Implemented confi snapshots

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -17,6 +17,8 @@ uopi runs as a **single portable binary** with no runtime dependencies. Point an
 | **Plot panels** | Dedicated chart panels with a recursive split layout (tmux/IDE-style) where plots fill the viewport |
 | **Panel logic** | In-editor node-graph flow editor (triggers → actions, dialogs) that runs client-side in view mode |
 | **Control logic** | Server-side always-on flow graphs with cron/alarm triggers and Lua blocks |
+| **Configuration manager** | Versioned configuration **sets** (typed signal schemas, grouped) and **instances** (values) with validation, array/CSV editing, apply-to-signals, and JSON import/export |
+| **Version history & diff** | Git-style history for panels, synthetic signals, control logic and config sets/instances: view, fork, promote any revision, with unified / side-by-side diff |
 | **Local variables** | Panel-scoped state variables for set-points, toggles and counters used by logic |
 | **Historical data** | EPICS Archive Appliance integration via REST; time range picker in UI |
 | **Synthetic signals** | Compose, filter, and transform signals via a wizard or visual node-graph editor (gain, offset, moving average, lowpass, highpass, derivative, integral, clamp, formula); panel/user/global visibility scopes |
@@ -138,12 +140,20 @@ The REST API is available under `/api/v1`. Key endpoints:
 | `POST` | `/api/v1/interfaces/{id}/clone` | Duplicate an interface |
 | `POST` | `/api/v1/interfaces/reorder` | Reorder panels / move them between folders |
 | `GET/PUT` | `/api/v1/interfaces/{id}/acl` | Read or set a panel's sharing rules |
-| `GET` | `/api/v1/interfaces/{id}/versions` | List saved versions of a panel |
 | `GET/POST` | `/api/v1/folders` | List or create panel folders |
 | `PUT/DELETE` | `/api/v1/folders/{id}` | Rename/reparent or delete a folder |
 | `GET/POST/DELETE` | `/api/v1/synthetic` | Manage synthetic signal definitions |
 | `GET/POST` | `/api/v1/controllogic` | List or create server-side control-logic graphs |
 | `GET/PUT/DELETE` | `/api/v1/controllogic/{id}` | Read, update, or delete a control-logic graph |
+| `GET/POST` | `/api/v1/config/sets` | List or create configuration sets (schemas) |
+| `GET/PUT/DELETE` | `/api/v1/config/sets/{id}` | Read, update, or delete a config set |
+| `GET/POST` | `/api/v1/config/instances` | List or create configuration instances (values) |
+| `GET/PUT/DELETE` | `/api/v1/config/instances/{id}` | Read, update, or delete a config instance |
+| `POST` | `/api/v1/config/instances/{id}/apply` | Write an instance's values to their target signals |
+| `GET` | `/api/v1/config/{sets\|instances}/diff` | Structural diff between two revisions |
+| `GET` | `/api/v1/{interfaces\|synthetic\|controllogic\|config/sets\|config/instances}/{id}/versions` | List revisions; `…/{version}` fetches one |
+| `POST` | `…/{id}/versions/{v}/promote` | Promote a revision to current |
+| `POST` | `…/{id}/versions/{v}/fork` | Fork a revision into a new document |
 | `GET` | `/api/v1/me` | Caller identity, access level, groups, logic-edit permission |
 | `GET` | `/api/v1/usergroups` | List configured users and groups (for sharing) |
 | `GET` | `/metrics` | Prometheus-format server metrics |

TODO.md

@@ -0,0 +1,87 @@
+# TODO
+
+- [ ] **MAJOR** Implement configuration manager:
+  - configuration is a set of signals (that can be organized in group and subgroup) that are used to configure a system or a sub system
+  - with configuration manager user should be able to:
+    - Define and manage configuration sets: delete (keep server side copy of deleted config), create (specifying default to parameters, mandatory, optional etc), edit (with versioning git style) and compare set
+      - user can fork an existing config instance to create a new one
+      - user can compare two instances: show unified diff or side by side diff
+      - etc...
+    - Create, delete (keep server cache), edit (git style versioning) and compare configuration instances: meaning set actual value to a configuration set
+      - user can fork an existing config instance to create a new one
+      - user can compare two instances: show unified diff or side by side diff
+      - etc...
+  - [x] user can apply and save configuration instances from manager
+  - [x] **instance snapshot**: create a new instance from the current live value of all of a set's target signals (optional label, else auto name) — exposed in the config editor (⎙ Snapshot), control loop (`action.config.snapshot`) and logic editor (`action.config.snapshot`)
+  - [x] **live diff**: compare a stored instance against current signal values ("Diff vs current" button → `/config/instances/{id}/livediff`)
+  - [x] git-style versioning for config sets and instances: fork any revision, click to view, promote to current, with unified / side-by-side diff (shared `VersionTree`)
+  - [x] in logic editor and control loop add nodes to read/write/create/apply config instances
+    - [x] **apply** and **read** config-instance nodes in both control logic (server Go) and panel logic (client TS)
+    - [x] **create / write** nodes (mutate versioned instances from automation) in both engines
+    - [x] **Config Selector** panel widget: operator picks an instance of a chosen set (optionally a subset) from a combo, writing its id to a panel-local string variable; apply/read/write panel-logic nodes can read their instance dynamically from that variable ("From variable" source)
+  - [x] support for all supported types (number, bools, enums, arrays, string etc)
+  - [x] ux elements for config set
+    - [x] the configuration editor should automatically get type and info from signal when possible (type is read-only, auto-derived from the bound signal)
+    - [x] a slick tree drag and drop editor to order elements and organize in group and sub-groups
+    - [x] possibility to customise unit, max, min etc
+    - [x] export / import a config set as JSON
+    - [x] full-screen config window
+  - [x] ux elements for config instances:
+    - automatically use the correct setting widget depending on the type (e.g. combo for enum, nubmer input for number):
+      - for arrays: import csv option, display points as mini plot (+ open dialog plot with more info), manual enter points via table like interface
+    - automatically fill with default or existing values (when forking an existing instance)
+    - explicity show errors/missing info and give additional info on hover
+  - [x] add advanced validation / transformation framework to configurations using custom CUE rules:
+    - [x] backend runs validation / transformation rules (real CUE via `cuelang.org/go`; `internal/confmgr/cue.go`). Rules are a third versioned `Kind` bound to a set; evaluated on instance create/update — violations block the save, concrete derivations transform & persist the values
+    - [x] user can create/edit/delete/compare rules from webui (Rules tab in ConfigManager; git-style versioning + side-by-side/unified source diff)
+      - [x] integrate syntax highlight (hand-rolled `CueEditor.tsx`, mirroring `LuaEditor`)
+      - [x] integrate autocomplete for signals names and cue grammars (param keys + target signals + CUE keywords/types; Ctrl+Space)
+      - [ ] ~~integrate cue lsp~~ — descoped: a separate language-server process does not fit the no-npm / single portable-binary architecture
+    - [x] when validation fails the error is propagated to the user (live `/config/rules/check` panel while editing; save returns the structured violation)
+    - [x] all actions tracked via history (versioned rules) + audit (`config.rule.create/update/delete/promote/fork`)
+- [ ] Improve UX:
+  - [ ] Synthetic editor:
+    - [ ] color code the node link by type
+      - [ ] edges color depends on type (e.g. float) including arrays
+      - [ ] input / outputs are color coded (if can accept many, gray, otherwise specific color, can be dynamic)
+      - [ ] can not connect input / output that are not compatible
+    - [x] hover on a block in error should show the reason
+    - [x] add proper array functionality
+    - [x] add shortcut to add Signals (S) and nodes (N) with HUD
+  - [ ] Panels:
+    - [x] in view mode the widgets should have no border/bg but blend with background
+    - [ ] add widgets such as toggle switch, table and other industrial hmi widgets
+    - [ ] add container widgets: labelled/title pane, tab panes, collapsable panes etc
+  - [ ] plot pane:
+    - [ ] add toolbar
+    - [ ] add time window selector to toolbar
+    - [ ] plot x-axis synchronised (option to unlink in toolbar)
+    - [ ] cursors and measuraments
+    - [ ] pause/resume
+    - [ ] save screenshot
+  - [ ] clean ui:
+    - create small statusbar where connection widget and other status related info will be placed
+    - group advanced items (audit/control loops/config manager etc) in a tool menu or something similar to not fill the toolbar
+    - make the toolbar as clean as possible
+- [ ] Logic editor:
+  - add full support to local array values: dynamic, dynamic but capped max, fixed size etc:
+    - array functions should work with new local array
+- [ ] Control loop:
+  - add full support to server side array values
+- [x] Implement git style versioning for: synthetic variable, panels, control logic:
+  - [x] possibility to fork any version
+  - [x] click to view the version
+  - [x] possibility to view graphical diff between versions (side by side or unified diff)
+  - [x] simple slick versioning pane:
+    - [x] vertical tree like
+    - [x] each version represented by a circle
+    - [x] active (the one currently view/edited) version has circle bigger then rest
+    - [x] selected (the one that will be executed/showed by user) version has circle full, not active only border
+    - [x] unsaved / new version appear with connection line dashed
+- [ ] Implement admin pane: create / manage groups, set users permits, manage auditors etc
+- [ ] Implement new datasources:
+  - [ ] Finalize alarm service
+  - [ ] modbus tcp
+  - [ ] scpi tcp
+  - [ ] udp? other?
+- [ ] **MAJOR** Implement proper distributed server side nodes to balance load and have redundancy (if a node is not available anymore all its clients migrate seamelessly to another)

cmd/uopi/main.go

@@ -9,14 +9,19 @@ import (
 	"log/slog"
 	"os"
 	"os/signal"
+	"os/user"
+	"path/filepath"
 	"syscall"
 
 	"github.com/uopi/uopi/internal/access"
+	"github.com/uopi/uopi/internal/audit"
 	"github.com/uopi/uopi/internal/broker"
 	"github.com/uopi/uopi/internal/config"
+	"github.com/uopi/uopi/internal/confmgr"
 	"github.com/uopi/uopi/internal/controllogic"
 	"github.com/uopi/uopi/internal/datasource/epics"
 	"github.com/uopi/uopi/internal/datasource/pva"
+	"github.com/uopi/uopi/internal/datasource/servervar"
 	"github.com/uopi/uopi/internal/datasource/stub"
 	"github.com/uopi/uopi/internal/datasource/synthetic"
 	"github.com/uopi/uopi/internal/panelacl"
@@ -41,6 +46,16 @@ func main() {
 		os.Exit(1)
 	}
 
+	// In an unproxied/local deployment (no trusted_user_header) without an explicit
+	// default_user, attribute actions to the OS user running the process so the UI
+	// and audit log show a real identity instead of anonymous.
+	if cfg.Server.TrustedUserHeader == "" && cfg.Server.DefaultUser == "" {
+		if u, err := user.Current(); err == nil && u.Username != "" {
+			cfg.Server.DefaultUser = u.Username
+			log.Info("no default_user configured; defaulting to OS user", "user", u.Username)
+		}
+	}
+
 	if err := os.MkdirAll(cfg.Server.StorageDir, 0o755); err != nil {
 		log.Error("failed to create storage dir", "dir", cfg.Server.StorageDir, "err", err)
 		os.Exit(1)
@@ -58,6 +73,12 @@ func main() {
 		os.Exit(1)
 	}
 
+	cfgStore, err := confmgr.New(cfg.Server.StorageDir)
+	if err != nil {
+		log.Error("failed to open configuration store", "err", err)
+		os.Exit(1)
+	}
+
 	webFS, err := fs.Sub(web.FS, "dist")
 	if err != nil {
 		log.Error("failed to sub web dist", "err", err)
@@ -122,6 +143,15 @@ func main() {
 		}
 	}
 
+	// Server variables: a small persistent key/value source ("srv") that the
+	// control-logic engine writes (e.g. sequence state) and panels can read.
+	srvVars, err := servervar.New(cfg.Server.StorageDir)
+	if err != nil {
+		log.Error("server variables init", "err", err)
+		os.Exit(1)
+	}
+	brk.Register(srvVars)
+
 	// Build the global access policy from config: every user is trusted with
 	// full write access unless downgraded by the blacklist; groups are named
 	// sets of users referenced by per-panel sharing.
@@ -133,7 +163,26 @@ func main() {
 	for _, g := range cfg.Groups {
 		groups[g.Name] = g.Members
 	}
-	policy := access.New(cfg.Server.DefaultUser, blacklist, groups, cfg.Server.LogicEditors)
+	policy := access.New(cfg.Server.DefaultUser, blacklist, groups, cfg.Server.LogicEditors, cfg.Audit.Readers)
+
+	// Audit log: when enabled, every system-affecting action (user/automated
+	// signal writes, interface and control-logic mutations) is recorded to SQLite.
+	// When disabled a no-op recorder is used so call sites need no guards.
+	recorder := audit.Nop()
+	if cfg.Audit.Enabled {
+		dbPath := cfg.Audit.DBPath
+		if dbPath == "" {
+			dbPath = filepath.Join(cfg.Server.StorageDir, "audit.db")
+		}
+		r, err := audit.NewSQLite(dbPath, log)
+		if err != nil {
+			log.Error("failed to open audit log", "path", dbPath, "err", err)
+			os.Exit(1)
+		}
+		defer r.Close()
+		recorder = r
+		log.Info("audit log enabled", "path", dbPath)
+	}
 
 	// Server-side control logic: flow graphs that run continuously under the root
 	// context, independent of any panel. The store is loaded from disk and the
@@ -143,10 +192,16 @@ func main() {
 		log.Error("failed to open control logic store", "err", err)
 		os.Exit(1)
 	}
-	ctrlEngine := controllogic.NewEngine(ctx, brk, ctrlStore, log)
+	ctrlEngine := controllogic.NewEngine(ctx, brk, ctrlStore, cfgStore, recorder, log)
+
+	// Dialog hub: control-logic action.dialog nodes push notifications/inputs to
+	// connected clients (filtered by user/group) and route input responses back
+	// to server variables. Installed before Reload so running graphs can emit.
+	dialogs := server.NewDialogHub(brk, policy, recorder, log)
+	ctrlEngine.SetNotifier(dialogs)
 	ctrlEngine.Reload()
 
-	srv := server.New(cfg.Server.Listen, webFS, brk, synthDS, store, policy, aclStore, ctrlStore, ctrlEngine, cfg.Datasource.EPICS.ChannelFinderURL, cfg.Datasource.EPICS.ArchiveURL, cfg.Server.TrustedUserHeader, log)
+	srv := server.New(cfg.Server.Listen, webFS, brk, synthDS, store, cfgStore, policy, aclStore, ctrlStore, ctrlEngine, dialogs, recorder, cfg.Datasource.EPICS.ChannelFinderURL, cfg.Datasource.EPICS.ArchiveURL, cfg.Server.TrustedUserHeader, log)
 
 	if err := srv.Start(ctx); err != nil {
 		fmt.Fprintf(os.Stderr, "server error: %v\n", err)

docs/FUNCTIONAL_SPEC.md

@@ -192,6 +192,7 @@ When multiple widgets are selected:
 | Histogram | numeric scalar(s) |
 | Bar chart | numeric scalar(s) |
 | Logic analyser | boolean / integer (bitset) |
+| Waveform | 1-D numeric array (latest sample, x-vs-index) |
 
 ### 4.5 Widget Properties (Properties Pane)
 
@@ -278,7 +279,7 @@ copy/paste.
 |----------|-------|
 | Triggers | Button press, threshold crossing, value change, timer/interval, panel loop, On-open / On-close lifecycle |
 | Logic | AND gate, If (then/else), Loop (count or while) |
-| Actions | Write to signal/variable, Delay, Log; Accumulate / Export-CSV / Clear for in-memory data arrays |
+| Actions | Write to signal/variable, Delay, Log; Accumulate / Export-CSV / Clear for in-memory data arrays; Apply config / Read config / Write config / Create config / Snapshot config (see §11) |
 | Dialogs | Info and Error pop-ups; Set-point prompt (asks the user for a number and writes it) |
 
 **System helpers in expressions:** `{sys:time}` (epoch seconds) and `{sys:dt}` (seconds
@@ -295,6 +296,12 @@ managed through the REST API.
 
 - Triggers include *cron* schedules and signal *alarm*/threshold conditions.
 - A **Lua** block provides custom logic; results are written back to signals.
+- **Apply / Read / Write / Create config** action nodes drive the configuration manager
+  (§11): *Apply config* writes every value of a chosen instance to its bound signals
+  (audited); *Read config* reads one parameter's value into a target signal or variable;
+  *Write config* stores a value into a parameter (creating a new instance revision); *Create
+  config* makes a new instance for a set, optionally seeded from another instance. Both
+  mutating nodes are audited.
 - Each graph can be enabled/disabled independently; saving reloads the engine live.
 - Editing is gated by the logic-edit restriction (§2).
 
@@ -304,7 +311,7 @@ managed through the REST API.
 
 - Interfaces are saved to the server in XML format and are available to all connected clients.
 - Per-panel access rules and panel-folder placement are stored server-side (sidecar JSON).
-- Saved versions are retained; a panel's version history can be listed, tagged and promoted.
+- Saved versions are retained; a panel's version history can be listed, tagged, viewed, promoted, forked and diffed — the same git-style versioning shared by all versioned documents (§12).
 - Export/Import allows local file exchange of XML files.
 - The XML schema records: interface kind (panel/plot) and split layout, widget type,
   position, size, signal bindings, all property values, local variables, and panel logic.
@@ -344,7 +351,93 @@ When the server has archive access configured:
 
 ---
 
-## 11. Non-functional Requirements
+## 11. Configuration Manager
+
+The **Configuration manager** (opened from the View-mode toolbar) manages three kinds of
+versioned documents, on **Sets**, **Instances** and **Rules** tabs, in a full-screen modal.
+
+**Configuration sets** are schemas: an ordered list of typed parameters, each binding a
+target signal. Parameters can be organised into **groups** and **subgroups** via a
+drag-and-drop tree.
+- A parameter's **type** (number, integer, boolean, string, enum, array/waveform) and its
+  unit/range/enum values are auto-derived from the bound signal's metadata when available;
+  the type is read-only.
+- Each parameter may declare a **default**, a **mandatory** flag, and **min/max** /
+  **enum** constraints.
+- Sets can be **exported / imported** as JSON.
+
+**Configuration instances** assign concrete values to a chosen set's parameters.
+- The editor renders the right control per type (number input, enum/boolean combo, and a
+  waveform editor with live sparkline, table editing, CSV import and a pop-out plot for
+  arrays); empty fields fall back to the parameter default.
+- Validation mirrors the backend (required-but-unset, out-of-range, wrong type, bad enum)
+  and is surfaced inline with hover detail.
+- **Apply** writes every value to its target signal and reports a per-parameter
+  applied / failed / skipped result.
+- **Snapshot** (⎙ in the Instances tab) captures the *current live value* of every target
+  signal of a chosen set into a new instance — an optional label, otherwise an auto name. This
+  records "what the hardware holds right now" as a reusable configuration.
+- **Diff vs current** compares a stored instance (resolved with defaults) against the current
+  live signal values, so an operator can see how the saved configuration differs from what the
+  system currently has.
+
+The Sets and Instances tabs support the shared version history (§12): view, fork and promote
+revisions, plus a **structural diff** between any two revisions (per-parameter added / removed
+/ changed / unchanged).
+
+**Validation / transformation rules** (Rules tab) attach **CUE** logic to a set. Each rule is
+CUE source describing constraints and/or derivations over the parameter values: a field like
+`voltage: >=0 & <=24` validates a value, while a concrete derivation like
+`power: voltage * current` computes one. When an instance of the bound set is saved, every
+rule runs — a failed constraint **blocks the save** and surfaces the violation, and derived
+values are written into the stored instance. The rule editor is a CUE-aware code editor with
+syntax highlighting and autocomplete (parameter keys, target signal names, and CUE
+keywords/types via Ctrl+Space); a live panel re-evaluates the rule against the set's default
+values on every keystroke, showing compile errors, violations, or the derived values. Rules
+are versioned like the other documents, with a side-by-side / unified source diff, and every
+create / edit / delete is audited. (A full CUE language server is intentionally out of scope:
+it does not fit the no-dependency, single portable-binary design.)
+
+**Automation:** both the panel-logic (§6) and control-logic (§7) editors expose **Apply
+config**, **Read config**, **Write config**, **Create config** and **Snapshot config** action
+nodes. *Apply config* applies a chosen instance exactly like the Apply button; *Read config*
+reads a single numeric parameter into a target signal or variable; *Write config* stores a
+value into a parameter, creating a new instance revision; *Create config* makes a new instance
+for a set, optionally seeded from another instance; *Snapshot config* captures every target
+signal's current live value of a set into a new instance (like the ⎙ Snapshot button). The
+mutating nodes are audited.
+
+**Config Selector widget:** a panel widget that lets an operator pick which configuration a
+flow operates on at run time. It lists the instances of a chosen set — all of them or a
+defined subset — in a combo and writes the selected instance id to a panel-local string
+variable. The panel-logic Apply / Read / Write nodes can take their instance "From variable"
+(reading that id) instead of a fixed instance, so the operator's choice drives the flow.
+Control-logic nodes use fixed instances only (their variables are numeric).
+
+---
+
+## 12. Version History & Diff
+
+All versioned documents — panels, synthetic signals, control-logic graphs, and
+configuration sets/instances — share one git-style version model and a common history
+pane:
+
+- A **vertical version tree** lists every revision (one node each); the **current**
+  (executed) revision is filled, the **viewed** revision is enlarged, and unsaved edits show
+  a dashed connector.
+- **View** loads any past revision read-only into the editor — viewing alone is not an edit
+  and does not mark the document dirty; saving from a viewed revision creates a new revision
+  on top (history is never destroyed).
+- **Fork** copies a revision into a brand-new document (version reset to 1).
+- **Promote** re-saves an older revision as a new current revision.
+- **Diff** compares two revisions, defaulting to *current-vs-selected*, shown either
+  **unified** or **side-by-side**. Panels, synthetic and control-logic use a generic line
+  diff of the serialized document; configuration sets/instances use a richer per-parameter
+  structural diff.
+
+---
+
+## 13. Non-functional Requirements
 
 | Requirement | Target |
 |-------------|--------|

docs/TECHNICAL_SPEC.md

@@ -41,7 +41,7 @@
 | ---------------- | --------------------------------------------------------------- |
 | `preact` 10      | Virtual DOM UI framework                                        |
 | `uPlot`          | Extremely fast time-series/line plot (canvas-based, < 40 kB)    |
-| `Apache ECharts` | FFT, waterfall, histogram, bar, logic analyser plots            |
+| `Apache ECharts` | FFT, waterfall, histogram, bar, logic analyser, waveform plots   |
 | `uplot.css`      | uPlot default stylesheet                                        |
 
 **Intentionally excluded:** React, Vue, Svelte, Konva, WebGPU, jQuery, npm at runtime.
@@ -198,10 +198,6 @@ Base path: `/api/v1`
 | POST            | `/interfaces/reorder`                 | Reorder panels / move between folders             |
 | GET, PUT, DELETE| `/interfaces/{id}`                    | Download, update, or delete an interface          |
 | POST            | `/interfaces/{id}/clone`              | Clone an interface                                 |
-| GET             | `/interfaces/{id}/versions`           | List saved versions; `…/{version}` to fetch one   |
-| PUT             | `/interfaces/{id}/versions/{v}/tag`   | Tag a version                                      |
-| POST            | `/interfaces/{id}/versions/{v}/promote` | Promote a version to current                     |
-| POST            | `/interfaces/{id}/versions/{v}/fork`  | Fork a version into a new panel                   |
 | GET, PUT        | `/interfaces/{id}/acl`                | Read or set a panel's sharing rules               |
 | GET, POST       | `/folders`                            | List or create panel folders                      |
 | PUT, DELETE     | `/folders/{id}`                       | Rename/reparent or delete a folder                |
@@ -211,10 +207,33 @@ Base path: `/api/v1`
 | GET, PUT, DELETE| `/synthetic/{name}`                   | Read, update, or delete a synthetic definition    |
 | GET, POST       | `/controllogic`                       | List or create server-side control-logic graphs   |
 | GET, PUT, DELETE| `/controllogic/{id}`                  | Read, update, or delete a control-logic graph     |
+| GET, POST       | `/config/sets`                        | List or create configuration sets (schemas)       |
+| GET, PUT, DELETE| `/config/sets/{id}`                   | Read, update, or delete a config set              |
+| GET, POST       | `/config/instances`                   | List or create configuration instances (values)   |
+| GET, PUT, DELETE| `/config/instances/{id}`              | Read, update, or delete a config instance         |
+| POST            | `/config/instances/{id}/apply`        | Write an instance's values to their target signals |
+| POST            | `/config/instances/{id}/validate`     | Run the set's CUE rules over the stored values; returns a structured `RuleResult` (no save) |
+| GET             | `/config/instances/{id}/livediff`     | Diff the stored instance (resolved with defaults) against the current live signal values |
+| POST            | `/config/sets/{id}/snapshot`          | Capture every target signal's current live value into a new instance (body: optional `{name}`) |
+| GET             | `/config/{sets\|instances}/diff`      | Structural diff between two revisions (`a,av,b,bv`)|
+| GET, POST       | `/config/rules`                       | List or create CUE validation/transformation rules |
+| GET, PUT, DELETE| `/config/rules/{id}`                  | Read, update, or delete a rule                     |
+| POST            | `/config/rules/check`                 | Compile an (unsaved) CUE source and evaluate it against sample values — powers the live editor |
 
-Mutating requests are gated by the access middleware (§8): global level for writes,
+**Versioning (shared).** Interfaces, synthetic signals, control-logic graphs and config
+sets/instances all expose the same revision endpoints under their `{base}`:
+
+| Method | Path | Description |
+| ------ | ---- | ----------- |
+| GET    | `{base}/{id}/versions`              | List revisions; `…/{version}` fetches one      |
+| POST   | `{base}/{id}/versions/{v}/promote`  | Promote a revision to current                  |
+| POST   | `{base}/{id}/versions/{v}/fork`     | Fork a revision into a new document            |
+| PUT    | `/interfaces/{id}/versions/{v}/tag` | Tag a panel version                            |
+
+Mutating requests are gated by the access middleware (§3.10): global level for writes,
 per-panel ACL for interface endpoints, and the logic-editor allowlist for control-logic
-endpoints and for any change to a panel's `<logic>` block.
+endpoints and for any change to a panel's `<logic>` block. Config-set/instance
+promote/fork are gated by the same write policy.
 
 ### 3.5 EPICS Data Source
 
@@ -234,15 +253,30 @@ endpoints and for any change to a panel's `<logic>` block.
 
 **Built-in node types:**
 
-| Node type    | Parameters                          | Description                                      |
+| Node type        | Parameters                  | In→Out         | Description                                     |
-| ------------ | ----------------------------------- | ------------------------------------------------ |
+| ---------------- | --------------------------- | -------------- | ----------------------------------------------- |
-| `source`     | `ds`, `name`                        | Reads a signal from any data source              |
+| `source`         | `ds`, `name`                | —              | Reads a signal from any data source             |
-| `gain`       | `factor`                            | Multiplies by a constant                         |
+| `gain`           | `gain`                      | elementwise    | Multiplies by a constant                        |
-| `offset`     | `value`                             | Adds a constant                                  |
+| `offset`         | `offset`                    | elementwise    | Adds a constant                                 |
-| `moving_avg` | `window` (samples)                  | Rolling mean                                     |
+| `add`/`subtract` | —                           | elementwise    | Sum of inputs / `a − b`                         |
-| `lowpass`    | `freq` (Hz), `order` (1–8)          | Cascaded IIR Butterworth-style low-pass filter   |
+| `multiply`/`divide` | —                        | elementwise    | Product of inputs / `a ÷ b`                     |
-| `formula`    | `expr`                              | Inline math expression (variables: `a`, `b`, …) |
+| `clamp`          | `min`, `max`                | elementwise    | Constrains to a range                           |
-| `lua`        | `script`                            | Arbitrary Lua 5.1 code with persistent state     |
+| `threshold`      | `threshold`, `high`, `low`  | elementwise    | Comparator output                               |
+| `moving_average` | `window` (samples)          | scalar-only    | Rolling mean                                    |
+| `rms`            | `window` (samples)          | scalar-only    | Rolling RMS                                     |
+| `derivative`     | —                           | scalar-only    | Time derivative (per-sample `dt`)               |
+| `integrate`      | —                           | scalar-only    | Trapezoidal integral                            |
+| `lowpass`        | `freq` (Hz), `order` (1–8)  | scalar-only    | Cascaded IIR Butterworth-style low-pass filter  |
+| `expr`           | `expr`, `vars`              | elementwise    | Inline math expression (named inputs)           |
+| `lua`            | `script`, `vars`            | scalar-only    | Arbitrary Lua 5.1 code with persistent state    |
+| `index`          | `i`                         | array→scalar   | Element `i` of a waveform (bounds-checked)      |
+| `slice`          | `start`, `end`              | array→array    | Sub-range of a waveform (clamped)               |
+| `sum`/`mean`     | —                           | array→scalar   | Σ / average of a waveform                       |
+| `min`/`max`      | —                           | array→scalar   | Reduction of a waveform                         |
+| `length`         | —                           | array→scalar   | Element count of a waveform                     |
+| `fft`            | —                           | array→array    | Magnitude spectrum (zero-padded to next pow-2)  |
+
+**Scalar vs waveform values:** A value flowing through the graph is a `dsp.Sample` — either a scalar `float64` or a `[]float64` waveform (the array-aware counterpart of EPICS `TypeFloat64Array`). *Elementwise* ops broadcast over arrays (scalar inputs act as constants; array inputs must share a length). *Reduction*/*producer* ops (`index`/`slice`/`sum`/…/`fft`) operate natively on waveforms. *Scalar-only* ops (stateful filters + `lua`) reject array inputs, since their per-evaluation state cannot be split across array lanes. `OpOutputType` (`internal/dsp/types.go`) propagates types statically at compile time to reject invalid wirings and to report the synthetic's metadata type; the editor mirrors these rules in `web/src/lib/synthTypes.ts` to colour wires by data type (scalar vs array) and flag type-incompatible links. Runtime `Sample` typing is authoritative.
 
 **Low-pass filter implementation:** Cascaded first-order IIR sections. Each stage computes `y = y_prev + α·(x − y_prev)` where `α = dt / (RC + dt)` and `RC = 1/(2π·fc)`. `dt` is computed per sample from source timestamps so the filter is correct for event-driven (non-uniform) data.
 
@@ -303,6 +337,27 @@ and writes results back to signals. Graphs are persisted by a store and managed
 `/api/v1/controllogic`; each mutation calls `Engine.Reload()` to apply changes live. Graphs
 can be individually enabled/disabled.
 
+The engine also holds a `*confmgr.Store` (injected via `NewEngine`) for five config action
+nodes: `action.config.apply` resolves an instance + its set and runs `confmgr.Apply` with a
+broker-backed, audited write closure; `action.config.read` resolves a single parameter value
+(`ConfigInstance.Resolve`), coerces it to float64 and writes it to the node's target;
+`action.config.write` evaluates an expression and stores the (type-coerced, via
+`coerceParamValue`) value into a parameter, creating a new instance revision;
+`action.config.create` creates a new instance for a set, optionally seeding its values from
+another instance; and `action.config.snapshot` reads every target signal's current live value
+(via the one-shot `Broker.ReadNow`, type-coerced by `confmgr.Snapshot`) and stores them as a
+new instance. All mutating nodes are audited. The panel-logic engine
+(`web/src/lib/logic.ts`) mirrors all five client-side via the REST endpoints
+(`/config/instances/{id}/apply`, GET/PUT `/config/instances/{id}`, POST `/config/instances`,
+POST `/config/sets/{id}/snapshot`).
+Panel-logic apply/read/write nodes additionally support an `instanceSource: 'var'` mode that
+reads the target instance id (a string) from a panel-local variable rather than a fixed id —
+fed by the **Config Selector** widget (`web/src/widgets/ConfigSelect.tsx`), which lists a
+set's instances in a combo and writes the chosen id to that variable. Control-logic nodes use
+fixed ids only (its variables are numeric, instance ids are strings). To let the selector
+filter instances by set without a GET per instance, `confmgr.Store.List` now returns each
+instance's `setId` in its `Meta`.
+
 ### 3.10 Access Control
 
 Identity and global policy live in `internal/access` (`Policy`, `Level`). The user identity
@@ -314,6 +369,46 @@ the optional `server.logic_editors` allowlist over control-logic endpoints and o
 change to a panel's `<logic>` block; it is surfaced to the frontend through `/api/v1/me`
 (`canEditLogic`) so the UI can hide logic-editing affordances.
 
+### 3.11 Configuration Manager
+
+The configuration manager is `internal/confmgr`: a two-tier model of **sets** (typed
+parameter schemas binding target signals) and **instances** (values for a chosen set).
+`model.go` defines `ConfigSet`/`Parameter`/`ConfigInstance`; `apply.go` validates an
+instance against its set (`checkValue`) and writes each value to its target signal,
+returning a per-parameter apply report; `diff.go` produces the structural per-parameter
+diff used by the `/config/{sets,instances}/diff` endpoints.
+
+`store.go` persists each object as `configs/{sets,instances,rules}/{id}.json`, with superseded
+revisions backed up as `{id}.vN.json` alongside — the same git-style scheme as panels and
+synthetic/control-logic, so `Versions`/`GetVersion`/`Promote`/`Fork` behave identically.
+`Delete` is non-destructive: the object and all its backups are moved to a timestamped
+`trash/configs/…` folder.
+
+**CUE rules (`cue.go`, `KindRule`).** A third versioned object type carries a CUE source
+(`cuelang.org/go`) bound to a set via `SetID`. `EvaluateRule` compiles the source, unifies it
+with the instance values (`ctx.Encode`), and validates with `cue.Concrete(true)`: regular
+fields whose key matches a parameter constrain its value (failures become `RuleViolation`s),
+while concrete derivations whose value differs from the input are reported (and persisted) as
+**transformations**; hidden fields `_x` and definitions `#X` are helpers, excluded from both.
+`CreateInstance`/`UpdateInstance` call `applyRules` after the structural `ValidateAgainst`:
+all rules bound to the set are run in order (`evaluateRules`), a violation aborts the save as
+a `*RuleError`, and successful transformations are merged back into the stored values (set
+parameters only). `ValidateInstanceRules` is the read-only counterpart behind
+`/config/instances/{id}/validate`; `EvaluateRule` is exposed directly via
+`/config/rules/check` for the live editor.
+
+### 3.12 Document Versioning
+
+Versioning is implemented per storage layer but follows one shared contract: the live
+revision lives in the primary file; each save backs up the previous revision as
+`{id}.v{N}.{ext}`; `VersionMeta{Version,Name,Tag,Current,SavedAt}` describes each. `Promote`
+re-saves an older revision on top (creating a new current revision, never destroying
+history); `Fork` writes the revision out under a fresh id with its version reset to 1. The
+frontend `web/src/VersionHistory.tsx` (`VersionTree` + `DiffViewer`) consumes these
+generically; line diffs are computed client-side in `web/src/lib/linediff.ts`, while
+config sets/instances use the backend structural diff instead. Config **rules** reuse the
+generic client-side `DiffViewer` (line diff over the source).
+
 ---
 
 ## 4. Frontend Architecture
@@ -353,7 +448,7 @@ The edit canvas is a free-form HTML div with absolutely positioned widget compon
 View mode renders widgets as absolutely positioned Preact components on a scrollable canvas div:
 
 - Each widget subscribes to its signal store(s) in a `useEffect` and re-renders only when values change.
-- uPlot (time series) and ECharts (histogram, bar, FFT, waterfall, logic analyser) manage their own canvas elements inside their widget component.
+- uPlot (time series) and ECharts (histogram, bar, FFT, waterfall, logic analyser, waveform) manage their own canvas elements inside their widget component. The `waveform` plot renders a waveform (array) signal's latest `[]float64` as an x-vs-index trace, replacing the trace on each update.
 - Plot widgets maintain a rolling ring buffer of 200,000 samples per signal for smooth long-window display.
 - Step-hold interpolation: when multiple signals at different update rates share a plot, the most recent value is carried forward to fill the shared time axis correctly.
 

go.mod

@@ -3,10 +3,23 @@ module github.com/uopi/uopi
 go 1.26.2
 
 require (
+	cuelang.org/go v0.16.1
 	github.com/BurntSushi/toml v1.6.0
 	github.com/coder/websocket v1.8.14
 	github.com/evanw/esbuild v0.28.0
 	github.com/yuin/gopher-lua v1.1.2
 )
 
-require golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 // indirect
+require (
+	github.com/dustin/go-humanize v1.0.1 // indirect
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/ncruces/go-strftime v0.1.9 // indirect
+	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
+	golang.org/x/exp v0.0.0-20250620022241-b7579e27df2b // indirect
+	golang.org/x/sys v0.42.0 // indirect
+	modernc.org/libc v1.66.10 // indirect
+	modernc.org/mathutil v1.7.1 // indirect
+	modernc.org/memory v1.11.0 // indirect
+	modernc.org/sqlite v1.42.2 // indirect
+)

go.sum

@@ -1,10 +1,37 @@
+cuelang.org/go v0.16.1 h1:iPN1lHZd2J0hjcr8hfq9PnIGk7VfPkKFfxH4de+m9sE=
+cuelang.org/go v0.16.1/go.mod h1:/aW3967FeWC5Hc1cDrN4Z4ICVApdMi83wO5L3uF/1hM=
 github.com/BurntSushi/toml v1.6.0 h1:dRaEfpa2VI55EwlIW72hMRHdWouJeRF7TPYhI+AUQjk=
 github.com/BurntSushi/toml v1.6.0/go.mod h1:ukJfTF/6rtPPRCnwkur4qwRxa8vTRFBF0uk2lLoLwho=
 github.com/coder/websocket v1.8.14 h1:9L0p0iKiNOibykf283eHkKUHHrpG7f65OE3BhhO7v9g=
 github.com/coder/websocket v1.8.14/go.mod h1:NX3SzP+inril6yawo5CQXx8+fk145lPDC6pumgx0mVg=
+github.com/dustin/go-humanize v1.0.1 h1:GzkhY7T5VNhEkwH0PVJgjz+fX1rhBrR7pRT3mDkpeCY=
+github.com/dustin/go-humanize v1.0.1/go.mod h1:Mu1zIs6XwVuF/gI1OepvI0qD18qycQx+mFykh5fBlto=
 github.com/evanw/esbuild v0.28.0 h1:V96ghtc5p5JnNUQIUsc5H3kr+AcFcMqOJll2ZmJW6Lo=
 github.com/evanw/esbuild v0.28.0/go.mod h1:D2vIQZqV/vIf/VRHtViaUtViZmG7o+kKmlBfVQuRi48=
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
+github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/ncruces/go-strftime v0.1.9 h1:bY0MQC28UADQmHmaF5dgpLmImcShSi2kHU9XLdhx/f4=
+github.com/ncruces/go-strftime v0.1.9/go.mod h1:Fwc5htZGVVkseilnfgOVb9mKy6w1naJmn9CehxcKcls=
+github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec h1:W09IVJc94icq4NjY3clb7Lk8O1qJ8BdBEF8z0ibU0rE=
+github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec/go.mod h1:qqbHyh8v60DhA7CoWK5oRCqLrMHRGoxYCSS9EjAz6Eo=
 github.com/yuin/gopher-lua v1.1.2 h1:yF/FjE3hD65tBbt0VXLE13HWS9h34fdzJmrWRXwobGA=
 github.com/yuin/gopher-lua v1.1.2/go.mod h1:7aRmXIWl37SqRf0koeyylBEzJ+aPt8A+mmkQ4f1ntR8=
+golang.org/x/exp v0.0.0-20250620022241-b7579e27df2b h1:M2rDM6z3Fhozi9O7NWsxAkg/yqS/lQJ6PmkyIV3YP+o=
+golang.org/x/exp v0.0.0-20250620022241-b7579e27df2b/go.mod h1:3//PLf8L/X+8b4vuAfHzxeRUl04Adcb341+IGKfnqS8=
 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 h1:0A+M6Uqn+Eje4kHMK80dtF3JCXC4ykBgQG4Fe06QRhQ=
 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.36.0 h1:KVRy2GtZBrk1cBYA7MKu5bEZFxQk4NIDV6RLVcC8o0k=
+golang.org/x/sys v0.36.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/sys v0.42.0 h1:omrd2nAlyT5ESRdCLYdm3+fMfNFE/+Rf4bDIQImRJeo=
+golang.org/x/sys v0.42.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
+modernc.org/libc v1.66.10 h1:yZkb3YeLx4oynyR+iUsXsybsX4Ubx7MQlSYEw4yj59A=
+modernc.org/libc v1.66.10/go.mod h1:8vGSEwvoUoltr4dlywvHqjtAqHBaw0j1jI7iFBTAr2I=
+modernc.org/mathutil v1.7.1 h1:GCZVGXdaN8gTqB1Mf/usp1Y/hSqgI2vAGGP4jZMCxOU=
+modernc.org/mathutil v1.7.1/go.mod h1:4p5IwJITfppl0G4sUEDtCr4DthTaT47/N3aT6MhfgJg=
+modernc.org/memory v1.11.0 h1:o4QC8aMQzmcwCK3t3Ux/ZHmwFPzE6hf2Y5LbkRs+hbI=
+modernc.org/memory v1.11.0/go.mod h1:/JP4VbVC+K5sU2wZi9bHoq2MAkCnrt2r98UGeSK7Mjw=
+modernc.org/sqlite v1.42.2 h1:7hkZUNJvJFN2PgfUdjni9Kbvd4ef4mNLOu0B9FGxM74=
+modernc.org/sqlite v1.42.2/go.mod h1:+VkC6v3pLOAE0A0uVucQEcbVW0I5nHCeDaBf+DpsQT8=

internal/access/access.go

@@ -61,18 +61,20 @@ type Policy struct {
 	userGroups   map[string][]string // user → groups they belong to
 	groupNames   []string            // all configured group names (sorted)
 	logicEditors map[string]bool     // users + group names allowed to edit logic
+	auditReaders map[string]bool     // users + group names allowed to view the audit log
 }
 
 // New builds a Policy. blacklist maps a username to a config level string;
 // groups maps a group name to its member usernames. logicEditors optionally
 // restricts who may edit panel/control logic (usernames or group names); empty
 // means no restriction.
-func New(defaultUser string, blacklist map[string]string, groups map[string][]string, logicEditors []string) *Policy {
+func New(defaultUser string, blacklist map[string]string, groups map[string][]string, logicEditors, auditReaders []string) *Policy {
 	p := &Policy{
 		defaultUser:  strings.TrimSpace(defaultUser),
 		blacklist:    make(map[string]Level),
 		userGroups:   make(map[string][]string),
 		logicEditors: make(map[string]bool),
+		auditReaders: make(map[string]bool),
 	}
 	for _, e := range logicEditors {
 		e = strings.TrimSpace(e)
@@ -80,6 +82,12 @@ func New(defaultUser string, blacklist map[string]string, groups map[string][]st
 			p.logicEditors[e] = true
 		}
 	}
+	for _, e := range auditReaders {
+		e = strings.TrimSpace(e)
+		if e != "" {
+			p.auditReaders[e] = true
+		}
+	}
 	for user, lvl := range blacklist {
 		u := strings.TrimSpace(user)
 		if u == "" {
@@ -165,6 +173,29 @@ func (p *Policy) CanEditLogic(user string) bool {
 	return false
 }
 
+// CanViewAudit reports whether a user may view the audit log. When no reader
+// allowlist is configured everyone with read access qualifies; otherwise the
+// user (or one of their groups) must be listed. Anonymous/trusted-LAN callers
+// (user=="") are always permitted.
+func (p *Policy) CanViewAudit(user string) bool {
+	user = strings.TrimSpace(user)
+	if user == "" {
+		return true
+	}
+	if len(p.auditReaders) == 0 {
+		return true
+	}
+	if p.auditReaders[user] {
+		return true
+	}
+	for _, g := range p.userGroups[user] {
+		if p.auditReaders[g] {
+			return true
+		}
+	}
+	return false
+}
+
 // GroupsOf returns a copy of the groups a user belongs to.
 func (p *Policy) GroupsOf(user string) []string {
 	src := p.userGroups[strings.TrimSpace(user)]

internal/access/access_test.go

@@ -6,7 +6,7 @@ func TestCanEditLogic(t *testing.T) {
 	groups := map[string][]string{"ops": {"carol"}}
 
 	// No allowlist configured: everyone with write access may edit logic.
-	open := New("", nil, groups, nil)
+	open := New("", nil, groups, nil, nil)
 	for _, u := range []string{"", "alice", "carol"} {
 		if !open.CanEditLogic(u) {
 			t.Errorf("unrestricted: CanEditLogic(%q) = false, want true", u)
@@ -17,7 +17,7 @@ func TestCanEditLogic(t *testing.T) {
 	}
 
 	// Allowlist by username and by group name.
-	p := New("", nil, groups, []string{"alice", "ops"})
+	p := New("", nil, groups, []string{"alice", "ops"}, nil)
 	if !p.LogicRestricted() {
 		t.Error("LogicRestricted() = false with allowlist set")
 	}

internal/api/api.go

@@ -6,15 +6,20 @@ import (
 	"encoding/hex"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"io"
 	"log/slog"
+	"net"
 	"net/http"
 	"net/url"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/uopi/uopi/internal/access"
+	"github.com/uopi/uopi/internal/audit"
 	"github.com/uopi/uopi/internal/broker"
+	"github.com/uopi/uopi/internal/confmgr"
 	"github.com/uopi/uopi/internal/controllogic"
 	"github.com/uopi/uopi/internal/datasource"
 	"github.com/uopi/uopi/internal/datasource/synthetic"
@@ -27,25 +32,33 @@ type Handler struct {
 	broker           *broker.Broker
 	synthetic        *synthetic.Synthetic // nil if not enabled
 	store            *storage.Store
+	cfg              *confmgr.Store
 	policy           *access.Policy
 	acl              *panelacl.Store
 	ctrlLogic        *controllogic.Store
 	ctrlEngine       *controllogic.Engine
+	audit            audit.Recorder // never nil; audit.Nop when disabled
 	channelFinderURL string         // empty if not configured
 	archiverURL      string         // empty if not configured
 	log              *slog.Logger
 }
 
 // New creates an API Handler. synth may be nil if the synthetic DS is disabled.
-func New(b *broker.Broker, synth *synthetic.Synthetic, store *storage.Store, policy *access.Policy, acl *panelacl.Store, ctrlLogic *controllogic.Store, ctrlEngine *controllogic.Engine, channelFinderURL, archiverURL string, log *slog.Logger) *Handler {
+// rec records system-affecting mutations; pass audit.Nop() to disable auditing.
+func New(b *broker.Broker, synth *synthetic.Synthetic, store *storage.Store, cfg *confmgr.Store, policy *access.Policy, acl *panelacl.Store, ctrlLogic *controllogic.Store, ctrlEngine *controllogic.Engine, rec audit.Recorder, channelFinderURL, archiverURL string, log *slog.Logger) *Handler {
+	if rec == nil {
+		rec = audit.Nop()
+	}
 	return &Handler{
 		broker:           b,
 		synthetic:        synth,
 		store:            store,
+		cfg:              cfg,
 		policy:           policy,
 		acl:              acl,
 		ctrlLogic:        ctrlLogic,
 		ctrlEngine:       ctrlEngine,
+		audit:            rec,
 		channelFinderURL: channelFinderURL,
 		archiverURL:      archiverURL,
 		log:              log,
@@ -56,6 +69,7 @@ func New(b *broker.Broker, synth *synthetic.Synthetic, store *storage.Store, pol
 // Requires Go 1.22+ for method+path routing.
 func (h *Handler) Register(mux *http.ServeMux, prefix string) {
 	mux.HandleFunc("GET "+prefix+"/me", h.getMe)
+	mux.HandleFunc("GET "+prefix+"/audit", h.getAudit)
 	mux.HandleFunc("GET "+prefix+"/datasources", h.listDataSources)
 	mux.HandleFunc("GET "+prefix+"/signals", h.listSignals)
 	mux.HandleFunc("GET "+prefix+"/signals/search", h.searchSignals)
@@ -92,6 +106,11 @@ func (h *Handler) Register(mux *http.ServeMux, prefix string) {
 	mux.HandleFunc("GET "+prefix+"/synthetic/{name}", h.getSynthetic)
 	mux.HandleFunc("PUT "+prefix+"/synthetic/{name}", h.updateSynthetic)
 	mux.HandleFunc("DELETE "+prefix+"/synthetic/{name}", h.deleteSynthetic)
+	// Synthetic signal git-style versioning (list / view / promote / fork).
+	mux.HandleFunc("GET "+prefix+"/synthetic/{name}/versions", h.listSyntheticVersions)
+	mux.HandleFunc("GET "+prefix+"/synthetic/{name}/versions/{version}", h.getSyntheticVersion)
+	mux.HandleFunc("POST "+prefix+"/synthetic/{name}/versions/{version}/promote", h.promoteSyntheticVersion)
+	mux.HandleFunc("POST "+prefix+"/synthetic/{name}/versions/{version}/fork", h.forkSyntheticVersion)
 	// Server-side control logic CRUD (mutations are write-gated by the access
 	// middleware; each mutation reloads the running engine).
 	mux.HandleFunc("GET "+prefix+"/controllogic", h.listControlLogic)
@@ -99,6 +118,51 @@ func (h *Handler) Register(mux *http.ServeMux, prefix string) {
 	mux.HandleFunc("GET "+prefix+"/controllogic/{id}", h.getControlLogic)
 	mux.HandleFunc("PUT "+prefix+"/controllogic/{id}", h.updateControlLogic)
 	mux.HandleFunc("DELETE "+prefix+"/controllogic/{id}", h.deleteControlLogic)
+	// Control-logic git-style versioning (list / view / promote / fork).
+	mux.HandleFunc("GET "+prefix+"/controllogic/{id}/versions", h.listControlLogicVersions)
+	mux.HandleFunc("GET "+prefix+"/controllogic/{id}/versions/{version}", h.getControlLogicVersion)
+	mux.HandleFunc("POST "+prefix+"/controllogic/{id}/versions/{version}/promote", h.promoteControlLogicVersion)
+	mux.HandleFunc("POST "+prefix+"/controllogic/{id}/versions/{version}/fork", h.forkControlLogicVersion)
+	// Configuration manager — config sets (schemas) and instances (values),
+	// both versioned git-style. Mutations are write-gated by the access
+	// middleware; "apply" writes each value to its target signal.
+	mux.HandleFunc("GET "+prefix+"/config/sets", h.listConfigSets)
+	mux.HandleFunc("POST "+prefix+"/config/sets", h.createConfigSet)
+	mux.HandleFunc("GET "+prefix+"/config/sets/{id}", h.getConfigSet)
+	mux.HandleFunc("PUT "+prefix+"/config/sets/{id}", h.updateConfigSet)
+	mux.HandleFunc("DELETE "+prefix+"/config/sets/{id}", h.deleteConfigSet)
+	mux.HandleFunc("GET "+prefix+"/config/sets/{id}/versions", h.listConfigSetVersions)
+	mux.HandleFunc("GET "+prefix+"/config/sets/{id}/versions/{version}", h.getConfigSetVersion)
+	mux.HandleFunc("POST "+prefix+"/config/sets/{id}/versions/{version}/promote", h.promoteConfigSet)
+	mux.HandleFunc("POST "+prefix+"/config/sets/{id}/versions/{version}/fork", h.forkConfigSet)
+	mux.HandleFunc("POST "+prefix+"/config/sets/{id}/snapshot", h.snapshotConfigSet)
+	mux.HandleFunc("GET "+prefix+"/config/sets/diff", h.diffConfigSets)
+	mux.HandleFunc("GET "+prefix+"/config/instances", h.listConfigInstances)
+	mux.HandleFunc("POST "+prefix+"/config/instances", h.createConfigInstance)
+	mux.HandleFunc("GET "+prefix+"/config/instances/{id}", h.getConfigInstance)
+	mux.HandleFunc("PUT "+prefix+"/config/instances/{id}", h.updateConfigInstance)
+	mux.HandleFunc("DELETE "+prefix+"/config/instances/{id}", h.deleteConfigInstance)
+	mux.HandleFunc("GET "+prefix+"/config/instances/{id}/versions", h.listConfigInstanceVersions)
+	mux.HandleFunc("GET "+prefix+"/config/instances/{id}/versions/{version}", h.getConfigInstanceVersion)
+	mux.HandleFunc("POST "+prefix+"/config/instances/{id}/versions/{version}/promote", h.promoteConfigInstance)
+	mux.HandleFunc("POST "+prefix+"/config/instances/{id}/versions/{version}/fork", h.forkConfigInstance)
+	mux.HandleFunc("POST "+prefix+"/config/instances/{id}/apply", h.applyConfigInstance)
+	mux.HandleFunc("POST "+prefix+"/config/instances/{id}/validate", h.validateConfigInstance)
+	mux.HandleFunc("GET "+prefix+"/config/instances/{id}/livediff", h.diffConfigInstanceLive)
+	mux.HandleFunc("GET "+prefix+"/config/instances/diff", h.diffConfigInstances)
+	// Config rules — CUE validation/transformation logic bound to a set, run
+	// when instances of that set are saved. Versioned git-style; "check"
+	// evaluates an unsaved source for the live editor.
+	mux.HandleFunc("GET "+prefix+"/config/rules", h.listConfigRules)
+	mux.HandleFunc("POST "+prefix+"/config/rules", h.createConfigRule)
+	mux.HandleFunc("POST "+prefix+"/config/rules/check", h.checkConfigRule)
+	mux.HandleFunc("GET "+prefix+"/config/rules/{id}", h.getConfigRule)
+	mux.HandleFunc("PUT "+prefix+"/config/rules/{id}", h.updateConfigRule)
+	mux.HandleFunc("DELETE "+prefix+"/config/rules/{id}", h.deleteConfigRule)
+	mux.HandleFunc("GET "+prefix+"/config/rules/{id}/versions", h.listConfigRuleVersions)
+	mux.HandleFunc("GET "+prefix+"/config/rules/{id}/versions/{version}", h.getConfigRuleVersion)
+	mux.HandleFunc("POST "+prefix+"/config/rules/{id}/versions/{version}/promote", h.promoteConfigRule)
+	mux.HandleFunc("POST "+prefix+"/config/rules/{id}/versions/{version}/fork", h.forkConfigRule)
 }
 
 // ── /me ─────────────────────────────────────────────────────────────────────
@@ -118,15 +182,93 @@ func (h *Handler) getMe(w http.ResponseWriter, r *http.Request) {
 		"level":        h.policy.Level(user).String(),
 		"groups":       groups,
 		"canEditLogic": h.policy.CanEditLogic(user),
+		"canViewAudit": h.policy.CanViewAudit(user),
 	})
 }
 
+// ── /audit ────────────────────────────────────────────────────────────────────
+
+// getAudit returns audit-log entries matching the query filters. Access is
+// restricted to users permitted by CanViewAudit (the audit-readers allowlist).
+// Filters: start, end (RFC3339), user, action, ds, signal, limit.
+func (h *Handler) getAudit(w http.ResponseWriter, r *http.Request) {
+	if !h.policy.CanViewAudit(caller(r)) {
+		jsonError(w, http.StatusForbidden, "you are not permitted to view the audit log")
+		return
+	}
+	q := r.URL.Query()
+	f := audit.Filter{
+		Actor:  q.Get("user"),
+		Action: q.Get("action"),
+		DS:     q.Get("ds"),
+		Signal: q.Get("signal"),
+	}
+	if v := q.Get("start"); v != "" {
+		t, err := time.Parse(time.RFC3339, v)
+		if err != nil {
+			jsonError(w, http.StatusBadRequest, "invalid start time (want RFC3339): "+v)
+			return
+		}
+		f.Start = t
+	}
+	if v := q.Get("end"); v != "" {
+		t, err := time.Parse(time.RFC3339, v)
+		if err != nil {
+			jsonError(w, http.StatusBadRequest, "invalid end time (want RFC3339): "+v)
+			return
+		}
+		f.End = t
+	}
+	if v := q.Get("limit"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil {
+			f.Limit = n
+		}
+	}
+	events, err := h.audit.Query(f)
+	if err != nil {
+		h.log.Error("audit query", "err", err)
+		jsonError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	jsonOK(w, events)
+}
+
 // ── access helpers ────────────────────────────────────────────────────────────
 
 // caller returns the resolved end-user identity for the request (set by the
 // access middleware).
 func caller(r *http.Request) string { return access.UserFrom(r.Context()) }
 
+// clientIP returns the best-effort client address for audit attribution,
+// preferring the proxy-set X-Forwarded-For / X-Real-IP headers.
+func clientIP(r *http.Request) string {
+	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
+		if i := strings.IndexByte(xff, ','); i >= 0 {
+			return strings.TrimSpace(xff[:i])
+		}
+		return strings.TrimSpace(xff)
+	}
+	if xr := r.Header.Get("X-Real-IP"); xr != "" {
+		return strings.TrimSpace(xr)
+	}
+	if host, _, err := net.SplitHostPort(r.RemoteAddr); err == nil {
+		return host
+	}
+	return r.RemoteAddr
+}
+
+// recordMutation appends a successful configuration change to the audit log.
+func (h *Handler) recordMutation(r *http.Request, action, detail string) {
+	h.audit.Record(audit.Event{
+		Actor:     caller(r),
+		ActorType: audit.ActorUser,
+		Action:    action,
+		Detail:    detail,
+		IP:        clientIP(r),
+		Outcome:   audit.OutcomeOK,
+	})
+}
+
 // capByGlobal lowers a per-panel/folder permission to what the user's global
 // access level allows: read-only users can never exceed read, no-access users
 // get nothing.
@@ -490,6 +632,7 @@ func (h *Handler) createInterface(w http.ResponseWriter, r *http.Request) {
 			h.log.Error("record panel ownership", "id", id, "err", err)
 		}
 	}
+	h.recordMutation(r, "interface.create", id)
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(http.StatusCreated)
 	_ = json.NewEncoder(w).Encode(map[string]string{"id": id})
@@ -580,6 +723,7 @@ func (h *Handler) updateInterface(w http.ResponseWriter, r *http.Request) {
 		}
 		return
 	}
+	h.recordMutation(r, "interface.update", id)
 	w.WriteHeader(http.StatusNoContent)
 }
 
@@ -721,6 +865,7 @@ func (h *Handler) deleteInterface(w http.ResponseWriter, r *http.Request) {
 	if err := h.acl.DeletePanel(id); err != nil {
 		h.log.Error("delete panel ACL", "id", id, "err", err)
 	}
+	h.recordMutation(r, "interface.delete", id)
 	w.WriteHeader(http.StatusNoContent)
 }
 
@@ -1076,6 +1221,80 @@ func (h *Handler) deleteSynthetic(w http.ResponseWriter, r *http.Request) {
 	w.WriteHeader(http.StatusNoContent)
 }
 
+func (h *Handler) listSyntheticVersions(w http.ResponseWriter, r *http.Request) {
+	if h.synthetic == nil {
+		jsonError(w, http.StatusServiceUnavailable, "synthetic data source not enabled")
+		return
+	}
+	name := r.PathValue("name")
+	versions, err := h.synthetic.Versions(name)
+	if err != nil {
+		jsonError(w, http.StatusNotFound, "synthetic signal not found: "+name)
+		return
+	}
+	jsonOK(w, versions)
+}
+
+func (h *Handler) getSyntheticVersion(w http.ResponseWriter, r *http.Request) {
+	if h.synthetic == nil {
+		jsonError(w, http.StatusServiceUnavailable, "synthetic data source not enabled")
+		return
+	}
+	name := r.PathValue("name")
+	version, err := strconv.Atoi(r.PathValue("version"))
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version: "+r.PathValue("version"))
+		return
+	}
+	def, err := h.synthetic.GetVersion(name, version)
+	if err != nil {
+		jsonError(w, http.StatusNotFound, "version not found")
+		return
+	}
+	jsonOK(w, def)
+}
+
+func (h *Handler) promoteSyntheticVersion(w http.ResponseWriter, r *http.Request) {
+	if h.synthetic == nil {
+		jsonError(w, http.StatusServiceUnavailable, "synthetic data source not enabled")
+		return
+	}
+	name := r.PathValue("name")
+	version, err := strconv.Atoi(r.PathValue("version"))
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version: "+r.PathValue("version"))
+		return
+	}
+	def, err := h.synthetic.PromoteVersion(name, version)
+	if err != nil {
+		jsonError(w, http.StatusNotFound, "version not found")
+		return
+	}
+	h.recordMutation(r, "synthetic.promote", fmt.Sprintf("%s v%d", name, version))
+	jsonOK(w, def)
+}
+
+func (h *Handler) forkSyntheticVersion(w http.ResponseWriter, r *http.Request) {
+	if h.synthetic == nil {
+		jsonError(w, http.StatusServiceUnavailable, "synthetic data source not enabled")
+		return
+	}
+	name := r.PathValue("name")
+	version, err := strconv.Atoi(r.PathValue("version"))
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version: "+r.PathValue("version"))
+		return
+	}
+	def, err := h.synthetic.ForkVersion(name, version)
+	if err != nil {
+		jsonError(w, http.StatusNotFound, "version not found")
+		return
+	}
+	h.recordMutation(r, "synthetic.fork", fmt.Sprintf("%s v%d -> %s", name, version, def.Name))
+	w.WriteHeader(http.StatusCreated)
+	jsonOK(w, map[string]string{"id": def.Name})
+}
+
 // ── Control logic ──────────────────────────────────────────────────────────────
 
 func (h *Handler) listControlLogic(w http.ResponseWriter, _ *http.Request) {
@@ -1123,6 +1342,7 @@ func (h *Handler) createControlLogic(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	h.ctrlEngine.Reload()
+	h.recordMutation(r, "controllogic.create", g.ID+" "+g.Name)
 	w.WriteHeader(http.StatusCreated)
 	jsonOK(w, g)
 }
@@ -1152,6 +1372,7 @@ func (h *Handler) updateControlLogic(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	h.ctrlEngine.Reload()
+	h.recordMutation(r, "controllogic.update", g.ID+" "+g.Name)
 	jsonOK(w, g)
 }
 
@@ -1164,14 +1385,98 @@ func (h *Handler) deleteControlLogic(w http.ResponseWriter, r *http.Request) {
 		jsonError(w, http.StatusForbidden, "you are not permitted to edit logic")
 		return
 	}
-	if err := h.ctrlLogic.Delete(r.PathValue("id")); err != nil {
+	id := r.PathValue("id")
-		jsonError(w, http.StatusNotFound, "control logic graph not found: "+r.PathValue("id"))
+	if err := h.ctrlLogic.Delete(id); err != nil {
+		jsonError(w, http.StatusNotFound, "control logic graph not found: "+id)
 		return
 	}
 	h.ctrlEngine.Reload()
+	h.recordMutation(r, "controllogic.delete", id)
 	w.WriteHeader(http.StatusNoContent)
 }
 
+func (h *Handler) listControlLogicVersions(w http.ResponseWriter, r *http.Request) {
+	if h.ctrlLogic == nil {
+		jsonError(w, http.StatusServiceUnavailable, "control logic not enabled")
+		return
+	}
+	versions, err := h.ctrlLogic.Versions(r.PathValue("id"))
+	if err != nil {
+		jsonError(w, http.StatusNotFound, "control logic graph not found: "+r.PathValue("id"))
+		return
+	}
+	jsonOK(w, versions)
+}
+
+func (h *Handler) getControlLogicVersion(w http.ResponseWriter, r *http.Request) {
+	if h.ctrlLogic == nil {
+		jsonError(w, http.StatusServiceUnavailable, "control logic not enabled")
+		return
+	}
+	version, err := strconv.Atoi(r.PathValue("version"))
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version: "+r.PathValue("version"))
+		return
+	}
+	g, err := h.ctrlLogic.GetVersion(r.PathValue("id"), version)
+	if err != nil {
+		jsonError(w, http.StatusNotFound, "version not found")
+		return
+	}
+	jsonOK(w, g)
+}
+
+func (h *Handler) promoteControlLogicVersion(w http.ResponseWriter, r *http.Request) {
+	if h.ctrlLogic == nil {
+		jsonError(w, http.StatusServiceUnavailable, "control logic not enabled")
+		return
+	}
+	if !h.policy.CanEditLogic(caller(r)) {
+		jsonError(w, http.StatusForbidden, "you are not permitted to edit logic")
+		return
+	}
+	id := r.PathValue("id")
+	version, err := strconv.Atoi(r.PathValue("version"))
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version: "+r.PathValue("version"))
+		return
+	}
+	g, err := h.ctrlLogic.Promote(id, version)
+	if err != nil {
+		jsonError(w, http.StatusNotFound, "version not found")
+		return
+	}
+	h.ctrlEngine.Reload()
+	h.recordMutation(r, "controllogic.promote", fmt.Sprintf("%s v%d", id, version))
+	jsonOK(w, g)
+}
+
+func (h *Handler) forkControlLogicVersion(w http.ResponseWriter, r *http.Request) {
+	if h.ctrlLogic == nil {
+		jsonError(w, http.StatusServiceUnavailable, "control logic not enabled")
+		return
+	}
+	if !h.policy.CanEditLogic(caller(r)) {
+		jsonError(w, http.StatusForbidden, "you are not permitted to edit logic")
+		return
+	}
+	id := r.PathValue("id")
+	version, err := strconv.Atoi(r.PathValue("version"))
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version: "+r.PathValue("version"))
+		return
+	}
+	g, err := h.ctrlLogic.Fork(id, version)
+	if err != nil {
+		jsonError(w, http.StatusNotFound, "version not found")
+		return
+	}
+	h.ctrlEngine.Reload()
+	h.recordMutation(r, "controllogic.fork", fmt.Sprintf("%s v%d -> %s", id, version, g.ID))
+	w.WriteHeader(http.StatusCreated)
+	jsonOK(w, map[string]string{"id": g.ID})
+}
+
 // ── Helpers ───────────────────────────────────────────────────────────────────
 
 // extractLogicBlock returns the verbatim <logic>…</logic> section of an

internal/api/api_test.go

@@ -14,7 +14,9 @@ import (
 
 	"github.com/uopi/uopi/internal/access"
 	"github.com/uopi/uopi/internal/api"
+	"github.com/uopi/uopi/internal/audit"
 	"github.com/uopi/uopi/internal/broker"
+	"github.com/uopi/uopi/internal/confmgr"
 	"github.com/uopi/uopi/internal/controllogic"
 	"github.com/uopi/uopi/internal/datasource/stub"
 	"github.com/uopi/uopi/internal/panelacl"
@@ -50,10 +52,16 @@ func setup(t *testing.T) (*httptest.Server, func()) {
 	if err != nil {
 		t.Fatal("controllogic.NewStore:", err)
 	}
-	clEngine := controllogic.NewEngine(ctx, brk, clStore, log)
+
+	cfgStore, err := confmgr.New(dir)
+	if err != nil {
+		t.Fatal("confmgr.New:", err)
+	}
+
+	clEngine := controllogic.NewEngine(ctx, brk, clStore, cfgStore, audit.Nop(), log)
 
 	mux := http.NewServeMux()
-	api.New(brk, nil, store, access.New("", nil, nil, nil), acl, clStore, clEngine, "", "", log).Register(mux, "/api/v1")
+	api.New(brk, nil, store, cfgStore, access.New("", nil, nil, nil, nil), acl, clStore, clEngine, audit.Nop(), "", "", log).Register(mux, "/api/v1")
 
 	srv := httptest.NewServer(mux)
 	return srv, func() {
@@ -214,7 +222,9 @@ func TestSearchSignals(t *testing.T) {
 	resp := get(t, srv, "/api/v1/signals/search?q=sine")
 	assertStatus(t, resp, http.StatusOK)
 
-	var signals []struct{ Name string `json:"name"` }
+	var signals []struct {
+		Name string `json:"name"`
+	}
 	readJSON(t, resp, &signals)
 
 	for _, s := range signals {
@@ -259,7 +269,9 @@ func TestInterfaceCRUD(t *testing.T) {
 	// Create
 	resp = postRaw(t, srv, "/api/v1/interfaces", "application/xml", []byte(sampleXML))
 	assertStatus(t, resp, http.StatusCreated)
-	var created struct{ ID string `json:"id"` }
+	var created struct {
+		ID string `json:"id"`
+	}
 	readJSON(t, resp, &created)
 	if created.ID == "" {
 		t.Fatal("expected non-empty ID from create")
@@ -303,7 +315,9 @@ func TestInterfaceCRUD(t *testing.T) {
 		t.Fatal("clone:", err)
 	}
 	assertStatus(t, resp, http.StatusCreated)
-	var cloned struct{ ID string `json:"id"` }
+	var cloned struct {
+		ID string `json:"id"`
+	}
 	readJSON(t, resp, &cloned)
 	if cloned.ID == created.ID {
 		t.Error("clone produced same ID as original")

internal/api/confmgr.go

@@ -0,0 +1,767 @@
+package api
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"strconv"
+	"sync"
+	"time"
+
+	"github.com/uopi/uopi/internal/broker"
+	"github.com/uopi/uopi/internal/confmgr"
+)
+
+// configEnabled guards every config-manager handler; the store is always
+// constructed today, but the nil check keeps the handlers safe if it is ever
+// made optional.
+func (h *Handler) configEnabled(w http.ResponseWriter) bool {
+	if h.cfg == nil {
+		jsonError(w, http.StatusServiceUnavailable, "configuration manager not enabled")
+		return false
+	}
+	return true
+}
+
+func pathVersion(r *http.Request) (int, error) {
+	return strconv.Atoi(r.PathValue("version"))
+}
+
+func configStatus(err error) int {
+	if errors.Is(err, confmgr.ErrNotFound) {
+		return http.StatusNotFound
+	}
+	return http.StatusBadRequest
+}
+
+// ── config sets ─────────────────────────────────────────────────────────────
+
+func (h *Handler) listConfigSets(w http.ResponseWriter, _ *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	sets, err := h.cfg.List(confmgr.KindSet)
+	if err != nil {
+		jsonError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	jsonOK(w, sets)
+}
+
+func (h *Handler) getConfigSet(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	set, err := h.cfg.GetSet(r.PathValue("id"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, set)
+}
+
+func (h *Handler) createConfigSet(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	var set confmgr.ConfigSet
+	if err := json.NewDecoder(r.Body).Decode(&set); err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
+		return
+	}
+	set.ID = ""
+	set.Owner = caller(r)
+	out, err := h.cfg.CreateSet(set, r.URL.Query().Get("tag"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.set.create", out.ID+" "+out.Name)
+	w.WriteHeader(http.StatusCreated)
+	jsonOK(w, out)
+}
+
+func (h *Handler) updateConfigSet(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	id := r.PathValue("id")
+	var set confmgr.ConfigSet
+	if err := json.NewDecoder(r.Body).Decode(&set); err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
+		return
+	}
+	out, err := h.cfg.UpdateSet(id, set, r.URL.Query().Get("tag"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.set.update", out.ID+" v"+strconv.Itoa(out.Version))
+	jsonOK(w, out)
+}
+
+func (h *Handler) deleteConfigSet(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	id := r.PathValue("id")
+	if err := h.cfg.Delete(confmgr.KindSet, id); err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.set.delete", id)
+	w.WriteHeader(http.StatusNoContent)
+}
+
+func (h *Handler) listConfigSetVersions(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	versions, err := h.cfg.Versions(confmgr.KindSet, r.PathValue("id"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, versions)
+}
+
+func (h *Handler) getConfigSetVersion(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	version, err := pathVersion(r)
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version")
+		return
+	}
+	set, err := h.cfg.GetSetVersion(r.PathValue("id"), version)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, set)
+}
+
+func (h *Handler) promoteConfigSet(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	version, err := pathVersion(r)
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version")
+		return
+	}
+	id := r.PathValue("id")
+	if err := h.cfg.Promote(confmgr.KindSet, id, version); err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.set.promote", id+" v"+strconv.Itoa(version))
+	set, err := h.cfg.GetSet(id)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, set)
+}
+
+func (h *Handler) forkConfigSet(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	version, err := pathVersion(r)
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version")
+		return
+	}
+	id := r.PathValue("id")
+	newID, err := h.cfg.Fork(confmgr.KindSet, id, version)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.set.fork", id+" v"+strconv.Itoa(version)+" -> "+newID)
+	set, err := h.cfg.GetSet(newID)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	w.WriteHeader(http.StatusCreated)
+	jsonOK(w, set)
+}
+
+// diffConfigSets compares two set revisions. Query params: a, b (ids);
+// optional av, bv (versions, default current).
+func (h *Handler) diffConfigSets(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	q := r.URL.Query()
+	left, err := h.resolveSet(q.Get("a"), q.Get("av"))
+	if err != nil {
+		jsonError(w, configStatus(err), "left set: "+err.Error())
+		return
+	}
+	right, err := h.resolveSet(q.Get("b"), q.Get("bv"))
+	if err != nil {
+		jsonError(w, configStatus(err), "right set: "+err.Error())
+		return
+	}
+	jsonOK(w, confmgr.DiffSets(left, right))
+}
+
+func (h *Handler) resolveSet(id, version string) (confmgr.ConfigSet, error) {
+	if id == "" {
+		return confmgr.ConfigSet{}, errors.New("missing set id")
+	}
+	if version == "" {
+		return h.cfg.GetSet(id)
+	}
+	v, err := strconv.Atoi(version)
+	if err != nil {
+		return confmgr.ConfigSet{}, errors.New("invalid version")
+	}
+	return h.cfg.GetSetVersion(id, v)
+}
+
+// ── config instances ────────────────────────────────────────────────────────
+
+func (h *Handler) listConfigInstances(w http.ResponseWriter, _ *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	insts, err := h.cfg.List(confmgr.KindInstance)
+	if err != nil {
+		jsonError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	jsonOK(w, insts)
+}
+
+func (h *Handler) getConfigInstance(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	inst, err := h.cfg.GetInstance(r.PathValue("id"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, inst)
+}
+
+func (h *Handler) createConfigInstance(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	var inst confmgr.ConfigInstance
+	if err := json.NewDecoder(r.Body).Decode(&inst); err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
+		return
+	}
+	inst.ID = ""
+	inst.Owner = caller(r)
+	out, err := h.cfg.CreateInstance(inst, r.URL.Query().Get("tag"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.instance.create", out.ID+" "+out.Name)
+	w.WriteHeader(http.StatusCreated)
+	jsonOK(w, out)
+}
+
+func (h *Handler) updateConfigInstance(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	id := r.PathValue("id")
+	var inst confmgr.ConfigInstance
+	if err := json.NewDecoder(r.Body).Decode(&inst); err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
+		return
+	}
+	out, err := h.cfg.UpdateInstance(id, inst, r.URL.Query().Get("tag"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.instance.update", out.ID+" v"+strconv.Itoa(out.Version))
+	jsonOK(w, out)
+}
+
+func (h *Handler) deleteConfigInstance(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	id := r.PathValue("id")
+	if err := h.cfg.Delete(confmgr.KindInstance, id); err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.instance.delete", id)
+	w.WriteHeader(http.StatusNoContent)
+}
+
+func (h *Handler) listConfigInstanceVersions(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	versions, err := h.cfg.Versions(confmgr.KindInstance, r.PathValue("id"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, versions)
+}
+
+func (h *Handler) getConfigInstanceVersion(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	version, err := pathVersion(r)
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version")
+		return
+	}
+	inst, err := h.cfg.GetInstanceVersion(r.PathValue("id"), version)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, inst)
+}
+
+func (h *Handler) promoteConfigInstance(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	version, err := pathVersion(r)
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version")
+		return
+	}
+	id := r.PathValue("id")
+	if err := h.cfg.Promote(confmgr.KindInstance, id, version); err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.instance.promote", id+" v"+strconv.Itoa(version))
+	inst, err := h.cfg.GetInstance(id)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, inst)
+}
+
+func (h *Handler) forkConfigInstance(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	version, err := pathVersion(r)
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version")
+		return
+	}
+	id := r.PathValue("id")
+	newID, err := h.cfg.Fork(confmgr.KindInstance, id, version)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.instance.fork", id+" v"+strconv.Itoa(version)+" -> "+newID)
+	inst, err := h.cfg.GetInstance(newID)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	w.WriteHeader(http.StatusCreated)
+	jsonOK(w, inst)
+}
+
+// applyConfigInstance writes every resolvable parameter value of an instance to
+// its target signal via the broker. Per-parameter outcomes are returned so a
+// partial apply is reported faithfully.
+func (h *Handler) applyConfigInstance(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	id := r.PathValue("id")
+	inst, err := h.cfg.GetInstance(id)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	set, err := h.cfg.SetForInstance(inst)
+	if err != nil {
+		jsonError(w, configStatus(err), "load set: "+err.Error())
+		return
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 15*time.Second)
+	defer cancel()
+	write := func(ds, signal string, value any) error {
+		src, ok := h.broker.Source(ds)
+		if !ok {
+			return errors.New("unknown data source: " + ds)
+		}
+		return src.Write(ctx, signal, value)
+	}
+	res := confmgr.Apply(set, inst, write)
+	h.recordMutation(r, "config.instance.apply", id+" applied="+strconv.Itoa(res.Applied)+" failed="+strconv.Itoa(res.Failed))
+	jsonOK(w, res)
+}
+
+// diffConfigInstances compares two instance revisions. Query params: a, b
+// (ids); optional av, bv (versions, default current).
+func (h *Handler) diffConfigInstances(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	q := r.URL.Query()
+	left, err := h.resolveInstance(q.Get("a"), q.Get("av"))
+	if err != nil {
+		jsonError(w, configStatus(err), "left instance: "+err.Error())
+		return
+	}
+	right, err := h.resolveInstance(q.Get("b"), q.Get("bv"))
+	if err != nil {
+		jsonError(w, configStatus(err), "right instance: "+err.Error())
+		return
+	}
+	jsonOK(w, confmgr.DiffInstances(left, right))
+}
+
+func (h *Handler) resolveInstance(id, version string) (confmgr.ConfigInstance, error) {
+	if id == "" {
+		return confmgr.ConfigInstance{}, errors.New("missing instance id")
+	}
+	if version == "" {
+		return h.cfg.GetInstance(id)
+	}
+	v, err := strconv.Atoi(version)
+	if err != nil {
+		return confmgr.ConfigInstance{}, errors.New("invalid version")
+	}
+	return h.cfg.GetInstanceVersion(id, v)
+}
+
+// validateConfigInstance evaluates the CUE rules bound to an instance's set
+// against its stored values, without persisting anything. The structured
+// RuleResult (violations + any transformed values) lets the UI surface
+// per-parameter failures.
+func (h *Handler) validateConfigInstance(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	inst, err := h.cfg.GetInstance(r.PathValue("id"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	res, err := h.cfg.ValidateInstanceRules(inst)
+	if err != nil {
+		jsonError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	jsonOK(w, res)
+}
+
+// ── config snapshot / live diff ─────────────────────────────────────────────
+
+// readResult is the per-signal outcome of a parallel live read.
+type readResult struct {
+	val any
+	err error
+}
+
+// readSetSignals reads the current value of every distinct target signal of a
+// set in parallel (deduplicated by ds+signal), bounded by ctx. The returned map
+// is keyed by {ds, signal}.
+func (h *Handler) readSetSignals(ctx context.Context, set confmgr.ConfigSet) map[[2]string]readResult {
+	jobs := make(map[[2]string]struct{}, len(set.Parameters))
+	for _, p := range set.Parameters {
+		jobs[[2]string{p.DS, p.Signal}] = struct{}{}
+	}
+	results := make(map[[2]string]readResult, len(jobs))
+	var mu sync.Mutex
+	var wg sync.WaitGroup
+	for k := range jobs {
+		wg.Add(1)
+		go func(ds, signal string) {
+			defer wg.Done()
+			v, err := h.broker.ReadNow(ctx, broker.SignalRef{DS: ds, Name: signal})
+			mu.Lock()
+			results[[2]string{ds, signal}] = readResult{val: v.Data, err: err}
+			mu.Unlock()
+		}(k[0], k[1])
+	}
+	wg.Wait()
+	return results
+}
+
+// snapshotReader builds a confmgr.ReadFunc backed by a pre-read results map.
+func snapshotReader(results map[[2]string]readResult) confmgr.ReadFunc {
+	return func(ds, signal string) (any, error) {
+		r, ok := results[[2]string{ds, signal}]
+		if !ok {
+			return nil, errors.New("signal not read")
+		}
+		return r.val, r.err
+	}
+}
+
+// snapshotConfigSet captures the current value of every target signal of a set
+// and stores them as a new config instance. Body: optional {name}. Returns the
+// created instance plus the per-parameter capture result.
+func (h *Handler) snapshotConfigSet(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	set, err := h.cfg.GetSet(r.PathValue("id"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	var body struct {
+		Name string `json:"name"`
+	}
+	if r.Body != nil {
+		_ = json.NewDecoder(r.Body).Decode(&body) // body is optional
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
+	defer cancel()
+	results := h.readSetSignals(ctx, set)
+	snap := confmgr.Snapshot(set, snapshotReader(results))
+
+	name := body.Name
+	if name == "" {
+		name = set.Name + " snapshot " + time.Now().Format("2006-01-02 15:04:05")
+	}
+	inst := confmgr.ConfigInstance{
+		Name:   name,
+		SetID:  set.ID,
+		Owner:  caller(r),
+		Values: snap.Values,
+	}
+	out, err := h.cfg.CreateInstance(inst, r.URL.Query().Get("tag"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.instance.snapshot", out.ID+" "+out.Name+" captured="+strconv.Itoa(snap.Captured)+" failed="+strconv.Itoa(snap.Failed))
+	w.WriteHeader(http.StatusCreated)
+	jsonOK(w, struct {
+		Instance confmgr.ConfigInstance `json:"instance"`
+		Snapshot confmgr.SnapshotResult `json:"snapshot"`
+	}{out, snap})
+}
+
+// diffConfigInstanceLive compares a stored instance against the current live
+// values of its set's target signals, so an operator can see how the saved
+// config differs from what the hardware currently holds. The stored side uses
+// resolved values (instance value or parameter default) so default-backed
+// parameters are not reported as spurious additions.
+func (h *Handler) diffConfigInstanceLive(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	inst, err := h.cfg.GetInstance(r.PathValue("id"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	set, err := h.cfg.SetForInstance(inst)
+	if err != nil {
+		jsonError(w, configStatus(err), "load set: "+err.Error())
+		return
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
+	defer cancel()
+	results := h.readSetSignals(ctx, set)
+	snap := confmgr.Snapshot(set, snapshotReader(results))
+
+	left := confmgr.ConfigInstance{ID: inst.ID, Name: inst.Name, Values: map[string]any{}}
+	for _, p := range set.Parameters {
+		if v, ok := inst.Resolve(p); ok {
+			left.Values[p.Key] = v
+		}
+	}
+	current := confmgr.ConfigInstance{Name: "current", Values: snap.Values}
+	jsonOK(w, confmgr.DiffInstances(left, current))
+}
+
+// ── config rules (CUE validation/transformation) ────────────────────────────
+
+func (h *Handler) listConfigRules(w http.ResponseWriter, _ *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	rules, err := h.cfg.List(confmgr.KindRule)
+	if err != nil {
+		jsonError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	jsonOK(w, rules)
+}
+
+func (h *Handler) getConfigRule(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	rule, err := h.cfg.GetRule(r.PathValue("id"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, rule)
+}
+
+func (h *Handler) createConfigRule(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	var rule confmgr.ConfigRule
+	if err := json.NewDecoder(r.Body).Decode(&rule); err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
+		return
+	}
+	rule.ID = ""
+	rule.Owner = caller(r)
+	out, err := h.cfg.CreateRule(rule, r.URL.Query().Get("tag"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.rule.create", out.ID+" "+out.Name)
+	w.WriteHeader(http.StatusCreated)
+	jsonOK(w, out)
+}
+
+func (h *Handler) updateConfigRule(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	id := r.PathValue("id")
+	var rule confmgr.ConfigRule
+	if err := json.NewDecoder(r.Body).Decode(&rule); err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
+		return
+	}
+	out, err := h.cfg.UpdateRule(id, rule, r.URL.Query().Get("tag"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.rule.update", out.ID+" v"+strconv.Itoa(out.Version))
+	jsonOK(w, out)
+}
+
+func (h *Handler) deleteConfigRule(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	id := r.PathValue("id")
+	if err := h.cfg.Delete(confmgr.KindRule, id); err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.rule.delete", id)
+	w.WriteHeader(http.StatusNoContent)
+}
+
+func (h *Handler) listConfigRuleVersions(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	versions, err := h.cfg.Versions(confmgr.KindRule, r.PathValue("id"))
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, versions)
+}
+
+func (h *Handler) getConfigRuleVersion(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	version, err := pathVersion(r)
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version")
+		return
+	}
+	rule, err := h.cfg.GetRuleVersion(r.PathValue("id"), version)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, rule)
+}
+
+func (h *Handler) promoteConfigRule(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	version, err := pathVersion(r)
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version")
+		return
+	}
+	id := r.PathValue("id")
+	if err := h.cfg.Promote(confmgr.KindRule, id, version); err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.rule.promote", id+" v"+strconv.Itoa(version))
+	rule, err := h.cfg.GetRule(id)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	jsonOK(w, rule)
+}
+
+func (h *Handler) forkConfigRule(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	version, err := pathVersion(r)
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid version")
+		return
+	}
+	id := r.PathValue("id")
+	newID, err := h.cfg.Fork(confmgr.KindRule, id, version)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	h.recordMutation(r, "config.rule.fork", id+" v"+strconv.Itoa(version)+" -> "+newID)
+	rule, err := h.cfg.GetRule(newID)
+	if err != nil {
+		jsonError(w, configStatus(err), err.Error())
+		return
+	}
+	w.WriteHeader(http.StatusCreated)
+	jsonOK(w, rule)
+}
+
+// checkConfigRule compiles a (possibly unsaved) CUE source and, when sample
+// values are supplied, evaluates it against them. It powers the editor's live
+// validation panel; nothing is persisted.
+func (h *Handler) checkConfigRule(w http.ResponseWriter, r *http.Request) {
+	if !h.configEnabled(w) {
+		return
+	}
+	var body struct {
+		Source string         `json:"source"`
+		Values map[string]any `json:"values"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
+		return
+	}
+	jsonOK(w, confmgr.EvaluateRule(body.Source, body.Values))
+}

internal/api/confmgr_test.go

@@ -0,0 +1,107 @@
+package api_test
+
+import (
+	"net/http"
+	"testing"
+)
+
+// TestConfigSetCRUD exercises create → get → version → apply over HTTP, using
+// the stub data source's writable "setpoint" signal as the apply target.
+func TestConfigManagerEndToEnd(t *testing.T) {
+	srv, teardown := setup(t)
+	defer teardown()
+
+	// Create a config set targeting the stub's writable setpoint.
+	setBody := map[string]any{
+		"name": "Stub PSU",
+		"parameters": []map[string]any{
+			{"key": "sp", "ds": "stub", "signal": "setpoint", "type": "float64", "default": 42.0, "mandatory": true, "min": 0.0, "max": 100.0},
+		},
+	}
+	resp := postJSON(t, srv, "/api/v1/config/sets", setBody)
+	assertStatus(t, resp, http.StatusCreated)
+	var set struct {
+		ID      string `json:"id"`
+		Version int    `json:"version"`
+	}
+	readJSON(t, resp, &set)
+	if set.ID == "" || set.Version != 1 {
+		t.Fatalf("unexpected created set: %+v", set)
+	}
+
+	// List sets includes it.
+	resp = get(t, srv, "/api/v1/config/sets")
+	assertStatus(t, resp, http.StatusOK)
+	var sets []map[string]any
+	readJSON(t, resp, &sets)
+	if len(sets) != 1 {
+		t.Fatalf("want 1 set, got %d", len(sets))
+	}
+
+	// Create an instance assigning a concrete value.
+	instBody := map[string]any{
+		"name":   "nominal",
+		"setId":  set.ID,
+		"values": map[string]any{"sp": 73.0},
+	}
+	resp = postJSON(t, srv, "/api/v1/config/instances", instBody)
+	assertStatus(t, resp, http.StatusCreated)
+	var inst struct {
+		ID string `json:"id"`
+	}
+	readJSON(t, resp, &inst)
+	if inst.ID == "" {
+		t.Fatal("instance missing id")
+	}
+
+	// Apply writes the value to the target signal.
+	resp = postJSON(t, srv, "/api/v1/config/instances/"+inst.ID+"/apply", nil)
+	assertStatus(t, resp, http.StatusOK)
+	var res struct {
+		Applied int `json:"applied"`
+		Failed  int `json:"failed"`
+		Entries []struct {
+			Signal string `json:"signal"`
+			OK     bool   `json:"ok"`
+		} `json:"entries"`
+	}
+	readJSON(t, resp, &res)
+	if res.Applied != 1 || res.Failed != 0 {
+		t.Fatalf("apply summary: applied=%d failed=%d", res.Applied, res.Failed)
+	}
+	if len(res.Entries) != 1 || res.Entries[0].Signal != "setpoint" || !res.Entries[0].OK {
+		t.Errorf("unexpected apply entries: %+v", res.Entries)
+	}
+
+	// Delete the set soft-deletes it.
+	resp = deleteReq(t, srv, "/api/v1/config/sets/"+set.ID)
+	assertStatus(t, resp, http.StatusNoContent)
+	resp = get(t, srv, "/api/v1/config/sets/"+set.ID)
+	assertStatus(t, resp, http.StatusNotFound)
+}
+
+// TestConfigInstanceRejectsInvalidValue verifies server-side validation against
+// the bound set (value above the parameter's max).
+func TestConfigInstanceRejectsInvalidValue(t *testing.T) {
+	srv, teardown := setup(t)
+	defer teardown()
+
+	resp := postJSON(t, srv, "/api/v1/config/sets", map[string]any{
+		"name": "S",
+		"parameters": []map[string]any{
+			{"key": "sp", "ds": "stub", "signal": "setpoint", "type": "float64", "max": 10.0},
+		},
+	})
+	assertStatus(t, resp, http.StatusCreated)
+	var set struct {
+		ID string `json:"id"`
+	}
+	readJSON(t, resp, &set)
+
+	resp = postJSON(t, srv, "/api/v1/config/instances", map[string]any{
+		"name":   "bad",
+		"setId":  set.ID,
+		"values": map[string]any{"sp": 999.0},
+	})
+	assertStatus(t, resp, http.StatusBadRequest)
+}

internal/audit/audit.go

@@ -0,0 +1,65 @@
+// Package audit records system-affecting actions (signal writes by users or the
+// control-logic engine, interface and control-logic mutations) to an append-only
+// SQLite log that audit staff can query later. It is enabled via [audit] in the
+// config; when disabled a no-op Recorder is used so call sites need no guards.
+package audit
+
+import "time"
+
+// Actor types distinguish human-initiated actions from automated ones.
+const (
+	ActorUser   = "user"   // action attributed to an authenticated end-user
+	ActorSystem = "system" // action performed by the control-logic engine
+)
+
+// Outcomes record whether the action succeeded.
+const (
+	OutcomeOK    = "ok"
+	OutcomeError = "error"
+)
+
+// Event is a single audit record. Optional fields are omitted from the database
+// when empty. Time defaults to the current time when zero.
+type Event struct {
+	Time      time.Time `json:"time"`
+	Actor     string    `json:"actor"`            // username, or graph name for system actions
+	ActorType string    `json:"actorType"`        // ActorUser | ActorSystem
+	Action    string    `json:"action"`           // e.g. "signal.write", "interface.update"
+	DS        string    `json:"ds,omitempty"`     // data source (signal writes)
+	Signal    string    `json:"signal,omitempty"` // signal / target name
+	Value     string    `json:"value,omitempty"`  // serialised written value
+	Detail    string    `json:"detail,omitempty"` // free-form context (id, graph, trigger)
+	IP        string    `json:"ip,omitempty"`     // client address (user actions)
+	Outcome   string    `json:"outcome"`          // OutcomeOK | OutcomeError
+	Error     string    `json:"error,omitempty"`  // message when Outcome==OutcomeError
+}
+
+// Filter selects a subset of events for Query. Zero-valued fields are ignored.
+type Filter struct {
+	Start  time.Time
+	End    time.Time
+	Actor  string
+	Action string
+	DS     string
+	Signal string
+	Limit  int // <=0 means a default cap is applied
+}
+
+// Recorder appends events and answers queries. Implementations must be safe for
+// concurrent use and Record must never block the caller for long.
+type Recorder interface {
+	Record(Event)
+	Query(Filter) ([]Event, error)
+	Close() error
+}
+
+// nopRecorder is used when auditing is disabled. It discards every event.
+type nopRecorder struct{}
+
+func (nopRecorder) Record(Event)                  {}
+func (nopRecorder) Query(Filter) ([]Event, error) { return []Event{}, nil }
+func (nopRecorder) Close() error                  { return nil }
+
+// Nop returns a Recorder that discards everything. Call sites can hold a Recorder
+// unconditionally and call Record without checking whether auditing is enabled.
+func Nop() Recorder { return nopRecorder{} }

internal/audit/sqlite.go

@@ -0,0 +1,183 @@
+package audit
+
+import (
+	"database/sql"
+	"fmt"
+	"log/slog"
+	"strings"
+	"sync"
+	"time"
+
+	_ "modernc.org/sqlite" // pure-Go SQLite driver (no CGo, keeps the single static binary)
+)
+
+// defaultQueryLimit caps how many rows Query returns when the filter does not
+// specify a smaller limit, protecting the API and UI from unbounded result sets.
+const defaultQueryLimit = 1000
+
+// writeBuffer is the depth of the async insert queue. When full, Record falls
+// back to a synchronous insert so events are never silently dropped.
+const writeBuffer = 4096
+
+// sqliteRecorder appends events to a SQLite database. Inserts are normally
+// handled by a background goroutine so Record does not block the calling write
+// path; the queue has a synchronous fallback to guarantee durability under load.
+type sqliteRecorder struct {
+	db  *sql.DB
+	log *slog.Logger
+
+	ch     chan Event
+	wg     sync.WaitGroup
+	closed chan struct{}
+	once   sync.Once
+}
+
+// NewSQLite opens (creating if needed) the audit database at path and starts the
+// background writer. The returned Recorder must be Closed on shutdown.
+func NewSQLite(path string, log *slog.Logger) (Recorder, error) {
+	// WAL + a busy timeout let the async writer and synchronous query/fallback
+	// paths share the file without "database is locked" errors.
+	dsn := fmt.Sprintf("file:%s?_pragma=busy_timeout(5000)&_pragma=journal_mode(WAL)&_pragma=synchronous(NORMAL)", path)
+	db, err := sql.Open("sqlite", dsn)
+	if err != nil {
+		return nil, fmt.Errorf("open audit db: %w", err)
+	}
+	if _, err := db.Exec(schema); err != nil {
+		_ = db.Close()
+		return nil, fmt.Errorf("init audit schema: %w", err)
+	}
+	r := &sqliteRecorder{
+		db:     db,
+		log:    log,
+		ch:     make(chan Event, writeBuffer),
+		closed: make(chan struct{}),
+	}
+	r.wg.Add(1)
+	go r.writeLoop()
+	return r, nil
+}
+
+const schema = `
+CREATE TABLE IF NOT EXISTS audit_log (
+	id         INTEGER PRIMARY KEY AUTOINCREMENT,
+	ts_ns      INTEGER NOT NULL,
+	actor      TEXT NOT NULL,
+	actor_type TEXT NOT NULL,
+	action     TEXT NOT NULL,
+	ds         TEXT NOT NULL DEFAULT '',
+	signal     TEXT NOT NULL DEFAULT '',
+	value      TEXT NOT NULL DEFAULT '',
+	detail     TEXT NOT NULL DEFAULT '',
+	ip         TEXT NOT NULL DEFAULT '',
+	outcome    TEXT NOT NULL DEFAULT 'ok',
+	error      TEXT NOT NULL DEFAULT ''
+);
+CREATE INDEX IF NOT EXISTS idx_audit_ts ON audit_log(ts_ns);
+CREATE INDEX IF NOT EXISTS idx_audit_actor ON audit_log(actor);
+CREATE INDEX IF NOT EXISTS idx_audit_action ON audit_log(action);
+`
+
+func (r *sqliteRecorder) Record(e Event) {
+	if e.Time.IsZero() {
+		e.Time = time.Now()
+	}
+	if e.Outcome == "" {
+		e.Outcome = OutcomeOK
+	}
+	select {
+	case <-r.closed:
+		// Recorder is shutting down; best-effort synchronous insert.
+		r.insert(e)
+	case r.ch <- e:
+	default:
+		// Queue full: write synchronously rather than drop an audit record.
+		r.insert(e)
+	}
+}
+
+func (r *sqliteRecorder) writeLoop() {
+	defer r.wg.Done()
+	for e := range r.ch {
+		r.insert(e)
+	}
+}
+
+func (r *sqliteRecorder) insert(e Event) {
+	_, err := r.db.Exec(
+		`INSERT INTO audit_log (ts_ns, actor, actor_type, action, ds, signal, value, detail, ip, outcome, error)
+		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+		e.Time.UnixNano(), e.Actor, e.ActorType, e.Action,
+		e.DS, e.Signal, e.Value, e.Detail, e.IP, e.Outcome, e.Error,
+	)
+	if err != nil {
+		r.log.Error("audit: insert failed", "action", e.Action, "err", err)
+	}
+}
+
+func (r *sqliteRecorder) Query(f Filter) ([]Event, error) {
+	var where []string
+	var args []any
+	if !f.Start.IsZero() {
+		where = append(where, "ts_ns >= ?")
+		args = append(args, f.Start.UnixNano())
+	}
+	if !f.End.IsZero() {
+		where = append(where, "ts_ns <= ?")
+		args = append(args, f.End.UnixNano())
+	}
+	if f.Actor != "" {
+		where = append(where, "actor = ?")
+		args = append(args, f.Actor)
+	}
+	if f.Action != "" {
+		where = append(where, "action = ?")
+		args = append(args, f.Action)
+	}
+	if f.DS != "" {
+		where = append(where, "ds = ?")
+		args = append(args, f.DS)
+	}
+	if f.Signal != "" {
+		where = append(where, "signal LIKE ?")
+		args = append(args, "%"+f.Signal+"%")
+	}
+	limit := f.Limit
+	if limit <= 0 || limit > defaultQueryLimit {
+		limit = defaultQueryLimit
+	}
+
+	q := "SELECT ts_ns, actor, actor_type, action, ds, signal, value, detail, ip, outcome, error FROM audit_log"
+	if len(where) > 0 {
+		q += " WHERE " + strings.Join(where, " AND ")
+	}
+	q += " ORDER BY ts_ns DESC LIMIT ?"
+	args = append(args, limit)
+
+	rows, err := r.db.Query(q, args...)
+	if err != nil {
+		return nil, fmt.Errorf("query audit log: %w", err)
+	}
+	defer rows.Close()
+
+	out := []Event{}
+	for rows.Next() {
+		var e Event
+		var tsNs int64
+		if err := rows.Scan(&tsNs, &e.Actor, &e.ActorType, &e.Action,
+			&e.DS, &e.Signal, &e.Value, &e.Detail, &e.IP, &e.Outcome, &e.Error); err != nil {
+			return nil, fmt.Errorf("scan audit row: %w", err)
+		}
+		e.Time = time.Unix(0, tsNs)
+		out = append(out, e)
+	}
+	return out, rows.Err()
+}
+
+func (r *sqliteRecorder) Close() error {
+	r.once.Do(func() {
+		close(r.closed)
+		close(r.ch)
+	})
+	r.wg.Wait()
+	return r.db.Close()
+}

internal/audit/sqlite_test.go

@@ -0,0 +1,68 @@
+package audit
+
+import (
+	"log/slog"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func TestSQLiteRoundTrip(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "audit.db")
+	rec, err := NewSQLite(path, slog.Default())
+	if err != nil {
+		t.Fatal("NewSQLite:", err)
+	}
+	defer rec.Close()
+
+	base := time.Now()
+	rec.Record(Event{Time: base, Actor: "alice", ActorType: ActorUser, Action: "signal.write", DS: "epics", Signal: "PV:A", Value: "1.5"})
+	rec.Record(Event{Time: base.Add(time.Second), Actor: "flow1", ActorType: ActorSystem, Action: "signal.write", DS: "epics", Signal: "PV:B", Value: "0"})
+	rec.Record(Event{Time: base.Add(2 * time.Second), Actor: "bob", ActorType: ActorUser, Action: "interface.update", Detail: "panel-1", Outcome: OutcomeError, Error: "denied"})
+
+	// Flush the async writer.
+	if err := rec.Close(); err != nil {
+		t.Fatal("Close:", err)
+	}
+	rec, err = NewSQLite(path, slog.Default())
+	if err != nil {
+		t.Fatal("reopen:", err)
+	}
+	defer rec.Close()
+
+	all, err := rec.Query(Filter{})
+	if err != nil {
+		t.Fatal("Query:", err)
+	}
+	if len(all) != 3 {
+		t.Fatalf("got %d events, want 3", len(all))
+	}
+	// Newest first.
+	if all[0].Actor != "bob" {
+		t.Errorf("first actor = %q, want bob", all[0].Actor)
+	}
+
+	byActor, err := rec.Query(Filter{Actor: "alice"})
+	if err != nil {
+		t.Fatal("Query actor:", err)
+	}
+	if len(byActor) != 1 || byActor[0].Signal != "PV:A" {
+		t.Errorf("actor filter = %+v, want one PV:A event", byActor)
+	}
+
+	byAction, err := rec.Query(Filter{Action: "signal.write"})
+	if err != nil {
+		t.Fatal("Query action:", err)
+	}
+	if len(byAction) != 2 {
+		t.Errorf("action filter returned %d, want 2", len(byAction))
+	}
+
+	since, err := rec.Query(Filter{Start: base.Add(1500 * time.Millisecond)})
+	if err != nil {
+		t.Fatal("Query start:", err)
+	}
+	if len(since) != 1 || since[0].Actor != "bob" {
+		t.Errorf("time filter = %+v, want one bob event", since)
+	}
+}

internal/broker/broker.go

@@ -251,6 +251,31 @@ func (b *Broker) fanOut(ref SignalRef, sub *signalSub, rawCh <-chan datasource.V
 	}
 }
 
+// ReadNow performs a one-shot synchronous read of a signal's current value.
+// It starts a dedicated upstream subscription, returns the first value the data
+// source delivers, then tears the subscription down. The read is bounded by ctx
+// (callers should pass a timeout). This bypasses the shared fan-out cache because
+// not every signal of interest (e.g. arbitrary config-set targets) is otherwise
+// subscribed.
+func (b *Broker) ReadNow(ctx context.Context, ref SignalRef) (datasource.Value, error) {
+	ds, ok := b.Source(ref.DS)
+	if !ok {
+		return datasource.Value{}, fmt.Errorf("unknown data source %q", ref.DS)
+	}
+	ch := make(chan datasource.Value, 1)
+	cancel, err := ds.Subscribe(ctx, ref.Name, ch)
+	if err != nil {
+		return datasource.Value{}, fmt.Errorf("read %s/%s: %w", ref.DS, ref.Name, err)
+	}
+	defer cancel()
+	select {
+	case v := <-ch:
+		return v, nil
+	case <-ctx.Done():
+		return datasource.Value{}, ctx.Err()
+	}
+}
+
 // ActiveSubscriptions returns the number of currently active upstream signal
 // subscriptions. Useful for diagnostics and tests.
 func (b *Broker) ActiveSubscriptions() int {

internal/config/config.go

@@ -12,10 +12,23 @@ import (
 type Config struct {
 	Server     ServerConfig     `toml:"server"`
 	Datasource DatasourceConfig `toml:"datasource"`
+	Audit      AuditConfig      `toml:"audit"`
 	// Groups are named sets of users, referenced by panel sharing rules.
 	Groups []GroupDef `toml:"groups"`
 }
 
+// AuditConfig controls the audit trail. When enabled, every user and automated
+// action that could affect the controlled system (signal writes, control-logic
+// changes) is recorded to a SQLite database for later review by audit staff.
+type AuditConfig struct {
+	Enabled bool   `toml:"enabled"`
+	DBPath  string `toml:"db_path"` // SQLite file; default {storage_dir}/audit.db
+	// Readers lists users or group names allowed to view the audit log. Empty
+	// leaves viewing unrestricted (any caller with read access). Anonymous /
+	// trusted-LAN callers are always permitted.
+	Readers []string `toml:"readers"`
+}
+
 // GroupDef is a named set of users defined as [[groups]] in the config file.
 type GroupDef struct {
 	Name    string   `toml:"name"`
@@ -141,6 +154,15 @@ func applyEnv(cfg *Config) {
 	if v := env("UOPI_SERVER_LOGIC_EDITORS"); v != "" {
 		cfg.Server.LogicEditors = strings.Fields(v)
 	}
+	if v := env("UOPI_AUDIT_ENABLED"); v != "" {
+		cfg.Audit.Enabled = (v == "true" || v == "YES")
+	}
+	if v := env("UOPI_AUDIT_DB_PATH"); v != "" {
+		cfg.Audit.DBPath = v
+	}
+	if v := env("UOPI_AUDIT_READERS"); v != "" {
+		cfg.Audit.Readers = strings.Fields(v)
+	}
 	if v := env("UOPI_EPICS_CA_ADDR_LIST"); v != "" {
 		cfg.Datasource.EPICS.CAAddrList = v
 	}

internal/confmgr/apply.go

@@ -0,0 +1,56 @@
+package confmgr
+
+// WriteFunc writes a resolved value to a target signal. The API layer supplies
+// a closure backed by the broker/datasource so confmgr stays decoupled from the
+// transport.
+type WriteFunc func(ds, signal string, value any) error
+
+// ApplyEntry records the outcome of writing one parameter.
+type ApplyEntry struct {
+	Key     string `json:"key"`
+	DS      string `json:"ds"`
+	Signal  string `json:"signal"`
+	Value   any    `json:"value,omitempty"`
+	OK      bool   `json:"ok"`
+	Skipped bool   `json:"skipped,omitempty"`
+	Error   string `json:"error,omitempty"`
+}
+
+// ApplyResult summarises an apply run.
+type ApplyResult struct {
+	InstanceID string       `json:"instanceId"`
+	SetID      string       `json:"setId"`
+	Entries    []ApplyEntry `json:"entries"`
+	Applied    int          `json:"applied"`
+	Failed     int          `json:"failed"`
+	Skipped    int          `json:"skipped"`
+}
+
+// Apply writes every resolvable parameter value of an instance to its target
+// signal via write. Optional parameters with no value and no default are
+// skipped. Individual write failures are recorded per-entry rather than
+// aborting the whole apply, so a partial apply is reported faithfully.
+func Apply(set ConfigSet, inst ConfigInstance, write WriteFunc) ApplyResult {
+	res := ApplyResult{InstanceID: inst.ID, SetID: set.ID, Entries: make([]ApplyEntry, 0, len(set.Parameters))}
+	for _, p := range set.Parameters {
+		e := ApplyEntry{Key: p.Key, DS: p.DS, Signal: p.Signal}
+		v, ok := inst.Resolve(p)
+		if !ok {
+			e.Skipped = true
+			res.Skipped++
+			res.Entries = append(res.Entries, e)
+			continue
+		}
+		v = p.normalize(v)
+		e.Value = v
+		if err := write(p.DS, p.Signal, v); err != nil {
+			e.Error = err.Error()
+			res.Failed++
+		} else {
+			e.OK = true
+			res.Applied++
+		}
+		res.Entries = append(res.Entries, e)
+	}
+	return res
+}

internal/confmgr/apply_test.go

@@ -0,0 +1,108 @@
+package confmgr
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestApplyWritesValues(t *testing.T) {
+	set := ConfigSet{
+		ID:   "set1",
+		Name: "s",
+		Parameters: []Parameter{
+			{Key: "v", DS: "epics", Signal: "PSU:V", Type: TypeFloat, Default: 12.0},
+			{Key: "en", DS: "epics", Signal: "PSU:EN", Type: TypeBool},
+			{Key: "opt", DS: "epics", Signal: "PSU:OPT", Type: TypeFloat}, // no value, no default → skipped
+		},
+	}
+	inst := ConfigInstance{ID: "i1", SetID: "set1", Values: map[string]any{"v": 24.0, "en": true}}
+
+	type write struct {
+		ds, sig string
+		val     any
+	}
+	var writes []write
+	res := Apply(set, inst, func(ds, signal string, value any) error {
+		writes = append(writes, write{ds, signal, value})
+		return nil
+	})
+
+	if res.Applied != 2 || res.Skipped != 1 || res.Failed != 0 {
+		t.Fatalf("summary: applied=%d skipped=%d failed=%d", res.Applied, res.Skipped, res.Failed)
+	}
+	if len(writes) != 2 {
+		t.Fatalf("want 2 writes, got %d", len(writes))
+	}
+	if writes[0].sig != "PSU:V" || writes[0].val != 24.0 {
+		t.Errorf("first write: %+v", writes[0])
+	}
+}
+
+func TestApplyUsesDefaultWhenNoValue(t *testing.T) {
+	set := ConfigSet{
+		ID: "set1", Name: "s",
+		Parameters: []Parameter{{Key: "v", DS: "d", Signal: "S", Type: TypeFloat, Default: 7.0}},
+	}
+	inst := ConfigInstance{ID: "i", SetID: "set1", Values: map[string]any{}}
+	var got any
+	res := Apply(set, inst, func(_, _ string, value any) error { got = value; return nil })
+	if res.Applied != 1 || got != 7.0 {
+		t.Errorf("want default 7.0 applied, got %v (applied=%d)", got, res.Applied)
+	}
+}
+
+func TestApplyArrayNormalizes(t *testing.T) {
+	set := ConfigSet{ID: "s", Name: "s", Parameters: []Parameter{
+		{Key: "wf", DS: "d", Signal: "WF", Type: TypeFloatArray},
+	}}
+	// JSON decoding yields []any of float64 — apply must hand the datasource a []float64.
+	inst := ConfigInstance{ID: "i", SetID: "s", Values: map[string]any{"wf": []any{1.0, 2.0, 3.0}}}
+	var got any
+	res := Apply(set, inst, func(_, _ string, value any) error { got = value; return nil })
+	if res.Applied != 1 {
+		t.Fatalf("applied=%d", res.Applied)
+	}
+	arr, ok := got.([]float64)
+	if !ok || len(arr) != 3 || arr[0] != 1 || arr[2] != 3 {
+		t.Fatalf("want []float64{1,2,3}, got %T %v", got, got)
+	}
+}
+
+func TestArrayValidation(t *testing.T) {
+	lo := 0.0
+	p := Parameter{Key: "wf", DS: "d", Signal: "S", Type: TypeFloatArray, Min: &lo}
+	if err := p.checkValue([]any{1.0, 2.0}); err != nil {
+		t.Fatalf("valid array rejected: %v", err)
+	}
+	if err := p.checkValue([]any{1.0, -5.0}); err == nil {
+		t.Fatal("expected out-of-range element to be rejected")
+	}
+	if err := p.checkValue("notarray"); err == nil {
+		t.Fatal("expected non-array value to be rejected")
+	}
+}
+
+func TestApplyRecordsFailures(t *testing.T) {
+	set := ConfigSet{
+		ID: "set1", Name: "s",
+		Parameters: []Parameter{
+			{Key: "a", DS: "d", Signal: "A", Type: TypeFloat, Default: 1.0},
+			{Key: "b", DS: "d", Signal: "B", Type: TypeFloat, Default: 2.0},
+		},
+	}
+	inst := ConfigInstance{ID: "i", SetID: "set1", Values: map[string]any{}}
+	res := Apply(set, inst, func(_, signal string, _ any) error {
+		if signal == "B" {
+			return errors.New("write rejected")
+		}
+		return nil
+	})
+	if res.Applied != 1 || res.Failed != 1 {
+		t.Fatalf("want applied=1 failed=1, got applied=%d failed=%d", res.Applied, res.Failed)
+	}
+	for _, e := range res.Entries {
+		if e.Key == "b" && (e.OK || e.Error == "") {
+			t.Errorf("entry b should record failure: %+v", e)
+		}
+	}
+}

internal/confmgr/cue.go

@@ -0,0 +1,199 @@
+package confmgr
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	"cuelang.org/go/cue"
+	"cuelang.org/go/cue/cuecontext"
+	cueerrors "cuelang.org/go/cue/errors"
+)
+
+// ConfigRule is a CUE-based validation/transformation rule bound to a config
+// set. Its Source is CUE describing constraints and/or derivations over the
+// instance's parameter values. Regular CUE fields whose key matches a set
+// parameter are unified with the instance value; constraints that fail produce
+// violations, and concrete fields that differ from the instance value are
+// reported (and persisted) as transformations. Hidden fields (_x) and
+// definitions (#X) are available for helpers and are excluded from both
+// concreteness checks and transformation output. Rules are versioned git-style,
+// exactly like sets and instances.
+type ConfigRule struct {
+	ID          string `json:"id"`
+	Name        string `json:"name"`
+	SetID       string `json:"setId"`
+	Description string `json:"description,omitempty"`
+	Version     int    `json:"version"`
+	Tag         string `json:"tag,omitempty"`
+	Owner       string `json:"owner,omitempty"`
+	Source      string `json:"source"`
+}
+
+// RuleViolation is a single constraint failure from evaluating a rule.
+type RuleViolation struct {
+	Rule    string `json:"rule,omitempty"` // rule ID that produced it (aggregate runs)
+	Path    string `json:"path,omitempty"` // dotted parameter path, when known
+	Message string `json:"message"`
+}
+
+// RuleResult is the outcome of evaluating one or more rules against a set of
+// instance values. OK is true only when there is no compile error and no
+// violation. Transformed holds the parameter values the rule(s) derived or
+// overrode (keys are parameter keys; values are the new concrete values).
+type RuleResult struct {
+	OK           bool             `json:"ok"`
+	Violations   []RuleViolation  `json:"violations,omitempty"`
+	Transformed  map[string]any   `json:"transformed,omitempty"`
+	CompileError string           `json:"compileError,omitempty"`
+}
+
+// RuleError wraps a failing RuleResult so it can flow through the store's
+// error-returning API while preserving the structured violations.
+type RuleError struct {
+	Result RuleResult
+}
+
+func (e *RuleError) Error() string {
+	if e.Result.CompileError != "" {
+		return "rule compile error: " + e.Result.CompileError
+	}
+	msgs := make([]string, 0, len(e.Result.Violations))
+	for _, v := range e.Result.Violations {
+		if v.Path != "" {
+			msgs = append(msgs, v.Path+": "+v.Message)
+		} else {
+			msgs = append(msgs, v.Message)
+		}
+	}
+	if len(msgs) == 0 {
+		return "rule validation failed"
+	}
+	return "rule validation failed: " + strings.Join(msgs, "; ")
+}
+
+// Validate compiles the rule's CUE source and checks basic metadata. It does
+// not require concrete values — only that the source is syntactically and
+// structurally well-formed CUE.
+func (r ConfigRule) Validate() error {
+	if strings.TrimSpace(r.Name) == "" {
+		return fmt.Errorf("rule name must not be empty")
+	}
+	if strings.TrimSpace(r.SetID) == "" {
+		return fmt.Errorf("rule must reference a config set")
+	}
+	ctx := cuecontext.New()
+	v := ctx.CompileString(r.Source)
+	if err := v.Err(); err != nil {
+		return fmt.Errorf("invalid CUE: %s", firstError(err))
+	}
+	return nil
+}
+
+// EvaluateRule unifies a single CUE source with the given instance values and
+// reports violations plus any transformed values. A compile error yields a
+// non-OK result with CompileError populated (and no violations), so callers can
+// distinguish "the rule is broken" from "the values are invalid".
+func EvaluateRule(source string, values map[string]any) RuleResult {
+	ctx := cuecontext.New()
+	schema := ctx.CompileString(source)
+	if err := schema.Err(); err != nil {
+		return RuleResult{OK: false, CompileError: firstError(err)}
+	}
+	data := ctx.Encode(values)
+	if err := data.Err(); err != nil {
+		return RuleResult{OK: false, CompileError: "cannot encode values: " + firstError(err)}
+	}
+	unified := schema.Unify(data)
+
+	res := RuleResult{OK: true}
+	if err := unified.Validate(cue.Concrete(true), cue.All()); err != nil {
+		res.OK = false
+		for _, e := range cueerrors.Errors(err) {
+			res.Violations = append(res.Violations, RuleViolation{
+				Path:    strings.Join(e.Path(), "."),
+				Message: cleanMessage(e),
+			})
+		}
+		if len(res.Violations) == 0 {
+			res.Violations = append(res.Violations, RuleViolation{Message: firstError(err)})
+		}
+		return res
+	}
+
+	// Extract transformations: regular concrete fields whose value differs from
+	// the supplied input. Definitions and hidden fields are skipped by Fields().
+	iter, err := unified.Fields()
+	if err != nil {
+		return res
+	}
+	for iter.Next() {
+		key := iter.Selector().Unquoted()
+		if key == "" {
+			key = strings.Trim(iter.Selector().String(), `"`)
+		}
+		var v any
+		if err := iter.Value().Decode(&v); err != nil {
+			continue
+		}
+		if !reflect.DeepEqual(v, values[key]) {
+			if res.Transformed == nil {
+				res.Transformed = map[string]any{}
+			}
+			res.Transformed[key] = v
+		}
+	}
+	return res
+}
+
+// evaluateRules runs several rules against the same values and aggregates the
+// outcome. Violations are tagged with the rule ID. Transformations are applied
+// cumulatively in order; a later rule sees earlier rules' outputs.
+func evaluateRules(rules []ConfigRule, values map[string]any) RuleResult {
+	agg := RuleResult{OK: true}
+	cur := make(map[string]any, len(values))
+	for k, v := range values {
+		cur[k] = v
+	}
+	for _, r := range rules {
+		one := EvaluateRule(r.Source, cur)
+		if one.CompileError != "" {
+			agg.OK = false
+			agg.Violations = append(agg.Violations, RuleViolation{Rule: r.ID, Message: "compile error: " + one.CompileError})
+			continue
+		}
+		if !one.OK {
+			agg.OK = false
+			for _, v := range one.Violations {
+				v.Rule = r.ID
+				agg.Violations = append(agg.Violations, v)
+			}
+			continue
+		}
+		for k, v := range one.Transformed {
+			if agg.Transformed == nil {
+				agg.Transformed = map[string]any{}
+			}
+			agg.Transformed[k] = v
+			cur[k] = v
+		}
+	}
+	return agg
+}
+
+// firstError renders the first CUE error as a single line.
+func firstError(err error) string {
+	errs := cueerrors.Errors(err)
+	if len(errs) == 0 {
+		return err.Error()
+	}
+	return cleanMessage(errs[0])
+}
+
+// cleanMessage formats a CUE error to a compact single-line string without the
+// noisy file:line position prefix that cuecontext synthesises for anonymous
+// sources.
+func cleanMessage(e cueerrors.Error) string {
+	format, args := e.Msg()
+	return fmt.Sprintf(format, args...)
+}

internal/confmgr/cue_test.go

@@ -0,0 +1,80 @@
+package confmgr
+
+import "testing"
+
+func TestEvaluateRule_Valid(t *testing.T) {
+	src := `
+current_limit: >=0 & <=max
+max: 100
+`
+	res := EvaluateRule(src, map[string]any{"current_limit": 50.0})
+	if !res.OK {
+		t.Fatalf("expected OK, got violations: %+v compile=%q", res.Violations, res.CompileError)
+	}
+	if res.CompileError != "" {
+		t.Fatalf("unexpected compile error: %s", res.CompileError)
+	}
+}
+
+func TestEvaluateRule_Violation(t *testing.T) {
+	src := `current_limit: >=0 & <=100`
+	res := EvaluateRule(src, map[string]any{"current_limit": 150.0})
+	if res.OK {
+		t.Fatalf("expected violation, got OK")
+	}
+	if len(res.Violations) == 0 {
+		t.Fatalf("expected at least one violation")
+	}
+}
+
+func TestEvaluateRule_Transform(t *testing.T) {
+	// power is derived from the supplied current & voltage.
+	src := `
+current: number
+voltage: number
+power: current * voltage
+`
+	res := EvaluateRule(src, map[string]any{"current": 2.0, "voltage": 3.0})
+	if !res.OK {
+		t.Fatalf("expected OK, got %+v", res.Violations)
+	}
+	got, ok := res.Transformed["power"]
+	if !ok {
+		t.Fatalf("expected transformed power, got %+v", res.Transformed)
+	}
+	if f, _ := toFloat(got); f != 6 {
+		t.Fatalf("expected power=6, got %v", got)
+	}
+}
+
+func TestEvaluateRule_DefaultFillsMissing(t *testing.T) {
+	src := `mode: *"auto" | "manual"`
+	res := EvaluateRule(src, map[string]any{})
+	if !res.OK {
+		t.Fatalf("expected OK, got %+v", res.Violations)
+	}
+	if res.Transformed["mode"] != "auto" {
+		t.Fatalf("expected mode default auto, got %v", res.Transformed["mode"])
+	}
+}
+
+func TestEvaluateRule_CompileError(t *testing.T) {
+	res := EvaluateRule(`this is : : not cue`, map[string]any{})
+	if res.OK || res.CompileError == "" {
+		t.Fatalf("expected compile error, got %+v", res)
+	}
+}
+
+func TestConfigRule_Validate(t *testing.T) {
+	r := ConfigRule{Name: "r", SetID: "s", Source: `x: >=0`}
+	if err := r.Validate(); err != nil {
+		t.Fatalf("expected valid rule, got %v", err)
+	}
+	bad := ConfigRule{Name: "r", SetID: "s", Source: `x: : :`}
+	if err := bad.Validate(); err == nil {
+		t.Fatalf("expected compile error for bad source")
+	}
+	if err := (ConfigRule{Source: `x: 1`}).Validate(); err == nil {
+		t.Fatalf("expected error for missing name/setID")
+	}
+}

internal/confmgr/diff.go

@@ -0,0 +1,140 @@
+package confmgr
+
+import (
+	"fmt"
+	"sort"
+)
+
+// ChangeStatus classifies a single diff entry.
+type ChangeStatus string
+
+const (
+	StatusAdded     ChangeStatus = "added"
+	StatusRemoved   ChangeStatus = "removed"
+	StatusChanged   ChangeStatus = "changed"
+	StatusUnchanged ChangeStatus = "unchanged"
+)
+
+// SetDiffEntry is one parameter-level difference between two config sets.
+type SetDiffEntry struct {
+	Key    string       `json:"key"`
+	Status ChangeStatus `json:"status"`
+	Left   *Parameter   `json:"left,omitempty"`
+	Right  *Parameter   `json:"right,omitempty"`
+}
+
+// InstanceDiffEntry is one value-level difference between two config instances.
+type InstanceDiffEntry struct {
+	Key    string       `json:"key"`
+	Status ChangeStatus `json:"status"`
+	Left   any          `json:"left,omitempty"`
+	Right  any          `json:"right,omitempty"`
+}
+
+// DiffSets compares two config sets parameter-by-parameter (keyed by Key),
+// returning entries sorted by key. Both sides are included so the frontend can
+// render either unified or side-by-side.
+func DiffSets(left, right ConfigSet) []SetDiffEntry {
+	keys := map[string]bool{}
+	li := map[string]Parameter{}
+	ri := map[string]Parameter{}
+	for _, p := range left.Parameters {
+		li[p.Key] = p
+		keys[p.Key] = true
+	}
+	for _, p := range right.Parameters {
+		ri[p.Key] = p
+		keys[p.Key] = true
+	}
+	out := make([]SetDiffEntry, 0, len(keys))
+	for k := range keys {
+		l, lok := li[k]
+		r, rok := ri[k]
+		e := SetDiffEntry{Key: k}
+		switch {
+		case lok && !rok:
+			e.Status = StatusRemoved
+			lp := l
+			e.Left = &lp
+		case !lok && rok:
+			e.Status = StatusAdded
+			rp := r
+			e.Right = &rp
+		default:
+			lp, rp := l, r
+			e.Left, e.Right = &lp, &rp
+			if paramEqual(l, r) {
+				e.Status = StatusUnchanged
+			} else {
+				e.Status = StatusChanged
+			}
+		}
+		out = append(out, e)
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Key < out[j].Key })
+	return out
+}
+
+// DiffInstances compares two config instances value-by-value (keyed by
+// parameter key), returning entries sorted by key.
+func DiffInstances(left, right ConfigInstance) []InstanceDiffEntry {
+	keys := map[string]bool{}
+	for k := range left.Values {
+		keys[k] = true
+	}
+	for k := range right.Values {
+		keys[k] = true
+	}
+	out := make([]InstanceDiffEntry, 0, len(keys))
+	for k := range keys {
+		lv, lok := left.Values[k]
+		rv, rok := right.Values[k]
+		e := InstanceDiffEntry{Key: k, Left: lv, Right: rv}
+		switch {
+		case lok && !rok:
+			e.Status = StatusRemoved
+		case !lok && rok:
+			e.Status = StatusAdded
+		case valueEqual(lv, rv):
+			e.Status = StatusUnchanged
+		default:
+			e.Status = StatusChanged
+		}
+		out = append(out, e)
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Key < out[j].Key })
+	return out
+}
+
+func paramEqual(a, b Parameter) bool {
+	if a.Label != b.Label || a.Group != b.Group || a.Subgroup != b.Subgroup ||
+		a.DS != b.DS || a.Signal != b.Signal || a.Type != b.Type ||
+		a.Mandatory != b.Mandatory || a.Unit != b.Unit || a.Description != b.Description {
+		return false
+	}
+	if !valueEqual(a.Default, b.Default) || !floatPtrEqual(a.Min, b.Min) || !floatPtrEqual(a.Max, b.Max) {
+		return false
+	}
+	if len(a.EnumValues) != len(b.EnumValues) {
+		return false
+	}
+	for i := range a.EnumValues {
+		if a.EnumValues[i] != b.EnumValues[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func floatPtrEqual(a, b *float64) bool {
+	if a == nil || b == nil {
+		return a == b
+	}
+	return *a == *b
+}
+
+// valueEqual compares two JSON-decoded scalar values for diff purposes by
+// rendering them to a canonical string.
+func valueEqual(a, b any) bool {
+	return fmt.Sprintf("%v", a) == fmt.Sprintf("%v", b)
+}

internal/confmgr/diff_test.go

@@ -0,0 +1,55 @@
+package confmgr
+
+import "testing"
+
+func TestDiffSets(t *testing.T) {
+	left := ConfigSet{Parameters: []Parameter{
+		{Key: "a", DS: "d", Signal: "A", Type: TypeFloat, Default: 1.0},
+		{Key: "b", DS: "d", Signal: "B", Type: TypeFloat},
+	}}
+	right := ConfigSet{Parameters: []Parameter{
+		{Key: "a", DS: "d", Signal: "A", Type: TypeFloat, Default: 2.0}, // changed default
+		{Key: "c", DS: "d", Signal: "C", Type: TypeFloat},               // added
+	}}
+	diff := DiffSets(left, right)
+	got := map[string]ChangeStatus{}
+	for _, e := range diff {
+		got[e.Key] = e.Status
+	}
+	if got["a"] != StatusChanged {
+		t.Errorf("a: want changed, got %s", got["a"])
+	}
+	if got["b"] != StatusRemoved {
+		t.Errorf("b: want removed, got %s", got["b"])
+	}
+	if got["c"] != StatusAdded {
+		t.Errorf("c: want added, got %s", got["c"])
+	}
+}
+
+func TestDiffSetsUnchanged(t *testing.T) {
+	p := Parameter{Key: "a", DS: "d", Signal: "A", Type: TypeFloat, Default: 1.0}
+	diff := DiffSets(ConfigSet{Parameters: []Parameter{p}}, ConfigSet{Parameters: []Parameter{p}})
+	if len(diff) != 1 || diff[0].Status != StatusUnchanged {
+		t.Errorf("want single unchanged entry, got %+v", diff)
+	}
+}
+
+func TestDiffInstances(t *testing.T) {
+	left := ConfigInstance{Values: map[string]any{"a": 1.0, "b": "x"}}
+	right := ConfigInstance{Values: map[string]any{"a": 2.0, "c": true}}
+	diff := DiffInstances(left, right)
+	got := map[string]ChangeStatus{}
+	for _, e := range diff {
+		got[e.Key] = e.Status
+	}
+	if got["a"] != StatusChanged {
+		t.Errorf("a: want changed, got %s", got["a"])
+	}
+	if got["b"] != StatusRemoved {
+		t.Errorf("b: want removed, got %s", got["b"])
+	}
+	if got["c"] != StatusAdded {
+		t.Errorf("c: want added, got %s", got["c"])
+	}
+}

internal/confmgr/model.go

@@ -0,0 +1,273 @@
+// Package confmgr implements the configuration manager: versioned, git-style
+// configuration Sets (schemas of parameters bound to target signals) and
+// configuration Instances (concrete values for a set), persisted as versioned
+// JSON files. Applying an instance writes each value to its target signal.
+package confmgr
+
+import (
+	"fmt"
+	"math"
+	"slices"
+	"strconv"
+	"strings"
+)
+
+// ParamType enumerates the value kinds a parameter may hold.
+type ParamType string
+
+const (
+	TypeFloat      ParamType = "float64"
+	TypeInt        ParamType = "int64"
+	TypeBool       ParamType = "bool"
+	TypeString     ParamType = "string"
+	TypeEnum       ParamType = "enum"
+	TypeFloatArray ParamType = "float64[]" // waveform; value is a list of numbers
+)
+
+func (t ParamType) valid() bool {
+	switch t {
+	case TypeFloat, TypeInt, TypeBool, TypeString, TypeEnum, TypeFloatArray:
+		return true
+	}
+	return false
+}
+
+// Parameter is one entry in a configuration set's schema. It names a target
+// signal (DS + Signal), a value type, an optional default, and validation
+// metadata. Parameters may be grouped for presentation via Group/Subgroup.
+type Parameter struct {
+	Key         string    `json:"key"`              // unique within the set
+	Label       string    `json:"label,omitempty"`  // human-friendly name
+	Group       string    `json:"group,omitempty"`  // top-level grouping
+	Subgroup    string    `json:"subgroup,omitempty"`
+	DS          string    `json:"ds"`               // target data source
+	Signal      string    `json:"signal"`           // target signal name
+	Type        ParamType `json:"type"`             // value kind
+	Default     any       `json:"default,omitempty"`
+	Mandatory   bool      `json:"mandatory,omitempty"`
+	Min         *float64  `json:"min,omitempty"`         // numeric lower bound
+	Max         *float64  `json:"max,omitempty"`         // numeric upper bound
+	EnumValues  []string  `json:"enumValues,omitempty"`  // allowed values for enum
+	Unit        string    `json:"unit,omitempty"`
+	Description string    `json:"description,omitempty"`
+}
+
+// ConfigSet is the schema half of the two-tier model: an ordered list of
+// parameters bound to target signals. It is versioned git-style.
+type ConfigSet struct {
+	ID          string      `json:"id"`
+	Name        string      `json:"name"`
+	Description string      `json:"description,omitempty"`
+	Version     int         `json:"version"`
+	Tag         string      `json:"tag,omitempty"`
+	Owner       string      `json:"owner,omitempty"`
+	Parameters  []Parameter `json:"parameters"`
+}
+
+// ConfigInstance is the value half: concrete values for a set's parameters,
+// keyed by parameter key. SetID pins the schema it belongs to; SetVersion pins
+// the schema revision (0 means "track current"). It is versioned git-style.
+type ConfigInstance struct {
+	ID         string         `json:"id"`
+	Name       string         `json:"name"`
+	SetID      string         `json:"setId"`
+	SetVersion int            `json:"setVersion,omitempty"` // 0 = current set version
+	Version    int            `json:"version"`
+	Tag        string         `json:"tag,omitempty"`
+	Owner      string         `json:"owner,omitempty"`
+	Values     map[string]any `json:"values"`
+}
+
+// Validate checks structural invariants of a config set: non-empty name,
+// unique non-empty parameter keys, valid types, a target signal per parameter,
+// and well-formed enum/default metadata.
+func (s ConfigSet) Validate() error {
+	if strings.TrimSpace(s.Name) == "" {
+		return fmt.Errorf("config set name must not be empty")
+	}
+	seen := make(map[string]bool, len(s.Parameters))
+	for i, p := range s.Parameters {
+		if strings.TrimSpace(p.Key) == "" {
+			return fmt.Errorf("parameter %d: key must not be empty", i)
+		}
+		if seen[p.Key] {
+			return fmt.Errorf("duplicate parameter key %q", p.Key)
+		}
+		seen[p.Key] = true
+		if !p.Type.valid() {
+			return fmt.Errorf("parameter %q: invalid type %q", p.Key, p.Type)
+		}
+		if strings.TrimSpace(p.DS) == "" || strings.TrimSpace(p.Signal) == "" {
+			return fmt.Errorf("parameter %q: target ds and signal are required", p.Key)
+		}
+		if p.Type == TypeEnum && len(p.EnumValues) == 0 {
+			return fmt.Errorf("parameter %q: enum type requires enumValues", p.Key)
+		}
+		if p.Min != nil && p.Max != nil && *p.Min > *p.Max {
+			return fmt.Errorf("parameter %q: min %v greater than max %v", p.Key, *p.Min, *p.Max)
+		}
+		if p.Default != nil {
+			if err := p.checkValue(p.Default); err != nil {
+				return fmt.Errorf("parameter %q default: %w", p.Key, err)
+			}
+		}
+	}
+	return nil
+}
+
+// param returns the parameter with the given key, or false.
+func (s ConfigSet) param(key string) (Parameter, bool) {
+	for _, p := range s.Parameters {
+		if p.Key == key {
+			return p, true
+		}
+	}
+	return Parameter{}, false
+}
+
+// ValidateAgainst checks an instance against its set: every value references a
+// known parameter and is type/range valid; every mandatory parameter without a
+// default has a value.
+func (inst ConfigInstance) ValidateAgainst(set ConfigSet) error {
+	for key, v := range inst.Values {
+		p, ok := set.param(key)
+		if !ok {
+			return fmt.Errorf("value for unknown parameter %q", key)
+		}
+		if err := p.checkValue(v); err != nil {
+			return fmt.Errorf("parameter %q: %w", key, err)
+		}
+	}
+	for _, p := range set.Parameters {
+		if !p.Mandatory {
+			continue
+		}
+		if _, ok := inst.Values[p.Key]; ok {
+			continue
+		}
+		if p.Default == nil {
+			return fmt.Errorf("mandatory parameter %q has no value", p.Key)
+		}
+	}
+	return nil
+}
+
+// Resolve returns the effective value for a parameter: the instance value when
+// present, otherwise the parameter default. The second result is false when no
+// value is available (optional parameter, no default).
+func (inst ConfigInstance) Resolve(p Parameter) (any, bool) {
+	if v, ok := inst.Values[p.Key]; ok {
+		return v, true
+	}
+	if p.Default != nil {
+		return p.Default, true
+	}
+	return nil, false
+}
+
+// checkValue verifies a value matches the parameter's type and constraints.
+func (p Parameter) checkValue(v any) error {
+	switch p.Type {
+	case TypeFloat, TypeInt:
+		f, err := toFloat(v)
+		if err != nil {
+			return err
+		}
+		if p.Type == TypeInt && f != math.Trunc(f) {
+			return fmt.Errorf("value %v is not an integer", f)
+		}
+		if p.Min != nil && f < *p.Min {
+			return fmt.Errorf("value %v below minimum %v", f, *p.Min)
+		}
+		if p.Max != nil && f > *p.Max {
+			return fmt.Errorf("value %v above maximum %v", f, *p.Max)
+		}
+	case TypeBool:
+		if _, ok := v.(bool); !ok {
+			return fmt.Errorf("value %v is not a bool", v)
+		}
+	case TypeString:
+		if _, ok := v.(string); !ok {
+			return fmt.Errorf("value %v is not a string", v)
+		}
+	case TypeEnum:
+		s, ok := v.(string)
+		if !ok {
+			return fmt.Errorf("enum value %v is not a string", v)
+		}
+		if !slices.Contains(p.EnumValues, s) {
+			return fmt.Errorf("value %q is not an allowed enum value", s)
+		}
+	case TypeFloatArray:
+		arr, err := toFloatArray(v)
+		if err != nil {
+			return err
+		}
+		for i, f := range arr {
+			if p.Min != nil && f < *p.Min {
+				return fmt.Errorf("element %d value %v below minimum %v", i, f, *p.Min)
+			}
+			if p.Max != nil && f > *p.Max {
+				return fmt.Errorf("element %d value %v above maximum %v", i, f, *p.Max)
+			}
+		}
+	}
+	return nil
+}
+
+// normalize coerces a JSON-decoded value into the canonical Go type the
+// datasource write path expects. Array parameters become []float64 (JSON yields
+// []any); scalar values are returned unchanged.
+func (p Parameter) normalize(v any) any {
+	if p.Type == TypeFloatArray {
+		if arr, err := toFloatArray(v); err == nil {
+			return arr
+		}
+	}
+	return v
+}
+
+// toFloatArray coerces a JSON-decoded array value to []float64. JSON
+// unmarshalling yields []any of float64, but a native []float64 is also
+// accepted.
+func toFloatArray(v any) ([]float64, error) {
+	switch a := v.(type) {
+	case []float64:
+		return a, nil
+	case []any:
+		out := make([]float64, len(a))
+		for i, e := range a {
+			f, err := toFloat(e)
+			if err != nil {
+				return nil, fmt.Errorf("element %d: %w", i, err)
+			}
+			out[i] = f
+		}
+		return out, nil
+	default:
+		return nil, fmt.Errorf("value %v is not an array", v)
+	}
+}
+
+// toFloat coerces a JSON-decoded numeric value to float64. JSON unmarshalling
+// yields float64 for numbers, but values may also arrive as int or string.
+func toFloat(v any) (float64, error) {
+	switch n := v.(type) {
+	case float64:
+		return n, nil
+	case float32:
+		return float64(n), nil
+	case int:
+		return float64(n), nil
+	case int64:
+		return float64(n), nil
+	case string:
+		f, err := strconv.ParseFloat(n, 64)
+		if err != nil {
+			return 0, fmt.Errorf("value %q is not numeric", n)
+		}
+		return f, nil
+	default:
+		return 0, fmt.Errorf("value %v is not numeric", v)
+	}
+}

internal/confmgr/snapshot.go

@@ -0,0 +1,129 @@
+package confmgr
+
+import (
+	"fmt"
+	"math"
+	"slices"
+	"strconv"
+)
+
+// ReadFunc reads the current raw value of a target signal. The API/engine layer
+// supplies a closure backed by the broker (ReadNow) so confmgr stays decoupled
+// from the transport. The returned value mirrors datasource.Value.Data
+// (float64 | []float64 | string | int64 | bool; enums arrive as an int64 index).
+type ReadFunc func(ds, signal string) (any, error)
+
+// SnapshotEntry records the outcome of reading one parameter's target signal.
+type SnapshotEntry struct {
+	Key    string `json:"key"`
+	DS     string `json:"ds"`
+	Signal string `json:"signal"`
+	Value  any    `json:"value,omitempty"`
+	OK     bool   `json:"ok"`
+	Error  string `json:"error,omitempty"`
+}
+
+// SnapshotResult summarises a snapshot run. Values holds the captured,
+// type-coerced values ready to populate a new ConfigInstance.
+type SnapshotResult struct {
+	SetID    string         `json:"setId"`
+	Entries  []SnapshotEntry `json:"entries"`
+	Captured int            `json:"captured"`
+	Failed   int            `json:"failed"`
+	Values   map[string]any `json:"-"`
+}
+
+// Snapshot reads the current value of every parameter's target signal via read
+// and builds a value map for a new instance. Read failures and values that
+// cannot be coerced to the parameter's type are recorded per-entry rather than
+// aborting the whole snapshot, so a partial capture is reported faithfully.
+func Snapshot(set ConfigSet, read ReadFunc) SnapshotResult {
+	res := SnapshotResult{
+		SetID:   set.ID,
+		Entries: make([]SnapshotEntry, 0, len(set.Parameters)),
+		Values:  make(map[string]any, len(set.Parameters)),
+	}
+	for _, p := range set.Parameters {
+		e := SnapshotEntry{Key: p.Key, DS: p.DS, Signal: p.Signal}
+		raw, err := read(p.DS, p.Signal)
+		if err != nil {
+			e.Error = err.Error()
+			res.Failed++
+			res.Entries = append(res.Entries, e)
+			continue
+		}
+		v, err := p.coerceSnapshot(raw)
+		if err != nil {
+			e.Error = err.Error()
+			res.Failed++
+			res.Entries = append(res.Entries, e)
+			continue
+		}
+		e.Value = v
+		e.OK = true
+		res.Values[p.Key] = v
+		res.Captured++
+		res.Entries = append(res.Entries, e)
+	}
+	return res
+}
+
+// coerceSnapshot converts a raw datasource value into the canonical Go value the
+// parameter's type expects, so the result passes checkValue and serialises
+// cleanly. Enum signals arrive as an int64 index and are mapped to their string.
+func (p Parameter) coerceSnapshot(raw any) (any, error) {
+	switch p.Type {
+	case TypeFloat:
+		return toFloat(raw)
+	case TypeInt:
+		f, err := toFloat(raw)
+		if err != nil {
+			return nil, err
+		}
+		return int64(math.Round(f)), nil
+	case TypeBool:
+		switch b := raw.(type) {
+		case bool:
+			return b, nil
+		case string:
+			pb, err := strconv.ParseBool(b)
+			if err != nil {
+				return nil, fmt.Errorf("value %q is not a bool", b)
+			}
+			return pb, nil
+		default:
+			f, err := toFloat(raw)
+			if err != nil {
+				return nil, fmt.Errorf("value %v is not a bool", raw)
+			}
+			return f != 0, nil
+		}
+	case TypeString:
+		if s, ok := raw.(string); ok {
+			return s, nil
+		}
+		return fmt.Sprintf("%v", raw), nil
+	case TypeEnum:
+		// Enum signals deliver an int64 index into the metadata strings; map it
+		// to this parameter's enum value. A string already in range is kept.
+		if s, ok := raw.(string); ok {
+			if slices.Contains(p.EnumValues, s) {
+				return s, nil
+			}
+			return nil, fmt.Errorf("value %q is not an allowed enum value", s)
+		}
+		f, err := toFloat(raw)
+		if err != nil {
+			return nil, fmt.Errorf("enum value %v is not an index", raw)
+		}
+		idx := int(math.Round(f))
+		if idx < 0 || idx >= len(p.EnumValues) {
+			return nil, fmt.Errorf("enum index %d out of range", idx)
+		}
+		return p.EnumValues[idx], nil
+	case TypeFloatArray:
+		return toFloatArray(raw)
+	default:
+		return raw, nil
+	}
+}

internal/confmgr/snapshot_test.go

@@ -0,0 +1,83 @@
+package confmgr
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestSnapshotCapturesAndCoerces(t *testing.T) {
+	set := ConfigSet{
+		ID:   "set1",
+		Name: "s",
+		Parameters: []Parameter{
+			{Key: "v", DS: "epics", Signal: "PSU:V", Type: TypeFloat},
+			{Key: "n", DS: "epics", Signal: "PSU:N", Type: TypeInt},
+			{Key: "en", DS: "epics", Signal: "PSU:EN", Type: TypeBool},
+			{Key: "mode", DS: "epics", Signal: "PSU:MODE", Type: TypeEnum, EnumValues: []string{"off", "low", "high"}},
+			{Key: "wf", DS: "epics", Signal: "PSU:WF", Type: TypeFloatArray},
+			{Key: "lbl", DS: "epics", Signal: "PSU:LBL", Type: TypeString},
+		},
+	}
+	live := map[string]any{
+		"PSU:V":    24.5,
+		"PSU:N":    3.0,         // float reading → coerced to int64
+		"PSU:EN":   int64(1),    // numeric → bool true
+		"PSU:MODE": int64(2),    // enum index → "high"
+		"PSU:WF":   []float64{1, 2, 3},
+		"PSU:LBL":  "ready",
+	}
+	res := Snapshot(set, func(_, signal string) (any, error) {
+		v, ok := live[signal]
+		if !ok {
+			return nil, errors.New("not read")
+		}
+		return v, nil
+	})
+
+	if res.Captured != 6 || res.Failed != 0 {
+		t.Fatalf("summary: captured=%d failed=%d", res.Captured, res.Failed)
+	}
+	if res.Values["v"] != 24.5 {
+		t.Errorf("v = %v, want 24.5", res.Values["v"])
+	}
+	if res.Values["n"] != int64(3) {
+		t.Errorf("n = %v (%T), want int64(3)", res.Values["n"], res.Values["n"])
+	}
+	if res.Values["en"] != true {
+		t.Errorf("en = %v, want true", res.Values["en"])
+	}
+	if res.Values["mode"] != "high" {
+		t.Errorf("mode = %v, want high", res.Values["mode"])
+	}
+	if res.Values["lbl"] != "ready" {
+		t.Errorf("lbl = %v, want ready", res.Values["lbl"])
+	}
+	// The captured values must validate against the set.
+	inst := ConfigInstance{SetID: set.ID, Values: res.Values}
+	if err := inst.ValidateAgainst(set); err != nil {
+		t.Errorf("snapshot values fail validation: %v", err)
+	}
+}
+
+func TestSnapshotReadFailureRecorded(t *testing.T) {
+	set := ConfigSet{
+		ID:   "set1",
+		Name: "s",
+		Parameters: []Parameter{
+			{Key: "a", DS: "epics", Signal: "A", Type: TypeFloat},
+			{Key: "b", DS: "epics", Signal: "B", Type: TypeFloat},
+		},
+	}
+	res := Snapshot(set, func(_, signal string) (any, error) {
+		if signal == "B" {
+			return nil, errors.New("offline")
+		}
+		return 1.0, nil
+	})
+	if res.Captured != 1 || res.Failed != 1 {
+		t.Fatalf("summary: captured=%d failed=%d", res.Captured, res.Failed)
+	}
+	if _, ok := res.Values["b"]; ok {
+		t.Errorf("failed parameter must not appear in values")
+	}
+}

internal/confmgr/store.go

@@ -0,0 +1,684 @@
+package confmgr
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+	"unicode"
+)
+
+// ErrNotFound is returned when the requested set or instance does not exist.
+var ErrNotFound = errors.New("config object not found")
+
+// Kind selects which collection a store operation targets.
+type Kind int
+
+const (
+	KindSet Kind = iota
+	KindInstance
+	KindRule
+)
+
+func (k Kind) sub() string {
+	switch k {
+	case KindInstance:
+		return "instances"
+	case KindRule:
+		return "rules"
+	default:
+		return "sets"
+	}
+}
+
+// Meta is the lightweight listing representation.
+type Meta struct {
+	ID      string `json:"id"`
+	Name    string `json:"name"`
+	Version int    `json:"version"`
+	// SetID is only populated for instances (the schema they belong to); it is
+	// empty for sets. Lets clients group/filter instances by set without a GET
+	// per instance.
+	SetID string `json:"setId,omitempty"`
+}
+
+// VersionMeta describes a single persisted revision.
+type VersionMeta struct {
+	Version int       `json:"version"`
+	Name    string    `json:"name"`
+	Tag     string    `json:"tag,omitempty"`
+	Current bool      `json:"current"`
+	SavedAt time.Time `json:"savedAt"`
+}
+
+// Store persists configuration sets and instances as versioned JSON files
+// under {storageDir}/configs/{sets,instances}/. Each object lives in
+// {id}.json with prior revisions preserved as {id}.v{N}.json backups, exactly
+// mirroring the panel storage versioning scheme.
+type Store struct {
+	rootDir string
+	dirs    map[Kind]string
+}
+
+// New opens (and creates, if needed) the configs storage directories.
+func New(storageDir string) (*Store, error) {
+	s := &Store{rootDir: storageDir, dirs: map[Kind]string{}}
+	for _, k := range []Kind{KindSet, KindInstance, KindRule} {
+		dir := filepath.Join(storageDir, "configs", k.sub())
+		if err := os.MkdirAll(dir, 0o755); err != nil {
+			return nil, fmt.Errorf("create %s dir: %w", k.sub(), err)
+		}
+		s.dirs[k] = dir
+	}
+	return s, nil
+}
+
+// header parses the metadata fields shared by sets and instances.
+type header struct {
+	ID      string `json:"id"`
+	Name    string `json:"name"`
+	Version int    `json:"version"`
+	Tag     string `json:"tag"`
+	SetID   string `json:"setId"`
+}
+
+func validateID(id string) error {
+	if id == "" {
+		return fmt.Errorf("config ID must not be empty")
+	}
+	for _, r := range id {
+		if !unicode.IsLetter(r) && !unicode.IsDigit(r) && r != '-' && r != '_' {
+			return fmt.Errorf("invalid character %q in config ID", r)
+		}
+	}
+	return nil
+}
+
+func (s *Store) filePath(k Kind, id string) string {
+	return filepath.Join(s.dirs[k], id+".json")
+}
+
+func (s *Store) backupPath(k Kind, id string, version int) string {
+	return filepath.Join(s.dirs[k], fmt.Sprintf("%s.v%d.json", id, version))
+}
+
+// isVersioned reports whether name matches <id>.v<number>.json.
+func isVersioned(name string) bool {
+	parts := strings.Split(name, ".")
+	if len(parts) != 3 || parts[2] != "json" {
+		return false
+	}
+	if !strings.HasPrefix(parts[1], "v") {
+		return false
+	}
+	_, err := strconv.Atoi(parts[1][1:])
+	return err == nil
+}
+
+func readHeader(data []byte) (header, error) {
+	var h header
+	if err := json.Unmarshal(data, &h); err != nil {
+		return header{}, err
+	}
+	return h, nil
+}
+
+// List returns metadata for every stored object of the given kind.
+func (s *Store) List(k Kind) ([]Meta, error) {
+	entries, err := os.ReadDir(s.dirs[k])
+	if err != nil {
+		return nil, err
+	}
+	out := []Meta{}
+	for _, e := range entries {
+		name := e.Name()
+		if e.IsDir() || !strings.HasSuffix(name, ".json") || isVersioned(name) {
+			continue
+		}
+		id := strings.TrimSuffix(name, ".json")
+		data, err := os.ReadFile(s.filePath(k, id))
+		if err != nil {
+			continue
+		}
+		h, err := readHeader(data)
+		if err != nil {
+			continue
+		}
+		out = append(out, Meta{ID: id, Name: h.Name, Version: h.Version, SetID: h.SetID})
+	}
+	return out, nil
+}
+
+// get returns the raw JSON bytes for the current revision.
+func (s *Store) get(k Kind, id string) ([]byte, error) {
+	if err := validateID(id); err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrNotFound, err)
+	}
+	data, err := os.ReadFile(s.filePath(k, id))
+	if errors.Is(err, os.ErrNotExist) {
+		return nil, ErrNotFound
+	}
+	return data, err
+}
+
+// create writes a new object, deriving a unique ID from name when obj has none,
+// stamping version=1 and the given tag. It returns the raw stored bytes.
+func (s *Store) create(k Kind, obj map[string]any, tag string) (string, []byte, error) {
+	id, _ := obj["id"].(string)
+	if id == "" {
+		id = slugify(name(obj))
+	}
+	if err := validateID(id); err != nil {
+		return "", nil, err
+	}
+	if _, err := os.Stat(s.filePath(k, id)); err == nil {
+		id = id + "-" + strconv.FormatInt(time.Now().UnixMilli(), 10)
+	}
+	obj["id"] = id
+	obj["version"] = 1
+	if tag != "" {
+		obj["tag"] = tag
+	}
+	data, err := marshal(obj)
+	if err != nil {
+		return "", nil, err
+	}
+	return id, data, os.WriteFile(s.filePath(k, id), data, 0o644)
+}
+
+// update replaces the current revision, preserving the prior one as a backup
+// and incrementing the version. It returns the raw stored bytes.
+func (s *Store) update(k Kind, id string, obj map[string]any, tag string) ([]byte, error) {
+	if err := validateID(id); err != nil {
+		return nil, ErrNotFound
+	}
+	oldData, err := os.ReadFile(s.filePath(k, id))
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+	oldHdr, err := readHeader(oldData)
+	if err != nil {
+		return nil, fmt.Errorf("parse existing JSON: %w", err)
+	}
+	if oldHdr.Version < 1 {
+		oldHdr.Version = 1
+	}
+	if err := os.WriteFile(s.backupPath(k, id, oldHdr.Version), oldData, 0o644); err != nil {
+		return nil, fmt.Errorf("create backup: %w", err)
+	}
+	obj["id"] = id
+	obj["version"] = oldHdr.Version + 1
+	if tag != "" {
+		obj["tag"] = tag
+	}
+	data, err := marshal(obj)
+	if err != nil {
+		return nil, err
+	}
+	return data, os.WriteFile(s.filePath(k, id), data, 0o644)
+}
+
+// Versions returns metadata for every persisted revision, newest-first.
+func (s *Store) Versions(k Kind, id string) ([]VersionMeta, error) {
+	if err := validateID(id); err != nil {
+		return nil, ErrNotFound
+	}
+	curInfo, err := os.Stat(s.filePath(k, id))
+	if errors.Is(err, os.ErrNotExist) {
+		return nil, ErrNotFound
+	} else if err != nil {
+		return nil, err
+	}
+	curData, err := os.ReadFile(s.filePath(k, id))
+	if err != nil {
+		return nil, err
+	}
+	curHdr, err := readHeader(curData)
+	if err != nil {
+		return nil, err
+	}
+	out := []VersionMeta{{
+		Version: curHdr.Version,
+		Name:    curHdr.Name,
+		Tag:     curHdr.Tag,
+		Current: true,
+		SavedAt: curInfo.ModTime(),
+	}}
+
+	entries, err := os.ReadDir(s.dirs[k])
+	if err != nil {
+		return nil, err
+	}
+	prefix := id + ".v"
+	for _, e := range entries {
+		name := e.Name()
+		if e.IsDir() || !strings.HasPrefix(name, prefix) || !isVersioned(name) {
+			continue
+		}
+		info, err := e.Info()
+		if err != nil {
+			continue
+		}
+		data, err := os.ReadFile(filepath.Join(s.dirs[k], name))
+		if err != nil {
+			continue
+		}
+		h, err := readHeader(data)
+		if err != nil {
+			continue
+		}
+		out = append(out, VersionMeta{
+			Version: h.Version,
+			Name:    h.Name,
+			Tag:     h.Tag,
+			SavedAt: info.ModTime(),
+		})
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Version > out[j].Version })
+	return out, nil
+}
+
+// getVersion returns the raw JSON bytes for a specific revision.
+func (s *Store) getVersion(k Kind, id string, version int) ([]byte, error) {
+	if err := validateID(id); err != nil {
+		return nil, ErrNotFound
+	}
+	curData, err := os.ReadFile(s.filePath(k, id))
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+	if h, err := readHeader(curData); err == nil && h.Version == version {
+		return curData, nil
+	}
+	data, err := os.ReadFile(s.backupPath(k, id, version))
+	if errors.Is(err, os.ErrNotExist) {
+		return nil, ErrNotFound
+	}
+	return data, err
+}
+
+// Promote re-saves a past revision as a new revision on top of history.
+func (s *Store) Promote(k Kind, id string, version int) error {
+	data, err := s.getVersion(k, id, version)
+	if err != nil {
+		return err
+	}
+	obj, err := unmarshal(data)
+	if err != nil {
+		return err
+	}
+	_, err = s.update(k, id, obj, fmt.Sprintf("restored from v%d", version))
+	return err
+}
+
+// Fork creates a brand-new object from a revision, with a fresh ID and version 1.
+func (s *Store) Fork(k Kind, id string, version int) (string, error) {
+	data, err := s.getVersion(k, id, version)
+	if err != nil {
+		return "", err
+	}
+	obj, err := unmarshal(data)
+	if err != nil {
+		return "", err
+	}
+	newID := id + "-fork-" + strconv.FormatInt(time.Now().UnixMilli(), 10)
+	obj["id"] = newID
+	obj["version"] = 1
+	delete(obj, "tag")
+	out, err := marshal(obj)
+	if err != nil {
+		return "", err
+	}
+	return newID, os.WriteFile(s.filePath(k, newID), out, 0o644)
+}
+
+// Delete moves an object and all its backups to a timestamped trash folder so
+// it can be recovered. Nothing is destroyed.
+func (s *Store) Delete(k Kind, id string) error {
+	if err := validateID(id); err != nil {
+		return ErrNotFound
+	}
+	if _, err := os.Stat(s.filePath(k, id)); err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return ErrNotFound
+		}
+		return err
+	}
+	trashDir := filepath.Join(s.rootDir, "trash", "configs", k.sub(), fmt.Sprintf("%s.%d", id, time.Now().UnixMilli()))
+	if err := os.MkdirAll(trashDir, 0o755); err != nil {
+		return fmt.Errorf("create trash dir: %w", err)
+	}
+	entries, err := os.ReadDir(s.dirs[k])
+	if err != nil {
+		return err
+	}
+	for _, e := range entries {
+		name := e.Name()
+		if e.IsDir() {
+			continue
+		}
+		if name == id+".json" || (strings.HasPrefix(name, id+".v") && isVersioned(name)) {
+			if err := os.Rename(filepath.Join(s.dirs[k], name), filepath.Join(trashDir, name)); err != nil {
+				return fmt.Errorf("move %s to trash: %w", name, err)
+			}
+		}
+	}
+	return nil
+}
+
+// ── typed wrappers ──────────────────────────────────────────────────────────
+
+// GetSet returns the current revision of a config set.
+func (s *Store) GetSet(id string) (ConfigSet, error) {
+	data, err := s.get(KindSet, id)
+	if err != nil {
+		return ConfigSet{}, err
+	}
+	var set ConfigSet
+	return set, json.Unmarshal(data, &set)
+}
+
+// GetSetVersion returns a specific revision of a config set.
+func (s *Store) GetSetVersion(id string, version int) (ConfigSet, error) {
+	data, err := s.getVersion(KindSet, id, version)
+	if err != nil {
+		return ConfigSet{}, err
+	}
+	var set ConfigSet
+	return set, json.Unmarshal(data, &set)
+}
+
+// CreateSet validates and stores a new config set, returning it with its
+// assigned ID and version.
+func (s *Store) CreateSet(set ConfigSet, tag string) (ConfigSet, error) {
+	if err := set.Validate(); err != nil {
+		return ConfigSet{}, err
+	}
+	obj, err := toMap(set)
+	if err != nil {
+		return ConfigSet{}, err
+	}
+	_, data, err := s.create(KindSet, obj, tag)
+	if err != nil {
+		return ConfigSet{}, err
+	}
+	var out ConfigSet
+	return out, json.Unmarshal(data, &out)
+}
+
+// UpdateSet validates and stores a new revision of an existing config set.
+func (s *Store) UpdateSet(id string, set ConfigSet, tag string) (ConfigSet, error) {
+	if err := set.Validate(); err != nil {
+		return ConfigSet{}, err
+	}
+	obj, err := toMap(set)
+	if err != nil {
+		return ConfigSet{}, err
+	}
+	data, err := s.update(KindSet, id, obj, tag)
+	if err != nil {
+		return ConfigSet{}, err
+	}
+	var out ConfigSet
+	return out, json.Unmarshal(data, &out)
+}
+
+// GetInstance returns the current revision of a config instance.
+func (s *Store) GetInstance(id string) (ConfigInstance, error) {
+	data, err := s.get(KindInstance, id)
+	if err != nil {
+		return ConfigInstance{}, err
+	}
+	var inst ConfigInstance
+	return inst, json.Unmarshal(data, &inst)
+}
+
+// GetInstanceVersion returns a specific revision of a config instance.
+func (s *Store) GetInstanceVersion(id string, version int) (ConfigInstance, error) {
+	data, err := s.getVersion(KindInstance, id, version)
+	if err != nil {
+		return ConfigInstance{}, err
+	}
+	var inst ConfigInstance
+	return inst, json.Unmarshal(data, &inst)
+}
+
+// setForInstance loads the schema an instance is bound to, honouring a pinned
+// SetVersion when set.
+func (s *Store) setForInstance(inst ConfigInstance) (ConfigSet, error) {
+	if inst.SetVersion > 0 {
+		return s.GetSetVersion(inst.SetID, inst.SetVersion)
+	}
+	return s.GetSet(inst.SetID)
+}
+
+// CreateInstance validates an instance against its set and stores it.
+func (s *Store) CreateInstance(inst ConfigInstance, tag string) (ConfigInstance, error) {
+	set, err := s.setForInstance(inst)
+	if err != nil {
+		return ConfigInstance{}, fmt.Errorf("load set %q: %w", inst.SetID, err)
+	}
+	if err := inst.ValidateAgainst(set); err != nil {
+		return ConfigInstance{}, err
+	}
+	if err := s.applyRules(&inst, set); err != nil {
+		return ConfigInstance{}, err
+	}
+	obj, err := toMap(inst)
+	if err != nil {
+		return ConfigInstance{}, err
+	}
+	_, data, err := s.create(KindInstance, obj, tag)
+	if err != nil {
+		return ConfigInstance{}, err
+	}
+	var out ConfigInstance
+	return out, json.Unmarshal(data, &out)
+}
+
+// UpdateInstance validates and stores a new revision of an existing instance.
+func (s *Store) UpdateInstance(id string, inst ConfigInstance, tag string) (ConfigInstance, error) {
+	set, err := s.setForInstance(inst)
+	if err != nil {
+		return ConfigInstance{}, fmt.Errorf("load set %q: %w", inst.SetID, err)
+	}
+	if err := inst.ValidateAgainst(set); err != nil {
+		return ConfigInstance{}, err
+	}
+	if err := s.applyRules(&inst, set); err != nil {
+		return ConfigInstance{}, err
+	}
+	obj, err := toMap(inst)
+	if err != nil {
+		return ConfigInstance{}, err
+	}
+	data, err := s.update(KindInstance, id, obj, tag)
+	if err != nil {
+		return ConfigInstance{}, err
+	}
+	var out ConfigInstance
+	return out, json.Unmarshal(data, &out)
+}
+
+// SetForInstance is the exported loader used by apply/diff callers.
+func (s *Store) SetForInstance(inst ConfigInstance) (ConfigSet, error) {
+	return s.setForInstance(inst)
+}
+
+// ── rules ────────────────────────────────────────────────────────────────────
+
+// GetRule returns the current revision of a CUE validation/transformation rule.
+func (s *Store) GetRule(id string) (ConfigRule, error) {
+	data, err := s.get(KindRule, id)
+	if err != nil {
+		return ConfigRule{}, err
+	}
+	var rule ConfigRule
+	return rule, json.Unmarshal(data, &rule)
+}
+
+// GetRuleVersion returns a specific revision of a rule.
+func (s *Store) GetRuleVersion(id string, version int) (ConfigRule, error) {
+	data, err := s.getVersion(KindRule, id, version)
+	if err != nil {
+		return ConfigRule{}, err
+	}
+	var rule ConfigRule
+	return rule, json.Unmarshal(data, &rule)
+}
+
+// CreateRule validates the rule's CUE source and stores it.
+func (s *Store) CreateRule(rule ConfigRule, tag string) (ConfigRule, error) {
+	if err := rule.Validate(); err != nil {
+		return ConfigRule{}, err
+	}
+	obj, err := toMap(rule)
+	if err != nil {
+		return ConfigRule{}, err
+	}
+	_, data, err := s.create(KindRule, obj, tag)
+	if err != nil {
+		return ConfigRule{}, err
+	}
+	var out ConfigRule
+	return out, json.Unmarshal(data, &out)
+}
+
+// UpdateRule validates and stores a new revision of an existing rule.
+func (s *Store) UpdateRule(id string, rule ConfigRule, tag string) (ConfigRule, error) {
+	if err := rule.Validate(); err != nil {
+		return ConfigRule{}, err
+	}
+	obj, err := toMap(rule)
+	if err != nil {
+		return ConfigRule{}, err
+	}
+	data, err := s.update(KindRule, id, obj, tag)
+	if err != nil {
+		return ConfigRule{}, err
+	}
+	var out ConfigRule
+	return out, json.Unmarshal(data, &out)
+}
+
+// rulesForSet loads every current-revision rule bound to the given set.
+func (s *Store) rulesForSet(setID string) ([]ConfigRule, error) {
+	metas, err := s.List(KindRule)
+	if err != nil {
+		return nil, err
+	}
+	var out []ConfigRule
+	for _, m := range metas {
+		if m.SetID != setID {
+			continue
+		}
+		rule, err := s.GetRule(m.ID)
+		if err != nil {
+			continue
+		}
+		out = append(out, rule)
+	}
+	return out, nil
+}
+
+// applyRules runs every rule bound to inst's set against its values. On
+// success it merges rule-derived values back into inst (parameter keys only) so
+// the stored instance reflects the canonical, transformed configuration. A
+// violation is returned as *RuleError so the caller can surface the structured
+// details.
+func (s *Store) applyRules(inst *ConfigInstance, set ConfigSet) error {
+	rules, err := s.rulesForSet(inst.SetID)
+	if err != nil {
+		return err
+	}
+	if len(rules) == 0 {
+		return nil
+	}
+	res := evaluateRules(rules, inst.Values)
+	if !res.OK {
+		return &RuleError{Result: res}
+	}
+	for k, v := range res.Transformed {
+		if _, ok := set.param(k); ok {
+			if inst.Values == nil {
+				inst.Values = map[string]any{}
+			}
+			inst.Values[k] = v
+		}
+	}
+	return nil
+}
+
+// ValidateInstanceRules evaluates the stored rules for an instance without
+// persisting anything. It is the read-only counterpart used by the validate
+// endpoint.
+func (s *Store) ValidateInstanceRules(inst ConfigInstance) (RuleResult, error) {
+	rules, err := s.rulesForSet(inst.SetID)
+	if err != nil {
+		return RuleResult{}, err
+	}
+	if len(rules) == 0 {
+		return RuleResult{OK: true}, nil
+	}
+	return evaluateRules(rules, inst.Values), nil
+}
+
+// ── JSON helpers ────────────────────────────────────────────────────────────
+
+func name(obj map[string]any) string {
+	n, _ := obj["name"].(string)
+	return n
+}
+
+func marshal(obj map[string]any) ([]byte, error) {
+	return json.MarshalIndent(obj, "", "  ")
+}
+
+func unmarshal(data []byte) (map[string]any, error) {
+	var obj map[string]any
+	if err := json.Unmarshal(data, &obj); err != nil {
+		return nil, err
+	}
+	return obj, nil
+}
+
+// toMap round-trips a typed value through JSON into a generic map so the store
+// can stamp id/version/tag without knowing the concrete type.
+func toMap(v any) (map[string]any, error) {
+	data, err := json.Marshal(v)
+	if err != nil {
+		return nil, err
+	}
+	return unmarshal(data)
+}
+
+// slugify converts a human-readable name into a URL-safe identifier.
+func slugify(s string) string {
+	var b strings.Builder
+	for _, r := range strings.ToLower(s) {
+		switch {
+		case r >= 'a' && r <= 'z', r >= '0' && r <= '9':
+			b.WriteRune(r)
+		default:
+			if b.Len() > 0 && b.String()[b.Len()-1] != '-' {
+				b.WriteByte('-')
+			}
+		}
+	}
+	result := strings.Trim(b.String(), "-")
+	if result == "" {
+		return "config"
+	}
+	return result
+}

internal/confmgr/store_test.go

@@ -0,0 +1,270 @@
+package confmgr
+
+import (
+	"testing"
+)
+
+func fptr(f float64) *float64 { return &f }
+
+func sampleSet() ConfigSet {
+	return ConfigSet{
+		Name:        "PSU",
+		Description: "power supply config",
+		Parameters: []Parameter{
+			{Key: "voltage", DS: "epics", Signal: "PSU:V", Type: TypeFloat, Default: 12.0, Mandatory: true, Min: fptr(0), Max: fptr(48)},
+			{Key: "enabled", DS: "epics", Signal: "PSU:EN", Type: TypeBool, Default: false},
+		},
+	}
+}
+
+func TestCreateAndGetSet(t *testing.T) {
+	s, err := New(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := s.CreateSet(sampleSet(), "initial")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out.ID == "" {
+		t.Fatal("expected generated ID")
+	}
+	if out.Version != 1 {
+		t.Errorf("version: want 1, got %d", out.Version)
+	}
+	got, err := s.GetSet(out.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Name != "PSU" || len(got.Parameters) != 2 {
+		t.Errorf("round-trip mismatch: %+v", got)
+	}
+}
+
+func TestRuleBlocksInvalidInstance(t *testing.T) {
+	s, _ := New(t.TempDir())
+	set, _ := s.CreateSet(sampleSet(), "")
+	if _, err := s.CreateRule(ConfigRule{
+		Name:   "voltage cap",
+		SetID:  set.ID,
+		Source: "voltage: <=24",
+	}, ""); err != nil {
+		t.Fatal(err)
+	}
+
+	// In-range value passes.
+	if _, err := s.CreateInstance(ConfigInstance{
+		Name: "ok", SetID: set.ID, Values: map[string]any{"voltage": 20.0},
+	}, ""); err != nil {
+		t.Fatalf("expected in-range instance to save, got %v", err)
+	}
+
+	// Out-of-range value is rejected by the rule.
+	_, err := s.CreateInstance(ConfigInstance{
+		Name: "bad", SetID: set.ID, Values: map[string]any{"voltage": 40.0},
+	}, "")
+	if err == nil {
+		t.Fatalf("expected rule violation to block save")
+	}
+	var re *RuleError
+	if !asRuleError(err, &re) {
+		t.Fatalf("expected *RuleError, got %T: %v", err, err)
+	}
+}
+
+func TestRuleTransformPersists(t *testing.T) {
+	s, _ := New(t.TempDir())
+	set := sampleSet()
+	max := 48.0
+	set.Parameters = append(set.Parameters, Parameter{Key: "vmax", DS: "epics", Signal: "PSU:VMAX", Type: TypeFloat, Min: &max})
+	created, _ := s.CreateSet(set, "")
+	// Rule derives vmax = voltage * 2 (within range for voltage=20 -> 40).
+	if _, err := s.CreateRule(ConfigRule{
+		Name: "vmax derive", SetID: created.ID, Source: "voltage: number\nvmax: voltage * 2",
+	}, ""); err != nil {
+		t.Fatal(err)
+	}
+	inst, err := s.CreateInstance(ConfigInstance{
+		Name: "x", SetID: created.ID, Values: map[string]any{"voltage": 20.0},
+	}, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if f, _ := toFloat(inst.Values["vmax"]); f != 40 {
+		t.Fatalf("expected derived vmax=40 to persist, got %v", inst.Values["vmax"])
+	}
+}
+
+func asRuleError(err error, target **RuleError) bool {
+	for err != nil {
+		if re, ok := err.(*RuleError); ok {
+			*target = re
+			return true
+		}
+		type unwrapper interface{ Unwrap() error }
+		u, ok := err.(unwrapper)
+		if !ok {
+			return false
+		}
+		err = u.Unwrap()
+	}
+	return false
+}
+
+func TestSetVersioning(t *testing.T) {
+	s, _ := New(t.TempDir())
+	created, _ := s.CreateSet(sampleSet(), "")
+	id := created.ID
+
+	// Update -> v2.
+	upd := sampleSet()
+	upd.Description = "edited"
+	v2, err := s.UpdateSet(id, upd, "edit")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if v2.Version != 2 {
+		t.Fatalf("version after update: want 2, got %d", v2.Version)
+	}
+
+	versions, err := s.Versions(KindSet, id)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(versions) != 2 {
+		t.Fatalf("want 2 versions, got %d", len(versions))
+	}
+	if !versions[0].Current || versions[0].Version != 2 {
+		t.Errorf("newest should be current v2: %+v", versions[0])
+	}
+
+	// Old version still retrievable.
+	old, err := s.GetSetVersion(id, 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if old.Description != "power supply config" {
+		t.Errorf("v1 description changed: %q", old.Description)
+	}
+
+	// Promote v1 -> becomes v3 with original content.
+	if err := s.Promote(KindSet, id, 1); err != nil {
+		t.Fatal(err)
+	}
+	cur, _ := s.GetSet(id)
+	if cur.Version != 3 || cur.Description != "power supply config" {
+		t.Errorf("after promote: want v3 original desc, got v%d %q", cur.Version, cur.Description)
+	}
+}
+
+func TestForkSet(t *testing.T) {
+	s, _ := New(t.TempDir())
+	created, _ := s.CreateSet(sampleSet(), "")
+	_, _ = s.UpdateSet(created.ID, sampleSet(), "")
+
+	newID, err := s.Fork(KindSet, created.ID, 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	forked, err := s.GetSet(newID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if forked.ID == created.ID {
+		t.Error("fork should have a new ID")
+	}
+	if forked.Version != 1 {
+		t.Errorf("fork version: want 1, got %d", forked.Version)
+	}
+	if forked.Tag != "" {
+		t.Errorf("fork tag should be cleared, got %q", forked.Tag)
+	}
+}
+
+func TestDeleteSetSoftDeletes(t *testing.T) {
+	s, _ := New(t.TempDir())
+	created, _ := s.CreateSet(sampleSet(), "")
+	if err := s.Delete(KindSet, created.ID); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := s.GetSet(created.ID); err == nil {
+		t.Error("expected set to be gone after delete")
+	}
+	// Deleting again is a not-found.
+	if err := s.Delete(KindSet, created.ID); err != ErrNotFound {
+		t.Errorf("want ErrNotFound, got %v", err)
+	}
+}
+
+func TestSetValidation(t *testing.T) {
+	s, _ := New(t.TempDir())
+	bad := ConfigSet{Name: "", Parameters: nil}
+	if _, err := s.CreateSet(bad, ""); err == nil {
+		t.Error("expected empty-name validation error")
+	}
+	dup := ConfigSet{Name: "x", Parameters: []Parameter{
+		{Key: "a", DS: "d", Signal: "s", Type: TypeFloat},
+		{Key: "a", DS: "d", Signal: "s2", Type: TypeFloat},
+	}}
+	if _, err := s.CreateSet(dup, ""); err == nil {
+		t.Error("expected duplicate-key validation error")
+	}
+	defaultOOR := ConfigSet{Name: "x", Parameters: []Parameter{
+		{Key: "a", DS: "d", Signal: "s", Type: TypeFloat, Default: 100.0, Max: fptr(10)},
+	}}
+	if _, err := s.CreateSet(defaultOOR, ""); err == nil {
+		t.Error("expected out-of-range default validation error")
+	}
+}
+
+func TestInstanceLifecycle(t *testing.T) {
+	s, _ := New(t.TempDir())
+	set, _ := s.CreateSet(sampleSet(), "")
+
+	inst := ConfigInstance{
+		Name:   "nominal",
+		SetID:  set.ID,
+		Values: map[string]any{"voltage": 24.0, "enabled": true},
+	}
+	out, err := s.CreateInstance(inst, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out.Version != 1 {
+		t.Errorf("instance version: want 1, got %d", out.Version)
+	}
+
+	// Update value -> v2.
+	out.Values["voltage"] = 36.0
+	v2, err := s.UpdateInstance(out.ID, out, "bump")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if v2.Version != 2 {
+		t.Errorf("instance version after update: want 2, got %d", v2.Version)
+	}
+}
+
+func TestInstanceValidation(t *testing.T) {
+	s, _ := New(t.TempDir())
+	set, _ := s.CreateSet(sampleSet(), "")
+
+	// voltage is mandatory with a default, so omitting it is OK; but an
+	// out-of-range value must fail.
+	bad := ConfigInstance{Name: "x", SetID: set.ID, Values: map[string]any{"voltage": 999.0}}
+	if _, err := s.CreateInstance(bad, ""); err == nil {
+		t.Error("expected out-of-range value error")
+	}
+
+	// Unknown parameter key must fail.
+	unknown := ConfigInstance{Name: "x", SetID: set.ID, Values: map[string]any{"nope": 1.0}}
+	if _, err := s.CreateInstance(unknown, ""); err == nil {
+		t.Error("expected unknown-parameter error")
+	}
+
+	// Unknown set must fail.
+	missing := ConfigInstance{Name: "x", SetID: "does-not-exist", Values: map[string]any{}}
+	if _, err := s.CreateInstance(missing, ""); err == nil {
+		t.Error("expected missing-set error")
+	}
+}

internal/controllogic/config_node_test.go

@@ -0,0 +1,234 @@
+package controllogic
+
+import (
+	"context"
+	"io"
+	"log/slog"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/uopi/uopi/internal/audit"
+	"github.com/uopi/uopi/internal/broker"
+	"github.com/uopi/uopi/internal/confmgr"
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+// writableSource is a minimal in-memory DataSource that records the last value
+// written to each signal, so config-apply/read nodes can be tested end-to-end.
+type writableSource struct {
+	mu      sync.Mutex
+	written map[string]any
+}
+
+func newWritableSource() *writableSource { return &writableSource{written: map[string]any{}} }
+
+func (s *writableSource) Name() string                          { return "tgt" }
+func (s *writableSource) Connect(context.Context) error         { return nil }
+func (s *writableSource) ListSignals(context.Context) ([]datasource.Metadata, error) {
+	return nil, nil
+}
+func (s *writableSource) GetMetadata(_ context.Context, sig string) (datasource.Metadata, error) {
+	return datasource.Metadata{Name: sig, Writable: true}, nil
+}
+// Subscribe delivers the signal's last-written value once (if any), so a
+// one-shot ReadNow (used by config snapshot) resolves immediately.
+func (s *writableSource) Subscribe(_ context.Context, sig string, ch chan<- datasource.Value) (datasource.CancelFunc, error) {
+	s.mu.Lock()
+	v, ok := s.written[sig]
+	s.mu.Unlock()
+	if ok {
+		select {
+		case ch <- datasource.Value{Data: v, Timestamp: time.Now()}:
+		default:
+		}
+	}
+	return func() {}, nil
+}
+func (s *writableSource) Write(_ context.Context, signal string, value any) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.written[signal] = value
+	return nil
+}
+func (s *writableSource) History(context.Context, string, time.Time, time.Time, int) ([]datasource.Value, error) {
+	return nil, datasource.ErrHistoryUnavailable
+}
+
+func (s *writableSource) get(signal string) (any, bool) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	v, ok := s.written[signal]
+	return v, ok
+}
+
+// setupConfigEngine wires a broker (with a writable "tgt" source), a confmgr
+// store seeded with a set + instance, and an Engine bound to both.
+func setupConfigEngine(t *testing.T) (*Engine, *writableSource, string) {
+	t.Helper()
+	log := slog.New(slog.NewTextHandler(io.Discard, nil))
+	ctx := context.Background()
+
+	src := newWritableSource()
+	brk := broker.New(ctx, log)
+	brk.Register(src)
+
+	cfg, err := confmgr.New(t.TempDir())
+	if err != nil {
+		t.Fatal("confmgr.New:", err)
+	}
+	set, err := cfg.CreateSet(confmgr.ConfigSet{
+		Name: "tuning",
+		Parameters: []confmgr.Parameter{
+			{Key: "gain", DS: "tgt", Signal: "GAIN", Type: confmgr.TypeFloat, Default: 1.0},
+			{Key: "offset", DS: "tgt", Signal: "OFFSET", Type: confmgr.TypeFloat, Default: 0.0},
+		},
+	}, "")
+	if err != nil {
+		t.Fatal("CreateSet:", err)
+	}
+	inst, err := cfg.CreateInstance(confmgr.ConfigInstance{
+		Name:   "warm",
+		SetID:  set.ID,
+		Values: map[string]any{"gain": 2.5, "offset": 10.0},
+	}, "")
+	if err != nil {
+		t.Fatal("CreateInstance:", err)
+	}
+
+	e := NewEngine(ctx, brk, nil, cfg, audit.Nop(), log)
+	return e, src, inst.ID
+}
+
+func TestApplyConfigWritesEveryParam(t *testing.T) {
+	e, src, instID := setupConfigEngine(t)
+	cg := &compiledGraph{name: "flow", engine: e, locals: map[string]float64{}}
+
+	e.applyConfig(cg, instID)
+
+	if got, ok := src.get("GAIN"); !ok || toNum(got) != 2.5 {
+		t.Errorf("GAIN = %v (ok=%v), want 2.5", got, ok)
+	}
+	if got, ok := src.get("OFFSET"); !ok || toNum(got) != 10.0 {
+		t.Errorf("OFFSET = %v (ok=%v), want 10.0", got, ok)
+	}
+}
+
+func TestApplyConfigUnknownInstanceNoop(t *testing.T) {
+	e, src, _ := setupConfigEngine(t)
+	cg := &compiledGraph{name: "flow", engine: e, locals: map[string]float64{}}
+
+	e.applyConfig(cg, "does-not-exist")
+
+	if len(src.written) != 0 {
+		t.Errorf("expected no writes, got %v", src.written)
+	}
+}
+
+func TestReadConfigParam(t *testing.T) {
+	e, _, instID := setupConfigEngine(t)
+
+	if v, ok := e.readConfigParam(instID, "gain"); !ok || v != 2.5 {
+		t.Errorf("readConfigParam(gain) = %v (ok=%v), want 2.5", v, ok)
+	}
+	// Missing param key.
+	if _, ok := e.readConfigParam(instID, "nope"); ok {
+		t.Errorf("readConfigParam(nope) returned ok=true, want false")
+	}
+	// Missing instance.
+	if _, ok := e.readConfigParam("does-not-exist", "gain"); ok {
+		t.Errorf("readConfigParam(missing instance) returned ok=true, want false")
+	}
+}
+
+func TestWriteConfigParam(t *testing.T) {
+	e, _, instID := setupConfigEngine(t)
+	cg := &compiledGraph{name: "flow", engine: e, locals: map[string]float64{}}
+
+	e.writeConfigParam(cg, instID, "gain", 7.5)
+
+	// A new revision should now resolve to the written value.
+	if v, ok := e.readConfigParam(instID, "gain"); !ok || v != 7.5 {
+		t.Errorf("after write, gain = %v (ok=%v), want 7.5", v, ok)
+	}
+	inst, err := e.cfg.GetInstance(instID)
+	if err != nil {
+		t.Fatal("GetInstance:", err)
+	}
+	if inst.Version < 2 {
+		t.Errorf("instance version = %d, want >= 2 (a new revision)", inst.Version)
+	}
+}
+
+func TestCreateConfigInstance(t *testing.T) {
+	e, _, srcID := setupConfigEngine(t)
+	cg := &compiledGraph{name: "flow", engine: e, locals: map[string]float64{}}
+
+	src, err := e.cfg.GetInstance(srcID)
+	if err != nil {
+		t.Fatal("GetInstance:", err)
+	}
+
+	e.createConfigInstance(cg, src.SetID, "cold", srcID)
+
+	insts, err := e.cfg.List(confmgr.KindInstance)
+	if err != nil {
+		t.Fatal("List:", err)
+	}
+	var found *confmgr.ConfigInstance
+	for i := range insts {
+		if insts[i].Name == "cold" {
+			full, err := e.cfg.GetInstance(insts[i].ID)
+			if err != nil {
+				t.Fatal("GetInstance:", err)
+			}
+			found = &full
+		}
+	}
+	if found == nil {
+		t.Fatal("created instance 'cold' not found")
+	}
+	// Values copied from the source instance.
+	if got := toNum(found.Values["gain"]); got != 2.5 {
+		t.Errorf("copied gain = %v, want 2.5", got)
+	}
+}
+
+func TestSnapshotConfig(t *testing.T) {
+	e, src, instID := setupConfigEngine(t)
+	cg := &compiledGraph{name: "flow", engine: e, locals: map[string]float64{}}
+
+	// Seed current live values for the set's target signals.
+	_ = src.Write(context.Background(), "GAIN", 3.5)
+	_ = src.Write(context.Background(), "OFFSET", -2.0)
+
+	seed, err := e.cfg.GetInstance(instID)
+	if err != nil {
+		t.Fatal("GetInstance:", err)
+	}
+	e.snapshotConfig(cg, seed.SetID, "snap1")
+
+	insts, err := e.cfg.List(confmgr.KindInstance)
+	if err != nil {
+		t.Fatal("List:", err)
+	}
+	var found *confmgr.ConfigInstance
+	for i := range insts {
+		if insts[i].Name == "snap1" {
+			full, err := e.cfg.GetInstance(insts[i].ID)
+			if err != nil {
+				t.Fatal("GetInstance:", err)
+			}
+			found = &full
+		}
+	}
+	if found == nil {
+		t.Fatal("snapshot instance 'snap1' not found")
+	}
+	if got := toNum(found.Values["gain"]); got != 3.5 {
+		t.Errorf("snapshot gain = %v, want 3.5 (current live value)", got)
+	}
+	if got := toNum(found.Values["offset"]); got != -2.0 {
+		t.Errorf("snapshot offset = %v, want -2.0 (current live value)", got)
+	}
+}

internal/controllogic/engine.go

@@ -2,17 +2,38 @@ package controllogic
 
 import (
 	"context"
+	"errors"
+	"fmt"
 	"log/slog"
 	"math"
 	"regexp"
 	"strconv"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
+	"github.com/uopi/uopi/internal/audit"
 	"github.com/uopi/uopi/internal/broker"
+	"github.com/uopi/uopi/internal/confmgr"
 )
 
+// errUnknownSource is returned by config-apply writes targeting a data source
+// that isn't registered with the broker.
+var errUnknownSource = errors.New("unknown data source")
+
+// formatAny renders a config value for the audit log.
+func formatAny(v any) string {
+	switch x := v.(type) {
+	case float64:
+		return strconv.FormatFloat(x, 'g', -1, 64)
+	case string:
+		return x
+	default:
+		return fmt.Sprintf("%v", v)
+	}
+}
+
 // Guards against runaway flows (cycles / pathological loops).
 const (
 	maxSteps = 100000
@@ -25,6 +46,8 @@ const (
 type Engine struct {
 	broker *broker.Broker
 	store  *Store
+	cfg    *confmgr.Store
+	audit  audit.Recorder
 	log    *slog.Logger
 	root   context.Context
 
@@ -32,16 +55,39 @@ type Engine struct {
 	cancel context.CancelFunc // cancels the current generation
 	wg     *sync.WaitGroup    // tracks the current generation's goroutines
 
+	// notifier delivers action.dialog requests to connected clients. Stored in
+	// an atomic so flow goroutines can read it without taking e.mu (which Reload
+	// holds while it waits for those same goroutines to drain).
+	notifier atomic.Value // notifierBox
+
 	// Shared live signal cache for the current generation (key "ds\0name").
 	liveMu sync.RWMutex
 	live   map[string]float64
 }
 
-// NewEngine creates an engine bound to root. Call Reload to start it.
+// notifierBox wraps a Notifier so atomic.Value always sees one concrete type.
-func NewEngine(root context.Context, brk *broker.Broker, store *Store, log *slog.Logger) *Engine {
+type notifierBox struct{ n Notifier }
+
+// dialogSeq generates unique action.dialog ids across all graphs.
+var dialogSeq uint64
+
+// SetNotifier installs the sink for action.dialog requests. Safe to call once
+// at startup before or after Reload; it is read lock-free by running flows.
+func (e *Engine) SetNotifier(n Notifier) {
+	e.notifier.Store(notifierBox{n: n})
+}
+
+// NewEngine creates an engine bound to root. Call Reload to start it. rec records
+// the writes performed by flows; pass audit.Nop() to disable auditing.
+func NewEngine(root context.Context, brk *broker.Broker, store *Store, cfg *confmgr.Store, rec audit.Recorder, log *slog.Logger) *Engine {
+	if rec == nil {
+		rec = audit.Nop()
+	}
 	return &Engine{
 		broker: brk,
 		store:  store,
+		cfg:    cfg,
+		audit:  rec,
 		log:    log,
 		root:   root,
 		live:   map[string]float64{},
@@ -227,9 +273,276 @@ func (e *Engine) write(cg *compiledGraph, target string, val float64) {
 		e.log.Warn("control logic: write to unknown data source", "ds", ds, "signal", name)
 		return
 	}
+	ev := audit.Event{
+		Actor:     cg.name,
+		ActorType: audit.ActorSystem,
+		Action:    "signal.write",
+		DS:        ds,
+		Signal:    name,
+		Value:     strconv.FormatFloat(val, 'g', -1, 64),
+		Detail:    "control logic: " + cg.name,
+		Outcome:   audit.OutcomeOK,
+	}
 	if err := src.Write(e.root, name, val); err != nil {
 		e.log.Warn("control logic: write failed", "ds", ds, "signal", name, "err", err)
+		ev.Outcome = audit.OutcomeError
+		ev.Error = err.Error()
 	}
+	e.audit.Record(ev)
+}
+
+// applyConfig resolves a config instance + its set and writes every parameter
+// to its target signal via the owning data source (confmgr.Apply). Each write is
+// audited. A bare instance id or a missing config store is a no-op (logged).
+func (e *Engine) applyConfig(cg *compiledGraph, instanceID string) {
+	if e.cfg == nil || instanceID == "" {
+		return
+	}
+	inst, err := e.cfg.GetInstance(instanceID)
+	if err != nil {
+		e.log.Warn("control logic: config apply: unknown instance", "instance", instanceID, "err", err)
+		return
+	}
+	set, err := e.cfg.SetForInstance(inst)
+	if err != nil {
+		e.log.Warn("control logic: config apply: set lookup failed", "instance", instanceID, "err", err)
+		return
+	}
+	write := func(ds, signal string, value any) error {
+		ev := audit.Event{
+			Actor:     cg.name,
+			ActorType: audit.ActorSystem,
+			Action:    "signal.write",
+			DS:        ds,
+			Signal:    signal,
+			Value:     formatAny(value),
+			Detail:    "control logic config apply: " + inst.Name,
+			Outcome:   audit.OutcomeOK,
+		}
+		var werr error
+		if ds == "local" {
+			cg.setLocal(signal, toNum(value))
+		} else if src, ok := e.broker.Source(ds); ok {
+			werr = src.Write(e.root, signal, value)
+		} else {
+			werr = errUnknownSource
+		}
+		if werr != nil {
+			ev.Outcome = audit.OutcomeError
+			ev.Error = werr.Error()
+		}
+		e.audit.Record(ev)
+		return werr
+	}
+	confmgr.Apply(set, inst, write)
+}
+
+// readConfigParam resolves a single parameter's value from a config instance,
+// coercing it to float64 for use as a control-logic value. Returns ok=false if
+// the store/instance/param is missing or the value isn't numeric.
+func (e *Engine) readConfigParam(instanceID, key string) (float64, bool) {
+	if e.cfg == nil || instanceID == "" || key == "" {
+		return 0, false
+	}
+	inst, err := e.cfg.GetInstance(instanceID)
+	if err != nil {
+		e.log.Warn("control logic: config read: unknown instance", "instance", instanceID, "err", err)
+		return 0, false
+	}
+	set, err := e.cfg.SetForInstance(inst)
+	if err != nil {
+		e.log.Warn("control logic: config read: set lookup failed", "instance", instanceID, "err", err)
+		return 0, false
+	}
+	for _, p := range set.Parameters {
+		if p.Key != key {
+			continue
+		}
+		v, ok := inst.Resolve(p)
+		if !ok {
+			return 0, false
+		}
+		f := toNum(v)
+		if math.IsNaN(f) {
+			return 0, false
+		}
+		return f, true
+	}
+	return 0, false
+}
+
+// writeConfigParam sets a single parameter's value on a config instance and
+// saves a new revision (git-style). The value is coerced to the parameter's
+// declared type (numeric/bool/string) so it validates against the set. A
+// missing store/instance/param is a no-op (logged). Audited.
+func (e *Engine) writeConfigParam(cg *compiledGraph, instanceID, key string, val float64) {
+	if e.cfg == nil || instanceID == "" || key == "" {
+		return
+	}
+	inst, err := e.cfg.GetInstance(instanceID)
+	if err != nil {
+		e.log.Warn("control logic: config write: unknown instance", "instance", instanceID, "err", err)
+		return
+	}
+	set, err := e.cfg.SetForInstance(inst)
+	if err != nil {
+		e.log.Warn("control logic: config write: set lookup failed", "instance", instanceID, "err", err)
+		return
+	}
+	var param *confmgr.Parameter
+	for i := range set.Parameters {
+		if set.Parameters[i].Key == key {
+			param = &set.Parameters[i]
+			break
+		}
+	}
+	if param == nil {
+		e.log.Warn("control logic: config write: unknown parameter", "instance", instanceID, "key", key)
+		return
+	}
+	if inst.Values == nil {
+		inst.Values = map[string]any{}
+	}
+	inst.Values[key] = coerceParamValue(*param, val)
+	ev := audit.Event{
+		Actor:     cg.name,
+		ActorType: audit.ActorSystem,
+		Action:    "config.instance.update",
+		Detail:    "control logic config write: " + inst.Name + " " + key + "=" + formatAny(inst.Values[key]),
+		Outcome:   audit.OutcomeOK,
+	}
+	if _, err := e.cfg.UpdateInstance(instanceID, inst, ""); err != nil {
+		e.log.Warn("control logic: config write failed", "instance", instanceID, "key", key, "err", err)
+		ev.Outcome = audit.OutcomeError
+		ev.Error = err.Error()
+	}
+	e.audit.Record(ev)
+}
+
+// createConfigInstance creates a new config instance for setID, optionally
+// copying values from an existing instance (fromID). A missing store/set is a
+// no-op (logged). Audited. The new instance's id is logged but not written back
+// to a flow variable (control-logic variables are numeric, ids are strings).
+func (e *Engine) createConfigInstance(cg *compiledGraph, setID, name, fromID string) {
+	if e.cfg == nil || setID == "" {
+		return
+	}
+	if name == "" {
+		name = "auto"
+	}
+	values := map[string]any{}
+	if fromID != "" {
+		if src, err := e.cfg.GetInstance(fromID); err == nil {
+			for k, v := range src.Values {
+				values[k] = v
+			}
+		} else {
+			e.log.Warn("control logic: config create: copy source missing", "from", fromID, "err", err)
+		}
+	}
+	inst := confmgr.ConfigInstance{Name: name, SetID: setID, Values: values}
+	ev := audit.Event{
+		Actor:     cg.name,
+		ActorType: audit.ActorSystem,
+		Action:    "config.instance.create",
+		Detail:    "control logic config create: set=" + setID + " name=" + name,
+		Outcome:   audit.OutcomeOK,
+	}
+	out, err := e.cfg.CreateInstance(inst, "")
+	if err != nil {
+		e.log.Warn("control logic: config create failed", "set", setID, "err", err)
+		ev.Outcome = audit.OutcomeError
+		ev.Error = err.Error()
+	} else {
+		ev.Detail += " -> " + out.ID
+	}
+	e.audit.Record(ev)
+}
+
+// snapshotConfig captures the current value of every target signal of a set and
+// stores them as a new config instance. A missing store/set is a no-op (logged).
+// Audited. The new instance's id is logged but not written back to a flow
+// variable (control-logic variables are numeric, ids are strings).
+func (e *Engine) snapshotConfig(cg *compiledGraph, setID, name string) {
+	if e.cfg == nil || setID == "" {
+		return
+	}
+	set, err := e.cfg.GetSet(setID)
+	if err != nil {
+		e.log.Warn("control logic: config snapshot: unknown set", "set", setID, "err", err)
+		return
+	}
+	ctx, cancel := context.WithTimeout(e.root, 5*time.Second)
+	defer cancel()
+	read := func(ds, signal string) (any, error) {
+		if ds == "local" {
+			return cg.getLocal(signal), nil
+		}
+		v, err := e.broker.ReadNow(ctx, broker.SignalRef{DS: ds, Name: signal})
+		if err != nil {
+			return nil, err
+		}
+		return v.Data, nil
+	}
+	snap := confmgr.Snapshot(set, read)
+	if name == "" {
+		name = set.Name + " snapshot"
+	}
+	inst := confmgr.ConfigInstance{Name: name, SetID: setID, Values: snap.Values}
+	ev := audit.Event{
+		Actor:     cg.name,
+		ActorType: audit.ActorSystem,
+		Action:    "config.instance.snapshot",
+		Detail:    "control logic config snapshot: set=" + setID + " name=" + name,
+		Outcome:   audit.OutcomeOK,
+	}
+	out, err := e.cfg.CreateInstance(inst, "")
+	if err != nil {
+		e.log.Warn("control logic: config snapshot failed", "set", setID, "err", err)
+		ev.Outcome = audit.OutcomeError
+		ev.Error = err.Error()
+	} else {
+		ev.Detail += " -> " + out.ID + " captured=" + strconv.Itoa(snap.Captured) + " failed=" + strconv.Itoa(snap.Failed)
+	}
+	e.audit.Record(ev)
+}
+
+// coerceParamValue converts a numeric flow value to the Go type a config
+// parameter expects, so the resulting instance validates against its set.
+func coerceParamValue(p confmgr.Parameter, val float64) any {
+	switch p.Type {
+	case confmgr.TypeInt:
+		return int64(val)
+	case confmgr.TypeBool:
+		return val != 0
+	case confmgr.TypeString, confmgr.TypeEnum:
+		return strconv.FormatFloat(val, 'g', -1, 64)
+	default:
+		return val
+	}
+}
+
+// emitDialog delivers an action.dialog node's request to the installed Notifier
+// (the WebSocket dialog hub). It is lock-free so it never deadlocks against a
+// concurrent Reload that is waiting for this flow goroutine to finish.
+func (e *Engine) emitDialog(n Node) {
+	box, _ := e.notifier.Load().(notifierBox)
+	if box.n == nil {
+		return
+	}
+	kind := strings.TrimSpace(n.param("kind"))
+	if kind != "error" && kind != "input" {
+		kind = "info"
+	}
+	box.n.Notify(Dialog{
+		ID:      strconv.FormatUint(atomic.AddUint64(&dialogSeq, 1), 10),
+		Kind:    kind,
+		Title:   n.param("title"),
+		Message: n.param("message"),
+		Target:  strings.TrimSpace(n.param("target")),
+		Users:   splitCSV(n.param("users")),
+		Groups:  splitCSV(n.param("groups")),
+	})
 }
 
 // ── compiled graph ─────────────────────────────────────────────────────────────
@@ -612,6 +925,30 @@ func (cg *compiledGraph) run(nodeID string, ctx *runCtx) {
 		cg.engine.write(cg, node.param("target"), val)
 		cg.follow(node.ID, "out", ctx)
 
+	case "action.config.apply":
+		cg.engine.applyConfig(cg, strings.TrimSpace(node.param("instance")))
+		cg.follow(node.ID, "out", ctx)
+
+	case "action.config.read":
+		v, ok := cg.engine.readConfigParam(strings.TrimSpace(node.param("instance")), strings.TrimSpace(node.param("key")))
+		if ok {
+			cg.engine.write(cg, node.param("target"), v)
+		}
+		cg.follow(node.ID, "out", ctx)
+
+	case "action.config.write":
+		val := EvalExpr(node.param("expr"), ctx.resolve)
+		cg.engine.writeConfigParam(cg, strings.TrimSpace(node.param("instance")), strings.TrimSpace(node.param("key")), val)
+		cg.follow(node.ID, "out", ctx)
+
+	case "action.config.create":
+		cg.engine.createConfigInstance(cg, strings.TrimSpace(node.param("set")), strings.TrimSpace(node.param("name")), strings.TrimSpace(node.param("from")))
+		cg.follow(node.ID, "out", ctx)
+
+	case "action.config.snapshot":
+		cg.engine.snapshotConfig(cg, strings.TrimSpace(node.param("set")), strings.TrimSpace(node.param("name")))
+		cg.follow(node.ID, "out", ctx)
+
 	case "action.delay":
 		ms := 0
 		if v, err := strconv.Atoi(strings.TrimSpace(node.param("ms"))); err == nil && v > 0 {
@@ -638,6 +975,10 @@ func (cg *compiledGraph) run(nodeID string, ctx *runCtx) {
 		cg.runLua(node.ID, ctx)
 		cg.follow(node.ID, "out", ctx)
 
+	case "action.dialog":
+		cg.engine.emitDialog(node)
+		cg.follow(node.ID, "out", ctx)
+
 	default:
 		cg.follow(node.ID, "out", ctx)
 	}

internal/controllogic/model.go

@@ -29,6 +29,8 @@ package controllogic
 //	action.delay      — waits `ms` before continuing.
 //	action.log        — logs an expression value to the server log.
 //	action.lua        — runs a sandboxed Lua script with get/set/log host funcs.
+//	action.dialog     — pushes an info/error/input dialog to connected clients
+//	                    filtered by user/group; input responses write `target`.
 
 // Node is a single node in a control-logic graph. Params are stored as strings
 // (matching the panel logic model) and parsed per-kind by the engine.
@@ -53,6 +55,8 @@ type Graph struct {
 	ID      string `json:"id"`
 	Name    string `json:"name"`
 	Enabled bool   `json:"enabled"`
+	Version int    `json:"version,omitempty"` // git-style revision; bumped on each Save
+	Tag     string `json:"tag,omitempty"`     // optional revision label (e.g. "restored from v3")
 	Nodes   []Node `json:"nodes"`
 	Wires   []Wire `json:"wires"`
 }

internal/controllogic/notify.go

@@ -0,0 +1,37 @@
+package controllogic
+
+import "strings"
+
+// Dialog is a user-facing notification or input request emitted by an
+// action.dialog node. It is delivered to connected clients whose identity
+// matches Users/Groups (both empty = everyone). For an "input" dialog the
+// client's response is written back to Target (a "ds:name" reference, e.g.
+// "srv:approved") so control logic can read it on a later activation.
+type Dialog struct {
+	ID      string   `json:"id"`
+	Kind    string   `json:"kind"` // "info" | "error" | "input"
+	Title   string   `json:"title"`
+	Message string   `json:"message"`
+	Target  string   `json:"target,omitempty"`
+	Users   []string `json:"users,omitempty"`
+	Groups  []string `json:"groups,omitempty"`
+}
+
+// Notifier delivers control-logic dialogs to connected clients. The server
+// implements it; the engine calls Notify when an action.dialog node runs.
+// Notify must not block (the hub fans out without waiting on slow clients).
+type Notifier interface {
+	Notify(Dialog)
+}
+
+// splitCSV parses a comma-separated user/group filter into trimmed,
+// non-empty tokens. An empty string yields a nil slice (no filter).
+func splitCSV(s string) []string {
+	var out []string
+	for _, p := range strings.Split(s, ",") {
+		if t := strings.TrimSpace(p); t != "" {
+			out = append(out, t)
+		}
+	}
+	return out
+}

internal/controllogic/store.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"path/filepath"
 	"sync"
+	"time"
 )
 
 const definitionsFile = "controllogic.json"
@@ -16,9 +17,15 @@ var ErrNotFound = errors.New("control logic graph not found")
 
 // Store persists control-logic graphs as a single JSON file in the storage dir.
 // Writes are atomic (tmp file + rename); all access is mutex-guarded.
+//
+// Git-style versioning: the live graph lives in controllogic.json (the current
+// revision), while every superseded revision is preserved as a backup file
+// {id}.vN.json under versionsDir. Promote/Fork build on these backups.
 type Store struct {
 	mu          sync.RWMutex
 	path        string
+	trashDir    string
+	versionsDir string
 	items       map[string]Graph
 }
 
@@ -26,6 +33,8 @@ type Store struct {
 func NewStore(storageDir string) (*Store, error) {
 	s := &Store{
 		path:        filepath.Join(storageDir, definitionsFile),
+		trashDir:    filepath.Join(storageDir, "trash", "controllogic"),
+		versionsDir: filepath.Join(storageDir, "controllogic_versions"),
 		items:       map[string]Graph{},
 	}
 	if err := s.load(); err != nil {
@@ -91,21 +100,72 @@ func (s *Store) Get(id string) (Graph, error) {
 	return g, nil
 }
 
-// Save inserts or replaces a graph and persists the store.
+// Save inserts or replaces a graph and persists the store. When replacing an
+// existing graph the superseded revision is backed up as {id}.vN.json and the
+// new graph's Version is bumped; a brand-new graph starts at version 1.
 func (s *Store) Save(g Graph) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
+	if old, ok := s.items[g.ID]; ok {
+		oldV := old.Version
+		if oldV < 1 {
+			oldV = 1
+			old.Version = 1
+		}
+		if err := s.backupLocked(old); err != nil {
+			return fmt.Errorf("back up control logic revision: %w", err)
+		}
+		g.Version = oldV + 1
+	} else if g.Version < 1 {
+		g.Version = 1
+	}
 	s.items[g.ID] = g
 	return s.saveLocked()
 }
 
-// Delete removes a graph by id.
+// backupLocked writes a single graph revision to versionsDir as {id}.vN.json.
+// Caller must hold s.mu.
+func (s *Store) backupLocked(g Graph) error {
+	if err := os.MkdirAll(s.versionsDir, 0o755); err != nil {
+		return err
+	}
+	data, err := json.MarshalIndent(g, "", "  ")
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(s.versionPath(g.ID, g.Version), data, 0o644)
+}
+
+func (s *Store) versionPath(id string, version int) string {
+	return filepath.Join(s.versionsDir, fmt.Sprintf("%s.v%d.json", id, version))
+}
+
+// Delete removes a graph by id, first writing a copy into the trash folder so it
+// can be recovered if needed. The trash backup is best-effort: a failure to write
+// it does not prevent the delete (but is reported).
 func (s *Store) Delete(id string) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	if _, ok := s.items[id]; !ok {
+	g, ok := s.items[id]
+	if !ok {
 		return ErrNotFound
 	}
+	if err := s.trash(g); err != nil {
+		return fmt.Errorf("move control logic to trash: %w", err)
+	}
 	delete(s.items, id)
 	return s.saveLocked()
 }
+
+// trash writes a single graph as a timestamped JSON file under the trash folder.
+func (s *Store) trash(g Graph) error {
+	if err := os.MkdirAll(s.trashDir, 0o755); err != nil {
+		return err
+	}
+	data, err := json.MarshalIndent(g, "", "  ")
+	if err != nil {
+		return err
+	}
+	dst := filepath.Join(s.trashDir, fmt.Sprintf("%s.%d.json", g.ID, time.Now().UnixMilli()))
+	return os.WriteFile(dst, data, 0o644)
+}

internal/controllogic/versions.go

@@ -0,0 +1,142 @@
+package controllogic
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// VersionMeta describes a single persisted revision of a control-logic graph,
+// mirroring storage.VersionMeta so the frontend can treat all versioned
+// document types uniformly.
+type VersionMeta struct {
+	Version int       `json:"version"`
+	Name    string    `json:"name"`
+	Tag     string    `json:"tag,omitempty"`
+	Current bool      `json:"current"`
+	SavedAt time.Time `json:"savedAt"`
+}
+
+// Versions returns metadata for every persisted revision of the graph, newest
+// first. The live revision (held in controllogic.json) is flagged Current.
+func (s *Store) Versions(id string) ([]VersionMeta, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	cur, ok := s.items[id]
+	if !ok {
+		return nil, ErrNotFound
+	}
+	curV := cur.Version
+	if curV < 1 {
+		curV = 1
+	}
+
+	var savedAt time.Time
+	if info, err := os.Stat(s.path); err == nil {
+		savedAt = info.ModTime()
+	}
+	out := []VersionMeta{{Version: curV, Name: cur.Name, Tag: cur.Tag, Current: true, SavedAt: savedAt}}
+
+	entries, err := os.ReadDir(s.versionsDir)
+	if err != nil && !os.IsNotExist(err) {
+		return nil, err
+	}
+	prefix := id + ".v"
+	for _, e := range entries {
+		name := e.Name()
+		if e.IsDir() || !strings.HasPrefix(name, prefix) || !strings.HasSuffix(name, ".json") {
+			continue
+		}
+		vStr := strings.TrimSuffix(strings.TrimPrefix(name, prefix), ".json")
+		v, err := strconv.Atoi(vStr)
+		if err != nil {
+			continue
+		}
+		g, err := s.readVersion(id, v)
+		if err != nil {
+			continue
+		}
+		info, err := e.Info()
+		if err != nil {
+			continue
+		}
+		out = append(out, VersionMeta{Version: v, Name: g.Name, Tag: g.Tag, SavedAt: info.ModTime()})
+	}
+
+	sort.Slice(out, func(i, j int) bool { return out[i].Version > out[j].Version })
+	return out, nil
+}
+
+// GetVersion returns a specific revision of the graph. The current revision is
+// served from the live store; older revisions come from their backup file.
+func (s *Store) GetVersion(id string, version int) (Graph, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	cur, ok := s.items[id]
+	if !ok {
+		return Graph{}, ErrNotFound
+	}
+	curV := cur.Version
+	if curV < 1 {
+		curV = 1
+	}
+	if version == curV {
+		return cur, nil
+	}
+	return s.readVersion(id, version)
+}
+
+// readVersion loads a backup revision file. Caller must hold s.mu.
+func (s *Store) readVersion(id string, version int) (Graph, error) {
+	data, err := os.ReadFile(s.versionPath(id, version))
+	if os.IsNotExist(err) {
+		return Graph{}, ErrNotFound
+	}
+	if err != nil {
+		return Graph{}, err
+	}
+	var g Graph
+	if err := json.Unmarshal(data, &g); err != nil {
+		return Graph{}, fmt.Errorf("parse revision: %w", err)
+	}
+	return g, nil
+}
+
+// Promote makes a past revision current by re-saving it on top of history. The
+// existing current revision is preserved as a backup, so promotion is
+// non-destructive. Returns the resulting (new current) graph.
+func (s *Store) Promote(id string, version int) (Graph, error) {
+	g, err := s.GetVersion(id, version)
+	if err != nil {
+		return Graph{}, err
+	}
+	g.Tag = fmt.Sprintf("restored from v%d", version)
+	if err := s.Save(g); err != nil {
+		return Graph{}, err
+	}
+	return s.Get(id)
+}
+
+// Fork creates a brand-new graph from a specific revision, assigning a fresh id
+// and resetting its version to 1. Returns the new graph.
+func (s *Store) Fork(id string, version int) (Graph, error) {
+	g, err := s.GetVersion(id, version)
+	if err != nil {
+		return Graph{}, err
+	}
+	g.ID = fmt.Sprintf("%s-fork-%d", id, time.Now().UnixMilli())
+	g.Version = 1
+	g.Tag = ""
+	if g.Name != "" {
+		g.Name = g.Name + " (fork)"
+	}
+	if err := s.Save(g); err != nil {
+		return Graph{}, err
+	}
+	return g, nil
+}

internal/controllogic/versions_test.go

@@ -0,0 +1,70 @@
+package controllogic
+
+import "testing"
+
+func TestControlLogicVersioning(t *testing.T) {
+	dir := t.TempDir()
+	s, err := NewStore(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	g := Graph{ID: "cl-1", Name: "loop", Enabled: true,
+		Nodes: []Node{{ID: "n1", Kind: "trigger.timer", Params: map[string]string{"interval": "1000"}}}}
+	if err := s.Save(g); err != nil {
+		t.Fatalf("Save v1: %v", err)
+	}
+	if got, _ := s.Get("cl-1"); got.Version != 1 {
+		t.Fatalf("after create: version=%d", got.Version)
+	}
+
+	// Two edits → v2, v3.
+	g.Name = "loop-2"
+	if err := s.Save(g); err != nil {
+		t.Fatalf("Save v2: %v", err)
+	}
+	g.Name = "loop-3"
+	if err := s.Save(g); err != nil {
+		t.Fatalf("Save v3: %v", err)
+	}
+	if got, _ := s.Get("cl-1"); got.Version != 3 || got.Name != "loop-3" {
+		t.Fatalf("current: version=%d name=%q", got.Version, got.Name)
+	}
+
+	versions, err := s.Versions("cl-1")
+	if err != nil {
+		t.Fatalf("Versions: %v", err)
+	}
+	if len(versions) != 3 {
+		t.Fatalf("want 3 versions, got %d", len(versions))
+	}
+	if !versions[0].Current || versions[0].Version != 3 {
+		t.Errorf("newest should be current v3: %+v", versions[0])
+	}
+
+	v1, err := s.GetVersion("cl-1", 1)
+	if err != nil || v1.Name != "loop" {
+		t.Fatalf("GetVersion v1: name=%q err=%v", v1.Name, err)
+	}
+
+	// Promote v1 → v4.
+	promoted, err := s.Promote("cl-1", 1)
+	if err != nil {
+		t.Fatalf("Promote: %v", err)
+	}
+	if promoted.Version != 4 || promoted.Name != "loop" {
+		t.Errorf("promote: version=%d name=%q", promoted.Version, promoted.Name)
+	}
+
+	// Fork v3 → new id, version 1.
+	forked, err := s.Fork("cl-1", 3)
+	if err != nil {
+		t.Fatalf("Fork: %v", err)
+	}
+	if forked.Version != 1 || forked.ID == "cl-1" {
+		t.Errorf("fork: id=%q version=%d", forked.ID, forked.Version)
+	}
+	if got, err := s.Get(forked.ID); err != nil || got.Name != forked.Name {
+		t.Errorf("forked graph not stored: %v", err)
+	}
+}

internal/datasource/epics/archive.go

@@ -112,6 +112,8 @@ func fetchArchiveHistory(ctx context.Context, archiveURL, signal string, start,
 			Timestamp: ts,
 			Data:      data,
 			Quality:   q,
+			Severity:  p.Severity,
+			Status:    p.Status,
 		})
 	}
 

internal/datasource/epics/ca_callback.go

@@ -22,7 +22,7 @@ import (
 //
 //export goCAMonitorCallback
 func goCAMonitorCallback(handle C.uintptr_t, dbrType C.int, count C.long,
-	dbr unsafe.Pointer, severity C.int, epicsTimeSecs C.double) {
+	dbr unsafe.Pointer, severity C.int, status C.int, epicsTimeSecs C.double) {
 
 	h := uintptr(handle)
 
@@ -79,7 +79,13 @@ func goCAMonitorCallback(handle C.uintptr_t, dbrType C.int, count C.long,
 		data = float64(0)
 	}
 
-	v := datasource.Value{Timestamp: ts, Data: data, Quality: q}
+	v := datasource.Value{
+		Timestamp: ts,
+		Data:      data,
+		Quality:   q,
+		Severity:  int(severity),
+		Status:    int(status),
+	}
 
 	// Look up the subscription channel under the global handle table lock and
 	// perform a non-blocking send so we never stall the CA callback thread.
@@ -129,6 +135,7 @@ func goCAConnectionCallback(handle C.uintptr_t, connected C.int) {
 				Timestamp: time.Now(),
 				Data:      float64(0),
 				Quality:   datasource.QualityBad,
+				Severity:  3, // INVALID
 			}
 			select {
 			case ch <- v:

internal/datasource/epics/ca_wrapper.h

@@ -13,7 +13,7 @@
  * goCAConnectionCallback is called when a channel connects or disconnects.
  */
 extern void goCAMonitorCallback(uintptr_t handle, int dbrType, long count,
-                                void *dbr, int severity,
+                                void *dbr, int severity, int status,
                                 double epicsTimeSecs);
 extern void goCAConnectionCallback(uintptr_t handle, int connected);
 
@@ -30,9 +30,10 @@ static void caMonitorCallbackShim(struct event_handler_args args) {
 
     double timeSecs = 0.0;
     int    severity = 0;
+    int    status   = 0;
 
     /*
-     * Determine the timestamp and alarm severity from the DBR type.
+     * Determine the timestamp and alarm severity/status from the DBR type.
      * We request DBR_TIME_* types so the timestamp is embedded in the value
      * buffer right after the alarm fields (struct dbr_time_double et al.).
      */
@@ -41,36 +42,42 @@ static void caMonitorCallbackShim(struct event_handler_args args) {
         const struct dbr_time_double *p = (const struct dbr_time_double *)args.dbr;
         timeSecs = (double)p->stamp.secPastEpoch + (double)p->stamp.nsec / 1e9;
         severity = (int)p->severity;
+        status   = (int)p->status;
         break;
     }
     case DBR_TIME_FLOAT: {
         const struct dbr_time_float *p = (const struct dbr_time_float *)args.dbr;
         timeSecs = (double)p->stamp.secPastEpoch + (double)p->stamp.nsec / 1e9;
         severity = (int)p->severity;
+        status   = (int)p->status;
         break;
     }
     case DBR_TIME_LONG: {
         const struct dbr_time_long *p = (const struct dbr_time_long *)args.dbr;
         timeSecs = (double)p->stamp.secPastEpoch + (double)p->stamp.nsec / 1e9;
         severity = (int)p->severity;
+        status   = (int)p->status;
         break;
     }
     case DBR_TIME_SHORT: {
         const struct dbr_time_short *p = (const struct dbr_time_short *)args.dbr;
         timeSecs = (double)p->stamp.secPastEpoch + (double)p->stamp.nsec / 1e9;
         severity = (int)p->severity;
+        status   = (int)p->status;
         break;
     }
     case DBR_TIME_STRING: {
         const struct dbr_time_string *p = (const struct dbr_time_string *)args.dbr;
         timeSecs = (double)p->stamp.secPastEpoch + (double)p->stamp.nsec / 1e9;
         severity = (int)p->severity;
+        status   = (int)p->status;
         break;
     }
     case DBR_TIME_ENUM: {
         const struct dbr_time_enum *p = (const struct dbr_time_enum *)args.dbr;
         timeSecs = (double)p->stamp.secPastEpoch + (double)p->stamp.nsec / 1e9;
         severity = (int)p->severity;
+        status   = (int)p->status;
         break;
     }
     default:
@@ -78,7 +85,7 @@ static void caMonitorCallbackShim(struct event_handler_args args) {
     }
 
     goCAMonitorCallback((uintptr_t)args.usr, (int)args.type, (long)args.count,
-                        (void *)args.dbr, severity, timeSecs);
+                        (void *)args.dbr, severity, status, timeSecs);
 }
 
 /*

internal/datasource/epics/noop.go

@@ -275,6 +275,8 @@ func (e *EPICS) timeValueToDS(signal string, tv proto.TimeValue) datasource.Valu
 		Timestamp: tv.Timestamp,
 		Data:      data,
 		Quality:   quality,
+		Severity:  int(tv.Severity),
+		Status:    int(tv.Status),
 	}
 }
 

internal/datasource/iface.go

@@ -45,6 +45,8 @@ type Value struct {
 	Timestamp  time.Time
 	Data       any // float64 | []float64 | string | int64 | bool
 	Quality    Quality
+	Severity   int  // raw EPICS alarm severity (0=NO_ALARM,1=MINOR,2=MAJOR,3=INVALID); 0 for sources without alarm info
+	Status     int  // raw EPICS alarm status (.STAT); 0 for sources without alarm info
 	MetaUpdate bool // if true, metadata was refreshed — dispatcher should re-send meta
 }
 

internal/datasource/pva/pva.go

@@ -180,6 +180,7 @@ func structToValue(sv pvdata.StructValue) datasource.Value {
 	val := fieldByName(sv, "value")
 	ts := extractTimestamp(sv)
 	quality := extractQuality(sv)
+	severity, status := extractSeverityStatus(sv)
 
 	var data any
 	if val != nil {
@@ -190,6 +191,8 @@ func structToValue(sv pvdata.StructValue) datasource.Value {
 		Timestamp: ts,
 		Data:      data,
 		Quality:   quality,
+		Severity:  severity,
+		Status:    status,
 	}
 }
 
@@ -329,6 +332,26 @@ func extractQuality(sv pvdata.StructValue) datasource.Quality {
 	}
 }
 
+// extractSeverityStatus pulls the raw EPICS alarm severity and status from the
+// NTScalar "alarm" struct. Returns (0, 0) when no alarm struct is present.
+func extractSeverityStatus(sv pvdata.StructValue) (severity, status int) {
+	alarm := structByName(sv, "alarm")
+	if alarm == nil {
+		return 0, 0
+	}
+	if v := fieldByName(*alarm, "severity"); v != nil {
+		if s, ok := v.(int32); ok {
+			severity = int(s)
+		}
+	}
+	if v := fieldByName(*alarm, "status"); v != nil {
+		if s, ok := v.(int32); ok {
+			status = int(s)
+		}
+	}
+	return severity, status
+}
+
 func toFloat64(v any) (float64, bool) {
 	switch x := v.(type) {
 	case float64:

internal/datasource/servervar/servervar.go

@@ -0,0 +1,212 @@
+// Package servervar provides a small persistent key/value data source for
+// "server variables": named scalar values that the server-side control-logic
+// engine writes (e.g. the state of a sequence) and that interface panels can
+// read live. Panels may read any variable; writes from panels are gated to
+// control-logic editors in the WebSocket write handler.
+package servervar
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"sort"
+	"sync"
+	"time"
+
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+const fileName = "servervars.json"
+
+type variable struct {
+	value float64
+	ts    time.Time
+}
+
+// Source is the "srv" data source. Variables are created on first write and
+// persisted so their last value survives a restart.
+type Source struct {
+	path string
+
+	mu     sync.RWMutex
+	vars   map[string]*variable
+	subs   map[string]map[int]chan<- datasource.Value
+	nextID int
+}
+
+// New opens (or initialises) the server-variable store under storageDir.
+func New(storageDir string) (*Source, error) {
+	s := &Source{
+		path: filepath.Join(storageDir, fileName),
+		vars: map[string]*variable{},
+		subs: map[string]map[int]chan<- datasource.Value{},
+	}
+	if err := s.load(); err != nil {
+		return nil, err
+	}
+	return s, nil
+}
+
+func (s *Source) load() error {
+	data, err := os.ReadFile(s.path)
+	if os.IsNotExist(err) {
+		return nil
+	}
+	if err != nil {
+		return err
+	}
+	var raw map[string]float64
+	if err := json.Unmarshal(data, &raw); err != nil {
+		return err
+	}
+	now := time.Now()
+	for name, v := range raw {
+		s.vars[name] = &variable{value: v, ts: now}
+	}
+	return nil
+}
+
+// saveLocked persists the current values atomically. Caller holds s.mu.
+func (s *Source) saveLocked() {
+	raw := make(map[string]float64, len(s.vars))
+	for name, v := range s.vars {
+		raw[name] = v.value
+	}
+	data, err := json.MarshalIndent(raw, "", "  ")
+	if err != nil {
+		return
+	}
+	tmp := s.path + ".tmp"
+	if err := os.WriteFile(tmp, data, 0o644); err != nil {
+		return
+	}
+	_ = os.Rename(tmp, s.path)
+}
+
+func meta(name string) datasource.Metadata {
+	return datasource.Metadata{
+		Name:        name,
+		Type:        datasource.TypeFloat64,
+		Description: "Server variable",
+		Writable:    true,
+	}
+}
+
+// Name implements datasource.DataSource.
+func (s *Source) Name() string { return "srv" }
+
+// Connect is a no-op — the store is opened in New.
+func (s *Source) Connect(_ context.Context) error { return nil }
+
+// ListSignals returns metadata for every defined server variable.
+func (s *Source) ListSignals(_ context.Context) ([]datasource.Metadata, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	names := make([]string, 0, len(s.vars))
+	for name := range s.vars {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	out := make([]datasource.Metadata, 0, len(names))
+	for _, name := range names {
+		out = append(out, meta(name))
+	}
+	return out, nil
+}
+
+// GetMetadata returns metadata for a single variable. Unknown names still report
+// writable metadata so that control logic / authorised panels may create them.
+func (s *Source) GetMetadata(_ context.Context, signal string) (datasource.Metadata, error) {
+	return meta(signal), nil
+}
+
+// Subscribe registers ch for updates and immediately delivers the current value.
+func (s *Source) Subscribe(ctx context.Context, signal string, ch chan<- datasource.Value) (datasource.CancelFunc, error) {
+	s.mu.Lock()
+	if s.subs[signal] == nil {
+		s.subs[signal] = map[int]chan<- datasource.Value{}
+	}
+	id := s.nextID
+	s.nextID++
+	s.subs[signal][id] = ch
+	cur, ok := s.vars[signal]
+	var first datasource.Value
+	if ok {
+		first = datasource.Value{Timestamp: cur.ts, Data: cur.value, Quality: datasource.QualityGood}
+	}
+	s.mu.Unlock()
+
+	if ok {
+		go func() {
+			select {
+			case ch <- first:
+			case <-ctx.Done():
+			}
+		}()
+	}
+
+	return func() {
+		s.mu.Lock()
+		if m := s.subs[signal]; m != nil {
+			delete(m, id)
+			if len(m) == 0 {
+				delete(s.subs, signal)
+			}
+		}
+		s.mu.Unlock()
+	}, nil
+}
+
+func toFloat64(v any) float64 {
+	switch x := v.(type) {
+	case float64:
+		return x
+	case float32:
+		return float64(x)
+	case int:
+		return float64(x)
+	case int64:
+		return float64(x)
+	case bool:
+		if x {
+			return 1
+		}
+		return 0
+	case json.Number:
+		f, _ := x.Float64()
+		return f
+	default:
+		return 0
+	}
+}
+
+// Write sets a variable (creating it if needed), persists, and fans the new value
+// out to all subscribers.
+func (s *Source) Write(_ context.Context, signal string, value any) error {
+	v := toFloat64(value)
+
+	s.mu.Lock()
+	now := time.Now()
+	s.vars[signal] = &variable{value: v, ts: now}
+	s.saveLocked()
+	subs := make([]chan<- datasource.Value, 0, len(s.subs[signal]))
+	for _, ch := range s.subs[signal] {
+		subs = append(subs, ch)
+	}
+	s.mu.Unlock()
+
+	upd := datasource.Value{Timestamp: now, Data: v, Quality: datasource.QualityGood}
+	for _, ch := range subs {
+		select {
+		case ch <- upd:
+		default:
+		}
+	}
+	return nil
+}
+
+// History is not supported.
+func (s *Source) History(_ context.Context, _ string, _, _ time.Time, _ int) ([]datasource.Value, error) {
+	return nil, datasource.ErrHistoryUnavailable
+}

internal/datasource/servervar/servervar_test.go

@@ -0,0 +1,74 @@
+package servervar
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+func TestWriteSubscribePersist(t *testing.T) {
+	dir := t.TempDir()
+	s, err := New(dir)
+	if err != nil {
+		t.Fatalf("New: %v", err)
+	}
+	ctx := context.Background()
+
+	if err := s.Write(ctx, "seq_state", 3.0); err != nil {
+		t.Fatalf("Write: %v", err)
+	}
+
+	// Subscribe should deliver the current value immediately.
+	ch := make(chan datasource.Value, 4)
+	cancel, err := s.Subscribe(ctx, "seq_state", ch)
+	if err != nil {
+		t.Fatalf("Subscribe: %v", err)
+	}
+	defer cancel()
+	select {
+	case v := <-ch:
+		if got := v.Data.(float64); got != 3.0 {
+			t.Fatalf("initial value = %v, want 3", got)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("no initial value delivered")
+	}
+
+	// A later write fans out to the subscriber.
+	if err := s.Write(ctx, "seq_state", 7.0); err != nil {
+		t.Fatalf("Write 2: %v", err)
+	}
+	select {
+	case v := <-ch:
+		if got := v.Data.(float64); got != 7.0 {
+			t.Fatalf("updated value = %v, want 7", got)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("no update delivered")
+	}
+
+	// ListSignals reports the variable.
+	sigs, err := s.ListSignals(ctx)
+	if err != nil || len(sigs) != 1 || sigs[0].Name != "seq_state" {
+		t.Fatalf("ListSignals = %+v, err %v", sigs, err)
+	}
+
+	// A fresh store over the same dir recovers the last value.
+	s2, err := New(dir)
+	if err != nil {
+		t.Fatalf("reopen: %v", err)
+	}
+	ch2 := make(chan datasource.Value, 1)
+	cancel2, _ := s2.Subscribe(ctx, "seq_state", ch2)
+	defer cancel2()
+	select {
+	case v := <-ch2:
+		if got := v.Data.(float64); got != 7.0 {
+			t.Fatalf("persisted value = %v, want 7", got)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("persisted value not delivered")
+	}
+}

internal/datasource/synthetic/array_graph_test.go

@@ -0,0 +1,222 @@
+package synthetic
+
+import (
+	"context"
+	"log/slog"
+	"math"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/uopi/uopi/internal/broker"
+	"github.com/uopi/uopi/internal/datasource"
+	"github.com/uopi/uopi/internal/dsp"
+)
+
+// evalSampleDef compiles a SignalDef and evaluates it against per-source
+// Samples keyed by source node id, returning the output Sample.
+func evalSampleDef(t *testing.T, def SignalDef, srcVals map[string]dsp.Sample) dsp.Sample {
+	t.Helper()
+	rg, err := compileGraph(def)
+	if err != nil {
+		t.Fatalf("compileGraph: %v", err)
+	}
+	out, err := rg.evalSample(srcVals)
+	if err != nil {
+		t.Fatalf("evalSample: %v", err)
+	}
+	return out
+}
+
+// TestArrayElementwiseChain runs an array source through an elementwise op
+// (gain) and asserts the output stays an array, broadcast per element.
+func TestArrayElementwiseChain(t *testing.T) {
+	def := SignalDef{
+		Name: "scaled",
+		Graph: &Graph{
+			Output: "out",
+			Nodes: []GraphNode{
+				{ID: "a", Kind: "source", DS: "x", Signal: "wave"},
+				{ID: "g", Kind: "op", Op: "gain", Inputs: []string{"a"}, Params: map[string]any{"gain": 2.0}},
+				{ID: "out", Kind: "output", Inputs: []string{"g"}},
+			},
+		},
+	}
+	out := evalSampleDef(t, def, map[string]dsp.Sample{"a": dsp.Array([]float64{1, 2, 3})})
+	if !out.IsArray {
+		t.Fatalf("want array output, got %v", out)
+	}
+	want := []float64{2, 4, 6}
+	for i, v := range want {
+		if out.Arr[i] != v {
+			t.Errorf("scaled[%d]: want %v, got %v", i, v, out.Arr[i])
+		}
+	}
+}
+
+// TestArrayReductionToScalar runs an array source into mean (array→scalar) and
+// asserts a scalar output and an array-output compile type for the producer.
+func TestArrayReductionToScalar(t *testing.T) {
+	def := SignalDef{
+		Name: "avg",
+		Graph: &Graph{
+			Output: "out",
+			Nodes: []GraphNode{
+				{ID: "a", Kind: "source", DS: "x", Signal: "wave"},
+				{ID: "m", Kind: "op", Op: "mean", Inputs: []string{"a"}},
+				{ID: "out", Kind: "output", Inputs: []string{"m"}},
+			},
+		},
+	}
+	out := evalSampleDef(t, def, map[string]dsp.Sample{"a": dsp.Array([]float64{2, 4, 6, 8})})
+	if out.IsArray {
+		t.Fatalf("want scalar output, got array %v", out.Arr)
+	}
+	if math.Abs(out.F-5) > 1e-9 {
+		t.Errorf("mean: want 5, got %v", out.F)
+	}
+}
+
+// TestArrayOutTypeMetadata verifies compileGraph reports an array output type
+// for a pure-elementwise array graph and scalar for a reduction graph.
+func TestArrayOutTypeMetadata(t *testing.T) {
+	arrayGraph := SignalDef{
+		Name: "fftout",
+		Graph: &Graph{
+			Output: "out",
+			Nodes: []GraphNode{
+				{ID: "a", Kind: "source", DS: "x", Signal: "wave"},
+				{ID: "f", Kind: "op", Op: "fft", Inputs: []string{"a"}},
+				{ID: "out", Kind: "output", Inputs: []string{"f"}},
+			},
+		},
+	}
+	rg, err := compileGraph(arrayGraph)
+	if err != nil {
+		t.Fatalf("compileGraph: %v", err)
+	}
+	if rg.outType != dsp.ValArray {
+		t.Errorf("fft graph outType: want ValArray, got %v", rg.outType)
+	}
+
+	reduction := SignalDef{
+		Name: "sumout",
+		Graph: &Graph{
+			Output: "out",
+			Nodes: []GraphNode{
+				{ID: "a", Kind: "source", DS: "x", Signal: "wave"},
+				{ID: "s", Kind: "op", Op: "sum", Inputs: []string{"a"}},
+				{ID: "out", Kind: "output", Inputs: []string{"s"}},
+			},
+		},
+	}
+	rg2, err := compileGraph(reduction)
+	if err != nil {
+		t.Fatalf("compileGraph: %v", err)
+	}
+	if rg2.outType != dsp.ValScalar {
+		t.Errorf("sum graph outType: want ValScalar, got %v", rg2.outType)
+	}
+}
+
+// TestStatefulRejectsArray verifies a stateful op (moving_average) errors when
+// fed an array input at runtime.
+func TestStatefulRejectsArray(t *testing.T) {
+	def := SignalDef{
+		Name: "ma",
+		Graph: &Graph{
+			Output: "out",
+			Nodes: []GraphNode{
+				{ID: "a", Kind: "source", DS: "x", Signal: "wave"},
+				{ID: "m", Kind: "op", Op: "moving_average", Inputs: []string{"a"}, Params: map[string]any{"window": 3.0}},
+				{ID: "out", Kind: "output", Inputs: []string{"m"}},
+			},
+		},
+	}
+	rg, err := compileGraph(def)
+	if err != nil {
+		t.Fatalf("compileGraph: %v", err)
+	}
+	if _, err := rg.evalSample(map[string]dsp.Sample{"a": dsp.Array([]float64{1, 2, 3})}); err == nil {
+		t.Error("expected moving_average to reject an array input")
+	}
+}
+
+// TestSubscribeArrayPassthrough is an end-to-end check that a synthetic with an
+// array-valued source and an elementwise op emits a []float64 over the broker,
+// and that GetMetadata reports the waveform type.
+func TestSubscribeArrayPassthrough(t *testing.T) {
+	log := slog.New(slog.NewTextHandler(os.Stderr, nil))
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	base := time.Date(2026, 6, 19, 10, 0, 0, 0, time.UTC)
+	src := &seqSource{name: "src", seq: []datasource.Value{
+		{Timestamp: base.Add(1 * time.Second), Data: []float64{1, 2, 3}, Quality: datasource.QualityGood},
+		{Timestamp: base.Add(2 * time.Second), Data: []float64{4, 5, 6}, Quality: datasource.QualityGood},
+	}}
+
+	brk := broker.New(ctx, log)
+	brk.Register(src)
+	syn := New(t.TempDir(), brk, log)
+	if err := syn.Connect(ctx); err != nil {
+		t.Fatal(err)
+	}
+	// gain x2 elementwise keeps the value an array.
+	if err := syn.AddSignal(SignalDef{
+		Name: "scaled",
+		Graph: &Graph{Output: "out", Nodes: []GraphNode{
+			{ID: "a", Kind: "source", DS: "src", Signal: "x"},
+			{ID: "g", Kind: "op", Op: "gain", Inputs: []string{"a"}, Params: map[string]any{"gain": 2.0}},
+			{ID: "out", Kind: "output", Inputs: []string{"g"}},
+		}},
+	}); err != nil {
+		t.Fatal(err)
+	}
+	// An fft-based signal has a statically-known array output type (the source's
+	// runtime type need not be known), so its metadata reports the waveform type.
+	if err := syn.AddSignal(SignalDef{
+		Name: "spectrum",
+		Graph: &Graph{Output: "out", Nodes: []GraphNode{
+			{ID: "a", Kind: "source", DS: "src", Signal: "x"},
+			{ID: "f", Kind: "op", Op: "fft", Inputs: []string{"a"}},
+			{ID: "out", Kind: "output", Inputs: []string{"f"}},
+		}},
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	meta, err := syn.GetMetadata(ctx, "spectrum")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if meta.Type != datasource.TypeFloat64Array {
+		t.Errorf("metadata type: want TypeFloat64Array, got %v", meta.Type)
+	}
+
+	ch := make(chan datasource.Value, 8)
+	if _, err := syn.Subscribe(ctx, "scaled", ch); err != nil {
+		t.Fatal(err)
+	}
+
+	want := [][]float64{{2, 4, 6}, {8, 10, 12}}
+	for i, w := range want {
+		select {
+		case v := <-ch:
+			arr, ok := v.Data.([]float64)
+			if !ok {
+				t.Fatalf("emit #%d: want []float64, got %T", i, v.Data)
+			}
+			if len(arr) != len(w) {
+				t.Fatalf("emit #%d: want len %d, got %d", i, len(w), len(arr))
+			}
+			for k, val := range w {
+				if arr[k] != val {
+					t.Errorf("emit #%d [%d]: want %v, got %v", i, k, val, arr[k])
+				}
+			}
+		case <-time.After(2 * time.Second):
+			t.Fatalf("timeout waiting for emit #%d", i)
+		}
+	}
+}

internal/datasource/synthetic/definition.go

@@ -9,6 +9,7 @@ type SignalDef struct {
 	Signal   string        `json:"signal"`  // upstream signal name (or "" for constant)
 	Inputs   []InputRef    `json:"inputs"`  // alternative multi-input format
 	Pipeline []NodeDef     `json:"pipeline"` // ordered list of DSP nodes
+	Graph    *Graph        `json:"graph,omitempty"` // DAG form (preferred when present)
 	Meta     MetaOverride  `json:"meta"`    // optional metadata overrides
 
 	// Visibility controls who sees this signal in the signal tree:
@@ -20,6 +21,12 @@ type SignalDef struct {
 	Visibility string `json:"visibility,omitempty"`
 	Owner      string `json:"owner,omitempty"` // creator identity (stamped server-side)
 	Panel      string `json:"panel,omitempty"` // bound interface id for "panel" visibility
+
+	// Version and Tag implement git-style revisioning. Version is bumped on
+	// every UpdateSignal; superseded revisions are kept as backup files. Tag is
+	// an optional human label for a revision (e.g. "restored from v3").
+	Version int    `json:"version,omitempty"`
+	Tag     string `json:"tag,omitempty"`
 }
 
 // InputRef names one upstream signal used as input to the pipeline.
@@ -34,6 +41,37 @@ type NodeDef struct {
 	Params map[string]any `json:"params,omitempty"`
 }
 
+// Graph is the DAG form of a synthetic signal: a set of nodes (sources, ops and
+// one output) wired together by explicit per-node ordered input lists. It
+// supersedes the linear Inputs+Pipeline form: when SignalDef.Graph is set it is
+// authoritative; otherwise the legacy linear fields are converted into an
+// equivalent graph at load time (see toGraph).
+type Graph struct {
+	Nodes  []GraphNode `json:"nodes"`
+	Output string      `json:"output"` // id of the output node
+}
+
+// GraphNode is one node in a Graph.
+//
+//	kind=="source": carries DS+Signal; has no Inputs (a graph root).
+//	kind=="op":     carries Op + Params; Inputs lists upstream node IDs in the
+//	                order the op receives them (input 0, 1, … e.g. a−b, a÷b).
+//	kind=="output": Inputs has a single upstream node whose value is the result.
+//
+// X/Y are the editor layout coordinates, persisted so a reloaded graph keeps its
+// shape; they have no effect on evaluation.
+type GraphNode struct {
+	ID     string         `json:"id"`
+	Kind   string         `json:"kind"`
+	Op     string         `json:"op,omitempty"`
+	Params map[string]any `json:"params,omitempty"`
+	DS     string         `json:"ds,omitempty"`
+	Signal string         `json:"signal,omitempty"`
+	Inputs []string       `json:"inputs,omitempty"`
+	X      float64        `json:"x,omitempty"`
+	Y      float64        `json:"y,omitempty"`
+}
+
 // MetaOverride allows the synthetic signal to override display metadata.
 type MetaOverride struct {
 	Unit        string  `json:"unit,omitempty"`

internal/datasource/synthetic/dsp_bridge.go

@@ -38,21 +38,32 @@ func stringParam(params map[string]any, key string) string {
 	return s
 }
 
-// BuildPipeline converts a []NodeDef (from JSON) into a []dsp.Node ready for
+// stringSliceParam extracts a []string from params; JSON arrays decode to []any,
-// execution. JSON numbers are float64, so all numeric params are handled as
+// so each element is coerced via its string value. Returns nil if missing.
-// float64 regardless of the final type needed.
+func stringSliceParam(params map[string]any, key string) []string {
-func BuildPipeline(defs []NodeDef) ([]dsp.Node, error) {
+	if params == nil {
-	nodes := make([]dsp.Node, 0, len(defs))
+		return nil
-	for i, d := range defs {
-		n, err := buildNode(d)
-		if err != nil {
-			return nil, fmt.Errorf("pipeline node %d (%q): %w", i, d.Type, err)
 	}
-		nodes = append(nodes, n)
+	v, ok := params[key]
+	if !ok {
+		return nil
 	}
-	return nodes, nil
+	arr, ok := v.([]any)
+	if !ok {
+		return nil
+	}
+	out := make([]string, 0, len(arr))
+	for _, e := range arr {
+		if s, ok := e.(string); ok && s != "" {
+			out = append(out, s)
+		}
+	}
+	return out
 }
 
+// buildNode converts a single NodeDef (from JSON) into a dsp.Node ready for
+// execution. JSON numbers are float64, so all numeric params are handled as
+// float64 regardless of the final type needed.
 func buildNode(d NodeDef) (dsp.Node, error) {
 	p := d.Params
 	switch d.Type {
@@ -100,7 +111,7 @@ func buildNode(d NodeDef) (dsp.Node, error) {
 		}, nil
 
 	case "expr":
-		return &dsp.ExprNode{Expr: stringParam(p, "expr")}, nil
+		return &dsp.ExprNode{Expr: stringParam(p, "expr"), Vars: stringSliceParam(p, "vars")}, nil
 
 	case "lowpass":
 		order := int(floatParam(p, "order"))
@@ -113,7 +124,31 @@ func buildNode(d NodeDef) (dsp.Node, error) {
 		}, nil
 
 	case "lua":
-		return &dsp.LuaNode{Script: stringParam(p, "script")}, nil
+		return &dsp.LuaNode{Script: stringParam(p, "script"), Vars: stringSliceParam(p, "vars")}, nil
+
+	case "index":
+		return &dsp.IndexNode{I: int(floatParam(p, "i"))}, nil
+
+	case "slice":
+		return &dsp.SliceNode{Start: int(floatParam(p, "start")), End: int(floatParam(p, "end"))}, nil
+
+	case "sum":
+		return &dsp.SumNode{}, nil
+
+	case "mean":
+		return &dsp.MeanNode{}, nil
+
+	case "min":
+		return &dsp.MinNode{}, nil
+
+	case "max":
+		return &dsp.MaxNode{}, nil
+
+	case "length":
+		return &dsp.LengthNode{}, nil
+
+	case "fft":
+		return &dsp.FFTNode{}, nil
 
 	default:
 		return nil, fmt.Errorf("unknown node type %q", d.Type)

internal/datasource/synthetic/graph.go

@@ -0,0 +1,263 @@
+package synthetic
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/uopi/uopi/internal/broker"
+	"github.com/uopi/uopi/internal/dsp"
+)
+
+// runtimeGraph is the executable form of a synthetic signal's DAG. Nodes are
+// held in topological order so a single forward pass computes every value with
+// each node's inputs already resolved. Op-node state maps persist across
+// evaluations (for stateful nodes like moving_average / lua).
+type runtimeGraph struct {
+	order    []*rtNode    // topological order (sources first, output last)
+	sources  []rtSource   // source nodes, in topological order
+	outputID string       // id of the output node
+	outType  dsp.ValType  // best-effort output type (scalar/array/unknown)
+}
+
+type rtNode struct {
+	id     string
+	kind   string         // source | op | output
+	op     dsp.Node       // set for kind==op
+	state  map[string]any // persistent per-node state (op only)
+	inputs []string       // upstream node ids, in input order
+}
+
+type rtSource struct {
+	id  string
+	ref broker.SignalRef
+}
+
+// sourceRefs returns the broker references for every source node, in a stable
+// order matching rg.sources.
+func (rg *runtimeGraph) sourceRefs() []broker.SignalRef {
+	refs := make([]broker.SignalRef, len(rg.sources))
+	for i, s := range rg.sources {
+		refs[i] = s.ref
+	}
+	return refs
+}
+
+// evalSample computes the output Sample (scalar or array) given the latest
+// value for each source node (keyed by source node id). Nodes are visited in
+// topological order so every input is present by the time a node is processed.
+//
+// Op dispatch:
+//   - ArrayNode ops (reductions/producers) run natively on Samples.
+//   - stateless elementwise ops broadcast over array inputs.
+//   - stateful ops (filters) and lua are scalar-only; an array input errors,
+//     since their per-evaluation state cannot be split across array lanes.
+func (rg *runtimeGraph) evalSample(sourceVals map[string]dsp.Sample) (dsp.Sample, error) {
+	vals := make(map[string]dsp.Sample, len(rg.order))
+	for id, v := range sourceVals {
+		vals[id] = v
+	}
+	for _, n := range rg.order {
+		switch n.kind {
+		case "op":
+			in := make([]dsp.Sample, len(n.inputs))
+			for i, id := range n.inputs {
+				in[i] = vals[id]
+			}
+			r, err := evalOp(n, in)
+			if err != nil {
+				return dsp.Sample{}, fmt.Errorf("node %s (%s): %w", n.id, n.op.Type(), err)
+			}
+			vals[n.id] = r
+		case "output":
+			if len(n.inputs) > 0 {
+				vals[n.id] = vals[n.inputs[0]]
+			}
+		}
+	}
+	return vals[rg.outputID], nil
+}
+
+// evalOp runs a single op node over its Sample inputs, choosing the right
+// execution path for the node type.
+func evalOp(n *rtNode, in []dsp.Sample) (dsp.Sample, error) {
+	if an, ok := n.op.(dsp.ArrayNode); ok {
+		return an.ProcessSample(in, n.state)
+	}
+	if dsp.StatelessElementwise(n.op.Type()) {
+		return dsp.ApplyElementwise(n.op, in, n.state)
+	}
+	// Stateful / lua: scalar-only.
+	row := make([]float64, len(in))
+	for i, s := range in {
+		if s.IsArray {
+			return dsp.Sample{}, fmt.Errorf("does not accept an array input")
+		}
+		row[i] = s.F
+	}
+	r, err := n.op.Process(row, n.state)
+	if err != nil {
+		return dsp.Sample{}, err
+	}
+	return dsp.Scalar(r), nil
+}
+
+// eval is the scalar wrapper around evalSample, kept so callers and tests that
+// deal purely in float64 (legacy linear graphs, scalar sources) are unchanged.
+func (rg *runtimeGraph) eval(sourceVals map[string]float64) (float64, error) {
+	sv := make(map[string]dsp.Sample, len(sourceVals))
+	for id, v := range sourceVals {
+		sv[id] = dsp.Scalar(v)
+	}
+	out, err := rg.evalSample(sv)
+	if err != nil {
+		return 0, err
+	}
+	return out.F, nil
+}
+
+// compileGraph converts a SignalDef into an executable runtimeGraph. When the
+// def carries an explicit Graph it is used directly; otherwise the legacy
+// Inputs+Pipeline form is converted to an equivalent linear graph (see toGraph).
+func compileGraph(def SignalDef) (*runtimeGraph, error) {
+	g := toGraph(def)
+	if g == nil || len(g.Nodes) == 0 {
+		return &runtimeGraph{}, nil
+	}
+	order, err := topoOrder(g)
+	if err != nil {
+		return nil, err
+	}
+	rg := &runtimeGraph{outputID: g.Output}
+	// nodeType tracks each node's best-effort output type for static
+	// propagation. Sources are unknown at compile time (their real type is
+	// only known once data flows), so type errors here are advisory; runtime
+	// Sample typing is authoritative.
+	nodeType := make(map[string]dsp.ValType, len(order))
+	for _, gn := range order {
+		switch gn.Kind {
+		case "source":
+			rg.sources = append(rg.sources, rtSource{id: gn.ID, ref: broker.SignalRef{DS: gn.DS, Name: gn.Signal}})
+			nodeType[gn.ID] = dsp.ValUnknown
+		case "op":
+			node, err := buildNode(NodeDef{Type: gn.Op, Params: gn.Params})
+			if err != nil {
+				return nil, fmt.Errorf("node %q: %w", gn.ID, err)
+			}
+			inTypes := make([]dsp.ValType, len(gn.Inputs))
+			for i, id := range gn.Inputs {
+				inTypes[i] = nodeType[id]
+			}
+			ot, terr := dsp.OpOutputType(gn.Op, inTypes)
+			if terr != nil {
+				return nil, fmt.Errorf("node %q: %w", gn.ID, terr)
+			}
+			nodeType[gn.ID] = ot
+			rg.order = append(rg.order, &rtNode{id: gn.ID, kind: "op", op: node, state: map[string]any{}, inputs: gn.Inputs})
+		case "output":
+			rg.outputID = gn.ID
+			if len(gn.Inputs) > 0 {
+				nodeType[gn.ID] = nodeType[gn.Inputs[0]]
+			}
+			rg.order = append(rg.order, &rtNode{id: gn.ID, kind: "output", inputs: gn.Inputs})
+		default:
+			return nil, fmt.Errorf("node %q: unknown kind %q", gn.ID, gn.Kind)
+		}
+	}
+	rg.outType = nodeType[rg.outputID]
+	return rg, nil
+}
+
+// topoOrder returns the graph's nodes in a topological (dependency-first) order,
+// treating each node's Inputs as its predecessors. It errors on dangling input
+// references or cycles.
+func topoOrder(g *Graph) ([]GraphNode, error) {
+	byID := make(map[string]GraphNode, len(g.Nodes))
+	for _, n := range g.Nodes {
+		byID[n.ID] = n
+	}
+	indeg := make(map[string]int, len(g.Nodes))
+	succ := make(map[string][]string, len(g.Nodes))
+	for _, n := range g.Nodes {
+		if _, ok := indeg[n.ID]; !ok {
+			indeg[n.ID] = 0
+		}
+		for _, in := range n.Inputs {
+			if _, ok := byID[in]; !ok {
+				return nil, fmt.Errorf("node %q references unknown input %q", n.ID, in)
+			}
+			indeg[n.ID]++
+			succ[in] = append(succ[in], n.ID)
+		}
+	}
+	// Seed the queue with roots, preserving the node slice order for determinism.
+	queue := make([]string, 0, len(g.Nodes))
+	for _, n := range g.Nodes {
+		if indeg[n.ID] == 0 {
+			queue = append(queue, n.ID)
+		}
+	}
+	order := make([]GraphNode, 0, len(g.Nodes))
+	for len(queue) > 0 {
+		id := queue[0]
+		queue = queue[1:]
+		order = append(order, byID[id])
+		for _, s := range succ[id] {
+			indeg[s]--
+			if indeg[s] == 0 {
+				queue = append(queue, s)
+			}
+		}
+	}
+	if len(order) != len(g.Nodes) {
+		return nil, errors.New("graph contains a cycle")
+	}
+	return order, nil
+}
+
+// toGraph returns the DAG for a SignalDef. If def.Graph is set it is returned
+// as-is. Otherwise the legacy linear form is converted: each input signal
+// becomes a source node, the pipeline becomes a chain of op nodes (the first op
+// receiving every source, each later op the previous op's output), terminated by
+// an output node. With no pipeline the output takes the first source directly,
+// matching the old runPipeline behaviour.
+func toGraph(def SignalDef) *Graph {
+	if def.Graph != nil && len(def.Graph.Nodes) > 0 {
+		return def.Graph
+	}
+
+	inputs := def.Inputs
+	if len(inputs) == 0 && def.DS != "" && def.Signal != "" {
+		inputs = []InputRef{{DS: def.DS, Signal: def.Signal}}
+	}
+
+	nodes := make([]GraphNode, 0, len(inputs)+len(def.Pipeline)+1)
+	srcIDs := make([]string, 0, len(inputs))
+	for i, inp := range inputs {
+		id := fmt.Sprintf("s%d", i)
+		nodes = append(nodes, GraphNode{ID: id, Kind: "source", DS: inp.DS, Signal: inp.Signal})
+		srcIDs = append(srcIDs, id)
+	}
+
+	opIDs := make([]string, 0, len(def.Pipeline))
+	for i, nd := range def.Pipeline {
+		id := fmt.Sprintf("p%d", i)
+		var ins []string
+		if i == 0 {
+			ins = srcIDs
+		} else {
+			ins = []string{opIDs[i-1]}
+		}
+		nodes = append(nodes, GraphNode{ID: id, Kind: "op", Op: nd.Type, Params: nd.Params, Inputs: ins})
+		opIDs = append(opIDs, id)
+	}
+
+	var outInputs []string
+	if len(opIDs) > 0 {
+		outInputs = []string{opIDs[len(opIDs)-1]}
+	} else if len(srcIDs) > 0 {
+		outInputs = []string{srcIDs[0]}
+	}
+	nodes = append(nodes, GraphNode{ID: "out", Kind: "output", Inputs: outInputs})
+
+	return &Graph{Nodes: nodes, Output: "out"}
+}

internal/datasource/synthetic/graph_test.go

@@ -0,0 +1,130 @@
+package synthetic
+
+import (
+	"math"
+	"testing"
+)
+
+// evalDef compiles a SignalDef and evaluates it against per-source values keyed
+// by source node id.
+func evalDef(t *testing.T, def SignalDef, srcVals map[string]float64) float64 {
+	t.Helper()
+	rg, err := compileGraph(def)
+	if err != nil {
+		t.Fatalf("compileGraph: %v", err)
+	}
+	out, err := rg.eval(srcVals)
+	if err != nil {
+		t.Fatalf("eval: %v", err)
+	}
+	return out
+}
+
+// TestGraphMultiInputDAG verifies that an intermediate op can take two
+// independently-wired sources — the capability the old linear pipeline lacked.
+func TestGraphMultiInputDAG(t *testing.T) {
+	def := SignalDef{
+		Name: "diff",
+		Graph: &Graph{
+			Output: "out",
+			Nodes: []GraphNode{
+				{ID: "a", Kind: "source", DS: "x", Signal: "left"},
+				{ID: "b", Kind: "source", DS: "x", Signal: "right"},
+				{ID: "sub", Kind: "op", Op: "subtract", Inputs: []string{"a", "b"}},
+				{ID: "out", Kind: "output", Inputs: []string{"sub"}},
+			},
+		},
+	}
+	got := evalDef(t, def, map[string]float64{"a": 10, "b": 3})
+	if got != 7 {
+		t.Errorf("subtract DAG: want 7, got %v", got)
+	}
+}
+
+// TestGraphExprNamedInputs verifies expr nodes bind arbitrary named inputs in
+// wired order.
+func TestGraphExprNamedInputs(t *testing.T) {
+	def := SignalDef{
+		Name: "formula",
+		Graph: &Graph{
+			Output: "out",
+			Nodes: []GraphNode{
+				{ID: "a", Kind: "source", DS: "x", Signal: "p"},
+				{ID: "b", Kind: "source", DS: "x", Signal: "q"},
+				{ID: "e", Kind: "op", Op: "expr", Inputs: []string{"a", "b"},
+					Params: map[string]any{"expr": "price * qty", "vars": []any{"price", "qty"}}},
+				{ID: "out", Kind: "output", Inputs: []string{"e"}},
+			},
+		},
+	}
+	got := evalDef(t, def, map[string]float64{"a": 4, "b": 2.5})
+	if math.Abs(got-10) > 1e-9 {
+		t.Errorf("expr named inputs: want 10, got %v", got)
+	}
+}
+
+// TestGraphFanInToExpr exercises a non-trivial DAG: two ops feeding one expr.
+func TestGraphFanInToExpr(t *testing.T) {
+	def := SignalDef{
+		Name: "combo",
+		Graph: &Graph{
+			Output: "out",
+			Nodes: []GraphNode{
+				{ID: "a", Kind: "source", DS: "x", Signal: "p"},
+				{ID: "b", Kind: "source", DS: "x", Signal: "q"},
+				{ID: "g", Kind: "op", Op: "gain", Inputs: []string{"a"}, Params: map[string]any{"gain": 2.0}},
+				{ID: "o", Kind: "op", Op: "offset", Inputs: []string{"b"}, Params: map[string]any{"offset": 1.0}},
+				{ID: "e", Kind: "op", Op: "expr", Inputs: []string{"g", "o"}, Params: map[string]any{"expr": "a + b"}},
+				{ID: "out", Kind: "output", Inputs: []string{"e"}},
+			},
+		},
+	}
+	// g = 5*2 = 10 ; o = 4+1 = 5 ; a+b = 15
+	got := evalDef(t, def, map[string]float64{"a": 5, "b": 4})
+	if math.Abs(got-15) > 1e-9 {
+		t.Errorf("fan-in DAG: want 15, got %v", got)
+	}
+}
+
+// TestGraphLegacyConversion verifies the linear Inputs+Pipeline form still
+// evaluates correctly via the graph runtime.
+func TestGraphLegacyConversion(t *testing.T) {
+	def := SignalDef{
+		Name:     "legacy",
+		DS:       "x",
+		Signal:   "p",
+		Pipeline: []NodeDef{{Type: "gain", Params: map[string]any{"gain": 3.0}}},
+	}
+	rg, err := compileGraph(def)
+	if err != nil {
+		t.Fatalf("compileGraph: %v", err)
+	}
+	if len(rg.sources) != 1 {
+		t.Fatalf("want 1 source, got %d", len(rg.sources))
+	}
+	got, err := rg.eval(map[string]float64{rg.sources[0].id: 4})
+	if err != nil {
+		t.Fatalf("eval: %v", err)
+	}
+	if got != 12 {
+		t.Errorf("legacy gain: want 12, got %v", got)
+	}
+}
+
+// TestGraphCycleRejected ensures a cyclic graph is refused at compile time.
+func TestGraphCycleRejected(t *testing.T) {
+	def := SignalDef{
+		Name: "cyclic",
+		Graph: &Graph{
+			Output: "out",
+			Nodes: []GraphNode{
+				{ID: "a", Kind: "op", Op: "gain", Inputs: []string{"b"}, Params: map[string]any{"gain": 1.0}},
+				{ID: "b", Kind: "op", Op: "gain", Inputs: []string{"a"}, Params: map[string]any{"gain": 1.0}},
+				{ID: "out", Kind: "output", Inputs: []string{"a"}},
+			},
+		},
+	}
+	if _, err := compileGraph(def); err == nil {
+		t.Error("expected cycle to be rejected")
+	}
+}

internal/datasource/synthetic/synthetic.go

@@ -21,8 +21,7 @@ const definitionsFile = "synthetic.json"
 // signalState holds everything needed to run one synthetic signal.
 type signalState struct {
 	def SignalDef
-	nodes  []dsp.Node
+	rg  *runtimeGraph // compiled DAG; op-node state persists across evaluations
-	states []map[string]any // one map per node, persistent across calls
 
 	// cancel stops the goroutine driving this signal.
 	cancel context.CancelFunc
@@ -80,7 +79,7 @@ func (s *Synthetic) ListSignals(_ context.Context) ([]datasource.Metadata, error
 
 	out := make([]datasource.Metadata, 0, len(s.signals))
 	for _, st := range s.signals {
-		out = append(out, defToMetadata(st.def))
+		out = append(out, defToMetadata(st.def, outTypeOf(st)))
 	}
 	return out, nil
 }
@@ -95,7 +94,7 @@ func (s *Synthetic) FilteredMetadata(keep func(SignalDef) bool) []datasource.Met
 	out := make([]datasource.Metadata, 0, len(s.signals))
 	for _, st := range s.signals {
 		if keep(st.def) {
-			out = append(out, defToMetadata(st.def))
+			out = append(out, defToMetadata(st.def, outTypeOf(st)))
 		}
 	}
 	return out
@@ -110,7 +109,7 @@ func (s *Synthetic) GetMetadata(_ context.Context, signal string) (datasource.Me
 	if !ok {
 		return datasource.Metadata{}, datasource.ErrNotFound
 	}
-	return defToMetadata(st.def), nil
+	return defToMetadata(st.def, outTypeOf(st)), nil
 }
 
 // Subscribe registers ch to receive computed values for the named signal.
@@ -123,19 +122,25 @@ func (s *Synthetic) Subscribe(ctx context.Context, signal string, ch chan<- data
 		return nil, datasource.ErrNotFound
 	}
 
-	// Collect the upstream references for this signal.
+	// Collect the source node references for this signal's DAG.
-	refs := upstreamRefs(st.def)
+	refs := st.rg.sourceRefs()
 	if len(refs) == 0 {
 		return nil, fmt.Errorf("synthetic: signal %q has no upstream inputs", signal)
 	}
+	// Source node ids, index-aligned with refs, so updates map to graph inputs.
+	srcIDs := make([]string, len(st.rg.sources))
+	for i, s := range st.rg.sources {
+		srcIDs[i] = s.id
+	}
 
 	ctx, cancel := context.WithCancel(ctx)
 
 	go func() {
 		defer cancel()
 
-		// Latest value per upstream input index.
+		// Latest value and timestamp per source node id.
-		latest := make([]float64, len(refs))
+		latest := make(map[string]dsp.Sample, len(refs))
+		latestTs := make([]time.Time, len(refs))
 		ready := make([]bool, len(refs))
 
 		// Subscribe to every upstream ref via the broker.
@@ -159,7 +164,7 @@ func (s *Synthetic) Subscribe(ctx context.Context, signal string, ch chan<- data
 							if !ok {
 								return
 							}
-							val := toFloat64(u.Value.Data)
+							val := toSample(u.Value.Data)
 							select {
 							case updateCh <- indexedUpdate{idx: idx, val: val, ts: u.Value.Timestamp}:
 							default:
@@ -184,7 +189,8 @@ func (s *Synthetic) Subscribe(ctx context.Context, signal string, ch chan<- data
 				return
 
 			case upd := <-updateCh:
-				latest[upd.idx] = upd.val
+				latest[srcIDs[upd.idx]] = upd.val
+				latestTs[upd.idx] = upd.ts
 				ready[upd.idx] = true
 
 				// Only compute once we have at least one value for every input.
@@ -199,7 +205,19 @@ func (s *Synthetic) Subscribe(ctx context.Context, signal string, ch chan<- data
 					continue
 				}
 
-				// Run the pipeline.
+				// The output is computed from the latest value of every input, so
+				// its timestamp is the most recent contributing sample time. Using
+				// the triggering update's timestamp instead would drag the output
+				// back in time whenever a slow/stale input fired, producing
+				// non-monotonic or duplicated timestamps on plots.
+				outTs := latestTs[0]
+				for _, ts := range latestTs[1:] {
+					if ts.After(outTs) {
+						outTs = ts
+					}
+				}
+
+				// Evaluate the DAG.
 				s.mu.RLock()
 				cur, stillExists := s.signals[signal]
 				s.mu.RUnlock()
@@ -207,15 +225,15 @@ func (s *Synthetic) Subscribe(ctx context.Context, signal string, ch chan<- data
 					return
 				}
 
-				result, err := runPipeline(cur.nodes, cur.states, latest)
+				result, err := cur.rg.evalSample(latest)
 				if err != nil {
 					s.log.Warn("synthetic: pipeline error", "signal", signal, "err", err)
 					continue
 				}
 
 				v := datasource.Value{
-					Timestamp: upd.ts,
+					Timestamp: outTs,
-					Data:      result,
+					Data:      result.AsAny(),
 					Quality:   datasource.QualityGood,
 				}
 				select {
@@ -245,10 +263,13 @@ func (s *Synthetic) AddSignal(def SignalDef) error {
 	if def.Name == "" {
 		return errors.New("signal name must not be empty")
 	}
+	if def.Version < 1 {
+		def.Version = 1
+	}
 
-	nodes, err := BuildPipeline(def.Pipeline)
+	rg, err := compileGraph(def)
 	if err != nil {
-		return fmt.Errorf("build pipeline: %w", err)
+		return fmt.Errorf("compile graph: %w", err)
 	}
 
 	s.mu.Lock()
@@ -257,16 +278,7 @@ func (s *Synthetic) AddSignal(def SignalDef) error {
 		return fmt.Errorf("signal %q already exists", def.Name)
 	}
 
-	states := make([]map[string]any, len(nodes))
+	st := &signalState{def: def, rg: rg}
-	for i := range states {
-		states[i] = make(map[string]any)
-	}
-
-	st := &signalState{
-		def:    def,
-		nodes:  nodes,
-		states: states,
-	}
 	s.signals[def.Name] = st
 	s.mu.Unlock()
 
@@ -320,14 +332,9 @@ func (s *Synthetic) UpdateSignal(def SignalDef) error {
 		return errors.New("signal name must not be empty")
 	}
 
-	nodes, err := BuildPipeline(def.Pipeline)
+	rg, err := compileGraph(def)
 	if err != nil {
-		return fmt.Errorf("build pipeline: %w", err)
+		return fmt.Errorf("compile graph: %w", err)
-	}
-
-	states := make([]map[string]any, len(nodes))
-	for i := range states {
-		states[i] = make(map[string]any)
 	}
 
 	s.mu.Lock()
@@ -336,10 +343,20 @@ func (s *Synthetic) UpdateSignal(def SignalDef) error {
 		s.mu.Unlock()
 		return datasource.ErrNotFound
 	}
+	// Preserve the superseded revision as a backup and bump the version.
+	oldDef := old.def
+	if oldDef.Version < 1 {
+		oldDef.Version = 1
+	}
+	if err := s.backupVersion(oldDef); err != nil {
+		s.mu.Unlock()
+		return fmt.Errorf("back up revision: %w", err)
+	}
+	def.Version = oldDef.Version + 1
 	if old.cancel != nil {
 		old.cancel()
 	}
-	s.signals[def.Name] = &signalState{def: def, nodes: nodes, states: states}
+	s.signals[def.Name] = &signalState{def: def, rg: rg}
 	s.mu.Unlock()
 
 	if err := s.saveDefs(); err != nil {
@@ -402,78 +419,33 @@ func (s *Synthetic) saveDefs() error {
 	return os.WriteFile(s.defsFilePath(), data, 0o644)
 }
 
-// startSignal builds the pipeline for def and registers the signalState.
+// startSignal compiles the DAG for def and registers the signalState.
 // The actual goroutines are started lazily by Subscribe.
 func (s *Synthetic) startSignal(def SignalDef) error {
-	nodes, err := BuildPipeline(def.Pipeline)
+	rg, err := compileGraph(def)
 	if err != nil {
-		return fmt.Errorf("build pipeline for %q: %w", def.Name, err)
+		return fmt.Errorf("compile graph for %q: %w", def.Name, err)
-	}
-
-	states := make([]map[string]any, len(nodes))
-	for i := range states {
-		states[i] = make(map[string]any)
 	}
 
 	s.mu.Lock()
-	s.signals[def.Name] = &signalState{
+	s.signals[def.Name] = &signalState{def: def, rg: rg}
-		def:    def,
-		nodes:  nodes,
-		states: states,
-	}
 	s.mu.Unlock()
 
 	s.log.Info("synthetic: signal registered", "name", def.Name)
 	return nil
 }
 
-// runPipeline executes all nodes in sequence. The output of node N becomes
+// defToMetadata converts a SignalDef into a datasource.Metadata. outType is the
-// input[0] of node N+1. For the first node, inputs is the full upstream slice.
+// compiled graph's best-effort output type; an array output is reported as a
-func runPipeline(nodes []dsp.Node, states []map[string]any, inputs []float64) (float64, error) {
+// waveform (TypeFloat64Array) so widgets can pick a compatible view.
-	if len(nodes) == 0 {
+func defToMetadata(def SignalDef, outType dsp.ValType) datasource.Metadata {
-		if len(inputs) == 0 {
+	dt := datasource.TypeFloat64
-			return 0, nil
+	if outType == dsp.ValArray {
+		dt = datasource.TypeFloat64Array
 	}
-		return inputs[0], nil
-	}
-
-	// First node receives all upstream inputs.
-	cur := inputs
-	var result float64
-	var err error
-
-	for i, node := range nodes {
-		result, err = node.Process(cur, states[i])
-		if err != nil {
-			return 0, fmt.Errorf("node %d (%s): %w", i, node.Type(), err)
-		}
-		// Subsequent nodes receive only the single output of the previous node.
-		cur = []float64{result}
-	}
-	return result, nil
-}
-
-// upstreamRefs returns the broker.SignalRef list for a SignalDef.
-// If Inputs is set, those take precedence; otherwise DS+Signal is used.
-func upstreamRefs(def SignalDef) []broker.SignalRef {
-	if len(def.Inputs) > 0 {
-		refs := make([]broker.SignalRef, len(def.Inputs))
-		for i, inp := range def.Inputs {
-			refs[i] = broker.SignalRef{DS: inp.DS, Name: inp.Signal}
-		}
-		return refs
-	}
-	if def.DS != "" && def.Signal != "" {
-		return []broker.SignalRef{{DS: def.DS, Name: def.Signal}}
-	}
-	return nil
-}
-
-// defToMetadata converts a SignalDef into a datasource.Metadata.
-func defToMetadata(def SignalDef) datasource.Metadata {
 	return datasource.Metadata{
 		Name:        def.Name,
-		Type:        datasource.TypeFloat64,
+		Type:        dt,
 		Unit:        def.Meta.Unit,
 		Description: def.Meta.Description,
 		DisplayLow:  def.Meta.DisplayLow,
@@ -482,7 +454,38 @@ func defToMetadata(def SignalDef) datasource.Metadata {
 	}
 }
 
-// toFloat64 coerces any numeric value from a datasource.Value.Data to float64.
+// outTypeOf returns the compiled output type for a signal state, or unknown.
+func outTypeOf(st *signalState) dsp.ValType {
+	if st == nil || st.rg == nil {
+		return dsp.ValUnknown
+	}
+	return st.rg.outType
+}
+
+// toSample coerces a datasource.Value.Data into a dsp.Sample: arrays become
+// array Samples (waveforms), everything else a scalar Sample.
+func toSample(v any) dsp.Sample {
+	switch val := v.(type) {
+	case []float64:
+		return dsp.Array(val)
+	case []float32:
+		out := make([]float64, len(val))
+		for i, e := range val {
+			out[i] = float64(e)
+		}
+		return dsp.Array(out)
+	case []int:
+		out := make([]float64, len(val))
+		for i, e := range val {
+			out[i] = float64(e)
+		}
+		return dsp.Array(out)
+	default:
+		return dsp.Scalar(toFloat64(v))
+	}
+}
+
+// toFloat64 coerces any numeric scalar value from a datasource.Value.Data to float64.
 func toFloat64(v any) float64 {
 	switch val := v.(type) {
 	case float64:
@@ -508,6 +511,6 @@ func toFloat64(v any) float64 {
 // indexedUpdate carries a value from one upstream goroutine to the pipeline runner.
 type indexedUpdate struct {
 	idx int
-	val float64
+	val dsp.Sample
 	ts  time.Time
 }

internal/datasource/synthetic/timestamp_test.go

@@ -0,0 +1,154 @@
+package synthetic
+
+import (
+	"context"
+	"log/slog"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/uopi/uopi/internal/broker"
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+// seqSource is a test DataSource that emits a fixed sequence of values, each
+// carrying its own timestamp, so tests can control upstream sample times.
+type seqSource struct {
+	name string
+	seq  []datasource.Value
+}
+
+func (s *seqSource) Name() string                                          { return s.name }
+func (s *seqSource) Connect(context.Context) error                         { return nil }
+func (s *seqSource) ListSignals(context.Context) ([]datasource.Metadata, error) { return nil, nil }
+func (s *seqSource) GetMetadata(context.Context, string) (datasource.Metadata, error) {
+	return datasource.Metadata{Name: "x", Type: datasource.TypeFloat64}, nil
+}
+func (s *seqSource) Write(context.Context, string, any) error { return datasource.ErrNotWritable }
+func (s *seqSource) History(context.Context, string, time.Time, time.Time, int) ([]datasource.Value, error) {
+	return nil, datasource.ErrHistoryUnavailable
+}
+func (s *seqSource) Subscribe(ctx context.Context, _ string, ch chan<- datasource.Value) (datasource.CancelFunc, error) {
+	go func() {
+		for _, v := range s.seq {
+			select {
+			case ch <- v:
+			case <-ctx.Done():
+				return
+			}
+			time.Sleep(8 * time.Millisecond)
+		}
+	}()
+	return func() {}, nil
+}
+
+// TestSubscribePreservesUpstreamTimestamp verifies a single-source synthetic
+// emits each computed value with the upstream sample's timestamp.
+func TestSubscribePreservesUpstreamTimestamp(t *testing.T) {
+	log := slog.New(slog.NewTextHandler(os.Stderr, nil))
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	base := time.Date(2026, 6, 19, 10, 0, 0, 0, time.UTC)
+	src := &seqSource{name: "src", seq: []datasource.Value{
+		{Timestamp: base.Add(1 * time.Second), Data: 1.0, Quality: datasource.QualityGood},
+		{Timestamp: base.Add(2 * time.Second), Data: 2.0, Quality: datasource.QualityGood},
+		{Timestamp: base.Add(3 * time.Second), Data: 3.0, Quality: datasource.QualityGood},
+	}}
+
+	brk := broker.New(ctx, log)
+	brk.Register(src)
+	syn := New(t.TempDir(), brk, log)
+	if err := syn.Connect(ctx); err != nil {
+		t.Fatal(err)
+	}
+	if err := syn.AddSignal(SignalDef{
+		Name: "g", DS: "src", Signal: "x",
+		Pipeline: []NodeDef{{Type: "gain", Params: map[string]any{"gain": 10.0}}},
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	ch := make(chan datasource.Value, 8)
+	if _, err := syn.Subscribe(ctx, "g", ch); err != nil {
+		t.Fatal(err)
+	}
+
+	want := []time.Time{base.Add(1 * time.Second), base.Add(2 * time.Second), base.Add(3 * time.Second)}
+	for i, w := range want {
+		select {
+		case v := <-ch:
+			if !v.Timestamp.Equal(w) {
+				t.Errorf("emit #%d timestamp: want %s, got %s", i, w, v.Timestamp)
+			}
+		case <-time.After(2 * time.Second):
+			t.Fatalf("timeout waiting for emit #%d", i)
+		}
+	}
+}
+
+// TestSubscribeMultiSourceUsesLatestTimestamp verifies that a synthetic combining
+// two independent sources stamps each output with the MOST RECENT contributing
+// sample time — not the timestamp of whichever source happened to trigger the
+// computation. A slow source carrying a stale timestamp must not drag the output
+// backwards in time (which previously produced wrong/non-monotonic plot points).
+func TestSubscribeMultiSourceUsesLatestTimestamp(t *testing.T) {
+	log := slog.New(slog.NewTextHandler(os.Stderr, nil))
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	now := time.Date(2026, 6, 19, 12, 0, 0, 0, time.UTC)
+	// Fast source A with current timestamps.
+	a := &seqSource{name: "A", seq: []datasource.Value{
+		{Timestamp: now.Add(10 * time.Second), Data: 1.0, Quality: datasource.QualityGood},
+		{Timestamp: now.Add(11 * time.Second), Data: 2.0, Quality: datasource.QualityGood},
+		{Timestamp: now.Add(12 * time.Second), Data: 3.0, Quality: datasource.QualityGood},
+		{Timestamp: now.Add(13 * time.Second), Data: 4.0, Quality: datasource.QualityGood},
+	}}
+	// Slow source B: a single sample with a much older timestamp.
+	b := &seqSource{name: "B", seq: []datasource.Value{
+		{Timestamp: now.Add(1 * time.Second), Data: 100.0, Quality: datasource.QualityGood},
+	}}
+
+	brk := broker.New(ctx, log)
+	brk.Register(a)
+	brk.Register(b)
+	syn := New(t.TempDir(), brk, log)
+	if err := syn.Connect(ctx); err != nil {
+		t.Fatal(err)
+	}
+	if err := syn.AddSignal(SignalDef{
+		Name: "diff",
+		Graph: &Graph{Output: "out", Nodes: []GraphNode{
+			{ID: "sa", Kind: "source", DS: "A", Signal: "x"},
+			{ID: "sb", Kind: "source", DS: "B", Signal: "x"},
+			{ID: "sub", Kind: "op", Op: "subtract", Inputs: []string{"sa", "sb"}},
+			{ID: "out", Kind: "output", Inputs: []string{"sub"}},
+		}},
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	ch := make(chan datasource.Value, 16)
+	if _, err := syn.Subscribe(ctx, "diff", ch); err != nil {
+		t.Fatal(err)
+	}
+
+	var last time.Time
+	for i := 0; i < 4; i++ {
+		select {
+		case v := <-ch:
+			// The stale source-B timestamp (t=1s) must never be used: every output
+			// is stamped with the newest input time, so emits stay monotonic.
+			if v.Timestamp.Equal(now.Add(1 * time.Second)) {
+				t.Errorf("emit #%d used the stale source-B timestamp %s", i, v.Timestamp)
+			}
+			if !last.IsZero() && v.Timestamp.Before(last) {
+				t.Errorf("emit #%d went backwards: %s before previous %s", i, v.Timestamp, last)
+			}
+			last = v.Timestamp
+		case <-time.After(2 * time.Second):
+			t.Fatalf("timeout waiting for emit #%d", i)
+		}
+	}
+}

internal/datasource/synthetic/versions.go

@@ -0,0 +1,174 @@
+package synthetic
+
+import (
+	"encoding/json"
+	"fmt"
+	"hash/fnv"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+	"unicode"
+
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+// VersionMeta describes a single persisted revision of a synthetic signal,
+// mirroring storage.VersionMeta so the frontend treats every versioned document
+// type uniformly.
+type VersionMeta struct {
+	Version int       `json:"version"`
+	Name    string    `json:"name"`
+	Tag     string    `json:"tag,omitempty"`
+	Current bool      `json:"current"`
+	SavedAt time.Time `json:"savedAt"`
+}
+
+func (s *Synthetic) versionsDir() string {
+	return filepath.Join(s.storePath, "synthetic_versions")
+}
+
+// slugForFile maps an arbitrary signal name to a filesystem-safe stem. A short
+// hash of the full name is appended so distinct names that sanitise to the same
+// stem (e.g. "A:B" and "A_B") never share backup files.
+func slugForFile(name string) string {
+	var b strings.Builder
+	for _, r := range name {
+		if unicode.IsLetter(r) || unicode.IsDigit(r) || r == '-' || r == '_' {
+			b.WriteRune(r)
+		} else {
+			b.WriteByte('_')
+		}
+	}
+	h := fnv.New32a()
+	_, _ = h.Write([]byte(name))
+	return fmt.Sprintf("%s-%08x", b.String(), h.Sum32())
+}
+
+func (s *Synthetic) versionPath(name string, version int) string {
+	return filepath.Join(s.versionsDir(), fmt.Sprintf("%s.v%d.json", slugForFile(name), version))
+}
+
+// backupVersion writes a single signal revision to the versions directory.
+func (s *Synthetic) backupVersion(def SignalDef) error {
+	if err := os.MkdirAll(s.versionsDir(), 0o755); err != nil {
+		return err
+	}
+	data, err := json.MarshalIndent(def, "", "  ")
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(s.versionPath(def.Name, def.Version), data, 0o644)
+}
+
+// Versions returns metadata for every persisted revision of the named signal,
+// newest first. The live revision is flagged Current.
+func (s *Synthetic) Versions(name string) ([]VersionMeta, error) {
+	cur, err := s.GetSignal(name)
+	if err != nil {
+		return nil, err
+	}
+	curV := cur.Version
+	if curV < 1 {
+		curV = 1
+	}
+
+	var savedAt time.Time
+	if info, err := os.Stat(s.defsFilePath()); err == nil {
+		savedAt = info.ModTime()
+	}
+	out := []VersionMeta{{Version: curV, Name: cur.Name, Tag: cur.Tag, Current: true, SavedAt: savedAt}}
+
+	entries, err := os.ReadDir(s.versionsDir())
+	if err != nil && !os.IsNotExist(err) {
+		return nil, err
+	}
+	prefix := slugForFile(name) + ".v"
+	for _, e := range entries {
+		fn := e.Name()
+		if e.IsDir() || !strings.HasPrefix(fn, prefix) || !strings.HasSuffix(fn, ".json") {
+			continue
+		}
+		vStr := strings.TrimSuffix(strings.TrimPrefix(fn, prefix), ".json")
+		v, err := strconv.Atoi(vStr)
+		if err != nil {
+			continue
+		}
+		def, err := s.readVersion(name, v)
+		if err != nil {
+			continue
+		}
+		info, err := e.Info()
+		if err != nil {
+			continue
+		}
+		out = append(out, VersionMeta{Version: v, Name: def.Name, Tag: def.Tag, SavedAt: info.ModTime()})
+	}
+
+	sort.Slice(out, func(i, j int) bool { return out[i].Version > out[j].Version })
+	return out, nil
+}
+
+// GetVersion returns a specific revision of the named signal. The current
+// revision comes from the live store; older revisions from their backup file.
+func (s *Synthetic) GetVersion(name string, version int) (SignalDef, error) {
+	cur, err := s.GetSignal(name)
+	if err != nil {
+		return SignalDef{}, err
+	}
+	curV := cur.Version
+	if curV < 1 {
+		curV = 1
+	}
+	if version == curV {
+		return cur, nil
+	}
+	return s.readVersion(name, version)
+}
+
+func (s *Synthetic) readVersion(name string, version int) (SignalDef, error) {
+	data, err := os.ReadFile(s.versionPath(name, version))
+	if os.IsNotExist(err) {
+		return SignalDef{}, datasource.ErrNotFound
+	}
+	if err != nil {
+		return SignalDef{}, err
+	}
+	var def SignalDef
+	if err := json.Unmarshal(data, &def); err != nil {
+		return SignalDef{}, fmt.Errorf("parse revision: %w", err)
+	}
+	return def, nil
+}
+
+// PromoteVersion makes a past revision current by re-saving it on top of
+// history (non-destructive). Returns the resulting current definition.
+func (s *Synthetic) PromoteVersion(name string, version int) (SignalDef, error) {
+	def, err := s.GetVersion(name, version)
+	if err != nil {
+		return SignalDef{}, err
+	}
+	def.Tag = fmt.Sprintf("restored from v%d", version)
+	if err := s.UpdateSignal(def); err != nil {
+		return SignalDef{}, err
+	}
+	return s.GetSignal(name)
+}
+
+// ForkVersion creates a brand-new synthetic signal from a specific revision,
+// assigning a fresh unique name and resetting its version to 1.
+func (s *Synthetic) ForkVersion(name string, version int) (SignalDef, error) {
+	def, err := s.GetVersion(name, version)
+	if err != nil {
+		return SignalDef{}, err
+	}
+	def.Name = fmt.Sprintf("%s_fork_%d", name, time.Now().UnixMilli())
+	def.Version = 1
+	def.Tag = ""
+	if err := s.AddSignal(def); err != nil {
+		return SignalDef{}, err
+	}
+	return def, nil
+}

internal/datasource/synthetic/versions_test.go

@@ -0,0 +1,87 @@
+package synthetic
+
+import (
+	"context"
+	"testing"
+)
+
+func TestSyntheticVersioning(t *testing.T) {
+	syn, _, cancel := newTestSynthetic(t)
+	defer cancel()
+	if err := syn.Connect(context.Background()); err != nil {
+		t.Fatal(err)
+	}
+
+	// defWithGain builds a fresh def each time, mirroring how the REST handler
+	// decodes a new SignalDef per request (no aliasing of slices/maps).
+	defWithGain := func(g float64) SignalDef {
+		return SignalDef{Name: "wf", DS: "stub", Signal: "sine_1hz",
+			Pipeline: []NodeDef{{Type: "gain", Params: map[string]any{"gain": g}}}}
+	}
+
+	if err := syn.AddSignal(defWithGain(1.0)); err != nil {
+		t.Fatalf("AddSignal: %v", err)
+	}
+
+	cur, err := syn.GetSignal("wf")
+	if err != nil || cur.Version != 1 {
+		t.Fatalf("after add: version=%d err=%v", cur.Version, err)
+	}
+
+	// Two edits → v2, v3.
+	if err := syn.UpdateSignal(defWithGain(2.0)); err != nil {
+		t.Fatalf("UpdateSignal: %v", err)
+	}
+	if err := syn.UpdateSignal(defWithGain(3.0)); err != nil {
+		t.Fatalf("UpdateSignal: %v", err)
+	}
+
+	cur, _ = syn.GetSignal("wf")
+	if cur.Version != 3 {
+		t.Fatalf("want current v3, got v%d", cur.Version)
+	}
+
+	versions, err := syn.Versions("wf")
+	if err != nil {
+		t.Fatalf("Versions: %v", err)
+	}
+	if len(versions) != 3 {
+		t.Fatalf("want 3 versions, got %d", len(versions))
+	}
+	if !versions[0].Current || versions[0].Version != 3 {
+		t.Errorf("newest should be current v3: %+v", versions[0])
+	}
+
+	// v1 backup retrievable with original gain.
+	v1, err := syn.GetVersion("wf", 1)
+	if err != nil {
+		t.Fatalf("GetVersion v1: %v", err)
+	}
+	if v1.Pipeline[0].Params["gain"] != 1.0 {
+		t.Errorf("v1 gain: want 1.0, got %v", v1.Pipeline[0].Params["gain"])
+	}
+
+	// Promote v1 → becomes v4 (non-destructive).
+	promoted, err := syn.PromoteVersion("wf", 1)
+	if err != nil {
+		t.Fatalf("Promote: %v", err)
+	}
+	if promoted.Version != 4 || promoted.Pipeline[0].Params["gain"] != 1.0 {
+		t.Errorf("promote: version=%d gain=%v", promoted.Version, promoted.Pipeline[0].Params["gain"])
+	}
+
+	// Fork v3 → fresh signal, version 1.
+	forked, err := syn.ForkVersion("wf", 3)
+	if err != nil {
+		t.Fatalf("Fork: %v", err)
+	}
+	if forked.Version != 1 || forked.Name == "wf" {
+		t.Errorf("fork: name=%q version=%d", forked.Name, forked.Version)
+	}
+	if forked.Pipeline[0].Params["gain"] != 3.0 {
+		t.Errorf("fork gain: want 3.0, got %v", forked.Pipeline[0].Params["gain"])
+	}
+	if _, err := syn.GetSignal(forked.Name); err != nil {
+		t.Errorf("forked signal not registered: %v", err)
+	}
+}

internal/dsp/array_nodes.go

@@ -0,0 +1,230 @@
+package dsp
+
+import (
+	"errors"
+	"fmt"
+	"math"
+)
+
+// This file holds ArrayNode ops: those that operate natively on waveform
+// (float64 array) Samples — reductions (array→scalar), producers (array→array),
+// and element access. Each also implements the legacy scalar Node interface
+// (treating a scalar as a single-element array) so it remains usable from the
+// scalar eval path.
+
+// reductionProcess adapts a scalar Process call to a reduction ArrayNode.
+func reductionProcess(n ArrayNode, in []float64, st map[string]any) (float64, error) {
+	s, err := n.ProcessSample(scalarInputs(in), st)
+	if err != nil {
+		return 0, err
+	}
+	return s.F, nil
+}
+
+// ── IndexNode ───────────────────────────────────────────────────────────────
+
+// IndexNode extracts element I of an array input (array→scalar).
+type IndexNode struct{ I int }
+
+func (n *IndexNode) Type() string { return "index" }
+func (n *IndexNode) Process(in []float64, st map[string]any) (float64, error) {
+	return reductionProcess(n, in, st)
+}
+func (n *IndexNode) ProcessSample(in []Sample, _ map[string]any) (Sample, error) {
+	if len(in) == 0 {
+		return Sample{}, errors.New("index: no inputs")
+	}
+	arr := in[0].AsArray()
+	if n.I < 0 || n.I >= len(arr) {
+		return Sample{}, fmt.Errorf("index: %d out of range [0,%d)", n.I, len(arr))
+	}
+	return Scalar(arr[n.I]), nil
+}
+
+// ── SliceNode ───────────────────────────────────────────────────────────────
+
+// SliceNode returns a sub-range [Start,End) of an array input (array→array),
+// clamped to the array bounds. End <= 0 means "to the end".
+type SliceNode struct{ Start, End int }
+
+func (n *SliceNode) Type() string { return "slice" }
+func (n *SliceNode) Process(in []float64, st map[string]any) (float64, error) {
+	s, err := n.ProcessSample(scalarInputs(in), st)
+	if err != nil {
+		return 0, err
+	}
+	if len(s.Arr) == 0 {
+		return 0, nil
+	}
+	return s.Arr[0], nil
+}
+func (n *SliceNode) ProcessSample(in []Sample, _ map[string]any) (Sample, error) {
+	if len(in) == 0 {
+		return Sample{}, errors.New("slice: no inputs")
+	}
+	arr := in[0].AsArray()
+	start := n.Start
+	if start < 0 {
+		start = 0
+	}
+	if start > len(arr) {
+		start = len(arr)
+	}
+	end := n.End
+	if end <= 0 || end > len(arr) {
+		end = len(arr)
+	}
+	if end < start {
+		end = start
+	}
+	out := make([]float64, end-start)
+	copy(out, arr[start:end])
+	return Array(out), nil
+}
+
+// ── reductions ────────────────────────────────────────────────────────────────
+
+// SumNode sums an array input (array→scalar).
+type SumNode struct{}
+
+func (n *SumNode) Type() string { return "sum" }
+func (n *SumNode) Process(in []float64, st map[string]any) (float64, error) {
+	return reductionProcess(n, in, st)
+}
+func (n *SumNode) ProcessSample(in []Sample, _ map[string]any) (Sample, error) {
+	if len(in) == 0 {
+		return Sample{}, errors.New("sum: no inputs")
+	}
+	var s float64
+	for _, v := range in[0].AsArray() {
+		s += v
+	}
+	return Scalar(s), nil
+}
+
+// MeanNode averages an array input (array→scalar).
+type MeanNode struct{}
+
+func (n *MeanNode) Type() string { return "mean" }
+func (n *MeanNode) Process(in []float64, st map[string]any) (float64, error) {
+	return reductionProcess(n, in, st)
+}
+func (n *MeanNode) ProcessSample(in []Sample, _ map[string]any) (Sample, error) {
+	if len(in) == 0 {
+		return Sample{}, errors.New("mean: no inputs")
+	}
+	arr := in[0].AsArray()
+	if len(arr) == 0 {
+		return Scalar(0), nil
+	}
+	var s float64
+	for _, v := range arr {
+		s += v
+	}
+	return Scalar(s / float64(len(arr))), nil
+}
+
+// MinNode returns the minimum element of an array input (array→scalar).
+type MinNode struct{}
+
+func (n *MinNode) Type() string { return "min" }
+func (n *MinNode) Process(in []float64, st map[string]any) (float64, error) {
+	return reductionProcess(n, in, st)
+}
+func (n *MinNode) ProcessSample(in []Sample, _ map[string]any) (Sample, error) {
+	if len(in) == 0 {
+		return Sample{}, errors.New("min: no inputs")
+	}
+	arr := in[0].AsArray()
+	if len(arr) == 0 {
+		return Scalar(0), nil
+	}
+	m := arr[0]
+	for _, v := range arr[1:] {
+		if v < m {
+			m = v
+		}
+	}
+	return Scalar(m), nil
+}
+
+// MaxNode returns the maximum element of an array input (array→scalar).
+type MaxNode struct{}
+
+func (n *MaxNode) Type() string { return "max" }
+func (n *MaxNode) Process(in []float64, st map[string]any) (float64, error) {
+	return reductionProcess(n, in, st)
+}
+func (n *MaxNode) ProcessSample(in []Sample, _ map[string]any) (Sample, error) {
+	if len(in) == 0 {
+		return Sample{}, errors.New("max: no inputs")
+	}
+	arr := in[0].AsArray()
+	if len(arr) == 0 {
+		return Scalar(0), nil
+	}
+	m := arr[0]
+	for _, v := range arr[1:] {
+		if v > m {
+			m = v
+		}
+	}
+	return Scalar(m), nil
+}
+
+// LengthNode returns the element count of an array input (array→scalar).
+type LengthNode struct{}
+
+func (n *LengthNode) Type() string { return "length" }
+func (n *LengthNode) Process(in []float64, st map[string]any) (float64, error) {
+	return reductionProcess(n, in, st)
+}
+func (n *LengthNode) ProcessSample(in []Sample, _ map[string]any) (Sample, error) {
+	if len(in) == 0 {
+		return Sample{}, errors.New("length: no inputs")
+	}
+	return Scalar(float64(len(in[0].AsArray()))), nil
+}
+
+// ── FFTNode ────────────────────────────────────────────────────────────────
+
+// FFTNode computes the magnitude spectrum of an array input (array→array). The
+// input is zero-padded to the next power of two; the output has that length and
+// holds |X[k]| for each frequency bin.
+type FFTNode struct{}
+
+func (n *FFTNode) Type() string { return "fft" }
+func (n *FFTNode) Process(in []float64, st map[string]any) (float64, error) {
+	s, err := n.ProcessSample(scalarInputs(in), st)
+	if err != nil {
+		return 0, err
+	}
+	if len(s.Arr) == 0 {
+		return 0, nil
+	}
+	return s.Arr[0], nil
+}
+func (n *FFTNode) ProcessSample(in []Sample, _ map[string]any) (Sample, error) {
+	if len(in) == 0 {
+		return Sample{}, errors.New("fft: no inputs")
+	}
+	return Array(fftMagnitude(in[0].AsArray())), nil
+}
+
+// fftMagnitude returns the magnitude spectrum of x, zero-padded to the next
+// power of two. Returns an empty slice for empty input.
+func fftMagnitude(x []float64) []float64 {
+	if len(x) == 0 {
+		return nil
+	}
+	n := nextPow2(len(x))
+	re := make([]float64, n)
+	im := make([]float64, n)
+	copy(re, x)
+	fftRadix2(re, im)
+	mag := make([]float64, n)
+	for i := range mag {
+		mag[i] = math.Hypot(re[i], im[i])
+	}
+	return mag
+}

internal/dsp/array_nodes_test.go

@@ -0,0 +1,213 @@
+package dsp
+
+import (
+	"math"
+	"testing"
+)
+
+func TestSampleRoundTrip(t *testing.T) {
+	s := Scalar(3.5)
+	if s.IsArray {
+		t.Error("Scalar should not be an array")
+	}
+	if s.Type() != ValScalar {
+		t.Errorf("Scalar type: want ValScalar, got %v", s.Type())
+	}
+	if s.AsAny() != 3.5 {
+		t.Errorf("Scalar AsAny: want 3.5, got %v", s.AsAny())
+	}
+	if got := s.AsArray(); len(got) != 1 || got[0] != 3.5 {
+		t.Errorf("Scalar AsArray: want [3.5], got %v", got)
+	}
+
+	a := Array([]float64{1, 2, 3})
+	if !a.IsArray {
+		t.Error("Array should be an array")
+	}
+	if a.Type() != ValArray {
+		t.Errorf("Array type: want ValArray, got %v", a.Type())
+	}
+	got, ok := a.AsAny().([]float64)
+	if !ok || len(got) != 3 {
+		t.Errorf("Array AsAny: want []float64 len 3, got %v", a.AsAny())
+	}
+}
+
+func TestApplyElementwiseAllScalar(t *testing.T) {
+	n := &AddNode{}
+	out, err := ApplyElementwise(n, []Sample{Scalar(2), Scalar(3)}, map[string]any{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out.IsArray || out.F != 5 {
+		t.Errorf("all-scalar add: want scalar 5, got %v", out)
+	}
+}
+
+func TestApplyElementwiseBroadcast(t *testing.T) {
+	// array ⊕ scalar: scalar is a constant broadcast across the array.
+	n := &AddNode{}
+	out, err := ApplyElementwise(n, []Sample{Array([]float64{1, 2, 3}), Scalar(10)}, map[string]any{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !out.IsArray {
+		t.Fatalf("array+scalar: want array, got %v", out)
+	}
+	want := []float64{11, 12, 13}
+	for i, v := range want {
+		if out.Arr[i] != v {
+			t.Errorf("array+scalar[%d]: want %v, got %v", i, v, out.Arr[i])
+		}
+	}
+}
+
+func TestApplyElementwiseArrayArray(t *testing.T) {
+	n := &MultiplyNode{}
+	out, err := ApplyElementwise(n, []Sample{Array([]float64{1, 2, 3}), Array([]float64{4, 5, 6})}, map[string]any{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := []float64{4, 10, 18}
+	for i, v := range want {
+		if out.Arr[i] != v {
+			t.Errorf("array*array[%d]: want %v, got %v", i, v, out.Arr[i])
+		}
+	}
+}
+
+func TestApplyElementwiseLengthMismatch(t *testing.T) {
+	n := &AddNode{}
+	_, err := ApplyElementwise(n, []Sample{Array([]float64{1, 2}), Array([]float64{1, 2, 3})}, map[string]any{})
+	if err == nil {
+		t.Error("expected length-mismatch error")
+	}
+}
+
+func TestReductionNodes(t *testing.T) {
+	arr := []Sample{Array([]float64{2, 4, 6, 8})}
+	cases := []struct {
+		name string
+		node ArrayNode
+		want float64
+	}{
+		{"sum", &SumNode{}, 20},
+		{"mean", &MeanNode{}, 5},
+		{"min", &MinNode{}, 2},
+		{"max", &MaxNode{}, 8},
+		{"length", &LengthNode{}, 4},
+		{"index", &IndexNode{I: 2}, 6},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			out, err := tc.node.ProcessSample(arr, map[string]any{})
+			if err != nil {
+				t.Fatal(err)
+			}
+			if out.IsArray || out.F != tc.want {
+				t.Errorf("%s: want scalar %v, got %v", tc.name, tc.want, out)
+			}
+		})
+	}
+}
+
+func TestIndexNodeOutOfRange(t *testing.T) {
+	n := &IndexNode{I: 9}
+	_, err := n.ProcessSample([]Sample{Array([]float64{1, 2, 3})}, map[string]any{})
+	if err == nil {
+		t.Error("expected out-of-range error")
+	}
+}
+
+func TestSliceNode(t *testing.T) {
+	n := &SliceNode{Start: 1, End: 3}
+	out, err := n.ProcessSample([]Sample{Array([]float64{10, 20, 30, 40})}, map[string]any{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := []float64{20, 30}
+	if len(out.Arr) != len(want) {
+		t.Fatalf("slice: want len %d, got %d", len(want), len(out.Arr))
+	}
+	for i, v := range want {
+		if out.Arr[i] != v {
+			t.Errorf("slice[%d]: want %v, got %v", i, v, out.Arr[i])
+		}
+	}
+}
+
+func TestFFTMagnitude(t *testing.T) {
+	// A constant signal has all energy in bin 0 (the DC term equals the sum).
+	x := []float64{1, 1, 1, 1}
+	mag := fftMagnitude(x)
+	if len(mag) != 4 {
+		t.Fatalf("fft len: want 4, got %d", len(mag))
+	}
+	if math.Abs(mag[0]-4) > 1e-9 {
+		t.Errorf("fft DC bin: want 4, got %v", mag[0])
+	}
+	for k := 1; k < len(mag); k++ {
+		if math.Abs(mag[k]) > 1e-9 {
+			t.Errorf("fft bin %d: want ~0, got %v", k, mag[k])
+		}
+	}
+}
+
+func TestFFTSingleTone(t *testing.T) {
+	// One full cycle of a cosine over 8 samples → energy in bins 1 and N-1.
+	n := 8
+	x := make([]float64, n)
+	for i := range x {
+		x[i] = math.Cos(2 * math.Pi * float64(i) / float64(n))
+	}
+	mag := fftMagnitude(x)
+	if math.Abs(mag[1]-float64(n)/2) > 1e-6 {
+		t.Errorf("fft tone bin 1: want %v, got %v", float64(n)/2, mag[1])
+	}
+	if math.Abs(mag[n-1]-float64(n)/2) > 1e-6 {
+		t.Errorf("fft tone bin %d: want %v, got %v", n-1, float64(n)/2, mag[n-1])
+	}
+}
+
+func TestOpOutputType(t *testing.T) {
+	cases := []struct {
+		op      string
+		in      []ValType
+		want    ValType
+		wantErr bool
+	}{
+		// reductions → scalar regardless of input
+		{"sum", []ValType{ValArray}, ValScalar, false},
+		{"mean", []ValType{ValScalar}, ValScalar, false},
+		{"index", []ValType{ValUnknown}, ValScalar, false},
+		// array producers require array, yield array
+		{"fft", []ValType{ValArray}, ValArray, false},
+		{"slice", []ValType{ValUnknown}, ValArray, false},
+		{"fft", []ValType{ValScalar}, ValUnknown, true},
+		// scalar-only reject arrays
+		{"moving_average", []ValType{ValScalar}, ValScalar, false},
+		{"lua", []ValType{ValArray}, ValUnknown, true},
+		{"rms", []ValType{ValUnknown}, ValScalar, false},
+		// elementwise: array if any array, scalar if all scalar, else unknown
+		{"add", []ValType{ValScalar, ValScalar}, ValScalar, false},
+		{"add", []ValType{ValArray, ValScalar}, ValArray, false},
+		{"gain", []ValType{ValUnknown}, ValUnknown, false},
+		{"expr", []ValType{ValArray, ValScalar}, ValArray, false},
+	}
+	for _, tc := range cases {
+		got, err := OpOutputType(tc.op, tc.in)
+		if tc.wantErr {
+			if err == nil {
+				t.Errorf("OpOutputType(%q,%v): expected error", tc.op, tc.in)
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("OpOutputType(%q,%v): unexpected error %v", tc.op, tc.in, err)
+			continue
+		}
+		if got != tc.want {
+			t.Errorf("OpOutputType(%q,%v): want %v, got %v", tc.op, tc.in, tc.want, got)
+		}
+	}
+}

internal/dsp/fft.go

@@ -0,0 +1,58 @@
+package dsp
+
+import "math"
+
+// nextPow2 returns the smallest power of two >= n (and at least 1).
+func nextPow2(n int) int {
+	p := 1
+	for p < n {
+		p <<= 1
+	}
+	return p
+}
+
+// fftRadix2 computes the in-place iterative radix-2 Cooley-Tukey FFT of the
+// complex signal held in re/im. len(re) == len(im) must be a power of two. The
+// transform overwrites re/im with the frequency-domain result. This is a small
+// self-contained implementation (no external dependency) used by the synthetic
+// fft op.
+func fftRadix2(re, im []float64) {
+	n := len(re)
+	if n <= 1 {
+		return
+	}
+
+	// Bit-reversal permutation.
+	for i, j := 1, 0; i < n; i++ {
+		bit := n >> 1
+		for ; j&bit != 0; bit >>= 1 {
+			j ^= bit
+		}
+		j ^= bit
+		if i < j {
+			re[i], re[j] = re[j], re[i]
+			im[i], im[j] = im[j], im[i]
+		}
+	}
+
+	// Danielson-Lanczos butterflies.
+	for length := 2; length <= n; length <<= 1 {
+		ang := -2 * math.Pi / float64(length)
+		wReal, wImag := math.Cos(ang), math.Sin(ang)
+		for i := 0; i < n; i += length {
+			curReal, curImag := 1.0, 0.0
+			half := length >> 1
+			for k := 0; k < half; k++ {
+				a := i + k
+				b := i + k + half
+				tReal := curReal*re[b] - curImag*im[b]
+				tImag := curReal*im[b] + curImag*re[b]
+				re[b] = re[a] - tReal
+				im[b] = im[a] - tImag
+				re[a] += tReal
+				im[a] += tImag
+				curReal, curImag = curReal*wReal-curImag*wImag, curReal*wImag+curImag*wReal
+			}
+		}
+	}
+}

internal/dsp/nodes.go

@@ -277,16 +277,28 @@ func (n *ThresholdNode) Process(inputs []float64, _ map[string]any) (float64, er
 
 // ── ExprNode ──────────────────────────────────────────────────────────────────
 
-// ExprNode evaluates a simple arithmetic expression with variables a, b, c, d
+// ExprNode evaluates a simple arithmetic expression. Inputs are bound to named
-// bound to inputs[0..3]. It uses a hand-written recursive descent parser.
+// variables: Vars[i] -> inputs[i]. When Vars is empty it defaults to a, b, c, d
+// (bound to inputs[0..3]) for backward compatibility. It uses a hand-written
+// recursive descent parser.
 type ExprNode struct {
 	Expr string
+	Vars []string
+}
+
+// defaultVarNames returns the variable names for an expr/lua node: the explicit
+// list when set, otherwise the legacy a,b,c,d.
+func defaultVarNames(vars []string) []string {
+	if len(vars) > 0 {
+		return vars
+	}
+	return []string{"a", "b", "c", "d"}
 }
 
 func (n *ExprNode) Type() string { return "expr" }
 func (n *ExprNode) Process(inputs []float64, _ map[string]any) (float64, error) {
 	vars := map[string]float64{}
-	names := []string{"a", "b", "c", "d"}
+	names := defaultVarNames(n.Vars)
 	for i, name := range names {
 		if i < len(inputs) {
 			vars[name] = inputs[i]
@@ -507,13 +519,10 @@ func (p *exprParser) parseCall() (float64, error) {
 			}
 		}
 
-		// Not a function call — must be a single-letter variable.
+		// Not a function call — must be a declared input variable.
-		if len(name) != 1 {
-			return 0, fmt.Errorf("unknown identifier %q (use a–d for variables, or a known function name)", name)
-		}
 		val, ok := p.vars[name]
 		if !ok {
-			return 0, fmt.Errorf("unknown variable %q (allowed: a, b, c, d)", name)
+			return 0, fmt.Errorf("unknown variable %q (declare it as a named input)", name)
 		}
 		return val, nil
 	}
@@ -628,10 +637,12 @@ func (n *LowPassNode) Process(inputs []float64, state map[string]any) (float64,
 // ── LuaNode ───────────────────────────────────────────────────────────────────
 
 // LuaNode runs a Lua script in a sandboxed gopher-lua VM.
-// Inputs are bound to globals a, b, c, d. The script's return value is the output.
+// Inputs are bound to globals named by Vars (Vars[i] -> inputs[i]); when Vars is
+// empty it defaults to a, b, c, d. The script's return value is the output.
 // The os, io, package, and debug libraries are disabled.
 type LuaNode struct {
 	Script string
+	Vars   []string
 }
 
 func (n *LuaNode) Type() string { return "lua" }
@@ -682,7 +693,7 @@ func (n *LuaNode) Process(inputs []float64, state map[string]any) (result float6
 	L.SetTop(0)
 
 	// Bind inputs.
-	names := []string{"a", "b", "c", "d"}
+	names := defaultVarNames(n.Vars)
 	for i, name := range names {
 		if i < len(inputs) {
 			L.SetGlobal(name, lua.LNumber(inputs[i]))

internal/dsp/sample.go

@@ -0,0 +1,151 @@
+package dsp
+
+import "fmt"
+
+// ValType is the data type of a Sample: a scalar float, a float array
+// (waveform), or — at graph-compile time, before a source's real type is
+// known — unknown.
+type ValType uint8
+
+const (
+	ValUnknown ValType = iota
+	ValScalar
+	ValArray
+)
+
+func (t ValType) String() string {
+	switch t {
+	case ValScalar:
+		return "scalar"
+	case ValArray:
+		return "array"
+	default:
+		return "unknown"
+	}
+}
+
+// Sample is a value flowing through the synthetic DSP graph: either a scalar
+// float64 or a float64 array (waveform). It is the array-aware counterpart of
+// the bare float64 the legacy scalar Node interface uses.
+type Sample struct {
+	F       float64
+	Arr     []float64
+	IsArray bool
+}
+
+// Scalar wraps a float64 as a scalar Sample.
+func Scalar(f float64) Sample { return Sample{F: f} }
+
+// Array wraps a []float64 as an array Sample.
+func Array(a []float64) Sample { return Sample{Arr: a, IsArray: true} }
+
+// Type reports whether the sample is a scalar or an array.
+func (s Sample) Type() ValType {
+	if s.IsArray {
+		return ValArray
+	}
+	return ValScalar
+}
+
+// AsAny returns the value in the form datasource.Value.Data expects: a
+// []float64 for arrays, a float64 for scalars.
+func (s Sample) AsAny() any {
+	if s.IsArray {
+		return s.Arr
+	}
+	return s.F
+}
+
+// AsArray returns the sample's data as a slice: the array itself, or a
+// single-element slice for a scalar. Used by reductions that accept either.
+func (s Sample) AsArray() []float64 {
+	if s.IsArray {
+		return s.Arr
+	}
+	return []float64{s.F}
+}
+
+// ArrayNode is an optional extension of Node implemented by ops that operate
+// natively on Samples (reductions array→scalar, producers array→array, etc.).
+// eval prefers ProcessSample when a node implements it.
+type ArrayNode interface {
+	Node
+	ProcessSample(inputs []Sample, state map[string]any) (Sample, error)
+}
+
+// statelessElementwise lists scalar ops that are safe to broadcast element-wise
+// over array inputs: they hold no per-evaluation state, so running the legacy
+// Process once per array lane is well-defined. Stateful ops (moving_average,
+// rms, lowpass, derivative, integrate) and lua are excluded — a single shared
+// state map cannot be meaningfully split across lanes.
+var statelessElementwise = map[string]bool{
+	"gain": true, "offset": true, "add": true, "subtract": true,
+	"multiply": true, "divide": true, "clamp": true, "threshold": true,
+	"expr": true,
+}
+
+// StatelessElementwise reports whether a scalar op type may be broadcast over
+// array inputs via ApplyElementwise.
+func StatelessElementwise(nodeType string) bool { return statelessElementwise[nodeType] }
+
+// scalarInputs wraps a legacy float64 input slice as scalar Samples.
+func scalarInputs(in []float64) []Sample {
+	out := make([]Sample, len(in))
+	for i, v := range in {
+		out[i] = Scalar(v)
+	}
+	return out
+}
+
+// ApplyElementwise runs a stateless scalar Node over Sample inputs. If every
+// input is scalar it calls Process once and wraps the result. If any input is
+// an array it broadcasts: scalar inputs act as constants, all array inputs must
+// share a common length (else an error), and Process is invoked once per index.
+//
+// The node MUST be stateless (see StatelessElementwise) — a shared state map
+// cannot be split across array lanes.
+func ApplyElementwise(n Node, inputs []Sample, state map[string]any) (Sample, error) {
+	// Determine the array length, if any input is an array.
+	length := -1
+	for _, s := range inputs {
+		if !s.IsArray {
+			continue
+		}
+		if length == -1 {
+			length = len(s.Arr)
+		} else if len(s.Arr) != length {
+			return Sample{}, fmt.Errorf("%s: array length mismatch (%d vs %d)", n.Type(), length, len(s.Arr))
+		}
+	}
+
+	if length == -1 {
+		// All scalar — single legacy call.
+		row := make([]float64, len(inputs))
+		for i, s := range inputs {
+			row[i] = s.F
+		}
+		r, err := n.Process(row, state)
+		if err != nil {
+			return Sample{}, err
+		}
+		return Scalar(r), nil
+	}
+
+	out := make([]float64, length)
+	row := make([]float64, len(inputs))
+	for i := 0; i < length; i++ {
+		for j, s := range inputs {
+			if s.IsArray {
+				row[j] = s.Arr[i]
+			} else {
+				row[j] = s.F
+			}
+		}
+		r, err := n.Process(row, state)
+		if err != nil {
+			return Sample{}, err
+		}
+		out[i] = r
+	}
+	return Array(out), nil
+}

internal/dsp/types.go

@@ -0,0 +1,74 @@
+package dsp
+
+import "fmt"
+
+// Op type categories for static (compile-time / editor) type propagation.
+// These mirror the runtime dispatch in the synthetic graph evaluator and the
+// frontend's inferNodeTypes (web/src/lib/synthTypes.ts) — keep the three in
+// sync; a parity test guards the Go/TS pair.
+var (
+	// reductionOps collapse an array (or scalar) to a single scalar.
+	reductionOps = map[string]bool{
+		"index": true, "length": true, "sum": true,
+		"mean": true, "min": true, "max": true,
+	}
+	// arrayProducerOps require an array input and yield an array.
+	arrayProducerOps = map[string]bool{
+		"fft": true, "slice": true,
+	}
+	// scalarOnlyOps reject array inputs and yield a scalar. Stateful filters
+	// plus lua (whose state/closure cannot be broadcast per array lane).
+	scalarOnlyOps = map[string]bool{
+		"moving_average": true, "rms": true, "lowpass": true,
+		"derivative": true, "integrate": true, "lua": true,
+	}
+)
+
+// OpOutputType reports the output ValType of an op given its input types, and
+// an error if the inputs are definitely incompatible with the op. Inputs may be
+// ValUnknown (a source whose real type is not yet known at compile time); such
+// inputs never trigger an error — runtime Sample typing is authoritative.
+func OpOutputType(op string, in []ValType) (ValType, error) {
+	switch {
+	case reductionOps[op]:
+		return ValScalar, nil
+
+	case arrayProducerOps[op]:
+		for _, t := range in {
+			if t == ValScalar {
+				return ValUnknown, fmt.Errorf("%s requires an array input", op)
+			}
+		}
+		return ValArray, nil
+
+	case scalarOnlyOps[op]:
+		for _, t := range in {
+			if t == ValArray {
+				return ValUnknown, fmt.Errorf("%s does not accept an array input", op)
+			}
+		}
+		return ValScalar, nil
+
+	default:
+		// Elementwise stateless ops (gain, offset, add, subtract, multiply,
+		// divide, clamp, threshold, expr): array if any input is an array,
+		// scalar if all inputs are definitely scalar, otherwise unknown.
+		anyArray, anyUnknown := false, false
+		for _, t := range in {
+			switch t {
+			case ValArray:
+				anyArray = true
+			case ValUnknown:
+				anyUnknown = true
+			}
+		}
+		switch {
+		case anyArray:
+			return ValArray, nil
+		case anyUnknown:
+			return ValUnknown, nil
+		default:
+			return ValScalar, nil
+		}
+	}
+}

internal/server/dialoghub.go

@@ -0,0 +1,199 @@
+package server
+
+import (
+	"context"
+	"encoding/json"
+	"log/slog"
+	"strconv"
+	"strings"
+	"sync"
+
+	"github.com/uopi/uopi/internal/access"
+	"github.com/uopi/uopi/internal/audit"
+	"github.com/uopi/uopi/internal/broker"
+	"github.com/uopi/uopi/internal/controllogic"
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+// DialogHub fans control-logic dialog requests out to connected WebSocket
+// clients whose identity matches the dialog's user/group filter, and routes
+// input responses back to the dialog's target server variable.
+//
+// It implements controllogic.Notifier; the engine calls Notify when an
+// action.dialog node runs. Input dialogs are remembered as pending so a later
+// dialogResponse can be correlated by id and validated against its recipient
+// filter — this is why panels can write the response target even though direct
+// srv writes are otherwise gated to control-logic editors.
+type DialogHub struct {
+	broker *broker.Broker
+	policy *access.Policy
+	audit  audit.Recorder
+	log    *slog.Logger
+
+	mu      sync.Mutex
+	clients map[*wsClient]struct{}
+	pending map[string]controllogic.Dialog // input dialogs awaiting a response
+}
+
+// NewDialogHub builds an empty hub. rec is never nil after construction.
+func NewDialogHub(brk *broker.Broker, policy *access.Policy, rec audit.Recorder, log *slog.Logger) *DialogHub {
+	if rec == nil {
+		rec = audit.Nop()
+	}
+	return &DialogHub{
+		broker:  brk,
+		policy:  policy,
+		audit:   rec,
+		log:     log,
+		clients: map[*wsClient]struct{}{},
+		pending: map[string]controllogic.Dialog{},
+	}
+}
+
+func (h *DialogHub) add(c *wsClient) {
+	h.mu.Lock()
+	h.clients[c] = struct{}{}
+	h.mu.Unlock()
+}
+
+func (h *DialogHub) remove(c *wsClient) {
+	h.mu.Lock()
+	delete(h.clients, c)
+	h.mu.Unlock()
+}
+
+// dialogOut is the client-bound JSON form of a dialog request.
+type dialogOut struct {
+	Type    string `json:"type"` // always "dialog"
+	ID      string `json:"id"`
+	Kind    string `json:"kind"` // "info" | "error" | "input"
+	Title   string `json:"title,omitempty"`
+	Message string `json:"message,omitempty"`
+}
+
+// Notify implements controllogic.Notifier: serialise the dialog and push it to
+// every connected client matching its user/group filter.
+func (h *DialogHub) Notify(d controllogic.Dialog) {
+	b, err := json.Marshal(dialogOut{
+		Type:    "dialog",
+		ID:      d.ID,
+		Kind:    d.Kind,
+		Title:   d.Title,
+		Message: d.Message,
+	})
+	if err != nil {
+		return
+	}
+
+	h.mu.Lock()
+	if d.Kind == "input" && strings.TrimSpace(d.Target) != "" {
+		h.pending[d.ID] = d
+	}
+	var targets []*wsClient
+	for c := range h.clients {
+		if h.matches(c.user, d) {
+			targets = append(targets, c)
+		}
+	}
+	h.mu.Unlock()
+
+	for _, c := range targets {
+		select {
+		case c.outCh <- b:
+		default:
+		}
+	}
+}
+
+// matches reports whether user is a recipient of d. An empty user+group filter
+// targets everyone; otherwise the user must be named or in a named group.
+func (h *DialogHub) matches(user string, d controllogic.Dialog) bool {
+	if len(d.Users) == 0 && len(d.Groups) == 0 {
+		return true
+	}
+	if h.policy != nil {
+		user = h.policy.ResolveUser(user)
+	}
+	for _, u := range d.Users {
+		if u == user {
+			return true
+		}
+	}
+	if len(d.Groups) > 0 && h.policy != nil {
+		groups := map[string]bool{}
+		for _, g := range h.policy.GroupsOf(user) {
+			groups[g] = true
+		}
+		for _, g := range d.Groups {
+			if groups[g] {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// cancel drops a pending input dialog without writing (user dismissed it).
+func (h *DialogHub) cancel(id string) {
+	h.mu.Lock()
+	delete(h.pending, id)
+	h.mu.Unlock()
+}
+
+// respond writes an input dialog's response to its target server variable. The
+// dialog must be pending and the responding client must have been a recipient;
+// this gate replaces the usual srv write-permission check for sanctioned
+// control-logic responses.
+func (h *DialogHub) respond(ctx context.Context, c *wsClient, id string, value float64) {
+	h.mu.Lock()
+	d, ok := h.pending[id]
+	if ok {
+		delete(h.pending, id)
+	}
+	h.mu.Unlock()
+	if !ok || !h.matches(c.user, d) {
+		return
+	}
+
+	ds, name, ok := parseDialogTarget(d.Target)
+	if !ok || ds == "local" {
+		return
+	}
+	src, ok := h.broker.Source(ds)
+	if !ok {
+		h.log.Warn("dialog response: unknown data source", "ds", ds, "target", d.Target)
+		return
+	}
+
+	ev := audit.Event{
+		Actor:     c.user,
+		ActorType: audit.ActorUser,
+		Action:    "signal.write",
+		DS:        ds,
+		Signal:    name,
+		Value:     strconv.FormatFloat(value, 'g', -1, 64),
+		Detail:    "control logic dialog response",
+		IP:        c.ip,
+		Outcome:   audit.OutcomeOK,
+	}
+	wctx := datasource.WithUser(ctx, c.user)
+	if err := src.Write(wctx, name, value); err != nil {
+		h.log.Warn("dialog response: write failed", "ds", ds, "signal", name, "err", err)
+		ev.Outcome = audit.OutcomeError
+		ev.Error = err.Error()
+	}
+	h.audit.Record(ev)
+}
+
+// parseDialogTarget splits a "ds:name" dialog target on the first ':'. A bare
+// name (no ':') defaults to the persistent server-variable source "srv".
+func parseDialogTarget(t string) (ds, name string, ok bool) {
+	t = strings.TrimSpace(t)
+	if t == "" {
+		return "", "", false
+	}
+	if i := strings.IndexByte(t, ':'); i >= 0 {
+		return t[:i], t[i+1:], true
+	}
+	return "srv", t, true
+}

internal/server/server.go

@@ -10,7 +10,9 @@ import (
 
 	"github.com/uopi/uopi/internal/access"
 	"github.com/uopi/uopi/internal/api"
+	"github.com/uopi/uopi/internal/audit"
 	"github.com/uopi/uopi/internal/broker"
+	"github.com/uopi/uopi/internal/confmgr"
 	"github.com/uopi/uopi/internal/controllogic"
 	"github.com/uopi/uopi/internal/datasource/synthetic"
 	"github.com/uopi/uopi/internal/metrics"
@@ -27,7 +29,10 @@ type Server struct {
 
 // New creates the HTTP server, registers all routes, and returns a ready-to-start Server.
 // synth may be nil if the synthetic data source is not enabled.
-func New(addr string, webFS fs.FS, brk *broker.Broker, synth *synthetic.Synthetic, store *storage.Store, policy *access.Policy, acl *panelacl.Store, ctrlLogic *controllogic.Store, ctrlEngine *controllogic.Engine, channelFinderURL, archiverURL, trustedUserHeader string, log *slog.Logger) *Server {
+func New(addr string, webFS fs.FS, brk *broker.Broker, synth *synthetic.Synthetic, store *storage.Store, cfgStore *confmgr.Store, policy *access.Policy, acl *panelacl.Store, ctrlLogic *controllogic.Store, ctrlEngine *controllogic.Engine, dialogs *DialogHub, rec audit.Recorder, channelFinderURL, archiverURL, trustedUserHeader string, log *slog.Logger) *Server {
+	if rec == nil {
+		rec = audit.Nop()
+	}
 	mux := http.NewServeMux()
 
 	// Health check
@@ -37,7 +42,7 @@ func New(addr string, webFS fs.FS, brk *broker.Broker, synth *synthetic.Syntheti
 	})
 
 	// WebSocket endpoint
-	mux.Handle("/ws", &wsHandler{broker: brk, log: log, userHeader: trustedUserHeader, policy: policy})
+	mux.Handle("/ws", &wsHandler{broker: brk, log: log, userHeader: trustedUserHeader, policy: policy, audit: rec, dialogs: dialogs})
 
 	// Prometheus-format metrics
 	mux.HandleFunc("/metrics", metrics.Handler(brk.ActiveSubscriptions))
@@ -45,7 +50,7 @@ func New(addr string, webFS fs.FS, brk *broker.Broker, synth *synthetic.Syntheti
 	// REST API — registered on a dedicated mux so it can be wrapped with the
 	// access-control middleware (identity resolution + global level enforcement).
 	apiMux := http.NewServeMux()
-	api.New(brk, synth, store, policy, acl, ctrlLogic, ctrlEngine, channelFinderURL, archiverURL, log).Register(apiMux, apiPrefix)
+	api.New(brk, synth, store, cfgStore, policy, acl, ctrlLogic, ctrlEngine, rec, channelFinderURL, archiverURL, log).Register(apiMux, apiPrefix)
 	mux.Handle(apiPrefix+"/", accessMiddleware(policy, trustedUserHeader, apiMux))
 
 	// Embedded frontend — must be last (catch-all)

internal/server/ws.go

@@ -5,7 +5,9 @@ import (
 	"encoding/json"
 	"errors"
 	"log/slog"
+	"net"
 	"net/http"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -13,6 +15,7 @@ import (
 	"github.com/coder/websocket"
 
 	"github.com/uopi/uopi/internal/access"
+	"github.com/uopi/uopi/internal/audit"
 	"github.com/uopi/uopi/internal/broker"
 	"github.com/uopi/uopi/internal/datasource"
 	"github.com/uopi/uopi/internal/metrics"
@@ -31,6 +34,9 @@ type inMsg struct {
 	Name  string          `json:"name,omitempty"`
 	Value json.RawMessage `json:"value,omitempty"`
 
+	// dialogResponse — id of the control-logic dialog being answered.
+	ID string `json:"id,omitempty"`
+
 	// history
 	Start     time.Time `json:"start"`
 	End       time.Time `json:"end"`
@@ -53,6 +59,8 @@ type outMsg struct {
 	TS       string `json:"ts,omitempty"`
 	Value    any    `json:"value,omitempty"`
 	Quality  string `json:"quality,omitempty"`
+	Severity int    `json:"severity,omitempty"` // raw EPICS alarm severity (0=NO_ALARM)
+	Status   int    `json:"status,omitempty"`   // raw EPICS alarm status
 
 	// meta
 	Meta *metaPayload `json:"meta,omitempty"`
@@ -94,6 +102,10 @@ type wsHandler struct {
 	userHeader string
 	// policy enforces the global access level (blacklist) on signal writes.
 	policy *access.Policy
+	// audit records signal writes (never nil; audit.Nop when disabled).
+	audit audit.Recorder
+	// dialogs fans control-logic dialogs to clients and routes responses.
+	dialogs *DialogHub
 }
 
 func (h *wsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
@@ -103,6 +115,12 @@ func (h *wsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	if h.userHeader != "" {
 		user = strings.TrimSpace(r.Header.Get(h.userHeader))
 	}
+	// Resolve to the configured default_user when the header is absent so the
+	// session carries a real identity (used for audit + EPICS write attribution).
+	if h.policy != nil {
+		user = h.policy.ResolveUser(user)
+	}
+	clientIP := clientIP(r)
 
 	conn, err := websocket.Accept(w, r, &websocket.AcceptOptions{
 		// Permissive origin check for LAN / SSH-tunnel use; tighten when auth lands.
@@ -118,17 +136,31 @@ func (h *wsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	ctx, cancel := context.WithCancel(r.Context())
 	defer cancel()
 
+	rec := h.audit
+	if rec == nil {
+		rec = audit.Nop()
+	}
+
 	c := &wsClient{
 		conn:     conn,
 		broker:   h.broker,
 		user:     user,
+		ip:       clientIP,
 		policy:   h.policy,
+		audit:    rec,
+		dialogs:  h.dialogs,
 		outCh:    make(chan []byte, 512),
 		updateCh: make(chan broker.Update, 1024),
 		subs:     make(map[broker.SignalRef]func()),
 		log:      h.log,
 	}
 
+	// Register for control-logic dialog pushes for this client's identity.
+	if h.dialogs != nil {
+		h.dialogs.add(c)
+		defer h.dialogs.remove(c)
+	}
+
 	var wg sync.WaitGroup
 	wg.Add(3)
 	go func() { defer wg.Done(); c.readLoop(ctx, cancel) }()
@@ -153,7 +185,10 @@ type wsClient struct {
 	broker *broker.Broker
 	log    *slog.Logger
 	user   string         // end-user identity from the trusted proxy header ("" if none)
+	ip     string         // client address, for audit attribution
 	policy  *access.Policy // global access-level enforcement
+	audit   audit.Recorder // signal-write audit recorder (never nil)
+	dialogs *DialogHub     // control-logic dialog fan-out (nil if disabled)
 
 	outCh    chan []byte        // serialised outgoing messages
 	updateCh chan broker.Update // raw updates from the broker
@@ -196,6 +231,8 @@ func (c *wsClient) dispatchLoop(ctx context.Context) {
 				TS:       u.Value.Timestamp.UTC().Format(time.RFC3339Nano),
 				Value:    u.Value.Data,
 				Quality:  u.Value.Quality.String(),
+				Severity: u.Value.Severity,
+				Status:   u.Value.Status,
 			}
 			b, err := json.Marshal(msg)
 			if err != nil {
@@ -248,6 +285,8 @@ func (c *wsClient) handleMessage(ctx context.Context, data []byte) {
 		c.handleWrite(ctx, msg)
 	case "history":
 		c.handleHistory(ctx, msg)
+	case "dialogResponse":
+		c.handleDialogResponse(ctx, msg)
 	default:
 		c.sendError(ctx, "UNKNOWN_TYPE", "unknown message type: "+msg.Type)
 	}
@@ -303,6 +342,14 @@ func (c *wsClient) handleWrite(ctx context.Context, msg inMsg) {
 		return
 	}
 
+	// Server variables are read-any but write only for control-logic editors, so a
+	// panel cannot mutate sequence state unless its user owns control-logic access.
+	if msg.DS == "srv" && c.policy != nil && !c.policy.CanEditLogic(c.policy.ResolveUser(c.user)) {
+		c.log.Warn("write: server variable denied", "name", msg.Name, "user", c.user)
+		c.sendError(ctx, "ACCESS_DENIED", "writing server variables requires control-logic access")
+		return
+	}
+
 	ds, ok := c.broker.Source(msg.DS)
 	if !ok {
 		c.log.Warn("write: unknown data source", "ds", msg.DS, "name", msg.Name)
@@ -336,10 +383,44 @@ func (c *wsClient) handleWrite(ctx context.Context, msg inMsg) {
 	// Attribute the write to the connecting end-user so data sources (EPICS) can
 	// act under that identity rather than the server's.
 	ctx = datasource.WithUser(ctx, c.user)
+	ev := audit.Event{
+		Actor:     c.user,
+		ActorType: audit.ActorUser,
+		Action:    "signal.write",
+		DS:        msg.DS,
+		Signal:    msg.Name,
+		Value:     formatAuditValue(value),
+		IP:        c.ip,
+		Outcome:   audit.OutcomeOK,
+	}
 	if err := ds.Write(ctx, msg.Name, value); err != nil {
 		c.log.Warn("write: ds.Write failed", "ds", msg.DS, "name", msg.Name, "err", err)
+		ev.Outcome = audit.OutcomeError
+		ev.Error = err.Error()
+		c.audit.Record(ev)
 		c.sendError(ctx, "WRITE_ERROR", err.Error())
+		return
 	}
+	c.audit.Record(ev)
+}
+
+// handleDialogResponse routes the answer to a control-logic input dialog. An
+// empty/null value means the user dismissed the dialog (drop it without
+// writing); otherwise the numeric value is written to the dialog's target.
+func (c *wsClient) handleDialogResponse(ctx context.Context, msg inMsg) {
+	if c.dialogs == nil || msg.ID == "" {
+		return
+	}
+	if len(msg.Value) == 0 || string(msg.Value) == "null" {
+		c.dialogs.cancel(msg.ID)
+		return
+	}
+	var num float64
+	if err := json.Unmarshal(msg.Value, &num); err != nil {
+		c.dialogs.cancel(msg.ID)
+		return
+	}
+	c.dialogs.respond(ctx, c, msg.ID, num)
 }
 
 func (c *wsClient) handleHistory(ctx context.Context, msg inMsg) {
@@ -416,6 +497,44 @@ func (c *wsClient) sendError(ctx context.Context, code, message string) {
 
 // ── Helpers ───────────────────────────────────────────────────────────────────
 
+// clientIP returns the best-effort client address for audit attribution,
+// preferring the X-Forwarded-For / X-Real-IP headers set by a reverse proxy and
+// falling back to the TCP peer address.
+func clientIP(r *http.Request) string {
+	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
+		if i := strings.IndexByte(xff, ','); i >= 0 {
+			return strings.TrimSpace(xff[:i])
+		}
+		return strings.TrimSpace(xff)
+	}
+	if xr := r.Header.Get("X-Real-IP"); xr != "" {
+		return strings.TrimSpace(xr)
+	}
+	if host, _, err := net.SplitHostPort(r.RemoteAddr); err == nil {
+		return host
+	}
+	return r.RemoteAddr
+}
+
+// formatAuditValue renders a written value as a compact string for the audit log.
+func formatAuditValue(v any) string {
+	switch x := v.(type) {
+	case string:
+		return x
+	case float64:
+		return strconv.FormatFloat(x, 'g', -1, 64)
+	case bool:
+		return strconv.FormatBool(x)
+	case nil:
+		return ""
+	default:
+		if b, err := json.Marshal(v); err == nil {
+			return string(b)
+		}
+		return ""
+	}
+}
+
 func metadataToPayload(m datasource.Metadata) *metaPayload {
 	return &metaPayload{
 		Type:        dataTypeName(m.Type),

internal/storage/store.go

@@ -474,16 +474,43 @@ func setXMLAttribute(data []byte, attr, value string) ([]byte, error) {
 	return []byte(s[:valStart] + value + s[valStart+valEnd:]), nil
 }
 
-// Delete removes the interface with the given ID.
+// Delete moves the interface with the given ID — and all of its version
+// backups — into a timestamped trash folder so it can be recovered if needed.
+// Nothing is destroyed; recovery is a matter of moving the files back.
 func (s *Store) Delete(id string) error {
 	if err := validateID(id); err != nil {
 		return ErrNotFound
 	}
-	err := os.Remove(s.filePath(id))
+	if _, err := os.Stat(s.filePath(id)); err != nil {
 		if errors.Is(err, os.ErrNotExist) {
 			return ErrNotFound
 		}
 		return err
+	}
+
+	trashDir := filepath.Join(s.rootDir, "trash", "interfaces", fmt.Sprintf("%s.%d", id, time.Now().UnixMilli()))
+	if err := os.MkdirAll(trashDir, 0o755); err != nil {
+		return fmt.Errorf("create trash dir: %w", err)
+	}
+
+	// Move the current file plus every versioned backup (id.vN.xml), preserving
+	// their original names so a restore is a straight move-back.
+	entries, err := os.ReadDir(s.dir)
+	if err != nil {
+		return err
+	}
+	for _, e := range entries {
+		name := e.Name()
+		if e.IsDir() {
+			continue
+		}
+		if name == id+".xml" || (strings.HasPrefix(name, id+".v") && isVersioned(name)) {
+			if err := os.Rename(filepath.Join(s.dir, name), filepath.Join(trashDir, name)); err != nil {
+				return fmt.Errorf("move %s to trash: %w", name, err)
+			}
+		}
+	}
+	return nil
 }
 
 // Clone duplicates an interface, assigning a new unique ID.

web/src/App.tsx

@@ -4,6 +4,7 @@ import { wsClient } from './lib/ws';
 import ViewMode from './ViewMode';
 import EditMode from './EditMode';
 import FullscreenMode from './FullscreenMode';
+import ControlDialogs from './ControlDialogs';
 import { applyZoom, getStoredZoom } from './ZoomControl';
 import { AuthContext, DEFAULT_ME, fetchMe, canRead } from './lib/auth';
 import type { Interface, Me } from './lib/types';
@@ -69,6 +70,7 @@ export default function App() {
   return (
     <AuthContext.Provider value={me}>
       <div class="app-root">
+        <ControlDialogs />
         {wsStatus === 'disconnected' && (
           <div class="connection-banner">WebSocket disconnected — reconnecting…</div>
         )}

web/src/AuditViewer.tsx

@@ -0,0 +1,169 @@
+import { h } from 'preact';
+import { useState, useEffect, useCallback } from 'preact/hooks';
+
+// AuditEvent mirrors the JSON returned by GET /api/v1/audit (internal/audit.Event).
+interface AuditEvent {
+  time: string;
+  actor: string;
+  actorType: string; // "user" | "system"
+  action: string;
+  ds?: string;
+  signal?: string;
+  value?: string;
+  detail?: string;
+  ip?: string;
+  outcome: string; // "ok" | "error"
+  error?: string;
+}
+
+interface Props { onClose: () => void; }
+
+/** Convert an RFC3339/ISO timestamp to a compact local datetime string. */
+function fmtTime(iso: string): string {
+  const d = new Date(iso);
+  if (isNaN(d.getTime())) return iso;
+  const pad = (n: number) => String(n).padStart(2, '0');
+  return `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())} ${pad(d.getHours())}:${pad(d.getMinutes())}:${pad(d.getSeconds())}`;
+}
+
+/** Convert a datetime-local input value (local time) to an RFC3339 string. */
+function localToRFC3339(v: string): string {
+  if (!v) return '';
+  const d = new Date(v);
+  return isNaN(d.getTime()) ? '' : d.toISOString();
+}
+
+export default function AuditViewer({ onClose }: Props) {
+  const [events, setEvents] = useState<AuditEvent[]>([]);
+  const [loading, setLoading] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+
+  // Filters
+  const [user, setUser] = useState('');
+  const [action, setAction] = useState('');
+  const [signal, setSignal] = useState('');
+  const [start, setStart] = useState('');
+  const [end, setEnd] = useState('');
+
+  const load = useCallback(async () => {
+    setLoading(true);
+    setError(null);
+    try {
+      const q = new URLSearchParams();
+      if (user.trim()) q.set('user', user.trim());
+      if (action) q.set('action', action);
+      if (signal.trim()) q.set('signal', signal.trim());
+      const s = localToRFC3339(start);
+      const e = localToRFC3339(end);
+      if (s) q.set('start', s);
+      if (e) q.set('end', e);
+      const res = await fetch(`/api/v1/audit?${q.toString()}`);
+      if (res.status === 403) throw new Error('You are not permitted to view the audit log.');
+      if (!res.ok) throw new Error(`HTTP ${res.status}`);
+      const data = await res.json();
+      setEvents(Array.isArray(data) ? data : []);
+    } catch (err) {
+      setError(err instanceof Error ? err.message : String(err));
+      setEvents([]);
+    } finally {
+      setLoading(false);
+    }
+  }, [user, action, signal, start, end]);
+
+  // Initial load.
+  useEffect(() => { load(); }, []); // eslint-disable-line react-hooks/exhaustive-deps
+
+  function resetFilters() {
+    setUser(''); setAction(''); setSignal(''); setStart(''); setEnd('');
+  }
+
+  return (
+    <div class="cl-overlay" onMouseDown={(e) => { if (e.target === e.currentTarget) onClose(); }}>
+      <div class="cl-modal audit-modal">
+        <header class="cl-header">
+          <span class="cl-title">Audit log</span>
+          <span class="hint cl-subtitle">Every system-affecting action (signal writes, control-logic and interface changes).</span>
+          <div class="cl-header-actions">
+            <button class="panel-btn" disabled={loading} onClick={load}>{loading ? 'Loading…' : 'Refresh'}</button>
+            <button class="panel-btn" onClick={onClose}>Close</button>
+          </div>
+        </header>
+
+        <div class="audit-filters">
+          <input class="audit-filter" type="text" placeholder="User" value={user}
+            onInput={(e) => setUser((e.target as HTMLInputElement).value)} />
+          <select class="audit-filter" value={action}
+            onChange={(e) => setAction((e.target as HTMLSelectElement).value)}>
+            <option value="">All actions</option>
+            <option value="signal.write">signal.write</option>
+            <option value="interface.create">interface.create</option>
+            <option value="interface.update">interface.update</option>
+            <option value="interface.delete">interface.delete</option>
+            <option value="controllogic.create">controllogic.create</option>
+            <option value="controllogic.update">controllogic.update</option>
+            <option value="controllogic.delete">controllogic.delete</option>
+          </select>
+          <input class="audit-filter" type="text" placeholder="Signal contains…" value={signal}
+            onInput={(e) => setSignal((e.target as HTMLInputElement).value)} />
+          <label class="audit-filter-label">From
+            <input class="audit-filter" type="datetime-local" value={start}
+              onInput={(e) => setStart((e.target as HTMLInputElement).value)} />
+          </label>
+          <label class="audit-filter-label">To
+            <input class="audit-filter" type="datetime-local" value={end}
+              onInput={(e) => setEnd((e.target as HTMLInputElement).value)} />
+          </label>
+          <button class="panel-btn" disabled={loading} onClick={load}>Apply</button>
+          <button class="panel-btn" onClick={resetFilters}>Reset</button>
+        </div>
+
+        {error && <div class="cl-error">{error}</div>}
+
+        <div class="audit-body">
+          {!error && events.length === 0 && !loading && (
+            <div class="hint audit-empty">No matching audit entries.</div>
+          )}
+          {events.length > 0 && (
+            <table class="audit-table">
+              <thead>
+                <tr>
+                  <th>Time</th>
+                  <th>Actor</th>
+                  <th>Action</th>
+                  <th>Source</th>
+                  <th>Signal / target</th>
+                  <th>Value</th>
+                  <th>Detail</th>
+                  <th>Client</th>
+                  <th>Result</th>
+                </tr>
+              </thead>
+              <tbody>
+                {events.map((ev, i) => (
+                  <tr key={i} class={ev.outcome === 'error' ? 'audit-row-error' : ''}>
+                    <td class="audit-time">{fmtTime(ev.time)}</td>
+                    <td>
+                      <span class={`audit-actor-tag audit-actor-${ev.actorType}`}>{ev.actorType}</span>
+                      {' '}{ev.actor || '—'}
+                    </td>
+                    <td>{ev.action}</td>
+                    <td>{ev.ds || '—'}</td>
+                    <td class="audit-signal" title={ev.signal}>{ev.signal || '—'}</td>
+                    <td class="audit-value" title={ev.value}>{ev.value ?? '—'}</td>
+                    <td class="audit-detail" title={ev.detail}>{ev.detail || '—'}</td>
+                    <td>{ev.ip || '—'}</td>
+                    <td>
+                      {ev.outcome === 'error'
+                        ? <span class="audit-result-err" title={ev.error}>error</span>
+                        : <span class="audit-result-ok">ok</span>}
+                    </td>
+                  </tr>
+                ))}
+              </tbody>
+            </table>
+          )}
+        </div>
+      </div>
+    </div>
+  );
+}

web/src/Canvas.tsx

@@ -16,6 +16,7 @@ import Button from './widgets/Button';
 import PlotWidget from './widgets/PlotWidget';
 import ImageWidget from './widgets/ImageWidget';
 import LinkWidget from './widgets/LinkWidget';
+import ConfigSelect from './widgets/ConfigSelect';
 import ContextMenu from './ContextMenu';
 import InfoPanel from './InfoPanel';
 import SplitLayout from './SplitLayout';
@@ -34,6 +35,7 @@ const COMPONENTS: Record<string, any> = {
   plot:      PlotWidget,
   image:     ImageWidget,
   link:      LinkWidget,
+  configselect: ConfigSelect,
 };
 
 interface CtxState {
@@ -155,7 +157,7 @@ export default function Canvas({ iface, onNavigate, timeRange }: Props) {
 
   return (
     <div class="canvas-container">
-      <div class="canvas-area" style={`width:${iface.w}px;height:${iface.h}px;`}>
+      <div class="canvas-area canvas-view-bare" style={`width:${iface.w}px;height:${iface.h}px;`}>
         {iface.widgets.map(widget => {
           const Comp = COMPONENTS[widget.type];
           const inner = Comp

web/src/ContextualHelp.tsx

@@ -1,95 +0,0 @@
-import { h } from 'preact';
-import { useState, useRef, useEffect } from 'preact/hooks';
-
-interface Props {
-  mode: 'view' | 'edit';
-  onOpenManual: (section?: string) => void;
-}
-
-const TIPS: Record<string, Array<{ text: string; section?: string }>> = {
-  view: [
-    { text: 'Click any interface in the left panel to load it on the canvas.', section: 'view' },
-    { text: 'Right-click a widget to view signal info or export data as CSV.', section: 'view' },
-    { text: 'The ● Live button shows live streaming is active. Use the date pickers to load historical data.', section: 'history' },
-    { text: 'Click Edit (top-right) to open the drag-and-drop panel builder.', section: 'edit' },
-    { text: 'Use the Share button on a panel to grant access to users or groups.', section: 'sharing' },
-    { text: 'The ⚙ Control logic button opens server-side automation that runs even with no panel open.', section: 'control' },
-    { text: 'The dot in the status chip turns green when the WebSocket is connected.', section: 'view' },
-  ],
-  edit: [
-    { text: 'Drag a signal from the left tree onto the canvas to create a widget.', section: 'edit' },
-    { text: 'Click a widget to select it, then adjust its properties on the right.', section: 'edit' },
-    { text: 'Ctrl+click to select multiple widgets; then use the align toolbar.', section: 'edit' },
-    { text: 'Ctrl+Z to undo, Ctrl+Y to redo. Up to 50 steps are remembered.', section: 'shortcuts' },
-    { text: 'Use "+ Synthetic" in the signal tree to create computed/filtered signals.', section: 'signals' },
-    { text: 'Switch to the Logic tab to add interactive behaviour with a node-graph flow editor.', section: 'logic' },
-    { text: 'Add Local variables for set-points and counters that live inside the panel.', section: 'edit' },
-    { text: 'Arrow keys nudge the selected widget by 1 px (Shift for grid size).', section: 'shortcuts' },
-  ],
-};
-
-export default function ContextualHelp({ mode, onOpenManual }: Props) {
-  const [open, setOpen] = useState(false);
-  const [tipIndex, setTipIndex] = useState(0);
-  const ref = useRef<HTMLDivElement>(null);
-  const tips = TIPS[mode];
-
-  // Close on outside click
-  useEffect(() => {
-    if (!open) return;
-    function handler(e: MouseEvent) {
-      if (ref.current && !ref.current.contains(e.target as Node)) {
-        setOpen(false);
-      }
-    }
-    document.addEventListener('mousedown', handler);
-    return () => document.removeEventListener('mousedown', handler);
-  }, [open]);
-
-  // Cycle to a new random tip each time the popover opens
-  function handleOpen() {
-    setTipIndex(t => (t + 1) % tips.length);
-    setOpen(o => !o);
-  }
-
-  const tip = tips[tipIndex];
-
-  return (
-    <div class="ctx-help" ref={ref}>
-      <button
-        class="ctx-help-btn"
-        onClick={handleOpen}
-        title="Contextual help"
-        aria-label="Open contextual help"
-        aria-expanded={open}
-      >
-        ?
-      </button>
-
-      {open && (
-        <div class="ctx-help-popover" role="tooltip">
-          <div class="ctx-help-tip">
-            <span class="ctx-help-icon">💡</span>
-            <span>{tip.text}</span>
-          </div>
-
-          <div class="ctx-help-footer">
-            <button
-              class="ctx-help-nav"
-              onClick={() => setTipIndex(t => (t + 1) % tips.length)}
-              title="Next tip"
-            >
-              Next tip →
-            </button>
-            <button
-              class="ctx-help-link"
-              onClick={() => { setOpen(false); onOpenManual(tip.section); }}
-            >
-              Open manual ↗
-            </button>
-          </div>
-        </div>
-      )}
-    </div>
-  );
-}

web/src/ControlDialogs.tsx

@@ -0,0 +1,60 @@
+import { h, Fragment } from 'preact';
+import { useState, useEffect } from 'preact/hooks';
+import { wsClient } from './lib/ws';
+import { controlDialogs, dismissControlDialog, type ControlDialog } from './lib/controldialogs';
+
+// Renders dialogs pushed by server-side control-logic action.dialog nodes over
+// the WebSocket. Mounted once globally (App) since these are addressed to the
+// connected user, independent of which panel is open. info/error dialogs are
+// acknowledgements; input dialogs send a numeric response back to the server.
+export default function ControlDialogs() {
+  const [reqs, setReqs] = useState<ControlDialog[]>([]);
+  useEffect(() => controlDialogs.subscribe(setReqs), []);
+  if (reqs.length === 0) return null;
+  return <Fragment>{reqs.map(r => <ControlDialogModal key={r.id} req={r} />)}</Fragment>;
+}
+
+function ControlDialogModal({ req }: { req: ControlDialog; key?: string }) {
+  const isInput = req.kind === 'input';
+  const [val, setVal] = useState('');
+
+  function ok() {
+    if (isInput) {
+      const n = parseFloat(val);
+      wsClient.sendDialogResponse(req.id, Number.isFinite(n) ? n : null);
+    }
+    dismissControlDialog(req.id);
+  }
+  function cancel() {
+    if (isInput) wsClient.sendDialogResponse(req.id, null);
+    dismissControlDialog(req.id);
+  }
+
+  function onKey(e: KeyboardEvent) {
+    if (e.key === 'Enter') { e.preventDefault(); ok(); }
+    if (e.key === 'Escape') { e.preventDefault(); cancel(); }
+  }
+
+  return (
+    <div class="logic-dialog-backdrop" onKeyDown={onKey}>
+      <div class={`logic-dialog logic-dialog-${req.kind}`} role="dialog">
+        <div class="logic-dialog-header">
+          {req.title || (req.kind === 'error' ? 'Error' : isInput ? 'Input required' : 'Info')}
+        </div>
+        {req.message && <div class="logic-dialog-message">{req.message}</div>}
+        {isInput && (
+          <div class="logic-dialog-field">
+            <input class="prop-input logic-dialog-input" type="number"
+              autoFocus value={val}
+              onInput={(e) => setVal((e.target as HTMLInputElement).value)}
+              onKeyDown={onKey} />
+          </div>
+        )}
+        <div class="logic-dialog-actions">
+          {isInput && <button class="panel-btn" onClick={cancel}>Cancel</button>}
+          <button class="panel-btn panel-btn-primary" onClick={ok}>OK</button>
+        </div>
+      </div>
+    </div>
+  );
+}

web/src/ControlLogicEditor.tsx

@@ -1,8 +1,9 @@
 import { h, Fragment } from 'preact';
 import { useState, useEffect, useRef } from 'preact/hooks';
-import SearchableSelect from './SearchableSelect';
+import SignalPicker, { SignalOption } from './SignalPicker';
 import LuaEditor from './LuaEditor';
 import { checkExpr } from './lib/expr';
+import { VersionTree, DiffViewer } from './VersionHistory';
 
 // ── Types (mirror internal/controllogic/model.go) ────────────────────────────
 
@@ -18,7 +19,13 @@ type CLNodeKind =
   | 'action.write'
   | 'action.delay'
   | 'action.log'
-  | 'action.lua';
+  | 'action.lua'
+  | 'action.dialog'
+  | 'action.config.apply'
+  | 'action.config.read'
+  | 'action.config.write'
+  | 'action.config.create'
+  | 'action.config.snapshot';
 
 interface CLNode {
   id: string;
@@ -55,6 +62,11 @@ const NODE_W = 11.5 * REM;
 const PORT_TOP = 2 * REM;
 const PORT_GAP = 1.375 * REM;
 const PORT_R = 0.375 * REM;
+// Ports sit inside the node's padding box, offset from the node border-box origin
+// by the node borders (3px colored top accent, 1px sides). Anchors add the same
+// offsets so wires meet the port centers, not their top edges.
+const BORDER = 1;
+const BORDER_TOP = 3;
 
 interface PaletteEntry { kind: CLNodeKind; label: string; params: Record<string, string>; }
 
@@ -71,6 +83,12 @@ const PALETTE: PaletteEntry[] = [
   { kind: 'action.delay',      label: 'Delay',     params: { ms: '500' } },
   { kind: 'action.log',        label: 'Log',       params: { expr: '', label: '' } },
   { kind: 'action.lua',        label: 'Lua script', params: { script: '-- get("ds:name") reads, set("ds:name", v) writes,\n-- log("msg") logs to the server.\n' } },
+  { kind: 'action.dialog',     label: 'Dialog',    params: { kind: 'info', title: '', message: '', users: '', groups: '', target: '' } },
+  { kind: 'action.config.apply', label: 'Apply config', params: { instance: '' } },
+  { kind: 'action.config.read',  label: 'Read config',  params: { instance: '', key: '', target: '' } },
+  { kind: 'action.config.write', label: 'Write config', params: { instance: '', key: '', expr: '' } },
+  { kind: 'action.config.create', label: 'Create config', params: { set: '', name: 'auto', from: '' } },
+  { kind: 'action.config.snapshot', label: 'Snapshot config', params: { set: '', name: '' } },
 ];
 
 const KIND_LABEL: Record<CLNodeKind, string> = {
@@ -86,6 +104,12 @@ const KIND_LABEL: Record<CLNodeKind, string> = {
   'action.delay': 'Delay',
   'action.log': 'Log',
   'action.lua': 'Lua script',
+  'action.dialog': 'Dialog',
+  'action.config.apply': 'Apply config',
+  'action.config.read': 'Read config',
+  'action.config.write': 'Write config',
+  'action.config.create': 'Create config',
+  'action.config.snapshot': 'Snapshot config',
 };
 
 const THRESHOLD_OPS = ['>', '<', '>=', '<=', '==', '!='] as const;
@@ -117,11 +141,11 @@ function nodeHeight(kind: CLNodeKind): number { return PORT_TOP + outputs(kind).
 
 function genId(): string { return 'n_' + Math.random().toString(36).slice(2, 9); }
 
-function inAnchor(n: CLNode) { return { x: n.x, y: n.y + PORT_TOP }; }
+function inAnchor(n: CLNode) { return { x: n.x + BORDER, y: n.y + BORDER_TOP + PORT_TOP }; }
 function outAnchor(n: CLNode, port: string) {
   const ports = outputs(n.kind);
   const i = Math.max(0, ports.findIndex(p => p.id === port));
-  return { x: n.x + NODE_W, y: n.y + PORT_TOP + i * PORT_GAP };
+  return { x: n.x + NODE_W - BORDER, y: n.y + BORDER_TOP + PORT_TOP + i * PORT_GAP };
 }
 function wirePathStr(x1: number, y1: number, x2: number, y2: number): string {
   const dx = Math.max(40, Math.abs(x2 - x1) / 2);
@@ -139,6 +163,20 @@ export default function ControlLogicEditor({ onClose }: Props) {
   const [dirty, setDirty] = useState(false);
   const [busy, setBusy] = useState(false);
   const [error, setError] = useState<string | null>(null);
+  const [showCloseConfirm, setShowCloseConfirm] = useState(false);
+  const [showVersions, setShowVersions] = useState(false);
+  const [viewingVersion, setViewingVersion] = useState<number | null>(null);
+  const [diff, setDiff] = useState<{ av: number; bv: number } | null>(null);
+  const [verReload, setVerReload] = useState(0);
+
+  // Closing with unsaved changes prompts instead of silently discarding them.
+  function requestClose() {
+    if (dirty) { setShowCloseConfirm(true); return; }
+    onClose();
+  }
+  async function saveAndClose() {
+    if (await saveGraph()) { setShowCloseConfirm(false); onClose(); }
+  }
 
   async function reload() {
     try {
@@ -180,8 +218,8 @@ export default function ControlLogicEditor({ onClose }: Props) {
     }
   }
 
-  async function saveGraph() {
+  async function saveGraph(): Promise<boolean> {
-    if (!graph) return;
+    if (!graph) return false;
     setBusy(true);
     setError(null);
     try {
@@ -191,8 +229,10 @@ export default function ControlLogicEditor({ onClose }: Props) {
       if (!res.ok) throw new Error(`HTTP ${res.status}`);
       setDirty(false);
       await reload();
+      return true;
     } catch (err) {
       setError(`Save failed: ${err instanceof Error ? err.message : err}`);
+      return false;
     } finally {
       setBusy(false);
     }
@@ -239,16 +279,35 @@ export default function ControlLogicEditor({ onClose }: Props) {
     setDirty(true);
   }
 
+  // Load a past revision's content into the editor as unsaved edits; saving it
+  // promotes it to a new current version (non-destructive).
+  async function viewVersion(version: number) {
+    if (!graph) return;
+    if (dirty && !confirm('Discard unsaved changes to load this version?')) return;
+    try {
+      const res = await fetch(`/api/v1/controllogic/${encodeURIComponent(graph.id)}/versions/${version}`);
+      if (!res.ok) throw new Error(`HTTP ${res.status}`);
+      const g: CLGraph = await res.json();
+      setGraph(g);
+      setViewingVersion(version);
+      setDirty(false);
+    } catch (err) {
+      setError(`Load version failed: ${err instanceof Error ? err.message : err}`);
+    }
+  }
+
   return (
-    <div class="cl-overlay" onMouseDown={(e) => { if (e.target === e.currentTarget) onClose(); }}>
+    <div class="cl-overlay" onMouseDown={(e) => { if (e.target === e.currentTarget) requestClose(); }}>
-      <div class="cl-modal">
+      <div class="cl-modal cl-modal-full">
         <header class="cl-header">
           <span class="cl-title">Control logic</span>
           <span class="hint cl-subtitle">Server-side flows — run continuously, independent of any panel.</span>
           <div class="cl-header-actions">
             {graph && dirty && <span class="cl-dirty">unsaved</span>}
             {graph && <button class="panel-btn" disabled={busy || !dirty} onClick={saveGraph}>Save</button>}
-            <button class="panel-btn" onClick={onClose}>Close</button>
+            {graph && <button class={`panel-btn${showVersions ? ' panel-btn-primary' : ''}`}
+              onClick={() => setShowVersions(v => !v)}>History</button>}
+            <button class="panel-btn" onClick={requestClose}>Close</button>
           </div>
         </header>
 
@@ -293,12 +352,50 @@ export default function ControlLogicEditor({ onClose }: Props) {
                   </label>
                   <span class="hint">Saving a disabled graph stops it; enabling + saving starts it.</span>
                 </div>
+                <div class="cl-editor-main">
                   <FlowEditor graph={graph}
                     onChange={(g) => { setGraph({ ...graph, nodes: g.nodes, wires: g.wires }); setDirty(true); }} />
+                  {showVersions && (
+                    <div class="ver-pane">
+                      <div class="ver-pane-head">Version history</div>
+                      <VersionTree
+                        base={`/api/v1/controllogic/${encodeURIComponent(graph.id)}`}
+                        viewing={viewingVersion}
+                        dirty={dirty}
+                        reloadKey={verReload}
+                        onView={viewVersion}
+                        onForked={async (newId) => { await reload(); setSelectedId(newId); const r = await fetch(`/api/v1/controllogic/${encodeURIComponent(newId)}`); if (r.ok) { setGraph(await r.json()); setViewingVersion(null); setDirty(false); } }}
+                        onPromoted={async () => { await reload(); const r = await fetch(`/api/v1/controllogic/${encodeURIComponent(graph.id)}`); if (r.ok) { setGraph(await r.json()); setViewingVersion(null); setDirty(false); } setVerReload(k => k + 1); }}
+                        onCompare={(av, bv) => setDiff({ av, bv })}
+                        onError={setError} />
+                    </div>
+                  )}
+                </div>
               </Fragment>
             )}
           </div>
         </div>
+
+        {diff && graph && (
+          <DiffViewer base={`/api/v1/controllogic/${encodeURIComponent(graph.id)}`}
+            av={diff.av} bv={diff.bv} title={`${graph.name} — v${diff.av} → v${diff.bv}`}
+            onClose={() => setDiff(null)} />
+        )}
+
+        {showCloseConfirm && (
+          <div class="cl-confirm-overlay" onMouseDown={(e) => { if (e.target === e.currentTarget) setShowCloseConfirm(false); }}>
+            <div class="cl-confirm">
+              <div class="cl-confirm-title">Unsaved changes</div>
+              <p class="hint">This graph has unsaved changes. What would you like to do?</p>
+              <div class="cl-confirm-actions">
+                <button class="panel-btn" onClick={() => setShowCloseConfirm(false)}>Cancel</button>
+                <button class="panel-btn" disabled={busy}
+                  onClick={() => { setShowCloseConfirm(false); onClose(); }}>Close without saving</button>
+                <button class="panel-btn panel-btn-primary" disabled={busy} onClick={saveAndClose}>Save and close</button>
+              </div>
+            </div>
+          </div>
+        )}
       </div>
     </div>
   );
@@ -317,6 +414,8 @@ function FlowEditor({ graph, onChange }: {
   const [selectedWire, setSelectedWire] = useState<number | null>(null);
   const [dataSources, setDataSources] = useState<string[]>([]);
   const [dsSignals, setDsSignals] = useState<Record<string, string[]>>({});
+  const [configInstances, setConfigInstances] = useState<{ id: string; name: string }[]>([]);
+  const [configSets, setConfigSets] = useState<{ id: string; name: string }[]>([]);
 
   const canvasRef = useRef<HTMLDivElement>(null);
   const dragNode = useRef<{ id: string; dx: number; dy: number } | null>(null);
@@ -329,6 +428,14 @@ function FlowEditor({ graph, onChange }: {
       .then(r => r.ok ? r.json() : [])
       .then((ds: DataSource[]) => setDataSources(ds.map(d => d.name)))
       .catch(() => {});
+    fetch('/api/v1/config/instances')
+      .then(r => r.ok ? r.json() : [])
+      .then((list: { id: string; name: string }[]) => setConfigInstances(list ?? []))
+      .catch(() => {});
+    fetch('/api/v1/config/sets')
+      .then(r => r.ok ? r.json() : [])
+      .then((list: { id: string; name: string }[]) => setConfigSets(list ?? []))
+      .catch(() => {});
   }, []);
 
   async function loadSignals(ds: string) {
@@ -341,12 +448,15 @@ function FlowEditor({ graph, onChange }: {
     } catch {}
   }
 
-  // Bare-name write targets are graph-local variables; offer them under 'local'.
+  // Graph-local write targets (bare name, or an explicit "local:" prefix) become
+  // the suggestions offered when the target data source is 'local'.
   const localNames = Array.from(new Set(
     nodes.filter(n => n.kind === 'action.write')
       .map(n => n.params.target ?? '')
+      .map(t => t.startsWith('local:') ? t.slice('local:'.length) : t)
       .filter(t => t && !t.includes(':'))
   ));
+  // 'srv' is a registered data source, so it already appears in dataSources.
   const dsOptions = ['local', 'sys', ...dataSources];
   function signalOptions(ds: string): string[] {
     if (ds === 'local') return localNames;
@@ -354,6 +464,15 @@ function FlowEditor({ graph, onChange }: {
     return dsSignals[ds] ?? [];
   }
 
+  // Flatten every known ds:name into a single list for the fuzzy SignalPicker,
+  // and a hook to lazily load all data sources' signals when a picker opens.
+  function allSignalOptions(): SignalOption[] {
+    const out: SignalOption[] = [];
+    for (const ds of dsOptions) for (const name of signalOptions(ds)) out.push({ ds, name });
+    return out;
+  }
+  function openAllSignals() { dsOptions.forEach(ds => loadSignals(ds)); }
+
   const selected = nodes.find(n => n.id === selectedNode) ?? null;
 
   useEffect(() => {
@@ -573,19 +692,13 @@ function FlowEditor({ graph, onChange }: {
             <div class="wizard-section-title">{KIND_LABEL[selected.kind]}</div>
 
             {(selected.kind === 'trigger.threshold' || selected.kind === 'trigger.change' || selected.kind === 'trigger.alarm') && (() => {
-              const { ds, name } = splitRef(selected.params.signal ?? '');
               return (
                 <Fragment>
-                  <div class="wizard-field">
-                    <label>Data source</label>
-                    <SearchableSelect value={ds} options={dataSources}
-                      onSelect={(newDs) => { loadSignals(newDs); patchParams(selected.id, { signal: `${newDs}:` }); }} />
-                  </div>
                   <div class="wizard-field">
                     <label>Signal</label>
-                    <SearchableSelect value={name} options={signalOptions(ds)}
+                    <SignalPicker value={selected.params.signal ?? ''} options={allSignalOptions()}
-                      onSelect={(sig) => patchParams(selected.id, { signal: `${ds}:${sig}` })}
+                      onOpen={openAllSignals}
-                      placeholder={ds ? 'Search signals…' : 'Select data source first'} />
+                      onChange={(ref) => patchParams(selected.id, { signal: ref })} />
                   </div>
                   {selected.kind === 'trigger.threshold' && (
                     <div class="wizard-field wizard-field-row">
@@ -661,7 +774,7 @@ function FlowEditor({ graph, onChange }: {
               <ExprField label="Condition" value={selected.params.cond ?? ''}
                 onChange={(v) => patchParams(selected.id, { cond: v })}
                 onInsert={(ds, sig) => insertRef(selected.id, 'cond', ds, sig)}
-                dsOptions={dsOptions} signalOptions={signalOptions} loadSignals={loadSignals}
+                allSignals={allSignalOptions()} onOpenSignals={openAllSignals}
                 hint="True → 'then' port, false → 'else'. e.g. {stub:level} > 5 && temp < 100. {sys:time}=epoch seconds, {sys:dt}=seconds since the trigger last fired." />
             )}
 
@@ -685,36 +798,30 @@ function FlowEditor({ graph, onChange }: {
                   <ExprField label="While condition" value={selected.params.cond ?? ''}
                     onChange={(v) => patchParams(selected.id, { cond: v })}
                     onInsert={(ds, sig) => insertRef(selected.id, 'cond', ds, sig)}
-                    dsOptions={dsOptions} signalOptions={signalOptions} loadSignals={loadSignals}
+                    allSignals={allSignalOptions()} onOpenSignals={openAllSignals}
                     hint="Loops the 'body' port while true (capped). e.g. {stub:level} < 90" />
                 )}
                 <p class="hint">Runs the <b>body</b> port repeatedly, then continues on <b>done</b>.</p>
               </Fragment>
             )}
 
-            {selected.kind === 'action.write' && (() => {
+            {selected.kind === 'action.write' && (
-              const { ds, name } = splitRef(selected.params.target ?? '');
-              return (
               <Fragment>
                 <div class="wizard-field">
-                    <label>Target data source</label>
+                  <label>Target signal / variable</label>
-                    <SearchableSelect value={ds} options={dsOptions}
+                  <SignalPicker value={selected.params.target ?? ''} options={allSignalOptions()}
-                      onSelect={(newDs) => { loadSignals(newDs); patchParams(selected.id, { target: `${newDs}:` }); }} />
+                    onOpen={openAllSignals} allowFreeform
-                  </div>
+                    onChange={(ref) => patchParams(selected.id, { target: ref })} />
-                  <div class="wizard-field">
+                  <p class="hint">Pick a signal, or type <code>local:name</code> for a graph-local var
-                    <label>Target signal</label>
+                    or <code>srv:name</code> for a server variable that panels can read.</p>
-                    <SearchableSelect value={name} options={signalOptions(ds)}
-                      onSelect={(sig) => patchParams(selected.id, { target: `${ds}:${sig}` })}
-                      placeholder={ds ? 'Search signals…' : 'Select data source first'} />
                 </div>
                 <ExprField label="Value (expression)" value={selected.params.expr ?? ''}
                   onChange={(v) => patchParams(selected.id, { expr: v })}
                   onInsert={(ds2, sig) => insertRef(selected.id, 'expr', ds2, sig)}
-                    dsOptions={dsOptions} signalOptions={signalOptions} loadSignals={loadSignals}
+                  allSignals={allSignalOptions()} onOpenSignals={openAllSignals}
-                    hint="Write to a data source signal, or a bare name to store a graph-local var. e.g. ({stub:a} - {stub:b}) / {sys:dt}." />
+                  hint="Write to a data source signal, a bare local var, or srv:name for a server variable panels can read. e.g. ({stub:a} - {stub:b}) / {sys:dt}." />
               </Fragment>
-              );
+            )}
-            })()}
 
             {selected.kind === 'action.delay' && (
               <div class="wizard-field">
@@ -735,7 +842,7 @@ function FlowEditor({ graph, onChange }: {
                 <ExprField label="Value (expression)" value={selected.params.expr ?? ''}
                   onChange={(v) => patchParams(selected.id, { expr: v })}
                   onInsert={(ds2, sig) => insertRef(selected.id, 'expr', ds2, sig)}
-                  dsOptions={dsOptions} signalOptions={signalOptions} loadSignals={loadSignals}
+                  allSignals={allSignalOptions()} onOpenSignals={openAllSignals}
                   hint="Logs this value to the server log — handy for debugging a flow." />
               </Fragment>
             )}
@@ -753,6 +860,172 @@ function FlowEditor({ graph, onChange }: {
               </div>
             )}
 
+            {selected.kind === 'action.dialog' && (
+              <Fragment>
+                <div class="wizard-field">
+                  <label>Type</label>
+                  <select class="prop-input" value={selected.params.kind ?? 'info'}
+                    onChange={(e) => patchParams(selected.id, { kind: (e.target as HTMLSelectElement).value })}>
+                    <option value="info">Info</option>
+                    <option value="error">Error</option>
+                    <option value="input">Input (ask for a value)</option>
+                  </select>
+                </div>
+                <div class="wizard-field">
+                  <label>Title</label>
+                  <input class="prop-input" value={selected.params.title ?? ''}
+                    placeholder="dialog title"
+                    onInput={(e) => patchParams(selected.id, { title: (e.target as HTMLInputElement).value })} />
+                </div>
+                <div class="wizard-field">
+                  <label>Message</label>
+                  <textarea class="prop-input" rows={3} value={selected.params.message ?? ''}
+                    placeholder="shown to the user"
+                    onInput={(e) => patchParams(selected.id, { message: (e.target as HTMLTextAreaElement).value })} />
+                </div>
+                {selected.params.kind === 'input' && (
+                  <div class="wizard-field">
+                    <label>Response variable</label>
+                    <input class="prop-input" value={selected.params.target ?? ''}
+                      placeholder="srv:approved"
+                      onInput={(e) => patchParams(selected.id, { target: (e.target as HTMLInputElement).value })} />
+                    <p class="hint">The user's number is written here (e.g. <code>srv:approved</code>); read it on a later activation.</p>
+                  </div>
+                )}
+                <div class="wizard-field">
+                  <label>Users (optional)</label>
+                  <input class="prop-input" value={selected.params.users ?? ''}
+                    placeholder="alice, bob"
+                    onInput={(e) => patchParams(selected.id, { users: (e.target as HTMLInputElement).value })} />
+                </div>
+                <div class="wizard-field">
+                  <label>Groups (optional)</label>
+                  <input class="prop-input" value={selected.params.groups ?? ''}
+                    placeholder="operators"
+                    onInput={(e) => patchParams(selected.id, { groups: (e.target as HTMLInputElement).value })} />
+                  <p class="hint">Comma-separated. Leave both empty to show the dialog to every connected user.</p>
+                </div>
+              </Fragment>
+            )}
+
+            {selected.kind === 'action.config.apply' && (
+              <div class="wizard-field">
+                <label>Config instance</label>
+                <select class="prop-select" value={selected.params.instance ?? ''}
+                  onChange={(e) => patchParams(selected.id, { instance: (e.target as HTMLSelectElement).value })}>
+                  <option value="">choose…</option>
+                  {configInstances.map(ci => <option key={ci.id} value={ci.id}>{ci.name}</option>)}
+                </select>
+                <p class="hint">Applies the instance's current values to every bound signal (like the
+                  Apply button in the config manager). Each write is audited.</p>
+              </div>
+            )}
+
+            {selected.kind === 'action.config.read' && (
+              <Fragment>
+                <div class="wizard-field">
+                  <label>Config instance</label>
+                  <select class="prop-select" value={selected.params.instance ?? ''}
+                    onChange={(e) => patchParams(selected.id, { instance: (e.target as HTMLSelectElement).value })}>
+                    <option value="">choose…</option>
+                    {configInstances.map(ci => <option key={ci.id} value={ci.id}>{ci.name}</option>)}
+                  </select>
+                </div>
+                <div class="wizard-field">
+                  <label>Parameter key</label>
+                  <input class="prop-input" value={selected.params.key ?? ''}
+                    placeholder="parameter key"
+                    onInput={(e) => patchParams(selected.id, { key: (e.target as HTMLInputElement).value })} />
+                </div>
+                <div class="wizard-field">
+                  <label>Target signal / variable</label>
+                  <SignalPicker value={selected.params.target ?? ''} options={allSignalOptions()}
+                    onOpen={openAllSignals} allowFreeform
+                    onChange={(ref) => patchParams(selected.id, { target: ref })} />
+                  <p class="hint">Reads the named parameter's value and writes it to this target. Only
+                    numeric values are supported.</p>
+                </div>
+              </Fragment>
+            )}
+
+            {selected.kind === 'action.config.write' && (
+              <Fragment>
+                <div class="wizard-field">
+                  <label>Config instance</label>
+                  <select class="prop-select" value={selected.params.instance ?? ''}
+                    onChange={(e) => patchParams(selected.id, { instance: (e.target as HTMLSelectElement).value })}>
+                    <option value="">choose…</option>
+                    {configInstances.map(ci => <option key={ci.id} value={ci.id}>{ci.name}</option>)}
+                  </select>
+                </div>
+                <div class="wizard-field">
+                  <label>Parameter key</label>
+                  <input class="prop-input" value={selected.params.key ?? ''}
+                    placeholder="parameter key"
+                    onInput={(e) => patchParams(selected.id, { key: (e.target as HTMLInputElement).value })} />
+                </div>
+                <div class="wizard-field">
+                  <label>Value expression</label>
+                  <input class="prop-input" value={selected.params.expr ?? ''}
+                    placeholder="e.g. {ds:signal} * 2"
+                    onInput={(e) => patchParams(selected.id, { expr: (e.target as HTMLInputElement).value })} />
+                  <p class="hint">Evaluates the expression and stores it into the named parameter, creating a
+                    new instance revision. Only numeric values are supported; the value is coerced to the
+                    parameter's declared type.</p>
+                </div>
+              </Fragment>
+            )}
+
+            {selected.kind === 'action.config.create' && (
+              <Fragment>
+                <div class="wizard-field">
+                  <label>Config set</label>
+                  <select class="prop-select" value={selected.params.set ?? ''}
+                    onChange={(e) => patchParams(selected.id, { set: (e.target as HTMLSelectElement).value })}>
+                    <option value="">choose…</option>
+                    {configSets.map(cs => <option key={cs.id} value={cs.id}>{cs.name}</option>)}
+                  </select>
+                </div>
+                <div class="wizard-field">
+                  <label>New instance name</label>
+                  <input class="prop-input" value={selected.params.name ?? ''}
+                    placeholder="auto"
+                    onInput={(e) => patchParams(selected.id, { name: (e.target as HTMLInputElement).value })} />
+                </div>
+                <div class="wizard-field">
+                  <label>Copy values from</label>
+                  <select class="prop-select" value={selected.params.from ?? ''}
+                    onChange={(e) => patchParams(selected.id, { from: (e.target as HTMLSelectElement).value })}>
+                    <option value="">defaults (empty)</option>
+                    {configInstances.map(ci => <option key={ci.id} value={ci.id}>{ci.name}</option>)}
+                  </select>
+                  <p class="hint">Creates a new instance for the chosen set, optionally seeded from an existing
+                    instance's values. The new id is logged to the audit trail.</p>
+                </div>
+              </Fragment>
+            )}
+
+            {selected.kind === 'action.config.snapshot' && (
+              <Fragment>
+                <div class="wizard-field">
+                  <label>Config set</label>
+                  <select class="prop-select" value={selected.params.set ?? ''}
+                    onChange={(e) => patchParams(selected.id, { set: (e.target as HTMLSelectElement).value })}>
+                    <option value="">choose…</option>
+                    {configSets.map(cs => <option key={cs.id} value={cs.id}>{cs.name}</option>)}
+                  </select>
+                </div>
+                <div class="wizard-field">
+                  <label>New instance name</label>
+                  <input class="prop-input" value={selected.params.name ?? ''}
+                    placeholder="(auto)"
+                    onInput={(e) => patchParams(selected.id, { name: (e.target as HTMLInputElement).value })} />
+                  <p class="hint">Reads the current live value of every target signal of the set and stores
+                    them as a new instance. The new id is logged to the audit trail.</p>
+                </div>
+              </Fragment>
+            )}
+
             <button class="panel-btn" style="margin-top:1rem;" onClick={() => deleteNode(selected.id)}>Delete node</button>
           </Fragment>
         )}
@@ -774,17 +1047,15 @@ function FlowEditor({ graph, onChange }: {
   }
 }
 
-function ExprField({ label, value, onChange, onInsert, dsOptions, signalOptions, loadSignals, hint }: {
+function ExprField({ label, value, onChange, onInsert, allSignals, onOpenSignals, hint }: {
   label: string;
   value: string;
   onChange: (v: string) => void;
   onInsert: (ds: string, sig: string) => void;
-  dsOptions: string[];
+  allSignals: SignalOption[];
-  signalOptions: (ds: string) => string[];
+  onOpenSignals: () => void;
-  loadSignals: (ds: string) => void;
   hint: string;
 }) {
-  const [insDs, setInsDs] = useState('');
   const err = checkExpr(value);
   return (
     <div class="wizard-field">
@@ -794,11 +1065,9 @@ function ExprField({ label, value, onChange, onInsert, dsOptions, signalOptions,
         onInput={(e) => onChange((e.target as HTMLInputElement).value)} />
       {err && <p class="wizard-error">{err}</p>}
       <div class="flow-expr-insert">
-        <SearchableSelect value={insDs} options={dsOptions}
+        <SignalPicker value="" options={allSignals} onOpen={onOpenSignals}
-          onSelect={(ds) => { setInsDs(ds); loadSignals(ds); }} placeholder="ds…" />
+          placeholder="+ insert signal"
-        <SearchableSelect value="" options={signalOptions(insDs)}
+          onChange={(ref) => { const s = splitRef(ref); onInsert(s.ds, s.name); }} />
-          onSelect={(sig) => onInsert(insDs, sig)}
-          placeholder={insDs ? '+ insert signal' : 'pick ds first'} />
       </div>
       <p class="hint">{hint}</p>
     </div>
@@ -821,6 +1090,7 @@ function nodeSummary(n: CLNode): string {
     case 'action.delay':      return `wait ${n.params.ms || '0'} ms`;
     case 'action.log':        return `log ${n.params.label ? n.params.label + ': ' : ''}${n.params.expr || ''}`;
     case 'action.lua':        return 'Lua script';
+    case 'action.dialog':     return `${n.params.kind || 'info'} dialog${n.params.title ? ': ' + n.params.title : ''}`;
     default:                  return '';
   }
 }

web/src/CueEditor.tsx

@@ -0,0 +1,259 @@
+import { h } from 'preact';
+import { useRef, useState } from 'preact/hooks';
+
+// ── Tokenizer ─────────────────────────────────────────────────────────────────
+
+type TT = 'kw' | 'type' | 'str' | 'cmt' | 'num' | 'attr' | 'text';
+
+const CUE_KEYWORDS = new Set([
+  'package', 'import', 'for', 'in', 'if', 'let', 'true', 'false', 'null',
+]);
+const CUE_TYPES = new Set([
+  'number', 'int', 'float', 'string', 'bytes', 'bool', 'uint', 'rune',
+]);
+
+// Identifiers that make sensible always-available completions.
+const CUE_COMPLETION_WORDS = [...CUE_KEYWORDS, ...CUE_TYPES];
+
+interface Tok { t: TT; s: string; }
+
+function isAlpha(c: string) { return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c === '_' || c === '#'; }
+function isAlNum(c: string) { return isAlpha(c) || (c >= '0' && c <= '9'); }
+function isDigit(c: string) { return c >= '0' && c <= '9'; }
+
+function tokenize(src: string): Tok[] {
+  const out: Tok[] = [];
+  let i = 0;
+
+  while (i < src.length) {
+    const c = src[i];
+
+    // Line comment
+    if (c === '/' && src[i + 1] === '/') {
+      const end = src.indexOf('\n', i);
+      const stop = end < 0 ? src.length : end;
+      out.push({ t: 'cmt', s: src.slice(i, stop) });
+      i = stop;
+      continue;
+    }
+
+    // Multiline string """...""" or '''...'''
+    if ((c === '"' || c === "'") && src[i + 1] === c && src[i + 2] === c) {
+      const q = c + c + c;
+      const end = src.indexOf(q, i + 3);
+      const stop = end < 0 ? src.length : end + 3;
+      out.push({ t: 'str', s: src.slice(i, stop) });
+      i = stop;
+      continue;
+    }
+
+    // String "..." or '...'
+    if (c === '"' || c === "'") {
+      let j = i + 1;
+      while (j < src.length) {
+        if (src[j] === '\\') { j += 2; continue; }
+        if (src[j] === c || src[j] === '\n') { j++; break; }
+        j++;
+      }
+      out.push({ t: 'str', s: src.slice(i, j) });
+      i = j;
+      continue;
+    }
+
+    // Number
+    if (isDigit(c) || (c === '.' && isDigit(src[i + 1] ?? ''))) {
+      let j = i;
+      while (j < src.length && (isDigit(src[j]) || src[j] === '.' || src[j] === '_')) j++;
+      if (j < src.length && (src[j] === 'e' || src[j] === 'E')) {
+        j++;
+        if (src[j] === '+' || src[j] === '-') j++;
+        while (j < src.length && isDigit(src[j])) j++;
+      }
+      out.push({ t: 'num', s: src.slice(i, j) });
+      i = j;
+      continue;
+    }
+
+    // Identifier / keyword / field label
+    if (isAlpha(c)) {
+      let j = i;
+      while (j < src.length && isAlNum(src[j])) j++;
+      const word = src.slice(i, j);
+      // Peek past spaces for a ':' => this identifier is a field label.
+      let k = j;
+      while (k < src.length && (src[k] === ' ' || src[k] === '\t')) k++;
+      let t: TT = 'text';
+      if (CUE_KEYWORDS.has(word)) t = 'kw';
+      else if (CUE_TYPES.has(word)) t = 'type';
+      else if (src[k] === ':') t = 'attr';
+      out.push({ t, s: word });
+      i = j;
+      continue;
+    }
+
+    out.push({ t: 'text', s: c });
+    i++;
+  }
+
+  return out;
+}
+
+function renderTokens(src: string) {
+  return tokenize(src).map((tok, idx) =>
+    tok.t === 'text'
+      ? <span key={idx}>{tok.s}</span>
+      : <span key={idx} class={`cue-${tok.t}`}>{tok.s}</span>
+  );
+}
+
+// ── Caret coordinates (mirror technique) ──────────────────────────────────────
+
+function caretXY(ta: HTMLTextAreaElement): { left: number; top: number; lineHeight: number } {
+  const style = getComputedStyle(ta);
+  const div = document.createElement('div');
+  const props = [
+    'boxSizing', 'width', 'paddingTop', 'paddingRight', 'paddingBottom', 'paddingLeft',
+    'borderTopWidth', 'borderRightWidth', 'borderBottomWidth', 'borderLeftWidth',
+    'fontFamily', 'fontSize', 'fontWeight', 'lineHeight', 'letterSpacing', 'tabSize',
+  ] as const;
+  for (const p of props) (div.style as any)[p] = (style as any)[p];
+  div.style.position = 'absolute';
+  div.style.visibility = 'hidden';
+  div.style.whiteSpace = 'pre-wrap';
+  div.style.wordWrap = 'break-word';
+  div.style.overflow = 'hidden';
+
+  div.textContent = ta.value.slice(0, ta.selectionStart);
+  const marker = document.createElement('span');
+  marker.textContent = ta.value.slice(ta.selectionStart) || '.';
+  div.appendChild(marker);
+  document.body.appendChild(div);
+  const lineHeight = parseFloat(style.lineHeight) || (parseFloat(style.fontSize) * 1.4);
+  const top = marker.offsetTop - ta.scrollTop;
+  const left = marker.offsetLeft - ta.scrollLeft;
+  document.body.removeChild(div);
+  return { left, top, lineHeight };
+}
+
+// ── Component ─────────────────────────────────────────────────────────────────
+
+interface Props {
+  value: string;
+  onChange: (v: string) => void;
+  rows?: number;
+  /** Parameter/signal names offered alongside the CUE vocabulary. */
+  completions?: string[];
+}
+
+interface AC { items: string[]; index: number; from: number; left: number; top: number; }
+
+export default function CueEditor({ value, onChange, rows = 14, completions = [] }: Props) {
+  const preRef = useRef<HTMLPreElement>(null);
+  const taRef = useRef<HTMLTextAreaElement>(null);
+  const [ac, setAc] = useState<AC | null>(null);
+
+  const vocab = [...new Set([...completions, ...CUE_COMPLETION_WORDS])];
+
+  function syncScroll(e: Event) {
+    const ta = e.target as HTMLTextAreaElement;
+    if (preRef.current) {
+      preRef.current.scrollTop = ta.scrollTop;
+      preRef.current.scrollLeft = ta.scrollLeft;
+    }
+  }
+
+  function wordPrefix(ta: HTMLTextAreaElement): { word: string; from: number } {
+    const caret = ta.selectionStart;
+    let from = caret;
+    while (from > 0 && /[A-Za-z0-9_#]/.test(ta.value[from - 1])) from--;
+    return { word: ta.value.slice(from, caret), from };
+  }
+
+  function refreshAC(ta: HTMLTextAreaElement) {
+    const { word, from } = wordPrefix(ta);
+    if (word.length < 1) { setAc(null); return; }
+    const lower = word.toLowerCase();
+    const items = vocab.filter((w) => w.toLowerCase().startsWith(lower) && w !== word).slice(0, 8);
+    if (items.length === 0) { setAc(null); return; }
+    const { left, top, lineHeight } = caretXY(ta);
+    const rect = ta.getBoundingClientRect();
+    setAc({ items, index: 0, from, left: rect.left + left, top: rect.top + top + lineHeight });
+  }
+
+  function accept(item: string) {
+    const ta = taRef.current;
+    if (!ta || !ac) return;
+    const caret = ta.selectionStart;
+    const next = value.slice(0, ac.from) + item + value.slice(caret);
+    onChange(next);
+    setAc(null);
+    const pos = ac.from + item.length;
+    requestAnimationFrame(() => {
+      ta.focus();
+      ta.setSelectionRange(pos, pos);
+    });
+  }
+
+  function onKeyDown(e: KeyboardEvent) {
+    if (!ac) {
+      // Ctrl+Space forces the completion popup open.
+      if (e.key === ' ' && e.ctrlKey) {
+        e.preventDefault();
+        refreshAC(e.target as HTMLTextAreaElement);
+      }
+      return;
+    }
+    switch (e.key) {
+      case 'ArrowDown':
+        e.preventDefault();
+        setAc({ ...ac, index: (ac.index + 1) % ac.items.length });
+        break;
+      case 'ArrowUp':
+        e.preventDefault();
+        setAc({ ...ac, index: (ac.index - 1 + ac.items.length) % ac.items.length });
+        break;
+      case 'Enter':
+      case 'Tab':
+        e.preventDefault();
+        accept(ac.items[ac.index]);
+        break;
+      case 'Escape':
+        e.preventDefault();
+        setAc(null);
+        break;
+    }
+  }
+
+  return (
+    <div class="cue-editor" style={`height:${rows * 1.5}em;`}>
+      <pre ref={preRef} class="cue-pre" aria-hidden="true">
+        {renderTokens(value)}
+        {'\n'}
+      </pre>
+      <textarea
+        ref={taRef}
+        class="cue-textarea"
+        value={value}
+        spellcheck={false}
+        autocomplete="off"
+        onInput={(e) => { onChange((e.target as HTMLTextAreaElement).value); refreshAC(e.target as HTMLTextAreaElement); }}
+        onKeyDown={onKeyDown}
+        onScroll={syncScroll}
+        onBlur={() => setTimeout(() => setAc(null), 120)}
+      />
+      {ac && (
+        <ul class="cue-ac" style={`left:${ac.left}px;top:${ac.top}px;`}>
+          {ac.items.map((it, i) => (
+            <li
+              key={it}
+              class={i === ac.index ? 'cue-ac-item active' : 'cue-ac-item'}
+              onMouseDown={(e) => { e.preventDefault(); accept(it); }}
+            >
+              {it}
+            </li>
+          ))}
+        </ul>
+      )}
+    </div>
+  );
+}

web/src/EditCanvas.tsx

@@ -35,6 +35,7 @@ export const DEFAULT_SIZES: Record<string, [number, number]> = {
   plot:      [400, 200],
   image:     [200, 150],
   link:      [140, 50],
+  configselect: [220, 50],
 };
 
 // Widget types that support multiple signals (signal can be appended)

web/src/EditMode.tsx

@@ -8,24 +8,16 @@ import EditCanvas, { genWidgetId, DEFAULT_SIZES } from './EditCanvas';
 import PlotPanelCanvas from './PlotPanelCanvas';
 import LogicEditor from './LogicEditor';
 import PropertiesPane from './PropertiesPane';
-import ContextualHelp from './ContextualHelp';
 import HelpModal from './HelpModal';
 import ZoomControl from './ZoomControl';
 import { useAuth, canWrite } from './lib/auth';
+import { VersionTree, DiffViewer } from './VersionHistory';
 
 interface Props {
   initial: Interface | null;
   onDone: (iface: Interface | null) => void;
 }
 
-interface VersionMeta {
-  version: number;
-  name: string;
-  tag?: string;
-  current: boolean;
-  savedAt: string;
-}
-
 function blankInterface(): Interface {
   return { id: '', name: 'New Interface', version: 1, w: 1200, h: 800, widgets: [] };
 }
@@ -84,6 +76,7 @@ const STATIC_WIDGET_TYPES = [
   { type: 'button',    label: 'Action Button' },
   { type: 'image',     label: 'Image' },
   { type: 'link',      label: 'Link' },
+  { type: 'configselect', label: 'Config Selector' },
 ];
 
 export default function EditMode({ initial, onDone }: Props) {
@@ -106,8 +99,9 @@ export default function EditMode({ initial, onDone }: Props) {
 
   // History panel
   const [showHistory, setShowHistory] = useState(false);
-  const [versions, setVersions] = useState<VersionMeta[]>([]);
+  const [viewingVersion, setViewingVersion] = useState<number | null>(null);
-  const [historyLoading, setHistoryLoading] = useState(false);
+  const [diff, setDiff] = useState<{ av: number; bv: number } | null>(null);
+  const [verReload, setVerReload] = useState(0);
   const [tag, setTag] = useState('');
   // Bumped whenever the editor content is replaced wholesale (version load /
   // promote) to force a full canvas remount, so no stale widget state lingers.
@@ -329,6 +323,7 @@ export default function EditMode({ initial, onDone }: Props) {
       options:
         type === 'textlabel' ? { label: 'Label' } :
         type === 'button'    ? { label: 'Button', mode: 'oneshot' } :
+        type === 'configselect' ? { label: 'Config', set: '', output: '', instances: '' } :
         {},
     };
     handleWidgetsChange([...(iface.widgets || []), newWidget]);
@@ -360,7 +355,8 @@ export default function EditMode({ initial, onDone }: Props) {
       setDirty(false);
       setTag('');
       window.dispatchEvent(new CustomEvent('uopi:refresh-interfaces'));
-      if (showHistory) loadVersions();
+      setViewingVersion(null);
+      setVerReload(k => k + 1);
     } catch (err) {
       setError(err instanceof Error ? err.message : String(err));
     } finally {
@@ -371,26 +367,12 @@ export default function EditMode({ initial, onDone }: Props) {
 
   // ── Version history ────────────────────────────────────────────────────────
 
-  const loadVersions = useCallback(async () => {
-    if (!iface.id) { setVersions([]); return; }
-    setHistoryLoading(true);
-    try {
-      const res = await fetch(`/api/v1/interfaces/${encodeURIComponent(iface.id)}/versions`);
-      if (!res.ok) throw new Error(`Load versions failed (${res.status})`);
-      setVersions(await res.json());
-    } catch (err) {
-      setError(err instanceof Error ? err.message : String(err));
-    } finally {
-      setHistoryLoading(false);
-    }
-  }, [iface.id]);
-
   const toggleHistory = useCallback(() => {
     setShowHistory(s => {
-      if (!s) loadVersions();
+      if (!s) setVerReload(k => k + 1);
       return !s;
     });
-  }, [loadVersions]);
+  }, []);
 
   // Load a past revision into the editor non-destructively: the current id is
   // preserved, so saving the restored content creates a new revision on top.
@@ -404,45 +386,26 @@ export default function EditMode({ initial, onDone }: Props) {
       restored.id = iface.id; // keep editing the same interface
       setIface(restored);
       setSelectedIds([]);
-      setDirty(true);
+      // Viewing a past revision is not itself a change — only subsequent edits
+      // dirty the editor (saving then promotes it to a new revision).
+      setDirty(false);
       setCanvasNonce(n => n + 1);
       undoStack.current = [];
       redoStack.current = [];
       setHistoryLen(0);
+      setViewingVersion(version);
     } catch (err) {
       setError(err instanceof Error ? err.message : String(err));
     }
   }, [iface.id, dirty]);
 
-  // Edit (or clear) the label of an existing revision in place.
+  // Reload the now-current interface content into the editor (after a promote,
-  const editVersionTag = useCallback(async (version: number, currentTag: string) => {
+  // which the VersionTree performs server-side).
+  const reloadCurrentIface = useCallback(async () => {
     if (!iface.id) return;
-    const next = prompt('Label for this version (leave empty to clear):', currentTag ?? '');
-    if (next === null) return;
     try {
-      const res = await fetch(
-        `/api/v1/interfaces/${encodeURIComponent(iface.id)}/versions/${version}/tag?tag=${encodeURIComponent(next)}`,
-        { method: 'PUT' },
-      );
-      if (!res.ok) throw new Error(`Tag update failed (${res.status})`);
-      loadVersions();
-    } catch (err) {
-      setError(err instanceof Error ? err.message : String(err));
-    }
-  }, [iface.id, loadVersions]);
-
-  // Make a past revision the current one (saved as a new revision on top).
-  const promoteVersion = useCallback(async (version: number) => {
-    if (!iface.id) return;
-    if (dirty && !confirm('You have unsaved changes that will be discarded. Set this version as current?')) return;
-    try {
-      const res = await fetch(
-        `/api/v1/interfaces/${encodeURIComponent(iface.id)}/versions/${version}/promote`,
-        { method: 'POST' },
-      );
-      if (!res.ok) throw new Error(`Promote failed (${res.status})`);
-      // Reload the now-current interface content into the editor.
       const cur = await fetch(`/api/v1/interfaces/${encodeURIComponent(iface.id)}`);
+      if (!cur.ok) throw new Error(`Reload failed (${cur.status})`);
       const reloaded = parseInterface(await cur.text());
       setIface(reloaded);
       setSelectedIds([]);
@@ -451,25 +414,9 @@ export default function EditMode({ initial, onDone }: Props) {
       undoStack.current = [];
       redoStack.current = [];
       setHistoryLen(0);
+      setViewingVersion(null);
       window.dispatchEvent(new CustomEvent('uopi:refresh-interfaces'));
-      loadVersions();
+      setVerReload(k => k + 1);
-    } catch (err) {
-      setError(err instanceof Error ? err.message : String(err));
-    }
-  }, [iface.id, dirty, loadVersions]);
-
-  // Fork a revision into a brand-new interface.
-  const forkVersion = useCallback(async (version: number) => {
-    if (!iface.id) return;
-    try {
-      const res = await fetch(
-        `/api/v1/interfaces/${encodeURIComponent(iface.id)}/versions/${version}/fork`,
-        { method: 'POST' },
-      );
-      if (!res.ok) throw new Error(`Fork failed (${res.status})`);
-      const json = await res.json();
-      window.dispatchEvent(new CustomEvent('uopi:refresh-interfaces'));
-      alert(`Forked into new interface "${json.id}". Open it from the interface list.`);
     } catch (err) {
       setError(err instanceof Error ? err.message : String(err));
     }
@@ -626,7 +573,6 @@ export default function EditMode({ initial, onDone }: Props) {
 
         <div class="toolbar-right">
           <ZoomControl />
-          <ContextualHelp mode="edit" onOpenManual={openHelp} />
           <button class="icon-btn help-manual-btn" onClick={() => openHelp('edit')} title="Open user manual">📖</button>
           <button class="toolbar-btn" onClick={handleImport}>Import</button>
           <button class="toolbar-btn" onClick={handleExport}>Export</button>
@@ -735,49 +681,31 @@ export default function EditMode({ initial, onDone }: Props) {
                 Save snapshot
               </button>
             </div>
-            <div class="history-list">
+            {!iface.id ? (
-              {historyLoading && <div class="history-empty">Loading…</div>}
+              <div class="history-empty">Save the interface first to enable history.</div>
-              {!historyLoading && versions.length === 0 && (
+            ) : (
-                <div class="history-empty">No saved versions yet.</div>
+              <VersionTree
+                base={`/api/v1/interfaces/${encodeURIComponent(iface.id)}`}
+                viewing={viewingVersion}
+                dirty={dirty}
+                canWrite={writable}
+                reloadKey={verReload}
+                onView={loadVersion}
+                onForked={() => window.dispatchEvent(new CustomEvent('uopi:refresh-interfaces'))}
+                onPromoted={reloadCurrentIface}
+                onCompare={(av, bv) => setDiff({ av, bv })}
+                onError={setError} />
             )}
-              {!historyLoading && versions.map(v => (
-                <div
-                  key={v.version}
-                  class={`history-item${v.current ? ' history-item-current' : ''}`}
-                >
-                  <div class="history-item-main">
-                    <span class="history-version">v{v.version}</span>
-                    {v.tag && <span class="history-tag">{v.tag}</span>}
-                    {v.current && <span class="history-current-badge">current</span>}
-                  </div>
-                  <div class="history-item-meta">
-                    {new Date(v.savedAt).toLocaleString()}
-                  </div>
-                  <div class="history-item-actions">
-                    {!v.current && (
-                      <button class="history-action-btn" onClick={() => loadVersion(v.version)} title="Load this version into the editor (does not change history)">
-                        Load
-                      </button>
-                    )}
-                    {!v.current && (
-                      <button class="history-action-btn" onClick={() => promoteVersion(v.version)} title="Make this version the current one">
-                        Set current
-                      </button>
-                    )}
-                    <button class="history-action-btn" onClick={() => forkVersion(v.version)} title="Create a new interface from this version">
-                      Fork
-                    </button>
-                    <button class="history-action-btn" onClick={() => editVersionTag(v.version, v.tag ?? '')} title="Edit this version's label">
-                      Label
-                    </button>
-                  </div>
-                </div>
-              ))}
-            </div>
           </div>
         )}
       </div>
 
+      {diff && iface.id && (
+        <DiffViewer base={`/api/v1/interfaces/${encodeURIComponent(iface.id)}`}
+          av={diff.av} bv={diff.bv} title={`${iface.name} — v${diff.av} → v${diff.bv}`}
+          onClose={() => setDiff(null)} />
+      )}
+
       {showHelp && (
         <HelpModal initialSection={helpSection} onClose={() => setShowHelp(false)} />
       )}

web/src/HelpModal.tsx

@@ -403,6 +403,7 @@ function DiagramSignalTree() {
 
 const SECTIONS = [
   { id: 'start',     label: 'Getting Started' },
+  { id: 'tips',      label: 'Quick Tips' },
   { id: 'view',      label: 'View Mode' },
   { id: 'edit',      label: 'Edit Mode' },
   { id: 'widgets',   label: 'Widgets' },
@@ -411,10 +412,68 @@ const SECTIONS = [
   { id: 'logic',     label: 'Panel Logic' },
   { id: 'control',   label: 'Control Logic' },
   { id: 'sharing',   label: 'Sharing & Access' },
+  { id: 'audit',     label: 'Audit Log' },
   { id: 'history',   label: 'Historical Data' },
   { id: 'shortcuts', label: 'Keyboard Shortcuts' },
 ];
 
+// Quick tips, grouped by the mode they apply to. Each links to the manual
+// section that covers it in depth. (Previously surfaced via a floating
+// contextual-help popover; now consolidated here in the manual.)
+const TIPS: Record<'view' | 'edit', Array<{ text: string; section: string }>> = {
+  view: [
+    { text: 'Click any interface in the left panel to load it on the canvas.', section: 'view' },
+    { text: 'Right-click a widget to view signal info or export data as CSV.', section: 'view' },
+    { text: 'The ● Live button shows live streaming is active. Use the date pickers to load historical data.', section: 'history' },
+    { text: 'Click Edit (top-right) to open the drag-and-drop panel builder.', section: 'edit' },
+    { text: 'Use the Share button on a panel to grant access to users or groups.', section: 'sharing' },
+    { text: 'The ⚙ Control logic button opens server-side automation that runs even with no panel open.', section: 'control' },
+    { text: 'The 🛡 Audit button (for permitted users) opens the log of system-affecting actions.', section: 'audit' },
+    { text: 'The status chip turns green and shows your username when the WebSocket is connected.', section: 'view' },
+  ],
+  edit: [
+    { text: 'Drag a signal from the left tree onto the canvas to create a widget.', section: 'edit' },
+    { text: 'Click a widget to select it, then adjust its properties on the right.', section: 'edit' },
+    { text: 'Ctrl+click to select multiple widgets; then use the align toolbar.', section: 'edit' },
+    { text: 'Ctrl+Z to undo, Ctrl+Y to redo. Up to 50 steps are remembered.', section: 'shortcuts' },
+    { text: 'Use "+ Synthetic" in the signal tree to create computed/filtered signals.', section: 'signals' },
+    { text: 'Switch to the Logic tab to add interactive behaviour with a node-graph flow editor.', section: 'logic' },
+    { text: 'Add Local variables for set-points and counters that live inside the panel.', section: 'edit' },
+    { text: 'Arrow keys nudge the selected widget by 1 px (Shift for grid size).', section: 'shortcuts' },
+  ],
+};
+
+function SectionTips({ onNavigate }: { onNavigate: (section: string) => void }) {
+  const groups: Array<['view' | 'edit', string]> = [
+    ['view', 'In View mode'],
+    ['edit', 'In Edit mode'],
+  ];
+  return (
+    <div>
+      <p class="help-lead">
+        A handful of quick pointers to get the most out of uopi. Click any tip to jump to the
+        section that explains it in detail.
+      </p>
+      {groups.map(([mode, title]) => (
+        <div key={mode}>
+          <h3 class="help-h3">{title}</h3>
+          <ul class="help-tips-list">
+            {TIPS[mode].map(tip => (
+              <li key={tip.text}>
+                <button class="help-tip-item" onClick={() => onNavigate(tip.section)}>
+                  <span class="help-tip-icon">💡</span>
+                  <span class="help-tip-text">{tip.text}</span>
+                  <span class="help-tip-go">↗</span>
+                </button>
+              </li>
+            ))}
+          </ul>
+        </div>
+      ))}
+    </div>
+  );
+}
+
 function SectionStart() {
   return (
     <div>
@@ -481,8 +540,10 @@ function SectionView() {
 
       <h3 class="help-h3">Connection status</h3>
       <p>
-        The coloured chip in the top-right shows the WebSocket connection state.
+        The coloured chip in the top-right shows the WebSocket connection state. When connected it
-        A red <em>"disconnected"</em> banner appears at the top while reconnecting — live values will resume automatically.
+        reads <em>"connected as &lt;your username&gt;"</em>, so you can confirm the identity your
+        actions are attributed to in the audit log. A red <em>"disconnected"</em> banner appears at
+        the top while reconnecting — live values will resume automatically.
       </p>
     </div>
   );
@@ -677,6 +738,44 @@ function SectionSharing() {
   );
 }
 
+function SectionAudit() {
+  return (
+    <div>
+      <p class="help-lead">
+        When the server is configured with <code>[audit] enabled = true</code>, every
+        <strong> system-affecting action</strong> is appended to an append-only log so it can be
+        reviewed later. Permitted users open it with the <strong>🛡 Audit</strong> button in the
+        view-mode toolbar.
+      </p>
+
+      <h3 class="help-h3">What gets recorded</h3>
+      <ul class="help-list">
+        <li><strong>Signal writes</strong> — both user-initiated (set-value widgets, buttons, panel
+          logic) and automated writes from the control-logic engine.</li>
+        <li><strong>Interface changes</strong> — panels created, updated, or deleted.</li>
+        <li><strong>Control-logic changes</strong> — graphs created, updated, or deleted.</li>
+      </ul>
+      <p>Each entry records the time, the actor (username, or the graph name for automated
+        actions), the action, the affected data source / signal and value, the client address, and
+        whether it succeeded.</p>
+
+      <h3 class="help-h3">Viewing the log</h3>
+      <ul class="help-list">
+        <li>The viewer lists the most recent events first.</li>
+        <li>Filter by user, action, signal, or a start/end time range.</li>
+        <li>System (automated) actions are tagged distinctly from user actions.</li>
+      </ul>
+
+      <p class="help-callout">
+        Access to the audit log is gated by an allowlist (<code>audit.readers</code> in the config),
+        following the same model as logic editing: an empty list means every user may view it,
+        otherwise only the listed users or groups can. The 🛡 Audit button is hidden for users who
+        are not permitted.
+      </p>
+    </div>
+  );
+}
+
 function SectionWidgets() {
   return (
     <div>
@@ -858,8 +957,9 @@ function SectionShortcuts() {
   );
 }
 
-const SECTION_COMPONENTS: Record<string, () => JSX.Element> = {
+const SECTION_COMPONENTS: Record<string, (props: { onNavigate: (section: string) => void }) => JSX.Element> = {
   start:     SectionStart,
+  tips:      SectionTips,
   view:      SectionView,
   edit:      SectionEdit,
   widgets:   SectionWidgets,
@@ -868,6 +968,7 @@ const SECTION_COMPONENTS: Record<string, () => JSX.Element> = {
   logic:     SectionLogic,
   control:   SectionControl,
   sharing:   SectionSharing,
+  audit:     SectionAudit,
   history:   SectionHistory,
   shortcuts: SectionShortcuts,
 };
@@ -877,7 +978,8 @@ const SECTION_COMPONENTS: Record<string, () => JSX.Element> = {
 export default function HelpModal({ initialSection = 'start', onClose }: Props) {
   const [active, setActive] = useState(initialSection);
 
-  const Content = SECTION_COMPONENTS[active] ?? SectionStart;
+  const Content: (props: { onNavigate: (section: string) => void }) => JSX.Element =
+    SECTION_COMPONENTS[active] ?? SectionStart;
 
   // Close on backdrop click
   function handleBackdrop(e: MouseEvent) {
@@ -915,7 +1017,7 @@ export default function HelpModal({ initialSection = 'start', onClose }: Props)
           {/* Content area */}
           <div class="help-content">
             <h2 class="help-h2">{SECTIONS.find(s => s.id === active)?.label}</h2>
-            <Content />
+            <Content onNavigate={setActive} />
           </div>
         </div>
       </div>

web/src/LogicEditor.tsx

@@ -1,6 +1,6 @@
 import { h, Fragment } from 'preact';
 import { useState, useEffect, useRef } from 'preact/hooks';
-import SearchableSelect from './SearchableSelect';
+import SignalPicker, { SignalOption } from './SignalPicker';
 import { checkExpr } from './lib/expr';
 import type { LogicGraph, LogicNode, LogicNodeKind, LogicWire, StateVar, Widget } from './lib/types';
 
@@ -37,6 +37,11 @@ const NODE_W = 11.5 * REM;  // node width
 const PORT_TOP = 2 * REM;   // y of the first port row, relative to node top
 const PORT_GAP = 1.375 * REM; // vertical spacing between stacked output ports
 const PORT_R = 0.375 * REM; // port radius (half the 0.75rem dot)
+// Ports sit inside the node's padding box, offset from the node border-box origin
+// by the node borders (3px colored top accent, 1px sides). Anchors add the same
+// offsets so wires meet the port centers, not their top edges.
+const BORDER = 1;
+const BORDER_TOP = 3;
 
 interface PaletteEntry {
   kind: LogicNodeKind;
@@ -65,6 +70,11 @@ const PALETTE: PaletteEntry[] = [
   { kind: 'action.dialog.info',     label: 'Info dialog',      params: { title: 'Info', message: '' } },
   { kind: 'action.dialog.error',    label: 'Error dialog',     params: { title: 'Error', message: '' } },
   { kind: 'action.dialog.setpoint', label: 'Set-point dialog', params: { title: 'Set value', message: '', fields: '[{"type":"input","label":"","target":"","default":""}]' } },
+  { kind: 'action.config.apply', label: 'Apply config', params: { instance: '', instanceSource: 'fixed', instanceVar: '' } },
+  { kind: 'action.config.read',  label: 'Read config',  params: { instance: '', instanceSource: 'fixed', instanceVar: '', key: '', target: '' } },
+  { kind: 'action.config.write', label: 'Write config', params: { instance: '', instanceSource: 'fixed', instanceVar: '', key: '', expr: '' } },
+  { kind: 'action.config.create', label: 'Create config', params: { set: '', name: 'auto', from: '', target: '' } },
+  { kind: 'action.config.snapshot', label: 'Snapshot config', params: { set: '', name: '', target: '' } },
 ];
 
 const KIND_LABEL: Record<LogicNodeKind, string> = {
@@ -88,6 +98,11 @@ const KIND_LABEL: Record<LogicNodeKind, string> = {
   'action.dialog.info': 'Info dialog',
   'action.dialog.error': 'Error dialog',
   'action.dialog.setpoint': 'Set-point dialog',
+  'action.config.apply': 'Apply config',
+  'action.config.read': 'Read config',
+  'action.config.write': 'Write config',
+  'action.config.create': 'Create config',
+  'action.config.snapshot': 'Snapshot config',
 };
 
 const THRESHOLD_OPS = ['>', '<', '>=', '<=', '==', '!='] as const;
@@ -114,11 +129,11 @@ function nodeHeight(kind: LogicNodeKind): number {
 function genId(): string { return 'n_' + Math.random().toString(36).slice(2, 9); }
 
 // Port anchors in canvas coordinates.
-function inAnchor(n: LogicNode) { return { x: n.x, y: n.y + PORT_TOP }; }
+function inAnchor(n: LogicNode) { return { x: n.x + BORDER, y: n.y + BORDER_TOP + PORT_TOP }; }
 function outAnchor(n: LogicNode, port: string) {
   const ports = outputs(n.kind);
   const i = Math.max(0, ports.findIndex(p => p.id === port));
-  return { x: n.x + NODE_W, y: n.y + PORT_TOP + i * PORT_GAP };
+  return { x: n.x + NODE_W - BORDER, y: n.y + BORDER_TOP + PORT_TOP + i * PORT_GAP };
 }
 
 function wirePathStr(x1: number, y1: number, x2: number, y2: number): string {
@@ -135,6 +150,8 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
 
   const [dataSources, setDataSources] = useState<string[]>([]);
   const [dsSignals, setDsSignals] = useState<Record<string, string[]>>({});
+  const [configInstances, setConfigInstances] = useState<{ id: string; name: string }[]>([]);
+  const [configSets, setConfigSets] = useState<{ id: string; name: string }[]>([]);
 
   const canvasRef = useRef<HTMLDivElement>(null);
   const dragNode = useRef<{ id: string; dx: number; dy: number; pushed: boolean } | null>(null);
@@ -160,6 +177,14 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
       .then(r => r.ok ? r.json() : [])
       .then((ds: DataSource[]) => setDataSources(ds.map(d => d.name)))
       .catch(() => {});
+    fetch('/api/v1/config/instances')
+      .then(r => r.ok ? r.json() : [])
+      .then((list: { id: string; name: string }[]) => setConfigInstances(list ?? []))
+      .catch(() => {});
+    fetch('/api/v1/config/sets')
+      .then(r => r.ok ? r.json() : [])
+      .then((list: { id: string; name: string }[]) => setConfigSets(list ?? []))
+      .catch(() => {});
   }, []);
 
   async function loadSignals(ds: string) {
@@ -180,6 +205,54 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
     return dsSignals[ds] ?? [];
   }
 
+  // Flatten every known ds:name into a single list for the fuzzy SignalPicker,
+  // and a hook to lazily load all data sources' signals when a picker opens.
+  function allSignalOptions(): SignalOption[] {
+    const out: SignalOption[] = [];
+    for (const ds of dsOptions) for (const name of signalOptions(ds)) out.push({ ds, name });
+    return out;
+  }
+  function openAllSignals() { dsOptions.forEach(ds => loadSignals(ds)); }
+
+  // The config-instance selector shared by the apply/read/write nodes. The
+  // instance can be fixed (chosen here at design time) or read at run time from
+  // a panel variable (instanceSource='var') — this is how a config-selector
+  // widget feeds these nodes the operator's current choice.
+  function instanceField(node: LogicNode) {
+    const src = node.params.instanceSource ?? 'fixed';
+    return (
+      <Fragment>
+        <div class="wizard-field">
+          <label>Instance source</label>
+          <select class="prop-select" value={src}
+            onChange={(e) => patchParams(node.id, { instanceSource: (e.target as HTMLSelectElement).value })}>
+            <option value="fixed">Fixed instance</option>
+            <option value="var">From variable</option>
+          </select>
+        </div>
+        {src === 'var' ? (
+          <div class="wizard-field">
+            <label>Instance-id variable</label>
+            <SignalPicker value={node.params.instanceVar ?? ''} options={allSignalOptions()}
+              onOpen={openAllSignals} allowFreeform
+              onChange={(ref) => patchParams(node.id, { instanceVar: ref })} />
+            <p class="hint">Reads the instance id (a string) from this panel variable — e.g. the
+              output of a Config selector widget.</p>
+          </div>
+        ) : (
+          <div class="wizard-field">
+            <label>Config instance</label>
+            <select class="prop-select" value={node.params.instance ?? ''}
+              onChange={(e) => patchParams(node.id, { instance: (e.target as HTMLSelectElement).value })}>
+              <option value="">choose…</option>
+              {configInstances.map(ci => <option key={ci.id} value={ci.id}>{ci.name}</option>)}
+            </select>
+          </div>
+        )}
+      </Fragment>
+    );
+  }
+
   const selected = nodes.find(n => n.id === selectedNode) ?? null;
 
   useEffect(() => {
@@ -520,19 +593,13 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
             )}
 
             {(selected.kind === 'trigger.threshold' || selected.kind === 'trigger.change') && (() => {
-              const { ds, name } = splitRef(selected.params.signal ?? '');
               return (
                 <Fragment>
-                  <div class="wizard-field">
-                    <label>Data source</label>
-                    <SearchableSelect value={ds} options={dsOptions}
-                      onSelect={(newDs) => { loadSignals(newDs); patchParams(selected.id, { signal: `${newDs}:` }); }} />
-                  </div>
                   <div class="wizard-field">
                     <label>Signal</label>
-                    <SearchableSelect value={name} options={signalOptions(ds)}
+                    <SignalPicker value={selected.params.signal ?? ''} options={allSignalOptions()}
-                      onSelect={(sig) => patchParams(selected.id, { signal: `${ds}:${sig}` })}
+                      onOpen={openAllSignals}
-                      placeholder={ds ? 'Search signals…' : 'Select data source first'} />
+                      onChange={(ref) => patchParams(selected.id, { signal: ref })} />
                   </div>
                   {selected.kind === 'trigger.threshold' && (
                     <div class="wizard-field wizard-field-row">
@@ -573,7 +640,7 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
               <ExprField label="Condition" value={selected.params.cond ?? ''}
                 onChange={(v) => patchParams(selected.id, { cond: v })}
                 onInsert={(ds, sig) => insertRef(selected.id, 'cond', ds, sig)}
-                dsOptions={dsOptions} signalOptions={signalOptions} loadSignals={loadSignals}
+                allSignals={allSignalOptions()} onOpenSignals={openAllSignals}
                 hint="True → 'then' port, false → 'else' port. e.g. {stub:level} > 5 && temp < 100. {sys:time}=epoch seconds, {sys:dt}=seconds since the trigger last fired." />
             )}
 
@@ -597,36 +664,29 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
                   <ExprField label="While condition" value={selected.params.cond ?? ''}
                     onChange={(v) => patchParams(selected.id, { cond: v })}
                     onInsert={(ds, sig) => insertRef(selected.id, 'cond', ds, sig)}
-                    dsOptions={dsOptions} signalOptions={signalOptions} loadSignals={loadSignals}
+                    allSignals={allSignalOptions()} onOpenSignals={openAllSignals}
                     hint="Loops the 'body' port while true (capped). e.g. {stub:level} < 90" />
                 )}
                 <p class="hint">Runs the <b>body</b> port repeatedly, then continues on <b>done</b>.</p>
               </Fragment>
             )}
 
-            {selected.kind === 'action.write' && (() => {
+            {selected.kind === 'action.write' && (
-              const { ds, name } = splitRef(selected.params.target ?? '');
-              return (
               <Fragment>
                 <div class="wizard-field">
-                    <label>Target data source</label>
+                  <label>Target signal / variable</label>
-                    <SearchableSelect value={ds} options={dsOptions}
+                  <SignalPicker value={selected.params.target ?? ''} options={allSignalOptions()}
-                      onSelect={(newDs) => { loadSignals(newDs); patchParams(selected.id, { target: `${newDs}:` }); }} />
+                    onOpen={openAllSignals} allowFreeform
-                  </div>
+                    onChange={(ref) => patchParams(selected.id, { target: ref })} />
-                  <div class="wizard-field">
+                  <p class="hint">Pick a signal, or type <code>local:name</code> to write a panel-local variable.</p>
-                    <label>Target signal</label>
-                    <SearchableSelect value={name} options={signalOptions(ds)}
-                      onSelect={(sig) => patchParams(selected.id, { target: `${ds}:${sig}` })}
-                      placeholder={ds ? 'Search signals…' : 'Select data source first'} />
                 </div>
                 <ExprField label="Value (expression)" value={selected.params.expr ?? ''}
                   onChange={(v) => patchParams(selected.id, { expr: v })}
                   onInsert={(ds2, sig) => insertRef(selected.id, 'expr', ds2, sig)}
-                    dsOptions={dsOptions} signalOptions={signalOptions} loadSignals={loadSignals}
+                  allSignals={allSignalOptions()} onOpenSignals={openAllSignals}
                   hint="e.g. ({stub:a} - {stub:b}) / {sys:dt} for a rate — or a constant like 42. {sys:time}=epoch seconds, {sys:dt}=seconds since the trigger last fired." />
               </Fragment>
-              );
+            )}
-            })()}
 
             {selected.kind === 'action.delay' && (
               <div class="wizard-field">
@@ -636,6 +696,114 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
               </div>
             )}
 
+            {selected.kind === 'action.config.apply' && (
+              <Fragment>
+                {instanceField(selected)}
+                <p class="hint">Applies the instance's current values to every bound signal (like the
+                  Apply button in the config manager).</p>
+              </Fragment>
+            )}
+
+            {selected.kind === 'action.config.read' && (
+              <Fragment>
+                {instanceField(selected)}
+                <div class="wizard-field">
+                  <label>Parameter key</label>
+                  <input class="prop-input" value={selected.params.key ?? ''}
+                    placeholder="parameter key"
+                    onInput={(e) => patchParams(selected.id, { key: (e.target as HTMLInputElement).value })} />
+                </div>
+                <div class="wizard-field">
+                  <label>Target signal / variable</label>
+                  <SignalPicker value={selected.params.target ?? ''} options={allSignalOptions()}
+                    onOpen={openAllSignals} allowFreeform
+                    onChange={(ref) => patchParams(selected.id, { target: ref })} />
+                  <p class="hint">Reads the named parameter's value and writes it to this target
+                    (numeric values only).</p>
+                </div>
+              </Fragment>
+            )}
+
+            {selected.kind === 'action.config.write' && (
+              <Fragment>
+                {instanceField(selected)}
+                <div class="wizard-field">
+                  <label>Parameter key</label>
+                  <input class="prop-input" value={selected.params.key ?? ''}
+                    placeholder="parameter key"
+                    onInput={(e) => patchParams(selected.id, { key: (e.target as HTMLInputElement).value })} />
+                </div>
+                <ExprField label="Value (expression)" value={selected.params.expr ?? ''}
+                  onChange={(v) => patchParams(selected.id, { expr: v })}
+                  onInsert={(ds2, sig) => insertRef(selected.id, 'expr', ds2, sig)}
+                  allSignals={allSignalOptions()} onOpenSignals={openAllSignals}
+                  hint="Stores the value into the named parameter, creating a new instance revision (numeric values only)." />
+              </Fragment>
+            )}
+
+            {selected.kind === 'action.config.create' && (
+              <Fragment>
+                <div class="wizard-field">
+                  <label>Config set</label>
+                  <select class="prop-select" value={selected.params.set ?? ''}
+                    onChange={(e) => patchParams(selected.id, { set: (e.target as HTMLSelectElement).value })}>
+                    <option value="">choose…</option>
+                    {configSets.map(cs => <option key={cs.id} value={cs.id}>{cs.name}</option>)}
+                  </select>
+                </div>
+                <div class="wizard-field">
+                  <label>New instance name</label>
+                  <input class="prop-input" value={selected.params.name ?? ''}
+                    placeholder="auto"
+                    onInput={(e) => patchParams(selected.id, { name: (e.target as HTMLInputElement).value })} />
+                </div>
+                <div class="wizard-field">
+                  <label>Copy values from</label>
+                  <select class="prop-select" value={selected.params.from ?? ''}
+                    onChange={(e) => patchParams(selected.id, { from: (e.target as HTMLSelectElement).value })}>
+                    <option value="">defaults (empty)</option>
+                    {configInstances.map(ci => <option key={ci.id} value={ci.id}>{ci.name}</option>)}
+                  </select>
+                </div>
+                <div class="wizard-field">
+                  <label>Write new id to variable</label>
+                  <SignalPicker value={selected.params.target ?? ''} options={allSignalOptions()}
+                    onOpen={openAllSignals} allowFreeform
+                    onChange={(ref) => patchParams(selected.id, { target: ref })} />
+                  <p class="hint">Creates a new instance for the chosen set (optionally seeded from another
+                    instance) and writes its id to this panel variable, ready to feed apply/read/write
+                    nodes set to "From variable".</p>
+                </div>
+              </Fragment>
+            )}
+
+            {selected.kind === 'action.config.snapshot' && (
+              <Fragment>
+                <div class="wizard-field">
+                  <label>Config set</label>
+                  <select class="prop-select" value={selected.params.set ?? ''}
+                    onChange={(e) => patchParams(selected.id, { set: (e.target as HTMLSelectElement).value })}>
+                    <option value="">choose…</option>
+                    {configSets.map(cs => <option key={cs.id} value={cs.id}>{cs.name}</option>)}
+                  </select>
+                </div>
+                <div class="wizard-field">
+                  <label>New instance name</label>
+                  <input class="prop-input" value={selected.params.name ?? ''}
+                    placeholder="(auto)"
+                    onInput={(e) => patchParams(selected.id, { name: (e.target as HTMLInputElement).value })} />
+                </div>
+                <div class="wizard-field">
+                  <label>Write new id to variable</label>
+                  <SignalPicker value={selected.params.target ?? ''} options={allSignalOptions()}
+                    onOpen={openAllSignals} allowFreeform
+                    onChange={(ref) => patchParams(selected.id, { target: ref })} />
+                  <p class="hint">Reads the current live value of every target signal of the set and stores
+                    them as a new instance, then writes the new instance id to this panel variable.</p>
+                </div>
+              </Fragment>
+            )}
+
             {selected.kind === 'action.accumulate' && (
               <Fragment>
                 <div class="wizard-field">
@@ -647,7 +815,7 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
                 <ExprField label="Value (expression)" value={selected.params.expr ?? ''}
                   onChange={(v) => patchParams(selected.id, { expr: v })}
                   onInsert={(ds2, sig) => insertRef(selected.id, 'expr', ds2, sig)}
-                  dsOptions={dsOptions} signalOptions={signalOptions} loadSignals={loadSignals}
+                  allSignals={allSignalOptions()} onOpenSignals={openAllSignals}
                   hint="Appends this value (with a timestamp) to the array. e.g. {stub:level}, or {sys:time} for the clock." />
               </Fragment>
             )}
@@ -683,7 +851,7 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
                 <ExprField label="Value (expression)" value={selected.params.expr ?? ''}
                   onChange={(v) => patchParams(selected.id, { expr: v })}
                   onInsert={(ds2, sig) => insertRef(selected.id, 'expr', ds2, sig)}
-                  dsOptions={dsOptions} signalOptions={signalOptions} loadSignals={loadSignals}
+                  allSignals={allSignalOptions()} onOpenSignals={openAllSignals}
                   hint="Logs this value to the browser console — handy for debugging a flow." />
               </Fragment>
             )}
@@ -747,7 +915,7 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
                 <DialogFieldsEditor allowInput={false}
                   fields={parseDialogFields(selected)}
                   onChange={(f) => patchParams(selected.id, { fields: JSON.stringify(f) })}
-                  dsOptions={dsOptions} signalOptions={signalOptions} loadSignals={loadSignals} />
+                  allSignals={allSignalOptions()} onOpenSignals={openAllSignals} />
               </Fragment>
             )}
 
@@ -768,7 +936,7 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
                 <DialogFieldsEditor allowInput={true}
                   fields={parseDialogFields(selected)}
                   onChange={(f) => patchParams(selected.id, { fields: JSON.stringify(f) })}
-                  dsOptions={dsOptions} signalOptions={signalOptions} loadSignals={loadSignals} />
+                  allSignals={allSignalOptions()} onOpenSignals={openAllSignals} />
                 <p class="hint">Each <b>input</b> prompts the operator and writes the entered number to its
                   target on OK; each <b>display</b> shows a live value. Cancel aborts the flow.</p>
               </Fragment>
@@ -796,17 +964,15 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
 }
 
 // Expression input with a signal-insert helper and live validation.
-function ExprField({ label, value, onChange, onInsert, dsOptions, signalOptions, loadSignals, hint }: {
+function ExprField({ label, value, onChange, onInsert, allSignals, onOpenSignals, hint }: {
   label: string;
   value: string;
   onChange: (v: string) => void;
   onInsert: (ds: string, sig: string) => void;
-  dsOptions: string[];
+  allSignals: SignalOption[];
-  signalOptions: (ds: string) => string[];
+  onOpenSignals: () => void;
-  loadSignals: (ds: string) => void;
   hint: string;
 }) {
-  const [insDs, setInsDs] = useState('');
   const err = checkExpr(value);
   return (
     <div class="wizard-field">
@@ -816,11 +982,9 @@ function ExprField({ label, value, onChange, onInsert, dsOptions, signalOptions,
         onInput={(e) => onChange((e.target as HTMLInputElement).value)} />
       {err && <p class="wizard-error">{err}</p>}
       <div class="flow-expr-insert">
-        <SearchableSelect value={insDs} options={dsOptions}
+        <SignalPicker value="" options={allSignals} onOpen={onOpenSignals}
-          onSelect={(ds) => { setInsDs(ds); loadSignals(ds); }} placeholder="ds…" />
+          placeholder="+ insert signal"
-        <SearchableSelect value="" options={signalOptions(insDs)}
+          onChange={(ref) => { const s = splitRef(ref); onInsert(s.ds, s.name); }} />
-          onSelect={(sig) => onInsert(insDs, sig)}
-          placeholder={insDs ? '+ insert signal' : 'pick ds first'} />
       </div>
       <p class="hint">{hint}</p>
     </div>
@@ -934,13 +1098,12 @@ function parseDialogFields(n: LogicNode): DialogFieldSpec[] {
   return [];
 }
 
-function DialogFieldsEditor({ allowInput, fields, onChange, dsOptions, signalOptions, loadSignals }: {
+function DialogFieldsEditor({ allowInput, fields, onChange, allSignals, onOpenSignals }: {
   allowInput: boolean;
   fields: DialogFieldSpec[];
   onChange: (fields: DialogFieldSpec[]) => void;
-  dsOptions: string[];
+  allSignals: SignalOption[];
-  signalOptions: (ds: string) => string[];
+  onOpenSignals: () => void;
-  loadSignals: (ds: string) => void;
 }) {
   function patch(i: number, patch: Partial<DialogFieldSpec>) {
     onChange(fields.map((f, j) => (j === i ? { ...f, ...patch } : f)));
@@ -953,7 +1116,6 @@ function DialogFieldsEditor({ allowInput, fields, onChange, dsOptions, signalOpt
       <label>{allowInput ? 'Fields' : 'Displayed values'}</label>
       {fields.length === 0 && <p class="hint">None yet.</p>}
       {fields.map((f, i) => {
-        const { ds, name } = splitRef(f.target ?? '');
         return (
           <div key={i} class="flow-field-edit">
             <div class="flow-field-head">
@@ -972,11 +1134,9 @@ function DialogFieldsEditor({ allowInput, fields, onChange, dsOptions, signalOpt
             {f.type === 'input' ? (
               <Fragment>
                 <div class="flow-row-edit">
-                  <SearchableSelect value={ds} options={dsOptions}
+                  <SignalPicker value={f.target ?? ''} options={allSignals}
-                    onSelect={(newDs) => { loadSignals(newDs); patch(i, { target: `${newDs}:` }); }} placeholder="ds…" />
+                    onOpen={onOpenSignals} allowFreeform placeholder="target signal…"
-                  <SearchableSelect value={name} options={signalOptions(ds)}
+                    onChange={(ref) => patch(i, { target: ref })} />
-                    onSelect={(sig) => patch(i, { target: `${ds}:${sig}` })}
-                    placeholder={ds ? 'signal…' : 'pick ds'} />
                 </div>
                 <input class={`prop-input${checkExpr(f.default ?? '') ? ' prop-input-error' : ''}`}
                   value={f.default ?? ''} placeholder="default value (expression, optional)"

web/src/PropertiesPane.tsx

@@ -55,6 +55,17 @@ const MULTI_SIGNAL_WIDGETS = new Set(['plot', 'multiled']);
 
 export default function PropertiesPane({ selected, multiCount, iface, onChange, onIfaceChange, width }: Props) {
   const [collapsed, setCollapsed] = useState(false);
+  const [configSets, setConfigSets] = useState<{ id: string; name: string }[]>([]);
+
+  // Config sets are only needed by the Config Selector widget; fetch lazily the
+  // first time one is selected.
+  useEffect(() => {
+    if (selected?.type !== 'configselect' || configSets.length > 0) return;
+    fetch('/api/v1/config/sets')
+      .then(r => r.ok ? r.json() : [])
+      .then((list: { id: string; name: string }[]) => setConfigSets(list ?? []))
+      .catch(() => {});
+  }, [selected?.type]);
 
   function setOpt(key: string, value: string) {
     if (!selected) return;
@@ -302,6 +313,7 @@ export default function PropertiesPane({ selected, multiCount, iface, onChange,
                       <option value="fft">FFT</option>
                       <option value="waterfall">Waterfall</option>
                       <option value="logic">Logic analyser</option>
+                      <option value="waveform">Waveform (array)</option>
                     </select>
                   </Field>
                   {(w.options['plotType'] ?? 'timeseries') === 'timeseries' && (
@@ -359,6 +371,39 @@ export default function PropertiesPane({ selected, multiCount, iface, onChange,
                   </Field>
                 </div>
               )}
+
+              {w.type === 'configselect' && (
+                <div>
+                  <Field label="Label">
+                    <TextInput value={w.options['label'] ?? 'Config'} onCommit={(v) => setOpt('label', v)} />
+                  </Field>
+                  <Field label="Config set">
+                    <select class="prop-select" value={w.options['set'] ?? ''}
+                      onChange={(e) => setOpt('set', (e.target as HTMLSelectElement).value)}>
+                      <option value="">choose…</option>
+                      {configSets.map(cs => <option key={cs.id} value={cs.id}>{cs.name}</option>)}
+                    </select>
+                  </Field>
+                  <Field label="Output variable">
+                    <div class="prop-field-col">
+                      <select class="prop-input" value={w.options['output'] ?? ''}
+                        onChange={(e) => setOpt('output', (e.target as HTMLSelectElement).value)}>
+                        <option value="">(none)</option>
+                        {(iface.statevars ?? []).map(v => (
+                          <option key={v.name} value={v.name}>{v.name}</option>
+                        ))}
+                      </select>
+                      <span class="prop-hint">A panel variable (define one of type "string" in the Variables tab); receives the selected instance id.</span>
+                    </div>
+                  </Field>
+                  <Field label="Instance subset">
+                    <div class="prop-field-col">
+                      <TextInput value={w.options['instances'] ?? ''} onCommit={(v) => setOpt('instances', v)} />
+                      <span class="prop-hint">Comma-separated instance ids to show. Empty = all instances of the set.</span>
+                    </div>
+                  </Field>
+                </div>
+              )}
             </div>
           )}
 

web/src/SignalPicker.tsx

@@ -0,0 +1,113 @@
+import { h } from 'preact';
+import { useState, useMemo } from 'preact/hooks';
+
+// A single fuzzy-finder input for picking a signal as one "ds:name" reference,
+// replacing the old stacked "Data source" + "Signal" select pair. The caller
+// supplies a flattened option list (every ds:name it knows about) and, via
+// onOpen, a hook to lazily load signals for all data sources when the dropdown
+// is first opened. When allowFreeform is set, typing a value that matches no
+// option (e.g. a new srv:/local: variable) can still be committed.
+
+export interface SignalOption { ds: string; name: string; }
+
+export default function SignalPicker({
+  value,
+  options,
+  onChange,
+  onOpen,
+  placeholder = 'Search signals…',
+  allowFreeform = false,
+}: {
+  value: string; // current "ds:name" (or "")
+  options: SignalOption[];
+  onChange: (ref: string) => void;
+  onOpen?: () => void;
+  placeholder?: string;
+  allowFreeform?: boolean;
+}) {
+  const [open, setOpen] = useState(false);
+  const [filter, setFilter] = useState('');
+
+  const filtered = useMemo(() => {
+    const tokens = filter.toLowerCase().split(/\s+/).filter(Boolean);
+    const scored = options
+      .map(o => ({ o, label: `${o.ds}:${o.name}` }))
+      .filter(({ label }) => {
+        const l = label.toLowerCase();
+        return tokens.every(t => l.includes(t));
+      });
+    // Prefer matches where the signal name (not the ds prefix) leads.
+    const f = filter.toLowerCase();
+    scored.sort((a, b) => {
+      const an = a.o.name.toLowerCase().startsWith(f) ? 0 : 1;
+      const bn = b.o.name.toLowerCase().startsWith(f) ? 0 : 1;
+      if (an !== bn) return an - bn;
+      return a.label.localeCompare(b.label);
+    });
+    return scored.slice(0, 200);
+  }, [options, filter]);
+
+  function openDropdown() {
+    setOpen(true);
+    setFilter('');
+    onOpen?.();
+  }
+
+  function commit(ref: string) {
+    onChange(ref);
+    setOpen(false);
+    setFilter('');
+  }
+
+  // A freeform entry is offered when the typed text looks like a usable
+  // reference and is not already an exact option.
+  const freeform = allowFreeform && filter.trim() !== ''
+    && !filtered.some(({ label }) => label === filter.trim());
+
+  return (
+    <div class="search-select">
+      <div class="search-select-trigger" onClick={() => (open ? setOpen(false) : openDropdown())}>
+        {value || <span class="search-select-placeholder">{placeholder}</span>}
+        <span class="search-select-arrow">{open ? '▴' : '▾'}</span>
+      </div>
+      {open && (
+        <div class="search-select-dropdown">
+          <input
+            class="prop-input"
+            autoFocus
+            placeholder="Type to search… (ds:name)"
+            value={filter}
+            onInput={(e) => setFilter((e.target as HTMLInputElement).value)}
+            onClick={(e) => e.stopPropagation()}
+            onKeyDown={(e: KeyboardEvent) => {
+              if (e.key === 'Enter') {
+                e.preventDefault();
+                if (filtered.length > 0) commit(`${filtered[0].o.ds}:${filtered[0].o.name}`);
+                else if (freeform) commit(filter.trim());
+              }
+              if (e.key === 'Escape') { e.preventDefault(); setOpen(false); }
+            }}
+          />
+          <div class="search-select-list">
+            {freeform && (
+              <div class="search-select-item" onClick={() => commit(filter.trim())}>
+                Use “{filter.trim()}”
+              </div>
+            )}
+            {filtered.length === 0 && !freeform && <div class="search-select-item hint">No matches</div>}
+            {filtered.map(({ o, label }) => (
+              <div
+                key={label}
+                class={`search-select-item${label === value ? ' search-select-item-selected' : ''}`}
+                onClick={() => commit(`${o.ds}:${o.name}`)}
+              >
+                {label}
+              </div>
+            ))}
+          </div>
+        </div>
+      )}
+      {open && <div class="search-select-backdrop" onClick={() => setOpen(false)} />}
+    </div>
+  );
+}

web/src/SignalTree.tsx

@@ -1,10 +1,10 @@
 import { h, Fragment } from 'preact';
 import { useState, useEffect, useRef, useMemo } from 'preact/hooks';
 import type { SignalRef, StateVar } from './lib/types';
-import SyntheticWizard from './SyntheticWizard';
 import SyntheticGraphEditor from './SyntheticGraphEditor';
 import GroupsTree from './GroupsTree';
 import ChannelFinderModal from './ChannelFinderModal';
+import SignalPicker from './SignalPicker';
 
 type TreeTab = 'sources' | 'groups';
 type GroupBy = 'datasource' | 'area' | 'system' | 'ioc';
@@ -491,10 +491,11 @@ export default function SignalTree({ onDragStart, width, panelId, statevars, onS
       )}
 
       {showWizard && (
-        <SyntheticWizard
+        <SyntheticGraphEditor
-          currentIfaceId={panelId}
+          create
+          panelId={panelId}
           onClose={() => setShowWizard(false)}
-          onCreated={loadAllSignals}
+          onSaved={loadAllSignals}
         />
       )}
 
@@ -523,24 +524,18 @@ export default function SignalTree({ onDragStart, width, panelId, statevars, onS
             </div>
             <div class="wizard-body">
               <div class="wizard-field">
-                <label>Data Source</label>
+                <label>Signal</label>
-                <select class="prop-select" value={manualDs} onChange={e => setManualDs((e.target as HTMLSelectElement).value)}>
+                <SignalPicker
-                  {Array.from(new Set(allSignals.map(s => s.ds))).map(ds => (
+                  value={manualName ? `${manualDs}:${manualName}` : ''}
-                    <option key={ds} value={ds}>{ds}</option>
+                  options={allSignals}
-                  ))}
+                  allowFreeform
-                  {!allSignals.some(s => s.ds === 'epics') && <option value="epics">epics</option>}
+                  placeholder="Search or type ds:NAME…"
-                </select>
+                  onChange={(ref) => {
-              </div>
+                    const i = ref.indexOf(':');
-              <div class="wizard-field">
+                    if (i < 0) { setManualDs(ref); setManualName(''); }
-                <label>Signal / PV Name</label>
+                    else { setManualDs(ref.slice(0, i)); setManualName(ref.slice(i + 1)); }
-                <input 
+                  }} />
-                  class="prop-input" 
+                <p class="hint">Pick an existing signal, or type <code>epics:MY:PV:NAME</code> to add a new one.</p>
-                  autoFocus
-                  placeholder="e.g. MY:PV:NAME" 
-                  value={manualName}
-                  onInput={e => setManualName((e.target as HTMLInputElement).value)}
-                  onKeyDown={e => e.key === 'Enter' && handleManualAdd()}
-                />
               </div>
             </div>
             <div class="wizard-footer">

web/src/SyntheticWizard.tsx

@@ -1,279 +0,0 @@
-import { h } from 'preact';
-import { useState, useEffect } from 'preact/hooks';
-import LuaEditor from './LuaEditor';
-import SearchableSelect from './SearchableSelect';
-import type { InputRef, SignalDef } from './lib/types';
-
-interface Props {
-  onClose: () => void;
-  onCreated: () => void;
-  // Interface id the wizard was opened from — used to bind panel-scoped signals.
-  currentIfaceId?: string;
-}
-
-interface NodeParam {
-  label: string;
-  key: string;
-  type: 'number' | 'text' | 'lua';
-  default: string;
-}
-
-const NODE_TYPES: Array<{ type: string; label: string; params: NodeParam[] }> = [
-  { type: 'gain',           label: 'Gain',            params: [{ label: 'Factor',           key: 'gain',   type: 'number', default: '1' }] },
-  { type: 'offset',         label: 'Offset',          params: [{ label: 'Offset',           key: 'offset', type: 'number', default: '0' }] },
-  { type: 'moving_average', label: 'Moving Average',  params: [{ label: 'Window (n)',       key: 'window', type: 'number', default: '10' }] },
-  { type: 'rms',            label: 'RMS',             params: [{ label: 'Window (n)',       key: 'window', type: 'number', default: '10' }] },
-  { type: 'lowpass',        label: 'Low-pass Filter', params: [
-    { label: 'Cutoff freq (Hz)', key: 'freq',  type: 'number', default: '1' },
-    { label: 'Order (1–8)',      key: 'order', type: 'number', default: '1' },
-  ]},
-  { type: 'derivative',     label: 'Derivative',      params: [] },
-  { type: 'integrate',      label: 'Integrate',       params: [] },
-  { type: 'clamp',          label: 'Clamp',           params: [{ label: 'Min', key: 'min', type: 'number', default: '0' }, { label: 'Max', key: 'max', type: 'number', default: '100' }] },
-  { type: 'expr',           label: 'Formula',         params: [{ label: 'Expression (a,b,c,d = inputs)', key: 'expr',   type: 'text', default: 'a * 1.0' }] },
-  { type: 'lua',            label: 'Lua Script',      params: [{ label: 'Script (a,b,c,d = inputs)',      key: 'script', type: 'lua',  default: 'return a' }] },
-];
-
-interface DataSource {
-  name: string;
-}
-
-interface SignalInfo {
-  name: string;
-  description?: string;
-}
-
-// ── Main Wizard ──────────────────────────────────────────────────────────────
-
-export default function SyntheticWizard({ onClose, onCreated, currentIfaceId }: Props) {
-  const [name, setName] = useState('');
-  const [inputs, setInputs] = useState<InputRef[]>([{ ds: 'stub', signal: 'sine_1hz' }]);
-  const [nodeType, setNodeType] = useState('gain');
-  const [params, setParams] = useState<Record<string, string>>({});
-  // Visibility scope. Panel scope requires an interface to bind to, so when the
-  // wizard is opened outside a saved panel it falls back to 'user'.
-  const [visibility, setVisibility] = useState<'panel' | 'user' | 'global'>(currentIfaceId ? 'panel' : 'user');
-  const [unit, setUnit] = useState('');
-  const [desc, setDesc] = useState('');
-  const [dispLow, setDispLow] = useState('0');
-  const [dispHigh, setDispHigh] = useState('100');
-  const [saving, setSaving] = useState(false);
-  const [error, setError] = useState('');
-
-  // Loaded data
-  const [dataSources, setDataSources] = useState<string[]>([]);
-  const [dsSignals, setDsSignals] = useState<Record<string, string[]>>({});
-
-  useEffect(() => {
-    fetch('/api/v1/datasources')
-      .then(r => r.ok ? r.json() : [])
-      .then((ds: DataSource[]) => setDataSources(ds.map(d => d.name)))
-      .catch(() => {});
-  }, []);
-
-  async function loadSignals(ds: string) {
-    if (dsSignals[ds]) return;
-    try {
-      const res = await fetch(`/api/v1/signals?ds=${encodeURIComponent(ds)}`);
-      if (!res.ok) return;
-      const sigs: SignalInfo[] = await res.json();
-      setDsSignals(prev => ({ ...prev, [ds]: sigs.map(s => s.name) }));
-    } catch {}
-  }
-
-  const nodeDef = NODE_TYPES.find(n => n.type === nodeType)!;
-
-  function getParam(key: string, def: string): string {
-    return params[key] ?? def;
-  }
-
-  function setParam(key: string, val: string) {
-    setParams(p => ({ ...p, [key]: val }));
-  }
-
-  function updateInput(idx: number, patch: Partial<InputRef>) {
-    setInputs(prev => prev.map((inp, i) => {
-      if (i !== idx) return inp;
-      const next = { ...inp, ...patch };
-      if (patch.ds) {
-        next.signal = '';
-        loadSignals(patch.ds);
-      }
-      return next;
-    }));
-  }
-
-  function addInput() {
-    setInputs(prev => [...prev, { ds: dataSources[0] || '', signal: '' }]);
-  }
-
-  function removeInput(idx: number) {
-    setInputs(prev => prev.filter((_, i) => i !== idx));
-  }
-
-  async function handleCreate() {
-    if (!name.trim()) { setError('Name is required'); return; }
-    if (inputs.some(i => !i.ds || !i.signal)) { setError('All inputs must have a data source and signal'); return; }
-
-    const nodeParams: Record<string, any> = {};
-    for (const p of nodeDef.params) {
-      const raw = getParam(p.key, p.default);
-      nodeParams[p.key] = p.type === 'number' ? parseFloat(raw) : raw;
-    }
-
-    const def: SignalDef = {
-      name: name.trim(),
-      inputs,
-      pipeline: [{ type: nodeType, params: nodeParams }],
-      meta: {
-        unit: unit || undefined,
-        description: desc || undefined,
-        displayLow: parseFloat(dispLow) || 0,
-        displayHigh: parseFloat(dispHigh) || 100,
-      },
-      visibility,
-      ...(visibility === 'panel' && currentIfaceId ? { panel: currentIfaceId } : {}),
-    };
-
-    setSaving(true);
-    setError('');
-    try {
-      const res = await fetch('/api/v1/synthetic', {
-        method: 'POST',
-        headers: { 'Content-Type': 'application/json' },
-        body: JSON.stringify(def),
-      });
-      if (!res.ok) {
-        const j = await res.json().catch(() => ({ error: res.statusText }));
-        throw new Error(j.error ?? res.statusText);
-      }
-      onCreated();
-      onClose();
-    } catch (err) {
-      setError(err instanceof Error ? err.message : String(err));
-    } finally {
-      setSaving(false);
-    }
-  }
-
-  return (
-    <div class="wizard-backdrop" onClick={onClose}>
-      <div class="wizard" onClick={(e) => e.stopPropagation()}>
-        <div class="wizard-header">
-          <span>New Synthetic Signal</span>
-          <button class="icon-btn" onClick={onClose}>✕</button>
-        </div>
-
-        <div class="wizard-body">
-          {error && <p class="wizard-error">{error}</p>}
-
-          <div class="wizard-section-title">Signal identity</div>
-          <div class="wizard-field">
-            <label>Name</label>
-            <input class="prop-input" value={name}
-              placeholder="e.g. smoothed_pressure"
-              onInput={(e) => setName((e.target as HTMLInputElement).value)} />
-          </div>
-
-          <div class="wizard-field">
-            <label>Visibility</label>
-            <select class="prop-select" value={visibility}
-              onChange={(e) => setVisibility((e.target as HTMLSelectElement).value as any)}>
-              <option value="panel" disabled={!currentIfaceId}>
-                This panel only{currentIfaceId ? '' : ' (save panel first)'}
-              </option>
-              <option value="user">All my panels</option>
-              <option value="global">All panels (global)</option>
-            </select>
-          </div>
-
-          <div class="wizard-section-title">Input signals</div>
-          {inputs.map((inp, idx) => (
-            <div key={idx} class="wizard-field wizard-field-row" style="align-items: flex-end; gap: 0.5rem; margin-bottom: 0.5rem;">
-              <div class="wizard-field" style="flex:1;">
-                <label>Data source</label>
-                <SearchableSelect
-                  value={inp.ds}
-                  options={dataSources}
-                  onSelect={(ds) => updateInput(idx, { ds })}
-                />
-              </div>
-              <div class="wizard-field" style="flex:2;">
-                <label>Signal</label>
-                <SearchableSelect
-                  value={inp.signal}
-                  options={dsSignals[inp.ds] || []}
-                  onSelect={(signal) => updateInput(idx, { signal })}
-                  placeholder={inp.ds ? 'Search signals…' : 'Select data source first'}
-                />
-              </div>
-              <button
-                class="icon-btn"
-                style="margin-bottom: 0.25rem;"
-                title="Remove input"
-                onClick={() => removeInput(idx)}
-                disabled={inputs.length === 1}
-              >✕</button>
-            </div>
-          ))}
-          <button class="panel-btn" style="margin-top: 0.5rem;" onClick={addInput}>+ Add input</button>
-
-          <div class="wizard-section-title" style="margin-top: 1.5rem;">Processing</div>
-          <div class="wizard-field">
-            <label>Node type</label>
-            <select class="prop-select" value={nodeType}
-              onChange={(e) => { setNodeType((e.target as HTMLSelectElement).value); setParams({}); }}>
-              {NODE_TYPES.map(n => <option key={n.type} value={n.type}>{n.label}</option>)}
-            </select>
-          </div>
-          {nodeDef.params.map(p => (
-            <div key={p.key} class="wizard-field">
-              <label>{p.label}</label>
-              {p.type === 'lua' ? (
-                <LuaEditor
-                  value={getParam(p.key, p.default)}
-                  onChange={(v) => setParam(p.key, v)}
-                />
-              ) : (
-                <input class="prop-input" type={p.type === 'number' ? 'number' : 'text'}
-                  value={getParam(p.key, p.default)}
-                  onInput={(e) => setParam(p.key, (e.target as HTMLInputElement).value)} />
-              )}
-            </div>
-          ))}
-
-          <div class="wizard-section-title">Metadata (optional)</div>
-          <div class="wizard-field wizard-field-row">
-            <div class="wizard-field">
-              <label>Unit</label>
-              <input class="prop-input" value={unit} placeholder="m/s"
-                onInput={(e) => setUnit((e.target as HTMLInputElement).value)} />
-            </div>
-            <div class="wizard-field">
-              <label>Display low</label>
-              <input class="prop-input" type="number" value={dispLow}
-                onInput={(e) => setDispLow((e.target as HTMLInputElement).value)} />
-            </div>
-            <div class="wizard-field">
-              <label>Display high</label>
-              <input class="prop-input" type="number" value={dispHigh}
-                onInput={(e) => setDispHigh((e.target as HTMLInputElement).value)} />
-            </div>
-          </div>
-          <div class="wizard-field">
-            <label>Description</label>
-            <input class="prop-input" value={desc} placeholder="Optional description"
-              onInput={(e) => setDesc((e.target as HTMLInputElement).value)} />
-          </div>
-        </div>
-
-        <div class="wizard-footer">
-          <button class="toolbar-btn" onClick={onClose}>Cancel</button>
-          <button class="toolbar-btn toolbar-btn-primary" onClick={handleCreate} disabled={saving}>
-            {saving ? 'Creating…' : 'Create Signal'}
-          </button>
-        </div>
-      </div>
-    </div>
-  );
-}

web/src/VersionHistory.tsx

@@ -0,0 +1,227 @@
+import { h } from 'preact';
+import { useState, useEffect, useCallback } from 'preact/hooks';
+import { diffLines, diffStats, sideBySide, DiffRow } from './lib/linediff';
+
+// VersionMeta mirrors the Go VersionMeta returned by every versioned document
+// type (interfaces, synthetic, controllogic, config sets/instances).
+export interface VersionMeta {
+  version: number;
+  name: string;
+  tag?: string;
+  current: boolean;
+  savedAt: string;
+}
+
+function errMsg(e: unknown): string { return e instanceof Error ? e.message : String(e); }
+
+function fmtTime(iso: string): string {
+  const d = new Date(iso);
+  if (isNaN(d.getTime())) return iso;
+  const pad = (n: number) => String(n).padStart(2, '0');
+  return `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())} ${pad(d.getHours())}:${pad(d.getMinutes())}`;
+}
+
+async function fetchJSON<T = any>(url: string, opts?: RequestInit): Promise<T | null> {
+  const res = await fetch(url, opts);
+  if (!res.ok && res.status !== 204) {
+    let m = `HTTP ${res.status}`;
+    try { const e = await res.json(); if (e && e.error) m = e.error; } catch { /* ignore */ }
+    throw new Error(m);
+  }
+  if (res.status === 204) return null;
+  return res.json();
+}
+
+// fetchVersionText returns a revision's serialized content as text, pretty-
+// printing JSON so structural changes produce clean, stable line diffs (XML
+// panels are returned verbatim).
+async function fetchVersionText(base: string, v: number): Promise<string> {
+  const res = await fetch(`${base}/versions/${v}`);
+  if (!res.ok) throw new Error(`HTTP ${res.status}`);
+  const raw = await res.text();
+  try { return JSON.stringify(JSON.parse(raw), null, 2); } catch { return raw; }
+}
+
+// ── Version tree ──────────────────────────────────────────────────────────────
+
+export function VersionTree({ base, viewing, dirty, canWrite = true, onView, onForked, onPromoted, onCompare, onError, reloadKey }: {
+  base: string;                       // e.g. /api/v1/synthetic/<name>
+  viewing: number | null;             // version currently open in the editor (active)
+  dirty?: boolean;                    // unsaved edits → dashed connector at the top
+  canWrite?: boolean;                 // gate promote/fork affordances
+  onView: (version: number) => void;
+  onForked: (newId: string) => void;
+  onPromoted: (version: number) => void;
+  onCompare: (av: number, bv: number) => void;
+  onError: (m: string) => void;
+  reloadKey?: number;                 // bump to force a versions reload
+}) {
+  const [versions, setVersions] = useState<VersionMeta[]>([]);
+  const [a, setA] = useState<number | null>(null);
+  const [b, setB] = useState<number | null>(null);
+
+  const load = useCallback(async () => {
+    try {
+      const v = (await fetchJSON<VersionMeta[]>(`${base}/versions`)) ?? [];
+      setVersions(v);
+      if (v.length >= 2) { setA(v[1].version); setB(v[0].version); }
+      else if (v.length === 1) { setA(v[0].version); setB(v[0].version); }
+    } catch (e) { onError(`Versions failed: ${errMsg(e)}`); }
+  }, [base, onError]);
+
+  useEffect(() => { load(); }, [load, reloadKey]);
+
+  async function fork(version: number) {
+    try {
+      const obj = await fetchJSON<{ id: string }>(`${base}/versions/${version}/fork`, { method: 'POST' });
+      if (obj?.id) onForked(obj.id);
+    } catch (e) { onError(`Fork failed: ${errMsg(e)}`); }
+  }
+  async function promote(version: number) {
+    if (!confirm(`Promote v${version} to a new current version?`)) return;
+    try {
+      await fetchJSON(`${base}/versions/${version}/promote`, { method: 'POST' });
+      await load();
+      onPromoted(version);
+    } catch (e) { onError(`Promote failed: ${errMsg(e)}`); }
+  }
+
+  const activeVer = viewing ?? versions.find(v => v.current)?.version ?? null;
+
+  return (
+    <div class="ver-tree">
+      {dirty && (
+        <div class="ver-node ver-node-unsaved">
+          <div class="ver-rail">
+            <span class="ver-dot ver-dot-unsaved" />
+            <span class="ver-line ver-line-dashed" />
+          </div>
+          <div class="ver-body"><span class="ver-num">unsaved changes</span></div>
+        </div>
+      )}
+      {versions.length === 0 && <div class="hint ver-empty">No versions yet.</div>}
+      {versions.map((v, idx) => {
+        const active = v.version === activeVer;
+        const last = idx === versions.length - 1;
+        const cls = `ver-dot${v.current ? ' ver-dot-current' : ''}${active ? ' ver-dot-active' : ''}`;
+        return (
+          <div key={v.version} class={`ver-node${active ? ' ver-node-active' : ''}`}>
+            <div class="ver-rail">
+              <span class={cls} title={v.current ? 'Selected (executed) version' : ''} />
+              {!last && <span class="ver-line" />}
+            </div>
+            <div class="ver-body">
+              <button class="ver-num" title="View this version" onClick={() => onView(v.version)}>
+                v{v.version}
+                {v.current && <span class="ver-badge">current</span>}
+                {active && !v.current && <span class="ver-badge ver-badge-view">viewing</span>}
+              </button>
+              {v.tag && <span class="ver-tag hint" title={v.tag}>{v.tag}</span>}
+              <span class="ver-time hint">{fmtTime(v.savedAt)}</span>
+              <span class="ver-actions">
+                {activeVer !== null && v.version !== activeVer && (
+                  <button class="cl-mini-btn" title={`Diff against the viewed version (v${activeVer})`}
+                    onClick={() => onCompare(Math.min(activeVer, v.version), Math.max(activeVer, v.version))}>diff</button>
+                )}
+                {canWrite && <button class="cl-mini-btn" title="Fork into a new document" onClick={() => fork(v.version)}>fork</button>}
+                {canWrite && !v.current && <button class="cl-mini-btn" title="Promote to current" onClick={() => promote(v.version)}>promote</button>}
+              </span>
+            </div>
+          </div>
+        );
+      })}
+      {versions.length >= 2 && (
+        <div class="ver-compare">
+          <span class="hint">Compare</span>
+          <select class="prop-select" value={String(a ?? '')} onChange={(e) => setA(Number((e.target as HTMLSelectElement).value))}>
+            {versions.map(v => <option key={v.version} value={v.version}>v{v.version}</option>)}
+          </select>
+          <span>→</span>
+          <select class="prop-select" value={String(b ?? '')} onChange={(e) => setB(Number((e.target as HTMLSelectElement).value))}>
+            {versions.map(v => <option key={v.version} value={v.version}>v{v.version}</option>)}
+          </select>
+          <button class="panel-btn" disabled={a === null || b === null} onClick={() => onCompare(a!, b!)}>Diff</button>
+        </div>
+      )}
+    </div>
+  );
+}
+
+// ── Diff viewer ───────────────────────────────────────────────────────────────
+
+export function DiffViewer({ base, av, bv, title, onClose }: {
+  base: string;
+  av: number;
+  bv: number;
+  title: string;
+  onClose: () => void;
+}) {
+  const [rows, setRows] = useState<DiffRow[] | null>(null);
+  const [mode, setMode] = useState<'unified' | 'split'>('split');
+  const [error, setError] = useState<string | null>(null);
+
+  useEffect(() => {
+    let alive = true;
+    (async () => {
+      try {
+        const [left, right] = await Promise.all([fetchVersionText(base, av), fetchVersionText(base, bv)]);
+        if (alive) setRows(diffLines(left, right));
+      } catch (e) { if (alive) setError(errMsg(e)); }
+    })();
+    return () => { alive = false; };
+  }, [base, av, bv]);
+
+  const stats = rows ? diffStats(rows) : { added: 0, removed: 0 };
+
+  return (
+    <div class="cl-confirm-overlay" onMouseDown={(e) => { if (e.target === e.currentTarget) onClose(); }}>
+      <div class="cl-confirm ver-diff-modal">
+        <div class="ver-diff-head">
+          <span class="cl-confirm-title">Diff — {title}</span>
+          <span class="ver-diff-stats">
+            <span class="ver-diff-add">+{stats.added}</span> <span class="ver-diff-del">−{stats.removed}</span>
+          </span>
+          <span class="ver-diff-modes">
+            <button class={`panel-btn${mode === 'split' ? ' panel-btn-primary' : ''}`} onClick={() => setMode('split')}>Side by side</button>
+            <button class={`panel-btn${mode === 'unified' ? ' panel-btn-primary' : ''}`} onClick={() => setMode('unified')}>Unified</button>
+          </span>
+          <button class="panel-btn" onClick={onClose}>Close</button>
+        </div>
+        {error && <div class="cl-error">{error}</div>}
+        {!rows && !error && <div class="hint ver-diff-loading">Loading…</div>}
+        {rows && (mode === 'unified' ? <UnifiedDiff rows={rows} /> : <SplitDiff rows={rows} />)}
+      </div>
+    </div>
+  );
+}
+
+function UnifiedDiff({ rows }: { rows: DiffRow[] }) {
+  return (
+    <div class="ver-diff ver-diff-unified">
+      {rows.map((r, i) => (
+        <div key={i} class={`ver-diff-row ver-diff-${r.op}`}>
+          <span class="ver-diff-ln">{r.leftNo ?? ''}</span>
+          <span class="ver-diff-ln">{r.rightNo ?? ''}</span>
+          <span class="ver-diff-sign">{r.op === 'add' ? '+' : r.op === 'del' ? '−' : ' '}</span>
+          <span class="ver-diff-text">{r.text || '\u00a0'}</span>
+        </div>
+      ))}
+    </div>
+  );
+}
+
+function SplitDiff({ rows }: { rows: DiffRow[] }) {
+  const pairs = sideBySide(rows);
+  return (
+    <div class="ver-diff ver-diff-split">
+      {pairs.map((p, i) => (
+        <div key={i} class="ver-diff-splitrow">
+          <span class="ver-diff-ln">{p.left?.leftNo ?? ''}</span>
+          <span class={`ver-diff-cell ver-diff-${p.left ? p.left.op : 'empty'}`}>{p.left ? (p.left.text || '\u00a0') : ''}</span>
+          <span class="ver-diff-ln">{p.right?.rightNo ?? ''}</span>
+          <span class={`ver-diff-cell ver-diff-${p.right ? p.right.op : 'empty'}`}>{p.right ? (p.right.text || '\u00a0') : ''}</span>
+        </div>
+      ))}
+    </div>
+  );
+}

web/src/ViewMode.tsx

@@ -7,10 +7,11 @@ import { parseInterface } from './lib/xml';
 import { newPlotPanel } from './lib/templates';
 import { useAuth, canWrite } from './lib/auth';
 import type { Interface } from './lib/types';
-import ContextualHelp from './ContextualHelp';
 import HelpModal from './HelpModal';
 import ZoomControl from './ZoomControl';
 import ControlLogicEditor from './ControlLogicEditor';
+import AuditViewer from './AuditViewer';
+import ConfigManager from './ConfigManager';
 
 interface Props {
   onEdit?: (iface?: Interface) => void;
@@ -33,6 +34,8 @@ export default function ViewMode({ onEdit, initialInterface, onView }: Props) {
   const [helpSection, setHelpSection] = useState('start');
   const [showTimeNav, setShowTimeNav] = useState(false);
   const [showControlLogic, setShowControlLogic] = useState(false);
+  const [showAudit, setShowAudit] = useState(false);
+  const [showConfig, setShowConfig] = useState(false);
   const [leftW, setLeftW] = useState(220);
   const [listCollapsed, setListCollapsed] = useState(false);
   const me = useAuth();
@@ -137,9 +140,13 @@ export default function ViewMode({ onEdit, initialInterface, onView }: Props) {
           )}
         </div>
         <div class="toolbar-right">
-          <div class={`status-chip ${wsStatus}`}>
+          <div
+            class={`status-chip ${wsStatus}`}
+            title={me.user ? `Signed in as ${me.user}${writable ? '' : ' (read-only)'}` : undefined}
+          >
             <span class="status-dot"></span>
             {wsStatus === 'connected' && me.user ? `connected as ${me.user}` : wsStatus}
+            {me.user && !writable && ' (read-only)'}
           </div>
           <button
             class={`toolbar-btn${showTimeNav ? ' toolbar-btn-active' : ''}`}
@@ -148,7 +155,6 @@ export default function ViewMode({ onEdit, initialInterface, onView }: Props) {
           >
             ⏱ History
           </button>
-          <ContextualHelp mode="view" onOpenManual={openHelp} />
           <button
             class="icon-btn help-manual-btn"
             onClick={() => openHelp('start')}
@@ -166,6 +172,24 @@ export default function ViewMode({ onEdit, initialInterface, onView }: Props) {
               ⚙ Control logic
             </button>
           )}
+          {me.canViewAudit && (
+            <button
+              class="toolbar-btn"
+              onClick={() => setShowAudit(true)}
+              title="View the audit log"
+            >
+              🛡 Audit
+            </button>
+          )}
+          {writable && (
+            <button
+              class="toolbar-btn"
+              onClick={() => setShowConfig(true)}
+              title="Open configuration manager"
+            >
+              🗂 Config
+            </button>
+          )}
           {writable && (
             <button
               class="btn-edit"
@@ -175,11 +199,6 @@ export default function ViewMode({ onEdit, initialInterface, onView }: Props) {
               Edit
             </button>
           )}
-          {me.user && (
-            <span class="user-chip" title={`Signed in as ${me.user}${writable ? '' : ' (read-only)'}`}>
-              {me.user}{!writable && ' (read-only)'}
-            </span>
-          )}
         </div>
       </header>
 
@@ -257,6 +276,13 @@ export default function ViewMode({ onEdit, initialInterface, onView }: Props) {
       {showControlLogic && (
         <ControlLogicEditor onClose={() => setShowControlLogic(false)} />
       )}
+
+      {showAudit && (
+        <AuditViewer onClose={() => setShowAudit(false)} />
+      )}
+      {showConfig && (
+        <ConfigManager onClose={() => setShowConfig(false)} />
+      )}
     </div>
   );
 }

web/src/lib/auth.ts

@@ -4,7 +4,7 @@ import type { Me, AccessLevel } from './types';
 
 // Default identity used before /api/v1/me resolves (or if it fails): assume a
 // trusted LAN user with full access, matching the backend default.
-export const DEFAULT_ME: Me = { user: '', level: 'write', groups: [], canEditLogic: true };
+export const DEFAULT_ME: Me = { user: '', level: 'write', groups: [], canEditLogic: true, canViewAudit: true };
 
 // AuthContext carries the resolved identity + global access level for the
 // current user throughout the app.
@@ -37,6 +37,7 @@ export async function fetchMe(): Promise<Me> {
       level: (data.level as AccessLevel) ?? 'write',
       groups: Array.isArray(data.groups) ? data.groups : [],
       canEditLogic: data.canEditLogic !== false,
+      canViewAudit: data.canViewAudit !== false,
     };
   } catch {
     return DEFAULT_ME;

web/src/lib/controldialogs.ts

@@ -0,0 +1,24 @@
+import { writable } from './store';
+
+// A dialog request pushed by a server-side control-logic action.dialog node and
+// delivered over the WebSocket. Unlike panel logic dialogs (lib/logic.ts) these
+// originate on the server and are addressed to the connected user by identity.
+export interface ControlDialog {
+  id: string;
+  kind: 'info' | 'error' | 'input';
+  title?: string;
+  message?: string;
+}
+
+// Active control-logic dialogs awaiting the user's acknowledgement / input.
+export const controlDialogs = writable<ControlDialog[]>([]);
+
+// pushControlDialog is invoked by the WS client on a "dialog" message.
+export function pushControlDialog(d: ControlDialog): void {
+  controlDialogs.update(list => (list.some(x => x.id === d.id) ? list : [...list, d]));
+}
+
+// dismissControlDialog removes a dialog once answered or cancelled.
+export function dismissControlDialog(id: string): void {
+  controlDialogs.update(list => list.filter(d => d.id !== id));
+}

web/src/lib/linediff.ts

@@ -0,0 +1,99 @@
+// Line-based diff (git style) used by the version history diff viewer. A simple
+// Longest-Common-Subsequence over lines yields a sequence of equal/added/removed
+// rows that can be rendered as a unified diff or split side-by-side.
+
+export type DiffOp = 'equal' | 'add' | 'del';
+
+export interface DiffRow {
+  op: DiffOp;
+  // Line content. For 'equal' both sides are identical (text).
+  text: string;
+  // 1-based line numbers in the left/right document; null when absent on a side.
+  leftNo: number | null;
+  rightNo: number | null;
+}
+
+function splitLines(s: string): string[] {
+  // Drop a single trailing newline so a file ending in "\n" doesn't yield a
+  // spurious empty final row.
+  const t = s.endsWith('\n') ? s.slice(0, -1) : s;
+  return t.length === 0 ? [] : t.split('\n');
+}
+
+// diffLines computes the LCS table and walks it back into ordered rows.
+export function diffLines(leftText: string, rightText: string): DiffRow[] {
+  const a = splitLines(leftText);
+  const b = splitLines(rightText);
+  const n = a.length;
+  const m = b.length;
+
+  // lcs[i][j] = length of LCS of a[i:] and b[j:].
+  const lcs: number[][] = Array.from({ length: n + 1 }, () => new Array(m + 1).fill(0));
+  for (let i = n - 1; i >= 0; i--) {
+    for (let j = m - 1; j >= 0; j--) {
+      lcs[i][j] = a[i] === b[j] ? lcs[i + 1][j + 1] + 1 : Math.max(lcs[i + 1][j], lcs[i][j + 1]);
+    }
+  }
+
+  const rows: DiffRow[] = [];
+  let i = 0;
+  let j = 0;
+  let la = 1;
+  let lb = 1;
+  while (i < n && j < m) {
+    if (a[i] === b[j]) {
+      rows.push({ op: 'equal', text: a[i], leftNo: la++, rightNo: lb++ });
+      i++; j++;
+    } else if (lcs[i + 1][j] >= lcs[i][j + 1]) {
+      rows.push({ op: 'del', text: a[i], leftNo: la++, rightNo: null });
+      i++;
+    } else {
+      rows.push({ op: 'add', text: b[j], leftNo: null, rightNo: lb++ });
+      j++;
+    }
+  }
+  while (i < n) rows.push({ op: 'del', text: a[i++], leftNo: la++, rightNo: null });
+  while (j < m) rows.push({ op: 'add', text: b[j++], leftNo: null, rightNo: lb++ });
+  return rows;
+}
+
+export interface DiffStats { added: number; removed: number; }
+
+export function diffStats(rows: DiffRow[]): DiffStats {
+  let added = 0;
+  let removed = 0;
+  for (const r of rows) {
+    if (r.op === 'add') added++;
+    else if (r.op === 'del') removed++;
+  }
+  return { added, removed };
+}
+
+// sideBySide pairs rows into aligned [left, right] columns: a del with the next
+// add becomes one changed row; otherwise each row occupies one side.
+export interface SideRow {
+  left: DiffRow | null;
+  right: DiffRow | null;
+}
+
+export function sideBySide(rows: DiffRow[]): SideRow[] {
+  const out: SideRow[] = [];
+  for (let k = 0; k < rows.length; k++) {
+    const r = rows[k];
+    if (r.op === 'equal') {
+      out.push({ left: r, right: r });
+    } else if (r.op === 'del') {
+      // Pair consecutive del/add as a single changed line when possible.
+      const next = rows[k + 1];
+      if (next && next.op === 'add') {
+        out.push({ left: r, right: next });
+        k++;
+      } else {
+        out.push({ left: r, right: null });
+      }
+    } else {
+      out.push({ left: null, right: r });
+    }
+  }
+  return out;
+}

web/src/lib/logic.ts

@@ -75,6 +75,88 @@ function sleep(ms: number): Promise<void> {
   return new Promise((resolve) => setTimeout(resolve, ms));
 }
 
+// Reads a single parameter's value from a config instance, coercing it to a
+// number. Returns null if the instance/set/param is missing or non-numeric.
+async function readConfigParam(instanceId: string, key: string): Promise<number | null> {
+  try {
+    const ir = await fetch(`/api/v1/config/instances/${encodeURIComponent(instanceId)}`);
+    if (!ir.ok) return null;
+    const inst: { setId: string; setVersion?: number; values?: Record<string, any> } = await ir.json();
+    const sv = inst.setVersion && inst.setVersion > 0
+      ? `/api/v1/config/sets/${encodeURIComponent(inst.setId)}/versions/${inst.setVersion}`
+      : `/api/v1/config/sets/${encodeURIComponent(inst.setId)}`;
+    const sr = await fetch(sv);
+    if (!sr.ok) return null;
+    const set: { parameters?: Array<{ key: string; default?: any }> } = await sr.json();
+    const param = (set.parameters ?? []).find(p => p.key === key);
+    if (!param) return null;
+    const raw = inst.values?.[key] ?? param.default;
+    const n = toNum(raw);
+    return isNaN(n) ? null : n;
+  } catch {
+    return null;
+  }
+}
+
+// Write a single numeric value into a config instance's parameter, creating a
+// new revision server-side. Reads the current instance, overwrites values[key],
+// and PUTs it back. Silently no-ops on any transport/parse error.
+async function writeConfigParam(instanceId: string, key: string, val: number): Promise<void> {
+  try {
+    const ir = await fetch(`/api/v1/config/instances/${encodeURIComponent(instanceId)}`);
+    if (!ir.ok) return;
+    const inst: any = await ir.json();
+    inst.values = { ...(inst.values ?? {}), [key]: val };
+    await fetch(`/api/v1/config/instances/${encodeURIComponent(instanceId)}`, {
+      method: 'PUT',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(inst),
+    });
+  } catch {}
+}
+
+// Create a new config instance for `setId`, optionally seeding its values from
+// an existing instance `fromId`. Returns the new instance id, or '' on failure.
+async function createConfigInstance(setId: string, name: string, fromId: string): Promise<string> {
+  try {
+    let values: Record<string, any> = {};
+    if (fromId) {
+      const fr = await fetch(`/api/v1/config/instances/${encodeURIComponent(fromId)}`);
+      if (fr.ok) {
+        const src: any = await fr.json();
+        values = { ...(src.values ?? {}) };
+      }
+    }
+    const r = await fetch('/api/v1/config/instances', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ name, setId, values }),
+    });
+    if (!r.ok) return '';
+    const out: any = await r.json();
+    return String(out?.id ?? '');
+  } catch {
+    return '';
+  }
+}
+
+// Snapshot the current live values of every target signal of `setId` into a new
+// config instance (optional label). Returns the new instance id, or '' on failure.
+async function snapshotConfigSet(setId: string, name: string): Promise<string> {
+  try {
+    const r = await fetch(`/api/v1/config/sets/${encodeURIComponent(setId)}/snapshot`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ name }),
+    });
+    if (!r.ok) return '';
+    const out: any = await r.json();
+    return String(out?.instance?.id ?? '');
+  } catch {
+    return '';
+  }
+}
+
 function toNum(v: any): number {
   if (typeof v === 'number') return v;
   if (typeof v === 'boolean') return v ? 1 : 0;
@@ -158,6 +240,20 @@ class LogicEngine {
     return toNum(this.live.get(refKey(ds, name)));
   }
 
+  // Resolve the config-instance id a node operates on. With instanceSource
+  // 'var' the id is read (as a raw string) from a panel-local variable / signal
+  // — this is how a config-selector widget feeds the apply/read/write nodes.
+  // Otherwise the fixed `instance` param (an id chosen at design time) is used.
+  private resolveInstanceId(node: LogicNode): string {
+    if ((node.params.instanceSource ?? 'fixed') === 'var') {
+      const r = parseRef(node.params.instanceVar ?? '');
+      if (!r) return '';
+      const v = this.live.get(refKey(r.ds, r.name));
+      return v == null ? '' : String(v).trim();
+    }
+    return (node.params.instance ?? '').trim();
+  }
+
   /** Activate a panel's logic graph. Replaces any previously loaded graph. */
   load(graph: LogicGraph | undefined): void {
     this.clear();
@@ -266,6 +362,18 @@ class LogicEngine {
         case 'action.write':
         case 'action.accumulate':
         case 'action.log':      collectRefs(node.params.expr ?? '').forEach(want); break;
+        case 'action.config.apply':
+        case 'action.config.read':
+        case 'action.config.write': {
+          // Dynamic-instance nodes read their target instance id from a panel
+          // var; subscribe it so the live cache holds the selected id.
+          if ((node.params.instanceSource ?? 'fixed') === 'var') {
+            const r = parseRef(node.params.instanceVar ?? '');
+            if (r) want(r);
+          }
+          if (node.kind === 'action.config.write') collectRefs(node.params.expr ?? '').forEach(want);
+          break;
+        }
         case 'action.dialog.info':
         case 'action.dialog.error':
         case 'action.dialog.setpoint': {
@@ -390,6 +498,65 @@ class LogicEngine {
         return;
       }
 
+      case 'action.config.apply': {
+        const id = this.resolveInstanceId(node);
+        if (id) {
+          try {
+            await fetch(`/api/v1/config/instances/${encodeURIComponent(id)}/apply`, { method: 'POST' });
+          } catch {}
+        }
+        await this.follow(node.id, 'out', ctx);
+        return;
+      }
+
+      case 'action.config.read': {
+        const id = this.resolveInstanceId(node);
+        const key = (node.params.key ?? '').trim();
+        const ref = parseRef(node.params.target ?? '');
+        if (id && key && ref) {
+          const val = await readConfigParam(id, key);
+          if (val !== null && !isNaN(val)) wsClient.write(ref, val);
+        }
+        await this.follow(node.id, 'out', ctx);
+        return;
+      }
+
+      case 'action.config.write': {
+        const id = this.resolveInstanceId(node);
+        const key = (node.params.key ?? '').trim();
+        const val = evalExpr(node.params.expr ?? '', ctx.resolve);
+        if (id && key && !isNaN(val)) {
+          await writeConfigParam(id, key, val);
+        }
+        await this.follow(node.id, 'out', ctx);
+        return;
+      }
+
+      case 'action.config.create': {
+        const setId = (node.params.set ?? '').trim();
+        const name = (node.params.name ?? '').trim() || 'auto';
+        const fromId = (node.params.from ?? '').trim();
+        const target = parseRef(node.params.target ?? '');
+        if (setId) {
+          const newId = await createConfigInstance(setId, name, fromId);
+          if (newId && target) wsClient.write(target, newId);
+        }
+        await this.follow(node.id, 'out', ctx);
+        return;
+      }
+
+      case 'action.config.snapshot': {
+        const setId = (node.params.set ?? '').trim();
+        const name = (node.params.name ?? '').trim();
+        const target = parseRef(node.params.target ?? '');
+        if (setId) {
+          const newId = await snapshotConfigSet(setId, name);
+          if (newId && target) wsClient.write(target, newId);
+        }
+        await this.follow(node.id, 'out', ctx);
+        return;
+      }
+
       case 'action.delay':
         await sleep(Math.max(0, parseInt(node.params.ms ?? '0', 10) || 0));
         await this.follow(node.id, 'out', ctx);

web/src/lib/synthTypes.ts

@@ -0,0 +1,86 @@
+// Static type propagation for the synthetic node-graph editor. This mirrors the
+// Go runtime/compile rules in internal/dsp/types.go (OpOutputType) so the editor
+// can colour wires by data type and flag type-incompatible wirings before save.
+// Keep the two in sync — a parity test guards the pair.
+
+import type { SynthGraph, SynthGraphNode } from './types';
+
+export type SynthType = 'scalar' | 'array' | 'unknown';
+
+// reductionOps collapse an array (or scalar) to a single scalar.
+const REDUCTION_OPS = new Set(['index', 'length', 'sum', 'mean', 'min', 'max']);
+// arrayProducerOps require an array input and yield an array.
+const ARRAY_PRODUCER_OPS = new Set(['fft', 'slice']);
+// scalarOnlyOps reject array inputs and yield a scalar (stateful filters + lua).
+const SCALAR_ONLY_OPS = new Set(['moving_average', 'rms', 'lowpass', 'derivative', 'integrate', 'lua']);
+
+// opOutputType reports an op's output type given its input types, plus an error
+// message when the inputs are definitely incompatible with the op. 'unknown'
+// inputs (a source whose real type isn't known yet) never trigger an error —
+// runtime typing is authoritative.
+export function opOutputType(op: string, inputs: SynthType[]): { type: SynthType; error?: string } {
+  if (REDUCTION_OPS.has(op)) return { type: 'scalar' };
+
+  if (ARRAY_PRODUCER_OPS.has(op)) {
+    if (inputs.some(t => t === 'scalar')) return { type: 'unknown', error: `${op} requires an array input` };
+    return { type: 'array' };
+  }
+
+  if (SCALAR_ONLY_OPS.has(op)) {
+    if (inputs.some(t => t === 'array')) return { type: 'unknown', error: `${op} does not accept an array input` };
+    return { type: 'scalar' };
+  }
+
+  // Elementwise stateless ops (gain, offset, add, subtract, multiply, divide,
+  // clamp, threshold, expr): array if any input is an array, scalar if all
+  // inputs are definitely scalar, otherwise unknown.
+  if (inputs.some(t => t === 'array')) return { type: 'array' };
+  if (inputs.some(t => t === 'unknown')) return { type: 'unknown' };
+  return { type: 'scalar' };
+}
+
+// inferNodeTypes walks the DAG in dependency order and assigns each node an
+// output type. Source node types come from `sourceType` (resolved from upstream
+// signal metadata); unresolved sources default to 'unknown'. `errors` collects
+// per-node type-conflict messages for the editor's validation.
+export function inferNodeTypes(
+  g: SynthGraph,
+  sourceType: (n: SynthGraphNode) => SynthType,
+): { types: Map<string, SynthType>; errors: Map<string, string> } {
+  const types = new Map<string, SynthType>();
+  const errors = new Map<string, string>();
+  const byId = new Map(g.nodes.map(n => [n.id, n]));
+
+  // Kahn topological order over node inputs.
+  const indeg = new Map<string, number>();
+  const succ = new Map<string, string[]>();
+  for (const n of g.nodes) indeg.set(n.id, 0);
+  for (const n of g.nodes) {
+    for (const from of n.inputs ?? []) {
+      if (!byId.has(from)) continue;
+      indeg.set(n.id, (indeg.get(n.id) ?? 0) + 1);
+      succ.set(from, [...(succ.get(from) ?? []), n.id]);
+    }
+  }
+  const queue = g.nodes.filter(n => (indeg.get(n.id) ?? 0) === 0).map(n => n.id);
+  while (queue.length) {
+    const id = queue.shift()!;
+    const n = byId.get(id)!;
+    if (n.kind === 'source') {
+      types.set(id, sourceType(n));
+    } else if (n.kind === 'output') {
+      const from = (n.inputs ?? [])[0];
+      types.set(id, (from && types.get(from)) || 'unknown');
+    } else {
+      const inTypes = (n.inputs ?? []).map(f => types.get(f) ?? 'unknown');
+      const { type, error } = opOutputType(n.op ?? '', inTypes);
+      types.set(id, type);
+      if (error) errors.set(id, error);
+    }
+    for (const s of succ.get(id) ?? []) {
+      indeg.set(s, (indeg.get(s) ?? 0) - 1);
+      if ((indeg.get(s) ?? 0) === 0) queue.push(s);
+    }
+  }
+  return { types, errors };
+}

web/src/lib/types.ts

@@ -9,6 +9,9 @@ export interface SignalValue {
   value: any;
   quality: 'good' | 'uncertain' | 'bad' | 'unknown';
   ts: string | null;
+  // Raw EPICS alarm fields (absent/0 = NO_ALARM). severity: 1=MINOR,2=MAJOR,3=INVALID.
+  severity?: number;
+  status?: number;
 }
 
 // Metadata for a signal (received once on subscribe)
@@ -149,7 +152,12 @@ export type LogicNodeKind =
   | 'action.widget'
   | 'action.dialog.info'
   | 'action.dialog.error'
-  | 'action.dialog.setpoint';
+  | 'action.dialog.setpoint'
+  | 'action.config.apply'
+  | 'action.config.read'
+  | 'action.config.write'
+  | 'action.config.create'
+  | 'action.config.snapshot';
 
 // A block on the flow canvas. `params` holds kind-specific fields as strings.
 export interface LogicNode {
@@ -209,6 +217,9 @@ export interface Me {
   // Whether the user may add/edit panel logic and server-side control logic.
   // False only when a logic-editors allowlist is configured and excludes them.
   canEditLogic: boolean;
+  // Whether the user may view the audit log. False only when an audit-readers
+  // allowlist is configured and excludes them, or auditing is disabled.
+  canViewAudit: boolean;
 }
 
 // Effective permission a user holds on a single panel or folder.
@@ -269,12 +280,33 @@ export interface PipelineNode {
   params: Record<string, any>;
 }
 
+// DAG form of a synthetic signal (mirrors backend synthetic.Graph). A node is a
+// source (ds:signal root), an op (DSP node with ordered `inputs`), or the single
+// output. When present it supersedes the legacy inputs+pipeline linear form.
+export type SynthNodeKind = 'source' | 'op' | 'output';
+export interface SynthGraphNode {
+  id: string;
+  kind: SynthNodeKind;
+  op?: string;
+  params?: Record<string, any>;
+  ds?: string;
+  signal?: string;
+  inputs?: string[]; // upstream node ids, in input order
+  x?: number;
+  y?: number;
+}
+export interface SynthGraph {
+  nodes: SynthGraphNode[];
+  output: string;
+}
+
 export interface SignalDef {
   name: string;
   ds?: string;      // legacy single input
   signal?: string;  // legacy single input
   inputs?: InputRef[];
-  pipeline: PipelineNode[];
+  pipeline?: PipelineNode[];
+  graph?: SynthGraph; // DAG form (preferred when present)
   meta: {
     unit?: string;
     description?: string;

web/src/lib/ws.ts

@@ -1,5 +1,6 @@
 import { writable, type Readable } from './store';
 import { writeLocalState } from './localstate';
+import { pushControlDialog } from './controldialogs';
 import type { SignalRef, SignalValue, SignalMeta, HistoryPoint } from './types';
 
 // ── Types ────────────────────────────────────────────────────────────────────
@@ -130,6 +131,8 @@ class WsClient {
           value: msg.value,
           quality: msg.quality ?? 'unknown',
           ts: msg.ts ?? null,
+          severity: msg.severity ?? 0,
+          status: msg.status ?? 0,
         };
         for (const s of subs) s.onUpdate(val);
         break;
@@ -161,6 +164,16 @@ class WsClient {
         }
         break;
       }
+      case 'dialog': {
+        // Server-side control logic requesting a user notification / input.
+        pushControlDialog({
+          id: String(msg.id),
+          kind: msg.kind === 'error' || msg.kind === 'input' ? msg.kind : 'info',
+          title: msg.title,
+          message: msg.message,
+        });
+        break;
+      }
       case 'error':
         // Resolve any pending history callbacks with empty data on error
         if (key && this.histCallbacks.has(key)) {
@@ -268,6 +281,14 @@ class WsClient {
     console.log('[ws] write', ref.ds, ref.name, value, 'ws state:', this.ws?.readyState);
     this._send({ type: 'write', ds: ref.ds, name: ref.name, value });
   }
+
+  /**
+   * Answer a control-logic input dialog. `value === null` cancels (dismisses)
+   * the dialog without writing its target server variable.
+   */
+  sendDialogResponse(id: string, value: number | null): void {
+    this._send({ type: 'dialogResponse', id, value });
+  }
 }
 
 // Singleton instance

web/src/widgets/ConfigSelect.tsx

@@ -0,0 +1,80 @@
+import { h } from 'preact';
+import { useState, useEffect } from 'preact/hooks';
+import { wsClient } from '../lib/ws';
+import { getSignalStore } from '../lib/stores';
+import type { Widget, SignalValue } from '../lib/types';
+
+interface InstanceMeta { id: string; name: string; setId?: string; }
+
+interface Props { widget: Widget; onContextMenu?: (e: MouseEvent) => void; }
+
+// A combo that lists the config instances of a chosen set and writes the
+// selected instance id (a string) to a panel-local variable. The output var can
+// then drive the apply/read/write config logic nodes (set to "From variable"),
+// letting an operator pick which configuration the flow operates on at run time.
+export default function ConfigSelect({ widget, onContextMenu }: Props) {
+  const setId = widget.options['set'] || '';
+  const output = widget.options['output'] || '';
+  const label = widget.options['label'] || 'Config';
+  // Optional comma-separated allow-list of instance ids; empty shows them all.
+  const subset = (widget.options['instances'] || '')
+    .split(',').map(s => s.trim()).filter(Boolean);
+
+  const [instances, setInstances] = useState<InstanceMeta[]>([]);
+  const [selected, setSelected] = useState('');
+
+  // Mirror the output var so external writers (e.g. a create-config node) keep
+  // the combo in sync.
+  useEffect(() => {
+    if (!output) return;
+    const unsub = getSignalStore({ ds: 'local', name: output }).subscribe((v: SignalValue) => {
+      const id = v.value == null ? '' : String(v.value);
+      setSelected(prev => (id && id !== prev ? id : prev));
+    });
+    return unsub;
+  }, [output]);
+
+  useEffect(() => {
+    let cancelled = false;
+    fetch('/api/v1/config/instances')
+      .then(r => r.ok ? r.json() : [])
+      .then((list: InstanceMeta[]) => {
+        if (cancelled) return;
+        let filtered = (list ?? []).filter(ci => !setId || ci.setId === setId);
+        if (subset.length > 0) filtered = filtered.filter(ci => subset.includes(ci.id));
+        setInstances(filtered);
+        // Default the output to the first instance when nothing is chosen yet.
+        setSelected(prev => {
+          if (prev && filtered.some(ci => ci.id === prev)) return prev;
+          const first = filtered[0]?.id ?? '';
+          if (first && output) wsClient.write({ ds: 'local', name: output }, first);
+          return first;
+        });
+      })
+      .catch(() => {});
+    return () => { cancelled = true; };
+  }, [setId, widget.options['instances']]);
+
+  function onChange(id: string) {
+    setSelected(id);
+    if (output) wsClient.write({ ds: 'local', name: output }, id);
+  }
+
+  return (
+    <div
+      class="configselect"
+      style={`left:${widget.x}px;top:${widget.y}px;width:${widget.w}px;height:${widget.h}px;`}
+      onContextMenu={onContextMenu}
+    >
+      <span class="cs-label">{label}:</span>
+      <select
+        class="cs-select"
+        value={selected}
+        onChange={(e: Event) => onChange((e.target as HTMLSelectElement).value)}
+      >
+        {instances.length === 0 && <option value="">no instances</option>}
+        {instances.map(ci => <option key={ci.id} value={ci.id}>{ci.name}</option>)}
+      </select>
+    </div>
+  );
+}

web/src/widgets/PlotWidget.tsx

@@ -84,12 +84,25 @@ export default function PlotWidget({ widget, onContextMenu, timeRange }: Props)
     const showLegend = legendPos !== 'none';
 
     const buffers: SeriesBuffer[] = signals.map(() => ({ timestamps: [], values: [] }));
+    // Latest waveform (array) value per signal — used only by plotType 'waveform'.
+    const waveforms: number[][] = signals.map(() => []);
     const unsubs: (() => void)[] = [];
     const fmt = widget.options['format'] ?? '';
 
     // ── uPlot (timeseries) ──────────────────────────────────────────────────
     let uplot: uPlot | null = null;
 
+    // Newest sample timestamp across all series (seconds). Anchoring the live
+    // x-axis to this — rather than wall-clock Date.now() — avoids client/server
+    // clock skew clipping the latest point, and keeps the right edge on real data.
+    function latestSampleTs(): number {
+      let m = -Infinity;
+      for (const b of buffers) {
+        if (b.timestamps.length) m = Math.max(m, b.timestamps[b.timestamps.length - 1]);
+      }
+      return isFinite(m) ? m : Date.now() / 1000;
+    }
+
     // windowSec: apply rolling window for live mode; 0 = use full buffer (historical)
     function uplotData(windowSec = 0): uPlot.AlignedData {
       if (signals.length === 0) return [[]];
@@ -165,7 +178,22 @@ export default function PlotWidget({ widget, onContextMenu, timeRange }: Props)
           { stroke: '#94a3b8', grid: { stroke: '#2d3748' }, ticks: { stroke: '#475569' } },
           yAxis,
         ],
-        scales: { x: { time: true }, y: { ...scaleY, range: scaleYRange } },
+        scales: {
+          x: {
+            time: true,
+            // Live mode with a finite window: pin the x-axis to a rolling
+            // [newest − window, newest] span so a single old/outlier sample
+            // can't stretch the axis and compress real points to the right.
+            // Historical mode (timeRange) keeps uPlot's data-driven auto-range.
+            ...(!timeRange && timeWindow > 0
+              ? { range: (): [number, number] => {
+                  const r = latestSampleTs();
+                  return [r - timeWindow, r];
+                } }
+              : {}),
+          },
+          y: { ...scaleY, range: scaleYRange },
+        },
       };
     }
 
@@ -243,6 +271,24 @@ export default function PlotWidget({ widget, onContextMenu, timeRange }: Props)
             }),
           };
         }
+        case 'waveform': {
+          // Latest waveform (array) sample per signal, drawn as an x-vs-index
+          // trace. Each update replaces the trace rather than appending.
+          return {
+            backgroundColor: ECHARTS_DARK.backgroundColor,
+            legend: legendOpt,
+            grid: { left: 60, right: 16, top: showLegend ? 28 : 12, bottom: 40 },
+            xAxis: { type: 'value', name: 'Index', nameLocation: 'middle', nameGap: 24, min: 0, axisLine, axisLabel, splitLine },
+            yAxis: { type: 'value', name: 'Value', axisLine, axisLabel, splitLine },
+            series: signals.map((s, i) => ({
+              name: s.name,
+              type: 'line',
+              data: (waveforms[i] ?? []).map((v, k) => [k, v]),
+              lineStyle: { color: s.color ?? COLORS[i % COLORS.length] },
+              showSymbol: false,
+            })),
+          };
+        }
         case 'logic': {
           // Logic-analyser style: each signal is a 0/1 step trace stacked on its
           // own lane, with a relative-time x-axis (seconds before now).
@@ -397,7 +443,16 @@ export default function PlotWidget({ widget, onContextMenu, timeRange }: Props)
         if (sv.value === null || sv.value === undefined || sv.ts === null) return;
         const ts = new Date(sv.ts).getTime() / 1000;
 
-        if (plotType === 'timeseries') {
+        if (plotType === 'waveform') {
+          // Array-valued sample: keep only the latest waveform and redraw.
+          if (Array.isArray(sv.value)) {
+            waveforms[i] = sv.value.map((x: any) => typeof x === 'number' ? x : parseFloat(String(x)));
+          } else {
+            const v = typeof sv.value === 'number' ? sv.value : parseFloat(String(sv.value));
+            waveforms[i] = isNaN(v) ? [] : [v];
+          }
+          if (echart) echart.setOption(echartsOption(), { notMerge: true });
+        } else if (plotType === 'timeseries') {
           const v = typeof sv.value === 'number' ? sv.value : parseFloat(String(sv.value));
           if (isNaN(v)) return;
           pushSample(buffers[i], ts, v);

workspace/data/acl.json

@@ -1,10 +1,31 @@
 {
-  "panels": {},
+  "panels": {
+    "epics_test": {
+      "owner": ""
+    },
+    "new-plot-panel": {
+      "owner": "",
+      "folder": "fld-c5396468072d4f69"
+    },
+    "test": {
+      "owner": "martino",
+      "order": 1
+    },
+    "test-1781729251317": {
+      "owner": "",
+      "order": 3
+    }
+  },
   "folders": {
     "fld-68b0bb9c23c9fd3b": {
       "id": "fld-68b0bb9c23c9fd3b",
       "name": "Test",
       "owner": ""
+    },
+    "fld-c5396468072d4f69": {
+      "id": "fld-c5396468072d4f69",
+      "name": "Plots",
+      "owner": "martino"
     }
   }
 }

workspace/data/configs/instances/new-instance.json

@@ -0,0 +1,13 @@
+{
+  "id": "new-instance",
+  "name": "New instance",
+  "owner": "martino",
+  "setId": "new-config-set",
+  "values": {
+    "param1": 1,
+    "param2": 1,
+    "param3": "Test",
+    "param4": "Idle"
+  },
+  "version": 3
+}

workspace/data/configs/instances/new-instance.v1.json

@@ -0,0 +1,8 @@
+{
+  "id": "new-instance",
+  "name": "New instance",
+  "owner": "martino",
+  "setId": "new-config-set",
+  "values": {},
+  "version": 1
+}

workspace/data/configs/instances/new-instance.v2.json

@@ -0,0 +1,12 @@
+{
+  "id": "new-instance",
+  "name": "New instance",
+  "owner": "martino",
+  "setId": "new-config-set",
+  "values": {
+    "param1": 1,
+    "param2": 1,
+    "param4": "Idle"
+  },
+  "version": 2
+}

workspace/data/configs/sets/new-config-set.json

@@ -0,0 +1,46 @@
+{
+  "id": "new-config-set",
+  "name": "New config set",
+  "owner": "martino",
+  "parameters": [
+    {
+      "ds": "epics",
+      "key": "param1",
+      "max": 1,
+      "min": 0,
+      "signal": "UOPI:INTERLOCK",
+      "type": "float64"
+    },
+    {
+      "ds": "epics",
+      "key": "param2",
+      "max": 100,
+      "min": 0,
+      "signal": "UOPI:FLOW",
+      "type": "float64",
+      "unit": "L/min"
+    },
+    {
+      "default": "CIAO",
+      "ds": "epics",
+      "key": "param3",
+      "signal": "UOPI:MESSAGE",
+      "subgroup": "Casa",
+      "type": "string"
+    },
+    {
+      "ds": "epics",
+      "enumValues": [
+        "Idle",
+        "Running",
+        "Fault",
+        "Maintenance"
+      ],
+      "key": "param4",
+      "signal": "UOPI:MODE",
+      "subgroup": "Casa",
+      "type": "enum"
+    }
+  ],
+  "version": 3
+}

workspace/data/configs/sets/new-config-set.v1.json

@@ -0,0 +1,7 @@
+{
+  "id": "new-config-set",
+  "name": "New config set",
+  "owner": "martino",
+  "parameters": [],
+  "version": 1
+}

workspace/data/configs/sets/new-config-set.v2.json

@@ -0,0 +1,25 @@
+{
+  "id": "new-config-set",
+  "name": "New config set",
+  "owner": "martino",
+  "parameters": [
+    {
+      "ds": "epics",
+      "key": "param1",
+      "max": 1,
+      "min": 0,
+      "signal": "UOPI:INTERLOCK",
+      "type": "float64"
+    },
+    {
+      "ds": "epics",
+      "key": "param2",
+      "max": 100,
+      "min": 0,
+      "signal": "UOPI:FLOW",
+      "type": "float64",
+      "unit": "L/min"
+    }
+  ],
+  "version": 2
+}