controllogic: make expr evaluator value-polymorphic (arrays, indexing, array funcs)

Rewrites internal/controllogic/expr.go to evaluate to Value (scalar float64
or []Value array): adds array literals [a,b], postfix indexing arr[i], and
array functions (len, sum, mean, push, pop, slice, concat, sort, …). Resolver
type changes from func(...) float64 to func(...) Value; EvalValue added;
EvalExpr/EvalBool retain scalar float64/bool returns. Three temporary shims
added in engine.go, lua.go, and expr_test.go pending Tasks 4 and 6.

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

TODO.md

@@ -98,6 +98,7 @@
     - [x] Implement live / debug mode where value are evaluated online and visualized at human speed (e.g. 0.5s) — editor spins up a second client-side `LogicEngine` in new `dryRun` mode (real writes/config/dialogs suppressed) loaded with the edited graph; per-node values polled into the shared badges; the view-mode singleton is untouched
     - add full suppor to local array values: dynamic, dynamic but capped max, fixed size etc:
       - array functions should work with new local array
+      - NOTE: **Phase 1 (panel logic, client-side TS) is DONE** — array statevars (dynamic/capped/fixed), value-polymorphic expression engine with indexing + array functions, `action.array.*` mutation nodes (legacy accumulate/export/clear unified + auto-migrated), panel-XML round-trip, editor declaration form, and widget array modes (plot/table/multi-LED). Box stays unchecked until **Phase 2** (server-side `internal/controllogic` Go port, see below) lands.
   - [ ] Control loop:
     - [x] Implement live / debug mode where value are evaluated online and visualized at human speed (e.g. 0.5s) — server pushes per-node events over the WS (`debugSubscribe`/`debugNode`) via a new `DebugObserver` on the engine (lock-free `atomic.Value`, gated by a per-graph watch set) + `internal/server/debughub.go` (drop-on-full fan-out). Two modes share one message shape: **Live** observes the running enabled graph; **Simulate** dry-runs the unsaved edits in a throwaway sandbox (`StartSimulate`, side effects suppressed). Live/Sim sub-toggle in the editor
     - add full support to server side array values

cmd/uopi/main.go

@@ -21,7 +21,9 @@ import (
 	"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/modbus"
 	"github.com/uopi/uopi/internal/datasource/pva"
+	"github.com/uopi/uopi/internal/datasource/scpi"
 	"github.com/uopi/uopi/internal/datasource/servervar"
 	"github.com/uopi/uopi/internal/datasource/stub"
 	"github.com/uopi/uopi/internal/datasource/synthetic"
@@ -146,6 +148,35 @@ func main() {
 		}
 	}
 
+	// Modbus TCP data source: polls configured holding/input/coil/discrete
+	// registers on one or more devices. Disabled unless [datasource.modbus] is
+	// configured with devices.
+	if cfg.Datasource.Modbus.Enabled {
+		mbDS, err := modbus.New(cfg.Datasource.Modbus)
+		if err != nil {
+			log.Error("modbus init", "err", err)
+		} else if err := mbDS.Connect(ctx); err != nil {
+			log.Error("modbus connect", "err", err)
+		} else {
+			brk.Register(mbDS)
+			context.AfterFunc(ctx, mbDS.Close)
+		}
+	}
+
+	// SCPI data source: polls instrument channels over raw TCP sockets.
+	// Disabled unless [datasource.scpi] is configured with instruments.
+	if cfg.Datasource.SCPI.Enabled {
+		scpiDS, err := scpi.New(cfg.Datasource.SCPI)
+		if err != nil {
+			log.Error("scpi init", "err", err)
+		} else if err := scpiDS.Connect(ctx); err != nil {
+			log.Error("scpi connect", "err", err)
+		} else {
+			brk.Register(scpiDS)
+			context.AfterFunc(ctx, scpiDS.Close)
+		}
+	}
+
 	// 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)

docs/TECHNICAL_SPEC.md

@@ -346,10 +346,40 @@ mount and `clear()` on unmount. The engine subscribes to every referenced signal
 cache, then on each trigger activation walks the wired graph (gates, if/loop, actions),
 evaluating expression fields via a small safe recursive-descent evaluator (no `eval`).
 Triggers include button/threshold/change/timer/loop and On-open/On-close lifecycle; actions
-include signal writes, delay, log, in-memory data arrays (accumulate/export-CSV/clear) and
+include signal writes, delay, log, array mutations (see below) and
 user dialogs (info/error/set-point). The engine runs entirely in the browser — no backend
 component.
 
+**Array-valued local variables.** Panel-local variables (`<statevar>`) may be declared with
+`type="array"`. An array statevar carries `elem` (`number`|`bool`|`array`, the element kind —
+`array` gives a 2-D array), `sizing`, and `capacity`. The three sizing policies
+(`web/src/lib/arraypolicy.ts`) are: **dynamic** (unbounded up to `ARRAY_MAX = 1_000_000`,
+oldest dropped past the cap), **capped** (length kept ≤ `capacity`, oldest dropped FIFO), and
+**fixed** (exactly `capacity` elements — truncated or zero-padded). Sizing is enforced only at
+store time (`writeLocalState` → `applySizing`); expressions themselves are pure and produce
+unbounded values. The value model is the tagged union `ArrVal = number | ArrVal[]` with
+booleans represented as `1`/`0` at the leaves.
+
+The expression evaluator (`web/src/lib/expr.ts`) is value-polymorphic: `evalValue` returns an
+`ArrVal`, while `evalExpr` returns a `number` (`NaN` if the result is an array). It supports
+array literals `[a, b, c]`, indexing `a[i]` (negative indices count from the end), and a table
+of array functions: `len`, `sum`, `mean`, `slice`, `concat`, `reverse`, `sort`, `scale`, `add`,
+`sub`, `push`, `set`, `insert`, `remove`, `pop`, `shift`, `indexOf`, `contains`, `fill` (plus
+`min`/`max`, which accept either scalars or an array). These are pure — they return new values
+and never mutate a stored variable.
+
+Array mutation nodes write back to a declared array statevar: `action.array.push`, `…set`,
+`…remove`, `…pop`, and `…clear`. The legacy `action.accumulate` and `action.clear` nodes are
+retained as aliases over `action.array.push` / `action.array.clear`, and legacy graphs are
+auto-migrated to declare their backing arrays on load (`ensureArrayDecls`). `action.export`
+now produces **index-aligned** CSV: each configured array becomes a column (custom per-column
+labels supported), rows aligned by element index. Array statevars and all array nodes
+round-trip through the panel XML (`<statevar type="array" elem=… sizing=… capacity=…>`).
+
+> **Note:** This is Phase 1 (panel logic, client-side TypeScript). The equivalent array
+> support in the server-side control-logic engine (`internal/controllogic`) is a separate
+> Phase 2 effort and is not yet implemented.
+
 ### 3.9 Control Logic Engine
 
 Control logic is server-side (`internal/controllogic`): always-on flow graphs that run under

docs/superpowers/plans/2026-06-24-local-arrays-panel-logic.md

@@ -0,0 +1,779 @@
+# Local Array Values — Phase 1 (Panel Logic, TypeScript) Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Add first-class array-valued local variables to the panel-logic (client TS) flow engine — declaration with dynamic/capped/fixed sizing, an array-aware expression language, mutation nodes (unifying the legacy accumulate/export/clear arrays), persistence, and binding from the plot / table / multi-LED widgets.
+
+**Architecture:** The expression evaluator (`expr.ts`) becomes value-polymorphic — `EvalValue = number | EvalValue[]` (tagged union, "Approach 1"). Array locals are declared as a new `type:'array'` `StateVar` and held per-panel in `localstate.ts`, which enforces the sizing policy on every write. Mutation is performed by new `action.array.*` nodes; reads/transforms are pure functions in the expression language. Widgets read array locals through the existing `ds:'local'` plumbing.
+
+**Tech Stack:** Preact 10 + TypeScript, bundled by esbuild via the Go tool `tools/buildfrontend/main.go` (no npm/node). Stores are the hand-rolled `web/src/lib/store.ts` writable/readable primitives.
+
+## Global Constraints
+
+- No npm / no Node.js. Frontend builds **only** via `make frontend` (esbuild, pure Go). There is **no JS test runner and no typecheck gate** — esbuild strips types without checking them. Phase-1 verification = `make frontend` builds clean + the manual smoke checklist in Task 9.
+- The authoritative automated tests for the shared array semantics live in **Phase 2 (Go `expr.go`)**, not here. Keep `expr.ts` semantics documented precisely so the Go port can mirror them exactly.
+- Booleans are numbers (`1`/`0`) at array leaves; `elem:'bool'` is display metadata only.
+- Expressions are **pure** (no side effects). Mutator-named functions (`push/set/insert/remove/pop/shift`) return **new** arrays; the sizing policy is enforced only at store time in `localstate.ts`.
+- Dynamic arrays are guarded by a global safety cap `ARRAY_MAX = 1_000_000` elements.
+- Preserve backward compatibility: existing `accumulate`/`clear`/`export` nodes keep working via aliasing + auto-declared locals.
+- Follow existing file conventions; commit frequently with `Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>`.
+
+---
+
+## File Structure
+
+- `web/src/lib/types.ts` — extend `StateVar` with array fields. (Modify)
+- `web/src/lib/expr.ts` — polymorphic value model, array literals, indexing, array functions. (Modify — the core change)
+- `web/src/lib/localstate.ts` — array init from `initial`, sizing-policy enforcement on write, array metadata. (Modify)
+- `web/src/lib/arraypolicy.ts` — **new**: pure helpers `applySizing(value, sv)` and `parseInitialArray(sv)` shared by `localstate.ts` and `logic.ts`. (Create)
+- `web/src/lib/logic.ts` — new `action.array.*` node handlers; accumulate/clear aliasing; export-by-index with custom headers; auto-declare migration in `load()`. (Modify)
+- `web/src/lib/types.ts` `LogicNodeKind` — add the new node kinds. (Modify, same file as above)
+- `web/src/lib/xml.ts` — round-trip the new `<statevar>` array attributes. (Modify)
+- `web/src/LogicEditor.tsx` — `LocalVars` array declaration form + array node palette entries + inspectors. (Modify)
+- `web/src/lib/flowDebug.ts` — compact array stringify for node value badges. (Modify)
+- `web/src/widgets/PlotWidget.tsx`, `web/src/widgets/TableWidget.tsx`, `web/src/widgets/MultiLed.tsx` (exact filenames verified in Task 7) — array source modes. (Modify)
+
+---
+
+## Task 1: Extend `StateVar` with array fields
+
+**Files:**
+- Modify: `web/src/lib/types.ts` (the `StateVar` interface, ~lines 69-76)
+
+**Interfaces:**
+- Produces: `StateVar` with new optional fields `elem?: 'number'|'bool'|'array'`, `sizing?: 'dynamic'|'capped'|'fixed'`, `capacity?: number`, and `type` union extended with `'array'`.
+
+- [ ] **Step 1: Extend the interface**
+
+In `web/src/lib/types.ts`, change the `StateVar` interface to:
+
+```ts
+export interface StateVar {
+  name: string;
+  type?: 'number' | 'bool' | 'string' | 'array';
+  initial: string;
+  unit?: string;
+  low?: number;
+  high?: number;
+  // array-only (present when type === 'array'):
+  elem?: 'number' | 'bool' | 'array';
+  sizing?: 'dynamic' | 'capped' | 'fixed';
+  capacity?: number;
+}
+```
+
+- [ ] **Step 2: Build**
+
+Run: `make frontend`
+Expected: `Frontend built successfully → …/web/dist`
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add web/src/lib/types.ts
+git commit -m "feat(logic): add array fields to StateVar type"
+```
+
+---
+
+## Task 2: Array sizing-policy helpers (`arraypolicy.ts`)
+
+**Files:**
+- Create: `web/src/lib/arraypolicy.ts`
+
+**Interfaces:**
+- Consumes: `StateVar`, `EvalValue` (Task 3 finalizes `EvalValue`; here use `type EvalValue = number | EvalValue[]` locally re-exported from `expr.ts` once Task 3 lands — for ordering, define the alias in this file and have `expr.ts` import it).
+- Produces:
+  - `export type ArrVal = number | ArrVal[];`
+  - `export const ARRAY_MAX = 1_000_000;`
+  - `export function parseInitialArray(sv: StateVar): ArrVal[]` — initial contents for an array local.
+  - `export function applySizing(arr: ArrVal[], sv: StateVar): ArrVal[]` — enforce dynamic/capped/fixed on a candidate array value.
+
+- [ ] **Step 1: Create the module**
+
+```ts
+// web/src/lib/arraypolicy.ts
+// Pure helpers for array-valued local state: parse the declared initial value
+// and enforce the declared sizing policy (dynamic / capped / fixed). Shared by
+// localstate.ts (write path) and logic.ts (node handlers + migration).
+
+import type { StateVar } from './types';
+
+export type ArrVal = number | ArrVal[];
+export const ARRAY_MAX = 1_000_000;
+
+// zeroFill builds a length-n array of zeros (flat; fixed nested init must come
+// from an explicit `initial` literal).
+function zeroFill(n: number): ArrVal[] {
+  return new Array(Math.max(0, n)).fill(0);
+}
+
+// parseInitialArray returns the starting contents of an array local.
+export function parseInitialArray(sv: StateVar): ArrVal[] {
+  const cap = sv.capacity ?? 0;
+  const raw = (sv.initial ?? '').trim();
+  let parsed: ArrVal[] | null = null;
+  if (raw) {
+    try {
+      const j = JSON.parse(raw);
+      if (Array.isArray(j)) parsed = j as ArrVal[];
+    } catch { parsed = null; }
+  }
+  if (sv.sizing === 'fixed') {
+    if (!parsed) return zeroFill(cap);
+    // truncate / zero-pad to capacity
+    const out = parsed.slice(0, cap);
+    while (out.length < cap) out.push(0);
+    return out;
+  }
+  return parsed ?? [];
+}
+
+// applySizing returns arr clamped to the declared policy.
+//   dynamic → unchanged (but globally capped at ARRAY_MAX, dropping oldest)
+//   capped  → keep at most capacity elements, dropping oldest (ring/FIFO)
+//   fixed   → exactly capacity elements (truncate / zero-pad); never grow/shrink
+export function applySizing(arr: ArrVal[], sv: StateVar): ArrVal[] {
+  const cap = sv.capacity ?? 0;
+  switch (sv.sizing) {
+    case 'fixed': {
+      const out = arr.slice(0, cap);
+      while (out.length < cap) out.push(0);
+      return out;
+    }
+    case 'capped':
+      return arr.length > cap ? arr.slice(arr.length - cap) : arr;
+    default:
+      return arr.length > ARRAY_MAX ? arr.slice(arr.length - ARRAY_MAX) : arr;
+  }
+}
+```
+
+- [ ] **Step 2: Build**
+
+Run: `make frontend`
+Expected: builds clean (module compiles; not yet imported anywhere).
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add web/src/lib/arraypolicy.ts
+git commit -m "feat(logic): add array sizing-policy helpers"
+```
+
+---
+
+## Task 3: Make `expr.ts` value-polymorphic
+
+This is the core change. `Resolver` and the evaluator move from `number` to `ArrVal = number | ArrVal[]`. Add array-literal and indexing syntax plus the array function set. Keep all existing scalar behavior identical (numbers, booleans-as-1/0, operators, ternary, the existing math funcs).
+
+**Files:**
+- Modify: `web/src/lib/expr.ts` (whole file — see current contents)
+- Modify import in: any caller of `Resolver`/`evalExpr` that assumed a `number` return — audit in Step 5.
+
+**Interfaces:**
+- Consumes: `ArrVal` from `./arraypolicy`.
+- Produces:
+  - `export type Resolver = (ds: string, name: string) => ArrVal;`
+  - `export function evalValue(src: string, resolve: Resolver): ArrVal` — full value (number or array).
+  - `export function evalExpr(src: string, resolve: Resolver): number` — **kept** for scalar callers; returns `NaN` if the value is an array or unparseable.
+  - `export function evalBool(src, resolve): boolean` — unchanged signature.
+  - `export function collectRefs(src): RefLite[]` — now also walks array-literal / index AST nodes.
+  - `export function checkExpr(src): string|null` — unchanged signature; parser now accepts the new syntax.
+
+- [ ] **Step 1: Add AST nodes for array literal and indexing**
+
+In the `Node` union add:
+
+```ts
+  | { t: 'arr'; items: Node[] }
+  | { t: 'index'; a: Node; i: Node }
+```
+
+- [ ] **Step 2: Tokenizer — add `[` and `]`**
+
+In `tokenize`, extend the single-char punctuation set to include brackets:
+
+```ts
+    if ('+-*/%<>!()?:,[]'.includes(c)) { toks.push({ k: c }); i++; continue; }
+```
+
+- [ ] **Step 3: Parser — array literals + postfix indexing**
+
+Replace `primary()` so that after producing a base node it consumes any chain of `[ expr ]`, and add the `[ … ]` literal:
+
+```ts
+  function atom(): Node {
+    const t = peek();
+    if (!t) throw new Error('unexpected end of expression');
+    if (t.k === 'num') { eat(); return { t: 'num', v: parseFloat(t.v!) }; }
+    if (t.k === '[') {
+      eat('[');
+      const items: Node[] = [];
+      if (peek()?.k !== ']') {
+        items.push(ternary());
+        while (peek()?.k === ',') { eat(','); items.push(ternary()); }
+      }
+      eat(']');
+      return { t: 'arr', items };
+    }
+    if (t.k === 'sig') {
+      eat();
+      const raw = t.v!;
+      const idx = raw.indexOf(':');
+      const ds = idx < 0 ? raw : raw.slice(0, idx);
+      const name = idx < 0 ? '' : raw.slice(idx + 1);
+      return { t: 'sig', ds, name };
+    }
+    if (t.k === 'ident') {
+      eat();
+      const id = t.v!;
+      if (id === 'true') return { t: 'num', v: 1 };
+      if (id === 'false') return { t: 'num', v: 0 };
+      if (peek()?.k === '(') {
+        eat('(');
+        const args: Node[] = [];
+        if (peek()?.k !== ')') {
+          args.push(ternary());
+          while (peek()?.k === ',') { eat(','); args.push(ternary()); }
+        }
+        eat(')');
+        return { t: 'call', fn: id, args };
+      }
+      return { t: 'var', name: id };
+    }
+    if (t.k === '(') { eat('('); const e = ternary(); eat(')'); return e; }
+    throw new Error(`unexpected token '${t.k}' in expression`);
+  }
+
+  function primary(): Node {
+    let n = atom();
+    while (peek()?.k === '[') {
+      eat('[');
+      const i = ternary();
+      eat(']');
+      n = { t: 'index', a: n, i };
+    }
+    return n;
+  }
+```
+
+(`unary` still calls `primary`; no other parser change.)
+
+- [ ] **Step 4: Evaluator — return `ArrVal`, add array funcs + indexing**
+
+Replace the evaluation section. Helpers `asNum` (coerce to number, throw on array) and `asArr` (require array) gate type errors.
+
+```ts
+import type { ArrVal } from './arraypolicy';
+
+export type Resolver = (ds: string, name: string) => ArrVal;
+
+function asNum(v: ArrVal): number {
+  if (typeof v !== 'number') throw new Error('expected a number, got an array');
+  return v;
+}
+function asArr(v: ArrVal): ArrVal[] {
+  if (!Array.isArray(v)) throw new Error('expected an array, got a number');
+  return v;
+}
+// resolve a possibly-negative index against length
+function idx(i: number, len: number): number {
+  const k = Math.trunc(i) < 0 ? len + Math.trunc(i) : Math.trunc(i);
+  if (k < 0 || k >= len) throw new Error(`index ${i} out of range (len ${len})`);
+  return k;
+}
+
+const ARR_FUNCS: Record<string, (a: ArrVal[]) => ArrVal> = {
+  len: a => asArr(a[0]).length,
+  sum: a => asArr(a[0]).reduce((s, x) => s + asNum(x), 0),
+  mean: a => { const r = asArr(a[0]); return r.length ? r.reduce((s, x) => s + asNum(x), 0) / r.length : 0; },
+  // min/max: scalar-variadic OR single-array — see ev() dispatch below
+  slice: a => { const r = asArr(a[0]); const s = a[1] === undefined ? 0 : asNum(a[1]); const e = a[2] === undefined ? r.length : asNum(a[2]); return r.slice(s, e); },
+  concat: a => asArr(a[0]).concat(asArr(a[1])),
+  reverse: a => asArr(a[0]).slice().reverse(),
+  sort: a => asArr(a[0]).slice().sort((x, y) => asNum(x) - asNum(y)),
+  scale: a => asArr(a[0]).map(x => asNum(x) * asNum(a[1])),
+  add: a => { const x = asArr(a[0]), y = asArr(a[1]); const n = Math.min(x.length, y.length); const o: ArrVal[] = []; for (let k = 0; k < n; k++) o.push(asNum(x[k]) + asNum(y[k])); return o; },
+  sub: a => { const x = asArr(a[0]), y = asArr(a[1]); const n = Math.min(x.length, y.length); const o: ArrVal[] = []; for (let k = 0; k < n; k++) o.push(asNum(x[k]) - asNum(y[k])); return o; },
+  push: a => asArr(a[0]).concat([a[1]]),
+  set: a => { const r = asArr(a[0]).slice(); r[idx(asNum(a[1]), r.length)] = a[2]; return r; },
+  insert: a => { const r = asArr(a[0]).slice(); const k = Math.max(0, Math.min(r.length, Math.trunc(asNum(a[1])))); r.splice(k, 0, a[2]); return r; },
+  remove: a => { const r = asArr(a[0]).slice(); r.splice(idx(asNum(a[1]), r.length), 1); return r; },
+  pop: a => { const r = asArr(a[0]).slice(); r.pop(); return r; },
+  shift: a => { const r = asArr(a[0]).slice(); r.shift(); return r; },
+  indexOf: a => { const r = asArr(a[0]); for (let k = 0; k < r.length; k++) if (r[k] === a[1]) return k; return -1; },
+  contains: a => { const r = asArr(a[0]); for (let k = 0; k < r.length; k++) if (r[k] === a[1]) return 1; return 0; },
+  fill: a => new Array(Math.max(0, Math.trunc(asNum(a[0])))).fill(a[1]),
+};
+
+function ev(n: Node, R: Resolver): ArrVal {
+  switch (n.t) {
+    case 'num': return n.v;
+    case 'arr': return n.items.map(it => ev(it, R));
+    case 'sig': return R(n.ds, n.name);
+    case 'var': return R('local', n.name);
+    case 'index': return asArr(ev(n.a, R))[idx(asNum(ev(n.i, R)), asArr(ev(n.a, R)).length)];
+    case 'un': return n.op === '-' ? -asNum(ev(n.a, R)) : (asNum(ev(n.a, R)) === 0 ? 1 : 0);
+    case 'tern': return asNum(ev(n.c, R)) !== 0 ? ev(n.a, R) : ev(n.b, R);
+    case 'call': {
+      const args = n.args.map(a => ev(a, R));
+      // min/max keep scalar-variadic form, plus 1-arg array form
+      if ((n.fn === 'min' || n.fn === 'max') && !(args.length === 1 && Array.isArray(args[0]))) {
+        const nums = args.map(asNum);
+        return n.fn === 'min' ? Math.min(...nums) : Math.max(...nums);
+      }
+      if (n.fn === 'min' || n.fn === 'max') {
+        const r = asArr(args[0]).map(asNum);
+        return n.fn === 'min' ? Math.min(...r) : Math.max(...r);
+      }
+      const af = ARR_FUNCS[n.fn];
+      if (af) return af(args);
+      const sf = SCALAR_FUNCS[n.fn];
+      if (sf) return sf(args.map(asNum));
+      throw new Error(`unknown function '${n.fn}'`);
+    }
+    case 'bin': {
+      const a = asNum(ev(n.a, R)), b = asNum(ev(n.b, R));
+      switch (n.op) {
+        case '+': return a + b; case '-': return a - b; case '*': return a * b;
+        case '/': return a / b; case '%': return a % b;
+        case '<': return a < b ? 1 : 0; case '<=': return a <= b ? 1 : 0;
+        case '>': return a > b ? 1 : 0; case '>=': return a >= b ? 1 : 0;
+        case '==': return a === b ? 1 : 0; case '!=': return a !== b ? 1 : 0;
+        case '&&': return (a !== 0 && b !== 0) ? 1 : 0;
+        case '||': return (a !== 0 || b !== 0) ? 1 : 0;
+        default: throw new Error(`unknown operator '${n.op}'`);
+      }
+    }
+  }
+}
+```
+
+Rename the existing `FUNCS` table to `SCALAR_FUNCS` (same entries: abs/min/max/sqrt/floor/ceil/round/sign/pow/log/exp/sin/cos) — but **remove** `min`/`max` from it since they are now handled in the `call` dispatch above.
+
+- [ ] **Step 5: Public functions — split `evalValue` / `evalExpr`**
+
+```ts
+export function evalValue(src: string, resolve: Resolver): ArrVal {
+  return ev(parseCached(src), resolve);
+}
+
+export function evalExpr(src: string, resolve: Resolver): number {
+  try {
+    const v = ev(parseCached(src), resolve);
+    return typeof v === 'number' ? v : NaN;
+  } catch {
+    return NaN;
+  }
+}
+```
+
+`evalBool` keeps calling `evalExpr` (array → NaN → false, acceptable). Update `collectRefs`'s `walk` switch to also recurse the new nodes:
+
+```ts
+      case 'arr': n.items.forEach(walk); break;
+      case 'index': walk(n.a); walk(n.i); break;
+```
+
+- [ ] **Step 6: Audit callers of `Resolver`/`evalExpr`**
+
+Run: `grep -rn "Resolver\|evalExpr\|evalValue" web/src` and confirm every resolver implementation can return `ArrVal` (returning a plain `number` still satisfies `ArrVal`). The write/condition callers that need a number keep using `evalExpr`; only array-targeting nodes (Task 4) use `evalValue`.
+
+- [ ] **Step 7: Build**
+
+Run: `make frontend`
+Expected: builds clean.
+
+- [ ] **Step 8: Commit**
+
+```bash
+git add web/src/lib/expr.ts
+git commit -m "feat(logic): array-aware expression engine (literals, indexing, array funcs)"
+```
+
+---
+
+## Task 4: Array values + sizing in `localstate.ts`
+
+**Files:**
+- Modify: `web/src/lib/localstate.ts`
+
+**Interfaces:**
+- Consumes: `parseInitialArray`, `applySizing`, `ArrVal` from `./arraypolicy`; `StateVar` from `./types`.
+- Produces: `writeLocalState(name, value, sv?)` — when `sv` is an array declaration, `applySizing` is enforced; `initLocalState` instantiates array locals from `parseInitialArray`; metadata carries `elem`/`sizing`/`capacity`.
+- Produces: `export function declaredVar(name): StateVar | undefined` — lookup used by `logic.ts` node handlers to know a local's sizing policy.
+
+- [ ] **Step 1: Track declarations + array init**
+
+Add a `decls = new Map<string, StateVar>()` populated in `initLocalState`; extend `coerce` for `type==='array'`:
+
+```ts
+import { parseInitialArray, applySizing, type ArrVal } from './arraypolicy';
+
+const decls = new Map<string, StateVar>();
+export function declaredVar(name: string): StateVar | undefined { return decls.get(name); }
+
+function coerce(v: StateVar): any {
+  switch (v.type) {
+    case 'bool': return v.initial === 'true' || v.initial === '1';
+    case 'string': return v.initial;
+    case 'array': return parseInitialArray(v);
+    default: { const n = parseFloat(v.initial); return isNaN(n) ? 0 : n; }
+  }
+}
+```
+
+In `initLocalState`, `decls.set(v.name, v)` before publishing, and extend the metadata object with `elem: v.elem, sizing: v.sizing, capacity: v.capacity` (add these optional fields to `SignalMeta` in `types.ts`).
+
+- [ ] **Step 2: Enforce sizing on write**
+
+```ts
+export function writeLocalState(name: string, value: any): void {
+  const sv = decls.get(name);
+  let v = value;
+  if (sv?.type === 'array' && Array.isArray(value)) v = applySizing(value as ArrVal[], sv);
+  valueW(name).set({ value: v, quality: 'good', ts: new Date().toISOString() });
+}
+```
+
+- [ ] **Step 3: Build**
+
+Run: `make frontend`
+Expected: builds clean.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add web/src/lib/localstate.ts web/src/lib/types.ts
+git commit -m "feat(logic): array local init + sizing enforcement in localstate"
+```
+
+---
+
+## Task 5: Array action nodes + accumulate/export unification in `logic.ts`
+
+**Files:**
+- Modify: `web/src/lib/types.ts` (`LogicNodeKind` union — add `'action.array.push' | 'action.array.set' | 'action.array.remove' | 'action.array.pop' | 'action.array.clear'`)
+- Modify: `web/src/lib/logic.ts`
+
+**Interfaces:**
+- Consumes: `evalValue`, `evalExpr` from `./expr`; `writeLocalState`, `getLocalValueStore`, `declaredVar` from `./localstate`; `applySizing` from `./arraypolicy`.
+- Produces: node handlers for the five `action.array.*` kinds; `accumulate`→push and `clear`→array.clear aliasing; export-by-index with custom header labels; `ensureArrayDecls(graph)` auto-declare migration called from `load()`.
+
+- [ ] **Step 1: Read current array machinery**
+
+Run: `grep -n "arrays\|accumulate\|action.export\|action.clear\|runNode\|case 'action" web/src/lib/logic.ts` to locate the dispatch switch and the legacy `arrays:Map` (around the lines noted in the design's code map: store ~225, accumulate ~614, export ~626, clear ~632, exportArrays ~733).
+
+- [ ] **Step 2: Replace the `{t,v}` store with array-local reads/writes**
+
+Array locals are the single source of truth. Implement a helper to read the current array value of a local:
+
+```ts
+import { get } from './store';
+import { getLocalValueStore, writeLocalState, declaredVar } from './localstate';
+import { applySizing, type ArrVal } from './arraypolicy';
+
+function curArray(name: string): ArrVal[] {
+  const v = get(getLocalValueStore(name)).value;
+  return Array.isArray(v) ? (v as ArrVal[]) : [];
+}
+```
+
+(If `store.ts` lacks a synchronous `get`, read via a one-shot subscribe; confirm in Step 1.)
+
+- [ ] **Step 3: Implement the five node handlers**
+
+In the node dispatch switch:
+
+```ts
+case 'action.array.push': {
+  const arr = curArray(p.array);
+  writeLocalState(p.array, [...arr, evalValue(p.expr, ctx.resolve)]);
+  break;
+}
+case 'action.array.set': {
+  const arr = curArray(p.array).slice();
+  const path = String(p.index ?? '').split(',').map(s => Math.trunc(evalExpr(s, ctx.resolve)));
+  setPath(arr, path, evalValue(p.expr, ctx.resolve));      // setPath: nested index assignment, defined below
+  writeLocalState(p.array, arr);
+  break;
+}
+case 'action.array.remove': {
+  const arr = curArray(p.array).slice();
+  const i = Math.trunc(evalExpr(p.index, ctx.resolve));
+  const k = i < 0 ? arr.length + i : i;
+  if (k >= 0 && k < arr.length) arr.splice(k, 1);
+  writeLocalState(p.array, arr);
+  break;
+}
+case 'action.array.pop': {
+  const arr = curArray(p.array).slice(); arr.pop();
+  writeLocalState(p.array, arr);
+  break;
+}
+case 'action.array.clear': {
+  const sv = declaredVar(p.array);
+  writeLocalState(p.array, sv ? applySizing([], sv) : []);   // fixed → zero-refill via applySizing
+  break;
+}
+```
+
+Add `setPath`:
+
+```ts
+function setPath(arr: ArrVal[], path: number[], v: ArrVal): void {
+  let cur: ArrVal[] = arr;
+  for (let d = 0; d < path.length - 1; d++) {
+    let k = path[d]; if (k < 0) k = cur.length + k;
+    if (!Array.isArray(cur[k])) cur[k] = [];
+    cur = cur[k] as ArrVal[];
+  }
+  let last = path[path.length - 1]; if (last < 0) last = cur.length + last;
+  cur[last] = v;
+}
+```
+
+- [ ] **Step 4: Alias accumulate/clear and rewrite export**
+
+In the dispatch switch, make the legacy kinds delegate:
+
+```ts
+case 'action.accumulate':  // legacy alias → push
+  { const arr = curArray(p.array); writeLocalState(p.array, [...arr, evalValue(p.expr, ctx.resolve)]); }
+  break;
+case 'action.clear':       // legacy alias → array.clear
+  { const sv = declaredVar(p.array); writeLocalState(p.array, sv ? applySizing([], sv) : []); }
+  break;
+```
+
+Rewrite `action.export` to read array locals by column and emit index-aligned CSV with custom headers. Parse `p.columns` as `[{array, label}]`; header row uses `label || array`; row `r` joins `col[r] ?? ''`:
+
+```ts
+case 'action.export': {
+  const cols = JSON.parse(p.columns || '[]') as { array: string; label?: string }[];
+  const data = cols.map(c => curArray(c.array));
+  const rows = Math.max(0, ...data.map(d => d.length));
+  const header = cols.map(c => csvCell(c.label || c.array)).join(',');
+  const lines = [header];
+  for (let r = 0; r < rows; r++) {
+    lines.push(data.map(d => (r < d.length ? csvCell(String(d[r])) : '')).join(','));
+  }
+  downloadCsv(lines.join('\n'), p.filename || 'export.csv');   // reuse existing blob-download helper
+  break;
+}
+```
+
+(Keep/rename the existing CSV-escape and blob-download helpers as `csvCell`/`downloadCsv`; drop `exportArrays`/`interpAt` and the `align` param handling.)
+
+- [ ] **Step 5: Auto-declare migration in `load()`**
+
+After the graph is loaded but before subscriptions, ensure any array referenced by an array node / accumulate / export but **not** declared gets a dynamic numeric array local:
+
+```ts
+function ensureArrayDecls(graph: LogicGraph, vars: StateVar[]): StateVar[] {
+  const have = new Set(vars.map(v => v.name));
+  const out = vars.slice();
+  const need = (name: string) => {
+    if (name && !have.has(name)) { have.add(name); out.push({ name, type: 'array', elem: 'number', sizing: 'dynamic', initial: '' }); }
+  };
+  for (const n of graph.nodes) {
+    if (n.kind === 'action.accumulate' || n.kind === 'action.clear' || n.kind.startsWith('action.array.')) need(n.params.array);
+    if (n.kind === 'action.export') { try { (JSON.parse(n.params.columns || '[]') as any[]).forEach(c => need(c.array)); } catch {} }
+  }
+  return out;
+}
+```
+
+Call this so the resulting list is passed to `initLocalState` (wherever `load()` currently calls it; if `load()` doesn't own statevars, thread the merged list through the same path the panel uses to init local state).
+
+- [ ] **Step 6: Build**
+
+Run: `make frontend`
+Expected: builds clean.
+
+- [ ] **Step 7: Commit**
+
+```bash
+git add web/src/lib/logic.ts web/src/lib/types.ts
+git commit -m "feat(logic): array action nodes + accumulate/export unification + migration"
+```
+
+---
+
+## Task 6: Persist array `<statevar>` attributes (`xml.ts`)
+
+**Files:**
+- Modify: `web/src/lib/xml.ts` (statevar read ~lines 67-77 and the corresponding write path)
+
+**Interfaces:**
+- Produces: `<statevar>` round-trips `elem`, `sizing`, `capacity` in addition to existing attrs, only emitting them when present.
+
+- [ ] **Step 1: Write path — emit array attrs**
+
+Where statevars are serialized, append the optional attrs:
+
+```ts
+function statevarXml(v: StateVar): string {
+  const a = [`name="${esc(v.name)}"`, `type="${v.type ?? 'number'}"`, `initial="${esc(v.initial)}"`];
+  if (v.unit) a.push(`unit="${esc(v.unit)}"`);
+  if (v.low !== undefined) a.push(`low="${v.low}"`);
+  if (v.high !== undefined) a.push(`high="${v.high}"`);
+  if (v.type === 'array') {
+    if (v.elem) a.push(`elem="${v.elem}"`);
+    if (v.sizing) a.push(`sizing="${v.sizing}"`);
+    if (v.capacity !== undefined) a.push(`capacity="${v.capacity}"`);
+  }
+  return `<statevar ${a.join(' ')}/>`;
+}
+```
+
+(Adapt to the file's existing serialization style — match how `unit`/`low`/`high` are currently emitted.)
+
+- [ ] **Step 2: Read path — parse array attrs**
+
+Where `<statevar>` is parsed into a `StateVar`, add:
+
+```ts
+  elem: el.getAttribute('elem') as any || undefined,
+  sizing: el.getAttribute('sizing') as any || undefined,
+  capacity: el.hasAttribute('capacity') ? Number(el.getAttribute('capacity')) : undefined,
+```
+
+- [ ] **Step 3: Build + round-trip sanity (manual)**
+
+Run: `make frontend`. Then in Task 9's smoke test confirm an array statevar survives save→reload.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add web/src/lib/xml.ts
+git commit -m "feat(logic): round-trip array statevar attributes in panel XML"
+```
+
+---
+
+## Task 7: Editor — array declaration form + array nodes
+
+**Files:**
+- Modify: `web/src/LogicEditor.tsx` (the `LocalVars` subcomponent + the palette node list + the inspector)
+- Modify: `web/src/lib/flowDebug.ts` (compact array badge formatting)
+
+**Interfaces:**
+- Consumes: `StateVar` shape (Task 1), the new node kinds (Task 5).
+- Produces: UI to declare array locals and place/inspect `action.array.*` nodes; debug badges that stringify arrays compactly.
+
+- [ ] **Step 1: `LocalVars` array form**
+
+In the `LocalVars` subcomponent, when the type select value is `array`, reveal: an `elem` select (number/bool/array), a `sizing` select (dynamic/capped/fixed), a `capacity` number input (shown for capped/fixed), and the existing `initial` text field repurposed as a JSON literal with inline `JSON.parse` validation (red hint on parse error). Persist via the existing `onStateVarsChange` path.
+
+- [ ] **Step 2: Palette + inspector for array nodes**
+
+Add the five `action.array.*` kinds to the Actions palette group (label/icon consistent with existing entries). In the inspector `switch`, add cases rendering: `array` (a select of declared array-local names), and `expr`/`index` fields using the existing `ExprField` (which already runs `checkExpr`). `action.array.set` shows both `index` (path, comma-separated) and `expr`.
+
+- [ ] **Step 3: Compact array badges**
+
+In `flowDebug.ts`, where a node value is stringified for the badge, format arrays as e.g. `[1, 2, 3, …](n=N)` truncated to the first ~3 elements:
+
+```ts
+export function fmtBadge(v: unknown): string {
+  if (Array.isArray(v)) {
+    const head = v.slice(0, 3).map(x => Array.isArray(x) ? '[…]' : String(x)).join(', ');
+    return `[${head}${v.length > 3 ? ', …' : ''}](n=${v.length})`;
+  }
+  return typeof v === 'number' ? String(+v.toFixed(4)) : String(v);
+}
+```
+
+Wire `fmtBadge` into the existing badge render site (replace the inline number formatting).
+
+- [ ] **Step 4: Build**
+
+Run: `make frontend`
+Expected: builds clean.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add web/src/LogicEditor.tsx web/src/lib/flowDebug.ts
+git commit -m "feat(logic): array local declaration form + array nodes + array debug badges"
+```
+
+---
+
+## Task 8: Widgets read array locals
+
+**Files (verify exact paths first):**
+- Run: `ls web/src/widgets` and `grep -rln "bitset\|MultiLed\|multi-led\|TableWidget\|PlotWidget" web/src/widgets`
+- Modify: the plot widget, table widget, multi-LED/bitset widget.
+
+**Interfaces:**
+- Consumes: a bound local whose `SignalValue.value` may be `ArrVal[]`; metadata `elem`/`sizing`/`capacity` from `getLocalMetaStore`.
+
+- [ ] **Step 1: Plot — accept a 1-D numeric array local as a waveform**
+
+In the plot widget's value-ingest path, when a bound signal's value is a numeric array, feed it through the **same** code path already used for EPICS `float64[]` waveform samples (multidimensional/FFT/waterfall). Nested arrays → render the existing "unsupported" placeholder. (Locate the waveform branch via `grep -n "Array.isArray\|waveform\|float64" web/src/widgets/PlotWidget.tsx`.)
+
+- [ ] **Step 2: Table — array source mode**
+
+Add an `array` source mode (config flag) that, when the bound value is an array, renders one row per element (index + value with the per-signal value format). For `elem:'array'` (2-D), rows = outer index, configured columns map to inner positions. Scalars → existing multi-signal behavior.
+
+- [ ] **Step 3: Multi-LED — array source mode**
+
+Add an `array` source mode: render one LED per element, lit by element truthiness; LED count tracks array length live; when meta `elem==='bool'`, use the declared on/off labels.
+
+- [ ] **Step 4: Build**
+
+Run: `make frontend`
+Expected: builds clean.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add web/src/widgets
+git commit -m "feat(widgets): array source modes for plot, table, multi-LED"
+```
+
+---
+
+## Task 9: Manual smoke verification + docs
+
+**Files:**
+- Modify: `TODO.md` (do NOT check the box yet — Phase 2 Go port still pending; add a sub-note that panel-logic arrays are done)
+- Modify: `docs/TECHNICAL_SPEC.md` (document array statevars + array expression functions + the export change)
+
+- [ ] **Step 1: Build the whole app**
+
+Run: `make all`
+Expected: frontend + backend build clean.
+
+- [ ] **Step 2: Manual smoke checklist** (run `go run ./cmd/uopi`, open a panel in edit mode → Logic tab)
+
+  - Declare a `capped` array `hist` capacity 5; add a `trigger.timer` → `action.array.push{array:hist, expr:{ds:stub:sine_1hz}}`; in view mode confirm `hist` rings at 5 elements (debug badge shows `[…](n=5)`).
+  - Add `action.write{target: avg, expr: mean(hist)}` (scalar local `avg`); confirm it tracks.
+  - Indexing: `action.write{target: last, expr: hist[-1]}` updates to the newest sample.
+  - `fixed` array `grid` capacity 4 initial `[0,0,0,0]`; `action.array.set{array:grid, index:"2", expr:42}`; confirm element 2 = 42 and length stays 4.
+  - Save the panel, reload it, confirm the array statevars + nodes persist (Task 6).
+  - Legacy: open/confirm an existing panel using `action.accumulate`/`action.export` still records and exports CSV (now index-aligned; header uses custom labels).
+  - Widgets: bind `hist` to a plot (waveform), a table (one row per element), and a multi-LED (one LED per element) and confirm they render and update live.
+
+- [ ] **Step 3: Commit docs**
+
+```bash
+git add TODO.md docs/TECHNICAL_SPEC.md
+git commit -m "docs(logic): document panel-logic array locals"
+```
+
+---
+
+## Self-Review Notes (spec coverage)
+
+- Data model (spec §2) → Task 1 + Task 2 (`arraypolicy`).
+- Expression engine (spec §3) → Task 3 (all functions, indexing, literals, negative index, errors, ref-collection).
+- Mutation nodes + accumulate/export unification + migration (spec §4) → Task 5.
+- Persistence panel XML (spec §5) → Task 6. (Control-logic Go persistence = Phase 2.)
+- Editor UI + debug badges (spec §6, panel side) → Task 7. (Control editor = Phase 2.)
+- Widgets (spec §7) → Task 8.
+- Testing (spec §8): TS has no runner → manual smoke (Task 9); the authoritative automated suite + cross-engine parity table is **Phase 2 (Go)**.
+
+**Deferred to Phase 2 (separate plan):** all of `internal/controllogic` (boxed `value` in `expr.go`, `Graph.StateVars`, `getLocal`/`setLocal` policy, JSON round-trip, config-apply/snapshot boxing), `ControlLogicEditor.tsx` LocalVars parity, the Go debug-event array payload, and the full Go test + parity suite.

docs/superpowers/specs/2026-06-24-local-arrays-design.md

@@ -0,0 +1,266 @@
+# Design: Local array values for the node-editor flow engines
+
+**Date:** 2026-06-24
+**Status:** Approved (design phase)
+**TODO refs:** "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" and "Control loop → add full support to server side array values".
+
+## 1. Goal & scope
+
+Add first-class **array-valued local variables** to both flow engines:
+
+- **Panel logic** (client TS): `web/src/lib/logic.ts`, `LogicEditor.tsx`,
+  `web/src/lib/types.ts`, `web/src/lib/expr.ts`, `web/src/lib/localstate.ts`,
+  `web/src/lib/xml.ts`.
+- **Control logic** (server Go): `internal/controllogic/` (`model.go`,
+  `engine.go`, `expr.go`), editor `web/src/ControlLogicEditor.tsx`.
+
+**Build order:** design both together; implement **panel logic (TS) first**,
+then port the same design to control logic (Go). The panel `StateVar` schema is
+the richer reference and doing TS first de-risks the expression-language change
+before the Go port.
+
+**In scope for v1:** declaration + sizing policies, an array-aware expression
+language (shared by both engines), array mutation nodes, persistence, **and
+widget binding** (multi-LED/bitset, table, plot read array locals).
+
+## 2. Data model — array local declaration
+
+A new array kind on the existing `StateVar` (TS `types.ts`; mirrored as a Go
+struct in control logic, which gains state-var declarations for the first time):
+
+```
+StateVar {
+  name: string
+  type: 'number' | 'bool' | 'string' | 'array'   // 'array' is new
+  initial: string            // arrays: JSON literal e.g. "[0,0,0]" / "[[1,2],[3,4]]", or "" = empty/zero-fill
+  unit?, low?, high?         // existing scalar fields
+
+  // present only when type === 'array':
+  elem?: 'number' | 'bool' | 'array'  // element type; 'array' ⇒ nested (recursive, arbitrary depth, jagged allowed)
+  sizing?: 'dynamic' | 'capped' | 'fixed'   // default 'dynamic'
+  capacity?: number          // required for capped/fixed
+}
+```
+
+Semantics:
+
+- **dynamic** — unbounded, guarded by a global safety cap (1e6 elements) to
+  prevent runaway growth.
+- **capped** — `capacity` max; pushing past full **drops the oldest** element
+  (ring / FIFO).
+- **fixed** — exactly `capacity` slots. Initialised from the `initial` literal
+  (truncated / zero-padded to `capacity`), else **zero-filled**. `push` is a
+  no-op (write via index/set); `clear` zero-refills rather than emptying.
+- **initial** — non-empty JSON literal is parsed and used; empty ⇒ dynamic and
+  capped start `[]`, fixed starts zero-filled.
+- `elem: 'bool'` is **display metadata only**. Runtime leaves are numeric
+  `1`/`0` (consistent with the engine's existing "booleans are 1/0" rule);
+  widgets use the declaration to render on/off.
+
+**Declaration-time validation:** capped/fixed require `capacity >= 1`;
+`initial`, if non-empty, must parse as JSON and match the declared element
+type / nesting. Errors surface inline in the editor.
+
+## 3. Expression engine (`expr.ts` + `expr.go`)
+
+**Value model (tagged union — "Approach 1"):**
+
+- TS: `type EvalValue = number | EvalValue[]`. The evaluator returns
+  `EvalValue`; functions/indexing type-check at runtime and throw on misuse
+  (caught → node error badge).
+- Go: a boxed `value{ num float64; arr []value; isArr bool }`. `Resolver`
+  returns `value`; every `*Node.eval` returns `value` (a contained, mechanical
+  refactor of `expr.go`, which today returns `float64`). The `float64` leaf
+  stays the fast path.
+
+**New syntax (both parsers):**
+
+- **Array literal:** `[a, b, c]`, nested `[[1,2],[3,4]]`.
+- **Indexing:** postfix `expr[expr]`, chainable `a[i][j]`. Index rounds to int;
+  **negative index counts from the end** (`a[-1]` = last); out-of-range → node
+  error.
+
+**Functions** — added to the existing `abs/min/max/sqrt/...` table. All the
+read/transform functions are **pure** (return new values; never mutate a local):
+
+| Function | Result | Meaning / notes |
+|---|---|---|
+| `len(a)` | number | element count (top level) |
+| `sum(a)`, `mean(a)`, `min(a)`, `max(a)` | number | over a 1-D numeric array; error if elements are arrays |
+| `slice(a, s, e)` | array | subrange, `e` exclusive, negative indices allowed |
+| `concat(a, b)` | array | join |
+| `reverse(a)` | array | |
+| `sort(a)` | array | ascending numeric |
+| `scale(a, k)` | array | element-wise `a[i]*k` |
+| `add(a, b)`, `sub(a, b)` | array | element-wise pairwise; length = min(len a, len b) |
+| `push(a, v)` | array | copy with `v` appended |
+| `set(a, i, v)` | array | copy with element `i` replaced (negative `i` ok) |
+| `insert(a, i, v)` | array | copy with `v` inserted at `i` |
+| `remove(a, i)` | array | copy without element `i` |
+| `pop(a)` | array | copy without the last element (read it with `a[-1]`) |
+| `shift(a)` | array | copy without the first element (read with `a[0]`) |
+| `indexOf(a, v)` | number | first index of `v`, else `-1` |
+| `contains(a, v)` | number | `1`/`0` |
+| `fill(n, v)` | array | new length-`n` array of `v` |
+
+- `min`/`max` keep their existing **scalar variadic** form (`min(x,y,z)`) and
+  gain a 1-arg **array** form (`min(a)`) — dispatch on arg count + type.
+- **Resolution:** a bare identifier naming an array local returns the whole
+  array value; `{ds:sig}` waveform signals (EPICS `float64[]`) become first-class
+  array values usable by every function above.
+
+**Purity & persistence interplay:** the mutator-named functions
+(`push/set/insert/remove/pop/shift`) are **immutable transforms** — they return a
+new array and do not touch the local. You persist a result by writing it back;
+the **sizing policy is enforced at store time** in `writeLocalState` (TS) /
+`setLocal` (Go) whenever the write target is a typed array local (ring-drop for
+capped, clamp / no-op for fixed). The mutation nodes (§4) are convenient, visible
+sugar for "store with policy".
+
+**Errors** (e.g. `sum` of nested array, indexing a scalar, `add` of non-arrays)
+throw in the evaluator and surface as the node's error reason via the existing
+`checkExpr` validation + runtime-catch / badge path.
+
+**Ref-collection** (`collectRefs` / `CollectRefs`) walks the new literal/index
+AST so subscriptions still discover every `{ds:sig}` inside array expressions.
+
+## 4. Mutation nodes + accumulate/export unification
+
+**New action nodes** (panel `LogicNodeKind`, mirrored in Go control-logic kinds):
+
+- `action.array.push{array, expr}` — append `eval(expr)`; sizing-policy aware
+  (ring-drop if capped; no-op if fixed).
+- `action.array.set{array, index, expr}` — store at `eval(index)`. Supports
+  **nested targets via an index path**: `index = "i, j"` ⇒ `a[i][j]`. Negative
+  indices allowed; out-of-range → node error. (This is the imperative
+  path-assignment style.)
+- `action.array.remove{array, index}` — remove element at index (in place).
+- `action.array.pop{array}` — remove last element (in place).
+- `action.array.clear{array}` — empty (dynamic/capped) or zero-refill (fixed).
+
+These are the sizing-policy-aware, in-place counterparts to the pure expression
+functions.
+
+**Unification of the existing `{t,v}` array system (decision: unify):**
+
+- `action.accumulate{array, expr}` → reframed as `action.array.push` (append,
+  policy-enforced). Old kind **kept as a compile alias** so saved panels run.
+- `action.clear{array}` → `action.array.clear` (alias retained).
+- `action.export{columns, align, filename}` → serializes **array locals** by
+  column. Array locals are plain numeric (no per-sample `t`), so **time-based
+  alignment (`common`/`any`/`interpolate`) is dropped**; columns are emitted
+  **side-by-side by index** (ragged columns padded blank). The `align` param is
+  ignored and hidden in the inspector. To keep a timestamp column, push
+  `{sys:time}` into a parallel array local and add it as a column.
+- **Custom column names:** each export column keeps its `label`, surfaced as an
+  **editable header name** in the inspector (default = array-local name); the CSV
+  header row uses the chosen names.
+
+**Migration (non-destructive, at engine `load()`):** any
+`accumulate`/`clear`/`export` node referencing an array name with **no** matching
+`StateVar` declaration triggers an **auto-declared dynamic numeric array local**
+of that name. No file rewrite.
+
+## 5. Persistence
+
+**Panel logic (XML, `xml.ts`):** `<statevar>` gains optional array attributes,
+written only for arrays:
+
+```xml
+<statevar name="hist" type="array" elem="number" sizing="capped" capacity="100" initial=""/>
+<statevar name="grid" type="array" elem="array" sizing="fixed" capacity="4" initial="[[0,0],[0,0]]"/>
+```
+
+Round-trips through the existing verbatim-body store (no Go change for panels).
+New nodes serialize via the existing `<node><param/></node>` mechanism.
+
+**Control logic (Go, `model.go`):** control logic has **no** state-var
+declarations today (`locals` is an untyped `map[string]float64`). Additions:
+
+- `Graph` gains `StateVars []StateVar` (Go struct mirroring the TS shape:
+  `Name, Type, Elem, Sizing string; Capacity int; Initial, Unit string; Low,
+  High float64`), serialized in `controllogic.json`.
+- `compiledGraph.locals` changes from `map[string]float64` to
+  `map[string]value`, initialised from `StateVars` (applying sizing/initial) at
+  compile time.
+- `getLocal`/`setLocal` operate on `value`; `setLocal` enforces sizing policy.
+  Config-apply / snapshot paths that read/write locals as `float64` box/unbox.
+
+**Versioning:** control-logic graphs are already git-style versioned; the new
+`StateVars` field rides along in each revision (no diff-engine change — just more
+JSON).
+
+## 6. Editor UI + debug/live badges
+
+**Panel `LogicEditor.tsx`:** the `LocalVars` palette subcomponent gains an array
+declaration form (type=array reveals element-type / sizing / capacity / `initial`
+JSON with inline validation). New array action nodes added to the Actions palette
+group with inspectors (array name + expr/index fields, reusing `ExprField` with
+array-aware `checkExpr`).
+
+**Control `ControlLogicEditor.tsx`:** control logic has **no** local-var
+declaration UI today. Add a `LocalVars` panel mirroring the panel editor (same
+component, driven by `Graph.StateVars`) plus the array nodes in its palette. This
+brings control-logic locals to parity — scalars *and* arrays become declarable
+there for the first time.
+
+**Debug/live badges (`flowDebug.ts` + Go `DebugObserver` / synthetic trace):**
+array node values render as a truncated literal, e.g. `[1, 2, 3, …](n=100)`. The
+Go debug event payload (`debugNode`) and the synthetic trace already serialize a
+value — extended to carry array JSON; the badge formatter stringifies arrays
+compactly.
+
+## 7. Widgets reading array locals
+
+The `ds:'local'` plumbing already routes through `stores.ts`/`ws.ts`; the change
+is that a local's `SignalValue.value` can be an array (number / nested), held and
+initialised per panel instance by `localstate.ts`. No new widget types — new
+source modes on three existing widgets:
+
+- **Plot** — a 1-D numeric array local binds as a **waveform sample** (same path
+  EPICS `float64[]` waveforms already use for multidimensional/FFT/waterfall).
+  Each engine tick that rewrites the array updates the trace. Nested arrays show
+  "unsupported shape".
+- **Table widget** — gains an **array source mode**: bound to one array local,
+  renders **one row per element** (index + value, per-signal value-format applied).
+  For an `elem:'array'` (2-D) local, rows are indices and the configured columns
+  map to inner-array positions. Falls back to multi-signal mode for scalars.
+- **Multi-LED / bitset** — gains an **array source mode**: one LED per element,
+  lit per element truthiness; when `elem:'bool'`, on/off labels come from the
+  declaration. Existing integer-bitset mode unchanged.
+
+`getLocalMetaStore` carries `elem`/`sizing`/`capacity` so widgets self-configure
+(e.g. multi-LED LED count = array length, growing/shrinking live for dynamic
+arrays).
+
+## 8. Testing
+
+- **TS unit (expr):** literals; indexing (negative, nested, out-of-range error);
+  every new function incl. type-error cases; sizing-policy enforcement on store
+  (ring drop-oldest, fixed no-op / zero-refill); accumulate→push migration; CSV
+  export by-index with custom headers.
+- **Go unit (`internal/controllogic`):** port of the expr suite (boxed `value`,
+  all functions/indexing/errors); `StateVars` init from declarations; `setLocal`
+  policy enforcement; JSON round-trip of `StateVars`; config-apply/snapshot with
+  boxed locals.
+- **Cross-engine parity:** a `(expr, expected)` table asserted identical in both
+  `expr.ts` and `expr.go` to keep them in lockstep.
+- **Widgets:** light component tests for the new array source modes if widget
+  tests exist; else manual verification.
+- **Gates:** `gofmt`, `go vet`, `go test ./... -race`, frontend typecheck/build.
+
+## 9. Risks
+
+- **Go `expr.go` refactor (`float64` → boxed `value`):** touches every node's
+  `eval` and the `Resolver`. Mechanical but broad; the parity test guards
+  behavioral drift from `expr.ts`.
+- **Backward compatibility of `accumulate`/`export`:** aliasing + auto-declared
+  locals keep old panels running, but the **dropped time-alignment in export** is
+  a behavioral change for any panel relying on `interpolate`/`common` align. Call
+  this out in release notes.
+- **Two engines staying in lockstep:** the function set and semantics must match
+  exactly across TS and Go; the cross-engine parity fixture is the safeguard.
+- **Hot-path purity:** array expression functions are evaluated repeatedly; they
+  must remain allocation-light and side-effect-free (mutation only at store time).

internal/config/config.go

@@ -7,6 +7,9 @@ import (
 	"strings"
 
 	"github.com/BurntSushi/toml"
+
+	"github.com/uopi/uopi/internal/datasource/modbus"
+	"github.com/uopi/uopi/internal/datasource/scpi"
 )
 
 type Config struct {
@@ -194,6 +197,8 @@ type DatasourceConfig struct {
 	EPICS     EPICSConfig     `toml:"epics"`
 	PVA       PVAConfig       `toml:"pva"`
 	Synthetic SyntheticConfig `toml:"synthetic"`
+	Modbus    modbus.Config   `toml:"modbus"`
+	SCPI      scpi.Config     `toml:"scpi"`
 }
 
 type StubConfig struct {

internal/controllogic/engine.go

@@ -897,7 +897,7 @@ func (cg *compiledGraph) activate(triggerID string) {
 		dt = float64(now-last) / 1e9
 	}
 
-	resolve := func(ds, name string) float64 {
+	resolve := func(ds, name string) Value { // shim: was float64 (Task 4 removes)
 		switch ds {
 		case "sys":
 			if name == "dt" {

internal/controllogic/expr.go

@@ -2,16 +2,15 @@
 //
 // Supports numbers, booleans (true/false → 1/0), arithmetic (+ - * / %),
 // comparison (< <= > >= == !=), boolean (&& || !), ternary (a ? b : c),
-// parentheses, and a handful of math functions. Two kinds of variable
-// reference are resolved live at evaluation time:
+// parentheses, array literals ([a, b, c]), postfix indexing (arr[i]), and a set
+// of math + array functions. Two kinds of variable reference are resolved live:
 //
-//	{ds:name}   a data-source signal value (the brace content is split on the
-//	            FIRST ':' so EPICS PV names like "MY:PV:NAME" work).
+//	{ds:name}   a data-source signal value (brace content split on FIRST ':').
 //	bareIdent   a graph-local state variable (data source "local").
 //
-// Booleans are represented as numbers: comparisons / logical ops yield 1 or 0,
-// and any nonzero value is truthy. The evaluator never uses reflection or eval;
-// it walks a parsed AST against a caller-supplied Resolver.
+// Values are either a scalar (float64; booleans 1/0) or an array ([]Value). The
+// evaluator never uses reflection or eval; it walks a parsed AST against a
+// caller-supplied Resolver.
 package controllogic
 
 import (
@@ -22,8 +21,8 @@ import (
 	"sync"
 )
 
-// Resolver returns the current numeric value of a signal/local reference.
-type Resolver func(ds, name string) float64
+// Resolver returns the current value of a signal/local reference.
+type Resolver func(ds, name string) Value
 
 // RefLite identifies one signal/local reference read by an expression.
 type RefLite struct {
@@ -33,11 +32,13 @@ type RefLite struct {
 
 // ── AST ──────────────────────────────────────────────────────────────────────
 
-type exprNode interface{ eval(R Resolver) float64 }
+type exprNode interface{ eval(R Resolver) Value }
 
 type numNode struct{ v float64 }
 type sigNode struct{ ds, name string }
 type varNode struct{ name string }
+type arrNode struct{ items []exprNode }
+type indexNode struct{ a, i exprNode }
 type unNode struct {
 	op string
 	a  exprNode
@@ -52,33 +53,84 @@ type callNode struct {
 	args []exprNode
 }
 
-func (n numNode) eval(R Resolver) float64 { return n.v }
-func (n sigNode) eval(R Resolver) float64 { return R(n.ds, n.name) }
-func (n varNode) eval(R Resolver) float64 { return R("local", n.name) }
-func (n unNode) eval(R Resolver) float64 {
-	if n.op == "-" {
-		return -n.a.eval(R)
+func mustNum(v Value) float64 {
+	f, err := asNum(v)
+	if err != nil {
+		panic(err)
 	}
-	if n.a.eval(R) == 0 {
-		return 1
-	}
-	return 0
+	return f
 }
-func (n ternNode) eval(R Resolver) float64 {
-	if n.c.eval(R) != 0 {
+func mustArr(v Value) []Value {
+	a, err := asArr(v)
+	if err != nil {
+		panic(err)
+	}
+	return a
+}
+
+func (n numNode) eval(R Resolver) Value { return n.v }
+func (n sigNode) eval(R Resolver) Value { return R(n.ds, n.name) }
+func (n varNode) eval(R Resolver) Value { return R("local", n.name) }
+func (n arrNode) eval(R Resolver) Value {
+	out := make([]Value, len(n.items))
+	for i, it := range n.items {
+		out[i] = it.eval(R)
+	}
+	return out
+}
+func (n indexNode) eval(R Resolver) Value {
+	arr := mustArr(n.a.eval(R))
+	k, err := idxResolve(mustNum(n.i.eval(R)), len(arr))
+	if err != nil {
+		panic(err)
+	}
+	return arr[k]
+}
+func (n unNode) eval(R Resolver) Value {
+	if n.op == "-" {
+		return -mustNum(n.a.eval(R))
+	}
+	if mustNum(n.a.eval(R)) == 0 {
+		return 1.0
+	}
+	return 0.0
+}
+func (n ternNode) eval(R Resolver) Value {
+	if mustNum(n.c.eval(R)) != 0 {
 		return n.a.eval(R)
 	}
 	return n.b.eval(R)
 }
-func (n callNode) eval(R Resolver) float64 {
-	args := make([]float64, len(n.args))
+func (n callNode) eval(R Resolver) Value {
+	args := make([]Value, len(n.args))
 	for i, a := range n.args {
 		args[i] = a.eval(R)
 	}
-	return funcs[n.fn](args)
+	// min/max: scalar-variadic OR single-array form.
+	if n.fn == "min" || n.fn == "max" {
+		if len(args) == 1 {
+			if arr, ok := args[0].([]Value); ok {
+				return reduceMinMax(n.fn, arr)
+			}
+		}
+		nums := make([]Value, len(args))
+		copy(nums, args)
+		return reduceMinMax(n.fn, nums)
+	}
+	if af, ok := arrFuncs[n.fn]; ok {
+		return af(args)
+	}
+	if sf, ok := scalarFuncs[n.fn]; ok {
+		nums := make([]float64, len(args))
+		for i, a := range args {
+			nums[i] = mustNum(a)
+		}
+		return sf(nums)
+	}
+	panic(fmt.Errorf("unknown function %q", n.fn))
 }
-func (n binNode) eval(R Resolver) float64 {
-	a, b := n.a.eval(R), n.b.eval(R)
+func (n binNode) eval(R Resolver) Value {
+	a, b := mustNum(n.a.eval(R)), mustNum(n.b.eval(R))
 	switch n.op {
 	case "+":
 		return a + b
@@ -107,7 +159,7 @@ func (n binNode) eval(R Resolver) float64 {
 	case "||":
 		return boolf(a != 0 || b != 0)
 	}
-	return math.NaN()
+	panic(fmt.Errorf("unknown operator %q", n.op))
 }
 
 func boolf(b bool) float64 {
@@ -117,15 +169,34 @@ func boolf(b bool) float64 {
 	return 0
 }
 
-var funcs = map[string]func([]float64) float64{
+func reduceMinMax(fn string, arr []Value) Value {
+	if len(arr) == 0 {
+		if fn == "min" {
+			return math.Inf(1)
+		}
+		return math.Inf(-1)
+	}
+	m := mustNum(arr[0])
+	for _, x := range arr[1:] {
+		v := mustNum(x)
+		if fn == "min" {
+			m = math.Min(m, v)
+		} else {
+			m = math.Max(m, v)
+		}
+	}
+	return m
+}
+
+// ── Functions ────────────────────────────────────────────────────────────────
+
+var scalarFuncs = map[string]func([]float64) float64{
 	"abs":   func(a []float64) float64 { return math.Abs(a[0]) },
-	"min":   func(a []float64) float64 { return minSlice(a) },
-	"max":   func(a []float64) float64 { return maxSlice(a) },
 	"sqrt":  func(a []float64) float64 { return math.Sqrt(a[0]) },
 	"floor": func(a []float64) float64 { return math.Floor(a[0]) },
 	"ceil":  func(a []float64) float64 { return math.Ceil(a[0]) },
 	"round": func(a []float64) float64 { return math.Round(a[0]) },
-	"sign":  func(a []float64) float64 { return float64(sign(a[0])) },
+	"sign":  func(a []float64) float64 { return float64(signOf(a[0])) },
 	"pow":   func(a []float64) float64 { return math.Pow(a[0], a[1]) },
 	"log":   func(a []float64) float64 { return math.Log(a[0]) },
 	"exp":   func(a []float64) float64 { return math.Exp(a[0]) },
@@ -133,27 +204,145 @@ var funcs = map[string]func([]float64) float64{
 	"cos":   func(a []float64) float64 { return math.Cos(a[0]) },
 }
 
-func minSlice(a []float64) float64 {
-	if len(a) == 0 {
-		return math.Inf(1)
+var arrFuncs = map[string]func([]Value) Value{
+	"len": func(a []Value) Value { return float64(len(mustArr(a[0]))) },
+	"sum": func(a []Value) Value {
+		s := 0.0
+		for _, x := range mustArr(a[0]) {
+			s += mustNum(x)
 		}
-	m := a[0]
-	for _, x := range a[1:] {
-		m = math.Min(m, x)
+		return s
+	},
+	"mean": func(a []Value) Value {
+		r := mustArr(a[0])
+		if len(r) == 0 {
+			return 0.0
 		}
-	return m
+		s := 0.0
+		for _, x := range r {
+			s += mustNum(x)
+		}
+		return s / float64(len(r))
+	},
+	"slice": func(a []Value) Value {
+		r := mustArr(a[0])
+		s := 0
+		e := len(r)
+		if len(a) > 1 {
+			s = clampIdx(int(mustNum(a[1])), len(r))
+		}
+		if len(a) > 2 {
+			e = clampIdx(int(mustNum(a[2])), len(r))
+		}
+		if s > e {
+			s = e
+		}
+		out := make([]Value, 0, e-s)
+		out = append(out, r[s:e]...)
+		return out
+	},
+	"concat":  func(a []Value) Value { return append(append([]Value{}, mustArr(a[0])...), mustArr(a[1])...) },
+	"reverse": func(a []Value) Value { r := append([]Value{}, mustArr(a[0])...); reverse(r); return r },
+	"sort": func(a []Value) Value {
+		r := append([]Value{}, mustArr(a[0])...)
+		sortNum(r)
+		return r
+	},
+	"scale": func(a []Value) Value {
+		r := mustArr(a[0])
+		k := mustNum(a[1])
+		out := make([]Value, len(r))
+		for i, x := range r {
+			out[i] = mustNum(x) * k
+		}
+		return out
+	},
+	"add": func(a []Value) Value {
+		return zipNum(mustArr(a[0]), mustArr(a[1]), func(x, y float64) float64 { return x + y })
+	},
+	"sub": func(a []Value) Value {
+		return zipNum(mustArr(a[0]), mustArr(a[1]), func(x, y float64) float64 { return x - y })
+	},
+	"push": func(a []Value) Value {
+		return append(append([]Value{}, mustArr(a[0])...), a[1])
+	},
+	"set": func(a []Value) Value {
+		r := append([]Value{}, mustArr(a[0])...)
+		k, err := idxResolve(mustNum(a[1]), len(r))
+		if err != nil {
+			panic(err)
+		}
+		r[k] = a[2]
+		return r
+	},
+	"insert": func(a []Value) Value {
+		r := append([]Value{}, mustArr(a[0])...)
+		k := int(mustNum(a[1]))
+		if k < 0 {
+			k = 0
+		}
+		if k > len(r) {
+			k = len(r)
+		}
+		r = append(r, nil)
+		copy(r[k+1:], r[k:])
+		r[k] = a[2]
+		return r
+	},
+	"remove": func(a []Value) Value {
+		r := append([]Value{}, mustArr(a[0])...)
+		k, err := idxResolve(mustNum(a[1]), len(r))
+		if err != nil {
+			panic(err)
+		}
+		return append(r[:k], r[k+1:]...)
+	},
+	"pop": func(a []Value) Value {
+		r := mustArr(a[0])
+		if len(r) == 0 {
+			return []Value{}
+		}
+		return append([]Value{}, r[:len(r)-1]...)
+	},
+	"shift": func(a []Value) Value {
+		r := mustArr(a[0])
+		if len(r) == 0 {
+			return []Value{}
+		}
+		return append([]Value{}, r[1:]...)
+	},
+	"indexOf": func(a []Value) Value {
+		r := mustArr(a[0])
+		for i, x := range r {
+			if valEq(x, a[1]) {
+				return float64(i)
+			}
+		}
+		return -1.0
+	},
+	"contains": func(a []Value) Value {
+		r := mustArr(a[0])
+		for _, x := range r {
+			if valEq(x, a[1]) {
+				return 1.0
+			}
+		}
+		return 0.0
+	},
+	"fill": func(a []Value) Value {
+		n := int(mustNum(a[0]))
+		if n < 0 {
+			n = 0
+		}
+		out := make([]Value, n)
+		for i := range out {
+			out[i] = a[1]
+		}
+		return out
+	},
 }
-func maxSlice(a []float64) float64 {
-	if len(a) == 0 {
-		return math.Inf(-1)
-	}
-	m := a[0]
-	for _, x := range a[1:] {
-		m = math.Max(m, x)
-	}
-	return m
-}
-func sign(x float64) int {
+
+func signOf(x float64) int {
 	switch {
 	case x > 0:
 		return 1
@@ -164,6 +353,49 @@ func sign(x float64) int {
 	}
 }
 
+// sign is an alias for signOf, kept for backward compatibility with existing tests.
+func sign(x float64) int { return signOf(x) }
+func clampIdx(i, length int) int {
+	if i < 0 {
+		i = length + i
+	}
+	if i < 0 {
+		i = 0
+	}
+	if i > length {
+		i = length
+	}
+	return i
+}
+func reverse(r []Value) {
+	for i, j := 0, len(r)-1; i < j; i, j = i+1, j-1 {
+		r[i], r[j] = r[j], r[i]
+	}
+}
+func sortNum(r []Value) {
+	for i := 1; i < len(r); i++ {
+		for j := i; j > 0 && mustNum(r[j-1]) > mustNum(r[j]); j-- {
+			r[j-1], r[j] = r[j], r[j-1]
+		}
+	}
+}
+func zipNum(x, y []Value, f func(a, b float64) float64) []Value {
+	n := len(x)
+	if len(y) < n {
+		n = len(y)
+	}
+	out := make([]Value, 0, n)
+	for i := 0; i < n; i++ {
+		out = append(out, f(mustNum(x[i]), mustNum(y[i])))
+	}
+	return out
+}
+func valEq(a, b Value) bool {
+	af, aok := a.(float64)
+	bf, bok := b.(float64)
+	return aok && bok && af == bf
+}
+
 // ── Tokenizer ────────────────────────────────────────────────────────────────
 
 type tok struct {
@@ -223,7 +455,7 @@ func tokenize(src string) ([]tok, error) {
 				continue
 			}
 		}
-		if strings.ContainsRune("+-*/%<>!()?:,", c) {
+		if strings.ContainsRune("+-*/%<>!()?:,[]", c) {
 			toks = append(toks, tok{k: string(c)})
 			i++
 			continue
@@ -279,7 +511,7 @@ func parse(src string) (exprNode, error) {
 	return root, nil
 }
 
-func (ps *parser) primary() (exprNode, error) {
+func (ps *parser) atom() (exprNode, error) {
 	t, ok := ps.peek()
 	if !ok {
 		return nil, fmt.Errorf("unexpected end of expression")
@@ -292,6 +524,32 @@ func (ps *parser) primary() (exprNode, error) {
 			return nil, fmt.Errorf("bad number %q", t.v)
 		}
 		return numNode{v: v}, nil
+	case "[":
+		ps.eat("[")
+		var items []exprNode
+		if nx, ok := ps.peek(); ok && nx.k != "]" {
+			a, err := ps.ternary()
+			if err != nil {
+				return nil, err
+			}
+			items = append(items, a)
+			for {
+				nx2, ok := ps.peek()
+				if !ok || nx2.k != "," {
+					break
+				}
+				ps.eat(",")
+				a, err := ps.ternary()
+				if err != nil {
+					return nil, err
+				}
+				items = append(items, a)
+			}
+		}
+		if _, err := ps.eat("]"); err != nil {
+			return nil, err
+		}
+		return arrNode{items: items}, nil
 	case "sig":
 		ps.eat("")
 		idx := strings.IndexByte(t.v, ':')
@@ -333,7 +591,7 @@ func (ps *parser) primary() (exprNode, error) {
 			if _, err := ps.eat(")"); err != nil {
 				return nil, err
 			}
-			if _, ok := funcs[id]; !ok {
+			if !knownFunc(id) {
 				return nil, fmt.Errorf("unknown function %q", id)
 			}
 			return callNode{fn: id, args: args}, nil
@@ -353,6 +611,39 @@ func (ps *parser) primary() (exprNode, error) {
 	return nil, fmt.Errorf("unexpected token %q in expression", t.k)
 }
 
+func knownFunc(id string) bool {
+	if id == "min" || id == "max" {
+		return true
+	}
+	if _, ok := arrFuncs[id]; ok {
+		return true
+	}
+	_, ok := scalarFuncs[id]
+	return ok
+}
+
+func (ps *parser) primary() (exprNode, error) {
+	n, err := ps.atom()
+	if err != nil {
+		return nil, err
+	}
+	for {
+		nx, ok := ps.peek()
+		if !ok || nx.k != "[" {
+			return n, nil
+		}
+		ps.eat("[")
+		i, err := ps.ternary()
+		if err != nil {
+			return nil, err
+		}
+		if _, err := ps.eat("]"); err != nil {
+			return nil, err
+		}
+		n = indexNode{a: n, i: i}
+	}
+}
+
 func (ps *parser) unary() (exprNode, error) {
 	if t, ok := ps.peek(); ok && (t.k == "-" || t.k == "!") {
 		ps.eat("")
@@ -449,8 +740,9 @@ func parseCached(src string) (exprNode, error) {
 	return n, err
 }
 
-// EvalExpr evaluates an expression string, returning NaN on parse/eval failure.
-func EvalExpr(src string, resolve Resolver) float64 {
+// EvalValue evaluates an expression, returning the full Value (number or array).
+// Returns NaN on parse/eval failure.
+func EvalValue(src string, resolve Resolver) Value {
 	n, err := parseCached(src)
 	if err != nil {
 		return math.NaN()
@@ -458,7 +750,7 @@ func EvalExpr(src string, resolve Resolver) float64 {
 	return safeEval(n, resolve)
 }
 
-func safeEval(n exprNode, resolve Resolver) (out float64) {
+func safeEval(n exprNode, resolve Resolver) (out Value) {
 	defer func() {
 		if recover() != nil {
 			out = math.NaN()
@@ -467,14 +759,23 @@ func safeEval(n exprNode, resolve Resolver) (out float64) {
 	return n.eval(resolve)
 }
 
-// EvalBool reports whether the expression evaluates to a nonzero, non-NaN value.
+// EvalExpr evaluates an expression to a scalar; returns NaN on parse/eval
+// failure OR when the result is an array.
+func EvalExpr(src string, resolve Resolver) float64 {
+	v := EvalValue(src, resolve)
+	if f, ok := v.(float64); ok {
+		return f
+	}
+	return math.NaN()
+}
+
+// EvalBool reports whether the expression evaluates to a nonzero, non-NaN scalar.
 func EvalBool(src string, resolve Resolver) bool {
 	v := EvalExpr(src, resolve)
 	return !math.IsNaN(v) && v != 0
 }
 
-// CollectRefs returns every signal/local reference an expression reads, for
-// subscription. Returns nil for an unparseable expression.
+// CollectRefs returns every signal/local reference an expression reads.
 func CollectRefs(src string) []RefLite {
 	root, err := parseCached(src)
 	if err != nil {
@@ -496,6 +797,13 @@ func CollectRefs(src string) []RefLite {
 			add(t.ds, t.name)
 		case varNode:
 			add("local", t.name)
+		case arrNode:
+			for _, it := range t.items {
+				walk(it)
+			}
+		case indexNode:
+			walk(t.a)
+			walk(t.i)
 		case unNode:
 			walk(t.a)
 		case binNode:

internal/controllogic/expr_test.go

@@ -2,11 +2,12 @@ package controllogic
 
 import (
 	"math"
+	"reflect"
 	"testing"
 )
 
 func TestEvalExpr(t *testing.T) {
-	resolve := func(ds, name string) float64 {
+	resolve := func(ds, name string) Value { // shim: was float64 (Task 4 removes)
 		switch {
 		case ds == "stub" && name == "x":
 			return 10
@@ -45,7 +46,7 @@ func TestEvalExpr(t *testing.T) {
 }
 
 func TestEvalExprErrors(t *testing.T) {
-	r := func(ds, name string) float64 { return 0 }
+	r := func(ds, name string) Value { return 0 } // shim: was float64 (Task 4 removes)
 	for _, bad := range []string{"1 +", "(1", "1 2", "{unterminated"} {
 		if v := EvalExpr(bad, r); !math.IsNaN(v) {
 			t.Errorf("EvalExpr(%q) = %v, want NaN", bad, v)
@@ -84,3 +85,72 @@ func TestEpicsRefSplitFirstColon(t *testing.T) {
 		t.Errorf("got %+v, want epics / SR:BPM:01:X", refs)
 	}
 }
+
+// ── New tests for value-polymorphic evaluator ─────────────────────────────────
+
+func numResolver(vals map[string]Value) Resolver {
+	return func(ds, name string) Value {
+		if v, ok := vals[ds+":"+name]; ok {
+			return v
+		}
+		return math.NaN()
+	}
+}
+
+func TestEvalValueScalar(t *testing.T) {
+	R := numResolver(nil)
+	if got := EvalExpr("2 + 3 * 4", R); got != 14 {
+		t.Fatalf("scalar = %v", got)
+	}
+	if !EvalBool("1 < 2 && 3 >= 3", R) {
+		t.Fatal("bool expr should be true")
+	}
+}
+
+func TestEvalValueArrayLiteralAndIndex(t *testing.T) {
+	R := numResolver(nil)
+	got := EvalValue("[1, 2, 3]", R)
+	if !reflect.DeepEqual(got, []Value{1.0, 2.0, 3.0}) {
+		t.Fatalf("array literal = %#v", got)
+	}
+	if v := EvalExpr("[10,20,30][-1]", R); v != 30 {
+		t.Fatalf("index -1 = %v", v)
+	}
+}
+
+func TestEvalArrayFuncs(t *testing.T) {
+	R := numResolver(map[string]Value{"local:buf": []Value{3.0, 1.0, 2.0}})
+	if v := EvalExpr("len(buf)", R); v != 3 {
+		t.Fatalf("len = %v", v)
+	}
+	if v := EvalExpr("sum(buf)", R); v != 6 {
+		t.Fatalf("sum = %v", v)
+	}
+	if v := EvalExpr("max(buf)", R); v != 3 {
+		t.Fatalf("max(array) = %v", v)
+	}
+	if v := EvalExpr("max(1, 9, 4)", R); v != 9 {
+		t.Fatalf("max(scalars) = %v", v)
+	}
+	got := EvalValue("push(buf, 7)", R)
+	if !reflect.DeepEqual(got, []Value{3.0, 1.0, 2.0, 7.0}) {
+		t.Fatalf("push = %#v", got)
+	}
+}
+
+func TestEvalExprArrayYieldsNaN(t *testing.T) {
+	if v := EvalExpr("[1,2]", numResolver(nil)); !math.IsNaN(v) {
+		t.Fatalf("array via EvalExpr should be NaN, got %v", v)
+	}
+}
+
+func TestCollectRefsArray(t *testing.T) {
+	refs := CollectRefs("[{ds:a}, b[0]] ")
+	keys := map[string]bool{}
+	for _, r := range refs {
+		keys[r.DS+":"+r.Name] = true
+	}
+	if !keys["ds:a"] || !keys["local:b"] {
+		t.Fatalf("refs = %#v", refs)
+	}
+}

internal/controllogic/lua.go

@@ -61,8 +61,10 @@ func (lr *luaRuntime) ensure() error {
 		target := s.CheckString(1)
 		ds, name, ok := parseRef(target)
 		var v float64
-		if ok && lr.curResolve != nil {
-			v = lr.curResolve(ds, name)
+		if ok && lr.curResolve != nil { // shim: Task 6 finalizes lua Value handling
+			if f, fok := lr.curResolve(ds, name).(float64); fok {
+				v = f
+			}
 		}
 		s.Push(lua.LNumber(v))
 		return 1

internal/controllogic/model.go

@@ -72,6 +72,10 @@ type Graph struct {
 	Nodes       []Node      `json:"nodes"`
 	Wires       []Wire      `json:"wires"`
 	Groups      []NodeGroup `json:"groups,omitempty"`
+	// StateVars declares graph-local variables (scalar or array). Live values are
+	// instantiated in memory per generation from these declarations; only the
+	// declarations persist. Mirrors the panel-logic statevars feature.
+	StateVars []StateVar `json:"statevars,omitempty"`
 }
 
 func (n Node) param(key string) string {

internal/controllogic/store_test.go

@@ -0,0 +1,33 @@
+package controllogic
+
+import "testing"
+
+func TestStoreRoundTripStateVars(t *testing.T) {
+	dir := t.TempDir()
+	st, err := NewStore(dir) // NewStore takes the storage DIRECTORY
+	if err != nil {
+		t.Fatal(err)
+	}
+	g := Graph{
+		ID:   "g1",
+		Name: "with-vars",
+		StateVars: []StateVar{
+			{Name: "count", Type: "number", Initial: "0"},
+			{Name: "buf", Type: "array", Initial: "[1,2]", Elem: "number", Sizing: "capped", Capacity: 5},
+		},
+	}
+	if err := st.Save(g); err != nil { // Save returns only error
+		t.Fatal(err)
+	}
+	st2, err := NewStore(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err := st2.Get("g1") // Get returns (Graph, error); ErrNotFound if absent
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got.StateVars) != 2 || got.StateVars[1].Name != "buf" || got.StateVars[1].Capacity != 5 {
+		t.Fatalf("statevars not round-tripped: %#v", got.StateVars)
+	}
+}

internal/controllogic/value.go

@@ -0,0 +1,156 @@
+// Value model for control-logic locals/expressions. A Value is either a scalar
+// (float64; booleans are 1/0) or an array ([]Value). This is the Go port of
+// web/src/lib/arraypolicy.ts (sizing) plus the asNum/asArr/idx narrowing from
+// web/src/lib/expr.ts. Pure, dependency-free.
+package controllogic
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// Value is a scalar (float64) or an array ([]Value).
+type Value = any
+
+// ARRAY_MAX is the global hard cap on dynamic array length (drops oldest).
+const ARRAY_MAX = 1_000_000
+
+// StateVar declares a graph-local variable. Mirrors web/src/lib/types.ts StateVar.
+type StateVar struct {
+	Name     string  `json:"name"`
+	Type     string  `json:"type,omitempty"` // number|bool|string|array (default number)
+	Initial  string  `json:"initial"`        // initial value, stored as a string
+	Unit     string  `json:"unit,omitempty"`
+	Low      float64 `json:"low,omitempty"`
+	High     float64 `json:"high,omitempty"`
+	Elem     string  `json:"elem,omitempty"`     // array-only: number|bool|array
+	Sizing   string  `json:"sizing,omitempty"`   // array-only: dynamic|capped|fixed
+	Capacity int     `json:"capacity,omitempty"` // array-only
+}
+
+func asNum(v Value) (float64, error) {
+	f, ok := v.(float64)
+	if !ok {
+		return 0, fmt.Errorf("expected a number, got an array")
+	}
+	return f, nil
+}
+
+func asArr(v Value) ([]Value, error) {
+	a, ok := v.([]Value)
+	if !ok {
+		return nil, fmt.Errorf("expected an array, got a number")
+	}
+	return a, nil
+}
+
+// idxResolve resolves a possibly-negative index against length; range-checked.
+func idxResolve(i float64, length int) (int, error) {
+	k := int(i) // truncates toward zero, matching Math.trunc
+	if k < 0 {
+		k = length + k
+	}
+	if k < 0 || k >= length {
+		return 0, fmt.Errorf("index %v out of range (len %d)", i, length)
+	}
+	return k, nil
+}
+
+// normalizeValue coerces an arbitrary decoded value (e.g. from JSON: float64,
+// bool, []interface{}) into a canonical Value (float64 leaves, []Value arrays).
+func normalizeValue(v any) Value {
+	switch t := v.(type) {
+	case float64:
+		return t
+	case float32:
+		return float64(t)
+	case int:
+		return float64(t)
+	case int64:
+		return float64(t)
+	case bool:
+		if t {
+			return 1.0
+		}
+		return 0.0
+	case []interface{}:
+		out := make([]Value, len(t))
+		for i, e := range t {
+			out[i] = normalizeValue(e)
+		}
+		return out
+	default:
+		return 0.0
+	}
+}
+
+func zeroFill(n int) []Value {
+	if n < 0 {
+		n = 0
+	}
+	out := make([]Value, n)
+	for i := range out {
+		out[i] = 0.0
+	}
+	return out
+}
+
+// parseInitialArray returns the starting contents of an array local. Mirrors
+// arraypolicy.ts parseInitialArray.
+func parseInitialArray(sv StateVar) []Value {
+	cap := sv.Capacity
+	raw := strings.TrimSpace(sv.Initial)
+	var parsed []Value
+	if raw != "" {
+		var j interface{}
+		if err := json.Unmarshal([]byte(raw), &j); err == nil {
+			if arr, ok := j.([]interface{}); ok {
+				parsed = normalizeValue(arr).([]Value)
+			}
+		}
+	}
+	if sv.Sizing == "fixed" {
+		if parsed == nil {
+			return zeroFill(cap)
+		}
+		out := make([]Value, 0, cap)
+		for i := 0; i < len(parsed) && i < cap; i++ {
+			out = append(out, parsed[i])
+		}
+		for len(out) < cap {
+			out = append(out, 0.0)
+		}
+		return out
+	}
+	if parsed == nil {
+		return []Value{}
+	}
+	return parsed
+}
+
+// applySizing clamps arr to the declared sizing policy. Mirrors arraypolicy.ts.
+func applySizing(arr []Value, sv StateVar) []Value {
+	cap := sv.Capacity
+	switch sv.Sizing {
+	case "fixed":
+		out := make([]Value, 0, cap)
+		for i := 0; i < len(arr) && i < cap; i++ {
+			out = append(out, arr[i])
+		}
+		for len(out) < cap {
+			out = append(out, 0.0)
+		}
+		return out
+	case "capped":
+		if len(arr) > cap {
+			return arr[len(arr)-cap:]
+		}
+		return arr
+	default:
+		if len(arr) > ARRAY_MAX {
+			return arr[len(arr)-ARRAY_MAX:]
+		}
+		return arr
+	}
+}

internal/controllogic/value_test.go

@@ -0,0 +1,67 @@
+package controllogic
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestAsNumAsArr(t *testing.T) {
+	if n, err := asNum(3.0); err != nil || n != 3 {
+		t.Fatalf("asNum(3)=%v,%v", n, err)
+	}
+	if _, err := asNum([]Value{1.0}); err == nil {
+		t.Fatal("asNum(array) should error")
+	}
+	if a, err := asArr([]Value{1.0, 2.0}); err != nil || len(a) != 2 {
+		t.Fatalf("asArr=%v,%v", a, err)
+	}
+	if _, err := asArr(3.0); err == nil {
+		t.Fatal("asArr(number) should error")
+	}
+}
+
+func TestIdxResolve(t *testing.T) {
+	if k, err := idxResolve(-1, 3); err != nil || k != 2 {
+		t.Fatalf("idx(-1,3)=%v,%v", k, err)
+	}
+	if _, err := idxResolve(3, 3); err == nil {
+		t.Fatal("idx(3,3) should be out of range")
+	}
+}
+
+func TestNormalizeValue(t *testing.T) {
+	got := normalizeValue([]interface{}{1.0, true, []interface{}{2.0}})
+	want := []Value{1.0, 1.0, []Value{2.0}}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("normalize=%#v want %#v", got, want)
+	}
+	if normalizeValue(5) != Value(5.0) {
+		t.Fatalf("normalize(int) = %#v", normalizeValue(5))
+	}
+}
+
+func TestParseInitialArray(t *testing.T) {
+	fixed := parseInitialArray(StateVar{Type: "array", Sizing: "fixed", Capacity: 3, Initial: "[1,2]"})
+	if !reflect.DeepEqual(fixed, []Value{1.0, 2.0, 0.0}) {
+		t.Fatalf("fixed init = %#v", fixed)
+	}
+	dyn := parseInitialArray(StateVar{Type: "array", Sizing: "dynamic", Initial: "[5,6,7]"})
+	if !reflect.DeepEqual(dyn, []Value{5.0, 6.0, 7.0}) {
+		t.Fatalf("dynamic init = %#v", dyn)
+	}
+	empty := parseInitialArray(StateVar{Type: "array", Sizing: "dynamic", Initial: ""})
+	if len(empty) != 0 {
+		t.Fatalf("empty init = %#v", empty)
+	}
+}
+
+func TestApplySizing(t *testing.T) {
+	capped := applySizing([]Value{1.0, 2.0, 3.0, 4.0}, StateVar{Sizing: "capped", Capacity: 2})
+	if !reflect.DeepEqual(capped, []Value{3.0, 4.0}) {
+		t.Fatalf("capped = %#v", capped)
+	}
+	fixed := applySizing([]Value{1.0}, StateVar{Sizing: "fixed", Capacity: 3})
+	if !reflect.DeepEqual(fixed, []Value{1.0, 0.0, 0.0}) {
+		t.Fatalf("fixed = %#v", fixed)
+	}
+}

internal/datasource/modbus/client.go

@@ -0,0 +1,216 @@
+package modbus
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+	"net"
+	"sync"
+	"time"
+)
+
+// Modbus function codes.
+const (
+	fcReadCoils         = 0x01
+	fcReadDiscrete      = 0x02
+	fcReadHolding       = 0x03
+	fcReadInput         = 0x04
+	fcWriteSingleCoil   = 0x05
+	fcWriteSingleReg    = 0x06
+	fcWriteMultipleRegs = 0x10
+)
+
+// client is a minimal Modbus TCP master for a single device address. Requests
+// are serialised by mu (Modbus TCP is request/response and the connection is
+// shared by all of a device's polled registers). The connection is dialled
+// lazily and dropped on any I/O error so the next request reconnects.
+type client struct {
+	addr    string
+	timeout time.Duration
+
+	mu   sync.Mutex
+	conn net.Conn
+	txID uint16
+}
+
+func newClient(addr string, timeout time.Duration) *client {
+	if timeout <= 0 {
+		timeout = 3 * time.Second
+	}
+	return &client{addr: addr, timeout: timeout}
+}
+
+func (c *client) close() {
+	c.mu.Lock()
+	c.closeLocked()
+	c.mu.Unlock()
+}
+
+func (c *client) closeLocked() {
+	if c.conn != nil {
+		_ = c.conn.Close()
+		c.conn = nil
+	}
+}
+
+// request sends a PDU to unitID and returns the response PDU (function code +
+// data). It dials on demand and tears the connection down on error.
+func (c *client) request(unitID byte, pdu []byte) ([]byte, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.conn == nil {
+		conn, err := net.DialTimeout("tcp", c.addr, c.timeout)
+		if err != nil {
+			return nil, fmt.Errorf("modbus: dial %s: %w", c.addr, err)
+		}
+		c.conn = conn
+	}
+
+	resp, err := c.transact(unitID, pdu)
+	if err != nil {
+		c.closeLocked()
+		return nil, err
+	}
+	return resp, nil
+}
+
+// transact performs one MBAP-framed exchange. Caller holds mu.
+func (c *client) transact(unitID byte, pdu []byte) ([]byte, error) {
+	c.txID++
+	tx := c.txID
+
+	frame := make([]byte, 7+len(pdu))
+	binary.BigEndian.PutUint16(frame[0:], tx)                 // transaction id
+	binary.BigEndian.PutUint16(frame[2:], 0)                  // protocol id (0 = Modbus)
+	binary.BigEndian.PutUint16(frame[4:], uint16(1+len(pdu))) // length: unit id + PDU
+	frame[6] = unitID
+	copy(frame[7:], pdu)
+
+	_ = c.conn.SetDeadline(time.Now().Add(c.timeout))
+	if _, err := c.conn.Write(frame); err != nil {
+		return nil, fmt.Errorf("modbus: write: %w", err)
+	}
+
+	head := make([]byte, 7)
+	if _, err := io.ReadFull(c.conn, head); err != nil {
+		return nil, fmt.Errorf("modbus: read header: %w", err)
+	}
+	if binary.BigEndian.Uint16(head[0:]) != tx {
+		return nil, fmt.Errorf("modbus: transaction id mismatch")
+	}
+	length := binary.BigEndian.Uint16(head[4:])
+	if length < 2 { // unit id + at least a function code
+		return nil, fmt.Errorf("modbus: short frame length %d", length)
+	}
+	body := make([]byte, length-1) // header already consumed the unit id
+	if _, err := io.ReadFull(c.conn, body); err != nil {
+		return nil, fmt.Errorf("modbus: read body: %w", err)
+	}
+
+	fc := body[0]
+	if fc&0x80 != 0 { // exception response
+		var ex byte
+		if len(body) >= 2 {
+			ex = body[1]
+		}
+		return nil, fmt.Errorf("modbus: exception 0x%02x (%s)", ex, exceptionText(ex))
+	}
+	return body, nil
+}
+
+// readRegisters reads `quantity` 16-bit registers via fc (holding or input).
+func (c *client) readRegisters(unitID, fc byte, addr, quantity uint16) ([]uint16, error) {
+	pdu := []byte{fc, byte(addr >> 8), byte(addr), byte(quantity >> 8), byte(quantity)}
+	resp, err := c.request(unitID, pdu)
+	if err != nil {
+		return nil, err
+	}
+	if len(resp) < 2 {
+		return nil, fmt.Errorf("modbus: short register response")
+	}
+	byteCount := int(resp[1])
+	if byteCount != int(quantity)*2 || len(resp) < 2+byteCount {
+		return nil, fmt.Errorf("modbus: register byte count %d (want %d)", byteCount, quantity*2)
+	}
+	regs := make([]uint16, quantity)
+	for i := range regs {
+		regs[i] = binary.BigEndian.Uint16(resp[2+i*2:])
+	}
+	return regs, nil
+}
+
+// readBits reads `quantity` bits via fc (coils or discrete inputs).
+func (c *client) readBits(unitID, fc byte, addr, quantity uint16) ([]bool, error) {
+	pdu := []byte{fc, byte(addr >> 8), byte(addr), byte(quantity >> 8), byte(quantity)}
+	resp, err := c.request(unitID, pdu)
+	if err != nil {
+		return nil, err
+	}
+	if len(resp) < 2 {
+		return nil, fmt.Errorf("modbus: short bit response")
+	}
+	byteCount := int(resp[1])
+	if len(resp) < 2+byteCount {
+		return nil, fmt.Errorf("modbus: bit byte count %d exceeds frame", byteCount)
+	}
+	bits := make([]bool, quantity)
+	for i := range bits {
+		idx := 2 + i/8
+		if idx >= len(resp) {
+			break
+		}
+		bits[i] = resp[idx]&(1<<(uint(i)%8)) != 0
+	}
+	return bits, nil
+}
+
+func (c *client) writeSingleRegister(unitID byte, addr, value uint16) error {
+	pdu := []byte{fcWriteSingleReg, byte(addr >> 8), byte(addr), byte(value >> 8), byte(value)}
+	_, err := c.request(unitID, pdu)
+	return err
+}
+
+func (c *client) writeMultipleRegisters(unitID byte, addr uint16, values []uint16) error {
+	pdu := make([]byte, 6+len(values)*2)
+	pdu[0] = fcWriteMultipleRegs
+	binary.BigEndian.PutUint16(pdu[1:], addr)
+	binary.BigEndian.PutUint16(pdu[3:], uint16(len(values)))
+	pdu[5] = byte(len(values) * 2)
+	for i, v := range values {
+		binary.BigEndian.PutUint16(pdu[6+i*2:], v)
+	}
+	_, err := c.request(unitID, pdu)
+	return err
+}
+
+func (c *client) writeSingleCoil(unitID byte, addr uint16, on bool) error {
+	var v uint16
+	if on {
+		v = 0xFF00
+	}
+	pdu := []byte{fcWriteSingleCoil, byte(addr >> 8), byte(addr), byte(v >> 8), byte(v)}
+	_, err := c.request(unitID, pdu)
+	return err
+}
+
+func exceptionText(code byte) string {
+	switch code {
+	case 0x01:
+		return "illegal function"
+	case 0x02:
+		return "illegal data address"
+	case 0x03:
+		return "illegal data value"
+	case 0x04:
+		return "server device failure"
+	case 0x05:
+		return "acknowledge"
+	case 0x06:
+		return "server device busy"
+	case 0x0B:
+		return "gateway target failed to respond"
+	default:
+		return "unknown"
+	}
+}

internal/datasource/modbus/config.go

@@ -0,0 +1,152 @@
+package modbus
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+// Config is the [datasource.modbus] section. Devices share no connection state;
+// each is polled independently over its own TCP socket.
+type Config struct {
+	Enabled bool `toml:"enabled"`
+	// PollIntervalMs is the default polling period for every register that does
+	// not override it. Zero → 1000 ms.
+	PollIntervalMs int      `toml:"poll_interval_ms"`
+	Devices        []Device `toml:"devices"`
+}
+
+// Device is one Modbus TCP slave. Address is "host:port" (default port 502 is
+// appended if absent). UnitID is the Modbus unit/slave identifier (0–255).
+type Device struct {
+	Name      string     `toml:"name"`
+	Address   string     `toml:"address"`
+	UnitID    uint8      `toml:"unit_id"`
+	TimeoutMs int        `toml:"timeout_ms"`
+	Registers []Register `toml:"registers"`
+}
+
+// Register describes one logical signal mapped onto a Modbus address.
+//
+//   - Kind selects the address space / function code:
+//     "holding" (FC03/06/10), "input" (FC04, read-only),
+//     "coil" (FC01/05, bool), "discrete" (FC02, read-only bool).
+//   - Encoding selects how holding/input words are decoded:
+//     "uint16", "int16", "uint32", "int32", "float32", "float64".
+//     Ignored for coil/discrete (always bool).
+//   - WordOrder is "big" (default, high word first) or "little" for the
+//     multi-word encodings.
+//   - Scale/Offset transform the raw numeric value: value*Scale + Offset.
+//     Scale 0 is treated as 1.
+type Register struct {
+	Name        string  `toml:"name"`
+	Kind        string  `toml:"kind"`
+	Address     uint16  `toml:"address"`
+	Encoding    string  `toml:"encoding"`
+	WordOrder   string  `toml:"word_order"`
+	Unit        string  `toml:"unit"`
+	Scale       float64 `toml:"scale"`
+	Offset      float64 `toml:"offset"`
+	Min         float64 `toml:"min"`
+	Max         float64 `toml:"max"`
+	Writable    bool    `toml:"writable"`
+	Description string  `toml:"description"`
+}
+
+// register kinds.
+const (
+	kindHolding  = "holding"
+	kindInput    = "input"
+	kindCoil     = "coil"
+	kindDiscrete = "discrete"
+)
+
+// isBool reports whether the register addresses a single-bit space.
+func (r Register) isBool() bool {
+	return r.kind() == kindCoil || r.kind() == kindDiscrete
+}
+
+func (r Register) kind() string {
+	if r.Kind == "" {
+		return kindHolding
+	}
+	return strings.ToLower(r.Kind)
+}
+
+func (r Register) encoding() string {
+	if r.Encoding == "" {
+		return "uint16"
+	}
+	return strings.ToLower(r.Encoding)
+}
+
+func (r Register) littleWordOrder() bool {
+	return strings.ToLower(r.WordOrder) == "little"
+}
+
+func (r Register) scale() float64 {
+	if r.Scale == 0 {
+		return 1
+	}
+	return r.Scale
+}
+
+// wordCount returns the number of 16-bit registers the encoding occupies.
+func (r Register) wordCount() (int, error) {
+	switch r.encoding() {
+	case "uint16", "int16":
+		return 1, nil
+	case "uint32", "int32", "float32":
+		return 2, nil
+	case "float64":
+		return 4, nil
+	default:
+		return 0, fmt.Errorf("modbus: unknown encoding %q", r.Encoding)
+	}
+}
+
+// dataType maps the register to a datasource value type.
+func (r Register) dataType() datasource.DataType {
+	if r.isBool() {
+		return datasource.TypeBool
+	}
+	// Integer encodings with no fractional scaling stay integers; anything
+	// scaled, offset, or float-encoded becomes a float64.
+	switch r.encoding() {
+	case "float32", "float64":
+		return datasource.TypeFloat64
+	default:
+		if r.scale() == 1 && r.Offset == 0 {
+			return datasource.TypeInt64
+		}
+		return datasource.TypeFloat64
+	}
+}
+
+// writable reports whether writes are permitted. Input registers and discrete
+// inputs are read-only regardless of the Writable flag.
+func (r Register) writable() bool {
+	switch r.kind() {
+	case kindInput, kindDiscrete:
+		return false
+	default:
+		return r.Writable
+	}
+}
+
+// metadata builds the datasource.Metadata for this register under signal name
+// "device:register".
+func (r Register) metadata(device string) datasource.Metadata {
+	return datasource.Metadata{
+		Name:        device + ":" + r.Name,
+		Type:        r.dataType(),
+		Unit:        r.Unit,
+		Description: r.Description,
+		DisplayLow:  r.Min,
+		DisplayHigh: r.Max,
+		DriveLow:    r.Min,
+		DriveHigh:   r.Max,
+		Writable:    r.writable(),
+	}
+}

internal/datasource/modbus/decode.go

@@ -0,0 +1,89 @@
+package modbus
+
+import (
+	"fmt"
+	"math"
+)
+
+// orderWords returns the registers in big-word-first order, reversing them when
+// the register declares little word order. The slice is copied so the caller's
+// data is left untouched.
+func (r Register) orderWords(words []uint16) []uint16 {
+	if !r.littleWordOrder() {
+		return words
+	}
+	out := make([]uint16, len(words))
+	for i, w := range words {
+		out[len(words)-1-i] = w
+	}
+	return out
+}
+
+// decode converts the raw registers into the register's numeric value and
+// applies scale/offset. The result type is int64 or float64 per dataType.
+func (r Register) decode(words []uint16) (any, error) {
+	w := r.orderWords(words)
+	var raw float64
+	var rawInt int64
+	switch r.encoding() {
+	case "uint16":
+		rawInt = int64(w[0])
+		raw = float64(w[0])
+	case "int16":
+		rawInt = int64(int16(w[0]))
+		raw = float64(int16(w[0]))
+	case "uint32":
+		u := uint32(w[0])<<16 | uint32(w[1])
+		rawInt = int64(u)
+		raw = float64(u)
+	case "int32":
+		u := uint32(w[0])<<16 | uint32(w[1])
+		rawInt = int64(int32(u))
+		raw = float64(int32(u))
+	case "float32":
+		u := uint32(w[0])<<16 | uint32(w[1])
+		raw = float64(math.Float32frombits(u))
+	case "float64":
+		u := uint64(w[0])<<48 | uint64(w[1])<<32 | uint64(w[2])<<16 | uint64(w[3])
+		raw = math.Float64frombits(u)
+	default:
+		return nil, fmt.Errorf("modbus: unknown encoding %q", r.Encoding)
+	}
+
+	// Integer fast-path: no scaling/offset, integer encoding.
+	if r.scale() == 1 && r.Offset == 0 {
+		switch r.encoding() {
+		case "uint16", "int16", "uint32", "int32":
+			return rawInt, nil
+		}
+	}
+	return raw*r.scale() + r.Offset, nil
+}
+
+// encode converts a value destined for a Write back into raw registers,
+// inverting scale/offset. Only the holding-register encodings are writable.
+func (r Register) encode(value float64) ([]uint16, error) {
+	v := (value - r.Offset) / r.scale()
+	var words []uint16
+	switch r.encoding() {
+	case "uint16":
+		words = []uint16{uint16(int64(math.Round(v)))}
+	case "int16":
+		words = []uint16{uint16(int16(int64(math.Round(v))))}
+	case "uint32":
+		u := uint32(int64(math.Round(v)))
+		words = []uint16{uint16(u >> 16), uint16(u)}
+	case "int32":
+		u := uint32(int32(int64(math.Round(v))))
+		words = []uint16{uint16(u >> 16), uint16(u)}
+	case "float32":
+		u := math.Float32bits(float32(v))
+		words = []uint16{uint16(u >> 16), uint16(u)}
+	case "float64":
+		u := math.Float64bits(v)
+		words = []uint16{uint16(u >> 48), uint16(u >> 32), uint16(u >> 16), uint16(u)}
+	default:
+		return nil, fmt.Errorf("modbus: unknown encoding %q", r.Encoding)
+	}
+	return r.orderWords(words), nil
+}

internal/datasource/modbus/decode_test.go

@@ -0,0 +1,115 @@
+package modbus
+
+import (
+	"math"
+	"testing"
+
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+func TestDecodeEncodings(t *testing.T) {
+	cases := []struct {
+		name  string
+		reg   Register
+		words []uint16
+		want  any
+	}{
+		{"uint16", Register{Encoding: "uint16"}, []uint16{42}, int64(42)},
+		{"int16 neg", Register{Encoding: "int16"}, []uint16{0xFFFF}, int64(-1)},
+		{"uint32", Register{Encoding: "uint32"}, []uint16{0x0001, 0x0000}, int64(65536)},
+		{"int32 neg", Register{Encoding: "int32"}, []uint16{0xFFFF, 0xFFFF}, int64(-1)},
+		{"scaled", Register{Encoding: "int16", Scale: 0.1}, []uint16{235}, 23.5},
+		{"float32", Register{Encoding: "float32"}, f32Words(3.5), 3.5},
+		{"float64", Register{Encoding: "float64"}, f64Words(2.25), 2.25},
+	}
+	for _, tc := range cases {
+		got, err := tc.reg.decode(tc.words)
+		if err != nil {
+			t.Errorf("%s: decode error %v", tc.name, err)
+			continue
+		}
+		switch w := tc.want.(type) {
+		case int64:
+			if got != w {
+				t.Errorf("%s: got %v (%T), want %v", tc.name, got, got, w)
+			}
+		case float64:
+			gf, ok := got.(float64)
+			if !ok || math.Abs(gf-w) > 1e-6 {
+				t.Errorf("%s: got %v (%T), want %v", tc.name, got, got, w)
+			}
+		}
+	}
+}
+
+func TestWordOrder(t *testing.T) {
+	big := Register{Encoding: "uint32", WordOrder: "big"}
+	little := Register{Encoding: "uint32", WordOrder: "little"}
+	words := []uint16{0x0001, 0x0002} // big: 0x00010002, little reverses to 0x00020001
+	gb, _ := big.decode(words)
+	gl, _ := little.decode(words)
+	if gb != int64(0x00010002) {
+		t.Errorf("big = %v, want %d", gb, 0x00010002)
+	}
+	if gl != int64(0x00020001) {
+		t.Errorf("little = %v, want %d", gl, 0x00020001)
+	}
+}
+
+func TestEncodeRoundTrip(t *testing.T) {
+	for _, enc := range []string{"uint16", "int16", "uint32", "int32", "float32", "float64"} {
+		reg := Register{Encoding: enc}
+		words, err := reg.encode(123)
+		if err != nil {
+			t.Fatalf("%s encode: %v", enc, err)
+		}
+		got, err := reg.decode(words)
+		if err != nil {
+			t.Fatalf("%s decode: %v", enc, err)
+		}
+		var f float64
+		switch v := got.(type) {
+		case int64:
+			f = float64(v)
+		case float64:
+			f = v
+		}
+		if math.Abs(f-123) > 1e-3 {
+			t.Errorf("%s round-trip = %v, want 123", enc, f)
+		}
+	}
+}
+
+func TestDataTypeAndWritable(t *testing.T) {
+	if got := (Register{Kind: "coil"}).dataType(); got != datasource.TypeBool {
+		t.Errorf("coil type = %v, want bool", got)
+	}
+	if got := (Register{Encoding: "float32"}).dataType(); got != datasource.TypeFloat64 {
+		t.Errorf("float type = %v, want float64", got)
+	}
+	if got := (Register{Encoding: "uint16", Scale: 0.5}).dataType(); got != datasource.TypeFloat64 {
+		t.Errorf("scaled int type = %v, want float64", got)
+	}
+	if got := (Register{Encoding: "uint16"}).dataType(); got != datasource.TypeInt64 {
+		t.Errorf("plain int type = %v, want int64", got)
+	}
+	if (Register{Kind: "input", Writable: true}).writable() {
+		t.Error("input register must be read-only")
+	}
+	if (Register{Kind: "discrete", Writable: true}).writable() {
+		t.Error("discrete input must be read-only")
+	}
+	if !(Register{Kind: "holding", Writable: true}).writable() {
+		t.Error("writable holding should be writable")
+	}
+}
+
+func f32Words(v float32) []uint16 {
+	u := math.Float32bits(v)
+	return []uint16{uint16(u >> 16), uint16(u)}
+}
+
+func f64Words(v float64) []uint16 {
+	u := math.Float64bits(v)
+	return []uint16{uint16(u >> 48), uint16(u >> 32), uint16(u >> 16), uint16(u)}
+}

internal/datasource/modbus/modbus.go

@@ -0,0 +1,258 @@
+// Package modbus implements a Modbus TCP data source. Each configured device is
+// polled over its own TCP connection; registers are exposed as signals named
+// "device:register". Reads use the holding/input/coil/discrete function codes;
+// writable holding registers and coils accept Write.
+package modbus
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+const defaultPollInterval = time.Second
+
+// deviceClient bundles a parsed device with its wire client and register lookup.
+type deviceClient struct {
+	dev    Device
+	cli    *client
+	byName map[string]Register
+}
+
+// Modbus is a datasource.DataSource backed by one or more Modbus TCP devices.
+type Modbus struct {
+	pollInterval time.Duration
+	devices      map[string]*deviceClient // device name → client
+	signals      map[string]signalRef     // "device:register" → ref
+}
+
+type signalRef struct {
+	device string
+	reg    Register
+}
+
+// New builds a Modbus source from config. It does not dial; connections are
+// established lazily on first poll/write.
+func New(cfg Config) (*Modbus, error) {
+	poll := time.Duration(cfg.PollIntervalMs) * time.Millisecond
+	if poll <= 0 {
+		poll = defaultPollInterval
+	}
+	m := &Modbus{
+		pollInterval: poll,
+		devices:      make(map[string]*deviceClient),
+		signals:      make(map[string]signalRef),
+	}
+	for _, dev := range cfg.Devices {
+		if dev.Name == "" || dev.Address == "" {
+			return nil, fmt.Errorf("modbus: device needs name and address")
+		}
+		if _, dup := m.devices[dev.Name]; dup {
+			return nil, fmt.Errorf("modbus: duplicate device %q", dev.Name)
+		}
+		addr := dev.Address
+		if !strings.Contains(addr, ":") {
+			addr += ":502"
+		}
+		dc := &deviceClient{
+			dev:    dev,
+			cli:    newClient(addr, time.Duration(dev.TimeoutMs)*time.Millisecond),
+			byName: make(map[string]Register),
+		}
+		for _, reg := range dev.Registers {
+			if reg.Name == "" {
+				return nil, fmt.Errorf("modbus: device %q has a register with no name", dev.Name)
+			}
+			if _, err := reg.wordCount(); !reg.isBool() && err != nil {
+				return nil, err
+			}
+			if _, dup := dc.byName[reg.Name]; dup {
+				return nil, fmt.Errorf("modbus: device %q duplicate register %q", dev.Name, reg.Name)
+			}
+			dc.byName[reg.Name] = reg
+			m.signals[dev.Name+":"+reg.Name] = signalRef{device: dev.Name, reg: reg}
+		}
+		m.devices[dev.Name] = dc
+	}
+	return m, nil
+}
+
+// Name implements datasource.DataSource.
+func (m *Modbus) Name() string { return "modbus" }
+
+// Connect is a no-op; TCP connections are dialled lazily per device.
+func (m *Modbus) Connect(_ context.Context) error { return nil }
+
+// ListSignals returns metadata for every configured register.
+func (m *Modbus) ListSignals(_ context.Context) ([]datasource.Metadata, error) {
+	out := make([]datasource.Metadata, 0, len(m.signals))
+	for _, ref := range m.signals {
+		out = append(out, ref.reg.metadata(ref.device))
+	}
+	return out, nil
+}
+
+// GetMetadata returns metadata for one signal.
+func (m *Modbus) GetMetadata(_ context.Context, signal string) (datasource.Metadata, error) {
+	ref, ok := m.signals[signal]
+	if !ok {
+		return datasource.Metadata{}, datasource.ErrNotFound
+	}
+	return ref.reg.metadata(ref.device), nil
+}
+
+// readSignal performs one synchronous read of a register's current value.
+func (m *Modbus) readSignal(ref signalRef) (datasource.Value, error) {
+	dc := m.devices[ref.device]
+	reg := ref.reg
+	now := time.Now()
+
+	if reg.isBool() {
+		fc := byte(fcReadCoils)
+		if reg.kind() == kindDiscrete {
+			fc = fcReadDiscrete
+		}
+		bits, err := dc.cli.readBits(dc.dev.UnitID, fc, reg.Address, 1)
+		if err != nil {
+			return datasource.Value{}, err
+		}
+		return datasource.Value{Timestamp: now, Data: bits[0], Quality: datasource.QualityGood}, nil
+	}
+
+	count, err := reg.wordCount()
+	if err != nil {
+		return datasource.Value{}, err
+	}
+	fc := byte(fcReadHolding)
+	if reg.kind() == kindInput {
+		fc = fcReadInput
+	}
+	words, err := dc.cli.readRegisters(dc.dev.UnitID, fc, reg.Address, uint16(count))
+	if err != nil {
+		return datasource.Value{}, err
+	}
+	data, err := reg.decode(words)
+	if err != nil {
+		return datasource.Value{}, err
+	}
+	return datasource.Value{Timestamp: now, Data: data, Quality: datasource.QualityGood}, nil
+}
+
+// Subscribe polls the register at the configured interval and pushes values
+// into ch. On a read error a QualityBad value is emitted and polling continues.
+func (m *Modbus) Subscribe(ctx context.Context, signal string, ch chan<- datasource.Value) (datasource.CancelFunc, error) {
+	ref, ok := m.signals[signal]
+	if !ok {
+		return nil, datasource.ErrNotFound
+	}
+
+	ctx, cancel := context.WithCancel(ctx)
+	go func() {
+		ticker := time.NewTicker(m.pollInterval)
+		defer ticker.Stop()
+		emit := func() {
+			v, err := m.readSignal(ref)
+			if err != nil {
+				v = datasource.Value{Timestamp: time.Now(), Quality: datasource.QualityBad}
+			}
+			select {
+			case ch <- v:
+			case <-ctx.Done():
+			}
+		}
+		emit() // first reading without waiting a full interval
+		for {
+			select {
+			case <-ticker.C:
+				emit()
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+	return datasource.CancelFunc(cancel), nil
+}
+
+// Write sets a writable holding register or coil.
+func (m *Modbus) Write(_ context.Context, signal string, value any) error {
+	ref, ok := m.signals[signal]
+	if !ok {
+		return datasource.ErrNotFound
+	}
+	reg := ref.reg
+	if !reg.writable() {
+		return datasource.ErrNotWritable
+	}
+	dc := m.devices[ref.device]
+
+	if reg.isBool() {
+		on, err := toBool(value)
+		if err != nil {
+			return err
+		}
+		return dc.cli.writeSingleCoil(dc.dev.UnitID, reg.Address, on)
+	}
+
+	f, err := toFloat(value)
+	if err != nil {
+		return err
+	}
+	words, err := reg.encode(f)
+	if err != nil {
+		return err
+	}
+	if len(words) == 1 {
+		return dc.cli.writeSingleRegister(dc.dev.UnitID, reg.Address, words[0])
+	}
+	return dc.cli.writeMultipleRegisters(dc.dev.UnitID, reg.Address, words)
+}
+
+// History is unavailable for Modbus devices.
+func (m *Modbus) History(_ context.Context, _ string, _, _ time.Time, _ int) ([]datasource.Value, error) {
+	return nil, datasource.ErrHistoryUnavailable
+}
+
+// Close tears down every device connection.
+func (m *Modbus) Close() {
+	for _, dc := range m.devices {
+		dc.cli.close()
+	}
+}
+
+func toFloat(v any) (float64, error) {
+	switch x := v.(type) {
+	case float64:
+		return x, nil
+	case float32:
+		return float64(x), nil
+	case int:
+		return float64(x), nil
+	case int64:
+		return float64(x), nil
+	case bool:
+		if x {
+			return 1, nil
+		}
+		return 0, nil
+	default:
+		return 0, fmt.Errorf("modbus: cannot write value of type %T", v)
+	}
+}
+
+func toBool(v any) (bool, error) {
+	switch x := v.(type) {
+	case bool:
+		return x, nil
+	case float64:
+		return x != 0, nil
+	case int:
+		return x != 0, nil
+	case int64:
+		return x != 0, nil
+	default:
+		return false, fmt.Errorf("modbus: cannot write bool value of type %T", v)
+	}
+}

internal/datasource/modbus/modbus_test.go

@@ -0,0 +1,364 @@
+package modbus
+
+import (
+	"context"
+	"encoding/binary"
+	"io"
+	"net"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+// mockServer is an in-process Modbus TCP slave for tests. It serves a small
+// register/coil store and records writes. Only the function codes exercised by
+// the data source are implemented.
+type mockServer struct {
+	ln net.Listener
+
+	mu        sync.Mutex
+	holding   map[uint16]uint16
+	input     map[uint16]uint16
+	coils     map[uint16]bool
+	discrete  map[uint16]bool
+	lastWrite []uint16 // registers from the most recent write
+}
+
+func newMockServer(t *testing.T) *mockServer {
+	t.Helper()
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	s := &mockServer{
+		ln:       ln,
+		holding:  map[uint16]uint16{},
+		input:    map[uint16]uint16{},
+		coils:    map[uint16]bool{},
+		discrete: map[uint16]bool{},
+	}
+	go s.serve()
+	t.Cleanup(func() { ln.Close() })
+	return s
+}
+
+func (s *mockServer) addr() string { return s.ln.Addr().String() }
+
+func (s *mockServer) serve() {
+	for {
+		conn, err := s.ln.Accept()
+		if err != nil {
+			return
+		}
+		go s.handle(conn)
+	}
+}
+
+func (s *mockServer) handle(conn net.Conn) {
+	defer conn.Close()
+	for {
+		head := make([]byte, 7)
+		if _, err := io.ReadFull(conn, head); err != nil {
+			return
+		}
+		tx := binary.BigEndian.Uint16(head[0:])
+		length := binary.BigEndian.Uint16(head[4:])
+		body := make([]byte, length-1)
+		if _, err := io.ReadFull(conn, body); err != nil {
+			return
+		}
+		resp := s.respond(body)
+		out := make([]byte, 7+len(resp))
+		binary.BigEndian.PutUint16(out[0:], tx)
+		binary.BigEndian.PutUint16(out[2:], 0)
+		binary.BigEndian.PutUint16(out[4:], uint16(1+len(resp)))
+		out[6] = head[6]
+		copy(out[7:], resp)
+		if _, err := conn.Write(out); err != nil {
+			return
+		}
+	}
+}
+
+func (s *mockServer) respond(pdu []byte) []byte {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	fc := pdu[0]
+	switch fc {
+	case fcReadHolding, fcReadInput:
+		addr := binary.BigEndian.Uint16(pdu[1:])
+		qty := binary.BigEndian.Uint16(pdu[3:])
+		out := []byte{fc, byte(qty * 2)}
+		src := s.holding
+		if fc == fcReadInput {
+			src = s.input
+		}
+		for i := uint16(0); i < qty; i++ {
+			out = binary.BigEndian.AppendUint16(out, src[addr+i])
+		}
+		return out
+	case fcReadCoils, fcReadDiscrete:
+		addr := binary.BigEndian.Uint16(pdu[1:])
+		qty := binary.BigEndian.Uint16(pdu[3:])
+		nbytes := (int(qty) + 7) / 8
+		out := []byte{fc, byte(nbytes)}
+		bits := make([]byte, nbytes)
+		src := s.coils
+		if fc == fcReadDiscrete {
+			src = s.discrete
+		}
+		for i := uint16(0); i < qty; i++ {
+			if src[addr+i] {
+				bits[i/8] |= 1 << (i % 8)
+			}
+		}
+		return append(out, bits...)
+	case fcWriteSingleReg:
+		addr := binary.BigEndian.Uint16(pdu[1:])
+		val := binary.BigEndian.Uint16(pdu[3:])
+		s.holding[addr] = val
+		s.lastWrite = []uint16{val}
+		return pdu // echo
+	case fcWriteSingleCoil:
+		addr := binary.BigEndian.Uint16(pdu[1:])
+		s.coils[addr] = binary.BigEndian.Uint16(pdu[3:]) == 0xFF00
+		return pdu
+	case fcWriteMultipleRegs:
+		addr := binary.BigEndian.Uint16(pdu[1:])
+		qty := binary.BigEndian.Uint16(pdu[3:])
+		s.lastWrite = nil
+		for i := uint16(0); i < qty; i++ {
+			v := binary.BigEndian.Uint16(pdu[6+i*2:])
+			s.holding[addr+i] = v
+			s.lastWrite = append(s.lastWrite, v)
+		}
+		return append([]byte{fc}, pdu[1:5]...)
+	default:
+		return []byte{fc | 0x80, 0x01}
+	}
+}
+
+func (s *mockServer) setHolding(addr, val uint16) {
+	s.mu.Lock()
+	s.holding[addr] = val
+	s.mu.Unlock()
+}
+
+func (s *mockServer) setInput(addr, val uint16) {
+	s.mu.Lock()
+	s.input[addr] = val
+	s.mu.Unlock()
+}
+
+func (s *mockServer) setDiscrete(addr uint16, on bool) {
+	s.mu.Lock()
+	s.discrete[addr] = on
+	s.mu.Unlock()
+}
+
+func testConfig(addr string) Config {
+	return Config{
+		Enabled:        true,
+		PollIntervalMs: 20,
+		Devices: []Device{{
+			Name:    "dev",
+			Address: addr,
+			UnitID:  1,
+			Registers: []Register{
+				{Name: "temp", Kind: "holding", Address: 10, Encoding: "int16", Scale: 0.1, Unit: "C", Writable: true},
+				{Name: "count", Kind: "holding", Address: 20, Encoding: "uint16"},
+				{Name: "big", Kind: "input", Address: 30, Encoding: "uint32"},
+				{Name: "flag", Kind: "discrete", Address: 5},
+				{Name: "relay", Kind: "coil", Address: 6, Writable: true},
+				{Name: "sp", Kind: "holding", Address: 40, Encoding: "float32", Writable: true},
+			},
+		}},
+	}
+}
+
+func TestReadRegisters(t *testing.T) {
+	srv := newMockServer(t)
+	srv.setHolding(10, 235) // int16, scale 0.1 → 23.5
+	srv.setHolding(20, 7)
+	srv.setInput(30, 0)
+	srv.setInput(31, 1000) // uint32 big-word-first: low word at 31
+	srv.setDiscrete(5, true)
+
+	m, err := New(testConfig(srv.addr()))
+	if err != nil {
+		t.Fatalf("New: %v", err)
+	}
+	defer m.Close()
+
+	temp, err := m.readSignal(m.signals["dev:temp"])
+	if err != nil {
+		t.Fatalf("read temp: %v", err)
+	}
+	if f, ok := temp.Data.(float64); !ok || f < 23.49 || f > 23.51 {
+		t.Errorf("temp = %v (%T), want 23.5", temp.Data, temp.Data)
+	}
+
+	count, err := m.readSignal(m.signals["dev:count"])
+	if err != nil {
+		t.Fatalf("read count: %v", err)
+	}
+	if v, ok := count.Data.(int64); !ok || v != 7 {
+		t.Errorf("count = %v (%T), want int64 7", count.Data, count.Data)
+	}
+
+	big, err := m.readSignal(m.signals["dev:big"])
+	if err != nil {
+		t.Fatalf("read big: %v", err)
+	}
+	if v, ok := big.Data.(int64); !ok || v != 1000 {
+		t.Errorf("big = %v (%T), want int64 1000", big.Data, big.Data)
+	}
+
+	flag, err := m.readSignal(m.signals["dev:flag"])
+	if err != nil {
+		t.Fatalf("read flag: %v", err)
+	}
+	if b, ok := flag.Data.(bool); !ok || !b {
+		t.Errorf("flag = %v, want true", flag.Data)
+	}
+}
+
+func TestWriteRoundTrip(t *testing.T) {
+	srv := newMockServer(t)
+	m, err := New(testConfig(srv.addr()))
+	if err != nil {
+		t.Fatalf("New: %v", err)
+	}
+	defer m.Close()
+	ctx := context.Background()
+
+	// Scaled int16: writing 23.5 with scale 0.1 should store raw 235.
+	if err := m.Write(ctx, "dev:temp", 23.5); err != nil {
+		t.Fatalf("write temp: %v", err)
+	}
+	srv.mu.Lock()
+	raw := srv.holding[10]
+	srv.mu.Unlock()
+	if raw != 235 {
+		t.Errorf("holding[10] = %d, want 235", raw)
+	}
+
+	// Coil write.
+	if err := m.Write(ctx, "dev:relay", true); err != nil {
+		t.Fatalf("write relay: %v", err)
+	}
+	srv.mu.Lock()
+	on := srv.coils[6]
+	srv.mu.Unlock()
+	if !on {
+		t.Error("coil 6 not set")
+	}
+
+	// float32 multi-register write.
+	if err := m.Write(ctx, "dev:sp", 12.5); err != nil {
+		t.Fatalf("write sp: %v", err)
+	}
+	got, err := m.readSignal(m.signals["dev:sp"])
+	if err != nil {
+		t.Fatalf("read sp: %v", err)
+	}
+	if f, ok := got.Data.(float64); !ok || f < 12.49 || f > 12.51 {
+		t.Errorf("sp = %v, want 12.5", got.Data)
+	}
+}
+
+func TestWriteErrors(t *testing.T) {
+	srv := newMockServer(t)
+	m, _ := New(testConfig(srv.addr()))
+	defer m.Close()
+	ctx := context.Background()
+
+	if err := m.Write(ctx, "dev:missing", 1); err != datasource.ErrNotFound {
+		t.Errorf("missing write err = %v, want ErrNotFound", err)
+	}
+	// Input register is read-only.
+	if err := m.Write(ctx, "dev:big", 1); err != datasource.ErrNotWritable {
+		t.Errorf("input write err = %v, want ErrNotWritable", err)
+	}
+}
+
+func TestSubscribe(t *testing.T) {
+	srv := newMockServer(t)
+	srv.setHolding(20, 42)
+	m, _ := New(testConfig(srv.addr()))
+	defer m.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	ch := make(chan datasource.Value, 4)
+	stop, err := m.Subscribe(ctx, "dev:count", ch)
+	if err != nil {
+		t.Fatalf("subscribe: %v", err)
+	}
+	defer stop()
+
+	select {
+	case v := <-ch:
+		if v.Quality != datasource.QualityGood {
+			t.Errorf("quality = %v, want good", v.Quality)
+		}
+		if iv, ok := v.Data.(int64); !ok || iv != 42 {
+			t.Errorf("first value = %v, want 42", v.Data)
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("timed out waiting for first value")
+	}
+}
+
+func TestSubscribeBadQualityOnError(t *testing.T) {
+	// Point at a closed port so reads fail; expect QualityBad, not a hang.
+	cfg := testConfig("127.0.0.1:1") // port 1: connection refused
+	m, _ := New(cfg)
+	defer m.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	ch := make(chan datasource.Value, 1)
+	stop, err := m.Subscribe(ctx, "dev:count", ch)
+	if err != nil {
+		t.Fatalf("subscribe: %v", err)
+	}
+	defer stop()
+
+	select {
+	case v := <-ch:
+		if v.Quality != datasource.QualityBad {
+			t.Errorf("quality = %v, want bad", v.Quality)
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("timed out")
+	}
+}
+
+func TestNewValidation(t *testing.T) {
+	if _, err := New(Config{Devices: []Device{{Name: "", Address: "x"}}}); err == nil {
+		t.Error("expected error for missing device name")
+	}
+	if _, err := New(Config{Devices: []Device{{Name: "a", Address: "x"}, {Name: "a", Address: "y"}}}); err == nil {
+		t.Error("expected error for duplicate device")
+	}
+	if _, err := New(Config{Devices: []Device{{Name: "a", Address: "x", Registers: []Register{{Name: "r", Encoding: "bogus"}}}}}); err == nil {
+		t.Error("expected error for bad encoding")
+	}
+	if _, err := New(Config{Devices: []Device{{Name: "a", Address: "x", Registers: []Register{{Name: "r"}, {Name: "r"}}}}}); err == nil {
+		t.Error("expected error for duplicate register")
+	}
+}
+
+func TestSubscribeUnknownSignal(t *testing.T) {
+	m, _ := New(testConfig("127.0.0.1:502"))
+	defer m.Close()
+	if _, err := m.Subscribe(context.Background(), "nope", nil); err != datasource.ErrNotFound {
+		t.Errorf("err = %v, want ErrNotFound", err)
+	}
+	if _, err := m.GetMetadata(context.Background(), "nope"); err != datasource.ErrNotFound {
+		t.Errorf("meta err = %v, want ErrNotFound", err)
+	}
+}

internal/datasource/scpi/config.go

@@ -0,0 +1,75 @@
+package scpi
+
+import "github.com/uopi/uopi/internal/datasource"
+
+// Config is the [datasource.scpi] section. Each instrument is polled
+// independently over its own TCP socket.
+type Config struct {
+	Enabled bool `toml:"enabled"`
+	// PollIntervalMs is the default polling period for channels that do not
+	// override it. Zero → 1000 ms.
+	PollIntervalMs int          `toml:"poll_interval_ms"`
+	Instruments    []Instrument `toml:"instruments"`
+}
+
+// Instrument is one SCPI device reachable over a raw TCP socket. Address is
+// "host:port"; the conventional SCPI-raw port 5025 is appended if absent.
+type Instrument struct {
+	Name string `toml:"name"`
+	// Transport selects the link type. "raw" (default) is line-based SCPI over
+	// TCP. Reserved: "vxi11" (not yet implemented).
+	Transport string `toml:"transport"`
+	Address   string `toml:"address"`
+	TimeoutMs int    `toml:"timeout_ms"`
+	// Terminator is appended to every command. Empty → "\n".
+	Terminator string    `toml:"terminator"`
+	Channels   []Channel `toml:"channels"`
+}
+
+// Channel maps a SCPI query/command pair onto a signal named
+// "instrument:channel".
+type Channel struct {
+	Name string `toml:"name"`
+	// Query is the SCPI command whose response is the channel value,
+	// e.g. "MEAS:VOLT?". Required.
+	Query string `toml:"query"`
+	// WriteCmd is a printf-style template used by Write; "%v" is replaced with
+	// the value, e.g. "VOLT %v". Empty → channel is read-only.
+	WriteCmd string `toml:"write_cmd"`
+	// Type is the value type: "float" (default), "string", "int", or "bool".
+	Type           string  `toml:"type"`
+	Unit           string  `toml:"unit"`
+	Min            float64 `toml:"min"`
+	Max            float64 `toml:"max"`
+	PollIntervalMs int     `toml:"poll_interval_ms"`
+	Description    string  `toml:"description"`
+}
+
+func (c Channel) dataType() datasource.DataType {
+	switch c.Type {
+	case "string":
+		return datasource.TypeString
+	case "int":
+		return datasource.TypeInt64
+	case "bool":
+		return datasource.TypeBool
+	default:
+		return datasource.TypeFloat64
+	}
+}
+
+func (c Channel) writable() bool { return c.WriteCmd != "" }
+
+func (c Channel) metadata(instrument string) datasource.Metadata {
+	return datasource.Metadata{
+		Name:        instrument + ":" + c.Name,
+		Type:        c.dataType(),
+		Unit:        c.Unit,
+		Description: c.Description,
+		DisplayLow:  c.Min,
+		DisplayHigh: c.Max,
+		DriveLow:    c.Min,
+		DriveHigh:   c.Max,
+		Writable:    c.writable(),
+	}
+}

internal/datasource/scpi/scpi.go

@@ -0,0 +1,237 @@
+// Package scpi implements a SCPI instrument data source. Each configured
+// instrument is reached over a raw TCP socket (line-based SCPI, the "SCPI raw" /
+// port 5025 convention); a VXI-11 transport is reserved for later. Channels are
+// exposed as signals named "instrument:channel" and polled at a configurable
+// interval. Channels with a write_cmd template accept Write.
+package scpi
+
+import (
+	"context"
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+const defaultPollInterval = time.Second
+
+type instrumentConn struct {
+	inst Instrument
+	tr   transport
+}
+
+// Scpi is a datasource.DataSource backed by one or more SCPI instruments.
+type Scpi struct {
+	pollInterval time.Duration
+	instruments  map[string]*instrumentConn
+	signals      map[string]signalRef // "instrument:channel" → ref
+}
+
+type signalRef struct {
+	instrument string
+	ch         Channel
+}
+
+// New builds a SCPI source from config. It does not dial; connections are
+// established lazily on first poll/write.
+func New(cfg Config) (*Scpi, error) {
+	poll := time.Duration(cfg.PollIntervalMs) * time.Millisecond
+	if poll <= 0 {
+		poll = defaultPollInterval
+	}
+	s := &Scpi{
+		pollInterval: poll,
+		instruments:  make(map[string]*instrumentConn),
+		signals:      make(map[string]signalRef),
+	}
+	for _, inst := range cfg.Instruments {
+		if inst.Name == "" || inst.Address == "" {
+			return nil, fmt.Errorf("scpi: instrument needs name and address")
+		}
+		if _, dup := s.instruments[inst.Name]; dup {
+			return nil, fmt.Errorf("scpi: duplicate instrument %q", inst.Name)
+		}
+		tr, err := newTransport(inst)
+		if err != nil {
+			return nil, err
+		}
+		ic := &instrumentConn{inst: inst, tr: tr}
+		for _, ch := range inst.Channels {
+			if ch.Name == "" || ch.Query == "" {
+				return nil, fmt.Errorf("scpi: instrument %q channel needs name and query", inst.Name)
+			}
+			key := inst.Name + ":" + ch.Name
+			if _, dup := s.signals[key]; dup {
+				return nil, fmt.Errorf("scpi: instrument %q duplicate channel %q", inst.Name, ch.Name)
+			}
+			s.signals[key] = signalRef{instrument: inst.Name, ch: ch}
+		}
+		s.instruments[inst.Name] = ic
+	}
+	return s, nil
+}
+
+// newTransport selects the transport implementation for an instrument.
+func newTransport(inst Instrument) (transport, error) {
+	addr := inst.Address
+	switch strings.ToLower(inst.Transport) {
+	case "", "raw":
+		if !strings.Contains(addr, ":") {
+			addr += ":5025"
+		}
+		return newRawSocket(addr, time.Duration(inst.TimeoutMs)*time.Millisecond, inst.Terminator), nil
+	case "vxi11":
+		return nil, fmt.Errorf("scpi: vxi11 transport not yet implemented")
+	default:
+		return nil, fmt.Errorf("scpi: unknown transport %q", inst.Transport)
+	}
+}
+
+// Name implements datasource.DataSource.
+func (s *Scpi) Name() string { return "scpi" }
+
+// Connect is a no-op; connections are dialled lazily per instrument.
+func (s *Scpi) Connect(_ context.Context) error { return nil }
+
+// ListSignals returns metadata for every configured channel.
+func (s *Scpi) ListSignals(_ context.Context) ([]datasource.Metadata, error) {
+	out := make([]datasource.Metadata, 0, len(s.signals))
+	for _, ref := range s.signals {
+		out = append(out, ref.ch.metadata(ref.instrument))
+	}
+	return out, nil
+}
+
+// GetMetadata returns metadata for one signal.
+func (s *Scpi) GetMetadata(_ context.Context, signal string) (datasource.Metadata, error) {
+	ref, ok := s.signals[signal]
+	if !ok {
+		return datasource.Metadata{}, datasource.ErrNotFound
+	}
+	return ref.ch.metadata(ref.instrument), nil
+}
+
+// readSignal performs one synchronous query of a channel.
+func (s *Scpi) readSignal(ref signalRef) (datasource.Value, error) {
+	ic := s.instruments[ref.instrument]
+	resp, err := ic.tr.query(ref.ch.Query)
+	if err != nil {
+		return datasource.Value{}, err
+	}
+	data, err := parseValue(ref.ch.dataType(), resp)
+	if err != nil {
+		return datasource.Value{}, err
+	}
+	return datasource.Value{Timestamp: time.Now(), Data: data, Quality: datasource.QualityGood}, nil
+}
+
+// Subscribe polls the channel at its configured interval (falling back to the
+// source default) and pushes values into ch. A query error emits QualityBad and
+// polling continues.
+func (s *Scpi) Subscribe(ctx context.Context, signal string, ch chan<- datasource.Value) (datasource.CancelFunc, error) {
+	ref, ok := s.signals[signal]
+	if !ok {
+		return nil, datasource.ErrNotFound
+	}
+	interval := s.pollInterval
+	if ref.ch.PollIntervalMs > 0 {
+		interval = time.Duration(ref.ch.PollIntervalMs) * time.Millisecond
+	}
+
+	ctx, cancel := context.WithCancel(ctx)
+	go func() {
+		ticker := time.NewTicker(interval)
+		defer ticker.Stop()
+		emit := func() {
+			v, err := s.readSignal(ref)
+			if err != nil {
+				v = datasource.Value{Timestamp: time.Now(), Quality: datasource.QualityBad}
+			}
+			select {
+			case ch <- v:
+			case <-ctx.Done():
+			}
+		}
+		emit()
+		for {
+			select {
+			case <-ticker.C:
+				emit()
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+	return datasource.CancelFunc(cancel), nil
+}
+
+// Write sends the channel's write_cmd template with the value substituted.
+func (s *Scpi) Write(_ context.Context, signal string, value any) error {
+	ref, ok := s.signals[signal]
+	if !ok {
+		return datasource.ErrNotFound
+	}
+	if !ref.ch.writable() {
+		return datasource.ErrNotWritable
+	}
+	ic := s.instruments[ref.instrument]
+	cmd := formatWrite(ref.ch.WriteCmd, value)
+	return ic.tr.write(cmd)
+}
+
+// History is unavailable for SCPI instruments.
+func (s *Scpi) History(_ context.Context, _ string, _, _ time.Time, _ int) ([]datasource.Value, error) {
+	return nil, datasource.ErrHistoryUnavailable
+}
+
+// Close tears down every instrument connection.
+func (s *Scpi) Close() {
+	for _, ic := range s.instruments {
+		ic.tr.close()
+	}
+}
+
+// formatWrite substitutes value into the write template. A "%" in the template
+// is treated as a printf verb; otherwise the value is appended after a space.
+func formatWrite(tmpl string, value any) string {
+	if strings.Contains(tmpl, "%") {
+		return fmt.Sprintf(tmpl, value)
+	}
+	return fmt.Sprintf("%s %v", tmpl, value)
+}
+
+// parseValue converts a raw SCPI response string into the channel's data type.
+func parseValue(t datasource.DataType, resp string) (any, error) {
+	resp = strings.TrimSpace(resp)
+	switch t {
+	case datasource.TypeString:
+		return resp, nil
+	case datasource.TypeInt64:
+		// Accept "12", "12.0", or scientific notation by going through float.
+		f, err := strconv.ParseFloat(resp, 64)
+		if err != nil {
+			return nil, fmt.Errorf("scpi: parse int %q: %w", resp, err)
+		}
+		return int64(f), nil
+	case datasource.TypeBool:
+		switch strings.ToUpper(resp) {
+		case "1", "ON", "TRUE":
+			return true, nil
+		case "0", "OFF", "FALSE":
+			return false, nil
+		}
+		f, err := strconv.ParseFloat(resp, 64)
+		if err != nil {
+			return nil, fmt.Errorf("scpi: parse bool %q: %w", resp, err)
+		}
+		return f != 0, nil
+	default:
+		f, err := strconv.ParseFloat(resp, 64)
+		if err != nil {
+			return nil, fmt.Errorf("scpi: parse float %q: %w", resp, err)
+		}
+		return f, nil
+	}
+}

internal/datasource/scpi/scpi_test.go

@@ -0,0 +1,267 @@
+package scpi
+
+import (
+	"bufio"
+	"context"
+	"net"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/uopi/uopi/internal/datasource"
+)
+
+// mockInstrument is an in-process line-based SCPI server. It answers queries
+// from a fixed table and records commands that produce no response (writes).
+type mockInstrument struct {
+	ln net.Listener
+
+	mu      sync.Mutex
+	answers map[string]string // query → response
+	writes  []string
+}
+
+func newMockInstrument(t *testing.T) *mockInstrument {
+	t.Helper()
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	m := &mockInstrument{ln: ln, answers: map[string]string{}}
+	go m.serve()
+	t.Cleanup(func() { ln.Close() })
+	return m
+}
+
+func (m *mockInstrument) addr() string { return m.ln.Addr().String() }
+
+func (m *mockInstrument) setAnswer(q, a string) {
+	m.mu.Lock()
+	m.answers[q] = a
+	m.mu.Unlock()
+}
+
+func (m *mockInstrument) writeLog() []string {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	return append([]string(nil), m.writes...)
+}
+
+func (m *mockInstrument) serve() {
+	for {
+		conn, err := m.ln.Accept()
+		if err != nil {
+			return
+		}
+		go m.handle(conn)
+	}
+}
+
+func (m *mockInstrument) handle(conn net.Conn) {
+	defer conn.Close()
+	br := bufio.NewReader(conn)
+	for {
+		line, err := br.ReadString('\n')
+		if err != nil {
+			return
+		}
+		cmd := strings.TrimRight(line, "\r\n")
+		m.mu.Lock()
+		if strings.HasSuffix(cmd, "?") {
+			resp, ok := m.answers[cmd]
+			if !ok {
+				resp = "0"
+			}
+			m.mu.Unlock()
+			conn.Write([]byte(resp + "\n"))
+			continue
+		}
+		m.writes = append(m.writes, cmd)
+		m.mu.Unlock()
+	}
+}
+
+func testCfg(addr string) Config {
+	return Config{
+		Enabled:        true,
+		PollIntervalMs: 20,
+		Instruments: []Instrument{{
+			Name:    "dmm",
+			Address: addr,
+			Channels: []Channel{
+				{Name: "volt", Query: "MEAS:VOLT?", WriteCmd: "VOLT %v", Type: "float", Unit: "V"},
+				{Name: "id", Query: "*IDN?", Type: "string"},
+				{Name: "n", Query: "COUNT?", Type: "int"},
+				{Name: "out", Query: "OUTP?", WriteCmd: "OUTP", Type: "bool"},
+			},
+		}},
+	}
+}
+
+func TestQueryTypes(t *testing.T) {
+	srv := newMockInstrument(t)
+	srv.setAnswer("MEAS:VOLT?", "12.34")
+	srv.setAnswer("*IDN?", "ACME,DMM,1,2.0")
+	srv.setAnswer("COUNT?", "7")
+	srv.setAnswer("OUTP?", "ON")
+
+	s, err := New(testCfg(srv.addr()))
+	if err != nil {
+		t.Fatalf("New: %v", err)
+	}
+	defer s.Close()
+
+	v, err := s.readSignal(s.signals["dmm:volt"])
+	if err != nil {
+		t.Fatalf("read volt: %v", err)
+	}
+	if f, ok := v.Data.(float64); !ok || f < 12.33 || f > 12.35 {
+		t.Errorf("volt = %v (%T), want 12.34", v.Data, v.Data)
+	}
+
+	id, _ := s.readSignal(s.signals["dmm:id"])
+	if id.Data != "ACME,DMM,1,2.0" {
+		t.Errorf("id = %v", id.Data)
+	}
+
+	n, _ := s.readSignal(s.signals["dmm:n"])
+	if iv, ok := n.Data.(int64); !ok || iv != 7 {
+		t.Errorf("n = %v (%T), want 7", n.Data, n.Data)
+	}
+
+	out, _ := s.readSignal(s.signals["dmm:out"])
+	if b, ok := out.Data.(bool); !ok || !b {
+		t.Errorf("out = %v, want true", out.Data)
+	}
+}
+
+func TestWrite(t *testing.T) {
+	srv := newMockInstrument(t)
+	s, _ := New(testCfg(srv.addr()))
+	defer s.Close()
+	ctx := context.Background()
+
+	if err := s.Write(ctx, "dmm:volt", 3.3); err != nil {
+		t.Fatalf("write volt: %v", err)
+	}
+	// bool write uses a template with no verb → "OUTP <val>".
+	if err := s.Write(ctx, "dmm:out", true); err != nil {
+		t.Fatalf("write out: %v", err)
+	}
+
+	// Give the server a moment to record both writes.
+	deadline := time.Now().Add(time.Second)
+	for time.Now().Before(deadline) {
+		if len(srv.writeLog()) >= 2 {
+			break
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+	got := srv.writeLog()
+	if len(got) != 2 || got[0] != "VOLT 3.3" || got[1] != "OUTP true" {
+		t.Errorf("writes = %v, want [VOLT 3.3, OUTP true]", got)
+	}
+}
+
+func TestWriteErrors(t *testing.T) {
+	srv := newMockInstrument(t)
+	s, _ := New(testCfg(srv.addr()))
+	defer s.Close()
+	ctx := context.Background()
+
+	if err := s.Write(ctx, "dmm:missing", 1); err != datasource.ErrNotFound {
+		t.Errorf("missing = %v, want ErrNotFound", err)
+	}
+	if err := s.Write(ctx, "dmm:id", 1); err != datasource.ErrNotWritable {
+		t.Errorf("read-only = %v, want ErrNotWritable", err)
+	}
+}
+
+func TestSubscribe(t *testing.T) {
+	srv := newMockInstrument(t)
+	srv.setAnswer("MEAS:VOLT?", "5.0")
+	s, _ := New(testCfg(srv.addr()))
+	defer s.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	ch := make(chan datasource.Value, 4)
+	stop, err := s.Subscribe(ctx, "dmm:volt", ch)
+	if err != nil {
+		t.Fatalf("subscribe: %v", err)
+	}
+	defer stop()
+
+	select {
+	case v := <-ch:
+		if v.Quality != datasource.QualityGood {
+			t.Errorf("quality = %v", v.Quality)
+		}
+		if f, ok := v.Data.(float64); !ok || f != 5.0 {
+			t.Errorf("value = %v, want 5.0", v.Data)
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("timed out")
+	}
+}
+
+func TestSubscribeBadQuality(t *testing.T) {
+	cfg := testCfg("127.0.0.1:1") // refused
+	s, _ := New(cfg)
+	defer s.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	ch := make(chan datasource.Value, 1)
+	stop, _ := s.Subscribe(ctx, "dmm:volt", ch)
+	defer stop()
+
+	select {
+	case v := <-ch:
+		if v.Quality != datasource.QualityBad {
+			t.Errorf("quality = %v, want bad", v.Quality)
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("timed out")
+	}
+}
+
+func TestValidation(t *testing.T) {
+	if _, err := New(Config{Instruments: []Instrument{{Name: "", Address: "x"}}}); err == nil {
+		t.Error("want error for missing name")
+	}
+	if _, err := New(Config{Instruments: []Instrument{{Name: "a", Address: "x"}, {Name: "a", Address: "y"}}}); err == nil {
+		t.Error("want error for duplicate instrument")
+	}
+	if _, err := New(Config{Instruments: []Instrument{{Name: "a", Address: "x", Transport: "vxi11"}}}); err == nil {
+		t.Error("want error for unimplemented vxi11 transport")
+	}
+	if _, err := New(Config{Instruments: []Instrument{{Name: "a", Address: "x", Transport: "bogus"}}}); err == nil {
+		t.Error("want error for unknown transport")
+	}
+	if _, err := New(Config{Instruments: []Instrument{{Name: "a", Address: "x", Channels: []Channel{{Name: "c"}}}}}); err == nil {
+		t.Error("want error for channel without query")
+	}
+}
+
+func TestFormatWrite(t *testing.T) {
+	if got := formatWrite("VOLT %v", 3.3); got != "VOLT 3.3" {
+		t.Errorf("verb template = %q", got)
+	}
+	if got := formatWrite("OUTP", true); got != "OUTP true" {
+		t.Errorf("plain template = %q", got)
+	}
+}
+
+func TestParseValue(t *testing.T) {
+	if v, _ := parseValue(datasource.TypeBool, "OFF"); v != false {
+		t.Errorf("OFF = %v, want false", v)
+	}
+	if v, _ := parseValue(datasource.TypeBool, "2.0"); v != true {
+		t.Errorf("2.0 bool = %v, want true", v)
+	}
+	if _, err := parseValue(datasource.TypeFloat64, "notnum"); err == nil {
+		t.Error("want parse error for non-numeric float")
+	}
+}

internal/datasource/scpi/transport.go

@@ -0,0 +1,107 @@
+package scpi
+
+import (
+	"bufio"
+	"fmt"
+	"net"
+	"strings"
+	"sync"
+	"time"
+)
+
+// transport is the request/response channel to an instrument. The raw-socket
+// implementation below speaks line-oriented SCPI over TCP (the common
+// "SCPI raw" / port 5025 convention). The interface is kept narrow so a VXI-11
+// (ONC-RPC) transport can be added later without touching the data source.
+type transport interface {
+	// query sends cmd and returns the instrument's single-line response.
+	query(cmd string) (string, error)
+	// write sends cmd and does not wait for a response.
+	write(cmd string) error
+	close()
+}
+
+// rawSocket is a line-based SCPI transport over a single TCP connection. The
+// connection is dialled lazily and dropped on any I/O error so the next call
+// reconnects. Calls are serialised by mu because SCPI is request/response.
+type rawSocket struct {
+	addr       string
+	timeout    time.Duration
+	terminator string
+
+	mu   sync.Mutex
+	conn net.Conn
+	br   *bufio.Reader
+}
+
+func newRawSocket(addr string, timeout time.Duration, terminator string) *rawSocket {
+	if timeout <= 0 {
+		timeout = 3 * time.Second
+	}
+	if terminator == "" {
+		terminator = "\n"
+	}
+	return &rawSocket{addr: addr, timeout: timeout, terminator: terminator}
+}
+
+func (s *rawSocket) dialLocked() error {
+	if s.conn != nil {
+		return nil
+	}
+	conn, err := net.DialTimeout("tcp", s.addr, s.timeout)
+	if err != nil {
+		return fmt.Errorf("scpi: dial %s: %w", s.addr, err)
+	}
+	s.conn = conn
+	s.br = bufio.NewReader(conn)
+	return nil
+}
+
+func (s *rawSocket) closeLocked() {
+	if s.conn != nil {
+		_ = s.conn.Close()
+		s.conn = nil
+		s.br = nil
+	}
+}
+
+func (s *rawSocket) close() {
+	s.mu.Lock()
+	s.closeLocked()
+	s.mu.Unlock()
+}
+
+func (s *rawSocket) sendLocked(cmd string) error {
+	_ = s.conn.SetDeadline(time.Now().Add(s.timeout))
+	if _, err := s.conn.Write([]byte(cmd + s.terminator)); err != nil {
+		s.closeLocked()
+		return fmt.Errorf("scpi: write: %w", err)
+	}
+	return nil
+}
+
+func (s *rawSocket) write(cmd string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if err := s.dialLocked(); err != nil {
+		return err
+	}
+	return s.sendLocked(cmd)
+}
+
+func (s *rawSocket) query(cmd string) (string, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if err := s.dialLocked(); err != nil {
+		return "", err
+	}
+	if err := s.sendLocked(cmd); err != nil {
+		return "", err
+	}
+	line, err := s.br.ReadString('\n')
+	if err != nil {
+		s.closeLocked()
+		return "", fmt.Errorf("scpi: read: %w", err)
+	}
+	return strings.TrimRight(line, "\r\n"), nil
+}

uopi.example.toml

@@ -129,3 +129,54 @@ auto_sync_filter   = ""   # e.g. area=StorageRing or tags=production
 
 [datasource.synthetic]
 enabled = true
+
+# Modbus TCP. Each device is polled over its own connection; registers become
+# signals named "device:register". Disabled unless enabled = true and at least
+# one device is declared.
+[datasource.modbus]
+enabled          = false
+poll_interval_ms = 1000   # default poll period for every register
+
+# [[datasource.modbus.devices]]
+# name       = "plc1"
+# address    = "192.168.1.50:502"   # ":502" appended if no port given
+# unit_id    = 1
+# timeout_ms = 3000
+#
+#   [[datasource.modbus.devices.registers]]
+#   name        = "temperature"
+#   kind        = "holding"   # holding | input | coil | discrete
+#   address     = 100
+#   encoding    = "int16"     # uint16|int16|uint32|int32|float32|float64
+#   word_order  = "big"       # big (default) | little, for multi-word encodings
+#   unit        = "C"
+#   scale       = 0.1         # value = raw*scale + offset (scale 0 → 1)
+#   offset      = 0.0
+#   min         = -50
+#   max         = 200
+#   writable    = false       # input/discrete are always read-only
+#   description = "Process temperature"
+
+# SCPI instruments over raw TCP sockets (line-based "SCPI raw", port 5025).
+# Channels become signals named "instrument:channel". A vxi11 transport is
+# reserved for a future release.
+[datasource.scpi]
+enabled          = false
+poll_interval_ms = 1000
+
+# [[datasource.scpi.instruments]]
+# name       = "dmm1"
+# transport  = "raw"               # raw (default); vxi11 reserved
+# address    = "192.168.1.60:5025" # ":5025" appended if no port given
+# timeout_ms = 3000
+# terminator = "\n"
+#
+#   [[datasource.scpi.instruments.channels]]
+#   name        = "voltage"
+#   query       = "MEAS:VOLT?"      # SCPI query whose response is the value
+#   write_cmd   = "VOLT %v"         # printf template; omit for read-only
+#   type        = "float"           # float (default) | int | string | bool
+#   unit        = "V"
+#   min         = 0
+#   max         = 30
+#   description = "DC voltage"

web/src/Canvas.tsx

@@ -1,7 +1,7 @@
 import { h, Fragment } from 'preact';
 import { useState, useEffect } from 'preact/hooks';
 import { initLocalState } from './lib/localstate';
-import { logicEngine } from './lib/logic';
+import { logicEngine, ensureArrayDecls } from './lib/logic';
 import { getWidgetCmdStore, type WidgetCmd } from './lib/widgetCommands';
 import type { Interface, Widget, SignalRef } from './lib/types';
 import TextView from './widgets/TextView';
@@ -119,9 +119,11 @@ export default function Canvas({ iface, onNavigate, timeRange }: Props) {
   }
 
   // Instantiate this panel's local state variables from their initial values.
+  // ensureArrayDecls auto-declares any array referenced by logic nodes that
+  // are not yet declared as state vars (backward-compat migration).
   useEffect(() => {
-    initLocalState(iface?.statevars);
-  }, [iface?.id, iface?.statevars]);
+    initLocalState(ensureArrayDecls(iface?.logic, iface?.statevars ?? []));
+  }, [iface?.id, iface?.statevars, iface?.logic]);
 
   // Activate panel logic for the live view; tear it down on unmount/panel switch.
   useEffect(() => {

web/src/EditMode.tsx

@@ -3,6 +3,7 @@ import { useState, useCallback, useRef, useEffect } from 'preact/hooks';
 import type { Interface, Widget, PlotLayout, StateVar, LogicGraph, Folder } from './lib/types';
 import { serializeInterface, parseInterface } from './lib/xml';
 import { initLocalState } from './lib/localstate';
+import { ensureArrayDecls } from './lib/logic';
 import SignalTree from './SignalTree';
 import EditCanvas, { genWidgetId, DEFAULT_SIZES } from './EditCanvas';
 import PlotPanelCanvas from './PlotPanelCanvas';
@@ -251,9 +252,11 @@ export default function EditMode({ initial, onDone }: Props) {
   }, []);
 
   const handleStateVarsChange = useCallback((statevars: StateVar[]) => {
-    setIface(f => ({ ...f, statevars }));
+    setIface(f => {
+      initLocalState(ensureArrayDecls(f.logic, statevars));
+      return { ...f, statevars };
+    });
     setDirty(true);
-    initLocalState(statevars);
   }, []);
 
   const handleLogicChange = useCallback((logic: LogicGraph) => {
@@ -264,7 +267,7 @@ export default function EditMode({ initial, onDone }: Props) {
   // Instantiate local state variables when the edited panel loads/changes so
   // they can be previewed live in the canvas just like real signals.
   useEffect(() => {
-    initLocalState(iface.statevars);
+    initLocalState(ensureArrayDecls(iface.logic, iface.statevars ?? []));
   }, [iface.id]);
 
   // ── Keyboard shortcuts ─────────────────────────────────────────────────────

web/src/HelpModal.tsx

@@ -657,7 +657,7 @@ function SectionLogic() {
         {[
           { type: 'Triggers',  desc: 'Button press, threshold crossing, value change, timer/interval, panel loop, and On-open / On-close lifecycle.' },
           { type: 'Logic',     desc: 'AND gate, If (then/else branches), and Loop (count or while).' },
-          { type: 'Actions',   desc: 'Write a value to a signal/variable, Delay, Log (debug), and Accumulate / Export-CSV / Clear for in-memory data arrays.' },
+          { type: 'Actions',   desc: 'Write a value to a signal/variable, Delay, Log (debug), Array push/set/remove/pop/clear on an array local variable, and Export-CSV.' },
           { type: 'Dialogs',   desc: 'Info and Error pop-ups, and a Set-point prompt that asks the user for a number and writes it to a target.' },
         ].map(w => (
           <div key={w.type} class="help-widget-row">

web/src/LogicEditor.tsx

@@ -73,9 +73,7 @@ const PALETTE: PaletteEntry[] = [
   { kind: 'flow.loop',         label: 'Loop',       params: { mode: 'count', count: '3', cond: '' } },
   { kind: 'action.write',      label: 'Write',      params: { target: '', expr: '' } },
   { kind: 'action.delay',      label: 'Delay',      params: { ms: '500' } },
-  { kind: 'action.accumulate', label: 'Accumulate', params: { array: 'data', expr: '' } },
-  { kind: 'action.export',     label: 'Export CSV', params: { columns: '[{"array":"data","label":""}]', align: 'common', filename: '' } },
-  { kind: 'action.clear',      label: 'Clear array', params: { array: 'data' } },
+  { kind: 'action.export',     label: 'Export CSV', params: { columns: '[{"array":"","label":""}]', align: 'common', filename: '' } },
   { kind: 'action.log',        label: 'Log',        params: { expr: '', label: '' } },
   { kind: 'action.widget',     label: 'Widget control', params: { widget: '', op: 'disable' } },
   { kind: 'action.dialog.info',     label: 'Info dialog',      params: { title: 'Info', message: '' } },
@@ -86,6 +84,11 @@ const PALETTE: PaletteEntry[] = [
   { 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: '' } },
+  { kind: 'action.array.push',   label: 'Array push',   params: { array: '', expr: '' } },
+  { kind: 'action.array.set',    label: 'Array set',    params: { array: '', index: '', expr: '' } },
+  { kind: 'action.array.remove', label: 'Array remove', params: { array: '', index: '' } },
+  { kind: 'action.array.pop',    label: 'Array pop',    params: { array: '' } },
+  { kind: 'action.array.clear',  label: 'Array clear',  params: { array: '' } },
 ];
 
 const KIND_LABEL: Record<LogicNodeKind, string> = {
@@ -101,9 +104,7 @@ const KIND_LABEL: Record<LogicNodeKind, string> = {
   'flow.loop': 'Loop',
   'action.write': 'Write',
   'action.delay': 'Delay',
-  'action.accumulate': 'Accumulate',
   'action.export': 'Export CSV',
-  'action.clear': 'Clear array',
   'action.log': 'Log',
   'action.widget': 'Widget control',
   'action.dialog.info': 'Info dialog',
@@ -114,6 +115,11 @@ const KIND_LABEL: Record<LogicNodeKind, string> = {
   'action.config.write': 'Write config',
   'action.config.create': 'Create config',
   'action.config.snapshot': 'Snapshot config',
+  'action.array.push':   'Array push',
+  'action.array.set':    'Array set',
+  'action.array.remove': 'Array remove',
+  'action.array.pop':    'Array pop',
+  'action.array.clear':  'Array clear',
 };
 
 const THRESHOLD_OPS = ['>', '<', '>=', '<=', '==', '!='] as const;
@@ -565,12 +571,6 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
 
   const byId = new Map(nodes.map(n => [n.id, n]));
 
-  // Array names already referenced by accumulate/export/clear nodes, offered as
-  // autocomplete suggestions so the same array is reused across nodes.
-  const arrayNames = Array.from(new Set(
-    nodes.map(n => n.params.array).filter((a): a is string => !!a)
-  ));
-
   // Append a {ds:name} reference into a node's expression field.
   function insertRef(id: string, field: string, ds: string, sig: string) {
     const cur = (byId.get(id)?.params[field]) ?? '';
@@ -670,9 +670,6 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
         {onStateVarsChange && (
           <LocalVars statevars={statevars ?? []} onChange={onStateVarsChange} />
         )}
-        <datalist id="flow-array-names">
-          {arrayNames.map(a => <option key={a} value={a} />)}
-        </datalist>
       </div>
 
       <div class="flow-canvas" ref={canvasRef}
@@ -1019,25 +1016,10 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
               </Fragment>
             )}
 
-            {selected.kind === 'action.accumulate' && (
-              <Fragment>
-                <div class="wizard-field">
-                  <label>Array name</label>
-                  <input class="prop-input" value={selected.params.array ?? ''} list="flow-array-names"
-                    placeholder="e.g. data"
-                    onInput={(e) => patchParams(selected.id, { array: (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="Appends this value (with a timestamp) to the array. e.g. {stub:level}, or {sys:time} for the clock." />
-              </Fragment>
-            )}
-
             {selected.kind === 'action.export' && (
               <ExportEditor
                 columns={parseExportColumns(selected)}
+                arrayLocals={(statevars ?? []).filter(v => v.type === 'array').map(v => v.name)}
                 align={selected.params.align ?? 'common'}
                 filename={selected.params.filename ?? ''}
                 onColumns={(cols) => patchParams(selected.id, { columns: JSON.stringify(cols) })}
@@ -1045,15 +1027,49 @@ export default function LogicEditor({ graph, onChange, widgets = [], statevars,
                 onFilename={(f) => patchParams(selected.id, { filename: f })} />
             )}
 
-            {selected.kind === 'action.clear' && (
+            {(selected.kind === 'action.array.push' || selected.kind === 'action.array.set' ||
+              selected.kind === 'action.array.remove' || selected.kind === 'action.array.pop' ||
+              selected.kind === 'action.array.clear') && (() => {
+              const arrayLocals = (statevars ?? []).filter(v => v.type === 'array');
+              return (
+                <Fragment>
                   <div class="wizard-field">
-                <label>Array name</label>
-                <input class="prop-input" value={selected.params.array ?? ''} list="flow-array-names"
-                  placeholder="e.g. data"
-                  onInput={(e) => patchParams(selected.id, { array: (e.target as HTMLInputElement).value })} />
-                <p class="hint">Empties the named array (e.g. to start a fresh capture).</p>
+                    <label>Array (local variable)</label>
+                    <select class="prop-select" value={selected.params.array ?? ''}
+                      onChange={(e) => patchParams(selected.id, { array: (e.target as HTMLSelectElement).value })}>
+                      <option value="">— select array —</option>
+                      {arrayLocals.map(v => <option key={v.name} value={v.name}>{v.name}</option>)}
+                    </select>
+                    {arrayLocals.length === 0 && (
+                      <p class="hint">No array locals declared yet — add one in the Local vars panel.</p>
+                    )}
+                  </div>
+                  {(selected.kind === 'action.array.set' || selected.kind === 'action.array.remove') && (
+                    <div class="wizard-field">
+                      <label>Index / path (comma-separated)</label>
+                      <input class="prop-input" value={selected.params.index ?? ''}
+                        placeholder="e.g. 0  or  2,1"
+                        onInput={(e) => patchParams(selected.id, { index: (e.target as HTMLInputElement).value })} />
+                      <p class="hint">Single integer for a flat array; comma-separated integers for a nested array.</p>
                     </div>
                   )}
+                  {(selected.kind === 'action.array.push' || selected.kind === 'action.array.set') && (
+                    <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={selected.kind === 'action.array.push'
+                        ? 'Value to append to the end of the array.'
+                        : 'Value to store at the given index / path.'} />
+                  )}
+                  {(selected.kind === 'action.array.pop' || selected.kind === 'action.array.clear') && (
+                    <p class="hint">{selected.kind === 'action.array.pop'
+                      ? 'Removes and returns the last element of the array.'
+                      : 'Removes all elements from the array.'}</p>
+                  )}
+                </Fragment>
+              );
+            })()}
 
             {selected.kind === 'action.log' && (
               <Fragment>
@@ -1210,9 +1226,9 @@ function ExprField({ label, value, onChange, onInsert, allSignals, onOpenSignals
 
 interface ExportColumn { array: string; label: string; }
 
-// The columns configured on an action.export node. Reads the JSON `columns`
-// param; falls back to the legacy single `array` param (so old panels migrate
-// transparently the first time the node is edited).
+// The columns configured on an action.export node, read from the JSON `columns`
+// param. Legacy single-`array` nodes are migrated to this form on load (see
+// xml.ts migrateLegacyArrayNode), so only the JSON form is read here.
 function parseExportColumns(n: LogicNode): ExportColumn[] {
   const raw = (n.params.columns ?? '').trim();
   if (raw) {
@@ -1223,8 +1239,7 @@ function parseExportColumns(n: LogicNode): ExportColumn[] {
       }
     } catch {}
   }
-  const a = (n.params.array ?? '').trim();
-  return [{ array: a, label: '' }];
+  return [{ array: '', label: '' }];
 }
 
 const ALIGN_OPTS: Array<{ value: string; label: string; hint: string }> = [
@@ -1233,8 +1248,9 @@ const ALIGN_OPTS: Array<{ value: string; label: string; hint: string }> = [
   { value: 'interpolate', label: 'Interpolate', hint: 'Union of all timestamps; missing cells linearly interpolated.' },
 ];
 
-function ExportEditor({ columns, align, filename, onColumns, onAlign, onFilename }: {
+function ExportEditor({ columns, arrayLocals, align, filename, onColumns, onAlign, onFilename }: {
   columns: ExportColumn[];
+  arrayLocals: string[];
   align: string;
   filename: string;
   onColumns: (cols: ExportColumn[]) => void;
@@ -1248,12 +1264,15 @@ function ExportEditor({ columns, align, filename, onColumns, onAlign, onFilename
   return (
     <Fragment>
       <div class="wizard-field">
-        <label>Columns (arrays)</label>
+        <label>Columns (array local variables)</label>
         {columns.map((c, i) => (
           <div key={i} class="flow-row-edit">
-            <input class="prop-input" value={c.array} list="flow-array-names"
-              placeholder="array name"
-              onInput={(e) => patch(i, { array: (e.target as HTMLInputElement).value })} />
+            <select class="prop-select" value={c.array}
+              onChange={(e) => patch(i, { array: (e.target as HTMLSelectElement).value })}>
+              <option value="">— select array —</option>
+              {c.array && !arrayLocals.includes(c.array) && <option value={c.array}>{c.array}</option>}
+              {arrayLocals.map(name => <option key={name} value={name}>{name}</option>)}
+            </select>
             <input class="prop-input" value={c.label}
               placeholder="column label (optional)"
               onInput={(e) => patch(i, { label: (e.target as HTMLInputElement).value })} />
@@ -1263,6 +1282,9 @@ function ExportEditor({ columns, align, filename, onColumns, onAlign, onFilename
           </div>
         ))}
         <button class="panel-btn flow-row-add" onClick={() => onColumns([...columns, { array: '', label: '' }])}>+ Add column</button>
+        {arrayLocals.length === 0 && (
+          <p class="hint">No array locals declared yet — add one in the Local vars panel.</p>
+        )}
       </div>
       {columns.length > 1 && (
         <div class="wizard-field">
@@ -1397,13 +1419,16 @@ function nodeSummary(n: LogicNode): string {
                                 : `while ${n.params.cond || '?'}`;
     case 'action.write':      return `${n.params.target || '?'} = ${n.params.expr || ''}`;
     case 'action.delay':      return `wait ${n.params.ms || '0'} ms`;
-    case 'action.accumulate': return `${n.params.array || '?'} ← ${n.params.expr || ''}`;
     case 'action.export': {
       const cols = parseExportColumns(n).filter(c => c.array);
       const names = cols.map(c => c.label || c.array).join(', ');
       return `export ${names || '?'} → csv`;
     }
-    case 'action.clear':      return `clear ${n.params.array || '?'}`;
+    case 'action.array.push':   return `push ${n.params.expr || ''} → ${n.params.array || '?'}`;
+    case 'action.array.set':    return `${n.params.array || '?'}[${n.params.index || '?'}] = ${n.params.expr || ''}`;
+    case 'action.array.remove': return `remove ${n.params.array || '?'}[${n.params.index || '?'}]`;
+    case 'action.array.pop':    return `pop ${n.params.array || '?'}`;
+    case 'action.array.clear':  return `clear ${n.params.array || '?'}`;
     case 'action.log':        return `log ${n.params.label ? n.params.label + ': ' : ''}${n.params.expr || ''}`;
     case 'action.widget':     return `${n.params.op || 'disable'} ${n.params.widget || '?'}`;
     case 'action.dialog.info':     return `info: ${n.params.title || n.params.message || '…'}`;
@@ -1429,15 +1454,47 @@ function LocalVars({ statevars, onChange }: {
 }) {
   const [open, setOpen] = useState(false);
   const [name, setName] = useState('');
-  const [type, setType] = useState<'number' | 'bool' | 'string'>('number');
+  const [type, setType] = useState<'number' | 'bool' | 'string' | 'array'>('number');
   const [initial, setInitial] = useState('0');
+  // array-specific fields
+  const [elem, setElem] = useState<'number' | 'bool' | 'array'>('number');
+  const [sizing, setSizing] = useState<'dynamic' | 'capped' | 'fixed'>('dynamic');
+  const [capacity, setCapacity] = useState('100');
+  const [jsonErr, setJsonErr] = useState('');
+
+  function handleInitialChange(v: string) {
+    setInitial(v);
+    if (type === 'array') {
+      try { JSON.parse(v); setJsonErr(''); }
+      catch (e: any) { setJsonErr(e.message); }
+    }
+  }
+
+  function handleTypeChange(t: 'number' | 'bool' | 'string' | 'array') {
+    setType(t);
+    setInitial(t === 'array' ? '[]' : t === 'bool' ? 'false' : t === 'string' ? '' : '0');
+    setJsonErr('');
+  }
 
   function add() {
     const n = name.trim();
     if (!n) return;
-    onChange([...statevars.filter(v => v.name !== n), { name: n, type, initial }]);
+    if (type === 'array' && jsonErr) return;
+    const base: StateVar = { name: n, type, initial };
+    if (type === 'array') {
+      base.elem = elem;
+      base.sizing = sizing;
+      if (sizing !== 'dynamic') base.capacity = parseInt(capacity, 10) || 100;
+    }
+    onChange([...statevars.filter(v => v.name !== n), base]);
     setName('');
     setInitial('0');
+    setType('number');
+    setElem('number');
+    setSizing('dynamic');
+    setCapacity('100');
+    setJsonErr('');
+    setOpen(false);
   }
 
   return (
@@ -1446,7 +1503,7 @@ function LocalVars({ statevars, onChange }: {
       {statevars.length === 0 && <div class="hint flow-localvars-empty">None yet.</div>}
       {statevars.map(v => (
         <div key={v.name} class="flow-localvar-row">
-          <span class="flow-localvar-name" title={`${v.type ?? 'number'} = ${v.initial}`}>{v.name}</span>
+          <span class="flow-localvar-name" title={`${v.type ?? 'number'}${v.type === 'array' ? `<${v.elem ?? 'number'}> ${v.sizing ?? 'dynamic'}` : ''} = ${v.initial}`}>{v.name}</span>
           <button class="flow-node-del" title="Remove"
             onClick={() => onChange(statevars.filter(x => x.name !== v.name))}>✕</button>
         </div>
@@ -1459,15 +1516,41 @@ function LocalVars({ statevars, onChange }: {
           <input class="prop-input" value={name} placeholder="name"
             onInput={(e) => setName((e.target as HTMLInputElement).value)} />
           <select class="prop-select" value={type}
-            onChange={(e) => setType((e.target as HTMLSelectElement).value as 'number' | 'bool' | 'string')}>
+            onChange={(e) => handleTypeChange((e.target as HTMLSelectElement).value as 'number' | 'bool' | 'string' | 'array')}>
             <option value="number">number</option>
             <option value="bool">bool</option>
             <option value="string">string</option>
+            <option value="array">array</option>
           </select>
+          {type === 'array' && (
+            <Fragment>
+              <select class="prop-select" value={elem}
+                onChange={(e) => setElem((e.target as HTMLSelectElement).value as 'number' | 'bool' | 'array')}>
+                <option value="number">elem: number</option>
+                <option value="bool">elem: bool</option>
+                <option value="array">elem: array</option>
+              </select>
+              <select class="prop-select" value={sizing}
+                onChange={(e) => setSizing((e.target as HTMLSelectElement).value as 'dynamic' | 'capped' | 'fixed')}>
+                <option value="dynamic">sizing: dynamic</option>
+                <option value="capped">sizing: capped</option>
+                <option value="fixed">sizing: fixed</option>
+              </select>
+              {sizing !== 'dynamic' && (
+                <input class="prop-input" type="number" value={capacity} placeholder="capacity"
+                  onInput={(e) => setCapacity((e.target as HTMLInputElement).value)} />
+              )}
+              <input class={`prop-input${jsonErr ? ' prop-input-error' : ''}`} value={initial} placeholder="initial (JSON)"
+                onInput={(e) => handleInitialChange((e.target as HTMLInputElement).value)} />
+              {jsonErr && <p class="wizard-error">{jsonErr}</p>}
+            </Fragment>
+          )}
+          {type !== 'array' && (
             <input class="prop-input" value={initial} placeholder="initial"
               onInput={(e) => setInitial((e.target as HTMLInputElement).value)} />
+          )}
           <div class="flow-localvar-actions">
-            <button class="panel-btn" onClick={add}>Add</button>
+            <button class="panel-btn" onClick={add} disabled={!name.trim() || (type === 'array' && !!jsonErr)}>Add</button>
             <button class="panel-btn" onClick={() => { setOpen(false); setName(''); }}>Cancel</button>
           </div>
         </div>

web/src/SignalTree.tsx

@@ -117,17 +117,48 @@ export default function SignalTree({ onDragStart, width, panelId, statevars, onS
   const [showAddLocal, setShowAddLocal] = useState(false);
   const [localOpen, setLocalOpen] = useState(true);
   const [lvName, setLvName] = useState('');
-  const [lvType, setLvType] = useState<'number' | 'bool' | 'string'>('number');
+  const [lvType, setLvType] = useState<'number' | 'bool' | 'string' | 'array'>('number');
   const [lvInitial, setLvInitial] = useState('0');
+  // array-specific fields (mirror LogicEditor LocalVars)
+  const [lvElem, setLvElem] = useState<'number' | 'bool' | 'array'>('number');
+  const [lvSizing, setLvSizing] = useState<'dynamic' | 'capped' | 'fixed'>('dynamic');
+  const [lvCapacity, setLvCapacity] = useState('100');
+  const [lvJsonErr, setLvJsonErr] = useState('');
+
+  function handleLvTypeChange(t: 'number' | 'bool' | 'string' | 'array') {
+    setLvType(t);
+    setLvInitial(t === 'array' ? '[]' : t === 'bool' ? 'false' : t === 'string' ? '' : '0');
+    setLvJsonErr('');
+  }
+
+  function handleLvInitialChange(v: string) {
+    setLvInitial(v);
+    if (lvType === 'array') {
+      try { JSON.parse(v); setLvJsonErr(''); }
+      catch (e: any) { setLvJsonErr(e.message); }
+    }
+  }
 
   function addLocal() {
     const name = lvName.trim();
     if (!name || !onStateVarsChange) return;
+    if (lvType === 'array' && lvJsonErr) return;
+    const base: StateVar = { name, type: lvType, initial: lvInitial };
+    if (lvType === 'array') {
+      base.elem = lvElem;
+      base.sizing = lvSizing;
+      if (lvSizing !== 'dynamic') base.capacity = parseInt(lvCapacity, 10) || 100;
+    }
     const next = (statevars ?? []).filter(v => v.name !== name);
-    next.push({ name, type: lvType, initial: lvInitial });
+    next.push(base);
     onStateVarsChange(next);
     setLvName('');
     setLvInitial('0');
+    setLvType('number');
+    setLvElem('number');
+    setLvSizing('dynamic');
+    setLvCapacity('100');
+    setLvJsonErr('');
     setShowAddLocal(false);
   }
 
@@ -324,20 +355,56 @@ export default function SignalTree({ onDragStart, width, panelId, statevars, onS
                         class="prop-select"
                         style="font-size: 0.7rem; height: 1.6rem; padding: 0 4px;"
                         value={lvType}
-                        onChange={(e) => setLvType((e.target as HTMLSelectElement).value as any)}
+                        onChange={(e) => handleLvTypeChange((e.target as HTMLSelectElement).value as any)}
                       >
                         <option value="number">number</option>
                         <option value="bool">bool</option>
                         <option value="string">string</option>
+                        <option value="array">array</option>
                       </select>
+                      {lvType === 'array' && (
+                        <Fragment>
+                          <select
+                            class="prop-select"
+                            style="font-size: 0.7rem; height: 1.6rem; padding: 0 4px;"
+                            value={lvElem}
+                            onChange={(e) => setLvElem((e.target as HTMLSelectElement).value as any)}
+                          >
+                            <option value="number">elem: number</option>
+                            <option value="bool">elem: bool</option>
+                            <option value="array">elem: array</option>
+                          </select>
+                          <select
+                            class="prop-select"
+                            style="font-size: 0.7rem; height: 1.6rem; padding: 0 4px;"
+                            value={lvSizing}
+                            onChange={(e) => setLvSizing((e.target as HTMLSelectElement).value as any)}
+                          >
+                            <option value="dynamic">sizing: dynamic</option>
+                            <option value="capped">sizing: capped</option>
+                            <option value="fixed">sizing: fixed</option>
+                          </select>
+                          {lvSizing !== 'dynamic' && (
                             <input
                               class="signal-add-input"
+                              type="number"
+                              style="width: 5rem;"
+                              placeholder="capacity"
+                              value={lvCapacity}
+                              onInput={(e) => setLvCapacity((e.target as HTMLInputElement).value)}
+                            />
+                          )}
+                        </Fragment>
+                      )}
+                      <input
+                        class={`signal-add-input${lvJsonErr ? ' prop-input-error' : ''}`}
                         style="flex: 1;"
-                        placeholder="initial"
+                        placeholder={lvType === 'array' ? 'initial (JSON)' : 'initial'}
                         value={lvInitial}
-                        onInput={(e) => setLvInitial((e.target as HTMLInputElement).value)}
+                        onInput={(e) => handleLvInitialChange((e.target as HTMLInputElement).value)}
                         onKeyDown={(e: KeyboardEvent) => { if (e.key === 'Enter') addLocal(); }}
                       />
+                      {lvJsonErr && <p class="wizard-error" style="flex-basis: 100%; margin: 0;">{lvJsonErr}</p>}
                       <button class="icon-btn" title="Add" onClick={addLocal}>✓</button>
                       <button class="icon-btn" title="Cancel" onClick={() => setShowAddLocal(false)}>✕</button>
                     </div>

web/src/lib/arraypolicy.ts

@@ -0,0 +1,54 @@
+// Pure helpers for array-valued local state: parse the declared initial value
+// and enforce the declared sizing policy (dynamic / capped / fixed). Shared by
+// localstate.ts (write path) and logic.ts (node handlers + migration).
+
+import type { StateVar } from './types';
+
+export type ArrVal = number | ArrVal[];
+export const ARRAY_MAX = 1_000_000;
+
+// zeroFill builds a length-n array of zeros (flat; fixed nested init must come
+// from an explicit `initial` literal).
+function zeroFill(n: number): ArrVal[] {
+  return new Array(Math.max(0, n)).fill(0);
+}
+
+// parseInitialArray returns the starting contents of an array local.
+export function parseInitialArray(sv: StateVar): ArrVal[] {
+  const cap = sv.capacity ?? 0;
+  const raw = (sv.initial ?? '').trim();
+  let parsed: ArrVal[] | null = null;
+  if (raw) {
+    try {
+      const j = JSON.parse(raw);
+      if (Array.isArray(j)) parsed = j as ArrVal[];
+    } catch { parsed = null; }
+  }
+  if (sv.sizing === 'fixed') {
+    if (!parsed) return zeroFill(cap);
+    // truncate / zero-pad to capacity
+    const out = parsed.slice(0, cap);
+    while (out.length < cap) out.push(0);
+    return out;
+  }
+  return parsed ?? [];
+}
+
+// applySizing returns arr clamped to the declared policy.
+//   dynamic → unchanged (but globally capped at ARRAY_MAX, dropping oldest)
+//   capped  → keep at most capacity elements, dropping oldest (ring/FIFO)
+//   fixed   → exactly capacity elements (truncate / zero-pad); never grow/shrink
+export function applySizing(arr: ArrVal[], sv: StateVar): ArrVal[] {
+  const cap = sv.capacity ?? 0;
+  switch (sv.sizing) {
+    case 'fixed': {
+      const out = arr.slice(0, cap);
+      while (out.length < cap) out.push(0);
+      return out;
+    }
+    case 'capped':
+      return arr.length > cap ? arr.slice(arr.length - cap) : arr;
+    default:
+      return arr.length > ARRAY_MAX ? arr.slice(arr.length - ARRAY_MAX) : arr;
+  }
+}

web/src/lib/expr.ts

@@ -2,8 +2,9 @@
 //
 // Supports numbers, booleans (true/false → 1/0), arithmetic (+ - * / %),
 // comparison (< <= > >= == !=), boolean (&& || !), ternary (a ? b : c),
-// parentheses, and a handful of math functions. Two kinds of variable
-// reference are resolved live at evaluation time:
+// parentheses, array literals ([a, b, c]), postfix indexing (arr[i]),
+// and a set of math + array functions. Two kinds of variable reference are
+// resolved live at evaluation time:
 //   {ds:name}   a data-source signal value (the brace content is split on the
 //               FIRST ':' so EPICS PV names like "MY:PV:NAME" work).
 //   bareIdent   a panel-local state variable (data source 'local').
@@ -12,6 +13,8 @@
 // and any nonzero value is truthy. The evaluator never touches the DOM or eval;
 // it walks a parsed AST against a caller-supplied resolver.
 
+import type { ArrVal } from './arraypolicy';
+
 export interface RefLite { ds: string; name: string }
 
 type Node =
@@ -21,12 +24,12 @@ type Node =
   | { t: 'un'; op: string; a: Node }
   | { t: 'bin'; op: string; a: Node; b: Node }
   | { t: 'tern'; c: Node; a: Node; b: Node }
-  | { t: 'call'; fn: string; args: Node[] };
+  | { t: 'call'; fn: string; args: Node[] }
+  | { t: 'arr'; items: Node[] }
+  | { t: 'index'; a: Node; i: Node };
 
-const FUNCS: Record<string, (a: number[]) => number> = {
+const SCALAR_FUNCS: Record<string, (a: number[]) => number> = {
   abs: a => Math.abs(a[0]),
-  min: a => Math.min(...a),
-  max: a => Math.max(...a),
   sqrt: a => Math.sqrt(a[0]),
   floor: a => Math.floor(a[0]),
   ceil: a => Math.ceil(a[0]),
@@ -77,8 +80,8 @@ function tokenize(src: string): Tok[] {
     // two-char operators
     const pair = src.slice(i, i + 2);
     if (two.includes(pair)) { toks.push({ k: pair }); i += 2; continue; }
-    // single-char operators / punctuation
-    if ('+-*/%<>!()?:,'.includes(c)) { toks.push({ k: c }); i++; continue; }
+    // single-char operators / punctuation (including brackets)
+    if ('+-*/%<>!()?:,[]'.includes(c)) { toks.push({ k: c }); i++; continue; }
     throw new Error(`unexpected character '${c}' in expression`);
   }
   return toks;
@@ -97,10 +100,20 @@ function parse(src: string): Node {
     return t;
   };
 
-  function primary(): Node {
+  function atom(): Node {
     const t = peek();
     if (!t) throw new Error('unexpected end of expression');
     if (t.k === 'num') { eat(); return { t: 'num', v: parseFloat(t.v!) }; }
+    if (t.k === '[') {
+      eat('[');
+      const items: Node[] = [];
+      if (peek()?.k !== ']') {
+        items.push(ternary());
+        while (peek()?.k === ',') { eat(','); items.push(ternary()); }
+      }
+      eat(']');
+      return { t: 'arr', items };
+    }
     if (t.k === 'sig') {
       eat();
       const raw = t.v!;
@@ -130,6 +143,17 @@ function parse(src: string): Node {
     throw new Error(`unexpected token '${t.k}' in expression`);
   }
 
+  function primary(): Node {
+    let n = atom();
+    while (peek()?.k === '[') {
+      eat('[');
+      const i = ternary();
+      eat(']');
+      n = { t: 'index', a: n, i };
+    }
+    return n;
+  }
+
   function unary(): Node {
     const t = peek();
     if (t && (t.k === '-' || t.k === '!')) { eat(); return { t: 'un', op: t.k, a: unary() }; }
@@ -186,34 +210,83 @@ function parseCached(src: string): Node {
 
 // ── Evaluation ─────────────────────────────────────────────────────────────
 
-export type Resolver = (ds: string, name: string) => number;
+export type Resolver = (ds: string, name: string) => ArrVal;
 
-function ev(n: Node, R: Resolver): number {
+function asNum(v: ArrVal): number {
+  if (typeof v !== 'number') throw new Error('expected a number, got an array');
+  return v;
+}
+function asArr(v: ArrVal): ArrVal[] {
+  if (!Array.isArray(v)) throw new Error('expected an array, got a number');
+  return v;
+}
+// resolve a possibly-negative index against length
+function idx(i: number, len: number): number {
+  const k = Math.trunc(i) < 0 ? len + Math.trunc(i) : Math.trunc(i);
+  if (k < 0 || k >= len) throw new Error(`index ${i} out of range (len ${len})`);
+  return k;
+}
+
+const ARR_FUNCS: Record<string, (a: ArrVal[]) => ArrVal> = {
+  len: a => asArr(a[0]).length,
+  sum: a => asArr(a[0]).reduce<number>((s, x) => s + asNum(x), 0),
+  mean: a => { const r = asArr(a[0]); return r.length ? r.reduce<number>((s, x) => s + asNum(x), 0) / r.length : 0; },
+  // min/max: scalar-variadic OR single-array — see ev() dispatch below
+  slice: a => { const r = asArr(a[0]); const s = a[1] === undefined ? 0 : asNum(a[1]); const e = a[2] === undefined ? r.length : asNum(a[2]); return r.slice(s, e); },
+  concat: a => asArr(a[0]).concat(asArr(a[1])),
+  reverse: a => asArr(a[0]).slice().reverse(),
+  sort: a => asArr(a[0]).slice().sort((x, y) => asNum(x) - asNum(y)),
+  scale: a => asArr(a[0]).map(x => asNum(x) * asNum(a[1])),
+  add: a => { const x = asArr(a[0]), y = asArr(a[1]); const n = Math.min(x.length, y.length); const o: ArrVal[] = []; for (let k = 0; k < n; k++) o.push(asNum(x[k]) + asNum(y[k])); return o; },
+  sub: a => { const x = asArr(a[0]), y = asArr(a[1]); const n = Math.min(x.length, y.length); const o: ArrVal[] = []; for (let k = 0; k < n; k++) o.push(asNum(x[k]) - asNum(y[k])); return o; },
+  push: a => asArr(a[0]).concat([a[1]]),
+  set: a => { const r = asArr(a[0]).slice(); r[idx(asNum(a[1]), r.length)] = a[2]; return r; },
+  insert: a => { const r = asArr(a[0]).slice(); const k = Math.max(0, Math.min(r.length, Math.trunc(asNum(a[1])))); r.splice(k, 0, a[2]); return r; },
+  remove: a => { const r = asArr(a[0]).slice(); r.splice(idx(asNum(a[1]), r.length), 1); return r; },
+  pop: a => { const r = asArr(a[0]).slice(); r.pop(); return r; },
+  shift: a => { const r = asArr(a[0]).slice(); r.shift(); return r; },
+  indexOf: a => { const r = asArr(a[0]); for (let k = 0; k < r.length; k++) if (r[k] === a[1]) return k; return -1; },
+  contains: a => { const r = asArr(a[0]); for (let k = 0; k < r.length; k++) if (r[k] === a[1]) return 1; return 0; },
+  fill: a => new Array(Math.max(0, Math.trunc(asNum(a[0])))).fill(a[1]),
+};
+
+function ev(n: Node, R: Resolver): ArrVal {
   switch (n.t) {
     case 'num': return n.v;
+    case 'arr': return n.items.map(it => ev(it, R));
     case 'sig': return R(n.ds, n.name);
     case 'var': return R('local', n.name);
-    case 'un': return n.op === '-' ? -ev(n.a, R) : (ev(n.a, R) === 0 ? 1 : 0);
-    case 'tern': return ev(n.c, R) !== 0 ? ev(n.a, R) : ev(n.b, R);
+    case 'index': {
+      const arr = asArr(ev(n.a, R));
+      return arr[idx(asNum(ev(n.i, R)), arr.length)];
+    }
+    case 'un': return n.op === '-' ? -asNum(ev(n.a, R)) : (asNum(ev(n.a, R)) === 0 ? 1 : 0);
+    case 'tern': return asNum(ev(n.c, R)) !== 0 ? ev(n.a, R) : ev(n.b, R);
     case 'call': {
-      const fn = FUNCS[n.fn];
-      if (!fn) throw new Error(`unknown function '${n.fn}'`);
-      return fn(n.args.map(a => ev(a, R)));
+      const args = n.args.map(a => ev(a, R));
+      // min/max keep scalar-variadic form, plus 1-arg array form
+      if ((n.fn === 'min' || n.fn === 'max') && !(args.length === 1 && Array.isArray(args[0]))) {
+        const nums = args.map(asNum);
+        return n.fn === 'min' ? Math.min(...nums) : Math.max(...nums);
+      }
+      if (n.fn === 'min' || n.fn === 'max') {
+        const r = asArr(args[0]).map(asNum);
+        return n.fn === 'min' ? Math.min(...r) : Math.max(...r);
+      }
+      const af = ARR_FUNCS[n.fn];
+      if (af) return af(args);
+      const sf = SCALAR_FUNCS[n.fn];
+      if (sf) return sf(args.map(asNum));
+      throw new Error(`unknown function '${n.fn}'`);
     }
     case 'bin': {
-      const a = ev(n.a, R), b = ev(n.b, R);
+      const a = asNum(ev(n.a, R)), b = asNum(ev(n.b, R));
       switch (n.op) {
-        case '+': return a + b;
-        case '-': return a - b;
-        case '*': return a * b;
-        case '/': return a / b;
-        case '%': return a % b;
-        case '<': return a < b ? 1 : 0;
-        case '<=': return a <= b ? 1 : 0;
-        case '>': return a > b ? 1 : 0;
-        case '>=': return a >= b ? 1 : 0;
-        case '==': return a === b ? 1 : 0;
-        case '!=': return a !== b ? 1 : 0;
+        case '+': return a + b; case '-': return a - b; case '*': return a * b;
+        case '/': return a / b; case '%': return a % b;
+        case '<': return a < b ? 1 : 0; case '<=': return a <= b ? 1 : 0;
+        case '>': return a > b ? 1 : 0; case '>=': return a >= b ? 1 : 0;
+        case '==': return a === b ? 1 : 0; case '!=': return a !== b ? 1 : 0;
         case '&&': return (a !== 0 && b !== 0) ? 1 : 0;
         case '||': return (a !== 0 || b !== 0) ? 1 : 0;
         default: throw new Error(`unknown operator '${n.op}'`);
@@ -222,10 +295,16 @@ function ev(n: Node, R: Resolver): number {
   }
 }
 
-/** Evaluate an expression string. Returns NaN if it cannot be parsed/evaluated. */
+/** Evaluate an expression string; returns the full value (number or array). */
+export function evalValue(src: string, resolve: Resolver): ArrVal {
+  return ev(parseCached(src), resolve);
+}
+
+/** Evaluate an expression string. Returns NaN if it cannot be parsed/evaluated or the result is an array. */
 export function evalExpr(src: string, resolve: Resolver): number {
   try {
-    return ev(parseCached(src), resolve);
+    const v = ev(parseCached(src), resolve);
+    return typeof v === 'number' ? v : NaN;
   } catch {
     return NaN;
   }
@@ -255,6 +334,8 @@ export function collectRefs(src: string): RefLite[] {
       case 'bin': walk(n.a); walk(n.b); break;
       case 'tern': walk(n.c); walk(n.a); walk(n.b); break;
       case 'call': n.args.forEach(walk); break;
+      case 'arr': n.items.forEach(walk); break;
+      case 'index': walk(n.a); walk(n.i); break;
     }
   };
   walk(root);

web/src/lib/flowDebug.ts

@@ -19,19 +19,28 @@ export interface NodeDebugState {
 /** Per-node debug state, keyed by node id. */
 export type DebugSnapshot = Map<string, NodeDebugState>;
 
+/** Compact string for a raw value — used in badges and tooltips. */
+export function fmtBadge(v: unknown): string {
+  if (Array.isArray(v)) {
+    const head = v.slice(0, 3).map(x => Array.isArray(x) ? '[…]' : String(x)).join(', ');
+    return `[${head}${v.length > 3 ? ', …' : ''}](n=${v.length})`;
+  }
+  if (typeof v === 'number') {
+    if (!isFinite(v)) return String(v);
+    if (Number.isInteger(v)) return String(v);
+    return String(+v.toFixed(4));
+  }
+  return String(v);
+}
+
 /** Round-trips a value into a compact label for the on-node badge. */
 export function formatBadge(s: NodeDebugState | undefined): string {
   if (!s) return '';
   if (s.error) return '!';
   const v = s.value;
   if (v == null) return '—';
-  if (Array.isArray(v)) return `[${v.length}]`;
-  if (typeof v === 'number') {
-    if (!isFinite(v)) return String(v);
-    if (Number.isInteger(v)) return String(v);
-    return v.toPrecision(4).replace(/\.?0+$/, '');
-  }
   if (typeof v === 'boolean') return v ? 'true' : 'false';
+  if (Array.isArray(v) || typeof v === 'number') return fmtBadge(v);
   const str = String(v);
   return str.length > 10 ? str.slice(0, 9) + '…' : str;
 }

web/src/lib/localstate.ts

@@ -11,9 +11,15 @@
 
 import { writable, type Readable, type Writable } from './store';
 import type { SignalValue, SignalMeta, StateVar } from './types';
+import { parseInitialArray, applySizing, type ArrVal } from './arraypolicy';
 
 const valueStores = new Map<string, Writable<SignalValue>>();
 const metaStores = new Map<string, Writable<SignalMeta | null>>();
+const decls = new Map<string, StateVar>();
+
+export function declaredVar(name: string): StateVar | undefined {
+  return decls.get(name);
+}
 
 const DEFAULT_VALUE: SignalValue = { value: null, quality: 'unknown', ts: null };
 
@@ -42,6 +48,8 @@ function coerce(v: StateVar): any {
       return v.initial === 'true' || v.initial === '1';
     case 'string':
       return v.initial;
+    case 'array':
+      return parseInitialArray(v);
     default: {
       const n = parseFloat(v.initial);
       return isNaN(n) ? 0 : n;
@@ -53,6 +61,7 @@ function coerce(v: StateVar): any {
 // publishes metadata. Call this whenever a panel is loaded.
 export function initLocalState(vars: StateVar[] | undefined): void {
   for (const v of vars ?? []) {
+    decls.set(v.name, v);
     valueW(v.name).set({
       value: coerce(v),
       quality: 'good',
@@ -64,6 +73,9 @@ export function initLocalState(vars: StateVar[] | undefined): void {
       displayLow: v.low ?? 0,
       displayHigh: v.high ?? 100,
       writable: true,
+      elem: v.elem,
+      sizing: v.sizing,
+      capacity: v.capacity,
     });
   }
 }
@@ -77,6 +89,11 @@ export function getLocalMetaStore(name: string): Readable<SignalMeta | null> {
 }
 
 // writeLocalState updates a local variable's live value in place.
+// When the declared variable is an array type, the written value is passed
+// through applySizing to enforce the declared sizing policy.
 export function writeLocalState(name: string, value: any): void {
-  valueW(name).set({ value, quality: 'good', ts: new Date().toISOString() });
+  const sv = decls.get(name);
+  let v = value;
+  if (sv?.type === 'array' && Array.isArray(value)) v = applySizing(value as ArrVal[], sv);
+  valueW(name).set({ value: v, quality: 'good', ts: new Date().toISOString() });
 }

web/src/lib/logic.ts

@@ -12,8 +12,8 @@
 //   flow.loop   — repeats the 'body' port (count / while, capped), then 'done'.
 //   action.write— evaluates `expr` and writes the result to `target`.
 //   action.delay— awaits `ms` before continuing.
-//   action.accumulate / export / clear — collect expression values into a named
-//                 in-memory array and download it as CSV.
+//   action.array.* — push/set/remove/pop/clear on a named array local variable.
+//   action.export— download named array local variables as CSV (one col each).
 //   action.log  — logs an expression value to the console.
 //
 // Expressions reference signals inline as {ds:name} and panel-local vars as
@@ -28,8 +28,10 @@ import { wsClient } from './ws';
 import { getSignalStore } from './stores';
 import { writable } from './store';
 import { setWidgetDisabled, setWidgetHidden, setPlotPaused, clearPlot, resetWidgetCmds } from './widgetCommands';
-import type { SignalRef, SignalValue, LogicGraph, LogicNode } from './types';
-import { evalExpr, evalBool, collectRefs, type Resolver } from './expr';
+import type { SignalRef, SignalValue, LogicGraph, LogicNode, StateVar } from './types';
+import { evalExpr, evalBool, collectRefs, evalValue, type Resolver } from './expr';
+import { getLocalValueStore, writeLocalState, declaredVar } from './localstate';
+import { applySizing, type ArrVal } from './arraypolicy';
 
 // A single row in a dialog: either an `input` (prompts the operator for a value
 // that is later written to its target) or a `display` (a read-only live value
@@ -177,27 +179,34 @@ interface DialogFieldSpec {
   expr?: string;    // display: expression evaluated and shown
 }
 
-// Linearly interpolate a value at time `t` from timestamp-sorted samples. Returns
-// null when `t` falls outside the samples' own time range (no extrapolation).
-function interpAt(samples: Array<{ t: number; v: number }>, t: number): number | null {
-  const n = samples.length;
-  if (n === 0 || t < samples[0].t || t > samples[n - 1].t) return null;
-  for (let i = 0; i < n - 1; i++) {
-    const a = samples[i], b = samples[i + 1];
-    if (t >= a.t && t <= b.t) {
-      if (b.t === a.t) return a.v;
-      return a.v + (b.v - a.v) * (t - a.t) / (b.t - a.t);
-    }
-  }
-  return samples[n - 1].v;
-}
-
 // Escape a CSV cell: quote and double inner quotes when it contains a comma,
 // quote, or newline.
 function csvEsc(s: string): string {
   return /[",\n]/.test(s) ? '"' + s.replace(/"/g, '""') + '"' : s;
 }
 
+// Read the current array value of a local state variable. Returns an empty
+// array if the variable doesn't exist or holds a non-array value.
+function curArray(name: string): ArrVal[] {
+  const store = getLocalValueStore(name) as { get?: () => { value: any } };
+  const sv = typeof store.get === 'function' ? store.get() : null;
+  const v = sv?.value;
+  return Array.isArray(v) ? (v as ArrVal[]) : [];
+}
+
+// Nested index assignment: sets arr[path[0]][path[1]]...[path[n-1]] = v.
+// Negative indices are resolved relative to the current sub-array length.
+function setPath(arr: ArrVal[], path: number[], v: ArrVal): void {
+  let cur: ArrVal[] = arr;
+  for (let d = 0; d < path.length - 1; d++) {
+    let k = path[d]; if (k < 0) k = cur.length + k;
+    if (!Array.isArray(cur[k])) cur[k] = [];
+    cur = cur[k] as ArrVal[];
+  }
+  let last = path[path.length - 1]; if (last < 0) last = cur.length + last;
+  cur[last] = v;
+}
+
 interface WireOut { to: string; port: string }
 // One flow run, started by an activating trigger. `dt` is the seconds elapsed
 // since that trigger last fired (0 on its first fire); `resolve` is an
@@ -220,9 +229,6 @@ export class LogicEngine {
   private prevVal = new Map<string, any>();
   // signal key → trigger node ids that react to it (threshold / change).
   private watchers = new Map<string, string[]>();
-  // Named in-memory data arrays, filled by action.accumulate and dumped by
-  // action.export. Each sample keeps the wall-clock time it was recorded.
-  private arrays = new Map<string, Array<{ t: number; v: number }>>();
   // Wall-clock time (ms) each trigger last activated, for the {sys:dt} signal.
   private lastFire = new Map<string, number>();
   private cleanups: Array<() => void> = [];
@@ -349,7 +355,6 @@ export class LogicEngine {
     this.prevBool = new Map();
     this.prevVal = new Map();
     this.watchers = new Map();
-    this.arrays = new Map();
     this.lastFire = new Map();
     this.debugStates = new Map();
     // Restore every widget to its default state so reopening a panel (whose
@@ -393,8 +398,14 @@ export class LogicEngine {
         case 'flow.if':         collectRefs(node.params.cond ?? '').forEach(want); break;
         case 'flow.loop':       if ((node.params.mode ?? 'count') === 'while') collectRefs(node.params.cond ?? '').forEach(want); break;
         case 'action.write':
-        case 'action.accumulate':
+        case 'action.array.push':
         case 'action.log':      collectRefs(node.params.expr ?? '').forEach(want); break;
+        case 'action.array.set':
+          collectRefs(node.params.expr ?? '').forEach(want);
+          String(node.params.index ?? '').split(',').forEach(s => collectRefs(s.trim()).forEach(want));
+          break;
+        case 'action.array.remove':
+          collectRefs(node.params.index ?? '').forEach(want); break;
         case 'action.config.apply':
         case 'action.config.read':
         case 'action.config.write': {
@@ -611,27 +622,71 @@ export class LogicEngine {
         await this.follow(node.id, 'out', ctx);
         return;
 
-      case 'action.accumulate': {
+      // ── Array action nodes ──────────────────────────────────────────────────
+
+      case 'action.array.push': {
         const name = (node.params.array ?? '').trim();
-        const val = evalExpr(node.params.expr ?? '', ctx.resolve);
+        if (name) {
+          const val = evalValue(node.params.expr ?? '', ctx.resolve);
           this.markActive(node.id, val);
-        if (name && !isNaN(val)) {
-          const arr = this.arrays.get(name) ?? this.arrays.set(name, []).get(name)!;
-          arr.push({ t: Date.now(), v: val });
+          writeLocalState(name, [...curArray(name), val]);
+        }
+        await this.follow(node.id, 'out', ctx);
+        return;
+      }
+
+      case 'action.array.set': {
+        const name = (node.params.array ?? '').trim();
+        if (name) {
+          const arr = curArray(name).slice();
+          const path = String(node.params.index ?? '').split(',')
+            .map(s => Math.trunc(evalExpr(s.trim(), ctx.resolve)));
+          const val = evalValue(node.params.expr ?? '', ctx.resolve);
+          this.markActive(node.id, val);
+          if (path.length > 0 && path.every(i => !isNaN(i))) setPath(arr, path, val);
+          writeLocalState(name, arr);
+        }
+        await this.follow(node.id, 'out', ctx);
+        return;
+      }
+
+      case 'action.array.remove': {
+        const name = (node.params.array ?? '').trim();
+        if (name) {
+          const arr = curArray(name).slice();
+          const i = Math.trunc(evalExpr(node.params.index ?? '0', ctx.resolve));
+          const k = i < 0 ? arr.length + i : i;
+          if (k >= 0 && k < arr.length) arr.splice(k, 1);
+          this.markActive(node.id, k);
+          writeLocalState(name, arr);
+        }
+        await this.follow(node.id, 'out', ctx);
+        return;
+      }
+
+      case 'action.array.pop': {
+        const name = (node.params.array ?? '').trim();
+        if (name) {
+          const arr = curArray(name).slice();
+          arr.pop();
+          writeLocalState(name, arr);
+        }
+        await this.follow(node.id, 'out', ctx);
+        return;
+      }
+
+      case 'action.array.clear': {
+        const name = (node.params.array ?? '').trim();
+        if (name) {
+          const sv = declaredVar(name);
+          writeLocalState(name, sv ? applySizing([], sv) : []);
         }
         await this.follow(node.id, 'out', ctx);
         return;
       }
 
       case 'action.export': {
-        if (!this.dryRun) this.exportArrays(this.exportColumns(node), node.params.align ?? 'common', node.params.filename ?? '');
-        await this.follow(node.id, 'out', ctx);
-        return;
-      }
-
-      case 'action.clear': {
-        const name = (node.params.array ?? '').trim();
-        if (name) this.arrays.delete(name);
+        if (!this.dryRun) this.exportArrays(this.exportColumns(node), node.params.filename ?? '');
         await this.follow(node.id, 'out', ctx);
         return;
       }
@@ -704,8 +759,9 @@ export class LogicEngine {
     }
   }
 
-  // The columns an action.export node should emit. Reads the JSON `columns`
-  // param (a list of { array, label }); falls back to the legacy single `array`.
+  // The columns an action.export node should emit, read from the JSON `columns`
+  // param (a list of { array, label }). Legacy single-`array` nodes are migrated
+  // to this form on load (see xml.ts migrateLegacyArrayNode).
   private exportColumns(node: LogicNode): Array<{ array: string; label: string }> {
     const raw = (node.params.columns ?? '').trim();
     if (raw) {
@@ -718,47 +774,24 @@ export class LogicEngine {
         }
       } catch {}
     }
-    const a = (node.params.array ?? '').trim();
-    return a ? [{ array: a, label: a }] : [];
+    return [];
   }
 
-  // Dump one or more named arrays to a CSV the browser downloads. Each column is
-  // a captured array; rows are keyed by sample timestamp. `align` controls how
-  // arrays with differing timestamps are combined:
-  //   common      — only timestamps present in every array (intersection).
-  //   any         — the union of all timestamps; cells with no sample are blank.
-  //   interpolate — the union of all timestamps; a missing cell is linearly
-  //                 interpolated between the array's surrounding samples (blank
-  //                 outside the array's own time range).
-  private exportArrays(cols: Array<{ array: string; label: string }>, align: string, filename: string): void {
+  // Dump one or more named array locals to a CSV the browser downloads.
+  // Rows are index-aligned: row r contains col[r] for each column; cells with
+  // no value at that index are blank. The header row uses the column's custom
+  // label (or its array name as fallback).
+  private exportArrays(cols: Array<{ array: string; label: string }>, filename: string): void {
     if (cols.length === 0) return;
-    const series = cols.map((c, i) => ({
-      label: c.label || c.array || `col${i + 1}`,
-      samples: (this.arrays.get(c.array) ?? []).slice().sort((a, b) => a.t - b.t),
-      map: new Map<number, number>(),
-    }));
-    for (const s of series) for (const p of s.samples) s.map.set(p.t, p.v);
-
-    const tsSet = new Set<number>();
-    for (const s of series) for (const p of s.samples) tsSet.add(p.t);
-    let times = Array.from(tsSet).sort((a, b) => a - b);
-    if (align === 'common') times = times.filter(t => series.every(s => s.map.has(t)));
-
-    const cell = (s: typeof series[number], t: number): string => {
-      const exact = s.map.get(t);
-      if (exact !== undefined) return String(exact);
-      if (align === 'interpolate') {
-        const v = interpAt(s.samples, t);
-        return v === null ? '' : String(v);
+    const data = cols.map(c => curArray(c.array));
+    const rows = Math.max(0, ...data.map(d => d.length));
+    const header = cols.map((c, i) => csvEsc(c.label || c.array || `col${i + 1}`)).join(',');
+    const lines = [header];
+    for (let r = 0; r < rows; r++) {
+      lines.push(data.map(d => (r < d.length ? csvEsc(String(d[r])) : '')).join(','));
     }
-      return ''; // 'any' (and 'common' never reaches here)
-    };
-
-    const header = ['timestamp_ms', 'iso', ...series.map(s => s.label)];
-    const rows = times.map(t => [String(t), new Date(t).toISOString(), ...series.map(s => cell(s, t))]);
-    const csv = [header, ...rows].map(r => r.map(csvEsc).join(',')).join('\n') + '\n';
-
-    const base = filename || series.map(s => s.label).join('_') || 'export';
+    const csv = lines.join('\n') + '\n';
+    const base = filename || cols.map(c => c.label || c.array).join('_') || 'export';
     const safe = base.replace(/[^a-z0-9_.-]/gi, '_');
     const fname = safe.toLowerCase().endsWith('.csv') ? safe : `${safe}.csv`;
     const blob = new Blob([csv], { type: 'text/csv' });
@@ -855,3 +888,30 @@ export class LogicEngine {
 
 // Singleton instance, mirrored on wsClient's module-level pattern.
 export const logicEngine = new LogicEngine();
+
+// ensureArrayDecls scans a LogicGraph for array references in accumulate /
+// clear / array.* / export nodes and auto-declares any that are not already
+// present in `vars` as dynamic numeric array locals. Call this before
+// initLocalState so that auto-declared arrays are initialised on panel load.
+export function ensureArrayDecls(graph: LogicGraph | undefined, vars: StateVar[]): StateVar[] {
+  if (!graph) return vars;
+  const have = new Set(vars.map(v => v.name));
+  const out = vars.slice();
+  const need = (name: string) => {
+    if (name && !have.has(name)) {
+      have.add(name);
+      out.push({ name, type: 'array', elem: 'number', sizing: 'dynamic', initial: '' });
+    }
+  };
+  for (const n of graph.nodes) {
+    if (n.kind.startsWith('action.array.')) {
+      need((n.params.array ?? '').trim());
+    }
+    if (n.kind === 'action.export') {
+      try {
+        (JSON.parse(n.params.columns || '[]') as any[]).forEach(c => need(String(c?.array ?? '').trim()));
+      } catch {}
+    }
+  }
+  return out;
+}

web/src/lib/types.ts

@@ -28,6 +28,10 @@ export interface SignalMeta {
   description?: string;
   properties?: Record<string, string>;
   tags?: string[];
+  // array-local extra fields (present when type === 'array'):
+  elem?: 'number' | 'bool' | 'array';
+  sizing?: 'dynamic' | 'capped' | 'fixed';
+  capacity?: number;
 }
 
 // A single widget in an interface
@@ -68,11 +72,15 @@ export type PlotLayout =
 // via ds 'local'.
 export interface StateVar {
   name: string;
-  type?: 'number' | 'bool' | 'string'; // default 'number'
+  type?: 'number' | 'bool' | 'string' | 'array'; // default 'number'
   initial: string;                     // initial value, stored as a string
   unit?: string;
   low?: number;
   high?: number;
+  // array-only (present when type === 'array'):
+  elem?: 'number' | 'bool' | 'array';
+  sizing?: 'dynamic' | 'capped' | 'fixed';
+  capacity?: number;
 }
 
 // ── Panel logic (Node-RED–style flow graph) ──────────────────────────────────
@@ -107,13 +115,14 @@ export interface StateVar {
 //   action.write      — evaluate `expr` and write the result to `target`
 //                       ("ds:name" or a bare local var) (params: target, expr).
 //   action.delay      — pause `ms` before continuing downstream (params: ms).
-//   action.accumulate — evaluate `expr` and append the value (with a timestamp)
-//                       to the named in-memory data array (params: array, expr).
-//   action.export     — download one or more named arrays as a CSV file, one
-//                       column per array (params: columns = JSON list of
-//                       {array,label}, align 'common'|'any'|'interpolate',
+//   action.export     — download one or more named array local variables as a
+//                       CSV file, one column per array (params: columns = JSON
+//                       list of {array,label}, align 'common'|'any'|'interpolate',
 //                       filename). Legacy single-array nodes use `array`.
-//   action.clear      — empty the named array (params: array).
+//   action.array.*    — push/set/remove/pop/clear on a named array local variable
+//                       (params: array, plus index/expr where relevant). The old
+//                       action.accumulate / action.clear kinds are migrated to
+//                       action.array.push / action.array.clear on load.
 //   action.log        — evaluate `expr` and log it to the browser console for
 //                       debugging a flow (params: expr, label).
 //   action.widget     — drive a panel widget by id (params: widget, op). `op` is
@@ -148,14 +157,17 @@ export type LogicNodeKind =
   | 'flow.loop'
   | 'action.write'
   | 'action.delay'
-  | 'action.accumulate'
   | 'action.export'
-  | 'action.clear'
   | 'action.log'
   | 'action.widget'
   | 'action.dialog.info'
   | 'action.dialog.error'
   | 'action.dialog.setpoint'
+  | 'action.array.push'
+  | 'action.array.set'
+  | 'action.array.remove'
+  | 'action.array.pop'
+  | 'action.array.clear'
   | 'action.config.apply'
   | 'action.config.read'
   | 'action.config.write'

web/src/lib/xml.ts

@@ -73,6 +73,11 @@ export function serializeInterface(iface: Interface): string {
     if (sv.unit) attrs.push(`unit="${xmlEsc(sv.unit)}"`);
     if (sv.low !== undefined) attrs.push(`low="${sv.low}"`);
     if (sv.high !== undefined) attrs.push(`high="${sv.high}"`);
+    if (sv.type === 'array') {
+      if (sv.elem) attrs.push(`elem="${sv.elem}"`);
+      if (sv.sizing) attrs.push(`sizing="${sv.sizing}"`);
+      if (sv.capacity !== undefined) attrs.push(`capacity="${sv.capacity}"`);
+    }
     lines.push(`  <statevar ${attrs.join(' ')}/>`);
   }
   if (iface.logic && (iface.logic.nodes.length > 0 || iface.logic.wires.length > 0)) {
@@ -123,6 +128,31 @@ function parseLayout(el: Element): PlotLayout {
   return { type: 'split', dir, ratio: isNaN(ratio) ? 0.5 : ratio, a, b };
 }
 
+// Rewrite a legacy array node kind to its current equivalent, mutating `params`
+// in place. The old action.accumulate / action.clear kinds (and the legacy
+// single-`array` form of action.export) predate the typed array local-variable
+// nodes; old panels are migrated transparently on load so the editor only ever
+// sees the current kinds.
+function migrateLegacyArrayNode(
+  kind: string,
+  params: Record<string, string>,
+  setKind: (k: LogicGraph['nodes'][number]['kind']) => void,
+): void {
+  if (kind === 'action.accumulate') {
+    setKind('action.array.push'); // same params: { array, expr }
+  } else if (kind === 'action.clear') {
+    setKind('action.array.clear'); // same params: { array }
+  } else if (kind === 'action.export') {
+    // Legacy single-array export had only an `array` param; fold it into the
+    // current JSON `columns` form so the editor never sees the legacy field.
+    const a = (params.array ?? '').trim();
+    if (a && !(params.columns ?? '').trim()) {
+      params.columns = JSON.stringify([{ array: a, label: '' }]);
+    }
+    delete params.array;
+  }
+}
+
 /** Parse a <logic> element into a LogicGraph (nodes + wires). */
 function parseLogic(logicEl: Element): LogicGraph {
   const nodes: LogicGraph['nodes'] = [];
@@ -155,9 +185,11 @@ function parseLogic(logicEl: Element): LogicGraph {
         const value = child.getAttribute('value');
         if (key !== null && value !== null) params[key] = value;
       }
+      let kind = (el.getAttribute('kind') ?? 'action.write') as LogicGraph['nodes'][number]['kind'];
+      migrateLegacyArrayNode(kind, params, (k) => { kind = k; });
       nodes.push({
         id,
-        kind: (el.getAttribute('kind') ?? 'action.write') as LogicGraph['nodes'][number]['kind'],
+        kind,
         x: parseFloat(el.getAttribute('x') ?? '0'),
         y: parseFloat(el.getAttribute('y') ?? '0'),
         params,
@@ -213,13 +245,21 @@ export function parseInterface(xml: string): Interface {
     const low = el.getAttribute('low');
     const high = el.getAttribute('high');
     const unit = el.getAttribute('unit');
+    const elem = el.getAttribute('elem');
+    const sizing = el.getAttribute('sizing');
+    const capacityAttr = el.getAttribute('capacity');
+    const svType: StateVar['type'] =
+      type === 'bool' || type === 'string' || type === 'array' ? type : 'number';
     statevars.push({
       name,
-      type: type === 'bool' || type === 'string' ? type : 'number',
+      type: svType,
       initial: el.getAttribute('initial') ?? '',
       ...(unit ? { unit } : {}),
       ...(low !== null ? { low: parseFloat(low) } : {}),
       ...(high !== null ? { high: parseFloat(high) } : {}),
+      ...(elem ? { elem: elem as StateVar['elem'] } : {}),
+      ...(sizing ? { sizing: sizing as StateVar['sizing'] } : {}),
+      ...(capacityAttr !== null ? { capacity: Number(capacityAttr) } : {}),
     });
   }
 

web/src/widgets/MultiLed.tsx

@@ -1,7 +1,7 @@
 import { h } from 'preact';
 import { useState, useEffect } from 'preact/hooks';
-import { getSignalStore } from '../lib/stores';
-import type { Widget, SignalValue } from '../lib/types';
+import { getSignalStore, getMetaStore } from '../lib/stores';
+import type { Widget, SignalValue, SignalMeta } from '../lib/types';
 
 const DEFAULT_VALUE: SignalValue = { value: null, quality: 'unknown', ts: null };
 
@@ -14,13 +14,16 @@ interface Props { widget: Widget; onContextMenu?: (e: MouseEvent) => void; }
 export default function MultiLed({ widget, onContextMenu }: Props) {
   const sigRef = widget.signals[0];
   const [sv, setSv] = useState<SignalValue>(DEFAULT_VALUE);
+  const [meta, setMeta] = useState<SignalMeta | null>(null);
 
   useEffect(() => {
     if (!sigRef) return;
-    const unsub = getSignalStore(sigRef).subscribe(setSv);
-    return unsub;
+    const uv = getSignalStore(sigRef).subscribe(setSv);
+    const um = getMetaStore(sigRef).subscribe(setMeta);
+    return () => { uv(); um(); };
   }, [sigRef?.ds, sigRef?.name]);
 
+  const sourceMode = widget.options['sourceMode'] ?? 'bitset';
   const bits = parseInt(widget.options['bits'] ?? '8', 10);
   const labelsRaw = widget.options['labels'] ?? '';
   const colorsTrueRaw = widget.options['colorsTrue'] ?? '';
@@ -32,8 +35,49 @@ export default function MultiLed({ widget, onContextMenu }: Props) {
 
   const quality = sv.quality;
   const isUncertain = quality === 'uncertain' || quality === 'unknown';
-
   const rawV = sv.value;
+
+  // ── Array source mode ──────────────────────────────────────────────────────
+  // When sourceMode === 'array' (or the bound value is already an array), render
+  // one LED per element.  LED count tracks the live array length.
+  // When meta.elem === 'bool', the on/off labels from labelArr are used as-is.
+  const isArrayMode = sourceMode === 'array' || Array.isArray(rawV);
+
+  if (isArrayMode) {
+    const arr: any[] = Array.isArray(rawV) ? rawV : [];
+    const isBoolElem = meta?.elem === 'bool';
+
+    return (
+      <div
+        class="multiled-widget"
+        style={`left:${widget.x}px;top:${widget.y}px;width:${widget.w}px;height:${widget.h}px;`}
+        onContextMenu={onContextMenu}
+      >
+        {arr.map((elem, i) => {
+          const on = isBoolElem ? Boolean(elem) : (Number(elem) !== 0 && elem !== false && elem !== null);
+          const trueColor = colorsTrueArr[i] ?? colorsTrueArr[0] ?? '#22c55e';
+          const falseColor = colorsFalseArr[i] ?? colorsFalseArr[0] ?? '#ef4444';
+          const color = on ? trueColor : falseColor;
+          // Label: per-element override, then generic index
+          const elemLabel = labelArr[i] ?? String(i);
+          return (
+            <div key={i} class="bit-item">
+              <div
+                class={`led-circle${isUncertain ? ' blink' : ''}`}
+                style={`background:${color};box-shadow:0 0 6px ${color}88;`}
+              />
+              <div class="bit-label">{elemLabel}</div>
+            </div>
+          );
+        })}
+        {arr.length === 0 && (
+          <div class="bit-label" style="color:#6b7280;padding:4px">—</div>
+        )}
+      </div>
+    );
+  }
+
+  // ── Bitset source mode (default) ───────────────────────────────────────────
   const intValue = rawV === null || rawV === undefined ? 0
     : typeof rawV === 'number' ? Math.floor(rawV) : parseInt(String(rawV), 10);
 

web/src/widgets/PlotWidget.tsx

@@ -406,7 +406,13 @@ export default function PlotWidget({ widget, onContextMenu, timeRange }: Props)
         ? { top: legendPos === 'top' ? 0 : 'bottom', textStyle: { color: '#94a3b8' } }
         : undefined;
 
-      switch (plotType) {
+      // If any signal has delivered an array value (stored in waveforms[]),
+      // render all signals as waveform traces regardless of the configured plotType.
+      // This handles local array vars and EPICS waveform PVs transparently.
+      const hasWaveformData = waveforms.some(w => w.length > 0);
+      const effectivePlotType = hasWaveformData ? 'waveform' : plotType;
+
+      switch (effectivePlotType) {
         case 'histogram': {
           // Distribution over all buffered samples (ring-buffer bounded).
           const { labels, counts } = buildHistogram(buffers.map(b => b.values));
@@ -664,14 +670,25 @@ 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 === 'waveform') {
-          // Array-valued sample: keep only the latest waveform and redraw.
+        // Array-valued signal (EPICS waveform or local array var): always route
+        // through the waveform sample path.  Nested (2-D) arrays are skipped —
+        // they fall through to the "unsupported" ECharts placeholder.
         if (Array.isArray(sv.value)) {
-            waveforms[i] = sv.value.map((x: any) => typeof x === 'number' ? x : parseFloat(String(x)));
-          } else {
+          const flat = sv.value as any[];
+          // Skip 2-D (nested) arrays — not renderable as a simple waveform.
+          if (flat.length > 0 && Array.isArray(flat[0])) {
+            if (echart) echart.setOption(echartsOption(), { notMerge: true });
+            return;
+          }
+          waveforms[i] = flat.map((x: any) => typeof x === 'number' ? x : parseFloat(String(x)));
+          if (echart) echart.setOption(echartsOption(), { notMerge: true });
+          return;
+        }
+
+        if (plotType === 'waveform') {
+          // Scalar sample while in waveform mode: treat as a single-element waveform.
           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));

web/src/widgets/TableWidget.tsx

@@ -81,6 +81,80 @@ function TableRow({ sig, label, cols, fmt, unitOverride }: RowProps) {
   );
 }
 
+interface ArrayBodyProps {
+  sig: SignalRef;
+  cols: Col[];
+  fmt: string;
+  unitOverride: string;
+  // For 2-D arrays: map column positions to inner-array indices.
+  // e.g. "0,2" means col[0] → elem[0], col[1] → elem[2]
+  colIndices?: number[];
+}
+
+// Array source mode body: subscribe to a single signal whose value is an array
+// and render one row per element.  For 2-D (elem:'array') arrays, each row is
+// the outer index and configured colIndices map columns to inner positions.
+// Returns an array of <tr> elements (no wrapper needed — inserted into <tbody>).
+function ArrayTableBody({ sig, cols, fmt, unitOverride, colIndices }: ArrayBodyProps) {
+  const [sv, setSv] = useState<SignalValue>(DEFAULT_VALUE);
+  const [meta, setMeta] = useState<SignalMeta | null>(null);
+
+  useEffect(() => {
+    const uv = getSignalStore(sig).subscribe(setSv);
+    const um = getMetaStore(sig).subscribe(setMeta);
+    return () => { uv(); um(); };
+  }, [sig.ds, sig.name]);
+
+  const unit = unitOverride === 'none' ? '' : (unitOverride || meta?.unit || '');
+  const time = sv.ts ? new Date(sv.ts).toLocaleTimeString() : '';
+  const quality = sv.quality;
+
+  const rawArr: any[] = Array.isArray(sv.value) ? sv.value : [];
+  const is2D = meta?.elem === 'array';
+
+  if (rawArr.length === 0) {
+    return <tr><td class="tw-empty" colSpan={cols.length}>—</td></tr>;
+  }
+
+  // Return an array of <tr> elements — JSX arrays are valid react-mode children.
+  return rawArr.map((elem, idx) => {
+    const cells = cols.map((c, ci) => {
+      switch (c) {
+        case 'name':
+          return <td key={c} class="tw-name">{idx}</td>;
+        case 'value': {
+          let display: string;
+          if (is2D && Array.isArray(elem)) {
+            // 2-D: show the inner element at the configured column index mapping.
+            const innerIdx = colIndices ? (colIndices[ci] ?? ci) : ci;
+            const inner = (elem as any[])[innerIdx];
+            display = inner === undefined ? '—'
+              : typeof inner === 'number' ? formatValue(inner, fmt) : String(inner);
+          } else if (typeof elem === 'number') {
+            display = formatValue(elem, fmt);
+          } else if (elem === null || elem === undefined) {
+            display = '—';
+          } else {
+            display = String(elem);
+          }
+          return <td key={c} class="tw-value">{display}</td>;
+        }
+        case 'unit':
+          return <td key={c} class="tw-unit">{unit}</td>;
+        case 'quality':
+          return (
+            <td key={c} class="tw-quality">
+              <span class="quality-dot" style={`background:${qualityColor(quality)};`} title={`Quality: ${quality}`} />
+            </td>
+          );
+        case 'time':
+          return <td key={c} class="tw-time">{time}</td>;
+      }
+    });
+    return <tr key={idx}>{cells}</tr>;
+  }) as any;
+}
+
 interface Props { widget: Widget; onContextMenu?: (e: MouseEvent) => void; }
 
 // A tabular multi-signal readout: each bound signal is one row, with a
@@ -95,6 +169,14 @@ export default function TableWidget({ widget, onContextMenu }: Props) {
   const fmt = o['format'] ?? '';
   const unitOverride = o['unit'] ?? '';
   const labels = (o['labels'] ?? '').split(',');
+  // sourceMode:'array' — use first bound signal as an array; each element = one row.
+  const sourceMode = o['sourceMode'] ?? '';
+  const isArrayMode = sourceMode === 'array';
+  // colIndices: for 2-D arrays, map column positions to inner-array positions.
+  // Stored as a comma-separated list of integers, e.g. "0,2,4".
+  const colIndices = o['colIndices']
+    ? o['colIndices'].split(',').map(s => parseInt(s.trim(), 10)).filter(n => !isNaN(n))
+    : undefined;
 
   return (
     <div
@@ -113,6 +195,15 @@ export default function TableWidget({ widget, onContextMenu }: Props) {
           <tbody>
             {widget.signals.length === 0 ? (
               <tr><td class="tw-empty" colSpan={cols.length}>No signals — drop signals here</td></tr>
+            ) : isArrayMode && widget.signals[0] ? (
+              // Array source mode: first signal's array value → one row per element.
+              <ArrayTableBody
+                sig={widget.signals[0]}
+                cols={cols}
+                fmt={fmt}
+                unitOverride={unitOverride}
+                colIndices={colIndices}
+              />
             ) : (
               widget.signals.map((s, i) => (
                 <TableRow