diff --git a/Common/Client/go/wshub/hub.go b/Common/Client/go/wshub/hub.go
index 833ffa3..a67f609 100644
--- a/Common/Client/go/wshub/hub.go
+++ b/Common/Client/go/wshub/hub.go
@@ -239,6 +239,10 @@ type Hub struct {
 
 	sm *SourceManager // set after construction; used for WS-initiated source changes
 
+	// cal holds the per-signal calibration table.  It is metadata only: the
+	// rings, the history and the trigger comparator all keep raw samples.
+	cal *calTable
+
 	// Ring buffers for hi-res zoom data.
 	// ringsMu protects the map structure; each sigRing has its own RWMutex for data.
 	ringsMu sync.RWMutex
@@ -270,6 +274,7 @@ func NewHub() *Hub {
 		rings:       make(map[string]*sigRing),
 		statsMap:    make(map[string]*SourceStat),
 		trigger:     newTriggerEngine(),
+		cal:         newCalTable(),
 	}
 }
 
diff --git a/Common/Client/go/wshub/sources.go b/Common/Client/go/wshub/sources.go
index c5f04b8..23a6e77 100644
--- a/Common/Client/go/wshub/sources.go
+++ b/Common/Client/go/wshub/sources.go
@@ -1,12 +1,12 @@
 package wshub
 
 import (
-	"encoding/json"
 	"fmt"
 	"io"
 	"log"
 	"net"
 	"os"
+	"sort"
 	"strconv"
 	"strings"
 	"sync"
@@ -95,11 +95,16 @@ func (sm *SourceManager) Remove(id string) {
 	}
 }
 
-// Save writes the current source list to filePath.
-func (sm *SourceManager) Save() error {
-	if sm.filePath == "" {
-		return fmt.Errorf("no sources-file configured")
-	}
+// Path returns the configured config-file path ("" when none).
+func (sm *SourceManager) Path() string {
+	sm.mu.RLock()
+	defer sm.mu.RUnlock()
+	return sm.filePath
+}
+
+// snapshotSources returns the current sources sorted by label, so the written
+// file is byte-stable across runs (the map iteration order is not).
+func (sm *SourceManager) snapshotSources() []SourceConfig {
 	sm.mu.RLock()
 	cfgs := make([]SourceConfig, 0, len(sm.sources))
 	for _, ms := range sm.sources {
@@ -111,26 +116,86 @@ func (sm *SourceManager) Save() error {
 		})
 	}
 	sm.mu.RUnlock()
+	sort.Slice(cfgs, func(i, j int) bool {
+		if cfgs[i].Label != cfgs[j].Label {
+			return cfgs[i].Label < cfgs[j].Label
+		}
+		return cfgs[i].Addr < cfgs[j].Addr
+	})
+	return cfgs
+}
 
-	data, err := json.MarshalIndent(cfgs, "", "  ")
+// Save writes the current source list and calibration table to filePath as one
+// flat JSON array.
+func (sm *SourceManager) Save() error {
+	path := sm.Path()
+	if path == "" {
+		return fmt.Errorf("no sources-file configured")
+	}
+	data, err := encodeConfigFile(sm.snapshotSources(), sm.hub.cal.List())
 	if err != nil {
 		return err
 	}
-	return os.WriteFile(sm.filePath, data, 0644)
+	return os.WriteFile(path, data, 0644)
 }
 
-// Load reads sources from path and adds them.
+// Load reads the config file at path, replaces the calibration table with its
+// contents and starts every source it lists.
 func (sm *SourceManager) Load(path string) error {
 	data, err := os.ReadFile(path)
 	if err != nil {
 		return err
 	}
-	var cfgs []SourceConfig
-	if err := json.Unmarshal(data, &cfgs); err != nil {
+	srcs, cals, err := parseConfigFile(data)
+	if err != nil {
 		return err
 	}
+	sm.mu.Lock()
 	sm.filePath = path
-	for _, cfg := range cfgs {
+	sm.mu.Unlock()
+
+	sm.hub.cal.Replace(cals)
+	for _, cfg := range srcs {
+		sm.Add(cfg.Label, cfg.Addr, cfg.MulticastGroup, cfg.DataPort)
+	}
+	return nil
+}
+
+// Reload re-reads the config file.  The calibration table is replaced wholesale
+// and sources listed in the file that are not already running are started; no
+// live source is ever stopped, restarted or reconnected, because a reload must
+// not interrupt streaming.  The asymmetry is deliberate: calibration is cheap
+// to reapply, a source is a live UDP session.
+func (sm *SourceManager) Reload() error {
+	path := sm.Path()
+	if path == "" {
+		return fmt.Errorf("no sources-file configured")
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return err
+	}
+	srcs, cals, err := parseConfigFile(data)
+	if err != nil {
+		return err
+	}
+	sm.hub.cal.Replace(cals)
+
+	sm.mu.RLock()
+	live := make(map[string]bool, len(sm.sources))
+	for _, ms := range sm.sources {
+		live[ms.label+"\x00"+ms.addr] = true
+	}
+	sm.mu.RUnlock()
+
+	for _, cfg := range srcs {
+		label := cfg.Label
+		if label == "" {
+			label = cfg.Addr // Add() applies the same default
+		}
+		if live[label+"\x00"+cfg.Addr] {
+			continue
+		}
 		sm.Add(cfg.Label, cfg.Addr, cfg.MulticastGroup, cfg.DataPort)
 	}
 	return nil
diff --git a/Common/Client/go/wshub/sources_test.go b/Common/Client/go/wshub/sources_test.go
new file mode 100644
index 0000000..ee3c6ae
--- /dev/null
+++ b/Common/Client/go/wshub/sources_test.go
@@ -0,0 +1,131 @@
+package wshub
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// newTestManager builds a hub + manager pair with no goroutines running.
+func newTestManager(t *testing.T) (*Hub, *SourceManager, string) {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "sources.json")
+	h := NewHub()
+	sm := NewSourceManager(h, path)
+	h.SetSourceManager(sm)
+	return h, sm, path
+}
+
+func TestSaveWritesSourcesAndCalibration(t *testing.T) {
+	h, sm, path := newTestManager(t)
+
+	// Register two sources without starting any UDP client.
+	sm.mu.Lock()
+	sm.sources["s1"] = &managedSource{id: "s1", label: "wave", addr: "127.0.0.1:44500"}
+	sm.sources["s2"] = &managedSource{
+		id: "s2", label: "mc", addr: "127.0.0.1:44501",
+		multicastGroup: "239.0.0.1", dataPort: 44502,
+	}
+	sm.mu.Unlock()
+
+	if !h.cal.Set(CalConfig{Source: "wave", Signal: "Adc", Scale: 0.5, Offset: -1.25, Unit: "V"}) {
+		t.Fatal("calibration rejected")
+	}
+	if err := sm.Save(); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("ReadFile: %v", err)
+	}
+	srcs, cals, err := parseConfigFile(data)
+	if err != nil {
+		t.Fatalf("parseConfigFile: %v\n%s", err, data)
+	}
+	if len(srcs) != 2 {
+		t.Fatalf("got %d sources, want 2\n%s", len(srcs), data)
+	}
+	// Save sorts by label so the file is byte-stable across runs.
+	if srcs[0].Label != "mc" || srcs[1].Label != "wave" {
+		t.Errorf("source order = %q,%q, want mc,wave", srcs[0].Label, srcs[1].Label)
+	}
+	if len(cals) != 1 || cals[0].Signal != "Adc" || cals[0].Scale != 0.5 {
+		t.Fatalf("calibration round-trip failed: %+v\n%s", cals, data)
+	}
+}
+
+func TestSaveWithoutFilePathFails(t *testing.T) {
+	h := NewHub()
+	sm := NewSourceManager(h, "")
+	h.SetSourceManager(sm)
+	if err := sm.Save(); err == nil {
+		t.Error("Save() with no path = nil error, want error")
+	}
+}
+
+func TestLoadSeedsCalibrationTable(t *testing.T) {
+	h, sm, path := newTestManager(t)
+	// No "addr" blocks: Load must not start any UDP client during the test.
+	if err := os.WriteFile(path, []byte(`[
+  {"source":"wave","signal":"Adc","scale":0.25,"offset":2,"unit":"mV"},
+  {"source":"wave","signal":"Dac","scale":2}
+]`), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := sm.Load(path); err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	got := h.cal.List()
+	if len(got) != 2 {
+		t.Fatalf("List() = %d entries, want 2", len(got))
+	}
+	if got[0].Signal != "Adc" || got[0].Unit != "mV" || got[0].Offset != 2 {
+		t.Errorf("Adc = %+v", got[0])
+	}
+	if sm.Path() != path {
+		t.Errorf("Path() = %q, want %q", sm.Path(), path)
+	}
+}
+
+func TestReloadReplacesCalibrationAndKeepsLiveSources(t *testing.T) {
+	h, sm, path := newTestManager(t)
+
+	// A live source that the file does not mention must survive the reload.
+	sm.mu.Lock()
+	sm.sources["s1"] = &managedSource{id: "s1", label: "live", addr: "127.0.0.1:44999"}
+	sm.mu.Unlock()
+
+	// A stale calibration that the file does not mention must be dropped.
+	h.cal.Set(CalConfig{Source: "stale", Signal: "Old", Scale: 9})
+
+	if err := os.WriteFile(path, []byte(`[
+  {"source":"wave","signal":"Adc","scale":0.5}
+]`), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := sm.Reload(); err != nil {
+		t.Fatalf("Reload: %v", err)
+	}
+
+	got := h.cal.List()
+	if len(got) != 1 || got[0].Source != "wave" {
+		t.Fatalf("after Reload, calibration = %+v, want only wave/Adc", got)
+	}
+	sm.mu.RLock()
+	_, alive := sm.sources["s1"]
+	n := len(sm.sources)
+	sm.mu.RUnlock()
+	if !alive || n != 1 {
+		t.Errorf("live source count = %d (s1 alive=%v), want 1 / true", n, alive)
+	}
+}
+
+func TestReloadWithoutFilePathFails(t *testing.T) {
+	h := NewHub()
+	sm := NewSourceManager(h, "")
+	h.SetSourceManager(sm)
+	if err := sm.Reload(); err == nil {
+		t.Error("Reload() with no path = nil error, want error")
+	}
+}