fix(watchdog): start the live watchdog on a cold enable from Settings (#9125)

The React Settings "Enable Watchdog" master toggle only ever writes the
idle/busy flags; watchdog_enabled is vestigial in that UI. The live
start/stop decision in UpdateSettingsEndpoint keyed off the raw, stale
watchdog_enabled request field, so a cold enable (idle/busy=true,
watchdog_enabled=false) called StopWatchdog() and the watchdog stayed
stopped until the next restart - at which point startup re-derived it
from the idle flag. Net: enabling the watchdog appeared to do nothing.

Derive the run-state from idle||busy as the single source of truth,
mirroring the startup invariant:

- ApplyRuntimeSettings now sets WatchDog = idle||busy whenever either
  field is present (so a full disable also brings it down), while an API
  client posting only watchdog_enabled keeps its explicit value.
- Add ApplicationConfig.WatchdogShouldRun() mirroring startWatchdog's
  gating (idle/busy, LRU eviction, memory reclaimer); the /api/settings
  handler uses it to decide start vs stop.
- Belt-and-suspenders: the Settings.jsx master toggle also writes
  watchdog_enabled = idle||busy.

Assisted-by: claude:claude-opus-4-8 [Claude Code]
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

core/config/application_config.go

@@ -488,6 +488,16 @@ func (o *ApplicationConfig) GetEffectiveMaxActiveBackends() int {
 	return 0
 }
 
+// WatchdogShouldRun reports whether the live watchdog process should be
+// running for the current config. It mirrors the gating in
+// (*Application).startWatchdog so the /api/settings start/stop decision and
+// the startup path agree on a single source of truth: the watchdog runs when
+// idle/busy checks are enabled (WatchDog), when LRU eviction is active
+// (effective max active backends > 0), or when the memory reclaimer is on.
+func (o *ApplicationConfig) WatchdogShouldRun() bool {
+	return o.WatchDog || o.GetEffectiveMaxActiveBackends() > 0 || o.MemoryReclaimerEnabled
+}
+
 // WithForceEvictionWhenBusy sets whether to force eviction even when models have active API calls
 func WithForceEvictionWhenBusy(enabled bool) AppOption {
 	return func(o *ApplicationConfig) {
@@ -1198,18 +1208,22 @@ func (o *ApplicationConfig) ApplyRuntimeSettings(settings *RuntimeSettings) (req
 	}
 	if settings.WatchdogIdleEnabled != nil {
 		o.WatchDogIdle = *settings.WatchdogIdleEnabled
-		if o.WatchDogIdle {
-			o.WatchDog = true
-		}
 		requireRestart = true
 	}
 	if settings.WatchdogBusyEnabled != nil {
 		o.WatchDogBusy = *settings.WatchdogBusyEnabled
-		if o.WatchDogBusy {
-			o.WatchDog = true
-		}
 		requireRestart = true
 	}
+	// The React Settings "Enable Watchdog" master toggle manages only the
+	// idle/busy checks — watchdog_enabled is vestigial in that UI. Whenever
+	// either idle/busy field is present in the body, derive the run-state from
+	// idle||busy so a cold enable starts the watchdog and a full disable stops
+	// it, instead of trusting the stale watchdog_enabled the UI never updates.
+	// This mirrors the startup invariant in startup.go. An API client posting
+	// only watchdog_enabled (idle/busy absent) keeps its explicit value.
+	if settings.WatchdogIdleEnabled != nil || settings.WatchdogBusyEnabled != nil {
+		o.WatchDog = o.WatchDogIdle || o.WatchDogBusy
+	}
 	if settings.WatchdogIdleTimeout != nil {
 		if dur, err := time.ParseDuration(*settings.WatchdogIdleTimeout); err == nil {
 			o.WatchDogIdleTimeout = dur

core/config/application_config_test.go

@@ -223,6 +223,69 @@ var _ = Describe("ApplicationConfig RuntimeSettings Conversion", func() {
 			Expect(appConfig.WatchDogBusy).To(BeTrue())
 		})
 
+		// Residual #9125: the React Settings "Enable Watchdog" master toggle
+		// manages only watchdog_idle_enabled / watchdog_busy_enabled — it never
+		// touches the vestigial watchdog_enabled field. On a cold enable the
+		// body therefore carries watchdog_enabled=false alongside idle/busy=true.
+		// The derived run-state (WatchDog) must follow idle||busy so the live
+		// watchdog actually starts, not the stale watchdog_enabled=false.
+		It("should derive WatchDog from idle||busy on a cold enable even when watchdog_enabled=false", func() {
+			appConfig := &ApplicationConfig{WatchDog: false}
+
+			watchdogEnabled := false
+			watchdogIdle := true
+			watchdogBusy := true
+			rs := &RuntimeSettings{
+				WatchdogEnabled:     &watchdogEnabled,
+				WatchdogIdleEnabled: &watchdogIdle,
+				WatchdogBusyEnabled: &watchdogBusy,
+			}
+
+			appConfig.ApplyRuntimeSettings(rs)
+
+			Expect(appConfig.WatchDog).To(BeTrue())
+			Expect(appConfig.WatchdogShouldRun()).To(BeTrue())
+		})
+
+		// The disable direction: the master toggle off sends idle=false,
+		// busy=false, but watchdog_enabled may still be the stale true loaded
+		// before the change. WatchDog must follow idle||busy down to false so
+		// the live watchdog is stopped (it stays stopped unless LRU / memory
+		// reclaimer keep it alive, which is gated by WatchdogShouldRun).
+		It("should disable WatchDog when both idle and busy are turned off", func() {
+			appConfig := &ApplicationConfig{WatchDog: true, WatchDogIdle: true, WatchDogBusy: true}
+
+			watchdogEnabled := true
+			watchdogIdle := false
+			watchdogBusy := false
+			rs := &RuntimeSettings{
+				WatchdogEnabled:     &watchdogEnabled,
+				WatchdogIdleEnabled: &watchdogIdle,
+				WatchdogBusyEnabled: &watchdogBusy,
+			}
+
+			appConfig.ApplyRuntimeSettings(rs)
+
+			Expect(appConfig.WatchDog).To(BeFalse())
+			Expect(appConfig.WatchdogShouldRun()).To(BeFalse())
+		})
+
+		// Backward compatibility: an API client that posts only watchdog_enabled
+		// (idle/busy nil) keeps the explicit value — the idle/busy derivation
+		// only kicks in when those fields are actually present in the body.
+		It("should preserve explicit watchdog_enabled when idle/busy are absent", func() {
+			appConfig := &ApplicationConfig{WatchDog: false}
+
+			watchdogEnabled := true
+			rs := &RuntimeSettings{
+				WatchdogEnabled: &watchdogEnabled,
+			}
+
+			appConfig.ApplyRuntimeSettings(rs)
+
+			Expect(appConfig.WatchDog).To(BeTrue())
+		})
+
 		It("should handle MaxActiveBackends and update SingleBackend accordingly", func() {
 			appConfig := &ApplicationConfig{}
 

core/http/endpoints/localai/settings.go

@@ -221,9 +221,18 @@ func UpdateSettingsEndpoint(app *application.Application) echo.HandlerFunc {
 		// Check if agent job retention changed
 		agentJobChanged := settings.AgentJobRetentionDays != nil
 
-		// Restart watchdog if settings changed
+		// Restart watchdog if settings changed.
+		//
+		// The live start/stop decision derives from the post-apply config
+		// (WatchdogShouldRun) rather than the raw watchdog_enabled request
+		// field: the React master toggle only ever writes the idle/busy flags,
+		// so keying off watchdog_enabled left the live watchdog stopped on a
+		// cold enable until the next restart (#9125). WatchdogShouldRun mirrors
+		// the gating in startWatchdog, so a cold enable starts it immediately
+		// and a full disable (both checks off, no LRU / memory reclaimer) stops
+		// it.
 		if watchdogChanged {
-			if settings.WatchdogEnabled != nil && !*settings.WatchdogEnabled {
+			if !appConfig.WatchdogShouldRun() {
 				if err := app.StopWatchdog(); err != nil {
 					xlog.Error("Failed to stop watchdog", "error", err)
 					return c.JSON(http.StatusInternalServerError, schema.SettingsResponse{

core/http/endpoints/localai/settings_test.go

@@ -108,4 +108,20 @@ var _ = Describe("Settings endpoints", func() {
 		_, err := os.Stat(filepath.Join(tmp, "runtime_settings.json"))
 		Expect(err).ToNot(HaveOccurred())
 	})
+
+	// Residual #9125: enabling the watchdog from a cold (off) state via the
+	// React master toggle must start the live watchdog immediately, without a
+	// restart. The toggle posts watchdog_idle_enabled/busy_enabled=true while
+	// the vestigial watchdog_enabled stays false (it was loaded false). The
+	// old handler keyed its stop decision off that raw watchdog_enabled=false
+	// and called StopWatchdog(), so the watchdog never started until restart.
+	It("starts the live watchdog on a cold enable even when watchdog_enabled=false", func() {
+		Expect(app.ModelLoader().GetWatchDog()).To(BeNil(), "precondition: watchdog should be off")
+
+		rec := post(`{"watchdog_enabled":false,"watchdog_idle_enabled":true,"watchdog_busy_enabled":true,"watchdog_idle_timeout":"15m","watchdog_busy_timeout":"5m","watchdog_interval":"1s"}`)
+		Expect(rec.Code).To(Equal(http.StatusOK))
+
+		Expect(app.ModelLoader().GetWatchDog()).ToNot(BeNil(),
+			"watchdog should be running after a cold enable, without waiting for a restart")
+	})
 })

core/http/react-ui/src/pages/Settings.jsx

@@ -294,7 +294,7 @@ export default function Settings() {
             </h3>
             <div className="card">
               <SettingRow label="Enable Watchdog" description="Automatically monitor and manage backend processes">
-                <Toggle checked={settings.watchdog_idle_enabled || settings.watchdog_busy_enabled} onChange={(v) => { update('watchdog_idle_enabled', v); update('watchdog_busy_enabled', v) }} />
+                <Toggle checked={settings.watchdog_idle_enabled || settings.watchdog_busy_enabled} onChange={(v) => { update('watchdog_idle_enabled', v); update('watchdog_busy_enabled', v); update('watchdog_enabled', v) }} />
               </SettingRow>
               <SettingRow label="Enable Idle Check" description="Automatically stop backends that have been idle too long">
                 <Toggle checked={settings.watchdog_idle_enabled} onChange={(v) => update('watchdog_idle_enabled', v)} disabled={!watchdogEnabled} />