fix(logs): capture backend logs by default in single mode (#10742)

Backend log capture into the per-model BackendLogStore (which feeds the
UI "Backend Logs" page and /api/backend-logs) was opt-in and off by
default in single mode, while worker/distributed mode force-enables it
via SetBackendLoggingEnabled(true). There was no CLI flag either, so the
only way to populate the store was the Settings UI toggle - and the page
was silently empty out of the box. Distributed "just worked"; single
mode looked broken.

Default EnableBackendLogging to true in NewApplicationConfig so single
mode matches worker mode. The store is a small in-memory ring buffer, so
the cost is negligible.

Now that the default is on, loadRuntimeSettingsFromFile's usual
"only flip false->true" merge would ignore a persisted false and revert
the UI toggle-off on every restart. There is no env var/CLI flag for
this setting, so an explicit persisted value is now authoritative in
both directions, letting the toggle-off survive a restart.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>

core/application/runtime_settings_branding_test.go

@@ -261,4 +261,35 @@ var _ = Describe("loadRuntimeSettingsFromFile", func() {
 			Expect(cfg.AgentPool.AgentHubURL).To(Equal("https://hub.acme.io"))
 		})
 	})
+
+	// Backend logging capture. Worker/distributed mode force-enables it
+	// (core/services/worker.SetBackendLoggingEnabled(true)); single mode used
+	// to leave it off by default with no CLI flag, so the UI "Backend Logs"
+	// page was silently empty unless the operator found the Settings toggle.
+	// It now defaults on in single mode too. Because the default is on, the
+	// loader must let a persisted enable_backend_logging=false (the UI
+	// toggle-off) win over the default - the sticky "only flip false->true"
+	// merge used for env-backed flags would otherwise ignore it and revert
+	// the toggle on every restart.
+	Describe("backend logging capture", func() {
+		It("captures backend logs by default in single mode", func() {
+			cfg := config.NewApplicationConfig()
+			Expect(cfg.EnableBackendLogging).To(BeTrue(),
+				"single mode should capture backend logs out of the box, matching worker mode")
+		})
+
+		It("honors a persisted enable_backend_logging=false across restart (toggle-off wins over default-on)", func() {
+			cfg := config.NewApplicationConfig() // default-on boot state
+			cfg.DynamicConfigsDir = seedSettings(`{"enable_backend_logging": false}`)
+			loadRuntimeSettingsFromFile(cfg)
+			Expect(cfg.EnableBackendLogging).To(BeFalse(),
+				"a UI toggle-off persisted to runtime_settings.json must survive a restart")
+		})
+
+		It("loads a persisted enable_backend_logging=true", func() {
+			cfg := &config.ApplicationConfig{DynamicConfigsDir: seedSettings(`{"enable_backend_logging": true}`)}
+			loadRuntimeSettingsFromFile(cfg)
+			Expect(cfg.EnableBackendLogging).To(BeTrue())
+		})
+	})
 })

core/application/startup.go

@@ -698,10 +698,12 @@ func loadRuntimeSettingsFromFile(options *config.ApplicationConfig) {
 		}
 	}
 
+	// Backend logging defaults on in single mode (NewApplicationConfig), so
+	// the usual "only flip false->true" merge would ignore a persisted false
+	// and revert the UI toggle-off on every restart. There is no env var/CLI
+	// flag for it, so an explicit persisted value is authoritative here.
 	if settings.EnableBackendLogging != nil {
-		if !options.EnableBackendLogging {
-			options.EnableBackendLogging = *settings.EnableBackendLogging
-		}
+		options.EnableBackendLogging = *settings.EnableBackendLogging
 	}
 
 	// Tracing settings

core/config/application_config.go

@@ -246,9 +246,16 @@ type AppOption func(*ApplicationConfig)
 
 func NewApplicationConfig(o ...AppOption) *ApplicationConfig {
 	opt := &ApplicationConfig{
-		Context:                  context.Background(),
-		UploadLimitMB:            15,
-		Debug:                    true,
+		Context:       context.Background(),
+		UploadLimitMB: 15,
+		Debug:         true,
+		// Capture backend process stdout/stderr into the per-model
+		// BackendLogStore by default so the UI "Backend Logs" page works out
+		// of the box in single mode, matching worker/distributed mode (which
+		// force-enables it). It's a small in-memory ring buffer; the Settings
+		// toggle can still turn it off (a persisted false wins - see
+		// loadRuntimeSettingsFromFile).
+		EnableBackendLogging:     true,
 		AgentJobRetentionDays:    30,              // Default: 30 days
 		LRUEvictionMaxRetries:    30,              // Default: 30 retries
 		LRUEvictionRetryInterval: 1 * time.Second, // Default: 1 second