backend: add unified restart-required signature logic

- Add bootConfigSignature to gateway state for tracking restart-sensitive config
- Implement computeConfigSignature() to capture model and tool enabled states
- Add gatewayRestartRequiredBySignature() for unified restart detection
- Update gatewayStatusData() to use signature-based comparison
- Preserve backward compatibility with existing boot_default_model field

web/backend/api/gateway.go

@@ -29,6 +29,7 @@ var gateway = struct {
 	cmd                 *exec.Cmd
 	owned               bool // true if we started the process, false if we attached to an existing one
 	bootDefaultModel    string
+	bootConfigSignature string
 	runtimeStatus       string
 	startupDeadline     time.Time
 	logs                *LogBuffer
@@ -187,6 +188,95 @@ func gatewayRestartRequired(configDefaultModel, bootDefaultModel, gatewayStatus
 	return configDefaultModel != bootDefaultModel
 }
 
+func computeConfigSignature(cfg *config.Config) string {
+	if cfg == nil {
+		return ""
+	}
+	var parts []string
+	defaultModel := strings.TrimSpace(cfg.Agents.Defaults.GetModelName())
+	if defaultModel != "" {
+		parts = append(parts, "model:"+defaultModel)
+	}
+	toolSignatures := []string{}
+	if cfg.Tools.ReadFile.Enabled {
+		toolSignatures = append(toolSignatures, "read_file")
+	}
+	if cfg.Tools.WriteFile.Enabled {
+		toolSignatures = append(toolSignatures, "write_file")
+	}
+	if cfg.Tools.ListDir.Enabled {
+		toolSignatures = append(toolSignatures, "list_dir")
+	}
+	if cfg.Tools.EditFile.Enabled {
+		toolSignatures = append(toolSignatures, "edit_file")
+	}
+	if cfg.Tools.AppendFile.Enabled {
+		toolSignatures = append(toolSignatures, "append_file")
+	}
+	if cfg.Tools.Exec.Enabled {
+		toolSignatures = append(toolSignatures, "exec")
+	}
+	if cfg.Tools.Cron.Enabled {
+		toolSignatures = append(toolSignatures, "cron")
+	}
+	if cfg.Tools.Web.Enabled {
+		toolSignatures = append(toolSignatures, "web")
+	}
+	if cfg.Tools.WebFetch.Enabled {
+		toolSignatures = append(toolSignatures, "web_fetch")
+	}
+	if cfg.Tools.Message.Enabled {
+		toolSignatures = append(toolSignatures, "message")
+	}
+	if cfg.Tools.SendFile.Enabled {
+		toolSignatures = append(toolSignatures, "send_file")
+	}
+	if cfg.Tools.FindSkills.Enabled {
+		toolSignatures = append(toolSignatures, "find_skills")
+	}
+	if cfg.Tools.InstallSkill.Enabled {
+		toolSignatures = append(toolSignatures, "install_skill")
+	}
+	if cfg.Tools.Spawn.Enabled {
+		toolSignatures = append(toolSignatures, "spawn")
+	}
+	if cfg.Tools.SpawnStatus.Enabled {
+		toolSignatures = append(toolSignatures, "spawn_status")
+	}
+	if cfg.Tools.I2C.Enabled {
+		toolSignatures = append(toolSignatures, "i2c")
+	}
+	if cfg.Tools.SPI.Enabled {
+		toolSignatures = append(toolSignatures, "spi")
+	}
+	if cfg.Tools.MCP.Enabled {
+		toolSignatures = append(toolSignatures, "mcp")
+	}
+	if cfg.Tools.MCP.Discovery.Enabled {
+		toolSignatures = append(toolSignatures, "mcp_discovery")
+	}
+	if cfg.Tools.MCP.Discovery.UseRegex {
+		toolSignatures = append(toolSignatures, "mcp_discovery_regex")
+	}
+	if cfg.Tools.MCP.Discovery.UseBM25 {
+		toolSignatures = append(toolSignatures, "mcp_discovery_bm25")
+	}
+	if len(toolSignatures) > 0 {
+		parts = append(parts, "tools:"+strings.Join(toolSignatures, ","))
+	}
+	return strings.Join(parts, ";")
+}
+
+func gatewayRestartRequiredBySignature(bootSignature, currentSignature, gatewayStatus string) bool {
+	if gatewayStatus != "running" {
+		return false
+	}
+	if bootSignature == "" || currentSignature == "" {
+		return false
+	}
+	return bootSignature != currentSignature
+}
+
 func isCmdProcessAliveLocked(cmd *exec.Cmd) bool {
 	if cmd == nil || cmd.Process == nil {
 		return false
@@ -228,10 +318,11 @@ func attachToGatewayProcessLocked(pid int, cfg *config.Config) error {
 	gateway.owned = false // We didn't start this process
 	setGatewayRuntimeStatusLocked("running")
 
-	// Update bootDefaultModel from config
+	// Update bootDefaultModel and bootConfigSignature from config
 	if cfg != nil {
 		defaultModelName := strings.TrimSpace(cfg.Agents.Defaults.GetModelName())
 		gateway.bootDefaultModel = defaultModelName
+		gateway.bootConfigSignature = computeConfigSignature(cfg)
 	}
 
 	logger.InfoC("gateway", fmt.Sprintf("Attached to gateway process (PID: %d)", pid))
@@ -419,6 +510,7 @@ func (h *Handler) startGatewayLocked(initialStatus string, existingPid int) (int
 	gateway.cmd = cmd
 	gateway.owned = true // We started this process
 	gateway.bootDefaultModel = defaultModelName
+	gateway.bootConfigSignature = computeConfigSignature(cfg)
 	setGatewayRuntimeStatusLocked(initialStatus)
 	pid = cmd.Process.Pid
 	logger.InfoC("gateway", fmt.Sprintf("Started picoclaw gateway (PID: %d) from %s", pid, execPath))
@@ -439,6 +531,7 @@ func (h *Handler) startGatewayLocked(initialStatus string, existingPid int) (int
 		if gateway.cmd == cmd {
 			gateway.cmd = nil
 			gateway.bootDefaultModel = ""
+			gateway.bootConfigSignature = ""
 			if gateway.runtimeStatus != "restarting" {
 				setGatewayRuntimeStatusLocked("stopped")
 			}
@@ -784,11 +877,14 @@ func (h *Handler) gatewayStatusData() map[string]any {
 		}
 	}
 
-	bootDefaultModel, _ := data["boot_default_model"].(string)
 	gatewayStatus, _ := data["gateway_status"].(string)
-	data["gateway_restart_required"] = gatewayRestartRequired(
+	currentConfigSignature := computeConfigSignature(cfg)
-		configDefaultModel,
+	gateway.mu.Lock()
-		bootDefaultModel,
+	bootConfigSignature := gateway.bootConfigSignature
+	gateway.mu.Unlock()
+	data["gateway_restart_required"] = gatewayRestartRequiredBySignature(
+		bootConfigSignature,
+		currentConfigSignature,
 		gatewayStatus,
 	)