backend: add restart-required coverage tests for model/tools/config

- TestGatewayStatusRequiresRestartAfterToolChange: verify tool toggle triggers restart hint
- TestGatewayStatusNoRestartRequiredForNonSensitiveChanges: verify non-sensitive changes don't trigger
- TestGatewayStatusNoRestartRequiredWhenNotRunning: verify no restart hint when gateway stopped
- Update resetGatewayTestState to clear bootConfigSignature

web/backend/api/gateway_test.go

@@ -77,6 +77,7 @@ func resetGatewayTestState(t *testing.T) {
 		gateway.mu.Lock()
 		gateway.cmd = nil
 		gateway.bootDefaultModel = ""
+		gateway.bootConfigSignature = ""
 		setGatewayRuntimeStatusLocked("stopped")
 		gateway.mu.Unlock()
 	})
@@ -502,9 +503,11 @@ func TestGatewayStatusRequiresRestartAfterDefaultModelChange(t *testing.T) {
 		t.Fatalf("FindProcess() error = %v", err)
 	}
 
+	bootSignature := computeConfigSignature(cfg)
 	gateway.mu.Lock()
 	gateway.cmd = &exec.Cmd{Process: process}
 	gateway.bootDefaultModel = cfg.ModelList[0].ModelName
+	gateway.bootConfigSignature = bootSignature
 	setGatewayRuntimeStatusLocked("running")
 	gateway.mu.Unlock()
 
@@ -548,6 +551,188 @@ func TestGatewayStatusRequiresRestartAfterDefaultModelChange(t *testing.T) {
 	}
 }
 
+func TestGatewayStatusRequiresRestartAfterToolChange(t *testing.T) {
+	resetGatewayTestState(t)
+
+	configPath := filepath.Join(t.TempDir(), "config.json")
+	cfg := config.DefaultConfig()
+	cfg.Agents.Defaults.ModelName = cfg.ModelList[0].ModelName
+	cfg.ModelList[0].SetAPIKey("test-key")
+	cfg.Tools.WriteFile.Enabled = true
+	if err := config.SaveConfig(configPath, cfg); err != nil {
+		t.Fatalf("SaveConfig() error = %v", err)
+	}
+
+	h := NewHandler(configPath)
+	mux := http.NewServeMux()
+	h.RegisterRoutes(mux)
+
+	process, err := os.FindProcess(os.Getpid())
+	if err != nil {
+		t.Fatalf("FindProcess() error = %v", err)
+	}
+
+	bootSignature := computeConfigSignature(cfg)
+	gateway.mu.Lock()
+	gateway.cmd = &exec.Cmd{Process: process}
+	gateway.bootDefaultModel = cfg.ModelList[0].ModelName
+	gateway.bootConfigSignature = bootSignature
+	setGatewayRuntimeStatusLocked("running")
+	gateway.mu.Unlock()
+
+	updatedCfg, err := config.LoadConfig(configPath)
+	if err != nil {
+		t.Fatalf("LoadConfig() error = %v", err)
+	}
+	updatedCfg.Tools.WriteFile.Enabled = false
+	if err := config.SaveConfig(configPath, updatedCfg); err != nil {
+		t.Fatalf("SaveConfig() error = %v", err)
+	}
+
+	gatewayHealthGet = func(string, time.Duration) (*http.Response, error) {
+		return mockGatewayHealthResponse(http.StatusOK, os.Getpid()), nil
+	}
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/gateway/status", nil)
+	mux.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
+	}
+
+	var body map[string]any
+	if err := json.Unmarshal(rec.Body.Bytes(), &body); err != nil {
+		t.Fatalf("unmarshal response: %v", err)
+	}
+
+	if got := body["gateway_status"]; got != "running" {
+		t.Fatalf("gateway_status = %#v, want %q", got, "running")
+	}
+	if got := body["gateway_restart_required"]; got != true {
+		t.Fatalf("gateway_restart_required = %#v, want true", got)
+	}
+}
+
+func TestGatewayStatusNoRestartRequiredForNonSensitiveChanges(t *testing.T) {
+	resetGatewayTestState(t)
+
+	configPath := filepath.Join(t.TempDir(), "config.json")
+	cfg := config.DefaultConfig()
+	cfg.Agents.Defaults.ModelName = cfg.ModelList[0].ModelName
+	cfg.ModelList[0].SetAPIKey("test-key")
+	cfg.Agents.Defaults.MaxTokens = 1000
+	if err := config.SaveConfig(configPath, cfg); err != nil {
+		t.Fatalf("SaveConfig() error = %v", err)
+	}
+
+	h := NewHandler(configPath)
+	mux := http.NewServeMux()
+	h.RegisterRoutes(mux)
+
+	process, err := os.FindProcess(os.Getpid())
+	if err != nil {
+		t.Fatalf("FindProcess() error = %v", err)
+	}
+
+	bootSignature := computeConfigSignature(cfg)
+	gateway.mu.Lock()
+	gateway.cmd = &exec.Cmd{Process: process}
+	gateway.bootDefaultModel = cfg.ModelList[0].ModelName
+	gateway.bootConfigSignature = bootSignature
+	setGatewayRuntimeStatusLocked("running")
+	gateway.mu.Unlock()
+
+	updatedCfg, err := config.LoadConfig(configPath)
+	if err != nil {
+		t.Fatalf("LoadConfig() error = %v", err)
+	}
+	updatedCfg.Agents.Defaults.MaxTokens = 2000
+	if err := config.SaveConfig(configPath, updatedCfg); err != nil {
+		t.Fatalf("SaveConfig() error = %v", err)
+	}
+
+	gatewayHealthGet = func(string, time.Duration) (*http.Response, error) {
+		return mockGatewayHealthResponse(http.StatusOK, os.Getpid()), nil
+	}
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/gateway/status", nil)
+	mux.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
+	}
+
+	var body map[string]any
+	if err := json.Unmarshal(rec.Body.Bytes(), &body); err != nil {
+		t.Fatalf("unmarshal response: %v", err)
+	}
+
+	if got := body["gateway_status"]; got != "running" {
+		t.Fatalf("gateway_status = %#v, want %q", got, "running")
+	}
+	if got := body["gateway_restart_required"]; got != false {
+		t.Fatalf("gateway_restart_required = %#v, want false", got)
+	}
+}
+
+func TestGatewayStatusNoRestartRequiredWhenNotRunning(t *testing.T) {
+	resetGatewayTestState(t)
+
+	configPath := filepath.Join(t.TempDir(), "config.json")
+	cfg := config.DefaultConfig()
+	cfg.Agents.Defaults.ModelName = cfg.ModelList[0].ModelName
+	cfg.ModelList[0].SetAPIKey("test-key")
+	if err := config.SaveConfig(configPath, cfg); err != nil {
+		t.Fatalf("SaveConfig() error = %v", err)
+	}
+
+	h := NewHandler(configPath)
+	mux := http.NewServeMux()
+	h.RegisterRoutes(mux)
+
+	gateway.mu.Lock()
+	gateway.cmd = nil
+	gateway.bootDefaultModel = ""
+	gateway.bootConfigSignature = ""
+	setGatewayRuntimeStatusLocked("stopped")
+	gateway.mu.Unlock()
+
+	updatedCfg, err := config.LoadConfig(configPath)
+	if err != nil {
+		t.Fatalf("LoadConfig() error = %v", err)
+	}
+	updatedCfg.Agents.Defaults.ModelName = "different-model"
+	if err := config.SaveConfig(configPath, updatedCfg); err != nil {
+		t.Fatalf("SaveConfig() error = %v", err)
+	}
+
+	gatewayHealthGet = func(string, time.Duration) (*http.Response, error) {
+		return nil, errors.New("no gateway running")
+	}
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/gateway/status", nil)
+	mux.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
+	}
+
+	var body map[string]any
+	if err := json.Unmarshal(rec.Body.Bytes(), &body); err != nil {
+		t.Fatalf("unmarshal response: %v", err)
+	}
+
+	if got := body["gateway_status"]; got != "stopped" {
+		t.Fatalf("gateway_status = %#v, want %q", got, "stopped")
+	}
+	if got := body["gateway_restart_required"]; got != false {
+		t.Fatalf("gateway_restart_required = %#v, want false", got)
+	}
+}
+
 func TestGatewayStatusReturnsErrorAfterStartupWindowExpires(t *testing.T) {
 	resetGatewayTestState(t)