fix(antigravity): mixed tools (web_search + functions) now use agent route

- When tools contain both web_search and function declarations, use
  requestType=agent instead of web_search (Google web_search route
  rejects functionDeclarations)
- Set toolConfig.mode=AUTO when mixed tools detected (VALIDATED is
  incompatible with googleSearch + functionDeclarations)
- Add hasOnlyWebSearchTools helper
- Fix buildParts test calls missing 4th arg (stripSignatures)

backend/internal/handler/failover_loop.go

@@ -37,11 +37,17 @@ const (
 	// Service 层在 SingleAccountRetry 模式下已做充分原地重试（最多 3 次、总等待 30s），
 	// Handler 层只需短暂间隔后重新进入 Service 层即可。
 	singleAccountBackoffDelay = 2 * time.Second
-	// stickyGraceRetries 粘性会话绑定账号的宽限重试次数：
+	// stickyGraceRetries 粘性会话绑定账号的宽限重试次数（默认）：
 	// 命中 sticky 的账号在首次失败时原地重试，避免会话瞬移到其他账号导致上下文断裂。
 	stickyGraceRetries = 1
-	// stickyGraceDelay 粘性宽限重试间隔
+	// stickyGraceDelay 粘性宽限重试间隔（默认）
 	stickyGraceDelay = 1500 * time.Millisecond
+	// windsurfStickyGraceRetries Windsurf 平台专属粘性宽限次数。
+	// Windsurf 的 LS 进程有冷启动开销，且切号后需要重建完整历史上下文（最多 3.5MB），
+	// 宽限次数更多可减少不必要切号，保留 cascade 会话连续性。
+	windsurfStickyGraceRetries = 3
+	// windsurfStickyGraceDelay Windsurf 平台粘性宽限重试间隔（LS 处理更耗时）
+	windsurfStickyGraceDelay = 2000 * time.Millisecond
 )
 
 // FailoverState 跨循环迭代共享的 failover 状态
@@ -57,6 +63,10 @@ type FailoverState struct {
 	stickyBoundAccountID int64
 	// stickyGraceUsed 已消耗的粘性宽限次数
 	stickyGraceUsed int
+	// stickyGraceMax 最大粘性宽限次数（平台相关，0 表示使用默认值）
+	stickyGraceMax int
+	// stickyGraceInterval 粘性宽限重试间隔（平台相关，0 表示使用默认值）
+	stickyGraceInterval time.Duration
 }
 
 // NewFailoverState 创建 failover 状态
@@ -75,6 +85,30 @@ func (s *FailoverState) WithStickyBoundAccount(accountID int64) *FailoverState {
 	return s
 }
 
+// WithStickyGraceConfig 配置平台相关的粘性宽限参数。
+// 仅在 stickyBoundAccountID > 0 时生效。
+func (s *FailoverState) WithStickyGraceConfig(maxRetries int, interval time.Duration) *FailoverState {
+	s.stickyGraceMax = maxRetries
+	s.stickyGraceInterval = interval
+	return s
+}
+
+// effectiveStickyGraceMax 返回实际生效的宽限次数（未配置时用平台默认值）
+func (s *FailoverState) effectiveStickyGraceMax() int {
+	if s.stickyGraceMax > 0 {
+		return s.stickyGraceMax
+	}
+	return stickyGraceRetries
+}
+
+// effectiveStickyGraceInterval 返回实际生效的宽限间隔（未配置时用平台默认值）
+func (s *FailoverState) effectiveStickyGraceInterval() time.Duration {
+	if s.stickyGraceInterval > 0 {
+		return s.stickyGraceInterval
+	}
+	return stickyGraceDelay
+}
+
 // HandleFailoverError 处理 UpstreamFailoverError，返回下一步动作。
 // 包含：缓存计费判断、同账号重试、临时封禁、切换计数、Antigravity 延时。
 func (s *FailoverState) HandleFailoverError(
@@ -111,15 +145,15 @@ func (s *FailoverState) HandleFailoverError(
 	// 仅对非 RetryableOnSameAccount 的硬失败生效（RetryableOnSameAccount 上面已处理）。
 	if s.stickyBoundAccountID > 0 &&
 		accountID == s.stickyBoundAccountID &&
-		s.stickyGraceUsed < stickyGraceRetries {
+		s.stickyGraceUsed < s.effectiveStickyGraceMax() {
 		s.stickyGraceUsed++
 		logger.FromContext(ctx).Warn("gateway.failover_sticky_grace_retry",
 			zap.Int64("account_id", accountID),
 			zap.Int("upstream_status", failoverErr.StatusCode),
 			zap.Int("sticky_grace_used", s.stickyGraceUsed),
-			zap.Int("sticky_grace_max", stickyGraceRetries),
+			zap.Int("sticky_grace_max", s.effectiveStickyGraceMax()),
 		)
-		if !sleepWithContext(ctx, stickyGraceDelay) {
+		if !sleepWithContext(ctx, s.effectiveStickyGraceInterval()) {
 			return FailoverCanceled
 		}
 		return FailoverContinue

backend/internal/handler/failover_loop_test.go

@@ -727,3 +727,74 @@ func TestHandleSelectionExhausted(t *testing.T) {
 		require.Equal(t, FailoverContinue, action)
 	})
 }
+
+// ---------------------------------------------------------------------------
+// HandleFailoverError — Windsurf 粘性宽限配置 (WithStickyGraceConfig)
+// ---------------------------------------------------------------------------
+
+func TestHandleFailoverError_StickyGraceConfig(t *testing.T) {
+	t.Run("默认配置使用stickyGraceRetries=1", func(t *testing.T) {
+		mock := &mockTempUnscheduler{}
+		fs := NewFailoverState(5, true).WithStickyBoundAccount(100)
+		err := newTestFailoverErr(500, false, false)
+
+		// 第 1 次宽限
+		action := fs.HandleFailoverError(context.Background(), mock, 100, "windsurf", err)
+		require.Equal(t, FailoverContinue, action)
+		require.Equal(t, 1, fs.stickyGraceUsed)
+
+		// 第 2 次：默认最大=1，已用完 → 切换
+		action = fs.HandleFailoverError(context.Background(), mock, 100, "windsurf", err)
+		require.Equal(t, FailoverContinue, action)
+		require.Equal(t, 1, fs.SwitchCount, "宽限用完后应切换")
+	})
+
+	t.Run("Windsurf专属配置grace=3次", func(t *testing.T) {
+		mock := &mockTempUnscheduler{}
+		fs := NewFailoverState(5, true).
+			WithStickyBoundAccount(100).
+			WithStickyGraceConfig(windsurfStickyGraceRetries, 10*time.Millisecond) // 用极短间隔加速测试
+		err := newTestFailoverErr(500, false, false)
+
+		// 前 3 次都应该是宽限重试
+		for i := 1; i <= windsurfStickyGraceRetries; i++ {
+			action := fs.HandleFailoverError(context.Background(), mock, 100, service.PlatformWindsurf, err)
+			require.Equal(t, FailoverContinue, action, "第%d次应为宽限重试", i)
+			require.Equal(t, i, fs.stickyGraceUsed)
+			require.Equal(t, 0, fs.SwitchCount, "宽限期间不应切换")
+		}
+
+		// 第 4 次：宽限耗尽 → 切换
+		action := fs.HandleFailoverError(context.Background(), mock, 100, service.PlatformWindsurf, err)
+		require.Equal(t, FailoverContinue, action)
+		require.Equal(t, 1, fs.SwitchCount, "宽限耗尽后应切换")
+	})
+
+	t.Run("Windsurf配置不影响其他账号", func(t *testing.T) {
+		mock := &mockTempUnscheduler{}
+		fs := NewFailoverState(5, true).
+			WithStickyBoundAccount(100).
+			WithStickyGraceConfig(windsurfStickyGraceRetries, 10*time.Millisecond)
+		err := newTestFailoverErr(500, false, false)
+
+		// 非 sticky 账号 200 不走宽限，直接切换
+		action := fs.HandleFailoverError(context.Background(), mock, 200, service.PlatformWindsurf, err)
+		require.Equal(t, FailoverContinue, action)
+		require.Equal(t, 0, fs.stickyGraceUsed, "非 sticky 账号不消耗宽限次数")
+		require.Equal(t, 1, fs.SwitchCount)
+	})
+
+	t.Run("WithStickyGraceConfig链式调用", func(t *testing.T) {
+		fs := NewFailoverState(5, true).
+			WithStickyBoundAccount(100).
+			WithStickyGraceConfig(2, 100*time.Millisecond)
+		require.Equal(t, 2, fs.effectiveStickyGraceMax())
+		require.Equal(t, 100*time.Millisecond, fs.effectiveStickyGraceInterval())
+	})
+
+	t.Run("未配置时使用默认值", func(t *testing.T) {
+		fs := NewFailoverState(5, true).WithStickyBoundAccount(100)
+		require.Equal(t, stickyGraceRetries, fs.effectiveStickyGraceMax())
+		require.Equal(t, stickyGraceDelay, fs.effectiveStickyGraceInterval())
+	})
+}

backend/internal/handler/gateway_handler.go

@@ -543,6 +543,9 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 
 	for {
 		fs := NewFailoverState(h.maxAccountSwitches, hasBoundSession).WithStickyBoundAccount(sessionBoundAccountID)
+		if platform == service.PlatformWindsurf {
+			fs.WithStickyGraceConfig(windsurfStickyGraceRetries, windsurfStickyGraceDelay)
+		}
 		retryWithFallback := false
 
 		for {

backend/internal/pkg/antigravity/claude_code_tool_map_test.go

@@ -39,7 +39,7 @@ func TestBuildPartsNormalizesClaudeCodeToolNames(t *testing.T) {
 	toolIDToName := make(map[string]string)
 	assistantParts, stripped, err := buildParts(json.RawMessage(`[
 		{"type":"tool_use","id":"tool-1","name":"read_file","input":{"file_path":"/tmp/demo.txt"}}
-	]`), toolIDToName, false)
+	]`), toolIDToName, false, false)
 	require.NoError(t, err)
 	require.False(t, stripped)
 	require.Len(t, assistantParts, 1)
@@ -49,7 +49,7 @@ func TestBuildPartsNormalizesClaudeCodeToolNames(t *testing.T) {
 
 	userParts, stripped, err := buildParts(json.RawMessage(`[
 		{"type":"tool_result","tool_use_id":"tool-1","content":[{"type":"text","text":"ok"}]}
-	]`), toolIDToName, false)
+	]`), toolIDToName, false, true)
 	require.NoError(t, err)
 	require.False(t, stripped)
 	require.Len(t, userParts, 1)

backend/internal/pkg/antigravity/request_transformer.go

@@ -210,11 +210,15 @@ func TransformClaudeToGeminiWithOptions(claudeReq *ClaudeRequest, projectID, map
 		requestType = "image_gen"
 	}
 	if hasWebSearchTool {
-		requestType = "web_search"
 		if targetModel != webSearchFallbackModel {
 			targetModel = webSearchFallbackModel
 		}
 		isImageGenModel = false
+		// 混合工具（web_search + functionDeclarations）走 agent 路由；
+		// Google web_search 专用路由不支持同时携带 functionDeclarations。
+		if hasOnlyWebSearchTools(normalizedReq.Tools) {
+			requestType = "web_search"
+		}
 	}
 
 	// 检测是否启用 thinking
@@ -268,10 +272,15 @@ func TransformClaudeToGeminiWithOptions(claudeReq *ClaudeRequest, projectID, map
 	defaultValidated := !isClaudeModel || len(tools) > 0
 	if toolConfig := buildToolConfig(normalizedReq.ToolChoice, defaultValidated); toolConfig != nil {
 		// 当同时存在 functionDeclarations 和 server-side tools（如 googleSearch）时，
-		// Gemini API 要求设置 includeServerSideToolInvocations=true，否则返回 400。
+		// Gemini API 要求：
+		// 1. includeServerSideToolInvocations=true
+		// 2. mode 必须为 AUTO（VALIDATED 与混合工具不兼容，会返回 400）
 		if hasMixedTools(tools) {
 			t := true
 			toolConfig.IncludeServerSideToolInvocations = &t
+			if toolConfig.FunctionCallingConfig != nil && toolConfig.FunctionCallingConfig.Mode == "VALIDATED" {
+				toolConfig.FunctionCallingConfig.Mode = "AUTO"
+			}
 		}
 		innerRequest.ToolConfig = toolConfig
 	}
@@ -1178,6 +1187,16 @@ func hasWebSearchTool(tools []ClaudeTool) bool {
 	return false
 }
 
+// hasOnlyWebSearchTools returns true when tools contains only web_search-type tools (no function declarations).
+func hasOnlyWebSearchTools(tools []ClaudeTool) bool {
+	for _, tool := range tools {
+		if !isWebSearchTool(tool) {
+			return false
+		}
+	}
+	return len(tools) > 0
+}
+
 func isWebSearchTool(tool ClaudeTool) bool {
 	if strings.HasPrefix(tool.Type, "web_search") || tool.Type == "google_search" {
 		return true

backend/internal/pkg/antigravity/request_transformer_test.go

@@ -161,7 +161,7 @@ func TestBuildParts_ThinkingBlockWithoutSignature(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			toolIDToName := make(map[string]string)
-			parts, _, err := buildParts(json.RawMessage(tt.content), toolIDToName, tt.allowDummyThought)
+			parts, _, err := buildParts(json.RawMessage(tt.content), toolIDToName, tt.allowDummyThought, false)
 
 			if err != nil {
 				t.Fatalf("buildParts() error = %v", err)
@@ -211,7 +211,7 @@ func TestBuildParts_ToolUseSignatureHandling(t *testing.T) {
 
 	t.Run("Gemini preserves provided tool_use signature", func(t *testing.T) {
 		toolIDToName := make(map[string]string)
-		parts, _, err := buildParts(json.RawMessage(content), toolIDToName, true)
+		parts, _, err := buildParts(json.RawMessage(content), toolIDToName, true, false)
 		if err != nil {
 			t.Fatalf("buildParts() error = %v", err)
 		}
@@ -228,7 +228,7 @@ func TestBuildParts_ToolUseSignatureHandling(t *testing.T) {
 			{"type": "tool_use", "id": "t1", "name": "Bash", "input": {"command": "ls"}}
 		]`
 		toolIDToName := make(map[string]string)
-		parts, _, err := buildParts(json.RawMessage(contentNoSig), toolIDToName, true)
+		parts, _, err := buildParts(json.RawMessage(contentNoSig), toolIDToName, true, false)
 		if err != nil {
 			t.Fatalf("buildParts() error = %v", err)
 		}
@@ -242,7 +242,7 @@ func TestBuildParts_ToolUseSignatureHandling(t *testing.T) {
 
 	t.Run("Claude model - preserve valid signature for tool_use", func(t *testing.T) {
 		toolIDToName := make(map[string]string)
-		parts, _, err := buildParts(json.RawMessage(content), toolIDToName, false)
+		parts, _, err := buildParts(json.RawMessage(content), toolIDToName, false, false)
 		if err != nil {
 			t.Fatalf("buildParts() error = %v", err)
 		}