diff --git a/backend/internal/pkg/antigravity/request_transformer.go b/backend/internal/pkg/antigravity/request_transformer.go
index 1b45e507..d13a8498 100644
--- a/backend/internal/pkg/antigravity/request_transformer.go
+++ b/backend/internal/pkg/antigravity/request_transformer.go
@@ -730,13 +730,14 @@ func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {
 		})
 	}
 
-	if len(funcDecls) == 0 {
-		if !hasWebSearch {
-			return nil
-		}
-
-		// Web Search 工具映射
-		return []GeminiToolDeclaration{{
+	var declarations []GeminiToolDeclaration
+	if len(funcDecls) > 0 {
+		declarations = append(declarations, GeminiToolDeclaration{
+			FunctionDeclarations: funcDecls,
+		})
+	}
+	if hasWebSearch {
+		declarations = append(declarations, GeminiToolDeclaration{
 			GoogleSearch: &GeminiGoogleSearch{
 				EnhancedContent: &GeminiEnhancedContent{
 					ImageSearch: &GeminiImageSearch{
@@ -744,10 +745,11 @@ func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {
 					},
 				},
 			},
-		}}
+		})
+	}
+	if len(declarations) == 0 {
+		return nil
 	}
 
-	return []GeminiToolDeclaration{{
-		FunctionDeclarations: funcDecls,
-	}}
+	return declarations
 }
diff --git a/backend/internal/pkg/antigravity/request_transformer_test.go b/backend/internal/pkg/antigravity/request_transformer_test.go
index 9e46295a..ccbd3e78 100644
--- a/backend/internal/pkg/antigravity/request_transformer_test.go
+++ b/backend/internal/pkg/antigravity/request_transformer_test.go
@@ -263,6 +263,29 @@ func TestBuildTools_CustomTypeTools(t *testing.T) {
 	}
 }
 
+func TestBuildTools_PreservesWebSearchAlongsideFunctions(t *testing.T) {
+	tools := []ClaudeTool{
+		{
+			Name:        "get_weather",
+			Description: "Get weather information",
+			InputSchema: map[string]any{"type": "object"},
+		},
+		{
+			Type: "web_search_20250305",
+			Name: "web_search",
+		},
+	}
+
+	result := buildTools(tools)
+	require.Len(t, result, 2)
+	require.Len(t, result[0].FunctionDeclarations, 1)
+	require.Equal(t, "get_weather", result[0].FunctionDeclarations[0].Name)
+	require.NotNil(t, result[1].GoogleSearch)
+	require.NotNil(t, result[1].GoogleSearch.EnhancedContent)
+	require.NotNil(t, result[1].GoogleSearch.EnhancedContent.ImageSearch)
+	require.Equal(t, 5, result[1].GoogleSearch.EnhancedContent.ImageSearch.MaxResultCount)
+}
+
 func TestBuildGenerationConfig_ThinkingDynamicBudget(t *testing.T) {
 	tests := []struct {
 		name        string