diff --git a/backend/internal/service/gemini_messages_compat_service.go b/backend/internal/service/gemini_messages_compat_service.go
index 45aa3599..a61274d9 100644
--- a/backend/internal/service/gemini_messages_compat_service.go
+++ b/backend/internal/service/gemini_messages_compat_service.go
@@ -612,7 +612,8 @@ func (s *GeminiMessagesCompatService) Forward(ctx context.Context, c *gin.Contex
 				fullURL += "?alt=sse"
 			}
 
-			upstreamReq, err := http.NewRequestWithContext(ctx, http.MethodPost, fullURL, bytes.NewReader(geminiReq))
+			restGeminiReq := normalizeGeminiRequestForAIStudio(geminiReq)
+			upstreamReq, err := http.NewRequestWithContext(ctx, http.MethodPost, fullURL, bytes.NewReader(restGeminiReq))
 			if err != nil {
 				return nil, "", err
 			}
@@ -685,7 +686,8 @@ func (s *GeminiMessagesCompatService) Forward(ctx context.Context, c *gin.Contex
 					fullURL += "?alt=sse"
 				}
 
-				upstreamReq, err := http.NewRequestWithContext(ctx, http.MethodPost, fullURL, bytes.NewReader(geminiReq))
+				restGeminiReq := normalizeGeminiRequestForAIStudio(geminiReq)
+				upstreamReq, err := http.NewRequestWithContext(ctx, http.MethodPost, fullURL, bytes.NewReader(restGeminiReq))
 				if err != nil {
 					return nil, "", err
 				}
@@ -3240,6 +3242,46 @@ func convertClaudeToolsToGeminiTools(tools any) []any {
 	return out
 }
 
+func normalizeGeminiRequestForAIStudio(body []byte) []byte {
+	var payload map[string]any
+	if err := json.Unmarshal(body, &payload); err != nil {
+		return body
+	}
+
+	tools, ok := payload["tools"].([]any)
+	if !ok || len(tools) == 0 {
+		return body
+	}
+
+	modified := false
+	for _, rawTool := range tools {
+		tool, ok := rawTool.(map[string]any)
+		if !ok {
+			continue
+		}
+		googleSearch, ok := tool["googleSearch"]
+		if !ok {
+			continue
+		}
+		if _, exists := tool["google_search"]; exists {
+			continue
+		}
+		tool["google_search"] = googleSearch
+		delete(tool, "googleSearch")
+		modified = true
+	}
+
+	if !modified {
+		return body
+	}
+
+	normalized, err := json.Marshal(payload)
+	if err != nil {
+		return body
+	}
+	return normalized
+}
+
 func isClaudeWebSearchToolMap(tool map[string]any) bool {
 	toolType, _ := tool["type"].(string)
 	if strings.HasPrefix(toolType, "web_search") || toolType == "google_search" {
diff --git a/backend/internal/service/gemini_messages_compat_service_test.go b/backend/internal/service/gemini_messages_compat_service_test.go
index 0d132b48..c2adf45d 100644
--- a/backend/internal/service/gemini_messages_compat_service_test.go
+++ b/backend/internal/service/gemini_messages_compat_service_test.go
@@ -261,6 +261,53 @@ func TestGeminiMessagesCompatServiceForward_PreservesRequestedModelAndMappedUpst
 	require.Contains(t, httpStub.lastReq.URL.String(), "/models/claude-sonnet-4-20250514:")
 }
 
+func TestGeminiMessagesCompatServiceForward_NormalizesWebSearchToolForAIStudio(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/messages", nil)
+
+	httpStub := &geminiCompatHTTPUpstreamStub{
+		response: &http.Response{
+			StatusCode: http.StatusOK,
+			Header:     http.Header{"x-request-id": []string{"gemini-req-2"}},
+			Body:       io.NopCloser(strings.NewReader(`{"candidates":[{"content":{"parts":[{"text":"hello"}]}}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":5}}`)),
+		},
+	}
+	svc := &GeminiMessagesCompatService{httpUpstream: httpStub, cfg: &config.Config{}}
+	account := &Account{
+		ID:   1,
+		Type: AccountTypeAPIKey,
+		Credentials: map[string]any{
+			"api_key": "test-key",
+		},
+	}
+	body := []byte(`{"model":"claude-sonnet-4","max_tokens":16,"messages":[{"role":"user","content":"hello"}],"tools":[{"name":"get_weather","description":"Get weather info","input_schema":{"type":"object"}},{"type":"web_search_20250305","name":"web_search"}]}`)
+
+	result, err := svc.Forward(context.Background(), c, account, body)
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.NotNil(t, httpStub.lastReq)
+
+	postedBody, err := io.ReadAll(httpStub.lastReq.Body)
+	require.NoError(t, err)
+
+	var posted map[string]any
+	require.NoError(t, json.Unmarshal(postedBody, &posted))
+	tools, ok := posted["tools"].([]any)
+	require.True(t, ok)
+	require.Len(t, tools, 2)
+
+	searchTool, ok := tools[1].(map[string]any)
+	require.True(t, ok)
+	_, hasSnake := searchTool["google_search"]
+	_, hasCamel := searchTool["googleSearch"]
+	require.True(t, hasSnake)
+	require.False(t, hasCamel)
+	_, hasFuncDecl := searchTool["functionDeclarations"]
+	require.False(t, hasFuncDecl)
+}
+
 func TestConvertClaudeMessagesToGeminiGenerateContent_AddsThoughtSignatureForToolUse(t *testing.T) {
 	claudeReq := map[string]any{
 		"model":      "claude-haiku-4-5-20251001",