**chore(executor): update default agent version and simplify const formatting**

- Updated `defaultAntigravityAgent` to version `1.11.5`.
- Adjusted const value formatting for improved readability.

**feat(executor): introduce fallback mechanism for Antigravity base URLs**

- Added retry logic with fallback order for Antigravity base URLs to handle request errors and rate limits.
- Refactored base URL handling with `antigravityBaseURLFallbackOrder` and related utilities.
- Enhanced error handling in non-streaming and streaming requests with retry support and improved metadata reporting.
- Updated `buildRequest` to support dynamic base URL assignment.

internal/runtime/executor/antigravity_executor.go

@@ -26,16 +26,18 @@ import (
 )
 
 const (
-	antigravityBaseURL          = "https://daily-cloudcode-pa.sandbox.googleapis.com"
-	antigravityStreamPath       = "/v1internal:streamGenerateContent"
-	antigravityGeneratePath     = "/v1internal:generateContent"
-	antigravityModelsPath       = "/v1internal:fetchAvailableModels"
-	antigravityClientID         = "1071006060591-tmhssin2h21lcre235vtolojh4g403ep.apps.googleusercontent.com"
-	antigravityClientSecret     = "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"
-	defaultAntigravityAgent     = "antigravity/1.11.3 windows/amd64"
-	antigravityAuthType         = "antigravity"
-	refreshSkew                 = 5 * time.Minute
-	streamScannerBuffer     int = 20_971_520
+	antigravityBaseURLDaily        = "https://daily-cloudcode-pa.sandbox.googleapis.com"
+	antigravityBaseURLAutopush     = "https://autopush-cloudcode-pa.sandbox.googleapis.com"
+	antigravityBaseURLProd         = "https://cloudcode-pa.googleapis.com"
+	antigravityStreamPath          = "/v1internal:streamGenerateContent"
+	antigravityGeneratePath        = "/v1internal:generateContent"
+	antigravityModelsPath          = "/v1internal:fetchAvailableModels"
+	antigravityClientID            = "1071006060591-tmhssin2h21lcre235vtolojh4g403ep.apps.googleusercontent.com"
+	antigravityClientSecret        = "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"
+	defaultAntigravityAgent        = "antigravity/1.11.5 windows/amd64"
+	antigravityAuthType            = "antigravity"
+	refreshSkew                    = 3000 * time.Second
+	streamScannerBuffer        int = 20_971_520
 )
 
 var randSource = rand.New(rand.NewSource(time.Now().UnixNano()))
@@ -73,43 +75,76 @@ func (e *AntigravityExecutor) Execute(ctx context.Context, auth *cliproxyauth.Au
 	to := sdktranslator.FromString("antigravity")
 	translated := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), false)
 
-	httpReq, errReq := e.buildRequest(ctx, auth, token, req.Model, translated, false, opts.Alt)
-	if errReq != nil {
-		return resp, errReq
-	}
-
+	baseURLs := antigravityBaseURLFallbackOrder(auth)
 	httpClient := newProxyAwareHTTPClient(ctx, e.cfg, auth, 0)
-	httpResp, errDo := httpClient.Do(httpReq)
-	if errDo != nil {
-		recordAPIResponseError(ctx, e.cfg, errDo)
-		return resp, errDo
-	}
-	defer func() {
+
+	var lastStatus int
+	var lastBody []byte
+	var lastErr error
+
+	for idx, baseURL := range baseURLs {
+		httpReq, errReq := e.buildRequest(ctx, auth, token, req.Model, translated, false, opts.Alt, baseURL)
+		if errReq != nil {
+			err = errReq
+			return resp, err
+		}
+
+		httpResp, errDo := httpClient.Do(httpReq)
+		if errDo != nil {
+			recordAPIResponseError(ctx, e.cfg, errDo)
+			lastStatus = 0
+			lastBody = nil
+			lastErr = errDo
+			if idx+1 < len(baseURLs) {
+				log.Debugf("antigravity executor: request error on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
+				continue
+			}
+			err = errDo
+			return resp, err
+		}
+
+		recordAPIResponseMetadata(ctx, e.cfg, httpResp.StatusCode, httpResp.Header.Clone())
+		bodyBytes, errRead := io.ReadAll(httpResp.Body)
 		if errClose := httpResp.Body.Close(); errClose != nil {
 			log.Errorf("antigravity executor: close response body error: %v", errClose)
 		}
-	}()
+		if errRead != nil {
+			recordAPIResponseError(ctx, e.cfg, errRead)
+			err = errRead
+			return resp, err
+		}
+		appendAPIResponseChunk(ctx, e.cfg, bodyBytes)
 
-	recordAPIResponseMetadata(ctx, e.cfg, httpResp.StatusCode, httpResp.Header.Clone())
-	bodyBytes, errRead := io.ReadAll(httpResp.Body)
-	if errRead != nil {
-		recordAPIResponseError(ctx, e.cfg, errRead)
-		return resp, errRead
-	}
-	appendAPIResponseChunk(ctx, e.cfg, bodyBytes)
+		if httpResp.StatusCode < http.StatusOK || httpResp.StatusCode >= http.StatusMultipleChoices {
+			log.Debugf("antigravity executor: upstream error status: %d, body: %s", httpResp.StatusCode, summarizeErrorBody(httpResp.Header.Get("Content-Type"), bodyBytes))
+			lastStatus = httpResp.StatusCode
+			lastBody = append([]byte(nil), bodyBytes...)
+			lastErr = nil
+			if httpResp.StatusCode == http.StatusTooManyRequests && idx+1 < len(baseURLs) {
+				log.Debugf("antigravity executor: rate limited on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
+				continue
+			}
+			err = statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+			return resp, err
+		}
 
-	if httpResp.StatusCode < http.StatusOK || httpResp.StatusCode >= http.StatusMultipleChoices {
-		log.Debugf("antigravity executor: upstream error status: %d, body: %s", httpResp.StatusCode, summarizeErrorBody(httpResp.Header.Get("Content-Type"), bodyBytes))
-		err = statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
-		return resp, err
+		reporter.publish(ctx, parseAntigravityUsage(bodyBytes))
+		var param any
+		converted := sdktranslator.TranslateNonStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), translated, bodyBytes, &param)
+		resp = cliproxyexecutor.Response{Payload: []byte(converted)}
+		reporter.ensurePublished(ctx)
+		return resp, nil
 	}
 
-	reporter.publish(ctx, parseAntigravityUsage(bodyBytes))
-	var param any
-	converted := sdktranslator.TranslateNonStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), translated, bodyBytes, &param)
-	resp = cliproxyexecutor.Response{Payload: []byte(converted)}
-	reporter.ensurePublished(ctx)
-	return resp, nil
+	switch {
+	case lastStatus != 0:
+		err = statusErr{code: lastStatus, msg: string(lastBody)}
+	case lastErr != nil:
+		err = lastErr
+	default:
+		err = statusErr{code: http.StatusServiceUnavailable, msg: "antigravity executor: no base url available"}
+	}
+	return resp, err
 }
 
 // ExecuteStream handles streaming requests via the antigravity upstream.
@@ -131,75 +166,121 @@ func (e *AntigravityExecutor) ExecuteStream(ctx context.Context, auth *cliproxya
 	to := sdktranslator.FromString("antigravity")
 	translated := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), true)
 
-	httpReq, errReq := e.buildRequest(ctx, auth, token, req.Model, translated, true, opts.Alt)
-	if errReq != nil {
-		return nil, errReq
-	}
-
+	baseURLs := antigravityBaseURLFallbackOrder(auth)
 	httpClient := newProxyAwareHTTPClient(ctx, e.cfg, auth, 0)
-	httpResp, errDo := httpClient.Do(httpReq)
-	if errDo != nil {
-		recordAPIResponseError(ctx, e.cfg, errDo)
-		return nil, errDo
-	}
-	recordAPIResponseMetadata(ctx, e.cfg, httpResp.StatusCode, httpResp.Header.Clone())
-	if httpResp.StatusCode < http.StatusOK || httpResp.StatusCode >= http.StatusMultipleChoices {
-		bodyBytes, _ := io.ReadAll(httpResp.Body)
-		appendAPIResponseChunk(ctx, e.cfg, bodyBytes)
-		if errClose := httpResp.Body.Close(); errClose != nil {
-			log.Errorf("antigravity executor: close response body error: %v", errClose)
-		}
-		err = statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
-		return nil, err
-	}
 
-	out := make(chan cliproxyexecutor.StreamChunk)
-	stream = out
-	go func() {
-		defer close(out)
-		defer func() {
+	var lastStatus int
+	var lastBody []byte
+	var lastErr error
+
+	for idx, baseURL := range baseURLs {
+		httpReq, errReq := e.buildRequest(ctx, auth, token, req.Model, translated, true, opts.Alt, baseURL)
+		if errReq != nil {
+			err = errReq
+			return nil, err
+		}
+
+		httpResp, errDo := httpClient.Do(httpReq)
+		if errDo != nil {
+			recordAPIResponseError(ctx, e.cfg, errDo)
+			lastStatus = 0
+			lastBody = nil
+			lastErr = errDo
+			if idx+1 < len(baseURLs) {
+				log.Debugf("antigravity executor: request error on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
+				continue
+			}
+			err = errDo
+			return nil, err
+		}
+		recordAPIResponseMetadata(ctx, e.cfg, httpResp.StatusCode, httpResp.Header.Clone())
+		if httpResp.StatusCode < http.StatusOK || httpResp.StatusCode >= http.StatusMultipleChoices {
+			bodyBytes, errRead := io.ReadAll(httpResp.Body)
 			if errClose := httpResp.Body.Close(); errClose != nil {
 				log.Errorf("antigravity executor: close response body error: %v", errClose)
 			}
-		}()
-		scanner := bufio.NewScanner(httpResp.Body)
-		scanner.Buffer(nil, streamScannerBuffer)
-		var param any
-		for scanner.Scan() {
-			line := scanner.Bytes()
-			appendAPIResponseChunk(ctx, e.cfg, line)
-
-			// Filter usage metadata for all models
-			// Only retain usage statistics in the terminal chunk
-			line = FilterSSEUsageMetadata(line)
-
-			payload := jsonPayload(line)
-			if payload == nil {
+			if errRead != nil {
+				recordAPIResponseError(ctx, e.cfg, errRead)
+				lastStatus = 0
+				lastBody = nil
+				lastErr = errRead
+				if idx+1 < len(baseURLs) {
+					log.Debugf("antigravity executor: read error on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
+					continue
+				}
+				err = errRead
+				return nil, err
+			}
+			appendAPIResponseChunk(ctx, e.cfg, bodyBytes)
+			lastStatus = httpResp.StatusCode
+			lastBody = append([]byte(nil), bodyBytes...)
+			lastErr = nil
+			if httpResp.StatusCode == http.StatusTooManyRequests && idx+1 < len(baseURLs) {
+				log.Debugf("antigravity executor: rate limited on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
 				continue
 			}
+			err = statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+			return nil, err
+		}
 
-			if detail, ok := parseAntigravityStreamUsage(payload); ok {
-				reporter.publish(ctx, detail)
-			}
+		out := make(chan cliproxyexecutor.StreamChunk)
+		stream = out
+		go func(resp *http.Response) {
+			defer close(out)
+			defer func() {
+				if errClose := resp.Body.Close(); errClose != nil {
+					log.Errorf("antigravity executor: close response body error: %v", errClose)
+				}
+			}()
+			scanner := bufio.NewScanner(resp.Body)
+			scanner.Buffer(nil, streamScannerBuffer)
+			var param any
+			for scanner.Scan() {
+				line := scanner.Bytes()
+				appendAPIResponseChunk(ctx, e.cfg, line)
 
-			chunks := sdktranslator.TranslateStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), translated, bytes.Clone(payload), &param)
-			for i := range chunks {
-				out <- cliproxyexecutor.StreamChunk{Payload: []byte(chunks[i])}
+				// Filter usage metadata for all models
+				// Only retain usage statistics in the terminal chunk
+				line = FilterSSEUsageMetadata(line)
+
+				payload := jsonPayload(line)
+				if payload == nil {
+					continue
+				}
+
+				if detail, ok := parseAntigravityStreamUsage(payload); ok {
+					reporter.publish(ctx, detail)
+				}
+
+				chunks := sdktranslator.TranslateStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), translated, bytes.Clone(payload), &param)
+				for i := range chunks {
+					out <- cliproxyexecutor.StreamChunk{Payload: []byte(chunks[i])}
+				}
 			}
-		}
-		tail := sdktranslator.TranslateStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), translated, []byte("[DONE]"), &param)
-		for i := range tail {
-			out <- cliproxyexecutor.StreamChunk{Payload: []byte(tail[i])}
-		}
-		if errScan := scanner.Err(); errScan != nil {
-			recordAPIResponseError(ctx, e.cfg, errScan)
-			reporter.publishFailure(ctx)
-			out <- cliproxyexecutor.StreamChunk{Err: errScan}
-		} else {
-			reporter.ensurePublished(ctx)
-		}
-	}()
-	return stream, nil
+			tail := sdktranslator.TranslateStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), translated, []byte("[DONE]"), &param)
+			for i := range tail {
+				out <- cliproxyexecutor.StreamChunk{Payload: []byte(tail[i])}
+			}
+			if errScan := scanner.Err(); errScan != nil {
+				recordAPIResponseError(ctx, e.cfg, errScan)
+				reporter.publishFailure(ctx)
+				out <- cliproxyexecutor.StreamChunk{Err: errScan}
+			} else {
+				reporter.ensurePublished(ctx)
+			}
+		}(httpResp)
+		return stream, nil
+	}
+
+	switch {
+	case lastStatus != 0:
+		err = statusErr{code: lastStatus, msg: string(lastBody)}
+	case lastErr != nil:
+		err = lastErr
+	default:
+		err = statusErr{code: http.StatusServiceUnavailable, msg: "antigravity executor: no base url available"}
+	}
+	return nil, err
 }
 
 // Refresh refreshes the OAuth token using the refresh token.
@@ -230,57 +311,72 @@ func FetchAntigravityModels(ctx context.Context, auth *cliproxyauth.Auth, cfg *c
 		auth = updatedAuth
 	}
 
-	modelsURL := buildBaseURL(auth) + antigravityModelsPath
-	httpReq, errReq := http.NewRequestWithContext(ctx, http.MethodPost, modelsURL, bytes.NewReader([]byte(`{}`)))
-	if errReq != nil {
-		return nil
-	}
-	httpReq.Header.Set("Content-Type", "application/json")
-	httpReq.Header.Set("Authorization", "Bearer "+token)
-	httpReq.Header.Set("User-Agent", resolveUserAgent(auth))
-	if host := resolveHost(auth); host != "" {
-		httpReq.Host = host
-	}
-
+	baseURLs := antigravityBaseURLFallbackOrder(auth)
 	httpClient := newProxyAwareHTTPClient(ctx, cfg, auth, 0)
-	httpResp, errDo := httpClient.Do(httpReq)
-	if errDo != nil {
-		return nil
-	}
-	defer func() {
+
+	for idx, baseURL := range baseURLs {
+		modelsURL := baseURL + antigravityModelsPath
+		httpReq, errReq := http.NewRequestWithContext(ctx, http.MethodPost, modelsURL, bytes.NewReader([]byte(`{}`)))
+		if errReq != nil {
+			return nil
+		}
+		httpReq.Header.Set("Content-Type", "application/json")
+		httpReq.Header.Set("Authorization", "Bearer "+token)
+		httpReq.Header.Set("User-Agent", resolveUserAgent(auth))
+		if host := resolveHost(baseURL); host != "" {
+			httpReq.Host = host
+		}
+
+		httpResp, errDo := httpClient.Do(httpReq)
+		if errDo != nil {
+			if idx+1 < len(baseURLs) {
+				log.Debugf("antigravity executor: models request error on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
+				continue
+			}
+			return nil
+		}
+
+		bodyBytes, errRead := io.ReadAll(httpResp.Body)
 		if errClose := httpResp.Body.Close(); errClose != nil {
 			log.Errorf("antigravity executor: close response body error: %v", errClose)
 		}
-	}()
-
-	bodyBytes, errRead := io.ReadAll(httpResp.Body)
-	if errRead != nil {
-		return nil
-	}
-	if httpResp.StatusCode < http.StatusOK || httpResp.StatusCode >= http.StatusMultipleChoices {
-		return nil
-	}
-
-	result := gjson.GetBytes(bodyBytes, "models")
-	if !result.Exists() {
-		return nil
-	}
-
-	now := time.Now().Unix()
-	models := make([]*registry.ModelInfo, 0, len(result.Map()))
-	for id := range result.Map() {
-		id = modelName2Alias(id)
-		if id != "" {
-			models = append(models, &registry.ModelInfo{
-				ID:      id,
-				Object:  "model",
-				Created: now,
-				OwnedBy: antigravityAuthType,
-				Type:    antigravityAuthType,
-			})
+		if errRead != nil {
+			if idx+1 < len(baseURLs) {
+				log.Debugf("antigravity executor: models read error on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
+				continue
+			}
+			return nil
 		}
+		if httpResp.StatusCode < http.StatusOK || httpResp.StatusCode >= http.StatusMultipleChoices {
+			if httpResp.StatusCode == http.StatusTooManyRequests && idx+1 < len(baseURLs) {
+				log.Debugf("antigravity executor: models request rate limited on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
+				continue
+			}
+			return nil
+		}
+
+		result := gjson.GetBytes(bodyBytes, "models")
+		if !result.Exists() {
+			return nil
+		}
+
+		now := time.Now().Unix()
+		models := make([]*registry.ModelInfo, 0, len(result.Map()))
+		for id := range result.Map() {
+			id = modelName2Alias(id)
+			if id != "" {
+				models = append(models, &registry.ModelInfo{
+					ID:      id,
+					Object:  "model",
+					Created: now,
+					OwnedBy: antigravityAuthType,
+					Type:    antigravityAuthType,
+				})
+			}
+		}
+		return models
 	}
-	return models
+	return nil
 }
 
 func (e *AntigravityExecutor) ensureAccessToken(ctx context.Context, auth *cliproxyauth.Auth) (string, *cliproxyauth.Auth, error) {
@@ -366,12 +462,15 @@ func (e *AntigravityExecutor) refreshToken(ctx context.Context, auth *cliproxyau
 	return auth, nil
 }
 
-func (e *AntigravityExecutor) buildRequest(ctx context.Context, auth *cliproxyauth.Auth, token, modelName string, payload []byte, stream bool, alt string) (*http.Request, error) {
+func (e *AntigravityExecutor) buildRequest(ctx context.Context, auth *cliproxyauth.Auth, token, modelName string, payload []byte, stream bool, alt, baseURL string) (*http.Request, error) {
 	if token == "" {
 		return nil, statusErr{code: http.StatusUnauthorized, msg: "missing access token"}
 	}
 
-	base := buildBaseURL(auth)
+	base := strings.TrimSuffix(baseURL, "/")
+	if base == "" {
+		base = buildBaseURL(auth)
+	}
 	path := antigravityGeneratePath
 	if stream {
 		path = antigravityStreamPath
@@ -405,7 +504,7 @@ func (e *AntigravityExecutor) buildRequest(ctx context.Context, auth *cliproxyau
 	} else {
 		httpReq.Header.Set("Accept", "application/json")
 	}
-	if host := resolveHost(auth); host != "" {
+	if host := resolveHost(base); host != "" {
 		httpReq.Host = host
 	}
 
@@ -489,26 +588,13 @@ func int64Value(value any) (int64, bool) {
 }
 
 func buildBaseURL(auth *cliproxyauth.Auth) string {
-	if auth != nil {
-		if auth.Attributes != nil {
-			if v := strings.TrimSpace(auth.Attributes["base_url"]); v != "" {
-				return strings.TrimSuffix(v, "/")
-			}
-		}
-		if auth.Metadata != nil {
-			if v, ok := auth.Metadata["base_url"].(string); ok {
-				v = strings.TrimSpace(v)
-				if v != "" {
-					return strings.TrimSuffix(v, "/")
-				}
-			}
-		}
+	if baseURLs := antigravityBaseURLFallbackOrder(auth); len(baseURLs) > 0 {
+		return baseURLs[0]
 	}
-	return antigravityBaseURL
+	return antigravityBaseURLAutopush
 }
 
-func resolveHost(auth *cliproxyauth.Auth) string {
-	base := buildBaseURL(auth)
+func resolveHost(base string) string {
 	parsed, errParse := url.Parse(base)
 	if errParse != nil {
 		return ""
@@ -535,6 +621,37 @@ func resolveUserAgent(auth *cliproxyauth.Auth) string {
 	return defaultAntigravityAgent
 }
 
+func antigravityBaseURLFallbackOrder(auth *cliproxyauth.Auth) []string {
+	if base := resolveCustomAntigravityBaseURL(auth); base != "" {
+		return []string{base}
+	}
+	return []string{
+		antigravityBaseURLDaily,
+		antigravityBaseURLAutopush,
+		// antigravityBaseURLProd,
+	}
+}
+
+func resolveCustomAntigravityBaseURL(auth *cliproxyauth.Auth) string {
+	if auth == nil {
+		return ""
+	}
+	if auth.Attributes != nil {
+		if v := strings.TrimSpace(auth.Attributes["base_url"]); v != "" {
+			return strings.TrimSuffix(v, "/")
+		}
+	}
+	if auth.Metadata != nil {
+		if v, ok := auth.Metadata["base_url"].(string); ok {
+			v = strings.TrimSpace(v)
+			if v != "" {
+				return strings.TrimSuffix(v, "/")
+			}
+		}
+	}
+	return ""
+}
+
 func geminiToAntigravity(modelName string, payload []byte) []byte {
 	template, _ := sjson.Set(string(payload), "model", modelName)
 	template, _ = sjson.Set(template, "userAgent", "antigravity")
@@ -613,7 +730,7 @@ func modelName2Alias(modelName string) string {
 		return "gemini-claude-sonnet-4-5"
 	case "claude-sonnet-4-5-thinking":
 		return "gemini-claude-sonnet-4-5-thinking"
-	case "chat_20706", "chat_23310", "gemini-2.5-flash-thinking", "gemini-3-pro-low":
+	case "chat_20706", "chat_23310", "gemini-2.5-flash-thinking", "gemini-3-pro-low", "gemini-2.5-pro":
 		return ""
 	default:
 		return modelName