feat(executor): update system instruction handling for Claude and Gemini-3-Pro models

internal/runtime/executor/antigravity_executor.go

@@ -45,7 +45,6 @@ const (
 	defaultAntigravityAgent        = "antigravity/1.104.0 darwin/arm64"
 	antigravityAuthType            = "antigravity"
 	refreshSkew                    = 3000 * time.Second
-	tokenRefreshTimeout            = 30 * time.Second
 )
 
 var (
@@ -78,7 +77,7 @@ func (e *AntigravityExecutor) PrepareRequest(_ *http.Request, _ *cliproxyauth.Au
 // Execute performs a non-streaming request to the Antigravity API.
 func (e *AntigravityExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, req cliproxyexecutor.Request, opts cliproxyexecutor.Options) (resp cliproxyexecutor.Response, err error) {
 	isClaude := strings.Contains(strings.ToLower(req.Model), "claude")
-	if isClaude {
+	if isClaude || strings.Contains(req.Model, "gemini-3-pro") {
 		return e.executeClaudeNonStream(ctx, auth, req, opts)
 	}
 
@@ -951,7 +950,7 @@ func (e *AntigravityExecutor) refreshToken(ctx context.Context, auth *cliproxyau
 	httpReq.Header.Set("User-Agent", defaultAntigravityAgent)
 	httpReq.Header.Set("Content-Type", "application/x-www-form-urlencoded")
 
-	httpClient := newProxyAwareHTTPClient(ctx, e.cfg, auth, tokenRefreshTimeout)
+	httpClient := newProxyAwareHTTPClient(ctx, e.cfg, auth, 0)
 	httpResp, errDo := httpClient.Do(httpReq)
 	if errDo != nil {
 		return auth, errDo
@@ -1048,6 +1047,19 @@ func (e *AntigravityExecutor) buildRequest(ctx context.Context, auth *cliproxyau
 		payload = []byte(strJSON)
 	}
 
+	if strings.Contains(modelName, "claude") || strings.Contains(modelName, "gemini-3-pro") {
+		systemInstructionPartsResult := gjson.GetBytes(payload, "request.systemInstruction.parts")
+
+		payload, _ = sjson.SetBytes(payload, "request.systemInstruction.role", "user")
+		payload, _ = sjson.SetBytes(payload, "request.systemInstruction.parts.0.text", "You are Antigravity, a powerful agentic AI coding assistant designed by the Google Deepmind team working on Advanced Agentic Coding.You are pair programming with a USER to solve their coding task. The task may require creating a new codebase, modifying or debugging an existing codebase, or simply answering a question.**Absolute paths only****Proactiveness**")
+
+		if systemInstructionPartsResult.Exists() && systemInstructionPartsResult.IsArray() {
+			for _, partResult := range systemInstructionPartsResult.Array() {
+				payload, _ = sjson.SetRawBytes(payload, "request.systemInstruction.parts.-1", []byte(partResult.Raw))
+			}
+		}
+	}
+
 	httpReq, errReq := http.NewRequestWithContext(ctx, http.MethodPost, requestURL.String(), bytes.NewReader(payload))
 	if errReq != nil {
 		return nil, errReq
@@ -1182,8 +1194,8 @@ func antigravityBaseURLFallbackOrder(auth *cliproxyauth.Auth) []string {
 		return []string{base}
 	}
 	return []string{
-		antigravityBaseURLDaily,
 		antigravitySandboxBaseURLDaily,
+		antigravityBaseURLDaily,
 		antigravityBaseURLProd,
 	}
 }
@@ -1211,6 +1223,7 @@ func resolveCustomAntigravityBaseURL(auth *cliproxyauth.Auth) string {
 func geminiToAntigravity(modelName string, payload []byte, projectID string) []byte {
 	template, _ := sjson.Set(string(payload), "model", modelName)
 	template, _ = sjson.Set(template, "userAgent", "antigravity")
+	template, _ = sjson.Set(template, "requestType", "agent")
 
 	// Use real project ID from auth if available, otherwise generate random (legacy fallback)
 	if projectID != "" {