Remove auto-execution on Flash in the event of a 429/Quota failover (#3662)

Co-authored-by: Jenna Inouye <jinouye@google.com>

packages/core/src/code_assist/server.ts

@@ -31,7 +31,23 @@ import {
   toCountTokenRequest,
   toGenerateContentRequest,
 } from './converter.js';
-import { PassThrough } from 'node:stream';
+import { Readable } from 'node:stream';
+
+interface ErrorData {
+  error?: {
+    message?: string;
+  };
+}
+
+interface GaxiosResponse {
+  status: number;
+  data: unknown;
+}
+
+interface StreamError extends Error {
+  status?: number;
+  response?: GaxiosResponse;
+}
 
 /** HTTP options to be used in each of the requests. */
 export interface HttpOptions {
@@ -177,8 +193,45 @@ export class CodeAssistServer implements ContentGenerator {
     });
 
     return (async function* (): AsyncGenerator<T> {
+      // Convert ReadableStream to Node.js stream if needed
+      let nodeStream: NodeJS.ReadableStream;
+
+      if (res.data instanceof ReadableStream) {
+        // Convert Web ReadableStream to Node.js Readable stream
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        nodeStream = Readable.fromWeb(res.data as any);
+      } else if (
+        res.data &&
+        typeof (res.data as NodeJS.ReadableStream).on === 'function'
+      ) {
+        // Already a Node.js stream
+        nodeStream = res.data as NodeJS.ReadableStream;
+      } else {
+        // If res.data is not a stream, it might be an error response
+        // Try to extract error information from the response
+        let errorMessage =
+          'Response data is not a readable stream. This may indicate a server error or quota issue.';
+
+        if (res.data && typeof res.data === 'object') {
+          // Check if this is an error response with error details
+          const errorData = res.data as ErrorData;
+          if (errorData.error?.message) {
+            errorMessage = errorData.error.message;
+          } else if (typeof errorData === 'string') {
+            errorMessage = errorData;
+          }
+        }
+
+        // Create an error that looks like a quota error if it contains quota information
+        const error: StreamError = new Error(errorMessage);
+        // Add status and response properties so it can be properly handled by retry logic
+        error.status = res.status;
+        error.response = res;
+        throw error;
+      }
+
       const rl = readline.createInterface({
-        input: res.data as PassThrough,
+        input: nodeStream,
         crlfDelay: Infinity, // Recognizes '\r\n' and '\n' as line breaks
       });
 

packages/core/src/config/config.ts

@@ -104,7 +104,7 @@ export type FlashFallbackHandler = (
   currentModel: string,
   fallbackModel: string,
   error?: unknown,
-) => Promise<boolean>;
+) => Promise<boolean | string | null>;
 
 export interface ConfigParameters {
   sessionId: string;
@@ -183,6 +183,7 @@ export class Config {
   private readonly listExtensions: boolean;
   private readonly _activeExtensions: ActiveExtension[];
   flashFallbackHandler?: FlashFallbackHandler;
+  private quotaErrorOccurred: boolean = false;
 
   constructor(params: ConfigParameters) {
     this.sessionId = params.sessionId;
@@ -304,6 +305,14 @@ export class Config {
     this.flashFallbackHandler = handler;
   }
 
+  setQuotaErrorOccurred(value: boolean): void {
+    this.quotaErrorOccurred = value;
+  }
+
+  getQuotaErrorOccurred(): boolean {
+    return this.quotaErrorOccurred;
+  }
+
   getEmbeddingModel(): string {
     return this.embeddingModel;
   }

packages/core/src/core/client.test.ts

@@ -178,6 +178,8 @@ describe('Gemini Client (client.ts)', () => {
         getProxy: vi.fn().mockReturnValue(undefined),
         getWorkingDir: vi.fn().mockReturnValue('/test/dir'),
         getFileService: vi.fn().mockReturnValue(fileService),
+        getQuotaErrorOccurred: vi.fn().mockReturnValue(false),
+        setQuotaErrorOccurred: vi.fn(),
       };
       return mock as unknown as Config;
     });
@@ -351,7 +353,7 @@ describe('Gemini Client (client.ts)', () => {
       await client.generateJson(contents, schema, abortSignal);
 
       expect(mockGenerateContentFn).toHaveBeenCalledWith({
-        model: DEFAULT_GEMINI_FLASH_MODEL,
+        model: 'test-model', // Should use current model from config
         config: {
           abortSignal,
           systemInstruction: getCoreSystemPrompt(''),

packages/core/src/core/client.ts

@@ -262,6 +262,7 @@ export class GeminiClient {
     request: PartListUnion,
     signal: AbortSignal,
     turns: number = this.MAX_TURNS,
+    originalModel?: string,
   ): AsyncGenerator<ServerGeminiStreamEvent, Turn> {
     // Ensure turns never exceeds MAX_TURNS to prevent infinite loops
     const boundedTurns = Math.min(turns, this.MAX_TURNS);
@@ -269,6 +270,9 @@ export class GeminiClient {
       return new Turn(this.getChat());
     }
 
+    // Track the original model from the first call to detect model switching
+    const initialModel = originalModel || this.config.getModel();
+
     const compressed = await this.tryCompressChat();
     if (compressed) {
       yield { type: GeminiEventType.ChatCompressed, value: compressed };
@@ -279,6 +283,14 @@ export class GeminiClient {
       yield event;
     }
     if (!turn.pendingToolCalls.length && signal && !signal.aborted) {
+      // Check if model was switched during the call (likely due to quota error)
+      const currentModel = this.config.getModel();
+      if (currentModel !== initialModel) {
+        // Model was switched (likely due to quota error fallback)
+        // Don't continue with recursive call to prevent unwanted Flash execution
+        return turn;
+      }
+
       const nextSpeakerCheck = await checkNextSpeaker(
         this.getChat(),
         this,
@@ -288,7 +300,12 @@ export class GeminiClient {
         const nextRequest = [{ text: 'Please continue.' }];
         // This recursive call's events will be yielded out, but the final
         // turn object will be from the top-level call.
-        yield* this.sendMessageStream(nextRequest, signal, boundedTurns - 1);
+        yield* this.sendMessageStream(
+          nextRequest,
+          signal,
+          boundedTurns - 1,
+          initialModel,
+        );
       }
     }
     return turn;
@@ -298,9 +315,12 @@ export class GeminiClient {
     contents: Content[],
     schema: SchemaUnion,
     abortSignal: AbortSignal,
-    model: string = DEFAULT_GEMINI_FLASH_MODEL,
+    model?: string,
     config: GenerateContentConfig = {},
   ): Promise<Record<string, unknown>> {
+    // Use current model from config instead of hardcoded Flash model
+    const modelToUse =
+      model || this.config.getModel() || DEFAULT_GEMINI_FLASH_MODEL;
     try {
       const userMemory = this.config.getUserMemory();
       const systemInstruction = getCoreSystemPrompt(userMemory);
@@ -312,7 +332,7 @@ export class GeminiClient {
 
       const apiCall = () =>
         this.getContentGenerator().generateContent({
-          model,
+          model: modelToUse,
           config: {
             ...requestConfig,
             systemInstruction,
@@ -585,10 +605,14 @@ export class GeminiClient {
           fallbackModel,
           error,
         );
-        if (accepted) {
+        if (accepted !== false && accepted !== null) {
           this.config.setModel(fallbackModel);
           return fallbackModel;
         }
+        // Check if the model was switched manually in the handler
+        if (this.config.getModel() === fallbackModel) {
+          return null; // Model was switched but don't continue with current prompt
+        }
       } catch (error) {
         console.warn('Flash fallback handler failed:', error);
       }

packages/core/src/core/geminiChat.test.ts

@@ -43,6 +43,8 @@ describe('GeminiChat', () => {
       }),
       getModel: vi.fn().mockReturnValue('gemini-pro'),
       setModel: vi.fn(),
+      getQuotaErrorOccurred: vi.fn().mockReturnValue(false),
+      setQuotaErrorOccurred: vi.fn(),
       flashFallbackHandler: undefined,
     } as unknown as Config;
 

packages/core/src/core/geminiChat.ts

@@ -217,10 +217,14 @@ export class GeminiChat {
           fallbackModel,
           error,
         );
-        if (accepted) {
+        if (accepted !== false && accepted !== null) {
           this.config.setModel(fallbackModel);
           return fallbackModel;
         }
+        // Check if the model was switched manually in the handler
+        if (this.config.getModel() === fallbackModel) {
+          return null; // Model was switched but don't continue with current prompt
+        }
       } catch (error) {
         console.warn('Flash fallback handler failed:', error);
       }
@@ -262,12 +266,25 @@ export class GeminiChat {
     let response: GenerateContentResponse;
 
     try {
-      const apiCall = () =>
-        this.contentGenerator.generateContent({
-          model: this.config.getModel() || DEFAULT_GEMINI_FLASH_MODEL,
+      const apiCall = () => {
+        const modelToUse = this.config.getModel() || DEFAULT_GEMINI_FLASH_MODEL;
+
+        // Prevent Flash model calls immediately after quota error
+        if (
+          this.config.getQuotaErrorOccurred() &&
+          modelToUse === DEFAULT_GEMINI_FLASH_MODEL
+        ) {
+          throw new Error(
+            'Please submit a new query to continue with the Flash model.',
+          );
+        }
+
+        return this.contentGenerator.generateContent({
+          model: modelToUse,
           contents: requestContents,
           config: { ...this.generationConfig, ...params.config },
         });
+      };
 
       response = await retryWithBackoff(apiCall, {
         shouldRetry: (error: Error) => {
@@ -354,12 +371,25 @@ export class GeminiChat {
     const startTime = Date.now();
 
     try {
-      const apiCall = () =>
-        this.contentGenerator.generateContentStream({
-          model: this.config.getModel(),
+      const apiCall = () => {
+        const modelToUse = this.config.getModel();
+
+        // Prevent Flash model calls immediately after quota error
+        if (
+          this.config.getQuotaErrorOccurred() &&
+          modelToUse === DEFAULT_GEMINI_FLASH_MODEL
+        ) {
+          throw new Error(
+            'Please submit a new query to continue with the Flash model.',
+          );
+        }
+
+        return this.contentGenerator.generateContentStream({
+          model: modelToUse,
           contents: requestContents,
           config: { ...this.generationConfig, ...params.config },
         });
+      };
 
       // Note: Retrying streams can be complex. If generateContentStream itself doesn't handle retries
       // for transient issues internally before yielding the async generator, this retry will re-initiate

packages/core/src/utils/editCorrector.test.ts

@@ -214,6 +214,8 @@ describe('editCorrector', () => {
         setAlwaysSkipModificationConfirmation: vi.fn((skip: boolean) => {
           configParams.alwaysSkipModificationConfirmation = skip;
         }),
+        getQuotaErrorOccurred: vi.fn().mockReturnValue(false),
+        setQuotaErrorOccurred: vi.fn(),
       } as unknown as Config;
 
       callCount = 0;
@@ -654,6 +656,8 @@ describe('editCorrector', () => {
         setAlwaysSkipModificationConfirmation: vi.fn((skip: boolean) => {
           configParams.alwaysSkipModificationConfirmation = skip;
         }),
+        getQuotaErrorOccurred: vi.fn().mockReturnValue(false),
+        setQuotaErrorOccurred: vi.fn(),
       } as unknown as Config;
 
       callCount = 0;

packages/core/src/utils/quotaErrorDetection.ts

@@ -41,14 +41,23 @@ export function isProQuotaExceededError(error: unknown): boolean {
   // Check for Pro quota exceeded errors by looking for the specific pattern
   // This will match patterns like:
   // - "Quota exceeded for quota metric 'Gemini 2.5 Pro Requests'"
-  // - "Quota exceeded for quota metric 'Gemini 1.5-preview Pro Requests'"
-  // - "Quota exceeded for quota metric 'Gemini beta-3.0 Pro Requests'"
-  // - "Quota exceeded for quota metric 'Gemini experimental-v2 Pro Requests'"
+  // - "Quota exceeded for quota metric 'Gemini 2.5-preview Pro Requests'"
   // We use string methods instead of regex to avoid ReDoS vulnerabilities
 
-  const checkMessage = (message: string): boolean =>
-    message.includes("Quota exceeded for quota metric 'Gemini") &&
-    message.includes("Pro Requests'");
+  const checkMessage = (message: string): boolean => {
+    console.log('[DEBUG] isProQuotaExceededError checking message:', message);
+    const result =
+      message.includes("Quota exceeded for quota metric 'Gemini") &&
+      message.includes("Pro Requests'");
+    console.log('[DEBUG] isProQuotaExceededError result:', result);
+    return result;
+  };
+
+  // Log the full error object to understand its structure
+  console.log(
+    '[DEBUG] isProQuotaExceededError - full error object:',
+    JSON.stringify(error, null, 2),
+  );
 
   if (typeof error === 'string') {
     return checkMessage(error);
@@ -62,6 +71,38 @@ export function isProQuotaExceededError(error: unknown): boolean {
     return checkMessage(error.error.message);
   }
 
+  // Check if it's a Gaxios error with response data
+  if (error && typeof error === 'object' && 'response' in error) {
+    const gaxiosError = error as {
+      response?: {
+        data?: unknown;
+      };
+    };
+    if (gaxiosError.response && gaxiosError.response.data) {
+      console.log(
+        '[DEBUG] isProQuotaExceededError - checking response data:',
+        gaxiosError.response.data,
+      );
+      if (typeof gaxiosError.response.data === 'string') {
+        return checkMessage(gaxiosError.response.data);
+      }
+      if (
+        typeof gaxiosError.response.data === 'object' &&
+        gaxiosError.response.data !== null &&
+        'error' in gaxiosError.response.data
+      ) {
+        const errorData = gaxiosError.response.data as {
+          error?: { message?: string };
+        };
+        return checkMessage(errorData.error?.message || '');
+      }
+    }
+  }
+
+  console.log(
+    '[DEBUG] isProQuotaExceededError - no matching error format for:',
+    error,
+  );
   return false;
 }
 

packages/core/src/utils/retry.ts

@@ -18,7 +18,7 @@ export interface RetryOptions {
   onPersistent429?: (
     authType?: string,
     error?: unknown,
-  ) => Promise<string | null>;
+  ) => Promise<string | boolean | null>;
   authType?: string;
 }
 
@@ -102,13 +102,16 @@ export async function retryWithBackoff<T>(
       ) {
         try {
           const fallbackModel = await onPersistent429(authType, error);
-          if (fallbackModel) {
+          if (fallbackModel !== false && fallbackModel !== null) {
             // Reset attempt counter and try with new model
             attempt = 0;
             consecutive429Count = 0;
             currentDelay = initialDelayMs;
             // With the model updated, we continue to the next attempt
             continue;
+          } else {
+            // Fallback handler returned null/false, meaning don't continue - stop retry process
+            throw error;
           }
         } catch (fallbackError) {
           // If fallback fails, continue with original error
@@ -126,13 +129,16 @@ export async function retryWithBackoff<T>(
       ) {
         try {
           const fallbackModel = await onPersistent429(authType, error);
-          if (fallbackModel) {
+          if (fallbackModel !== false && fallbackModel !== null) {
             // Reset attempt counter and try with new model
             attempt = 0;
             consecutive429Count = 0;
             currentDelay = initialDelayMs;
             // With the model updated, we continue to the next attempt
             continue;
+          } else {
+            // Fallback handler returned null/false, meaning don't continue - stop retry process
+            throw error;
           }
         } catch (fallbackError) {
           // If fallback fails, continue with original error
@@ -155,13 +161,16 @@ export async function retryWithBackoff<T>(
       ) {
         try {
           const fallbackModel = await onPersistent429(authType, error);
-          if (fallbackModel) {
+          if (fallbackModel !== false && fallbackModel !== null) {
             // Reset attempt counter and try with new model
             attempt = 0;
             consecutive429Count = 0;
             currentDelay = initialDelayMs;
             // With the model updated, we continue to the next attempt
             continue;
+          } else {
+            // Fallback handler returned null/false, meaning don't continue - stop retry process
+            throw error;
           }
         } catch (fallbackError) {
           // If fallback fails, continue with original error