feat: centralize maxAttempts configuration via ExperimentFlags

This commit centralizes the retry attempt limits to be driven by the `ExperimentFlags.MAX_ATTEMPTS` flag or the user configuration, rather than being hardcoded throughout the codebase. The retry logic in `baseLlmClient`, `geminiChat`, `client`, and `web-fetch` has been updated to retrieve the `maxAttempts` setting directly from `Config`. It also addresses the removal of the previous 10-attempt cap in the Config initialization to allow tests simulating high retry limits to pass successfully.

packages/core/src/code_assist/experiments/flagNames.ts

@@ -20,6 +20,7 @@ export const ExperimentFlags = {
   PRO_MODEL_NO_ACCESS: 45768879,
   GEMINI_3_1_FLASH_LITE_LAUNCHED: 45771641,
   DEFAULT_REQUEST_TIMEOUT: 45773134,
+  MAX_ATTEMPTS: 45774515,
 } as const;
 
 export type ExperimentFlagName =

packages/core/src/config/config.test.ts

@@ -305,6 +305,53 @@ describe('Server Config (config.ts)', () => {
       });
       expect(config.getMaxAttempts()).toBe(DEFAULT_MAX_ATTEMPTS);
     });
+
+    it('should use experiment flag if present and valid', () => {
+      const config = new Config({
+        ...baseParams,
+        experiments: {
+          flags: {
+            [ExperimentFlags.MAX_ATTEMPTS]: {
+              intValue: '15',
+            },
+          },
+          experimentIds: [],
+        },
+      });
+      expect(config.getMaxAttempts()).toBe(15);
+    });
+
+    it('should fallback to maxAttempts if experiment flag is invalid', () => {
+      const config = new Config({
+        ...baseParams,
+        maxAttempts: 5,
+        experiments: {
+          flags: {
+            [ExperimentFlags.MAX_ATTEMPTS]: {
+              intValue: 'abc',
+            },
+          },
+          experimentIds: [],
+        },
+      });
+      expect(config.getMaxAttempts()).toBe(5);
+    });
+
+    it('should fallback to maxAttempts if experiment flag is non-positive', () => {
+      const config = new Config({
+        ...baseParams,
+        maxAttempts: 5,
+        experiments: {
+          flags: {
+            [ExperimentFlags.MAX_ATTEMPTS]: {
+              intValue: '0',
+            },
+          },
+          experimentIds: [],
+        },
+      });
+      expect(config.getMaxAttempts()).toBe(5);
+    });
   });
 
   beforeEach(() => {

packages/core/src/config/config.ts

@@ -3318,6 +3318,14 @@ export class Config implements McpContext, AgentLoopContext {
   }
 
   getMaxAttempts(): number {
+    const flagVal =
+      this.experiments?.flags?.[ExperimentFlags.MAX_ATTEMPTS]?.intValue;
+    if (flagVal !== undefined) {
+      const parsed = parseInt(flagVal, 10);
+      if (!isNaN(parsed) && parsed > 0) {
+        return parsed;
+      }
+    }
     return this.maxAttempts;
   }
 

packages/core/src/core/baseLlmClient.test.ts

@@ -252,7 +252,7 @@ describe('BaseLlmClient', () => {
       expect(retryWithBackoff).toHaveBeenCalledWith(
         expect.any(Function),
         expect.objectContaining({
-          maxAttempts: 5,
+          maxAttempts: 3,
         }),
       );
     });

packages/core/src/core/baseLlmClient.ts

@@ -36,8 +36,6 @@ import {
   createAvailabilityContextProvider,
 } from '../availability/policyHelpers.js';
 
-const DEFAULT_MAX_ATTEMPTS = 5;
-
 /**
  * Options for the generateJson utility function.
  */
@@ -328,7 +326,9 @@ export class BaseLlmClient {
       return await retryWithBackoff(apiCall, {
         shouldRetryOnContent,
         maxAttempts:
-          availabilityMaxAttempts ?? maxAttempts ?? DEFAULT_MAX_ATTEMPTS,
+          availabilityMaxAttempts ??
+          maxAttempts ??
+          this.config.getMaxAttempts(),
         getAvailabilityContext,
         onPersistent429: this.config.isInteractive()
           ? (authType, error) =>
@@ -339,7 +339,9 @@ export class BaseLlmClient {
         retryFetchErrors: this.config.getRetryFetchErrors(),
         onRetry: (attempt, error, delayMs) => {
           const actualMaxAttempts =
-            availabilityMaxAttempts ?? maxAttempts ?? DEFAULT_MAX_ATTEMPTS;
+            availabilityMaxAttempts ??
+            maxAttempts ??
+            this.config.getMaxAttempts();
           const modelName = getDisplayString(currentModel);
           const errorType = getRetryErrorType(error);
 

packages/core/src/core/client.ts

@@ -1133,7 +1133,7 @@ export class GeminiClient {
         onPersistent429: onPersistent429Callback,
         onValidationRequired: onValidationRequiredCallback,
         authType: this.config.getContentGeneratorConfig()?.authType,
-        maxAttempts: availabilityMaxAttempts,
+        maxAttempts: availabilityMaxAttempts ?? this.config.getMaxAttempts(),
         retryFetchErrors: this.config.getRetryFetchErrors(),
         getAvailabilityContext,
         onRetry: (attempt, error, delayMs) => {

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

@@ -176,7 +176,7 @@ describe('GeminiChat', () => {
       },
       getContentGenerator: vi.fn().mockReturnValue(mockContentGenerator),
       getRetryFetchErrors: vi.fn().mockReturnValue(false),
-      getMaxAttempts: vi.fn().mockReturnValue(10),
+      getMaxAttempts: vi.fn().mockReturnValue(4),
       getUserTier: vi.fn().mockReturnValue(undefined),
       modelConfigService: {
         getResolvedConfig: vi.fn().mockImplementation((modelConfigKey) => {

packages/core/src/core/geminiChat.ts

@@ -78,8 +78,6 @@ export type StreamEvent =
  * Options for retrying mid-stream errors (e.g. invalid content or API disconnects).
  */
 interface MidStreamRetryOptions {
-  /** Total number of attempts to make (1 initial + N retries). */
-  maxAttempts: number;
   /** The base delay in milliseconds for backoff. */
   initialDelayMs: number;
   /** Whether to use exponential backoff instead of linear. */
@@ -87,7 +85,6 @@ interface MidStreamRetryOptions {
 }
 
 const MID_STREAM_RETRY_OPTIONS: MidStreamRetryOptions = {
-  maxAttempts: 4, // 1 initial call + 3 retries mid-stream
   initialDelayMs: 1000,
   useExponentialBackoff: true,
 };
@@ -420,10 +417,8 @@ export class GeminiChat {
               : getRetryErrorType(error);
 
             if (isContentError || (isRetryable && !signal.aborted)) {
-              // The issue requests exactly 3 retries (4 attempts) for API errors during stream iteration.
-              // Regardless of the global maxAttempts (e.g. 10), we only want to retry these mid-stream API errors
-              // up to 3 times before finally throwing the error to the user.
-              const maxMidStreamAttempts = MID_STREAM_RETRY_OPTIONS.maxAttempts;
+              // We retry mid-stream API errors up to maxAttempts times before finally throwing the error to the user.
+              const maxMidStreamAttempts = this.context.config.getMaxAttempts();
 
               if (
                 attempt < maxAttempts - 1 &&

packages/core/src/tools/web-fetch.ts

@@ -309,6 +309,7 @@ class WebFetchToolInvocation extends BaseToolInvocation<
         return res;
       },
       {
+        maxAttempts: this.context.config.getMaxAttempts(),
         retryFetchErrors: this.context.config.getRetryFetchErrors(),
         onRetry: (attempt, error, delayMs) =>
           this.handleRetry(attempt, error, delayMs),
@@ -643,6 +644,7 @@ ${aggregatedContent}
           return res;
         },
         {
+          maxAttempts: this.context.config.getMaxAttempts(),
           retryFetchErrors: this.context.config.getRetryFetchErrors(),
           onRetry: (attempt, error, delayMs) =>
             this.handleRetry(attempt, error, delayMs),

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

@@ -9,12 +9,13 @@ import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 import { ApiError } from '@google/genai';
 import { AuthType } from '../core/contentGenerator.js';
 import { type HttpError, ModelNotFoundError } from './httpErrors.js';
-import { retryWithBackoff } from './retry.js';
+import { retryWithBackoff, isRetryableError } from './retry.js';
 import { setSimulate429 } from './testUtils.js';
 import { debugLogger } from './debugLogger.js';
 import {
   TerminalQuotaError,
   RetryableQuotaError,
+  ValidationRequiredError,
 } from './googleQuotaErrors.js';
 import { PREVIEW_GEMINI_MODEL } from '../config/models.js';
 import type { ModelPolicy } from '../availability/modelPolicy.js';
@@ -332,6 +333,81 @@ describe('retryWithBackoff', () => {
     });
   });
 
+  it('should call onRetry callback on each retry', async () => {
+    const mockFn = createFailingFunction(2);
+    const onRetry = vi.fn();
+    const promise = retryWithBackoff(mockFn, {
+      maxAttempts: 3,
+      initialDelayMs: 10,
+      onRetry,
+    });
+
+    await vi.runAllTimersAsync();
+
+    await promise;
+    expect(onRetry).toHaveBeenCalledTimes(2);
+    expect(onRetry).toHaveBeenCalledWith(
+      1,
+      expect.any(Error),
+      expect.any(Number),
+    );
+    expect(onRetry).toHaveBeenCalledWith(
+      2,
+      expect.any(Error),
+      expect.any(Number),
+    );
+  });
+
+  it('should handle ValidationRequiredError using onValidationRequired', async () => {
+    const error = new ValidationRequiredError('Validation required', {} as any);
+    let validationCalled = false;
+    const mockFn = vi.fn().mockImplementation(async () => {
+      if (!validationCalled) {
+        throw error;
+      }
+      return 'success';
+    });
+
+    const onValidationRequired = vi.fn().mockImplementation(async () => {
+      validationCalled = true;
+      return 'verify';
+    });
+
+    const promise = retryWithBackoff(mockFn, {
+      maxAttempts: 3,
+      initialDelayMs: 10,
+      onValidationRequired,
+    });
+
+    await vi.runAllTimersAsync();
+
+    const result = await promise;
+    expect(result).toBe('success');
+    expect(onValidationRequired).toHaveBeenCalledWith(error);
+    expect(mockFn).toHaveBeenCalledTimes(2);
+  });
+
+  it('should throw ValidationRequiredError if onValidationRequired returns cancel', async () => {
+    const error = new ValidationRequiredError('Validation required', {} as any);
+    const mockFn = vi.fn().mockImplementation(async () => {
+      throw error;
+    });
+
+    const onValidationRequired = vi.fn().mockResolvedValue('cancel');
+
+    const promise = retryWithBackoff(mockFn, {
+      maxAttempts: 3,
+      initialDelayMs: 10,
+      onValidationRequired,
+    });
+
+    await expect(promise).rejects.toThrow('Validation required');
+    await vi.runAllTimersAsync();
+
+    expect(error.userHandled).toBe(true);
+    expect(mockFn).toHaveBeenCalledTimes(1);
+  });
+
   describe('Fetch error retries', () => {
     it("should retry on 'fetch failed' when retryFetchErrors is true", async () => {
       const mockFn = vi.fn();
@@ -886,3 +962,37 @@ describe('retryWithBackoff', () => {
     });
   });
 });
+
+describe('isRetryableError', () => {
+  it('should return true for 429 errors', () => {
+    const error = new ApiError({ message: 'Quota exceeded', status: 429 });
+    expect(isRetryableError(error)).toBe(true);
+  });
+
+  it('should return true for 499 errors', () => {
+    const error = new ApiError({
+      message: 'Client closed request',
+      status: 499,
+    });
+    expect(isRetryableError(error)).toBe(true);
+  });
+
+  it('should return true for 500 errors', () => {
+    const error = new ApiError({
+      message: 'Internal Server Error',
+      status: 500,
+    });
+    expect(isRetryableError(error)).toBe(true);
+  });
+
+  it('should return false for 400 errors', () => {
+    const error = new ApiError({ message: 'Bad Request', status: 400 });
+    expect(isRetryableError(error)).toBe(false);
+  });
+
+  it('should return true for network error codes like ECONNRESET', () => {
+    const error = new Error('ECONNRESET');
+    (error as any).code = 'ECONNRESET';
+    expect(isRetryableError(error)).toBe(true);
+  });
+});

packages/core/src/utils/retry.ts

@@ -17,9 +17,18 @@ import { getErrorStatus, ModelNotFoundError } from './httpErrors.js';
 import type { RetryAvailabilityContext } from '../availability/modelPolicy.js';
 
 export type { RetryAvailabilityContext };
+
+/**
+ * Global fallback for maximum retry attempts when not explicitly provided.
+ * Most callers should use config.getMaxAttempts() instead.
+ */
 export const DEFAULT_MAX_ATTEMPTS = 10;
 
 export interface RetryOptions {
+  /**
+   * Total number of attempts (1 initial + N retries).
+   * Defaults to DEFAULT_MAX_ATTEMPTS (10) if not specified.
+   */
   maxAttempts: number;
   initialDelayMs: number;
   maxDelayMs: number;