Fix circular reference JSON serialization in telemetry logging (#4150)

packages/core/src/telemetry/clearcut-logger/clearcut-logger.ts

@@ -23,6 +23,7 @@ import {
   getCachedGoogleAccount,
   getLifetimeGoogleAccounts,
 } from '../../utils/user_account.js';
+import { safeJsonStringify } from '../../utils/safeJsonStringify.js';
 
 const start_session_event_name = 'start_session';
 const new_prompt_event_name = 'new_prompt';
@@ -65,7 +66,7 @@ export class ClearcutLogger {
     this.events.push([
       {
         event_time_ms: Date.now(),
-        source_extension_json: JSON.stringify(event),
+        source_extension_json: safeJsonStringify(event),
       },
     ]);
   }
@@ -121,7 +122,7 @@ export class ClearcutLogger {
           log_event: eventsToSend,
         },
       ];
-      const body = JSON.stringify(request);
+      const body = safeJsonStringify(request);
       const options = {
         hostname: 'play.googleapis.com',
         path: '/log',

packages/core/src/telemetry/integration.test.circular.ts

@@ -0,0 +1,62 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Integration test to verify circular reference handling with proxy agents
+ */
+
+import { describe, it, expect } from 'vitest';
+import { ClearcutLogger } from './clearcut-logger/clearcut-logger.js';
+import { Config } from '../config/config.js';
+
+describe('Circular Reference Integration Test', () => {
+  it('should handle HttpsProxyAgent-like circular references in clearcut logging', () => {
+    // Create a mock config with proxy
+    const mockConfig = {
+      getTelemetryEnabled: () => true,
+      getUsageStatisticsEnabled: () => true,
+      getSessionId: () => 'test-session',
+      getModel: () => 'test-model',
+      getEmbeddingModel: () => 'test-embedding',
+      getDebugMode: () => false,
+      getProxy: () => 'http://proxy.example.com:8080',
+    } as unknown as Config;
+
+    // Simulate the structure that causes the circular reference error
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const proxyAgentLike: any = {
+      sockets: {},
+      options: { proxy: 'http://proxy.example.com:8080' },
+    };
+
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const socketLike: any = {
+      _httpMessage: {
+        agent: proxyAgentLike,
+        socket: null,
+      },
+    };
+
+    socketLike._httpMessage.socket = socketLike; // Create circular reference
+    proxyAgentLike.sockets['cloudcode-pa.googleapis.com:443'] = [socketLike];
+
+    // Create an event that would contain this circular structure
+    const problematicEvent = {
+      error: new Error('Network error'),
+      function_args: {
+        filePath: '/test/file.txt',
+        httpAgent: proxyAgentLike, // This would cause the circular reference
+      },
+    };
+
+    // Test that ClearcutLogger can handle this
+    const logger = ClearcutLogger.getInstance(mockConfig);
+
+    expect(() => {
+      logger?.enqueueLogEvent(problematicEvent);
+    }).not.toThrow();
+  });
+});

packages/core/src/telemetry/loggers.test.circular.ts

@@ -0,0 +1,119 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Test to verify circular reference handling in telemetry logging
+ */
+
+import { describe, it, expect } from 'vitest';
+import { logToolCall } from './loggers.js';
+import { ToolCallEvent } from './types.js';
+import { Config } from '../config/config.js';
+import { CompletedToolCall } from '../core/coreToolScheduler.js';
+import { ToolCallRequestInfo, ToolCallResponseInfo } from '../core/turn.js';
+import { Tool } from '../tools/tools.js';
+
+describe('Circular Reference Handling', () => {
+  it('should handle circular references in tool function arguments', () => {
+    // Create a mock config
+    const mockConfig = {
+      getTelemetryEnabled: () => true,
+      getUsageStatisticsEnabled: () => true,
+      getSessionId: () => 'test-session',
+      getModel: () => 'test-model',
+      getEmbeddingModel: () => 'test-embedding',
+      getDebugMode: () => false,
+    } as unknown as Config;
+
+    // Create an object with circular references (similar to HttpsProxyAgent)
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const circularObject: any = {
+      sockets: {},
+      agent: null,
+    };
+    circularObject.agent = circularObject; // Create circular reference
+    circularObject.sockets['test-host'] = [
+      { _httpMessage: { agent: circularObject } },
+    ];
+
+    // Create a mock CompletedToolCall with circular references in function_args
+    const mockRequest: ToolCallRequestInfo = {
+      callId: 'test-call-id',
+      name: 'ReadFile',
+      args: circularObject, // This would cause the original error
+      isClientInitiated: false,
+      prompt_id: 'test-prompt-id',
+    };
+
+    const mockResponse: ToolCallResponseInfo = {
+      callId: 'test-call-id',
+      responseParts: [{ text: 'test result' }],
+      resultDisplay: undefined,
+      error: undefined, // undefined means success
+    };
+
+    const mockCompletedToolCall: CompletedToolCall = {
+      status: 'success',
+      request: mockRequest,
+      response: mockResponse,
+      tool: {} as Tool,
+      durationMs: 100,
+    };
+
+    // Create a tool call event with circular references in function_args
+    const event = new ToolCallEvent(mockCompletedToolCall);
+
+    // This should not throw an error
+    expect(() => {
+      logToolCall(mockConfig, event);
+    }).not.toThrow();
+  });
+
+  it('should handle normal objects without circular references', () => {
+    const mockConfig = {
+      getTelemetryEnabled: () => true,
+      getUsageStatisticsEnabled: () => true,
+      getSessionId: () => 'test-session',
+      getModel: () => 'test-model',
+      getEmbeddingModel: () => 'test-embedding',
+      getDebugMode: () => false,
+    } as unknown as Config;
+
+    const normalObject = {
+      filePath: '/test/path',
+      options: { encoding: 'utf8' },
+    };
+
+    const mockRequest: ToolCallRequestInfo = {
+      callId: 'test-call-id',
+      name: 'ReadFile',
+      args: normalObject,
+      isClientInitiated: false,
+      prompt_id: 'test-prompt-id',
+    };
+
+    const mockResponse: ToolCallResponseInfo = {
+      callId: 'test-call-id',
+      responseParts: [{ text: 'test result' }],
+      resultDisplay: undefined,
+      error: undefined, // undefined means success
+    };
+
+    const mockCompletedToolCall: CompletedToolCall = {
+      status: 'success',
+      request: mockRequest,
+      response: mockResponse,
+      tool: {} as Tool,
+      durationMs: 100,
+    };
+
+    const event = new ToolCallEvent(mockCompletedToolCall);
+
+    expect(() => {
+      logToolCall(mockConfig, event);
+    }).not.toThrow();
+  });
+});

packages/core/src/telemetry/loggers.ts

@@ -35,6 +35,7 @@ import {
 import { isTelemetrySdkInitialized } from './sdk.js';
 import { uiTelemetryService, UiEvent } from './uiTelemetry.js';
 import { ClearcutLogger } from './clearcut-logger/clearcut-logger.js';
+import { safeJsonStringify } from '../utils/safeJsonStringify.js';
 
 const shouldLogUserPrompts = (config: Config): boolean =>
   config.getTelemetryLogPromptsEnabled();
@@ -115,7 +116,7 @@ export function logToolCall(config: Config, event: ToolCallEvent): void {
     ...event,
     'event.name': EVENT_TOOL_CALL,
     'event.timestamp': new Date().toISOString(),
-    function_args: JSON.stringify(event.function_args, null, 2),
+    function_args: safeJsonStringify(event.function_args, 2),
   };
   if (event.error) {
     attributes['error.message'] = event.error;

packages/core/src/utils/quotaErrorDetection.ts

@@ -44,20 +44,9 @@ export function isProQuotaExceededError(error: unknown): boolean {
   // - "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 => {
+  const checkMessage = (message: string): boolean =>
-    console.log('[DEBUG] isProQuotaExceededError checking message:', message);
+    message.includes("Quota exceeded for quota metric 'Gemini") &&
-    const result =
+    message.includes("Pro Requests'");
-      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);

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

@@ -0,0 +1,73 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import { safeJsonStringify } from './safeJsonStringify.js';
+
+describe('safeJsonStringify', () => {
+  it('should stringify normal objects without issues', () => {
+    const obj = { name: 'test', value: 42 };
+    const result = safeJsonStringify(obj);
+    expect(result).toBe('{"name":"test","value":42}');
+  });
+
+  it('should handle circular references by replacing them with [Circular]', () => {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const obj: any = { name: 'test' };
+    obj.circular = obj; // Create circular reference
+
+    const result = safeJsonStringify(obj);
+    expect(result).toBe('{"name":"test","circular":"[Circular]"}');
+  });
+
+  it('should handle complex circular structures like HttpsProxyAgent', () => {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const agent: any = {
+      sockets: {},
+      options: { host: 'example.com' },
+    };
+    agent.sockets['example.com'] = [{ agent }];
+
+    const result = safeJsonStringify(agent);
+    expect(result).toContain('[Circular]');
+    expect(result).toContain('example.com');
+  });
+
+  it('should respect the space parameter for formatting', () => {
+    const obj = { name: 'test', value: 42 };
+    const result = safeJsonStringify(obj, 2);
+    expect(result).toBe('{\n  "name": "test",\n  "value": 42\n}');
+  });
+
+  it('should handle circular references with formatting', () => {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const obj: any = { name: 'test' };
+    obj.circular = obj;
+
+    const result = safeJsonStringify(obj, 2);
+    expect(result).toBe('{\n  "name": "test",\n  "circular": "[Circular]"\n}');
+  });
+
+  it('should handle arrays with circular references', () => {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const arr: any[] = [{ id: 1 }];
+    arr[0].parent = arr; // Create circular reference
+
+    const result = safeJsonStringify(arr);
+    expect(result).toBe('[{"id":1,"parent":"[Circular]"}]');
+  });
+
+  it('should handle null and undefined values', () => {
+    expect(safeJsonStringify(null)).toBe('null');
+    expect(safeJsonStringify(undefined)).toBe(undefined);
+  });
+
+  it('should handle primitive values', () => {
+    expect(safeJsonStringify('test')).toBe('"test"');
+    expect(safeJsonStringify(42)).toBe('42');
+    expect(safeJsonStringify(true)).toBe('true');
+  });
+});

packages/core/src/utils/safeJsonStringify.ts

@@ -0,0 +1,32 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Safely stringifies an object to JSON, handling circular references by replacing them with [Circular].
+ *
+ * @param obj - The object to stringify
+ * @param space - Optional space parameter for formatting (defaults to no formatting)
+ * @returns JSON string with circular references replaced by [Circular]
+ */
+export function safeJsonStringify(
+  obj: unknown,
+  space?: string | number,
+): string {
+  const seen = new WeakSet();
+  return JSON.stringify(
+    obj,
+    (key, value) => {
+      if (typeof value === 'object' && value !== null) {
+        if (seen.has(value)) {
+          return '[Circular]';
+        }
+        seen.add(value);
+      }
+      return value;
+    },
+    space,
+  );
+}