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

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();
+  });
+});