feat(core): add robustness tests, logging, and metrics for CodeAssistServer SSE parsing (#21013)

Co-authored-by: Yuna Seol <yunaseol@google.com>

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

@@ -33,6 +33,7 @@ import {
   logFlashFallback,
   logChatCompression,
   logMalformedJsonResponse,
+  logInvalidChunk,
   logFileOperation,
   logRipgrepFallback,
   logToolOutputTruncated,
@@ -68,6 +69,7 @@ import {
   EVENT_AGENT_START,
   EVENT_AGENT_FINISH,
   EVENT_WEB_FETCH_FALLBACK_ATTEMPT,
+  EVENT_INVALID_CHUNK,
   ApiErrorEvent,
   ApiRequestEvent,
   ApiResponseEvent,
@@ -77,6 +79,7 @@ import {
   FlashFallbackEvent,
   RipgrepFallbackEvent,
   MalformedJsonResponseEvent,
+  InvalidChunkEvent,
   makeChatCompressionEvent,
   FileOperationEvent,
   ToolOutputTruncatedEvent,
@@ -1736,6 +1739,39 @@ describe('loggers', () => {
     });
   });
 
+  describe('logInvalidChunk', () => {
+    beforeEach(() => {
+      vi.spyOn(ClearcutLogger.prototype, 'logInvalidChunkEvent');
+      vi.spyOn(metrics, 'recordInvalidChunk');
+    });
+
+    it('logs the event to Clearcut and OTEL', () => {
+      const mockConfig = makeFakeConfig();
+      const event = new InvalidChunkEvent('Unexpected token');
+
+      logInvalidChunk(mockConfig, event);
+
+      expect(
+        ClearcutLogger.prototype.logInvalidChunkEvent,
+      ).toHaveBeenCalledWith(event);
+
+      expect(mockLogger.emit).toHaveBeenCalledWith({
+        body: 'Invalid chunk received from stream.',
+        attributes: {
+          'session.id': 'test-session-id',
+          'user.email': 'test-user@example.com',
+          'installation.id': 'test-installation-id',
+          'event.name': EVENT_INVALID_CHUNK,
+          'event.timestamp': '2025-01-01T00:00:00.000Z',
+          interactive: false,
+          'error.message': 'Unexpected token',
+        },
+      });
+
+      expect(metrics.recordInvalidChunk).toHaveBeenCalledWith(mockConfig);
+    });
+  });
+
   describe('logFileOperation', () => {
     const mockConfig = {
       getSessionId: () => 'test-session-id',

packages/core/src/telemetry/loggers.ts

@@ -29,6 +29,7 @@ import {
   type ConversationFinishedEvent,
   type ChatCompressionEvent,
   type MalformedJsonResponseEvent,
+  type InvalidChunkEvent,
   type ContentRetryEvent,
   type ContentRetryFailureEvent,
   type RipgrepFallbackEvent,
@@ -75,6 +76,7 @@ import {
   recordPlanExecution,
   recordKeychainAvailability,
   recordTokenStorageInitialization,
+  recordInvalidChunk,
 } from './metrics.js';
 import { bufferTelemetryEvent } from './sdk.js';
 import { uiTelemetryService, type UiEvent } from './uiTelemetry.js';
@@ -467,6 +469,22 @@ export function logMalformedJsonResponse(
   });
 }
 
+export function logInvalidChunk(
+  config: Config,
+  event: InvalidChunkEvent,
+): void {
+  ClearcutLogger.getInstance(config)?.logInvalidChunkEvent(event);
+  bufferTelemetryEvent(() => {
+    const logger = logs.getLogger(SERVICE_NAME);
+    const logRecord: LogRecord = {
+      body: event.toLogBody(),
+      attributes: event.toOpenTelemetryAttributes(config),
+    };
+    logger.emit(logRecord);
+    recordInvalidChunk(config);
+  });
+}
+
 export function logContentRetry(
   config: Config,
   event: ContentRetryEvent,

packages/core/src/telemetry/metrics.test.ts

@@ -105,6 +105,7 @@ describe('Telemetry Metrics', () => {
   let recordPlanExecutionModule: typeof import('./metrics.js').recordPlanExecution;
   let recordKeychainAvailabilityModule: typeof import('./metrics.js').recordKeychainAvailability;
   let recordTokenStorageInitializationModule: typeof import('./metrics.js').recordTokenStorageInitialization;
+  let recordInvalidChunkModule: typeof import('./metrics.js').recordInvalidChunk;
 
   beforeEach(async () => {
     vi.resetModules();
@@ -154,6 +155,7 @@ describe('Telemetry Metrics', () => {
       metricsJsModule.recordKeychainAvailability;
     recordTokenStorageInitializationModule =
       metricsJsModule.recordTokenStorageInitialization;
+    recordInvalidChunkModule = metricsJsModule.recordInvalidChunk;
 
     const otelApiModule = await import('@opentelemetry/api');
 
@@ -1555,5 +1557,27 @@ describe('Telemetry Metrics', () => {
         });
       });
     });
+
+    describe('recordInvalidChunk', () => {
+      it('should not record metrics if not initialized', () => {
+        const config = makeFakeConfig({});
+        recordInvalidChunkModule(config);
+        expect(mockCounterAddFn).not.toHaveBeenCalled();
+      });
+
+      it('should record invalid chunk when initialized', () => {
+        const config = makeFakeConfig({});
+        initializeMetricsModule(config);
+        mockCounterAddFn.mockClear();
+
+        recordInvalidChunkModule(config);
+
+        expect(mockCounterAddFn).toHaveBeenCalledWith(1, {
+          'session.id': 'test-session-id',
+          'installation.id': 'test-installation-id',
+          'user.email': 'test@example.com',
+        });
+      });
+    });
   });
 });