6 files changed, 592 insertions, 0 deletions
diff --git a/packages/core/src/telemetry/constants.ts b/packages/core/src/telemetry/constants.ts
new file mode 100644
index 00000000..67d5b38b
--- /dev/null
+++ b/packages/core/src/telemetry/constants.ts
@@ -0,0 +1,24 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { randomUUID } from 'crypto';
+
+export const SERVICE_NAME = 'gemini-code';
+export const sessionId = randomUUID();
+
+export const EVENT_USER_PROMPT = 'gemini_code.user_prompt';
+export const EVENT_TOOL_CALL = 'gemini_code.tool_call';
+export const EVENT_API_REQUEST = 'gemini_code.api_request';
+export const EVENT_API_ERROR = 'gemini_code.api_error';
+export const EVENT_API_RESPONSE = 'gemini_code.api_response';
+export const EVENT_CLI_CONFIG = 'gemini_code.config';
+
+export const METRIC_TOOL_CALL_COUNT = 'gemini_code.tool.call.count';
+export const METRIC_TOOL_CALL_LATENCY = 'gemini_code.tool.call.latency';
+export const METRIC_API_REQUEST_COUNT = 'gemini_code.api.request.count';
+export const METRIC_API_REQUEST_LATENCY = 'gemini_code.api.request.latency';
+export const METRIC_TOKEN_INPUT_COUNT = 'gemini_code.token.input.count';
+export const METRIC_SESSION_COUNT = 'gemini_code.session.count';
diff --git a/packages/core/src/telemetry/index.ts b/packages/core/src/telemetry/index.ts
new file mode 100644
index 00000000..7b2ab0e7
--- /dev/null
+++ b/packages/core/src/telemetry/index.ts
@@ -0,0 +1,31 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+export {
+  initializeTelemetry,
+  shutdownTelemetry,
+  isTelemetrySdkInitialized,
+} from './sdk.js';
+export {
+  logCliConfiguration,
+  logUserPrompt,
+  logToolCall,
+  logApiRequest,
+  logApiError,
+  logApiResponse,
+} from './loggers.js';
+export {
+  UserPromptEvent,
+  ToolCallEvent,
+  ApiRequestEvent,
+  ApiErrorEvent,
+  ApiResponseEvent,
+  CliConfigEvent,
+  TelemetryEvent,
+} from './types.js';
+export { SpanStatusCode, ValueType } from '@opentelemetry/api';
+export { SemanticAttributes } from '@opentelemetry/semantic-conventions';
+export { sessionId } from './constants.js';
diff --git a/packages/core/src/telemetry/loggers.ts b/packages/core/src/telemetry/loggers.ts
new file mode 100644
index 00000000..ccab12ff
--- /dev/null
+++ b/packages/core/src/telemetry/loggers.ts
@@ -0,0 +1,191 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { logs, LogRecord, LogAttributes } from '@opentelemetry/api-logs';
+import { SemanticAttributes } from '@opentelemetry/semantic-conventions';
+import { Config } from '../config/config.js';
+import {
+  EVENT_API_ERROR,
+  EVENT_API_REQUEST,
+  EVENT_API_RESPONSE,
+  EVENT_CLI_CONFIG,
+  EVENT_TOOL_CALL,
+  EVENT_USER_PROMPT,
+  SERVICE_NAME,
+} from './constants.js';
+import {
+  ApiErrorEvent,
+  ApiRequestEvent,
+  ApiResponseEvent,
+  ToolCallEvent,
+  UserPromptEvent,
+} from './types.js';
+import {
+  recordApiErrorMetrics,
+  recordApiRequestMetrics,
+  recordApiResponseMetrics,
+  recordToolCallMetrics,
+} from './metrics.js';
+import { isTelemetrySdkInitialized } from './sdk.js';
+
+const shouldLogUserPrompts = (config: Config): boolean =>
+  config.getTelemetryLogUserPromptsEnabled() ?? false;
+
+export function logCliConfiguration(config: Config): void {
+  if (!isTelemetrySdkInitialized()) return;
+
+  const attributes: LogAttributes = {
+    'event.name': EVENT_CLI_CONFIG,
+    'event.timestamp': new Date().toISOString(),
+    model: config.getModel(),
+    sandbox_enabled:
+      typeof config.getSandbox() === 'string' ? true : config.getSandbox(),
+    core_tools_enabled: (config.getCoreTools() ?? []).join(','),
+    approval_mode: config.getApprovalMode(),
+    vertex_ai_enabled: config.getVertexAI() ?? false,
+    log_user_prompts_enabled: config.getTelemetryLogUserPromptsEnabled(),
+    file_filtering_respect_git_ignore:
+      config.getFileFilteringRespectGitIgnore(),
+    file_filtering_allow_build_artifacts:
+      config.getFileFilteringAllowBuildArtifacts(),
+  };
+  const logger = logs.getLogger(SERVICE_NAME);
+  const logRecord: LogRecord = {
+    body: 'CLI configuration loaded.',
+    attributes,
+  };
+  logger.emit(logRecord);
+}
+
+export function logUserPrompt(
+  config: Config,
+  event: Omit<UserPromptEvent, 'event.name' | 'event.timestamp' | 'prompt'> & {
+    prompt: string;
+  },
+): void {
+  if (!isTelemetrySdkInitialized()) return;
+  const { prompt, ...restOfEventArgs } = event;
+  const attributes: LogAttributes = {
+    ...restOfEventArgs,
+    'event.name': EVENT_USER_PROMPT,
+    'event.timestamp': new Date().toISOString(),
+  };
+  if (shouldLogUserPrompts(config)) {
+    attributes.prompt = prompt;
+  }
+  const logger = logs.getLogger(SERVICE_NAME);
+  const logRecord: LogRecord = {
+    body: `User prompt. Length: ${event.prompt_char_count}`,
+    attributes,
+  };
+  logger.emit(logRecord);
+}
+
+export function logToolCall(
+  event: Omit<ToolCallEvent, 'event.name' | 'event.timestamp'>,
+): void {
+  if (!isTelemetrySdkInitialized()) return;
+  const attributes: LogAttributes = {
+    ...event,
+    'event.name': EVENT_TOOL_CALL,
+    'event.timestamp': new Date().toISOString(),
+    function_args: JSON.stringify(event.function_args),
+  };
+  if (event.error) {
+    attributes['error.message'] = event.error;
+    if (event.error_type) {
+      attributes['error.type'] = event.error_type;
+    }
+  }
+  const logger = logs.getLogger(SERVICE_NAME);
+  const logRecord: LogRecord = {
+    body: `Tool call: ${event.function_name}. Success: ${event.success}. Duration: ${event.duration_ms}ms.`,
+    attributes,
+  };
+  logger.emit(logRecord);
+  recordToolCallMetrics(event.function_name, event.duration_ms, event.success);
+}
+
+export function logApiRequest(
+  event: Omit<ApiRequestEvent, 'event.name' | 'event.timestamp'>,
+): void {
+  if (!isTelemetrySdkInitialized()) return;
+  const attributes: LogAttributes = {
+    ...event,
+    'event.name': EVENT_API_REQUEST,
+    'event.timestamp': new Date().toISOString(),
+  };
+  const logger = logs.getLogger(SERVICE_NAME);
+  const logRecord: LogRecord = {
+    body: `API request to ${event.model}. Tokens: ${event.prompt_token_count}.`,
+    attributes,
+  };
+  logger.emit(logRecord);
+  recordApiRequestMetrics(event.model, event.prompt_token_count);
+}
+
+export function logApiError(
+  event: Omit<ApiErrorEvent, 'event.name' | 'event.timestamp'>,
+): void {
+  if (!isTelemetrySdkInitialized()) return;
+  const attributes: LogAttributes = {
+    ...event,
+    'event.name': EVENT_API_ERROR,
+    'event.timestamp': new Date().toISOString(),
+    ['error.message']: event.error,
+  };
+
+  if (event.error_type) {
+    attributes['error.type'] = event.error_type;
+  }
+  if (typeof event.status_code === 'number') {
+    attributes[SemanticAttributes.HTTP_STATUS_CODE] = event.status_code;
+  }
+
+  const logger = logs.getLogger(SERVICE_NAME);
+  const logRecord: LogRecord = {
+    body: `API error for ${event.model}. Error: ${event.error}. Duration: ${event.duration_ms}ms.`,
+    attributes,
+  };
+  logger.emit(logRecord);
+  recordApiErrorMetrics(
+    event.model,
+    event.duration_ms,
+    event.status_code,
+    event.error_type,
+  );
+}
+
+export function logApiResponse(
+  event: Omit<ApiResponseEvent, 'event.name' | 'event.timestamp'>,
+): void {
+  if (!isTelemetrySdkInitialized()) return;
+  const attributes: LogAttributes = {
+    ...event,
+    'event.name': EVENT_API_RESPONSE,
+    'event.timestamp': new Date().toISOString(),
+  };
+  if (event.error) {
+    attributes['error.message'] = event.error;
+  } else if (event.status_code) {
+    if (typeof event.status_code === 'number') {
+      attributes[SemanticAttributes.HTTP_STATUS_CODE] = event.status_code;
+    }
+  }
+
+  const logger = logs.getLogger(SERVICE_NAME);
+  const logRecord: LogRecord = {
+    body: `API response from ${event.model}. Status: ${event.status_code || 'N/A'}. Duration: ${event.duration_ms}ms.`,
+    attributes,
+  };
+  logger.emit(logRecord);
+  recordApiResponseMetrics(
+    event.model,
+    event.duration_ms,
+    event.status_code,
+    event.error,
+  );
+}
diff --git a/packages/core/src/telemetry/metrics.ts b/packages/core/src/telemetry/metrics.ts
new file mode 100644
index 00000000..2e6bd909
--- /dev/null
+++ b/packages/core/src/telemetry/metrics.ts
@@ -0,0 +1,145 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {
+  metrics,
+  Attributes,
+  ValueType,
+  Meter,
+  Counter,
+  Histogram,
+} from '@opentelemetry/api';
+import {
+  SERVICE_NAME,
+  METRIC_TOOL_CALL_COUNT,
+  METRIC_TOOL_CALL_LATENCY,
+  METRIC_API_REQUEST_COUNT,
+  METRIC_API_REQUEST_LATENCY,
+  METRIC_TOKEN_INPUT_COUNT,
+  METRIC_SESSION_COUNT,
+} from './constants.js';
+
+let cliMeter: Meter | undefined;
+let toolCallCounter: Counter | undefined;
+let toolCallLatencyHistogram: Histogram | undefined;
+let apiRequestCounter: Counter | undefined;
+let apiRequestLatencyHistogram: Histogram | undefined;
+let tokenInputCounter: Counter | undefined;
+let isMetricsInitialized = false;
+
+export function getMeter(): Meter | undefined {
+  if (!cliMeter) {
+    cliMeter = metrics.getMeter(SERVICE_NAME);
+  }
+  return cliMeter;
+}
+
+export function initializeMetrics(): void {
+  if (isMetricsInitialized) return;
+
+  const meter = getMeter();
+  if (!meter) return;
+
+  toolCallCounter = meter.createCounter(METRIC_TOOL_CALL_COUNT, {
+    description: 'Counts tool calls, tagged by function name and success.',
+    valueType: ValueType.INT,
+  });
+  toolCallLatencyHistogram = meter.createHistogram(METRIC_TOOL_CALL_LATENCY, {
+    description: 'Latency of tool calls in milliseconds.',
+    unit: 'ms',
+    valueType: ValueType.INT,
+  });
+  apiRequestCounter = meter.createCounter(METRIC_API_REQUEST_COUNT, {
+    description: 'Counts API requests, tagged by model and status.',
+    valueType: ValueType.INT,
+  });
+  apiRequestLatencyHistogram = meter.createHistogram(
+    METRIC_API_REQUEST_LATENCY,
+    {
+      description: 'Latency of API requests in milliseconds.',
+      unit: 'ms',
+      valueType: ValueType.INT,
+    },
+  );
+  tokenInputCounter = meter.createCounter(METRIC_TOKEN_INPUT_COUNT, {
+    description: 'Counts the total number of input tokens sent to the API.',
+    valueType: ValueType.INT,
+  });
+
+  const sessionCounter = meter.createCounter(METRIC_SESSION_COUNT, {
+    description: 'Count of CLI sessions started.',
+    valueType: ValueType.INT,
+  });
+  sessionCounter.add(1);
+  isMetricsInitialized = true;
+}
+
+export function recordToolCallMetrics(
+  functionName: string,
+  durationMs: number,
+  success: boolean,
+): void {
+  if (!toolCallCounter || !toolCallLatencyHistogram || !isMetricsInitialized)
+    return;
+
+  const metricAttributes: Attributes = {
+    function_name: functionName,
+    success,
+  };
+  toolCallCounter.add(1, metricAttributes);
+  toolCallLatencyHistogram.record(durationMs, {
+    function_name: functionName,
+  });
+}
+
+export function recordApiRequestMetrics(
+  model: string,
+  inputTokenCount: number,
+): void {
+  if (!tokenInputCounter || !isMetricsInitialized) return;
+  tokenInputCounter.add(inputTokenCount, { model });
+}
+
+export function recordApiResponseMetrics(
+  model: string,
+  durationMs: number,
+  statusCode?: number | string,
+  error?: string,
+): void {
+  if (
+    !apiRequestCounter ||
+    !apiRequestLatencyHistogram ||
+    !isMetricsInitialized
+  )
+    return;
+  const metricAttributes: Attributes = {
+    model,
+    status_code: statusCode ?? (error ? 'error' : 'ok'),
+  };
+  apiRequestCounter.add(1, metricAttributes);
+  apiRequestLatencyHistogram.record(durationMs, { model });
+}
+
+export function recordApiErrorMetrics(
+  model: string,
+  durationMs: number,
+  statusCode?: number | string,
+  errorType?: string,
+): void {
+  if (
+    !apiRequestCounter ||
+    !apiRequestLatencyHistogram ||
+    !isMetricsInitialized
+  )
+    return;
+  const metricAttributes: Attributes = {
+    model,
+    status_code: statusCode ?? 'error',
+    error_type: errorType ?? 'unknown',
+  };
+  apiRequestCounter.add(1, metricAttributes);
+  apiRequestLatencyHistogram.record(durationMs, { model });
+}
diff --git a/packages/core/src/telemetry/sdk.ts b/packages/core/src/telemetry/sdk.ts
new file mode 100644
index 00000000..b55cb149
--- /dev/null
+++ b/packages/core/src/telemetry/sdk.ts
@@ -0,0 +1,128 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { DiagConsoleLogger, DiagLogLevel, diag } from '@opentelemetry/api';
+import { OTLPTraceExporter } from '@opentelemetry/exporter-trace-otlp-grpc';
+import { OTLPLogExporter } from '@opentelemetry/exporter-logs-otlp-grpc';
+import { OTLPMetricExporter } from '@opentelemetry/exporter-metrics-otlp-grpc';
+import { NodeSDK } from '@opentelemetry/sdk-node';
+import { SemanticResourceAttributes } from '@opentelemetry/semantic-conventions';
+import { Resource } from '@opentelemetry/resources';
+import {
+  BatchSpanProcessor,
+  ConsoleSpanExporter,
+} from '@opentelemetry/sdk-trace-node';
+import {
+  BatchLogRecordProcessor,
+  ConsoleLogRecordExporter,
+} from '@opentelemetry/sdk-logs';
+import {
+  ConsoleMetricExporter,
+  PeriodicExportingMetricReader,
+} from '@opentelemetry/sdk-metrics';
+import { HttpInstrumentation } from '@opentelemetry/instrumentation-http';
+import { Config } from '../config/config.js';
+import { SERVICE_NAME, sessionId } from './constants.js';
+import { initializeMetrics } from './metrics.js';
+import { logCliConfiguration } from './loggers.js';
+
+// For troubleshooting, set the log level to DiagLogLevel.DEBUG
+diag.setLogger(new DiagConsoleLogger(), DiagLogLevel.INFO);
+
+let sdk: NodeSDK | undefined;
+let telemetryInitialized = false;
+
+export function isTelemetrySdkInitialized(): boolean {
+  return telemetryInitialized;
+}
+
+function parseGrpcEndpoint(
+  otlpEndpointSetting: string | undefined,
+): string | undefined {
+  if (!otlpEndpointSetting) {
+    return undefined;
+  }
+  // Trim leading/trailing quotes that might come from env variables
+  const trimmedEndpoint = otlpEndpointSetting.replace(/^["']|["']$/g, '');
+
+  try {
+    const url = new URL(trimmedEndpoint);
+    // OTLP gRPC exporters expect an endpoint in the format scheme://host:port
+    // The `origin` property provides this, stripping any path, query, or hash.
+    return url.origin;
+  } catch (error) {
+    diag.error('Invalid OTLP endpoint URL provided:', trimmedEndpoint, error);
+    return undefined;
+  }
+}
+
+export function initializeTelemetry(config: Config): void {
+  if (telemetryInitialized || !config.getTelemetryEnabled()) {
+    return;
+  }
+
+  const geminiCliVersion = config.getUserAgent() || 'unknown';
+  const resource = new Resource({
+    [SemanticResourceAttributes.SERVICE_NAME]: SERVICE_NAME,
+    [SemanticResourceAttributes.SERVICE_VERSION]: geminiCliVersion,
+    'session.id': sessionId,
+  });
+
+  const otlpEndpoint = config.getTelemetryOtlpEndpoint();
+  const grpcParsedEndpoint = parseGrpcEndpoint(otlpEndpoint);
+  const useOtlp = !!grpcParsedEndpoint;
+
+  const spanExporter = useOtlp
+    ? new OTLPTraceExporter({ url: grpcParsedEndpoint })
+    : new ConsoleSpanExporter();
+  const logExporter = useOtlp
+    ? new OTLPLogExporter({ url: grpcParsedEndpoint })
+    : new ConsoleLogRecordExporter();
+  const metricReader = useOtlp
+    ? new PeriodicExportingMetricReader({
+        exporter: new OTLPMetricExporter({ url: grpcParsedEndpoint }),
+        exportIntervalMillis: 10000,
+      })
+    : new PeriodicExportingMetricReader({
+        exporter: new ConsoleMetricExporter(),
+        exportIntervalMillis: 10000,
+      });
+
+  sdk = new NodeSDK({
+    resource,
+    spanProcessors: [new BatchSpanProcessor(spanExporter)],
+    logRecordProcessor: new BatchLogRecordProcessor(logExporter),
+    metricReader,
+    instrumentations: [new HttpInstrumentation()],
+  });
+
+  try {
+    sdk.start();
+    console.log('OpenTelemetry SDK started successfully.');
+    telemetryInitialized = true;
+    initializeMetrics();
+    logCliConfiguration(config);
+  } catch (error) {
+    console.error('Error starting OpenTelemetry SDK:', error);
+  }
+
+  process.on('SIGTERM', shutdownTelemetry);
+  process.on('SIGINT', shutdownTelemetry);
+}
+
+export async function shutdownTelemetry(): Promise<void> {
+  if (!telemetryInitialized || !sdk) {
+    return;
+  }
+  try {
+    await sdk.shutdown();
+    console.log('OpenTelemetry SDK shut down successfully.');
+  } catch (error) {
+    console.error('Error shutting down SDK:', error);
+  } finally {
+    telemetryInitialized = false;
+  }
+}
diff --git a/packages/core/src/telemetry/types.ts b/packages/core/src/telemetry/types.ts
new file mode 100644
index 00000000..ea65d6de
--- /dev/null
+++ b/packages/core/src/telemetry/types.ts
@@ -0,0 +1,73 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+export interface UserPromptEvent {
+  'event.name': 'user_prompt';
+  'event.timestamp': string; // ISO 8601
+  prompt_char_count: number;
+  prompt?: string;
+}
+
+export interface ToolCallEvent {
+  'event.name': 'tool_call';
+  'event.timestamp': string; // ISO 8601
+  function_name: string;
+  function_args: Record<string, unknown>;
+  duration_ms: number;
+  success: boolean;
+  error?: string;
+  error_type?: string;
+}
+
+export interface ApiRequestEvent {
+  'event.name': 'api_request';
+  'event.timestamp': string; // ISO 8601
+  model: string;
+  duration_ms: number;
+  prompt_token_count: number;
+}
+
+export interface ApiErrorEvent {
+  'event.name': 'api_error';
+  'event.timestamp': string; // ISO 8601
+  model: string;
+  error: string;
+  error_type?: string;
+  status_code?: number | string;
+  duration_ms: number;
+  attempt: number;
+}
+
+export interface ApiResponseEvent {
+  'event.name': 'api_response';
+  'event.timestamp': string; // ISO 8601
+  model: string;
+  status_code?: number | string;
+  duration_ms: number;
+  error?: string;
+  attempt: number;
+}
+
+export interface CliConfigEvent {
+  'event.name': 'cli_config';
+  'event.timestamp': string; // ISO 8601
+  model: string;
+  sandbox_enabled: boolean;
+  core_tools_enabled: string;
+  approval_mode: string;
+  vertex_ai_enabled: boolean;
+  log_user_prompts_enabled: boolean;
+  file_filtering_respect_git_ignore: boolean;
+  file_filtering_allow_build_artifacts: boolean;
+}
+
+export type TelemetryEvent =
+  | UserPromptEvent
+  | ToolCallEvent
+  | ApiRequestEvent
+  | ApiErrorEvent
+  | ApiResponseEvent
+  | CliConfigEvent;