1 files changed, 145 insertions, 0 deletions
diff --git a/packages/core/src/telemetry/metrics.ts b/packages/core/src/telemetry/metrics.ts
new file mode 100644
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+++ b/packages/core/src/telemetry/metrics.ts
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+/**
+ * @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 });
+}