feat(telemetry) - Add metric for slow rendering (#12391)

Co-authored-by: gemini-cli-robot <gemini-cli-robot@google.com>

packages/core/src/telemetry/index.ts

@@ -126,6 +126,7 @@ export {
   recordBaselineComparison,
   isPerformanceMonitoringActive,
   recordFlickerFrame,
+  recordSlowRender,
   // Performance monitoring types
   PerformanceMetricType,
   MemoryMetricType,

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

@@ -95,6 +95,7 @@ describe('Telemetry Metrics', () => {
   let recordExitFailModule: typeof import('./metrics.js').recordExitFail;
   let recordAgentRunMetricsModule: typeof import('./metrics.js').recordAgentRunMetrics;
   let recordLinesChangedModule: typeof import('./metrics.js').recordLinesChanged;
+  let recordSlowRenderModule: typeof import('./metrics.js').recordSlowRender;
 
   beforeEach(async () => {
     vi.resetModules();
@@ -138,6 +139,7 @@ describe('Telemetry Metrics', () => {
     recordExitFailModule = metricsJsModule.recordExitFail;
     recordAgentRunMetricsModule = metricsJsModule.recordAgentRunMetrics;
     recordLinesChangedModule = metricsJsModule.recordLinesChanged;
+    recordSlowRenderModule = metricsJsModule.recordSlowRender;
 
     const otelApiModule = await import('@opentelemetry/api');
 
@@ -196,6 +198,26 @@ describe('Telemetry Metrics', () => {
     });
   });
 
+  describe('recordSlowRender', () => {
+    it('does not record metrics if not initialized', () => {
+      const config = makeFakeConfig({});
+      recordSlowRenderModule(config, 123);
+      expect(mockHistogramRecordFn).not.toHaveBeenCalled();
+    });
+
+    it('records a slow render event when initialized', () => {
+      const config = makeFakeConfig({});
+      initializeMetricsModule(config);
+      recordSlowRenderModule(config, 123);
+
+      expect(mockHistogramRecordFn).toHaveBeenCalledWith(123, {
+        'session.id': 'test-session-id',
+        'installation.id': 'test-installation-id',
+        'user.email': 'test@example.com',
+      });
+    });
+  });
+
   describe('initializeMetrics', () => {
     const mockConfig = {
       getSessionId: () => 'test-session-id',

packages/core/src/telemetry/metrics.ts

@@ -57,6 +57,7 @@ const REGRESSION_PERCENTAGE_CHANGE =
   'gemini_cli.performance.regression.percentage_change';
 const BASELINE_COMPARISON = 'gemini_cli.performance.baseline.comparison';
 const FLICKER_FRAME_COUNT = 'gemini_cli.ui.flicker.count';
+const SLOW_RENDER_LATENCY = 'gemini_cli.ui.slow_render.latency';
 const EXIT_FAIL_COUNT = 'gemini_cli.exit.fail.count';
 
 const baseMetricDefinition = {
@@ -227,6 +228,13 @@ const HISTOGRAM_DEFINITIONS = {
       agent_name: string;
     },
   },
+  [SLOW_RENDER_LATENCY]: {
+    description: 'Counts UI frames that take too long to render.',
+    unit: 'ms',
+    valueType: ValueType.INT,
+    assign: (h: Histogram) => (slowRenderHistogram = h),
+    attributes: {} as Record<string, never>,
+  },
   [AGENT_TURNS]: {
     description: 'Number of turns taken by agents.',
     unit: 'turns',
@@ -472,6 +480,7 @@ let agentDurationHistogram: Histogram | undefined;
 let agentTurnsHistogram: Histogram | undefined;
 let flickerFrameCounter: Counter | undefined;
 let exitFailCounter: Counter | undefined;
+let slowRenderHistogram: Histogram | undefined;
 
 // OpenTelemetry GenAI Semantic Convention Metrics
 let genAiClientTokenUsageHistogram: Histogram | undefined;
@@ -660,6 +669,16 @@ export function recordExitFail(config: Config): void {
   exitFailCounter.add(1, baseMetricDefinition.getCommonAttributes(config));
 }
 
+/**
+ * Records a metric for when a UI frame is slow in rendering
+ */
+export function recordSlowRender(config: Config, renderLatency: number): void {
+  if (!slowRenderHistogram || !isMetricsInitialized) return;
+  slowRenderHistogram.record(renderLatency, {
+    ...baseMetricDefinition.getCommonAttributes(config),
+  });
+}
+
 /**
  * Records a metric for when an invalid chunk is received from a stream.
  */