feat(routing): A/B Test Numerical Complexity Scoring for Gemini 3 (#16041)

Co-authored-by: N. Taylor Mullen <ntaylormullen@google.com>

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

@@ -478,6 +478,8 @@ describe('Telemetry Metrics', () => {
         'user.email': 'test@example.com',
         'routing.decision_model': 'gemini-pro',
         'routing.decision_source': 'default',
+        'routing.failed': false,
+        'routing.reasoning': 'test-reason',
       });
       // The session counter is called once on init
       expect(mockCounterAddFn).toHaveBeenCalledTimes(1);
@@ -501,6 +503,8 @@ describe('Telemetry Metrics', () => {
         'user.email': 'test@example.com',
         'routing.decision_model': 'gemini-pro',
         'routing.decision_source': 'classifier',
+        'routing.failed': true,
+        'routing.reasoning': 'test-reason',
       });
 
       expect(mockCounterAddFn).toHaveBeenCalledTimes(2);
@@ -508,7 +512,10 @@ describe('Telemetry Metrics', () => {
         'session.id': 'test-session-id',
         'installation.id': 'test-installation-id',
         'user.email': 'test@example.com',
+        'routing.decision_model': 'gemini-pro',
         'routing.decision_source': 'classifier',
+        'routing.failed': true,
+        'routing.reasoning': 'test-reason',
         'routing.error_message': 'test-error',
       });
     });

packages/core/src/telemetry/metrics.ts

@@ -779,16 +779,29 @@ export function recordModelRoutingMetrics(
   )
     return;
 
-  modelRoutingLatencyHistogram.record(event.routing_latency_ms, {
+  const attributes: Attributes = {
     ...baseMetricDefinition.getCommonAttributes(config),
     'routing.decision_model': event.decision_model,
     'routing.decision_source': event.decision_source,
-  });
+    'routing.failed': event.failed,
+  };
+
+  if (event.reasoning) {
+    attributes['routing.reasoning'] = event.reasoning;
+  }
+  if (event.enable_numerical_routing !== undefined) {
+    attributes['routing.enable_numerical_routing'] =
+      event.enable_numerical_routing;
+  }
+  if (event.classifier_threshold) {
+    attributes['routing.classifier_threshold'] = event.classifier_threshold;
+  }
+
+  modelRoutingLatencyHistogram.record(event.routing_latency_ms, attributes);
 
   if (event.failed) {
     modelRoutingFailureCounter.add(1, {
-      ...baseMetricDefinition.getCommonAttributes(config),
-      'routing.decision_source': event.decision_source,
+      ...attributes,
       'routing.error_message': event.error_message,
     });
   }

packages/core/src/telemetry/types.ts

@@ -1193,6 +1193,8 @@ export class ModelRoutingEvent implements BaseTelemetryEvent {
   reasoning?: string;
   failed: boolean;
   error_message?: string;
+  enable_numerical_routing?: boolean;
+  classifier_threshold?: string;
 
   constructor(
     decision_model: string,
@@ -1201,6 +1203,8 @@ export class ModelRoutingEvent implements BaseTelemetryEvent {
     reasoning: string | undefined,
     failed: boolean,
     error_message: string | undefined,
+    enable_numerical_routing?: boolean,
+    classifier_threshold?: string,
   ) {
     this['event.name'] = 'model_routing';
     this['event.timestamp'] = new Date().toISOString();
@@ -1210,20 +1214,38 @@ export class ModelRoutingEvent implements BaseTelemetryEvent {
     this.reasoning = reasoning;
     this.failed = failed;
     this.error_message = error_message;
+    this.enable_numerical_routing = enable_numerical_routing;
+    this.classifier_threshold = classifier_threshold;
   }
 
   toOpenTelemetryAttributes(config: Config): LogAttributes {
-    return {
+    const attributes: LogAttributes = {
       ...getCommonAttributes(config),
       'event.name': EVENT_MODEL_ROUTING,
       'event.timestamp': this['event.timestamp'],
       decision_model: this.decision_model,
       decision_source: this.decision_source,
       routing_latency_ms: this.routing_latency_ms,
-      reasoning: this.reasoning,
       failed: this.failed,
-      error_message: this.error_message,
     };
+
+    if (this.reasoning) {
+      attributes['reasoning'] = this.reasoning;
+    }
+
+    if (this.error_message) {
+      attributes['error_message'] = this.error_message;
+    }
+
+    if (this.enable_numerical_routing !== undefined) {
+      attributes['enable_numerical_routing'] = this.enable_numerical_routing;
+    }
+
+    if (this.classifier_threshold) {
+      attributes['classifier_threshold'] = this.classifier_threshold;
+    }
+
+    return attributes;
   }
 
   toLogBody(): string {