fix(voice): propagate caller's OTel context through AgentSession

Honour otelContext.active() when starting the agent_session span and
when building rootSpanContext, so spans the caller created before
session.start() become parents of LiveKit spans. Stop calling
tracerProvider.register() in setupCloudTracer to avoid replacing the
global AsyncLocalStorageContextManager.

Fixes #924

Author: mrniket

agents/src/telemetry/traces.test.ts

@@ -0,0 +1,52 @@
+// SPDX-FileCopyrightText: 2026 LiveKit, Inc.
+//
+// SPDX-License-Identifier: Apache-2.0
+import { context as otelContext, trace } from '@opentelemetry/api';
+import { InMemorySpanExporter, SimpleSpanProcessor } from '@opentelemetry/sdk-trace-base';
+import { NodeTracerProvider } from '@opentelemetry/sdk-trace-node';
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { setTracerProvider, tracer } from './traces.js';
+
+describe('DynamicTracer', () => {
+  let exporter: InMemorySpanExporter;
+  let provider: NodeTracerProvider;
+
+  beforeEach(() => {
+    exporter = new InMemorySpanExporter();
+    provider = new NodeTracerProvider({
+      spanProcessors: [new SimpleSpanProcessor(exporter)],
+    });
+    provider.register();
+    setTracerProvider(provider);
+  });
+
+  afterEach(async () => {
+    await provider.shutdown();
+    otelContext.disable();
+    trace.disable();
+  });
+
+  it('inherits the active OTel context as parent when no explicit context is passed', async () => {
+    const outerTracer = provider.getTracer('test');
+
+    await outerTracer.startActiveSpan('outer', async (outer) => {
+      const child = tracer.startSpan({ name: 'child' });
+      child.end();
+      outer.end();
+    });
+
+    const spans = exporter.getFinishedSpans();
+    const outerSpan = spans.find((s) => s.name === 'outer');
+    const childSpan = spans.find((s) => s.name === 'child');
+
+    expect(outerSpan).toBeDefined();
+    expect(childSpan).toBeDefined();
+
+    // parentSpanId in OTel SDK v1; parentSpanContext.spanId in v2.
+    const parentId =
+      (childSpan as { parentSpanId?: string }).parentSpanId ??
+      (childSpan as { parentSpanContext?: { spanId: string } }).parentSpanContext?.spanId;
+
+    expect(parentId).toBe(outerSpan!.spanContext().spanId);
+  });
+});

agents/src/telemetry/traces.ts

@@ -258,8 +258,7 @@ export async function setupCloudTracer(options: {
       resource,
       spanProcessors: [new MetadataSpanProcessor(metadata), new BatchSpanProcessor(spanExporter)],
     });
-    tracerProvider.register();
-
+    // Don't call tracerProvider.register() — it would replace the global context manager.
     setTracerProvider(tracerProvider);
 
     // Initialize standalone Pino cloud exporter (no OTEL SDK dependency)

agents/src/voice/agent_session.ts

@@ -5,7 +5,7 @@ import { Mutex } from '@livekit/mutex';
 import type { AudioFrame, Room } from '@livekit/rtc-node';
 import type { TypedEventEmitter as TypedEmitter } from '@livekit/typed-emitter';
 import type { Context, Span } from '@opentelemetry/api';
-import { ROOT_CONTEXT, context as otelContext, trace } from '@opentelemetry/api';
+import { context as otelContext, trace } from '@opentelemetry/api';
 import { EventEmitter } from 'node:events';
 import type { ReadableStream } from 'node:stream/web';
 import type { z } from 'zod';
@@ -537,10 +537,9 @@ export class AgentSession<
 
     this.sessionSpan = tracer.startSpan({
       name: 'agent_session',
-      context: ROOT_CONTEXT,
     });
 
-    this.rootSpanContext = trace.setSpan(ROOT_CONTEXT, this.sessionSpan);
+    this.rootSpanContext = trace.setSpan(otelContext.active(), this.sessionSpan);
 
     await this._startImpl({
       agent,