fix(server-utils): Start Flue runs without a recorded admission in clean scopes

A submission admitted by another process, replayed by idempotency key or
evicted from the map has no record to restore, so its run kept the context
the claim loop inherited from an unrelated request, and lost its
`traceparent`. Run it in clean scopes with a new trace instead, through the
existing `withCleanScopes` helper, which also gives restored runs a clean
current scope.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: RulaKhaled

packages/server-utils/src/ai/flue/index.ts

@@ -2,13 +2,13 @@ import type { Scope, Span } from '@sentry/core';
 import {
   continueTrace,
   getActiveSpan,
+  getDefaultIsolationScope,
   getIsolationScope,
   GLOBAL_OBJ,
   LRUMap,
   startNewTrace,
   startSpan,
   withActiveSpan,
-  withIsolationScope,
 } from '@sentry/core';
 import {
   GEN_AI_AGENT_NAME,
@@ -19,6 +19,7 @@ import {
 import type { GenAiOptions } from '../core/utils';
 import { getGenAiSpanOp, resolveAIRecordingOptions } from '../core/utils';
 import { skipPiAiProviderIntegrations } from '../pi-ai/providers';
+import { withCleanScopes } from '../../utils/withCleanScopes';
 import { FLUE_INSTRUMENTATION_KEY, FLUE_OPERATION, FLUE_ORIGIN, MAX_TRACKED_FLUE_SPANS } from './constants';
 import type { SpanTracker } from './utils';
 import {
@@ -45,10 +46,15 @@ interface Admission {
  * (https://github.com/withastro/flue/issues/813).
  */
 function runInAdmissionContext<T>(admission: Admission | undefined, next: () => T): T {
-  if (!admission) {
+  if (isCloudflareWorkers()) {
     return next();
   }
-  return withIsolationScope(admission.isolationScope, () =>
+  if (!admission) {
+    // Admitted by another process, replayed by idempotency key, or evicted: there is nothing to
+    // restore, but the loop's context still belongs to an unrelated request.
+    return withCleanScopes(getDefaultIsolationScope().clone(), () => startNewTrace(next));
+  }
+  return withCleanScopes(admission.isolationScope, () =>
     admission.span ? withActiveSpan(admission.span, next) : startNewTrace(next),
   );
 }

packages/server-utils/test/ai/lib/tracing/flue.test.ts

@@ -303,17 +303,37 @@ describe('createFlueInstrumentation', () => {
       expect(findSpan('invoke_agent Hello')?.parent_span_id).toBe(alarmSpanId);
     });
 
-    it('forgets the admission once the submission settled', async () => {
+    // A submission admitted by another process, replayed by idempotency key, or already settled has
+    // no record here, but the loop still carries the context of whichever request started it.
+    it('drops the loop context when nothing was recorded for the submission', async () => {
       withActiveSpan(startInactiveSpan({ name: 'POST /agents/hello/b' }), admit);
       instrumentation.observe({ type: 'submission_settled', submissionId: 'sub_1' }, {});
 
-      let loopSpanId: string | undefined;
+      let loopTraceId: string | undefined;
       await startSpan({ name: 'POST /agents/hello/a' }, span => {
-        loopSpanId = span.spanContext().spanId;
+        loopTraceId = span.spanContext().traceId;
         return runSubmission();
       });
 
-      expect(findSpan('invoke_agent Hello')?.parent_span_id).toBe(loopSpanId);
+      const agent = findSpan('invoke_agent Hello');
+      expect(agent?.parent_span_id).toBeUndefined();
+      expect(agent?.trace_id).toMatch(/^[0-9a-f]{32}$/);
+      expect(agent?.trace_id).not.toBe(loopTraceId);
+    });
+
+    it('continues the replayed traceparent when nothing was recorded for the submission', async () => {
+      const traceId = 'cccccccccccccccccccccccccccccccc';
+      await startSpan({ name: 'POST /agents/hello/a' }, () =>
+        instrumentation.interceptor(SUBMISSION_OP, AGENT_CTX, () =>
+          instrumentation.interceptor(
+            AGENT_OP,
+            { ...AGENT_CTX, traceCarrier: { traceparent: `00-${traceId}-dddddddddddddddd-01` } },
+            async () => undefined,
+          ),
+        ),
+      );
+
+      expect(findSpan('invoke_agent Hello')?.trace_id).toBe(traceId);
     });
   });