From c0aa90bab853506e769608b4c6c367ea9ade6593 Mon Sep 17 00:00:00 2001
From: JPeer264 <jan.peer@sentry.io>
Date: Tue, 22 Sep 2026 16:14:43 +0200
Subject: [PATCH] fix(cloudflare): Bind pass-through Queue producer methods to
 the binding

The Queue producer proxy returned methods other than send and sendBatch
unbound, so calling a native method like metrics() ran it with the proxy
as `this` and workerd threw "Illegal invocation".

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 .../suites/queue/index.ts                        |  4 ++++
 .../suites/queue/test.ts                         | 16 ++++++++++++++++
 .../worker/instrumentQueueProducer.ts            |  4 +++-
 .../worker/instrumentQueueProducer.test.ts       | 15 +++++++++++++++
 4 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/dev-packages/cloudflare-integration-tests/suites/queue/index.ts b/dev-packages/cloudflare-integration-tests/suites/queue/index.ts
index 405b86695ed4..55968af1f0fa 100644
--- a/dev-packages/cloudflare-integration-tests/suites/queue/index.ts
+++ b/dev-packages/cloudflare-integration-tests/suites/queue/index.ts
@@ -35,6 +35,10 @@ export default Sentry.withSentry(
         return new Response('enqueued batch');
       }
 
+      if (url.pathname === '/metrics') {
+        return Response.json(await env.MY_QUEUE.metrics());
+      }
+
       return new Response('not found', { status: 404 });
     },
     async queue(batch: MessageBatch<{ trigger?: 'error'; payload?: string }>) {
diff --git a/dev-packages/cloudflare-integration-tests/suites/queue/test.ts b/dev-packages/cloudflare-integration-tests/suites/queue/test.ts
index f0886ba3f37c..6d116ef37bbe 100644
--- a/dev-packages/cloudflare-integration-tests/suites/queue/test.ts
+++ b/dev-packages/cloudflare-integration-tests/suites/queue/test.ts
@@ -126,3 +126,19 @@ it('emits a queue.publish span with batch attributes on env.MY_QUEUE.sendBatch',
   await runner.makeRequest('post', '/enqueue/batch');
   await runner.completed();
 });
+
+it('calls non-instrumented Queue methods like metrics() on the underlying binding', async ({ signal }) => {
+  const runner = createRunner(__dirname)
+    .expect((envelope: Envelope) => {
+      expect(envelopeItemType(envelope)).toBe('transaction');
+      expect(envelopeItem(envelope)).toMatchObject({
+        transaction: 'GET /metrics',
+        contexts: { trace: { status: 'ok' } },
+      });
+    })
+    .start(signal);
+
+  const metrics = await runner.makeRequest('get', '/metrics');
+  expect(metrics).toMatchObject({ backlogCount: expect.any(Number), backlogBytes: expect.any(Number) });
+  await runner.completed();
+});
diff --git a/packages/cloudflare/src/instrumentations/worker/instrumentQueueProducer.ts b/packages/cloudflare/src/instrumentations/worker/instrumentQueueProducer.ts
index 293b027d5441..d1b3de4ba107 100644
--- a/packages/cloudflare/src/instrumentations/worker/instrumentQueueProducer.ts
+++ b/packages/cloudflare/src/instrumentations/worker/instrumentQueueProducer.ts
@@ -99,7 +99,9 @@ export function instrumentQueueProducer<T extends Queue>(queue: T, bindingName:
         };
       }
 
-      return Reflect.get(target, prop, receiver);
+      const value = Reflect.get(target, prop) as unknown;
+
+      return typeof value === 'function' ? value.bind(target) : value;
     },
   });
 }
diff --git a/packages/cloudflare/test/instrumentations/worker/instrumentQueueProducer.test.ts b/packages/cloudflare/test/instrumentations/worker/instrumentQueueProducer.test.ts
index 5b291bea7e3e..f176d92e53db 100644
--- a/packages/cloudflare/test/instrumentations/worker/instrumentQueueProducer.test.ts
+++ b/packages/cloudflare/test/instrumentations/worker/instrumentQueueProducer.test.ts
@@ -178,4 +178,19 @@ describe('instrumentQueueProducer', () => {
     const wrapped = instrumentQueueProducer(queue, 'MY_QUEUE') as Queue & { customMethod: () => string };
     expect(wrapped.customMethod()).toBe('hi');
   });
+
+  test('calls pass-through methods with the underlying queue as `this`', async () => {
+    const metrics = { backlogCount: 3, backlogBytes: 42 };
+    const queue = Object.assign(createMockQueue(), {
+      metrics(this: unknown) {
+        if (this !== queue) {
+          throw new TypeError('Illegal invocation: function called with incorrect `this` reference.');
+        }
+        return Promise.resolve(metrics);
+      },
+    }) as unknown as Queue & { metrics: () => Promise<typeof metrics> };
+    const wrapped = instrumentQueueProducer(queue, 'MY_QUEUE') as typeof queue;
+
+    await expect(wrapped.metrics()).resolves.toEqual(metrics);
+  });
 });