WIP fix(cloudflare): Keep http root span alive until streaming responses are consumed

packages/cloudflare/src/request.ts

@@ -8,13 +8,14 @@ import {
   parseStringToURLObject,
   SEMANTIC_ATTRIBUTE_SENTRY_OP,
   setHttpStatus,
-  startSpan,
+  startSpanManual,
   winterCGHeadersToDict,
   withIsolationScope,
 } from '@sentry/core';
 import type { CloudflareOptions } from './client';
 import { addCloudResourceContext, addCultureContext, addRequest } from './scope-utils';
 import { init } from './sdk';
+import { classifyResponseStreaming } from './utils/streaming';
 
 interface RequestHandlerWrapperOptions {
   options: CloudflareOptions;
@@ -98,26 +99,64 @@ export function wrapRequestHandler(
         // Note: This span will not have a duration unless I/O happens in the handler. This is
         // because of how the cloudflare workers runtime works.
         // See: https://developers.cloudflare.com/workers/runtime-apis/performance/
-        return startSpan(
-          {
-            name,
-            attributes,
-          },
-          async span => {
-            try {
-              const res = await handler();
-              setHttpStatus(span, res.status);
-              return res;
-            } catch (e) {
-              if (captureErrors) {
-                captureException(e, { mechanism: { handled: false, type: 'auto.http.cloudflare' } });
-              }
-              throw e;
-            } finally {
-              waitUntil?.(flush(2000));
+
+        // Use startSpanManual to control when span ends (needed for streaming responses)
+        return startSpanManual({ name, attributes }, async span => {
+          let res: Response;
+
+          try {
+            res = await handler();
+            setHttpStatus(span, res.status);
+          } catch (e) {
+            span.end();
+            if (captureErrors) {
+              captureException(e, { mechanism: { handled: false, type: 'auto.http.cloudflare' } });
             }
-          },
-        );
+            waitUntil?.(flush(2000));
+            throw e;
+          }
+
+          // Classify response to detect actual streaming
+          const classification = await classifyResponseStreaming(res);
+
+          if (classification.isStreaming && classification.response.body) {
+            // Streaming response detected - monitor consumption to keep span alive
+            const [clientStream, monitorStream] = classification.response.body.tee();
+
+            // Monitor stream consumption and end span when complete
+            const streamMonitor = (async () => {
+              const reader = monitorStream.getReader();
+
+              try {
+                let done = false;
+                while (!done) {
+                  const result = await reader.read();
+                  done = result.done;
+                }
+              } catch {
+                // Stream error or cancellation - will end span in finally
+              } finally {
+                reader.releaseLock();
+                span.end();
+                waitUntil?.(flush(2000));
+              }
+            })();
+
+            waitUntil?.(streamMonitor);
+
+            // Return response with client stream
+            return new Response(clientStream, {
+              status: classification.response.status,
+              statusText: classification.response.statusText,
+              headers: classification.response.headers,
+            });
+          }
+
+          // Non-streaming response - end span immediately and return original
+          span.end();
+          waitUntil?.(flush(2000));
+          return classification.response;
+        });
       },
     );
   });

packages/cloudflare/src/utils/streaming.ts

@@ -0,0 +1,64 @@
+export type StreamingGuess = {
+  response: Response;
+  isStreaming: boolean;
+};
+
+/**
+ * Classifies a Response as streaming or non-streaming.
+ *
+ * Uses multiple heuristics:
+ * - No body → not streaming
+ * - Content-Type: text/event-stream → streaming
+ * - Content-Length header present → not streaming
+ * - Otherwise: attempts immediate read to detect behavior
+ *   - Stream empty (done) → not streaming
+ *   - Got data without Content-Length → streaming
+ *   - Got data with Content-Length → not streaming
+ *
+ * Note: Probing will tee() the stream and return a new Response object.
+ *
+ * @param res - The Response to classify
+ * @returns Classification result with safe-to-return Response
+ */
+export async function classifyResponseStreaming(res: Response): Promise<StreamingGuess> {
+  if (!res.body) {
+    return { response: res, isStreaming: false };
+  }
+
+  const contentType = res.headers.get('content-type') ?? '';
+  const contentLength = res.headers.get('content-length');
+
+  // Fast path: Server-Sent Events
+  if (/^text\/event-stream\b/i.test(contentType)) {
+    return { response: res, isStreaming: true };
+  }
+
+  // Fast path: Content-Length indicates buffered response
+  if (contentLength && /^\d+$/.test(contentLength)) {
+    return { response: res, isStreaming: false };
+  }
+
+  // Probe the stream by trying to read first chunk immediately
+  // After tee(), must use the teed stream (original is locked)
+  const [probeStream, passStream] = res.body.tee();
+  const reader = probeStream.getReader();
+
+  try {
+    const { done } = await reader.read();
+    reader.releaseLock();
+
+    const teededResponse = new Response(passStream, res);
+
+    if (done) {
+      // Stream completed immediately - buffered (empty body)
+      return { response: teededResponse, isStreaming: false };
+    }
+
+    // Got data - treat as streaming if no Content-Length header
+    return { response: teededResponse, isStreaming: contentLength == null };
+  } catch {
+    reader.releaseLock();
+    // Error reading - treat as non-streaming to be safe
+    return { response: new Response(passStream, res), isStreaming: false };
+  }
+}

packages/cloudflare/test/durableobject.test.ts

@@ -133,11 +133,25 @@ describe('instrumentDurableObjectWithSentry', () => {
       waitUntil,
     } as unknown as ExecutionContext;
     const dObject: any = Reflect.construct(instrumented, [context, {} as any]);
-    expect(() => dObject.fetch(new Request('https://example.com'))).not.toThrow();
-    expect(flush).not.toBeCalled();
-    expect(waitUntil).toHaveBeenCalledOnce();
+
+    // Call fetch (don't await yet)
+    const responsePromise = dObject.fetch(new Request('https://example.com'));
+
+    // Advance past classification timeout and get response
+    vi.advanceTimersByTime(30);
+    const response = await responsePromise;
+
+    // Consume response (triggers span end for buffered responses)
+    await response.text();
+
+    // The flush should now be queued in waitUntil
+    expect(waitUntil).toHaveBeenCalled();
+
+    // Advance to trigger the setTimeout in the handler's waitUntil
     vi.advanceTimersToNextTimer();
     await Promise.all(waitUntil.mock.calls.map(([p]) => p));
+
+    // Now flush should have been called
     expect(flush).toBeCalled();
   });
 

packages/cloudflare/test/handler.test.ts

@@ -72,7 +72,11 @@ describe('withSentry', () => {
         createMockExecutionContext(),
       );
 
-      expect(result).toBe(response);
+      // Response may be wrapped for streaming detection, verify content
+      expect(result?.status).toBe(response.status);
+      if (result) {
+        expect(await result.text()).toBe('test');
+      }
     });
 
     test('merges options from env and callback', async () => {

packages/cloudflare/test/pages-plugin.test.ts

@@ -52,6 +52,8 @@ describe('sentryPagesPlugin', () => {
       pluginArgs: MOCK_OPTIONS,
     });
 
-    expect(result).toBe(response);
+    // Response may be wrapped for streaming detection, verify content
+    expect(result.status).toBe(response.status);
+    expect(await result.text()).toBe('test');
   });
 });

packages/cloudflare/test/request.test.ts

@@ -33,7 +33,9 @@ describe('withSentry', () => {
       { options: MOCK_OPTIONS, request: new Request('https://example.com'), context: createMockExecutionContext() },
       () => response,
     );
-    expect(result).toBe(response);
+    // Response may be wrapped for streaming detection, verify content matches
+    expect(result.status).toBe(response.status);
+    expect(await result.text()).toBe('test');
   });
 
   test('flushes the event after the handler is done using the cloudflare context.waitUntil', async () => {
@@ -48,6 +50,25 @@ describe('withSentry', () => {
     expect(waitUntilSpy).toHaveBeenLastCalledWith(expect.any(Promise));
   });
 
+  test('handles streaming responses correctly', async () => {
+    const stream = new ReadableStream({
+      start(controller) {
+        controller.enqueue(new TextEncoder().encode('chunk1'));
+        controller.enqueue(new TextEncoder().encode('chunk2'));
+        controller.close();
+      },
+    });
+    const streamingResponse = new Response(stream);
+
+    const result = await wrapRequestHandler(
+      { options: MOCK_OPTIONS, request: new Request('https://example.com'), context: createMockExecutionContext() },
+      () => streamingResponse,
+    );
+
+    const text = await result.text();
+    expect(text).toBe('chunk1chunk2');
+  });
+
   test("doesn't error if context is undefined", () => {
     expect(() =>
       wrapRequestHandler(
@@ -69,7 +90,7 @@ describe('withSentry', () => {
   });
 
   test('flush must be called when all waitUntil are done', async () => {
-    const flush = vi.spyOn(SentryCore.Client.prototype, 'flush');
+    const flushSpy = vi.spyOn(SentryCore.Client.prototype, 'flush');
     vi.useFakeTimers();
     onTestFinished(() => {
       vi.useRealTimers();
@@ -83,13 +104,17 @@ describe('withSentry', () => {
 
     await wrapRequestHandler({ options: MOCK_OPTIONS, request: new Request('https://example.com'), context }, () => {
       addDelayedWaitUntil(context);
-      return new Response('test');
+      const response = new Response('test');
+      // Add Content-Length to skip probing
+      response.headers.set('content-length', '4');
+      return response;
     });
-    expect(flush).not.toBeCalled();
+    expect(flushSpy).not.toBeCalled();
     expect(waitUntil).toBeCalled();
-    vi.advanceTimersToNextTimerAsync().then(() => vi.runAllTimers());
+    await vi.advanceTimersToNextTimerAsync();
+    vi.runAllTimers();
     await Promise.all(waits);
-    expect(flush).toHaveBeenCalledOnce();
+    expect(flushSpy).toHaveBeenCalledOnce();
   });
 
   describe('scope instrumentation', () => {
@@ -303,6 +328,9 @@ describe('withSentry', () => {
         },
       );
 
+      // Wait for async span end and transaction capture
+      await new Promise(resolve => setTimeout(resolve, 50));
+
       expect(sentryEvent.transaction).toEqual('GET /');
       expect(sentryEvent.spans).toHaveLength(0);
       expect(sentryEvent.contexts?.trace).toEqual({