From a14b30605bdce24991db2ccacf88a41c42a34404 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 10 Apr 2026 14:04:42 +0000
Subject: [PATCH 1/2] Initial plan


From 51352ee7b433fe7fc06e51028fdc77757e93ab83 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 10 Apr 2026 14:32:45 +0000
Subject: [PATCH 2/2] fix(cloudflare,deno): Remove overly aggressive text/plain
 streaming classification

The `classifyResponseStreaming` function classified `text/plain` responses
without a `Content-Length` header as streaming. This heuristic was too
aggressive because `new Response('some text')` creates a `text/plain`
response without Content-Length, causing simple non-streaming responses
to take the streaming code path.

In the streaming path, the span end and transaction flush are delayed
until a stream monitor completes, which can cause timing issues when
the response is passed between Durable Objects and Workers in the
Cloudflare runtime, leading to flaky test timeouts.

Removing this rule ensures simple text/plain responses are processed
through the non-streaming (immediate span end + flush) code path.
Known streaming content types (SSE, NDJSON, JSON streaming) are still
correctly detected.

Fixes #20209

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

Agent-Logs-Url: https://github.com/getsentry/sentry-javascript/sessions/b58267a8-c6d6-4fc0-b4fb-82b5843bbf70

Co-authored-by: Lms24 <8420481+Lms24@users.noreply.github.com>
---
 packages/cloudflare/src/utils/streaming.ts | 6 +-----
 packages/deno/src/utils/streaming.ts       | 6 +-----
 2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/packages/cloudflare/src/utils/streaming.ts b/packages/cloudflare/src/utils/streaming.ts
index fee67cbb9f2a..b479edee06a7 100644
--- a/packages/cloudflare/src/utils/streaming.ts
+++ b/packages/cloudflare/src/utils/streaming.ts
@@ -8,7 +8,6 @@ export type StreamingGuess = {
  * Heuristics:
  * - No body → not streaming
  * - Known streaming Content-Types → streaming (SSE, NDJSON, JSON streaming)
- * - text/plain without Content-Length → streaming (some AI APIs)
  * - Otherwise → not streaming (conservative default, including HTML/SSR)
  *
  * We avoid probing the stream to prevent blocking on transform streams (like injectTraceMetaTags)
@@ -20,18 +19,15 @@ export function classifyResponseStreaming(res: Response): StreamingGuess {
   }
 
   const contentType = res.headers.get('content-type') ?? '';
-  const contentLength = res.headers.get('content-length');
 
   // Streaming: Known streaming content types
   // - text/event-stream: Server-Sent Events (Vercel AI SDK, real-time APIs)
   // - application/x-ndjson, application/ndjson: Newline-delimited JSON
   // - application/stream+json: JSON streaming
-  // - text/plain (without Content-Length): Some AI APIs use this for streaming text
   if (
     /^text\/event-stream\b/i.test(contentType) ||
     /^application\/(x-)?ndjson\b/i.test(contentType) ||
-    /^application\/stream\+json\b/i.test(contentType) ||
-    (/^text\/plain\b/i.test(contentType) && !contentLength)
+    /^application\/stream\+json\b/i.test(contentType)
   ) {
     return { isStreaming: true };
   }
diff --git a/packages/deno/src/utils/streaming.ts b/packages/deno/src/utils/streaming.ts
index 045a104c5e93..be9a6e4051ed 100644
--- a/packages/deno/src/utils/streaming.ts
+++ b/packages/deno/src/utils/streaming.ts
@@ -10,7 +10,6 @@ export type StreamingGuess = {
  * Heuristics:
  * - No body → not streaming
  * - Known streaming Content-Types → streaming (SSE, NDJSON, JSON streaming)
- * - text/plain without Content-Length → streaming (some AI APIs)
  * - Otherwise → not streaming (conservative default, including HTML/SSR)
  *
  * We avoid probing the stream to prevent blocking on transform streams (like injectTraceMetaTags)
@@ -22,18 +21,15 @@ export function classifyResponseStreaming(res: Response): StreamingGuess {
   }
 
   const contentType = res.headers.get('content-type') ?? '';
-  const contentLength = res.headers.get('content-length');
 
   // Streaming: Known streaming content types
   // - text/event-stream: Server-Sent Events (Vercel AI SDK, real-time APIs)
   // - application/x-ndjson, application/ndjson: Newline-delimited JSON
   // - application/stream+json: JSON streaming
-  // - text/plain (without Content-Length): Some AI APIs use this for streaming text
   if (
     /^text\/event-stream\b/i.test(contentType) ||
     /^application\/(x-)?ndjson\b/i.test(contentType) ||
-    /^application\/stream\+json\b/i.test(contentType) ||
-    (/^text\/plain\b/i.test(contentType) && !contentLength)
+    /^application\/stream\+json\b/i.test(contentType)
   ) {
     return { isStreaming: true };
   }