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 };
   }