diff --git a/extensions/elevenlabs/tts.test.ts b/extensions/elevenlabs/tts.test.ts
index 1d0be96eee9..65d3accd79c 100644
--- a/extensions/elevenlabs/tts.test.ts
+++ b/extensions/elevenlabs/tts.test.ts
@@ -1,32 +1,10 @@
 import { afterEach, describe, expect, it, vi } from "vitest";
+import { createStreamingErrorResponse } from "../test-support/streaming-error-response.js";
 import { elevenLabsTTS } from "./tts.js";
 
 describe("elevenlabs tts diagnostics", () => {
   const originalFetch = globalThis.fetch;
 
-  function createStreamingErrorResponse(params: {
-    status: number;
-    chunkCount: number;
-    chunkSize: number;
-    byte: number;
-  }): { response: Response; getReadCount: () => number } {
-    let reads = 0;
-    const stream = new ReadableStream<Uint8Array>({
-      pull(controller) {
-        if (reads >= params.chunkCount) {
-          controller.close();
-          return;
-        }
-        reads += 1;
-        controller.enqueue(new Uint8Array(params.chunkSize).fill(params.byte));
-      },
-    });
-    return {
-      response: new Response(stream, { status: params.status }),
-      getReadCount: () => reads,
-    };
-  }
-
   function createDefaultTtsRequest() {
     return {
       text: "hello",
diff --git a/extensions/openai/tts.test.ts b/extensions/openai/tts.test.ts
index 2860f57e59b..0b8a764ef0c 100644
--- a/extensions/openai/tts.test.ts
+++ b/extensions/openai/tts.test.ts
@@ -3,6 +3,7 @@ import os from "node:os";
 import path from "node:path";
 import { describe, expect, it, vi } from "vitest";
 import { installDebugProxyTestResetHooks } from "../test-support/debug-proxy-env-test-helpers.js";
+import { createStreamingErrorResponse } from "../test-support/streaming-error-response.js";
 import {
   isValidOpenAIModel,
   isValidOpenAIVoice,
@@ -79,29 +80,6 @@ describe("openai tts", () => {
   });
 
   describe("openaiTTS diagnostics", () => {
-    function createStreamingErrorResponse(params: {
-      status: number;
-      chunkCount: number;
-      chunkSize: number;
-      byte: number;
-    }): { response: Response; getReadCount: () => number } {
-      let reads = 0;
-      const stream = new ReadableStream<Uint8Array>({
-        pull(controller) {
-          if (reads >= params.chunkCount) {
-            controller.close();
-            return;
-          }
-          reads += 1;
-          controller.enqueue(new Uint8Array(params.chunkSize).fill(params.byte));
-        },
-      });
-      return {
-        response: new Response(stream, { status: params.status }),
-        getReadCount: () => reads,
-      };
-    }
-
     it("includes parsed provider detail and request id for JSON API errors", async () => {
       const fetchMock = vi.fn(
         async () =>
diff --git a/extensions/test-support/streaming-error-response.ts b/extensions/test-support/streaming-error-response.ts
new file mode 100644
index 00000000000..1ae8275c75d
--- /dev/null
+++ b/extensions/test-support/streaming-error-response.ts
@@ -0,0 +1,22 @@
+export function createStreamingErrorResponse(params: {
+  status: number;
+  chunkCount: number;
+  chunkSize: number;
+  byte: number;
+}): { response: Response; getReadCount: () => number } {
+  let reads = 0;
+  const stream = new ReadableStream<Uint8Array>({
+    pull(controller) {
+      if (reads >= params.chunkCount) {
+        controller.close();
+        return;
+      }
+      reads += 1;
+      controller.enqueue(new Uint8Array(params.chunkSize).fill(params.byte));
+    },
+  });
+  return {
+    response: new Response(stream, { status: params.status }),
+    getReadCount: () => reads,
+  };
+}