diff --git a/packages/adapters/src/media/transcription.test.ts b/packages/adapters/src/media/transcription.test.ts
index 158acff..d39c55e 100644
--- a/packages/adapters/src/media/transcription.test.ts
+++ b/packages/adapters/src/media/transcription.test.ts
@@ -4,15 +4,19 @@ import { join } from "node:path";
 import type { MediaJobContext, MediaJobInputFile, MediaJobOutputFile } from "@rakazo/adapter-kit";
 import { MediaJobDeferredError } from "@rakazo/adapter-kit";
 import type { MediaOutput, MediaSettings } from "@rakazo/contracts";
-import { afterEach, describe, expect, it } from "vitest";
+import { afterAll, afterEach, beforeAll, describe, expect, it } from "vitest";
 import { createOpenAiCompatibleTranscriptionProvider } from "../openai-compatible-transcription.js";
 import {
   EmulatorTranscriptionProvider,
   OpenAiCompatibleTranscriptionServerEmulator,
 } from "../transcription-emulator.js";
+import { detectFfmpeg, runFfmpeg } from "./ffmpeg.js";
+import type { TestClips } from "./media-test-support.js";
+import { createTestClips, fakeMediaJobContext } from "./media-test-support.js";
 import type { TranscriptionAudioTools } from "./transcription.js";
 import {
   createTranscriptionOperations,
+  ffmpegTranscriptionAudio,
   planAudioChunks,
   TRANSCRIPT_SUMMARY_MAX_CHARS,
   transcribeChunks,
@@ -326,3 +330,69 @@ describe("planAudioChunks", () => {
     ]);
   });
 });
+
+const ffmpeg = await detectFfmpeg();
+
+// CI runners without ffmpeg skip these; the unit tests above cover the same paths with fakes.
+describe.skipIf(!ffmpeg)("transcribe with ffmpeg", () => {
+  let clips: TestClips;
+  let longTone: string;
+
+  beforeAll(async () => {
+    clips = await createTestClips();
+    longTone = join(clips.dir, "long-tone.m4a");
+    await runFfmpeg([
+      ...["-f", "lavfi", "-i", "sine=frequency=330:sample_rate=44100:duration=12"],
+      ...["-c:a", "aac", `file:${longTone}`],
+    ]);
+  });
+  afterAll(async () => {
+    if (clips) await rm(clips.dir, { recursive: true, force: true });
+  });
+
+  function ffmpegOperation(maxBytes?: number) {
+    return operation(TRANSCRIPTION, { audio: ffmpegTranscriptionAudio, maxBytes });
+  }
+
+  it("transcribes a video's audio as 16 kHz mono WAV", async () => {
+    const { registration, server } = ffmpegOperation();
+    const job = await fakeMediaJobContext(
+      { artifactId: "video-1" },
+      { "video-1": { path: clips.landscape, name: "landscape.mp4", mimeType: "video/mp4" } },
+    );
+    dirs.push(job.tempDir);
+    await registration.handler.run(job.context);
+    // Three seconds at 32,000 bytes per second plus the WAV header.
+    expect(server.requests).toEqual([
+      expect.objectContaining({ fileName: "landscape.wav", fileType: "audio/wav" }),
+    ]);
+    expect(Math.abs(server.requests[0]!.fileSize - 3 * 32_000)).toBeLessThan(2_000);
+    expect(job.outputs.map((output) => output.name)).toEqual(["landscape.srt", "landscape.vtt"]);
+  });
+
+  it("uploads a long recording in ranges below the server's limit", async () => {
+    const { registration, server } = ffmpegOperation(1024);
+    const job = await fakeMediaJobContext(
+      { artifactId: "audio-1" },
+      { "audio-1": { path: longTone, name: "long-tone.m4a", mimeType: "audio/mp4" } },
+    );
+    dirs.push(job.tempDir);
+    await registration.handler.run(job.context);
+    expect(server.requests).toHaveLength(2);
+    expect(Math.abs(server.requests[0]!.fileSize - 10 * 32_000)).toBeLessThan(2_000);
+    expect(Math.abs(server.requests[1]!.fileSize - 2 * 32_000)).toBeLessThan(2_000);
+  });
+
+  it("refuses a video without sound", async () => {
+    const { registration, server } = ffmpegOperation();
+    const job = await fakeMediaJobContext(
+      { artifactId: "video-2" },
+      { "video-2": { path: clips.silentPortrait, name: "silent.mp4", mimeType: "video/mp4" } },
+    );
+    dirs.push(job.tempDir);
+    await expect(registration.handler.run(job.context)).rejects.toThrow(
+      "The file has no audio track.",
+    );
+    expect(server.requests).toEqual([]);
+  });
+});