diff --git a/packages/cli/src/commands/init.test.ts b/packages/cli/src/commands/init.test.ts
index ded2b14ca5..259d2837be 100644
--- a/packages/cli/src/commands/init.test.ts
+++ b/packages/cli/src/commands/init.test.ts
@@ -1,6 +1,7 @@
-import { describe, expect, it } from "vitest";
+import { describe, expect, it, vi } from "vitest";
 import { spawnSync } from "node:child_process";
 import {
+  chmodSync,
   copyFileSync,
   existsSync,
   mkdirSync,
@@ -17,6 +18,7 @@ import {
   injectTailwindBrowserScript,
   nameTooLongMessage,
   resolveVideoDurationSeconds,
+  transcodeToMp4,
 } from "./init.js";
 
 const cliEntry = resolve(fileURLToPath(import.meta.url), "..", "..", "cli.ts");
@@ -698,3 +700,30 @@ describe("applyResolutionPreset", () => {
     }
   });
 });
+
+describe("transcodeToMp4", () => {
+  it.skipIf(process.platform === "win32")(
+    "finishes when ffmpeg logs far more than a pipe buffer holds",
+    async () => {
+      const dir = mkdtempSync(join(tmpdir(), "hf-init-ffmpeg-log-"));
+      const ffmpeg = join(dir, "ffmpeg");
+      const output = join(dir, "out.mp4");
+      // Blocking writes, like ffmpeg's own log: 1 MB stalls on a pipe nobody reads.
+      const script = `const fs = require("node:fs");
+const line = Buffer.alloc(1024, "x");
+for (let i = 0; i < 1024; i++) fs.writeSync(2, line);
+fs.writeFileSync(process.argv.at(-1), "");`;
+      writeFileSync(ffmpeg, `#!${process.execPath}\n${script}\n`);
+      chmodSync(ffmpeg, 0o755);
+      vi.stubEnv("HYPERFRAMES_FFMPEG_PATH", ffmpeg);
+      try {
+        await expect(transcodeToMp4(join(dir, "in.mov"), output)).resolves.toBe(true);
+        expect(existsSync(output)).toBe(true);
+      } finally {
+        vi.unstubAllEnvs();
+        rmSync(dir, { recursive: true, force: true });
+      }
+    },
+    5_000,
+  );
+});
diff --git a/packages/cli/src/commands/init.ts b/packages/cli/src/commands/init.ts
index 80f082d4cf..b3bf347f1b 100644
--- a/packages/cli/src/commands/init.ts
+++ b/packages/cli/src/commands/init.ts
@@ -211,7 +211,7 @@ export function transcodeToMp4(inputPath: string, outputPath: string): Promise<b
         "-y",
         outputPath,
       ],
-      { stdio: "pipe", windowsHide: true },
+      { stdio: "ignore", windowsHide: true },
     );
 
     child.on("close", (code) => resolvePromise(code === 0));
diff --git a/packages/cli/src/commands/render.ts b/packages/cli/src/commands/render.ts
index 36d508644d..fba7f97037 100644
--- a/packages/cli/src/commands/render.ts
+++ b/packages/cli/src/commands/render.ts
@@ -847,7 +847,7 @@ async function renderDocker(
       const stderrTail = createStderrTail();
       // stderr is piped so the failure can name its cause; it is still echoed live.
       const child = spawn("docker", dockerArgs, {
-        stdio: options.quiet ? ["pipe", "pipe", "pipe"] : ["inherit", "inherit", "pipe"],
+        stdio: options.quiet ? ["pipe", "ignore", "pipe"] : ["inherit", "inherit", "pipe"],
       });
       child.stderr?.on("data", (chunk: Buffer) => {
         process.stderr.write(chunk);