diff --git a/src/music/local-extract-fallback.test.ts b/src/music/local-extract-fallback.test.ts
new file mode 100644
index 0000000..ba12c8f
--- /dev/null
+++ b/src/music/local-extract-fallback.test.ts
@@ -0,0 +1,108 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+// unlinkSync/rmdirSync are NOT mocked below, so the test's own fixture
+// teardown is unaffected by the simulated lock on *.mp4.
+import { mkdtempSync, statSync, existsSync, readFileSync, unlinkSync, readdirSync, rmdirSync } from "node:fs";
+import { spawnSync } from "node:child_process";
+import { createRequire } from "node:module";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+
+/**
+ * #149: when the audio track is extracted successfully but the source video
+ * cannot be deleted (Windows keeps files locked briefly — rmSync with
+ * force:true still throws EBUSY/EPERM), the record must fall back to the
+ * ORIGINAL container completely: both the path AND the recorded size.
+ *
+ * Committing the size before the delete succeeded would leave the record
+ * claiming the small extracted size while still holding the whole video, so
+ * totalBytes() under-counts and the upload directory grows past its quota.
+ *
+ * This lives in its own file because it partially mocks node:fs, which would
+ * otherwise leak into every other test in local.test.ts.
+ */
+vi.mock("node:fs", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("node:fs")>();
+  return {
+    ...actual,
+    default: actual,
+    rmSync: (path: string, opts?: object) => {
+      // Simulate the lock on the source video only; every other delete
+      // (the discarded .mka, temp dirs, the reject path) behaves normally.
+      if (typeof path === "string" && path.endsWith(".mp4")) {
+        const err = new Error("EBUSY: resource busy or locked") as NodeJS.ErrnoException;
+        err.code = "EBUSY";
+        throw err;
+      }
+      return actual.rmSync(path, opts as never);
+    },
+  };
+});
+
+const { LocalMusicProvider } = await import("./local.js");
+
+const ffmpeg: string | null = (() => {
+  try {
+    return createRequire(import.meta.url)("ffmpeg-static") as string;
+  } catch {
+    return null;
+  }
+})();
+const have = !!ffmpeg && spawnSync(ffmpeg, ["-version"], { stdio: "ignore" }).status === 0;
+
+let dir: string;
+beforeEach(() => { dir = mkdtempSync(join(tmpdir(), "local-extract-fallback-")); });
+afterEach(() => {
+  // Recursive teardown without rmSync (mocked above for *.mp4).
+  for (const f of readdirSync(dir)) {
+    try { unlinkSync(join(dir, f)); } catch { /* best effort */ }
+  }
+  try { rmdirSync(dir); } catch { /* best effort */ }
+});
+
+describe("LocalMusicProvider: source video cannot be deleted after extraction (#149)", () => {
+  it.runIf(have)("keeps the original container AND its real size, not the extracted size", async () => {
+    const src = join(dir, "fixture.mp4");
+    const r = spawnSync(ffmpeg!, [
+      "-y", "-hide_banner", "-loglevel", "error",
+      "-f", "lavfi", "-i", "testsrc=s=320x240:r=25:d=3",
+      "-f", "lavfi", "-i", "sine=f=440:d=3",
+      "-c:v", "libx264", "-b:v", "800k", "-c:a", "aac", "-shortest", src,
+    ], { stdio: "ignore" });
+    expect(r.status).toBe(0);
+
+    const bytes = readFileSync(src);
+    unlinkSync(src); // uploadAudio writes its own copy under a uuid name
+
+    const p = new LocalMusicProvider(dir);
+    const song = await p.uploadAudio({
+      buffer: bytes, originalName: "fixture.mp4", mimeType: "video/mp4",
+    });
+
+    const resolved = await p.getSongUrl(song.id);
+    expect(resolved).not.toBeNull();
+
+    // Fell back to the original container — the extract was discarded.
+    expect(resolved!.url.endsWith(".mp4")).toBe(true);
+    expect(existsSync(resolved!.url)).toBe(true);
+    expect(existsSync(resolved!.url.replace(/\.mp4$/, ".mka"))).toBe(false);
+
+    const onDisk = statSync(resolved!.url).size;
+    expect(onDisk).toBe(bytes.length);
+
+    // The RECORDED size drives the quota (totalBytes()), so it must describe
+    // the file actually retained. It is not exposed through search()/toSong,
+    // but it is persisted to index.json — read it back from there.
+    const record = (JSON.parse(readFileSync(join(dir, "index.json"), "utf8")) as Array<{
+      id: string; size: number; filePath: string;
+    }>).find((r) => r.id === song.id);
+    expect(record).toBeDefined();
+    expect(record!.filePath.endsWith(".mp4")).toBe(true);
+    // Before the fix this was the (much smaller) .mka size while the whole
+    // .mp4 stayed on disk, so the quota under-counted the retained bytes.
+    expect(record!.size).toBe(bytes.length);
+
+    // Sanity: the extract really is much smaller, so a wrong commit order
+    // would have been clearly observable rather than a rounding error.
+    expect(onDisk).toBeGreaterThan(50_000);
+  }, 60000);
+});
diff --git a/src/music/local.ts b/src/music/local.ts
index 692a84a..82f5542 100644
--- a/src/music/local.ts
+++ b/src/music/local.ts
@@ -330,9 +330,16 @@ export class LocalMusicProvider implements MusicProvider {
       const extracted = path.join(this.uploadDir, `${id}${EXTRACTED_AUDIO_EXT}`);
       if (await extractAudioTrack(filePath, extracted)) {
         try {
-          size = statSync(extracted).size;
+          // Commit filePath and size TOGETHER, and only after the source is
+          // actually gone. rmSync(force) still throws EBUSY/EPERM on Windows,
+          // and assigning size first would leave the record claiming the
+          // small extracted size while still pointing at the whole video —
+          // which makes totalBytes() under-count and lets the upload
+          // directory grow past its quota.
+          const extractedSize = statSync(extracted).size;
           rmSync(filePath, { force: true });
           filePath = extracted;
+          size = extractedSize;
         } catch {
           // Could not stat/remove (Windows lock) — keep playing the original
           // container and drop the half-finished extract.