diff --git a/packages/cli/src/media-use/lib/manifest.mjs b/packages/cli/src/media-use/lib/manifest.mjs
index 56b533aaa3..49e387690f 100644
--- a/packages/cli/src/media-use/lib/manifest.mjs
+++ b/packages/cli/src/media-use/lib/manifest.mjs
@@ -79,6 +79,9 @@ export function appendRecord(projectDir, record) {
   appendFileSync(p, line);
 }
 
+/** Sources that mean the agent made or fetched the file; any other file is the person's own. */
+export const AGENT_SOURCES = ["generated", "search", "bundled"];
+
 /** The record a path has now: the manifest only appends, so the last one for a path wins. */
 export function latestRecordFor(projectDir, path) {
   return readManifest(projectDir).findLast((record) => record.path === path);
diff --git a/packages/cli/src/media-use/resolve.mjs b/packages/cli/src/media-use/resolve.mjs
index a529fd313d..80bc42ec2e 100644
--- a/packages/cli/src/media-use/resolve.mjs
+++ b/packages/cli/src/media-use/resolve.mjs
@@ -5,6 +5,7 @@ import { existsSync, statSync, writeFileSync, renameSync, rmSync, realpathSync }
 import { resolve, join, extname, basename, relative, isAbsolute, sep } from "node:path";
 import { parseArgs } from "node:util";
 import {
+  AGENT_SOURCES,
   appendRecord,
   latestRecordFor,
   recordInPlace,
@@ -60,7 +61,6 @@ import {
 } from "./lib/local-media-search.mjs";
 
 const INGEST_TYPES = listTypes();
-const RECORDED_SOURCES = ["generated", "search", "bundled"];
 const DEFAULT_EXT = {
   bgm: ".wav",
   sfx: ".mp3",
@@ -130,7 +130,7 @@ Options:
   --reuse <sha>   Import a specific global-cache asset (by content sha/prefix,
                   from --candidates) into this project
   --from <file>   Freeze a local file or direct public URL (ingest)
-  --source <how>  With --from: how the file was made (${RECORDED_SOURCES.join(" | ")}).
+  --source <how>  With --from: how the file was made (${AGENT_SOURCES.join(" | ")}).
                   A file already inside the project is then recorded where it is
   --params <json> Build an explicit parametric LUT (lut/grade only)
   --for <media>   Analyze a local image/video and add measured grade adjust
@@ -918,8 +918,8 @@ async function ingest(src) {
     console.error(`error: refusing to ingest a 0-byte file: ${src}`);
     process.exit(2);
   }
-  if (args.source && !RECORDED_SOURCES.includes(args.source)) {
-    console.error(`error: --source takes one of: ${RECORDED_SOURCES.join(", ")}`);
+  if (args.source && !AGENT_SOURCES.includes(args.source)) {
+    console.error(`error: --source takes one of: ${AGENT_SOURCES.join(", ")}`);
     process.exit(2);
   }
   if (args.source && (type === "lut" || type === "grade")) {
diff --git a/skills-manifest.json b/skills-manifest.json
index 33fd821fbe..da195b39f1 100644
--- a/skills-manifest.json
+++ b/skills-manifest.json
@@ -54,7 +54,7 @@
       "files": 1
     },
     "media-use": {
-      "hash": "1871ad36628ac54b",
+      "hash": "0744050e3114e60a",
       "files": 104
     },
     "motion-graphics": {
diff --git a/skills/media-use/audio/references/bgm.md b/skills/media-use/audio/references/bgm.md
index 9c43da908a..e6483479d4 100644
--- a/skills/media-use/audio/references/bgm.md
+++ b/skills/media-use/audio/references/bgm.md
@@ -15,6 +15,8 @@ One music bed per composition, produced by the shared audio engine (`scripts/aud
 - **`query`** — the mood, used for retrieval and as a fallback prompt seed (e.g. a storyboard's `music:` field, falling back to `message` → `arc` → `"calm cinematic underscore"`).
 - **`prompt`** — an explicit full prompt for generation; omit and the engine infers one (see Mood inference). Optional `blob` / `archetype` / `arc` feed that inference.
 
+Both routes keep a file of yours already at the output name: the engine writes the next free name (`track-2.mp3`), reports it as an anomaly, and `bgm.path` carries the real path.
+
 ## HeyGen retrieval (default)
 
 `searchSounds(query, "music", { limit: 5 })` → `GET /audio/sounds?query=<mood>&type=music&limit=5`. Take the top result (ranked by `score`), download its presigned `audio_url` → `assets/bgm/track.mp3`. Synchronous. No match → skip (BGM is optional; never fail the render over it). Cue written to `audio_meta.json`:
diff --git a/skills/media-use/audio/references/sfx.md b/skills/media-use/audio/references/sfx.md
index 0fa1d28e77..9de60a3a8d 100644
--- a/skills/media-use/audio/references/sfx.md
+++ b/skills/media-use/audio/references/sfx.md
@@ -16,15 +16,14 @@ Each line names the effects it wants: `lines[].sfx: ["whoosh", "ui click"]`. The
   "id": "3",                       // joins the cue to the caller's model (frame / scene / segment)
   "name": "whoosh",
   "file": "assets/sfx/whoosh.mp3", // downloaded or copied, relative to project root
-  "source": "heygen" | "local" | "project", // which route resolved it; "project": a file already
-                                   // in assets/sfx under that name that is not the library's copy
+  "source": "heygen" | "local",    // which route resolved it
   "offset_s": 0,                   // delay from the line's start
   "duration_s": 0.57,
   "volume": 0.35                   // SFX sit UNDER voice + BGM
 }
 ```
 
-A cue that matches nothing is **skipped** (recorded as an anomaly); SFX never blocks a render.
+A cue that matches nothing is **skipped** (recorded as an anomaly); SFX never blocks a render. Neither route replaces a file of yours already at the output name: the cue gets the next free name (`whoosh-2.mp3`), reported as an anomaly, and `file` carries the real path.
 
 ## HeyGen retrieval (credentialed)
 
diff --git a/skills/media-use/audio/references/tts.md b/skills/media-use/audio/references/tts.md
index 468ca78a14..cb295e53dd 100644
--- a/skills/media-use/audio/references/tts.md
+++ b/skills/media-use/audio/references/tts.md
@@ -135,7 +135,7 @@ node <SKILL_DIR>/audio/scripts/audio.mjs \
   --request ./audio_request.json --hyperframes . --out ./audio_meta.json --only tts
 ```
 
-The engine saves `assets/voice/intro.wav`, measures its duration, and transcribes
+The engine saves `assets/voice/intro.wav` (or `intro-2.wav` when a file of yours already has that name; `voices[].path` says which), measures its duration, and transcribes
 it into `voices[].words` in `audio_meta.json`. Check that every requested line
 has audio and nonempty word timings before building a captioned video. Review
 the timings against the actual audio; transcription is estimated alignment,
diff --git a/skills/media-use/audio/scripts/audio.mjs b/skills/media-use/audio/scripts/audio.mjs
index d0437028e7..3f84aede4d 100644
--- a/skills/media-use/audio/scripts/audio.mjs
+++ b/skills/media-use/audio/scripts/audio.mjs
@@ -55,7 +55,7 @@ import { generateBgmDetached, inferBgmPrompt, retrieveBgm } from "./lib/bgm.mjs"
 import { resolveSfx } from "./lib/sfx.mjs";
 import { mapWithConcurrency } from "./lib/concurrency.mjs";
 import { openAudioMeta } from "./lib/audio-meta.mjs";
-import { recordInManifest, writtenAssets } from "./lib/media-record.mjs";
+import { recordInManifest, voicePaths, writtenAssets } from "./lib/media-record.mjs";
 
 const HERE = dirname(fileURLToPath(import.meta.url));
 const argv = process.argv.slice(2);
@@ -138,6 +138,7 @@ if (only.has("tts") && lines.length) {
     lang,
   });
   console.error(`· tts: ${ttsProvider} · voice ${voiceId} · ${lines.length} line(s)`);
+  const paths = voicePaths(hyperframesDir, lines, anomalies);
   const synthLine = async (line) => {
     const id = String(line.id);
     const text = String(line.text ?? "").trim();
@@ -145,7 +146,7 @@ if (only.has("tts") && lines.length) {
       anomalies.push(`line ${id}: empty text — skipped`);
       return null;
     }
-    const rel = `assets/voice/${id}.wav`;
+    const rel = paths.get(id);
     const abs = join(hyperframesDir, rel);
     const { ok, words, error } = await synthesizeOne({
       provider: ttsProvider,
@@ -217,6 +218,7 @@ if (only.has("bgm")) {
         headers: heygenAuthHeaders(),
         hyperframesDir,
         hasVoice,
+        anomalies,
       });
       if (bgm) {
         bgmFields.bgm_provider = "heygen";
@@ -243,6 +245,7 @@ if (only.has("bgm")) {
       lyriaRecipe: existsSync(lyriaRecipe) ? lyriaRecipe : null,
       seedSeconds,
       hasVoice,
+      anomalies,
     });
     if (gen.disabled) {
       anomalies.push(`bgm: ${gen.reason}`);
diff --git a/skills/media-use/audio/scripts/audio.test.mjs b/skills/media-use/audio/scripts/audio.test.mjs
index 3d7de20316..505cdecae7 100644
--- a/skills/media-use/audio/scripts/audio.test.mjs
+++ b/skills/media-use/audio/scripts/audio.test.mjs
@@ -1,9 +1,10 @@
 import { strict as assert } from "node:assert";
 import { test } from "node:test";
-import { mkdtempSync, rmSync, existsSync, writeFileSync } from "node:fs";
+import { mkdtempSync, mkdirSync, readFileSync, rmSync, existsSync, writeFileSync } from "node:fs";
 import { join, dirname } from "node:path";
 import { tmpdir } from "node:os";
 import { fileURLToPath } from "node:url";
+import { recordInManifest } from "./lib/media-record.mjs";
 import { resolveSfx } from "./lib/sfx.mjs";
 
 // Proves the relocated engine (skills/media-use/audio/) still resolves its
@@ -48,9 +49,12 @@ test("an unknown cue is reported, not fatal", async () => {
   }
 });
 
-test("a person's own file under a bundled name is not labelled as the library's", async () => {
+test("a person's own file under a bundled name survives, and the cue gets the next free name", async () => {
   const dir = mkdtempSync(join(tmpdir(), "mu-audio-"));
   try {
+    const own = join(dir, "assets", "sfx", "whoosh.mp3");
+    mkdirSync(dirname(own), { recursive: true });
+    writeFileSync(own, "the person's own whoosh");
     const resolve = () =>
       resolveSfx({
         cues: [{ id: "1", name: "whoosh" }],
@@ -58,16 +62,65 @@ test("a person's own file under a bundled name is not labelled as the library's"
         hyperframesDir: dir,
         sfxLibDir,
       });
-    const copied = await resolve();
-    const reused = await resolve();
-    writeFileSync(join(dir, copied.sfx[0].file), "the person's own whoosh");
-    const own = await resolve();
 
+    const first = await resolve();
+    const second = await resolve();
+
+    assert.equal(readFileSync(own, "utf8"), "the person's own whoosh");
+    assert.deepEqual(
+      [first, second].map(({ sfx }) => [sfx[0].file, sfx[0].source]),
+      [
+        ["assets/sfx/whoosh-2.mp3", "local"],
+        ["assets/sfx/whoosh-2.mp3", "local"],
+      ],
+    );
     assert.deepEqual(
-      [copied, reused, own].map(({ sfx }) => sfx[0].source),
-      ["local", "local", "project"],
+      readFileSync(join(dir, "assets/sfx/whoosh-2.mp3")),
+      readFileSync(join(sfxLibDir, "whoosh.mp3")),
     );
   } finally {
     rmSync(dir, { recursive: true, force: true });
   }
 });
+
+test("two effects never share a file when one's name is taken by the person, run after run", async () => {
+  const dir = mkdtempSync(join(tmpdir(), "mu-audio-"));
+  try {
+    mkdirSync(join(dir, "assets", "sfx"), { recursive: true });
+    writeFileSync(join(dir, "assets", "sfx", "glitch.mp3"), "the person's own glitch");
+    const realFetch = globalThis.fetch;
+    globalThis.fetch = async (url) => {
+      const query = new URL(url).searchParams.get("query");
+      if (query)
+        return Response.json({ data: [{ audio_url: `https://sound.test/${query}`, score: 0.6 }] });
+      return new Response(`bytes of ${new URL(url).pathname}`);
+    };
+    const run = async (names) => {
+      const { sfx } = await resolveSfx({
+        cues: names.map((name, index) => ({ id: String(index), name })),
+        heygenOK: true,
+        headers: {},
+        hyperframesDir: dir,
+        sfxLibDir,
+      });
+      const files = sfx.map(({ file }) => file);
+      recordInManifest(
+        dir,
+        [...new Set(files)].map((path) => ({ path, type: "sfx", source: "search" })),
+      );
+      return files;
+    };
+    try {
+      assert.deepEqual(await run(["glitch"]), ["assets/sfx/glitch-2.mp3"]);
+      assert.deepEqual(await run(["glitch", "glitch 2", "glitch"]), [
+        "assets/sfx/glitch-2.mp3",
+        "assets/sfx/glitch-2-2.mp3",
+        "assets/sfx/glitch-2.mp3",
+      ]);
+    } finally {
+      globalThis.fetch = realFetch;
+    }
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+});
diff --git a/skills/media-use/audio/scripts/gemini-pipeline.test.mjs b/skills/media-use/audio/scripts/gemini-pipeline.test.mjs
index 8658807a89..842e5085e6 100644
--- a/skills/media-use/audio/scripts/gemini-pipeline.test.mjs
+++ b/skills/media-use/audio/scripts/gemini-pipeline.test.mjs
@@ -9,9 +9,15 @@ import { spawnSync } from "node:child_process";
 // external audio tools are fixtures. This is not a live synthesis/render test.
 for (const expired of [false, true]) {
   for (const only of ["tts", "tts,bgm,sfx"]) {
+    // With expired credentials the person already has an assets/voice/intro.wav, which the engine must keep.
+    const voicePath = expired ? "assets/voice/intro-2.wav" : "assets/voice/intro.wav";
     test(`Gemini engine returns caption metadata with ${expired ? "expired" : "absent"} HeyGen credentials (${only})`, (t) => {
       const dir = mkdtempSync(join(tmpdir(), "hf-gemini-pipeline-"));
       t.after(() => rmSync(dir, { recursive: true, force: true }));
+      if (expired) {
+        mkdirSync(join(dir, "assets/voice"), { recursive: true });
+        writeFileSync(join(dir, "assets/voice/intro.wav"), "the person's own intro");
+      }
       const config = join(dir, "heygen");
       mkdirSync(config);
       if (expired)
@@ -48,7 +54,7 @@ const assert = require('node:assert/strict');
 const fs = require('node:fs');
 const path = require('node:path');
 const args = process.argv.slice(2);
-assert.deepEqual(args.slice(0, 3), ['hyperframes', 'transcribe', 'assets/voice/intro.wav']);
+assert.deepEqual(args.slice(0, 3), ['hyperframes', 'transcribe', '${voicePath}']);
 assert.ok(fs.existsSync(args[2]));
 assert.equal(args[args.indexOf('--model')+1], 'small.en');
 fs.writeFileSync(path.join(args[args.indexOf('--dir')+1], 'transcript.json'), JSON.stringify([
@@ -99,7 +105,7 @@ fs.writeFileSync(path.join(args[args.indexOf('--dir')+1], 'transcript.json'), JS
       assert.deepEqual(meta.voices, [
         {
           id: "intro",
-          path: "assets/voice/intro.wav",
+          path: voicePath,
           duration_s: 1.25,
           words: [
             { id: "w0", text: "Hello", start: 0.1, end: 0.4 },
@@ -113,8 +119,13 @@ fs.writeFileSync(path.join(args[args.indexOf('--dir')+1], 'transcript.json'), JS
         manifest
           .map((line) => JSON.parse(line))
           .map(({ path, type, source }) => [path, type, source]),
-        [["assets/voice/intro.wav", "voice", "generated"]],
+        [[voicePath, "voice", "generated"]],
       );
+      if (expired)
+        assert.equal(
+          readFileSync(join(dir, "assets/voice/intro.wav"), "utf8"),
+          "the person's own intro",
+        );
     });
   }
 }
diff --git a/skills/media-use/audio/scripts/lib/bgm.mjs b/skills/media-use/audio/scripts/lib/bgm.mjs
index 0e2cc5b545..d23c8c0b65 100644
--- a/skills/media-use/audio/scripts/lib/bgm.mjs
+++ b/skills/media-use/audio/scripts/lib/bgm.mjs
@@ -12,9 +12,10 @@
 // Missing/failed BGM never blocks a render.
 
 import { spawn, spawnSync } from "node:child_process";
-import { existsSync, mkdirSync, openSync, closeSync } from "node:fs";
+import { existsSync, mkdirSync, openSync, closeSync, rmSync } from "node:fs";
 import { join } from "node:path";
 import { downloadTo, searchSounds } from "./heygen.mjs";
+import { agentWritePath } from "./media-record.mjs";
 import { pythonInvocation } from "./python.mjs";
 
 const r3 = (x) => Number(x.toFixed(3));
@@ -45,12 +46,12 @@ function pipInstall(deps) {
 }
 
 // ── retrieval (HeyGen music library) ──────────────────────────────────────────
-export async function retrieveBgm({ query, headers, hyperframesDir, hasVoice }) {
+export async function retrieveBgm({ query, headers, hyperframesDir, hasVoice, anomalies }) {
   const q = query || "calm cinematic underscore";
   const results = await searchSounds(q, "music", headers, { limit: 5 });
   if (!results.length) return null;
   const top = results[0];
-  const rel = "assets/bgm/track.mp3";
+  const rel = agentWritePath(hyperframesDir, "assets/bgm/track.mp3", { anomalies });
   await downloadTo(top.audio_url, join(hyperframesDir, rel));
   return {
     path: rel,
@@ -113,8 +114,9 @@ export function generateBgmDetached({
   lyriaRecipe,
   seedSeconds = 28,
   hasVoice,
+  anomalies,
 }) {
-  const rel = "assets/bgm/track.wav";
+  const rel = agentWritePath(hyperframesDir, "assets/bgm/track.wav", { anomalies });
   const abs = join(hyperframesDir, rel);
   mkdirSync(join(hyperframesDir, "assets", "bgm"), { recursive: true });
   const log = join(hyperframesDir, "assets", "bgm", `bgm-${Date.now()}.log`);
@@ -141,6 +143,7 @@ export function generateBgmDetached({
       "--prompt",
       prompt,
     ]);
+    rmSync(abs, { force: true }); // wait-bgm takes any file here as the finished track
     const proc = spawn(cmd, args, { detached: true, stdio: ["ignore", fd, fd] });
     proc.unref();
     closeSync(fd);
@@ -159,6 +162,7 @@ export function generateBgmDetached({
     const loops = targetS > seedS ? Math.ceil(targetS / seedS) : 1;
     const script = musicgenScript({ prompt, abs, targetS, seedS });
     const { cmd, args } = pythonInvocation(["-c", script]);
+    rmSync(abs, { force: true });
     const proc = spawn(cmd, args, { detached: true, stdio: ["ignore", fd, fd] });
     proc.unref();
     closeSync(fd);
diff --git a/skills/media-use/audio/scripts/lib/bgm.test.mjs b/skills/media-use/audio/scripts/lib/bgm.test.mjs
index 46967605c7..a31f6e72c6 100644
--- a/skills/media-use/audio/scripts/lib/bgm.test.mjs
+++ b/skills/media-use/audio/scripts/lib/bgm.test.mjs
@@ -1,6 +1,15 @@
 import { test } from "node:test";
 import assert from "node:assert/strict";
-import { BGM_BED_VOLUME, BGM_SILENT_VOLUME, bgmDefaultVolume } from "./bgm.mjs";
+import { existsSync, mkdirSync, mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+import { appendRecord } from "../../../scripts/lib/manifest.mjs";
+import {
+  BGM_BED_VOLUME,
+  BGM_SILENT_VOLUME,
+  bgmDefaultVolume,
+  generateBgmDetached,
+} from "./bgm.mjs";
 
 // Regression: narrated pipelines used to ship BGM at 0.8 (≈ -2 dB), ~16 dB
 // hotter than a music bed under a voice should be. The default under narration
@@ -28,3 +37,38 @@ test("the narrated default is well below the voice (≈ 0 dBFS)", () => {
     `bed should sit ≥16 dB under the voice, got ${separation.toFixed(1)} dB`,
   );
 });
+
+test(
+  "generating music again clears the engine's old track, so waiting cannot mistake it for the new one",
+  { skip: process.platform === "win32" && "the fake python is a shell script" },
+  (t) => {
+    const dir = mkdtempSync(join(tmpdir(), "hf-bgm-"));
+    const path = process.env.PATH;
+    t.after(() => {
+      process.env.PATH = path;
+      rmSync(dir, { recursive: true, force: true });
+    });
+    mkdirSync(join(dir, "bin"));
+    for (const name of ["python3", "python"])
+      writeFileSync(join(dir, "bin", name), "#!/bin/sh\nexit 0\n", { mode: 0o755 });
+    process.env.PATH = `${join(dir, "bin")}:${path}`;
+    mkdirSync(join(dir, "assets/bgm"), { recursive: true });
+    writeFileSync(join(dir, "assets/bgm/track.wav"), "last run's track");
+    appendRecord(dir, {
+      id: "bgm_001",
+      type: "bgm",
+      path: "assets/bgm/track.wav",
+      source: "generated",
+    });
+
+    const gen = generateBgmDetached({
+      prompt: "calm",
+      durationS: 5,
+      hyperframesDir: dir,
+      anomalies: [],
+    });
+
+    assert.equal(gen.path, "assets/bgm/track.wav");
+    assert.equal(existsSync(join(dir, "assets/bgm/track.wav")), false);
+  },
+);
diff --git a/skills/media-use/audio/scripts/lib/media-record.mjs b/skills/media-use/audio/scripts/lib/media-record.mjs
index ed94a691db..bbc2f91888 100644
--- a/skills/media-use/audio/scripts/lib/media-record.mjs
+++ b/skills/media-use/audio/scripts/lib/media-record.mjs
@@ -1,6 +1,48 @@
-import { recordInPlace } from "../../../scripts/lib/manifest.mjs";
+import { existsSync } from "node:fs";
+import { extname, join } from "node:path";
+import { AGENT_SOURCES, latestRecordFor, recordInPlace } from "../../../scripts/lib/manifest.mjs";
 import { regenerateIndex } from "../../../scripts/lib/index-gen.mjs";
 
+/**
+ * Where the engine may write `rel`: there, unless another file of this run has `taken` it or the file there is
+ * the person's (not `reusable` and not recorded as agent-made). Then the first free `name-2.ext`, with an anomaly.
+ */
+export function agentWritePath(
+  hyperframesDir,
+  rel,
+  { anomalies, taken = new Set(), reusable = () => false },
+) {
+  const free = (path) =>
+    !taken.has(path) &&
+    (!existsSync(join(hyperframesDir, path)) ||
+      reusable(path) ||
+      AGENT_SOURCES.includes(latestRecordFor(hyperframesDir, path)?.source));
+  if (free(rel)) return rel;
+  const ext = extname(rel);
+  const stem = rel.slice(0, rel.length - ext.length);
+  let n = 2;
+  while (!free(`${stem}-${n}${ext}`)) n++;
+  const path = `${stem}-${n}${ext}`;
+  const why = taken.has(rel)
+    ? "another file of this run goes there"
+    : "the file there is yours (the media manifest does not record it as made by the engine)";
+  const note = `${rel}: kept, because ${why}; writing ${path} instead (audio_meta.json has the path used)`;
+  if (!anomalies.includes(note)) anomalies.push(note);
+  return path;
+}
+
+/** Each spoken line's file, picked before lines synthesize concurrently so two never land on one free name. */
+export function voicePaths(hyperframesDir, lines, anomalies) {
+  const taken = new Set();
+  const paths = new Map();
+  for (const line of lines.filter((l) => String(l.text ?? "").trim())) {
+    const rel = agentWritePath(hyperframesDir, `assets/voice/${line.id}.wav`, { anomalies, taken });
+    taken.add(rel);
+    paths.set(String(line.id), rel);
+  }
+  return paths;
+}
+
 const SFX_SOURCES = { heygen: "search", local: "bundled" };
 
 // The files one engine run wrote, each with how it was made, for the project's media manifest.
@@ -32,7 +74,6 @@ export function writtenAssets({ only, lines, voices, ttsProvider, bgm, bgmFields
   if (only.has("sfx")) {
     for (const cue of new Map(sfx.map((entry) => [entry.file, entry])).values()) {
       const source = SFX_SOURCES[cue.source];
-      if (!source) continue;
       const provider = source === "search" ? "heygen" : "bundled.sfx";
       assets.push({
         path: cue.file,
diff --git a/skills/media-use/audio/scripts/lib/media-record.test.mjs b/skills/media-use/audio/scripts/lib/media-record.test.mjs
index b6ef637267..0325fa9479 100644
--- a/skills/media-use/audio/scripts/lib/media-record.test.mjs
+++ b/skills/media-use/audio/scripts/lib/media-record.test.mjs
@@ -4,7 +4,7 @@ import { mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "nod
 import { join } from "node:path";
 import { tmpdir } from "node:os";
 import { findByPrompt, readManifest } from "../../../scripts/lib/manifest.mjs";
-import { recordInManifest, writtenAssets } from "./media-record.mjs";
+import { agentWritePath, recordInManifest, voicePaths, writtenAssets } from "./media-record.mjs";
 
 const noBgm = { bgm: null, bgmFields: { bgm_pending: false } };
 
@@ -98,7 +98,6 @@ test("music and sound effects are marked by where they came from", () => {
       { file: "assets/sfx/whoosh.mp3", name: "whoosh", source: "local" },
       { file: "assets/sfx/whoosh.mp3", name: "whoosh", source: "local" },
       { file: "assets/sfx/glass.mp3", name: "glass", source: "heygen" },
-      { file: "assets/sfx/pop.mp3", name: "pop", source: "project" },
     ],
   });
 
@@ -139,6 +138,59 @@ test("a file that cannot be recorded becomes an anomaly, not a failure", (t) =>
   assert.match(anomalies[0], /^assets\/voice\/01\.wav: not recorded in the media manifest/);
 });
 
+test("the engine writes over only its own files, else the next free name", (t) => {
+  const dir = project(t);
+  mkdirSync(join(dir, "assets/sfx"), { recursive: true });
+  const names = ["mine", "made", "adopted", "twice", "twice-2", "kept", "kept-2"];
+  for (const name of names) writeFileSync(join(dir, `assets/sfx/${name}.mp3`), name);
+  for (const path of ["assets/sfx/made.mp3", "assets/sfx/kept-2.mp3"])
+    recordInManifest(dir, [{ path, type: "sfx", source: "search" }]);
+  recordInManifest(dir, [{ path: "assets/sfx/adopted.mp3", type: "sfx", source: "existing" }]);
+  const anomalies = [];
+  const at = (name, reusable) =>
+    agentWritePath(dir, `assets/sfx/${name}.mp3`, { anomalies, reusable });
+
+  assert.equal(at("new"), "assets/sfx/new.mp3");
+  assert.equal(at("made"), "assets/sfx/made.mp3");
+  assert.equal(
+    at("mine", (path) => path === "assets/sfx/mine.mp3"),
+    "assets/sfx/mine.mp3",
+  );
+  assert.deepEqual(anomalies, []);
+  assert.equal(at("mine"), "assets/sfx/mine-2.mp3");
+  assert.equal(at("adopted"), "assets/sfx/adopted-2.mp3");
+  assert.equal(at("twice"), "assets/sfx/twice-3.mp3");
+  assert.equal(at("kept"), "assets/sfx/kept-2.mp3");
+  assert.equal(anomalies.length, 4);
+  assert.match(
+    anomalies[0],
+    /^assets\/sfx\/mine\.mp3: kept, .* writing assets\/sfx\/mine-2\.mp3 instead/,
+  );
+});
+
+test("two spoken lines never share a file when one's name is taken by the person", (t) => {
+  const dir = project(t);
+  mkdirSync(join(dir, "assets/voice"), { recursive: true });
+  writeFileSync(join(dir, "assets/voice/hook.wav"), "the person's own hook");
+  const anomalies = [];
+
+  const paths = voicePaths(
+    dir,
+    [
+      { id: "hook", text: "First" },
+      { id: "hook-2", text: "Second" },
+      { id: "blank", text: " " },
+    ],
+    anomalies,
+  );
+
+  assert.deepEqual(Object.fromEntries(paths), {
+    hook: "assets/voice/hook-2.wav",
+    "hook-2": "assets/voice/hook-2-2.wav",
+  });
+  assert.equal(anomalies.length, 2);
+});
+
 test("a record never takes the id of a download still in flight", (t) => {
   const dir = project(t);
   mkdirSync(join(dir, ".media/audio/bgm"), { recursive: true });
diff --git a/skills/media-use/audio/scripts/lib/sfx.mjs b/skills/media-use/audio/scripts/lib/sfx.mjs
index 7cc3487c34..7f746f149b 100644
--- a/skills/media-use/audio/scripts/lib/sfx.mjs
+++ b/skills/media-use/audio/scripts/lib/sfx.mjs
@@ -15,6 +15,8 @@
 import { copyFileSync, existsSync, mkdirSync, readFileSync } from "node:fs";
 import { join } from "node:path";
 import { downloadTo, searchSounds } from "./heygen.mjs";
+import { latestRecordFor } from "../../../scripts/lib/manifest.mjs";
+import { agentWritePath } from "./media-record.mjs";
 
 const SFX_VOLUME = 0.35;
 const slug = (s) =>
@@ -31,6 +33,8 @@ export async function resolveSfx({ cues, heygenOK, headers, hyperframesDir, sfxL
   const sfx = [];
   const anomalies = [];
   const destDir = join(hyperframesDir, "assets", "sfx");
+  // Each effect's file this run: one effect named twice gets one file, and two effects never share one.
+  const fileFor = new Map();
 
   // Dedupe identical (id,name) cues — the same effect named twice in one line
   // downloads/copies once.
@@ -57,8 +61,14 @@ export async function resolveSfx({ cues, heygenOK, headers, hyperframesDir, sfxL
           continue;
         }
         const top = results[0];
-        const file = `assets/sfx/${slug(name)}.mp3`;
+        const file =
+          fileFor.get(slug(name)) ??
+          agentWritePath(hyperframesDir, `assets/sfx/${slug(name)}.mp3`, {
+            anomalies,
+            taken: new Set(fileFor.values()),
+          });
         await downloadTo(top.audio_url, join(hyperframesDir, file));
+        fileFor.set(slug(name), file);
         sfx.push({
           id,
           name,
@@ -111,32 +121,41 @@ export async function resolveSfx({ cues, heygenOK, headers, hyperframesDir, sfxL
       continue;
     }
     const src = join(sfxLibDir, hit.file);
-    const destRel = `assets/sfx/${hit.file}`;
+    const library = existsSync(src) ? readFileSync(src) : null;
+    const isLibraryCopy = (rel) =>
+      library &&
+      existsSync(join(hyperframesDir, rel)) &&
+      readFileSync(join(hyperframesDir, rel)).equals(library);
+    const destRel =
+      fileFor.get(hit.file) ??
+      agentWritePath(hyperframesDir, `assets/sfx/${hit.file}`, {
+        anomalies,
+        taken: new Set(fileFor.values()),
+        // An unrecorded copy of the library file is one an engine run made before the manifest had it.
+        reusable: (rel) => !latestRecordFor(hyperframesDir, rel) && isLibraryCopy(rel),
+      });
     const dest = join(hyperframesDir, destRel);
     // The bundled library may be incomplete: some installs of the skill ship
     // manifest.json without the actual mp3s. Pushing an sfx entry that points at
     // a file we never copied produces a dangling reference that silently drops
     // downstream ("not on disk"). Surface it as a loud anomaly and skip the cue
     // instead, so the audio_meta never references a missing file.
-    const reused = existsSync(dest);
-    if (!reused) {
-      if (!existsSync(src)) {
-        anomalies.push(
-          `sfx "${name}" (id ${id}): bundled file ${hit.file} missing from the offline ` +
-            `library (${sfxLibDir}) — skipped. Reinstall the media-use skill to ` +
-            `restore assets/sfx/*.mp3, or configure a HeyGen credential for retrieval.`,
-        );
-        continue;
-      }
-      copyFileSync(src, dest);
-    }
-    // A file already there that is not the library's copy is the person's own.
-    const own = reused && !(existsSync(src) && readFileSync(dest).equals(readFileSync(src)));
+    if (library) {
+      if (!isLibraryCopy(destRel)) copyFileSync(src, dest);
+    } else if (!existsSync(dest)) {
+      anomalies.push(
+        `sfx "${name}" (id ${id}): bundled file ${hit.file} missing from the offline ` +
+          `library (${sfxLibDir}) — skipped. Reinstall the media-use skill to ` +
+          `restore assets/sfx/*.mp3, or configure a HeyGen credential for retrieval.`,
+      );
+      continue;
+    } // else the engine's earlier copy at dest stands in for the file this install lacks
+    fileFor.set(hit.file, destRel);
     sfx.push({
       id,
       name,
       file: destRel,
-      source: own ? "project" : "local",
+      source: "local",
       offset_s: 0,
       duration_s: r3(hit.duration),
       volume: SFX_VOLUME,
diff --git a/skills/media-use/audio/scripts/lib/sfx.test.mjs b/skills/media-use/audio/scripts/lib/sfx.test.mjs
index 3c89d58748..ef692962e1 100644
--- a/skills/media-use/audio/scripts/lib/sfx.test.mjs
+++ b/skills/media-use/audio/scripts/lib/sfx.test.mjs
@@ -1,8 +1,9 @@
 import { test } from "node:test";
 import assert from "node:assert/strict";
-import { mkdtempSync, mkdirSync, writeFileSync, existsSync, rmSync } from "node:fs";
+import { mkdtempSync, mkdirSync, writeFileSync, existsSync, readFileSync, rmSync } from "node:fs";
 import { join } from "node:path";
 import { tmpdir } from "node:os";
+import { appendRecord } from "../../../scripts/lib/manifest.mjs";
 import { resolveSfx } from "./sfx.mjs";
 
 // Offline (no HeyGen) SFX resolution: the bundled library may ship manifest.json
@@ -67,3 +68,54 @@ test("offline: a matched-but-missing bundled file yields an anomaly and NO dangl
     assert.ok(!existsSync(join(projDir, "assets/sfx/whoosh.mp3")), "nothing copied");
   });
 });
+
+const whooshLibrary = (libDir, withFile) => {
+  writeFileSync(
+    join(libDir, "manifest.json"),
+    JSON.stringify({ whoosh: { file: "whoosh.mp3", duration: 0.8 } }),
+  );
+  if (withFile) writeFileSync(join(libDir, "whoosh.mp3"), "ID3-library-bytes");
+};
+const record = (projDir, source) =>
+  appendRecord(projDir, { id: "sfx_001", type: "sfx", path: "assets/sfx/whoosh.mp3", source });
+const offline = (libDir, projDir) =>
+  resolveSfx({
+    cues: [{ id: "s1", name: "whoosh" }],
+    heygenOK: false,
+    hyperframesDir: projDir,
+    sfxLibDir: libDir,
+  });
+
+test("offline: the engine's earlier copy stands in for a library file this install lacks", async () => {
+  await withDirs(async ({ libDir, projDir }) => {
+    whooshLibrary(libDir, false);
+    mkdirSync(join(projDir, "assets/sfx"), { recursive: true });
+    writeFileSync(join(projDir, "assets/sfx/whoosh.mp3"), "engine copy");
+    record(projDir, "bundled");
+
+    const { sfx, anomalies } = await offline(libDir, projDir);
+
+    assert.deepEqual(
+      sfx.map(({ file }) => file),
+      ["assets/sfx/whoosh.mp3"],
+    );
+    assert.deepEqual(anomalies, []);
+  });
+});
+
+test("offline: a person's file with the library's bytes stays theirs once recorded as their own", async () => {
+  await withDirs(async ({ libDir, projDir }) => {
+    whooshLibrary(libDir, true);
+    mkdirSync(join(projDir, "assets/sfx"), { recursive: true });
+    writeFileSync(join(projDir, "assets/sfx/whoosh.mp3"), "ID3-library-bytes");
+    record(projDir, "existing");
+
+    const { sfx } = await offline(libDir, projDir);
+
+    assert.deepEqual(
+      sfx.map(({ file }) => file),
+      ["assets/sfx/whoosh-2.mp3"],
+    );
+    assert.equal(readFileSync(join(projDir, "assets/sfx/whoosh.mp3"), "utf8"), "ID3-library-bytes");
+  });
+});
diff --git a/skills/media-use/scripts/lib/manifest.mjs b/skills/media-use/scripts/lib/manifest.mjs
index 56b533aaa3..49e387690f 100644
--- a/skills/media-use/scripts/lib/manifest.mjs
+++ b/skills/media-use/scripts/lib/manifest.mjs
@@ -79,6 +79,9 @@ export function appendRecord(projectDir, record) {
   appendFileSync(p, line);
 }
 
+/** Sources that mean the agent made or fetched the file; any other file is the person's own. */
+export const AGENT_SOURCES = ["generated", "search", "bundled"];
+
 /** The record a path has now: the manifest only appends, so the last one for a path wins. */
 export function latestRecordFor(projectDir, path) {
   return readManifest(projectDir).findLast((record) => record.path === path);