diff --git a/README.md b/README.md
index 49aef86..db6f24f 100644
--- a/README.md
+++ b/README.md
@@ -12,9 +12,10 @@ It is one static page. Serve the folder and open it:
 
     python3 -m http.server 8794 && open http://127.0.0.1:8794/
 
-It talks to the factory's inference worker at `https://inference.yolopreneur.lol` (allowed origins include
-localhost? no: only `*.yolopreneur.lol` and `gandora.lol`; for local work add your Venice key with `/?key` or run
-from a `*.yolopreneur.lol` host). Everything the listener makes lives in their browser (IndexedDB) — see STORAGE.md.
+It talks to the factory's inference worker at `https://inference.yolopreneur.lol`, which only answers pages served
+from `*.yolopreneur.lol` or `gandora.lol`. For local work either add a personal Venice key (open `/?key` to show the
+key box) or test with `tools/harness.sh`, which stubs the backend. Everything the listener makes lives in their
+browser (IndexedDB) — see STORAGE.md.
 
 ## Files
 
@@ -23,7 +24,7 @@ from a `*.yolopreneur.lol` host). Everything the listener makes lives in their b
 - `sw.js` — service worker: caches the shell; stamped with the commit by the shots workflow.
 - `manifest.json`, `icons/`, `favicon.svg` — PWA. Icons are drawn by `tools/icons.py` (stdlib only).
 - `tools/shots.sh` — the card image and the icons, run by `.gitea/workflows/shots.yml` on every push.
-- `tools/harness.html` — the playback regression harness (see ARCHITECTURE.md › Testing).
+- `tools/harness.sh` + `tools/harness.html` — the playback regression harness (ARCHITECTURE.md › Testing).
 - `STORAGE.md` — the IndexedDB contract. `ARCHITECTURE.md` — how it all fits. `HANDOFF.md` — read before changing things.
 
 ## Backend
diff --git a/tools/harness.html b/tools/harness.html
index 1ef9280..6c8128a 100644
--- a/tools/harness.html
+++ b/tools/harness.html
@@ -5,32 +5,30 @@
 <!-- harness -->
 <script>
 try {
-const MP3 = "data:audio/mpeg;base64,__MP3__";
-async function mp3blob() { const b = atob(MP3.split(",")[1]); const u = new Uint8Array(b.length); for (let i = 0; i < b.length; i++) u[i] = b.charCodeAt(i); return new Blob([u], { type: "audio/mpeg" }); }
 let renderDelay = 50, n = 0;
 venice = async function (path, body, { raw = false } = {}) {
   if (path.includes("chat")) return { choices: [{ message: { content: JSON.stringify({ title: "T" + (++n), tags: "lo-fi, piano, instrumental", lyrics: "[verse]\nla\n[chorus]\nlo", bpm: 80, key: "C major", energy: 0.4, seconds: 30, meter: "4/4", station: "Test FM", line: "hi" }) } }] };
-  if (path === "/render") { await new Promise((r) => setTimeout(r, renderDelay)); const b = await mp3blob(); return new Response(b, { headers: { "content-type": "audio/mpeg", "x-cost": "0.001", "x-renderer": "test" } }); }
+  if (path === "/render") { await new Promise((r) => setTimeout(r, renderDelay)); const b = wavBlob(new Int16Array(8000 * 2), 8000); return new Response(b, { headers: { "content-type": "audio/wav", "x-cost": "0.001", "x-renderer": "test" } }); }
   throw new Error("unexpected " + path);
 };
 const log = []; const dd = document.createElement("pre"); dd.id = "diag"; document.body.append(dd);
 const L = (m) => { log.push(m); dd.textContent = log.join("\n"); };
-const S = (tag) => L(tag + ": src=" + String(state.audio.src).slice(5, 14) + " paused=" + state.audio.paused + " playing=" + state.playing + " holding=" + !!state.holding + " cur=" + (state.current && state.current.spec.title) + " next=" + (state.nextJob && state.nextJob.spec.title) + " nextblob=" + !!(state.nextJob && state.nextJob.blob) + " crackle=" + crackle.on + " loop=" + state.audio.loop);
+const S = (tag) => L(tag + "\n    src=" + String(state.audio.src).slice(5, 14) + " paused=" + state.audio.paused + " playing=" + state.playing + " holding=" + !!state.holding + " cur=" + (state.current && state.current.spec.title) + " next=" + (state.nextJob && state.nextJob.spec.title) + " nextblob=" + !!(state.nextJob && state.nextJob.blob) + " crackle=" + crackle.on + " loop=" + state.audio.loop);
 window.addEventListener("error", (e) => L("ERR " + e.message + " @" + e.lineno));
 window.addEventListener("unhandledrejection", (e) => L("REJ " + (e.reason && (e.reason.stack || e.reason)).toString().slice(0, 200)));
 const sleep = (ms) => new Promise((r) => setTimeout(r, ms));
 const ended = () => { state.audio.dispatchEvent(new Event("ended")); };
 (async () => {
   document.dispatchEvent(new Event("keydown")); await sleep(300);
-  openStation("test seed"); await sleep(1500); S("after first         (expect cur=T1 playing, next=T2 cooked)");
-  ended(); await sleep(600); S("after ended         (expect cur=T2 playing, holding=false)");
-  renderDelay = 3000; state.nextJob = null; cookNext(); await sleep(300); S("slow cook started   (expect next cooking, nextblob=false)");
-  ended(); await sleep(600); S("ended, nothing ready (expect holding=true, loop=true)");
-  await sleep(3500); S("track landed        (expect holding=true, loop=false: queued behind the crackle)");
-  ended(); await sleep(600); S("crackle pass ended  (expect cur=next track playing, holding=false)");
-  renderDelay = 50; document.querySelector("#play").click(); await sleep(600); S("after pause         (expect paused, crackle=true)");
-  document.querySelector("#play").click(); await sleep(300); S("after resume        (expect playing, crackle=false)");
-  document.querySelector("#skip").click(); await sleep(1500); S("after skip          (expect a new cur)");
+  openStation("test seed"); await sleep(1500); S("after first          expect cur=T1 playing, next=T2 nextblob=true");
+  ended(); await sleep(600); S("after ended          expect cur=T2 playing, holding=false");
+  renderDelay = 3000; state.nextJob = null; cookNext(); await sleep(300); S("slow cook started    expect next cooking, nextblob=false");
+  ended(); await sleep(600); S("ended, nothing ready expect holding=true loop=true");
+  await sleep(3500); S("track landed         expect holding=true loop=false (queued behind the crackle)");
+  ended(); await sleep(600); S("crackle pass ended   expect cur=that track playing, holding=false");
+  renderDelay = 50; document.querySelector("#play").click(); await sleep(600); S("after pause          expect paused=true crackle=true");
+  document.querySelector("#play").click(); await sleep(300); S("after resume         expect paused=false crackle=false");
+  document.querySelector("#skip").click(); await sleep(1500); S("after skip           expect a new cur");
   L("END");
 })();
 } catch (e) { const p = document.createElement("pre"); p.id = "diag"; p.textContent = "TOPERR " + e.message; document.body.append(p); }
diff --git a/tools/harness.sh b/tools/harness.sh
index 0e5659e..8f7736c 100644
--- a/tools/harness.sh
+++ b/tools/harness.sh
@@ -1,5 +1,5 @@
 #!/bin/sh
-# tools/harness.sh: the playback regression run. Builds tools/harness.html's page from index.html, runs it in headless
+# tools/harness.sh: the playback regression run. Appends tools/harness.html's script to index.html, runs it in headless
 # Chrome with autoplay allowed, prints one state line per step. Needs Chrome/Chromium and python3.
 set -eu
 cd "$(dirname "$0")/.."
@@ -15,12 +15,10 @@ out = pathlib.Path(sys.argv[1])
 page = pathlib.Path("index.html").read_text()
 h = pathlib.Path("tools/harness.html").read_text()
 script = h[h.index("<!-- harness -->"):]
-mp3 = pathlib.Path("tools/harness.mp3").read_bytes() if pathlib.Path("tools/harness.mp3").exists() else b""
-import base64
-script = script.replace("__MP3__", base64.b64encode(mp3).decode())
 (out / "run.html").write_text(page.replace("</body>", script + "</body>"))
 EOF
-"$CHROME" --headless=new --disable-gpu --autoplay-policy=no-user-gesture-required --virtual-time-budget=25000 --dump-dom "file://$out/run.html" 2>/dev/null > "$out/dom.html" || true
+# shellcheck disable=SC2086
+"$CHROME" --headless=new --disable-gpu --autoplay-policy=no-user-gesture-required --virtual-time-budget=25000 ${CHROME_FLAGS:-} --dump-dom "file://$out/run.html" 2>/dev/null > "$out/dom.html" || true
 python3 - "$out/dom.html" <<'EOF'
 import sys, re, html
 s = open(sys.argv[1]).read()