The runtime call does not go over HTTP on Android — the WebView cannot deliver a fetch() POST body to shouldInterceptRequest, so v3 routes runtime calls through the addJavascriptInterface bridge. Two things follow that cost an hour each before the v3 source was read: `.playwright/init-events.js` does not transfer to the device (its outbound half hooks fetch, and a POST to /wails/runtime answers "missing object value" — which reads like a wrong payload and is the interceptor getting no body at all), and hooking fetch from an eval is too late on any platform because the bundle captured its reference at module scope. The recipe that does work goes in, along with how to get audio onto the phone (scoped storage silently swallows a push into /sdcard/Android/data/<pkg>/files, and the fixtures are 2 seconds long, which is useless for watching a seek bar) and the permission dialog a reinstall raises, which looks exactly like the app failing to start. NOTES.md takes the #53 measurements: that its frontend is byte-identical to the v0.3.1 the phone carries, that the symptom does not reproduce on main in four scenarios, and that reverting only backend/player/ to v0.3.1 reproduces #125 instead — with the shim that makes that a ten-minute experiment rather than a full checkout.