argent-metro-debugger
1. Prerequisites
For React Native (iOS / Android): requires Metro dev server running (default localhost:8081) and a React Native app connected to Metro (at least one CDP target). Verify via debugger-status.
For Vega (Fire TV): requires a Debug .vpkg (a Release build never attaches) and Metro reachable from the device (vega device start-port-forwarding --port 8081 --forward false). Verify via debugger-status. debugger-component-tree, debugger-inspect-element, debugger-reload-metro and the react-profiler-* / profiler-* tools are unavailable there — see the argent-tv-interact skill.
For Chromium (CDP): requires a Chromium/CDP app already available — an Electron app booted via boot-device with electronAppPath, or any Chromium browser exposing a CDP port (auto-discovered by list-devices on 9222 / ARGENT_CHROMIUM_PORTS). The debugger re-uses the page CDP session — port is ignored, device_id is the chromium-cdp-<port> value from list-devices / boot-device. Only debugger-connect, debugger-status, debugger-evaluate, debugger-log-registry, view-network-logs, and view-network-request-details work on Chromium (the latter two read the browser's native CDP Network recording for the active tab instead of the Metro-injected fetch interceptor); debugger-component-tree, debugger-reload-metro, debugger-inspect-element, and the react-profiler-* / profiler-* tools are RN-only and reject Chromium at the capability gate with Tool 'X' is not supported on chromium app.
Android: reverse port for Metro
Android emulators and physical devices do not resolve the host's localhost by default. Before the RN app can reach Metro, forward port 8081 (or whichever port Metro is on) from the device back to the host:
adb -s <serial> reverse tcp:8081 tcp:8081
<serial> is the Android serial from list-devices. Once reversed, the app on the device connects to Metro just like an iOS simulator does, and all debugger-* / network-* / react-profiler-* tools work unchanged. If the device restarts or adb drops, re-run the command. A failing Metro connection on Android almost always means adb reverse has not been done or has been lost.