Fast Refresh

The watch runtime opens a WebSocket back to Metro and applies HMR updates in-place — your component tree updates without losing state.

How it's wired:

• Metro emits HMR updates over WebSocket.
• The watch RNWWebSocket client subscribes.
• Updates are routed into the JS runtime via JSI.

If Fast Refresh stops working, common culprits:

• The watch lost its WebSocket connection (suspend / network change).
• Metro is serving from a path the watch isn't subscribed to (see the workspace bundle-path note in Metro & platform resolution).