Replace three separate real-time channels (per-terminal WS, SSE, HTTP poll)
with a single persistent multiplexed WebSocket at /mux.
Architecture:
- Browser ↔ MuxProvider owns one WS connection per tab (/mux)
- Terminal I/O, resize, open/close all flow over mux channels
- Session status patches delivered via a shared SSE relay:
mux server subscribes once to Next.js /api/events (SSE) and
broadcasts to all connected browser clients — no per-client polling
- Manual WS upgrade routing fixes ws library limitation with multiple
WebSocketServer instances on the same HTTP server
Remove:
- terminal-websocket.ts (legacy ttyd-based per-session server, port 14800)
- Per-terminal WebSocket connections from DirectTerminal
- Per-client 5 s HTTP polling for session patches
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>