After ~3 refreshes, the dashboard would hang on "Initializing dashboard..."
with all /api/* fetches stalling. Root cause: Chrome keeps HTTP/1.1 sockets
in its keep-alive pool across page navigations even after EventSource is
garbage-collected. Once 6 (the per-origin limit) are held, every new fetch
queues indefinitely and the app can't finish booting.
Fix, layered:
1. sse-bus.ts — pagehide/beforeunload listeners close all active channels
and send a sendBeacon to /api/events/disconnect so the server forces
the socket closed (socket.destroy) rather than waiting for the browser
to notice. Uses a sessionStorage clientId to correlate.
2. api.ts — createResilientEventSource (used by planning / mission / slice
stream endpoints) registers every handle in a module-level set and
closes them all on pagehide/beforeunload. sse-bus doesn't see these
streams, so it needs its own teardown.
3. sse.ts — server-side connection bookkeeping. Tracks managed SSE
connections by clientId, supports client-triggered disconnect via
POST /api/events/disconnect, stale-timer cleanup, and supersedes
older streams when a client reconnects.
4. server.ts — exposes /api/events/disconnect and /api/events/keepalive
under a dedicated 300 req/min rate limit.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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