Field-safe SERVER net. A device opening duplicate/rapid sockets (the APK duplicate-socket bug,
separate track) currently churns through evictions during the reconnect-throttle's 30s
post-restart WARM-UP (only the hard ceiling 20 applies then, so an 8-in-9s burst passes
undamped and each new socket evicts the prior). This makes the server absorb it: a thrashing
PAIRED device converges to ONE stable connection and stays online.
- lib/session-settle.js (decision only; bounded, swept): shouldHold(deviceId, incumbentAlive)
— true only when a socket was accepted for this device within SESSION_SETTLE_WINDOW_MS
(config, default 2500ms) AND the incumbent is alive. Warm-up-independent.
- deviceSocket register gate (just before evictPriorSocket): if a LIVE incumbent exists and
we're inside the window, SOFT-REFUSE the new socket (device:throttled reason=session_settle
+ disconnect) and keep the incumbent; else accept + evict + (re)arm the window.
- LIVENESS SAFEGUARD (load-bearing): only hold when the incumbent socket is actually in the
/device namespace — a dead/half-open incumbent is replaced, NEVER stranding the device (max
hold is the 2.5s window from the incumbent's accept, then any new socket is accepted).
- Soft refusal, NEVER a quarantine (reuses patch1's paired-safe philosophy); single-session
enforcement intact for a legitimate move; unpaired/abusive flapping still caught by the
existing limiters. O(1), no loop impact.
Tests (liveness first-class): live incumbent holds + DEAD incumbent replaced (not stranded);
storm of 6 sockets converges to ONE, stays online, not quarantined (during warm-up); single-
session move past the window replaces cleanly; unit decision + bounded sweep. The
evicted-socket-rearm test shrinks its settle window so it still exercises the eviction path.
Suite 336/336.
