The renderer pings each pool backend every 60s (`hermes:backend:touch` →
`touchPoolBackend` → updates `lastActiveAt`). The LRU eviction cap used a
keepalive-fresh window of 90s — only 1.5× the ping cadence — to decide
whether a backend was "plausibly still alive". One missed or delayed ping
pushed a live backend past the threshold and the cap-driven eviction killed
the active profile's backend mid-session, restarting the gateway and
re-minting runtime ids. On WSL2, where the renderer→Electron IPC roundtrips
through 9p, brief 9p hiccups commonly stretch a ping to seconds of observed
silence, producing the ~80–90s exit / ~2 min cycle reported in #95189
(122 gateway starts on 2026-08-26 alone, driving renderer OOM via reconnect
churn at ~5GB/day).
Widen POOL_KEEPALIVE_FRESH_MS to 4 minutes (3× ping cadence + IPC stall
headroom, still bounded well below POOL_IDLE_MS=10min). Backends with one or
even two missed pings are now spared; truly idle backends (multiple lapses,
minutes idle) remain eligible for eviction by the cap and the idle reaper.
The constant is also overridable via HERMES_DESKTOP_POOL_KEEPALIVE_FRESH_MS
to make this tunable without a rebuild.
Finn763
00988f3b89