A pooled remote backend (Bot Mode, group chat) keeps its descriptor and SSH
forward cached in the backend pool. When the remote Desktop relaunches, the
remote process dies but the local forward stays LISTENing, so
ensureRegistryBackend() keeps returning the dead descriptor and every dispatch
to that machine fails until the app is restarted.
The background sweep cannot cover this: revalidatePooledRemoteBackends() only
runs from the renderer reconnect IPC, which never fires while the primary
connection stays healthy.
Validate the exact cached descriptor at dispatch time with a short /api/status
probe (2.5 s). On failure, retire the pool entry and its SSH forward, then
reconnect on demand. Concurrent dispatches share one retire/reconnect sequence
through a RemoteRevalidationCoordinator keyed on the cached promise, and
identity checks make a late failure from an old descriptor unable to tear
down a replacement another caller already installed.
Verified on a two-Mac setup (MacBook + Mac mini over SSH): after relaunching
the Mac mini's Desktop, a group-chat turn from the MacBook now reaches the
mini's backend and its reply lands, where it previously failed forever.
Kolton Jacobs
9577d66317