Startup warm-up, opening the switcher and the refresh button can all probe at
once, and a relay host working through tunnel retries takes an order of
magnitude longer than a loopback one — so a slow older run landed last and
replaced a fresh "ok" with its own stale "unreachable". Each host now records
which run owns its status; a status from the switch flow outranks any probe
still running for it.
Each relay attempt is also capped by what is left of the 15s budget rather than
the full per-request timeout, so an attempt started just under the deadline can
no longer run the whole 8s past it.
The switcher held reachability in component state and replaced the whole map at
the end of a probe run. It ran once per open before the config had loaded — with
Local as the only host — so that pass wiped every other instance's status and
each open started on "Checking", including for the instance the app was
connected to and actively talking to.
Statuses move to their own module: startup warms them so the switcher opens on
real values, a re-probe replaces each value in place as it lands rather than
blanking them first, and stale entries are dropped against the loaded config
instead of a partial host list. The connected instance never reads "Checking" —
the live connection already answers what the probe would ask.
Bohdan Triapitsyn