The free-port probe bound without SO_REUSEADDR while the board's own
ThreadingHTTPServer sets it, so the socket a just-stopped board left in
TIME_WAIT read as "taken by something else": a routine stop/start walked
the board to the next port and wrote that over the user's BOARD_PORT pin.
The probe now binds exactly as the server does, which is the whole race.
Behind it, a held port gets a few seconds (BOARD_PORT_WAIT, 5s) to clear
before the walk, re-asking is_our_board each beat — a restart races its
own predecessor far more often than a stranger takes the port. Walking
off a pinned port still persists, since the hooks and agents read
BOARD_PORT and must reach the live board, but it now says so in full:
the right file (manager/local/.env, not manager/.env), old → new, and
how to reclaim the pin.
Tested end to end against a scratch host with a stub board.py, over real
sockets: a genuine TIME_WAIT remnant, a listener that lets go mid-wait,
a listener that does not, and our own board answering.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
