previous attempt was wrong: the legacy branch returned port_hash
unconditionally, so two legacies hashing to the same port both
wrote that port and the collision persisted (test still trying to
bind coder's port).
new rule: always probe forward from port_hash, with scan_taken_ports
parameterised by include_implicit_hashes:
- legacy migration (applied dir exists, no port file): pass false.
scan only counts other agents' port files. first-queried legacy
claims its hash; subsequent colliders see the first's port file
and probe forward. we don't know which legacy originally won
the bind race, so first-write-wins; the loser was already
crash-looping anyway and gets a fresh port to rebuild to.
- fresh spawn (no applied dir): pass true. counts port files AND
implicit hashes for not-yet-migrated legacies, so a new spawn
doesn't race with an unmigrated peer.
migration note for affected users: agents whose port file says
something other than their hashed port may have been corrupted by
the previous fix. Hit ↻ R3BU1LD on the offender to regenerate the
flake (uses the current port file) and the container will bind
the right port on restart.
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