When api_key_hint from a 401 response doesn't match any pool entry
(common with OAuth tokens where runtime_api_key rotates), the pool
rotated without marking anything exhausted and handed back a fresh
selection. Because nothing was ever marked, the pool could never reach
the "no available entries" state — the caller retried the same dead
token forever (~6 attempts/sec), starving the event loop so /stop was
never processed; only killing the gateway ended it.
Rebased onto the identity-tracking rework that landed on main
(73c4b5a045): the single-entry escape from that commit already stops
the most common OAuth case, so this fix bounds the REMAINING gap —
multi-entry pools ping-ponging A->B->A with an unmatched hint. Cap
consecutive no-mark rotations at one full lap of the available
entries, then return None so the error surfaces / fallback activates.
Deliberately does NOT mark innocent entries exhausted (the original
PR's approach): that would quarantine a healthy key for the full
cooldown TTL on a hint that provably matches nothing. No cooldown is
written by the escape, so healthy keys stay available next turn --
bounded without hammering.
The streak resets when a rotation identifies a real entry and on any
successful normal select(), so only genuinely consecutive unmatched
rotations trip the bound.
Fixes#70401
Teknium
JonthanaHanh