Follow-ups from review of #80590:
- oauth.py: extract _rotate_and_persist() — the twin ~18-line
OAuthRefreshError permanent/transient handling blocks in
ensure_fresh_token and force_refresh_token were byte-identical
except the log verb.
- oauth.py: cap the exchange cycle at _REFRESH_TOTAL_BUDGET_SECONDS
(20s). The retry runs while holding the global refresh locks on the
path to a memory call; a timed-out first attempt no longer earns a
second full 15s exchange (~32s lock hold -> <=20s).
- oauth.py: transient-failure cooldown (_refresh_failure_at, 30s).
Waiting threads and later turns fail open to the stale token instead
of serializing their own full exchange cycles against an endpoint
that just failed. Cleared on successful rotation and re-login.
- oauth.py: mtime-gate reauth_required()'s config read — the dead-grant
state persists until re-login, and the verdict can only change when
the config file is rewritten; drop the per-call read+parse.
- oauth.py: derive _TOKEN_VALUE_RE from ACCESS_TOKEN_PREFIX /
REFRESH_TOKEN_PREFIX so a prefix change can't silently break
redaction; promote redact_tokens to public (session.py imported the
private name).
- session.py: fast path in _reauth_required — skip config-path
resolution entirely while no grant is dead (runs before every SDK
call).
- session.py: client-generation counter closes the fetch/store race in
_sdk_session/_get_or_create_peer — an object resolved from the old
client mid-rebuild is no longer cached (it would 401 forever and burn
a token rotation per retry).
- __init__.py: drop the getattr/callable/except triple-guard in
_pop_auth_notice; the manager is always None or HonchoSessionManager.
7 new tests (budget, cooldown x3, generation guard, fast path); all
mutation-checked (disabling each guard fails its test). honcho_plugin
293 passed; plugins/memory 285 passed; live E2E against a real HTTP
token endpoint re-verified.
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