xAI's refresh-token response sometimes omits expires_in. Without it the
new access token kept the stale pre-refresh expires_at, so is_valid /
--check forever rejected a fresh token — and the refresh loop re-rotated
the single-use refresh token every tick, killing the credential (F006).
The access token is a JWT whose exp is the authoritative expiry: decode it
when expires_in is absent. Fallback to the documented ~6h TTL + a structlog
warning when the JWT exp is unreadable, so a fresh token is treated as live
instead of stale.
Renn F
ba5ac385ed