## Why
Coordinated MCP OAuth refresh must stop retrying a definitively rejected refresh token, including after the runtime is rebuilt.
## What changed
Remove the rejected refresh token while preserving the access token and credential record. Compare stored credentials under the appropriate locks before writing so a replacement login is preserved, and update file entries using their existing keys.
Keep rejection handling alive through caller cancellation and prevent reuse within the runtime even if persistence fails. For ordinary direct-keyring credentials shared across `CODEX_HOME` directories, retire the token only in the current runtime because locking does not span those directories. Report persistence failures without exposing backend diagnostics.
## Testing
Add coverage for reauthentication after runtime rebuild, legacy file keys, cancellation with a concurrent credential replacement, keyring scope, and persistence failures with diagnostic redaction.
GitOrigin-RevId: a6e602ca2e2893ed711d853becc45142d9575fab
Matthew Zeng
4ae6016a93