## Why
App-server logs can be persisted or included in submitted diagnostics, so credentials used by model providers, authentication refreshes, and attestation requests must not appear in diagnostic output.
## What changed
- Add `RedactedString`, which preserves serialization and string access while replacing debug output with `<redacted>`.
- Use it for model-provider bearer tokens, header and query values, authentication command arguments, and attestation tokens.
- Avoid logging JSON-RPC error payloads and parser or authentication errors that may echo credentials; retain safe context such as error codes and categories.
## Testing
- Add an app-server regression test that exercises provider credentials, refreshed authentication tokens, and attestation tokens, then verifies none appear in persisted SQLite or submitted diagnostic logs.
GitOrigin-RevId: 8c50408adf94d93847658b1320682cf3b637d2cc
## Summary
External auth had two paths: provider-command credentials were resolved
through `ExternalAuth`, while app-provided ChatGPT credentials were
installed separately and only used the provider for refresh.
`ExternalAuth` also declared an auth mode independently from the
`CodexAuth` value it returned, so the declaration and credentials could
disagree.
This change makes the provider-owned `CodexAuth` authoritative for
initial resolution, credential kind, and refresh.
- remove `ExternalAuth::auth_mode` and require providers to return their
current auth from `resolve`
- route external auth registration, resolution, and unauthorized refresh
through `AuthManager::set_external_auth`
- keep the last resolved credential with its provider so synchronous
consumers and unauthorized recovery observe the credential's actual mode
- make the app-server bridge own both initial and refreshed ChatGPT
credentials, and detach it on logout
- keep model listing free of auth-refresh side effects, including in
offline mode
Provider-command auth still follows its configured cache interval.
App-provided ChatGPT auth still asks the parent app once after a `401`
and retries the request once.
Stacked on #31355.
## Testing
- `just test -p codex-login`
- `just test -p codex-models-manager`
- focused `codex-app-server` tests for external login/logout,
unauthorized refresh, and workspace mismatch
andrewgu-oai