Windows: split CLI auth reports success but credentials are not available to a fresh process

[QvxSphere]

Summary

On Windows, ACP CLI browser authentication completes successfully, but the resulting session is not retrievable by a fresh CLI process.

Environment

• OS: Windows
• ACP CLI: 1.0.31
• Authentication mode: documented non-streaming split flow

Reproduction

1. Run acp configure start --json.
2. Complete the returned URL's browser authorization.
3. Run acp configure complete --request-id <requestId> --json.
4. The completion command returns status: authenticated.
5. In separate new CLI processes, run:
   • acp agent list --json
   • acp agent whoami --json
   • acp policy list --json

Actual result

Each fresh authenticated command immediately returns NOT_AUTHENTICATED.

Diagnostics (non-secret)

• ACP config persists the owner identity.
• The official cross-keychain dependency selects Native Windows Credential Manager / DPAPI.
• Expected ACP Credential Manager records are absent after configure complete.
• No filesystem or permission error was observed.
• No plaintext token fallback was attempted.

Expected result

A successful configure complete should store credentials in the supported OS keychain such that fresh CLI processes can execute authenticated read-only commands.

Could you advise whether this is a known Windows issue and whether there is a supported fix or workaround?

[QvxSphere]

Additional diagnosis: the failure mechanism is reproducible below the ACP auth layer. NativeWindowsBackend / @napi-rs/keyring setPassword fails on this Windows host with PasswordSetError / Windows error code 8. ACP CLI 1.0.31 catches that failure, calls useBackend("file"), successfully stores credentials in that process-local fallback, and reports authentication success. However, backend selection is not persisted. A fresh CLI process auto-selects native-windows again and returns NOT_AUTHENTICATED.

The same behavior was reproduced under Node 24.18 and 24.19 x64 with the same Windows user/SID, USERPROFILE, ACP config path, and architecture. No credential values were inspected.

Suggested behavior: resolve/document the native Windows credential-store failure or fail closed when secure credential persistence fails, rather than reporting authenticated after a process-local fallback that subsequent processes cannot retrieve.