Auto-update at boot invalidates session, forces relogin

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) and this hasn't been reported yet
- [x] This is a single bug report (please file separate reports for different bugs)
- [x] I am using the latest version of Claude Code

### What's Wrong?

- Version: 2.1.235 → auto-updated to 2.1.237 at boot
- Symptom: session says "expired", forces /login, right after native auto-update runs at cold-start on Windows 11
- .credentials.json refreshToken still valid (not actually expired) — update process itself invalidates session, not token expiry
- .last-update-result.json timestamp matches failure time
- OS: Windows 11, native install, domain-joined machine

### What Should Happen?

Session should survive native auto-update. Refresh token isn't actually expired — relogin shouldn't be needed after an update completes.

### Error Messages/Logs

```shell
.last-update-result.json:
{"timestamp":"2026-08-20T03:58:42.322Z","path":"native","outcome":"success","status":"success","version_from":"2.1.235","version_to":"2.1.237","error_code":null}

CLI message on launch: "Please run /login" (session expired)
```

### Steps to Reproduce

1. Have Claude Code running, close laptop / shutdown
2. Reboot, open terminal, run claude
3. CLI auto-updates itself in background (check .claude/.last-update-result.json for timestamp)
4. Session immediately shows "expired", prompts /login
5. Manually /login — works fine, valid until next reboot+update cycle

### Claude Model

Not sure / Multiple models

### Is this a regression?

No, this never worked

### Last Working Version

_No response_

### Claude Code Version

2.1.237

### Platform

Anthropic API

### Operating System

Windows

### Terminal/Shell

PowerShell

### Additional Information

Machine is domain-joined (Windows 11). Config backup at ~/.claude/backups/.claude.json.backup shrank in size right after the failing update (79KB → 76KB), suggesting the update process partially resets local config/session state, not just the token.

Fast Startup (hiberboot) enabled — ruled out as cause (cold boot vs hybrid boot both trigger the issue).
Verified refreshToken in .credentials.json is NOT expired at time of failure — expiresAt several days out.

Start by comparing .last-update-result.json, .credentials.json, and the ~/.claude/backups/.claude.json.backup state before and after the native update. Trace the boot-time update and session-loading path in the repository, then reproduce on Windows 11 with the listed version transition. Done means a valid refresh token remains usable after a native auto-update and reboot without requiring /login.

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