[BUG] validation_failed on login + continuous OAuth 403 spam causes screen to go blank (Windows)

Preflight Checklist

• [x] I have searched existing issues 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?

After logging in (including after a fresh logout/re-login), a validation_failed toast appears briefly. From that point, the app continuously calls api.anthropic.com/api/oauth/claude_cli/client_data and api.anthropic.com/api/oauth/profile, receiving 403 responses every time:

OAuth token does not meet scope requirement user:profile

There is no backoff — it retries every few seconds for the entire session. Debug logs in ~/.claude/debug/ show 70-120+ of these errors per session, growing the longer the session runs. In my current session, the count went from 35 to 60+ within minutes.

During sessions with heavy file read/write operations, the screen eventually goes completely blank and requires killing and restarting the app. This started within the last week. Prior to that, equally large projects with the same workload had zero issues.

Latest version (no update available)
Windows 11 Pro
Fresh re-login did not fix the validation_failed or the 403 spam
System resources are fine (RAM/CPU well within normal range when crash occurs)

What Should Happen?

The OAuth login flow should grant all scopes the app requires. If the app needs user:profile, the login flow should request it.
If token validation fails, the app should re-prompt authentication — not silently proceed with a broken token.
A 403 response should not be retried indefinitely without backoff.
The renderer should never go blank regardless of background error volume.

Error Messages/Logs

=== ERROR SUMMARY — Session be485c9d ===

Total [ERROR] entries: 85

--- BREAKDOWN ---

1. OAuth 403 — client_data endpoint (no backoff, fires continuously):
   Count: 63
   Error: OAuth token does not meet scope requirement user:profile
   URL: https://api.anthropic.com/api/oauth/claude_cli/client_data
   Status: 403

2. OAuth 403 — profile endpoint:
   Count: 2
   Error: OAuth token does not meet scope requirement any_of(user:profile, user:office)
   URL: https://api.anthropic.com/api/oauth/profile
   Status: 403

3. Missing managed-settings.json:
   Count: 2
   Error: ENOENT: no such file or directory, open C:\ProgramData\ClaudeCode\managed-settings.json

--- TIMELINE ---
First OAuth error: 2026-02-28T20:22:32.398Z
Last OAuth error:  2026-02-28T20:59:24.965Z
Duration: ~37 minutes of continuous 403 spam

--- SAMPLE STACK TRACE ---
AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,
status=403, body=OAuth token does not meet scope requirement user:profile]
    at cu (B:/~BUN/root/claude.exe:92:1144)
    at <anonymous> (B:/~BUN/root/claude.exe:93:10067)
    at emit (node:events:92:22)
    at endReadableNT (internal:streams/readable:861:50)
    at processTicksAndRejections (native:7:39)
    at request (B:/~BUN/root/claude.exe:95:2149)

--- NOTES ---
- Fresh logout/re-login did not resolve. Same errors immediately after re-authentication.
- `validation_failed` toast appears on login.
- Screen goes blank during file I/O heavy sessions, requiring full app restart.
- Same workload on same machine had zero issues one week ago.
- Related: #29628 (same OAuth 403, different symptom)

Steps to Reproduce

Steps to Reproduce:

1. Open Claude Code on Windows 11
2. Log in (or log out and log back in — same result)
3. Observe validation_failed toast on login
4. Start any session with file read/write operations
5. Check debug log at ~/.claude/debug/ — OAuth 403 errors are already accumulating
6. Continue working — errors grow continuously with no backoff (63+ in 37 minutes)
7. During heavy file I/O, screen goes blank. App is unresponsive. Only fix is kill and restart.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.1.4498 Claude Code Desktop

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

Screenshot of the validation _Failed upon first log in

<img width="361" height="65" alt="Image" src="https://github.com/user-attachments/assets/9de60aa4-d0b8-4ff4-b25d-332733900471" />