[BUG] Pro login loads 2.9M tokens in "System tools" — makes Claude Code unusable

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?

When logged in via Claude.ai Pro OAuth (/login → "Claude.ai Subscription"), Claude Code loads approximately 2.9M tokens into "System tools" on startup, making the context 1460% full before any user input.
Steps to reproduce:

Log out: rm ~/.claude/.credentials.json
Start claude in any project directory → /context shows ~721 tokens (normal)
Run /login → authenticate with Claude.ai Pro subscription
/context immediately shows 2.9M tokens in "System tools" (1460% full)

Environment:

Claude Code version: 2.1.133
Platform: Ubuntu 24.04 LTS, linux-x64
Model: claude-sonnet-4-6
Plan: Claude Pro
Interface: Terminal + VS Code extension

What Should Happen?

Expected behavior: System tools should load ~10-15k tokens (built-in tools only), regardless of login method.
Actual behavior: Pro OAuth login causes 2.9M tokens to load in "System tools". No MCP connectors are connected (verified in claude.ai → Settings → Connectors).

Error Messages/Logs

Steps to Reproduce

see description

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.133

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

OAuth token scopes include user:mcp_servers — this may be triggering automatic MCP server loading
Removing .credentials.json and using API key only resolves the issue
No MCP connectors visible in claude.ai settings