[BUG] Notion OAuth connector fails with "Internal Server Error" on authorization step

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?

Bug Description

When trying to connect the Notion MCP connector on claude.ai/settings/connectors,
the OAuth flow fails with an "Internal Server Error" immediately after approving
access on Notion's authorization page (Step 3 of the OAuth flow).

What Should Happen?

Expected Behavior

After approving access on Notion's OAuth page, the connector should be
successfully linked and appear as "Connected" on the settings page.

Error Messages/Logs

## Actual Behavior

"Internal Server Error" is displayed after the OAuth redirect.
The connector is not established.

the link for error message is https://mcp.notion.com/callback?code=03d6a088-ca5d-408b-b202-4b545c8b5476&state=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

Steps to Reproduce

Steps to Reproduce

1. Go to https://claude.ai/settings/connectors
2. Click "Connect" on the Notion connector
3. The Notion OAuth page opens — select workspace and click "Allow access"
4. Redirected back to claude.ai — "Internal Server Error" is displayed
5. Connector remains unconnected

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

2.1.110

Claude Code Version

2.1.110

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

Additional Context

• This issue has persisted for 4–5 days (since approximately April 11, 2026)
• Tried multiple times, same result every time
• Notion workspace and account are working normally
• Notion API token is valid (tested separately, returns HTTP 200)