Notion MCP server: OAuth succeeds but server reconnection fails with 401
Using the hosted Notion MCP server (https://mcp.notion.com/mcp (opens external site)) with Claude Code 2.0.75 on macOS, OAuth completes and the browser shows successful authentication, but Claude Code reports 'Authentication successful, but server reconnection failed' and the MCP connection returns HTTP 401. The same happens in Cursor and Gemini CLI. Is this a client configuration problem or a server-side issue, and what fixed it?
Originally asked on GitHub: https://github.com/makenotion/notion-mcp-server/issues/167
4 answers
Fixed: a Notion maintainer confirmed the cause was a new server-side validation on https://mcp.notion.com/mcp (opens external site) that was incompatible with conventional MCP clients, and the change was reverted on December 21, 2025. One user then confirmed the hosted server connected successfully again. No client configuration fix is documented in the thread, so if you see this error again, check Notion's server status before reinstalling or reconfiguring your client.
The failure affected Claude Code 2.0.74 and 2.0.75, Cursor, and Gemini CLI. The typical log sequence was: OAuth completes, access and refresh tokens are returned, then the MCP HTTP transport fails with 'Server returned 401 after successful authentication (code: 401)'. Since even a completely fresh OAuth flow with no cached credentials produced the same 401, the problem was not stale tokens or client misconfiguration.
The following troubleshooting steps were tried and did not help: clearing authentication through the /mcp menu, removing and re-adding the server with
claude mcp remove notionandclaude mcp add --transport http notion https://mcp.notion.com/mcp, disconnecting the integration in Notion UI, deleting the Claude Code credential from the macOS Keychain withsecurity delete-generic-password -s "Claude Code-credentials", and trying all three connection methods in Gemini CLI. If you hit this issue again, you can skip those steps and wait for the server side to be fixed.Did this work for you?What @geopopos tried on GitHub (Didn't work)
Full credential reset on macOS: cleared auth via /mcp, revoked the Notion MCP connection in Notion UI, deleted the Claude Code credential from the Keychain with
security delete-generic-password -s "Claude Code-credentials", removed and re-added the server withclaude mcp add --transport http notion https://mcp.notion.com/mcp, then restarted and re-authenticated. Fresh OAuth still produced the same 401 error.Did this work for you?What a GitHub user tried on GitHub (Didn't work)
Restarted Claude Code and reinstalled both the plain MCP server and the plugin on a fresh install. Authentication still reported success followed by 'Authentication successful, but server reconnection failed'.
Source: https://github.com/makenotion/notion-mcp-server/issues/167 (opens external site)
Did this work for you?What @rucomcode tried on GitHub (Didn't work)
In Gemini CLI, tried all three connection methods from the Notion MCP getting-started documentation. Each attempt completed OAuth in the browser, then the server rejected the stored token and requested re-authentication.
Did this work for you?