MCP error: "Incompatible auth server: does not support dynamic client registration"
Error: Incompatible auth server: does not support dynamic client registration
What causes it
Most MCP clients register themselves with the server on the fly (OAuth dynamic client registration). GitHub and Slack do not offer a registration endpoint, so the client has no client ID to use and stops.
How to fix it
- Use a token if the server accepts one. GitHub does: create a fine-grained personal access token and send it as an Authorization: Bearer header. That worked for us on Oct 16, 2026.
- Or register your own OAuth app with the vendor and give its client ID (and secret) to your client. For Slack, create an internal Slack app and turn on "Enable Slack MCP Server" in its Agents settings. That worked for us on Oct 16, 2026.
- In Claude Code, pass --client-id and --client-secret to claude mcp add. Some versions still try dynamic registration first (see anthropics/claude-code issue 38102).
Where we hit it
- GitHub MCP test report (tested Oct 16, 2026). Setup: Claude, Claude Code, Cursor, VS Code, ChatGPT
- Slack MCP test report (tested Oct 16, 2026). Setup: Claude, Claude Code, Cursor, VS Code, ChatGPT
Related fixes
- MCP Inspector keeps failing after a bad OAuth attempt
- GitHub MCP issue_write shows a form and creates nothing
- MCP error -32601 Method not found on resources/list
- Slack MCP search fails: needs keywords and natural_language_query
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