Claude Code HTTP MCP Servers with OAuth Auth Failed — Incompatible Auth Server

What this error means

SDK auth failed: Incompatible auth server is a Claude Code failure pattern reported for developers trying to developer uses http-based mcp servers with oauth (e.g., slack mcp at mcp.slack.com) in claude code; dynamic client registration (rfc 7591) fails with incompatible auth server error. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Found on GitHub claude-code repository issues (#52638). HTTP MCP server OAuth integration specifically fails when Claude Code attempts RFC 7591 dynamic client registration. Different from token persistence bug (distinct candidate). Affects developers building MCP integrations with OAuth-enabled services. Category: AI Coding Tools per mapping rules.

Common causes

• Found on GitHub claude-code repository issues (#52638). HTTP MCP server OAuth integration specifically fails when Claude Code attempts RFC 7591 dynamic client registration. Different from token persistence bug (distinct candidate). Affects developers building MCP integrations with OAuth-enabled services. Category: AI Coding Tools per mapping rules.

Quick fixes

1. Confirm the exact error signature matches SDK auth failed: Incompatible auth server.
2. Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
3. Verify the account session, API key, provider settings, and environment where the failing tool is running.

Platform/tool-specific checks

• Verify the command, editor, extension, or API client that produced the error.
• Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
• Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. Keep the working fix documented for the team or deployment environment.

How to prevent it

• Keep provider/tool configuration documented.
• Record non-secret diagnostics such as tool version, provider name, model name, and command path.
• Add a lightweight check before CI or production workflows depend on the tool.

Sources checked

• https://github.com/anthropics/claude-code/issues/52638

Evidence note: Found on GitHub claude-code repository issues (#52638). HTTP MCP server OAuth integration specifically fails when Claude Code attempts RFC 7591 dynamic client registration. Different from token persistence bug (distinct candidate). Affects developers building MCP integrations with OAuth-enabled services. Category: AI Coding Tools per mapping rules.

Related errors

• AI Coding Tools

FAQ

What should I check first?

Start with the exact SDK auth failed: Incompatible auth server text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed Claude Code workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without SDK auth failed: Incompatible auth server.