Claude Code / AI Coding Tools

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

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 Includes evidence for Claude Code troubleshooting demand.

Source-backed Last updated May 21, 2026 1 source Needs local verification

Category: AI Coding Tools
Error signature: SDK auth failed: Incompatible auth server
Quick fix: Verify the account session, API key, provider settings, and environment where the failing tool is running.
Updated: May 21, 2026
Verification status: Source-backed
Evidence: 1 public source URL

Before you change production

This page includes public source URLs in the imported troubleshooting record. Compare those references with your version and environment before applying changes.

Reproduce the smallest failing action and save non-secret logs before changing configuration.
Check versions for Claude Code, related SDKs, package managers, CI runners, and hosting providers.
Change one setting or dependency at a time, then rerun the same failing command or request.
Avoid destructive commands, credential rotation, billing changes, or security relaxations without a rollback plan.

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

Confirm the exact error signature matches SDK auth failed: Incompatible auth server.
Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
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

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

Diagnostic flow for this page

Match SDK auth failed: Incompatible auth server exactly before applying the quick fix.
Compare the failing environment with Claude Code versions, account scope, provider settings, and deployment context.
Check the listed common causes in order, starting with the cause that best matches your logs.
Use the evidence status below to decide whether to confirm against public sources or official documentation.
Apply one reversible change, rerun the smallest failing action, and keep rollback notes.

FAQ

What does SDK auth failed: Incompatible auth server mean in Claude Code?

SDK auth failed: Incompatible auth server indicates the workflow described by "Claude Code HTTP MCP Servers with OAuth Auth Failed — Incompatible Auth Server" failed in a AI Coding Tools context. Start by confirming the exact signature and the component that emitted it.

What should I check first for SDK auth failed: Incompatible auth server?

Check whether this cause matches your environment: 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.

Is the SDK auth failed: Incompatible auth server guidance source-backed?

The "Claude Code HTTP MCP Servers with OAuth Auth Failed — Incompatible Auth Server" page is labeled source-backed. It has 1 public source URL from github.com, so use that evidence status when deciding how much additional verification you need.

When should I avoid the quick fix for SDK auth failed: Incompatible auth server?

For "Claude Code HTTP MCP Servers with OAuth Auth Failed — Incompatible Auth Server", avoid applying "Verify the account session, API key, provider settings, and environment where the failing tool is running." when the error text differs, the affected version or provider is different, or the change would touch credentials, billing, DNS, production deploy settings, or irreversible data.

What should I collect before debugging SDK auth failed: Incompatible auth server?

For "Claude Code HTTP MCP Servers with OAuth Auth Failed — Incompatible Auth Server", collect the failing Claude Code command or request, non-secret configuration, versions, timestamps, request IDs when available, and the smallest reproduction that still triggers the signature.