mcp_token_exchange_failed against OAuth 2.1 + Cognito stack on claude.ai web; same stack works via Claude Code CLI

What this error means

mcp_token_exchange_failed against OAuth 2.1 + Cognito stack is a Claude Code failure pattern reported for developers trying to fix claude code oauth 2.1 + aws cognito token exchange failure for mcp server connections. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub Issue #309 (anthropics/claude-ai-mcp, 2026-05-18): User reports mcp_token_exchange_failed when using OAuth 2.1 + Cognito authentication stack on claude.ai web, while the identical stack works via Claude Code CLI. Indicates an inconsistency between web and CLI MCP auth flows. Maps to AI Coding Tools category as it concerns Claude Code’s MCP server connectivity.

Common causes

• GitHub Issue #309 (anthropics/claude-ai-mcp, 2026-05-18): User reports mcp_token_exchange_failed when using OAuth 2.1 + Cognito authentication stack on claude.ai web, while the identical stack works via Claude Code CLI. Indicates an inconsistency between web and CLI MCP auth flows. Maps to AI Coding Tools category as it concerns Claude Code’s MCP server connectivity.

Quick fixes

1. Confirm the exact error signature matches mcp_token_exchange_failed against OAuth 2.1 + Cognito stack.
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-ai-mcp/issues/309

Evidence note: GitHub Issue #309 (anthropics/claude-ai-mcp, 2026-05-18): User reports mcp_token_exchange_failed when using OAuth 2.1 + Cognito authentication stack on claude.ai web, while the identical stack works via Claude Code CLI. Indicates an inconsistency between web and CLI MCP auth flows. Maps to AI Coding Tools category as it concerns Claude Code’s MCP server connectivity.

Related errors

• AI Coding Tools

FAQ

What should I check first?

Start with the exact mcp_token_exchange_failed against OAuth 2.1 + Cognito stack 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 mcp_token_exchange_failed against OAuth 2.1 + Cognito stack.