MCP Server 未拒绝 Header 与 Body 协议版本不匹配的初始化请求

What this error means

initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header is a Claude Code failure pattern reported for developers trying to 修复 mcp sdk 在 initialize 阶段同时接收 http header 和 body 中的 protocolversion 时，未能校验两者一致性的问题，避免 claude code/cursor 等工具因版本协商失败导致的连接异常. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

modelcontextprotocol/typescript-sdk #2108 报告：MCP v2025-11-25 规范下，server 接受 header 与 body 协议版本不一致的 initialize 请求而不报错，可能导致客户端与服务端使用错误的协议版本通信。复现于 v1.29.0（2026-05-16）。这直接影响 Claude Code 和 Cursor 等依赖 MCP 协议的 AI 编程工具。Category mapping: 属于 AI Coding Tools 范畴（Claude Code 通过 MCP 协议与外部服务交互时的鉴权/协商错误）。

Common causes

• modelcontextprotocol/typescript-sdk #2108 报告：MCP v2025-11-25 规范下，server 接受 header 与 body 协议版本不一致的 initialize 请求而不报错，可能导致客户端与服务端使用错误的协议版本通信。复现于 v1.29.0（2026-05-16）。这直接影响 Claude Code 和 Cursor 等依赖 MCP 协议的 AI 编程工具。Category mapping: 属于 AI Coding Tools 范畴（Claude Code 通过 MCP 协议与外部服务交互时的鉴权/协商错误）。

Quick fixes

1. Confirm the exact error signature matches initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header.
2. Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
3. Compare the failing environment with a known working setup, then change one configuration value at a time.

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/modelcontextprotocol/typescript-sdk/issues/2108

Evidence note: modelcontextprotocol/typescript-sdk #2108 报告：MCP v2025-11-25 规范下，server 接受 header 与 body 协议版本不一致的 initialize 请求而不报错，可能导致客户端与服务端使用错误的协议版本通信。复现于 v1.29.0（2026-05-16）。这直接影响 Claude Code 和 Cursor 等依赖 MCP 协议的 AI 编程工具。Category mapping: 属于 AI Coding Tools 范畴（Claude Code 通过 MCP 协议与外部服务交互时的鉴权/协商错误）。

Related errors

• AI Coding Tools

FAQ

What should I check first?

Start with the exact initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header 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 initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header.