Claude Code / AI Coding Tools

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

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 Includes evidence for Claude Code troubleshooting demand.

Source-backed Last updated May 16, 2026 1 source Needs local verification

Category: AI Coding Tools
Error signature: initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header
Quick fix: Compare the failing environment with a known working setup, then change one configuration value at a time.
Updated: May 16, 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

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

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.
Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
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

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 initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header 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 initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header mean in Claude Code?

initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header indicates the workflow described by "MCP Server 未拒绝 Header 与 Body 协议版本不匹配的初始化请求" 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 initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header?

Check whether this cause matches your environment: 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）。

Is the initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header guidance source-backed?

The "MCP Server 未拒绝 Header 与 Body 协议版本不匹配的初始化请求" 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 initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header?

For "MCP Server 未拒绝 Header 与 Body 协议版本不匹配的初始化请求", avoid applying "Compare the failing environment with a known working setup, then change one configuration value at a time." 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 initialize request accepted despite MISMATCHED MCP-Protocol-Version header vs body protocolVersion — server negotiates from JSON-RPC body, ignoring header?

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