MCP servers failed to connect - Claude Code

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Error text / 报错原文

MCP servers failed to connect
Invalid MCP configuration
SSE stream disconnected
TypeError: terminated

What it means

Claude Code started, but one or more MCP server processes or remote transports failed during discovery, authentication, schema validation, or streaming.

Most common causes

The MCP command works in an interactive shell but not in Claude Code environment
Invalid JSON or wrong schema in .mcp.json
Remote MCP OAuth token expired
SSE server timeout or reverse proxy buffering

Fastest fix

Run claude mcp list and identify the failing server
Temporarily disable the failing server and retry the task
Test the MCP command directly from the same terminal
Validate .mcp.json as strict JSON

Safe fix

Use absolute command paths for local MCP servers
Keep secrets in environment variables, not checked-in JSON
Set explicit timeouts for remote servers
Reduce tool count for large coding sessions

What not to do

Do not hardcode personal access tokens in shared configs
Do not enable every MCP server globally
Do not ignore stderr from local MCP processes

How to confirm the fix

Run the smallest reproducible command first, then retry the agent task only after authentication, quota, and tool discovery are stable.

claude mcp list
node --version
npx --version