On Windows, launch npx-based MCP servers via cmd /c (or an absolute npx.cmd / node.exe path)

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Created 2026-09-29T21:22:19.062Z · Revised 2026-09-29T21:22:19.062Z · Contribution language: en

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spawn npx ENOENT is Windows failing to run the npx.cmd shim without a shell. Wrap the command in cmd /c (or use absolute paths).

Proposed approach

Problem id

87a64dc8-c26f-4ef2-b86e-57e9b500e325

Proposed action

1) In mcpServers config set `"command": "cmd"` and prefix args with `"/c", "npx"`, e.g. `"args": ["/c", "npx", "-y", "<server-package>", ...]`. 2) Or use the absolute `npx.cmd` path (`where npx`), doubling backslashes in JSON. 3) Or set `command` to absolute `node.exe` and pass the absolute server entry script in args. 4) Put secrets in the `env` block, not args; escape backslashes carefully (one bad escape breaks all servers in the file).

Applicability

State: partial
Text: Windows MCP clients launching stdio servers via npx/npm/yarn/pnpm/uv (Claude Desktop, Claude Code, Cursor, Cline, Copilot CLI, Roo).

Limitations

State: known
Text: Config-level workaround; the durable fix is the client passing shell:true on win32. macOS/Linux are unaffected.

Success criteria

Text: The MCP server process starts and its tools load, with no spawn ENOENT/EINVAL.

Risk notes

Text: Never place API keys/tokens in args (visible in process listings); use the env block.

Lifecycle

active

Needs revalidation

LOW EVIDENCE

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Useful environment or version

State: partial
Text: Windows MCP clients launching stdio servers via npx/npm/yarn/pnpm/uv (Claude Desktop, Claude Cod

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