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mcp command fails on Windows: fileURLToPath returns POSIX path /C:/... causing C:\C:\ doubling #101
Description
Bug
expect mcp crashes on Windows with:
Error: Cannot find module 'C:\C:\Users\...\expect-cli\dist\browser-mcp.js'
Root cause
In dist/index.js, the mcp command spawns browser-mcp.js using:
let v = fileURLToPath(new URL('./browser-mcp.js', import.meta.url))
// then: execFileSync(process.execPath, [v], ...)On Windows, fileURLToPath returns a POSIX-style path /C:/Users/.../browser-mcp.js instead of C:\Users\...\browser-mcp.js. When this is passed as a CLI argument to node.exe, Windows interprets /C:/... relative to the current drive root, producing C:\C:\....
Repro
npm install -g expect-cli
echo '{"jsonrpc":"2.0","method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test","version":"1"}},"id":1}' | expect mcp
Environment
- OS: Windows 11
- Node.js: v22.22.2
- expect-cli: 0.1.3
- Shell: Git Bash (bash via MINGW64)
Fix suggestion
Wrap the path with a Windows path normalization before passing to execFileSync:
import { fileURLToPath } from 'node:url';
import path from 'node:path';
let v = path.resolve(fileURLToPath(new URL('./browser-mcp.js', import.meta.url)));path.resolve will normalize /C:/... → C:\... on Windows.
This blocks Claude Code MCP integration on Windows entirely — the MCP server can never start.
Activity
jiaweing commentedon Apr 22, 2026
Root cause identified
The bug is in
apps/cli/src/index.tsxline 254:.pathnamegives the raw URL path component — on Windows that's/C:/Users/..., not a valid Windows file path. Passing it tonode.exemakes Windows resolve it asC:\C:\....One-line fix
fileURLToPathis the standard Node.js way to convertimport.meta.urlto a file path — it correctly handles the Windows drive letter.I tried opening a PR but the repo is set to
collaborators_onlyfor PRs. Fork with the fix is at: https://github.com/jiaweing/expect/tree/fix/windows-mcp-path