matchu-patchu-mcp

An MCP (Model Context Protocol) server exposing matchu-patchu — the unified-diff patcher that's tolerant of form, strict about intent — as a patch tool over stdio.

Tool

patch(filePath, diff, dryRun?) — applies a unified diff to a file. Sloppy AI-generated diffs are repaired and applied atomically when the intent is unambiguous; ambiguous ones fail with a precise, typed error the calling model can act on in one step. dryRun: true reports what would change without writing.

Setup

claude mcp add --scope user patcher -- npx -y matchu-patchu-mcp@latest

(-y skips npx's first-run install prompt, which would otherwise hang the server spawn; @latest re-resolves against the registry at each session start, so new sessions pick up updates automatically.)

This works as-is on Windows — Claude Code spawns npx correctly there; no wrapper or global install needed.

Then restart Claude Code — MCP servers load at session startup, so the patch tool won't appear until a new session. Verify with claude mcp list: patcher should show as connected.

Or in any MCP client configuration:

{
  "mcpServers": {
    "patcher": { "command": "npx", "args": ["-y", "matchu-patchu-mcp@latest"] }
  }
}

See the matchu-patchu README for what the patcher tolerates, fuzz scores, and when to prefer it over exact string replacement.

Troubleshooting

npx matchu-patchu-mcp crashes with Cannot read properties of null (reading 'package') — this is an npm bug, not a package bug: npx scans the current project's node_modules before downloading anything, and that scan is known to crash in some pnpm workspaces (e.g. links whose target lives inside the same project tree). Work around it by installing globally and invoking the bin directly:

npm i -g matchu-patchu-mcp
claude mcp add --scope user patcher -- matchu-patchu-mcp

(This form pins to the globally installed version — rerun npm i -g matchu-patchu-mcp to update.)

Windows, MCP clients other than Claude Code — some clients can't spawn npx directly on Windows (it's a .cmd shim, not an .exe). Claude Code handles this itself, so the Setup command above needs no change; for a client that doesn't, wrap it — this keeps @latest auto-updates:

{
  "mcpServers": {
    "patcher": { "command": "cmd", "args": ["/c", "npx", "-y", "matchu-patchu-mcp@latest"] }
  }
}

(A global install also sidesteps this — "command": "matchu-patchu-mcp" works as-is — but pins the installed version; prefer the cmd /c wrapper.)

License

Apache-2.0. See LICENSE and NOTICE.