apply-patch

Apply a unified diff / patch to files — for an agent that has diff text (from a PR, git format-patch, or generated by an LLM) and needs to land it, without shell gymnastics. Tolerant of line-offset drift: it matches each hunk by its surrounding context, not just the stated line number.

apply_patch({ diff: "<unified diff>", dry_run: true })   // validate first
→ { ok: true, files: [ { path: "src/api.ts", action: "modified", hunks: 2 } ] }

Why

Edit is for hand-written edits; there was no clean way to apply an external diff. This closes that — and completes the edit-safety story: checkpoint → apply_patch → verify (and restore if verify fails).

The tool

apply_patch(diff, root?, dry_run?) — applies a unified diff. Handles modify / create (--- /dev/null) / delete (+++ /dev/null) across multiple files. Returns per-file { path, ok, action, hunks, error? }.

• Context matching — if the file has drifted from the diff's line numbers, it searches outward from the expected position for the matching context block.
• Per-file safety — a file whose hunk doesn't match is reported as failed and left unchanged (no half-applied file).
• dry_run: true — validate every hunk without writing.

Setup

npm install
npm test

claude mcp add apply-patch -e APPLY_PATCH_ROOT=/path/to/project -- node /abs/path/apply-patch/dist/server.js
# CLI: agent-patch change.diff   |   git diff | agent-patch --dry-run

Honest limits

• Standard unified-diff format (---/+++/@@); git-extended metadata lines are ignored. Renames-as-metadata aren't specially handled (delete+create works).
• Created files don't get a guaranteed trailing newline (the \ No newline marker is ignored).
• Context matching is exact-line within the search window — it won't apply against already-modified content (use verify after, checkpoint before).