diffmate

English · 한국어

See what it looks like →

Leave private notes on a GitHub pull request diff, and have an AI agent answer them in place.

Nothing is posted to GitHub. Notes live on your machine only — nobody else sees them, even on the same PR.

On the page you also get a changed-files tree with each file's risk and note count, cards badged by kind (question / request / memo) and by whether they are answered, and ⌥J / ⌥K to jump between notes.

^{Rendered from the demo page with sample code — real reviews happen on private repositories.}

  ⓪ the agent fills in a one-line summary per file
        │
        ▼
  [GitHub PR · Files changed]   under each filename: why this file is worth looking at
        │  ① click the gutter button → write a question
        ▼
   [extension]  ──②──▶  local daemon  ──▶  ~/.diffmate/<owner>__<repo>/<pr>.json
        ▲                                      │ ▲
        │ ④ the answer appears in place        ▼ │ ③ ask your agent to answer
        └──────────────────────────  [AI agent] ─┘

  ①~④ repeat. Follow-ups stack on the same card.

Why

Reviewing AI-written code from a diff alone is hard: you cannot tell which file matters and why. Writing it up in the PR description does not help either — by the time you are reading code, that text is far above the fold.

So the explanation moves next to the diff. And the direction flips: instead of the agent pushing context, the person who does not know asks, and the one who knows answers. Only the reader knows what they are missing.

Install

git clone https://github.com/chaeeun037/diffmate.git
cd diffmate
npm start          # local daemon on 127.0.0.1:7777

Then in Chrome: chrome://extensions → enable Developer mode → Load unpacked → pick extension/.

Node 18+. No dependencies.

Update — git pull, then hit the reload button on diffmate in chrome://extensions.

Use

Leave a note — hover a diff line; a button appears left of the line number. Click and type.

• ⌘Enter to save, Esc to cancel
• Three kinds: question (answer only), request (change the code), memo (agent leaves it alone). Each card shows its kind, and questions and requests also show answered / unanswered
• Clicking the logo in a file's summary banner creates a file-level note that is not tied to any line
• ⌥J / ⌥K jump to the next / previous note (ignored while typing)

See the whole PR at once — a changed-files tree sits above the file list, with each file's risk (● high · ◐ mid · ○ low) and note count. Click a file to jump to it.

Get answers — ask your agent to answer the notes. It reads and writes through the CLI:

node cli/notes.mjs list                          # which PRs have unanswered notes
node cli/notes.mjs list <owner/repo> <pr>        # full notes as JSON
node cli/notes.mjs stale <owner/repo> <pr>       # which summaries a later commit made stale
echo 'answer'   | node cli/notes.mjs answer <owner/repo> <pr> <noteId>
echo 'follow-up'| node cli/notes.mjs reply  <owner/repo> <pr> <noteId>

Fill file summaries — right after opening a PR, so the reviewer sees them first:

echo '{
  "src/pages/_document.tsx": {
    "summary": "Inline beacon injected into every page. If the path check on the first line is wrong, every page fires the log.",
    "risk": "high", "order": 1
  }
}' | node cli/notes.mjs summarize <owner/repo> <pr>

How to write those summaries is a discipline of its own — see the skill below.

Use with Claude Code

A ready-made skill lives in this repo. Copy it where Claude Code looks for skills:

cp -r skill/diffmate ~/.claude/skills/        # English
cp -r skill/ko/diffmate ~/.claude/skills/     # Korean

Then set DIFFMATE to your checkout inside the skill, and ask your agent to "fill in the file summaries" after opening a PR, or "answer my notes" while reviewing.

Where notes live

~/.diffmate/
  <owner>__<repo>/
    <pr>.json

One file per PR, holding both the file summaries (files) and the notes (notes). A note is anchored by line number plus a hash of that line's content, so it follows the code when a new commit shifts it. When it cannot be found, it is not dropped — it surfaces as an "orphan note" at the top of the page.

Good to know

• Built for unified diff view. Split view is not handled yet.
• The script loads on any github.com page but stays idle until you reach a pull request's changes view — GitHub is a single-page app, so it cannot be injected on arrival.
• It rides on GitHub's Files changed DOM, so a redesign can break it. If buttons stop appearing, the [diffmate] console logs say where it lost track.
• A collapsed file (marked Viewed) has no diff lines on the page. Its notes are not hidden — they expand under the filename instead.
• Two tabs on the same PR: last write wins.

Docs

• Korean README
• Agent skill — how the agent writes summaries and answers
• Design notes — structure and the reasoning behind it (Korean)

AI use

This repo is developed with AI assistance (Claude Code), reviewed by the maintainer — most of the code, docs and commit messages started as drafts from an agent, and every change was read, tested and kept or rewritten by a person.

Contributions made with AI tools are welcome too. Please mention it in your pull request — an Assisted-by: trailer is the convention this repo follows — and make sure you can explain every line you submit.

License

MIT

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Issues in Korean or English are both welcome.