Review a git diff in your browser, comment on the lines, hand the feedback back.

diffpane opens a diff as a local web page, lets you click any line to leave a comment, and prints the feedback to whatever called it — markdown for a human, JSON for an agent. Nothing leaves your machine: no account, no service, no runtime dependencies.

Install

npm i -g diffpane

Or run it without installing: npx diffpane. Either way npm fetches a prebuilt binary; node is not needed at runtime.

Without node:

curl -LsSf https://github.com/thostetler/diffpane/releases/latest/download/diffpane-installer.sh | sh

From source:

git clone https://github.com/thostetler/diffpane
cd diffpane && cargo install --path .

Needs git. Prebuilt binaries cover macOS and Linux (glibc 2.31+) on x86_64 and arm64; building from source needs Rust 1.92+.

Use

From inside a repo:

diffpane                      # current branch vs its base
diffpane --working            # uncommitted changes
diffpane --staged             # staged changes
diffpane --range main..feat   # an explicit range
diffpane --commit a1b2c3d     # a single commit
diffpane -- src/search        # limit to a pathspec

It parses the diff, serves a page on 127.0.0.1, opens your browser, and waits. Click a line number to comment. Each comment takes a verdict — ok, fix, or question. Finish review prints the report and exits.

diffpane  14 files, +402/-88
review    http://127.0.0.1:7777/?t=3f9c...

Options

--base <ref>       base ref for the branch diff
--title <text>     human title for the review
--review <file>    narrative JSON (chapters + descriptions) to render
--out <file>       write the markdown report to a file
--json             print machine-readable feedback to stdout
--port <n>         preferred port (default 7777, walks forward if taken)
--no-open          do not open a browser
--timeout <sec>    give up waiting after N seconds (default 3600, 0 = never)

Exit codes

| Code | Meaning | |---|---| | 0 | approved — submitted with no open fix comments, or nothing to review | | 1 | changes requested | | 2 | abandoned — timed out, or you quit without submitting | | 3 | error |

diffpane --staged || { echo "review not clean"; exit 1; }

Long diffs

Collapsed by default, with a one-line summary and an expand control:

• lockfiles, snapshots, dist/, minified and generated files
• added and deleted files in their entirety
• hunks over 40 lines fold their middle, keeping head and tail
• files over 400 diff lines

Anything you have commented on auto-expands. j/k move by hunk, n/p by chapter, c comments on the focused line, ? lists the shortcuts.

Driving it from an agent

Claude Code

diffpane --install-skill

Writes a skill to ~/.claude/skills/diffpane/ — --skill-dir puts it elsewhere. Restart Claude Code, then:

/diffpane

The agent writes the chapter narrative, serves the diff, waits for you, and works through your comments: questions answered before edits, then a report of what it fixed, answered or skipped.

Any other agent

Run with --json and read stdout:

diffpane --working --json

{
  "outcome": "changes-requested",
  "overall": { "verdict": "fix", "body": "two blockers" },
  "comments": [
    {
      "verdict": "fix",
      "body": "Unbounded — needs a max size.",
      "file": "src/search/cache.ts",
      "line": 13,
      "kind": "line",
      "code": "+  const hit = map.get(k);"
    }
  ]
}

Each comment carries the file, the line, and the code it was pinned to.

Chapters

--review takes a narrative that regroups the hunks into chapters:

{
  "title": "Search result caching",
  "story": "Adds an LRU in front of the search endpoint.",
  "chapters": [
    {
      "id": "c1",
      "title": "Cache layer",
      "intent": "New LRU keyed on normalised query.",
      "why": "Repeat queries hit Solr on every keystroke.",
      "hunks": ["f0h0", "f0h1", "f2h0"],
      "size": "+61/-4",
      "flags": ["No eviction test yet."]
    }
  ]
}

Hunk ids are f<file>h<hunk>, in the order the diff reports them. Unclaimed hunks land in a trailing "Everything else". Without --review the page is a plain file-ordered diff.

Security

Each run mints a random token: the page needs it in the URL, the API needs it in an X-Diffpane-Token header, which cross-origin callers cannot set without a preflight. Requests with a non-loopback Host are rejected, and mutations must be JSON. Loopback binding alone is not access control: any page in any tab can reach 127.0.0.1.

Development

cargo test
cargo clippy --all-targets -- -D warnings
cargo fmt --check

The browser suite runs a real Chromium against the built binary:

pnpm install
pnpm exec playwright install chromium
pnpm test:ui
pnpm typecheck

Layout:

• server/ — CLI and HTTP server. The manifest is at the repo root because the binary embeds ui/ and skills/, which cargo packages only from there.
• ui/ — vanilla HTML/CSS/JS, no build step, compiled into the binary. DIFFPANE_UI_DIR=ui serves it from disk instead.
• parity/ — parity.sh check-golden asserts the diff output still matches parity/golden/.

Wire shapes are in server/src/model.rs and are frozen, snake_case.

Open the UI against fixture data without a repo:

diffpane --working --no-open   # then append &fixture=1 to the URL

License

MIT