diffler

A tool for taking ownership of agentic code: review what your agent writes, together with the agent, while it happens. The code that lands is code you have actually reviewed.

If you know Emacs' magit, diffler is basically a standalone magit with an MCP server built in: the same fast, keyboard-driven git UI, no Emacs required. The keys follow the Doom Emacs magit experience, so its leader-key transients land where your fingers expect them. Launch it in a repo alongside Claude Code or any MCP-compatible agent: it shows a live diff of what the agent is doing; you read, comment, stage, and commit; the agent picks your feedback up over MCP and responds in place. One binary, no browser, no daemon.

Install

cargo install diffler

Prebuilt binary

Skips the compile, and needs no Rust toolchain.

cargo binstall diffler

Or download it straight from the releases page: macOS, Linux and Windows, x86_64 and arm64. Any GitHub-release installer (eget, ubi, ...) works against it too.

Homebrew

macOS and Linux. The tap is this repository.

brew tap matheusfillipe/diffler https://github.com/matheusfillipe/diffler
brew install diffler

Scoop

Windows. The bucket is this repository.

scoop bucket add diffler https://github.com/matheusfillipe/diffler
scoop install diffler

Arch

diffler-bin on the AUR ships the prebuilt binary, so it installs without building.

yay -S diffler-bin

Nix

The flake serves the prebuilt binary. nix run tries it without installing anything, nix profile install keeps it.

nix run github:matheusfillipe/diffler
nix profile install github:matheusfillipe/diffler

npm

A wrapper that fetches the prebuilt binary. The package name is scoped, the command it installs is plain diffler.

npx @mattfillipe/diffler
npm install -g @mattfillipe/diffler

Quickstart

Run diffler inside a repository. It starts the TUI and an MCP server on port 8417. Connect your agent once:

Claude Code

claude mcp add --transport http diffler http://127.0.0.1:8417/mcp
# or, over stdio, auto-discovering the port:
claude mcp add diffler -- npx -y diffler-mcp
# or, as a plugin (MCP server plus a /diffler command):
claude plugin marketplace add matheusfillipe/diffler && claude plugin install diffler@diffler

Connected, the server's review prompt shows up as the /diffler:review command; the plugin adds a bare /diffler.

opencode

Add the server to opencode.json in the project, or globally in ~/.config/opencode/opencode.json:

{
  "mcp": {
    "diffler": {
      "type": "local",
      "command": ["npx", "-y", "diffler-mcp"],
      "enabled": true
    }
  }
}

And install the /diffler command (opencode has no package mechanism for commands, so this fetches the one maintained in this repo):

mkdir -p ~/.config/opencode/commands && curl -fsSLo ~/.config/opencode/commands/diffler.md \
  https://raw.githubusercontent.com/matheusfillipe/diffler/main/.opencode/commands/diffler.md

Any other MCP agent

Point it at http://127.0.0.1:8417/mcp (streamable HTTP), or run npx -y diffler-mcp as a stdio proxy that auto-discovers the port from .diffler/mcp.json. The server also ships a review prompt that prompt-aware clients surface as a command.

The loop: the agent edits files, the diff updates live. You comment lines or ranges in the diff view and press Z to send feedback. The agent picks the comments up through wait_for_feedback, replies or proposes resolutions, and you confirm in the TUI. y/Y copy the same feedback as markdown if you would rather paste it into a prompt.

The same review works against real pull requests: the status screen shows the branch's PR (and b p lists all open ones; reviewing never needs a checkout). PR comments sync in as regular threads, yours stack locally, and S submits them as a single review on the forge. b P opens a new one from the current branch, filling the title and body from its commits and pushing first when the forge has not seen the branch yet. Replies the agent wrote stay local: what goes out carries your name, so it is what you wrote.

Keys

Vim-like: j/k/gg/G motions, / search, and <c-d>/<c-u> paging work in every list. The basics:

Key	Action
<c-k>	command palette: fuzzy-find every action on this screen and its key
<cr>	open the thing under the cursor
s / u	stage / unstage
cc	commit
c	comment the diff line (V selects a range first)
m / u / U	in the diff view: mark the file viewed and step to the row under it, sorting it to the top of its group (a folder row marks everything under it) / jump to the next unviewed / clear every mark
+ / - / =	widen / narrow the context around a hunk, or open the whole file
|	side-by-side diff
t	cycle the sidebar: file tree, review buckets (viewed files fold away, come back if they change), kinds (source, tests, docs, config, build, generated, assets)
Z	send feedback to the agent
C	comments sidebar: walk every comment, Enter jumps to it in the pane
d / D	delete the comment under the cursor / every local comment of the review
S	submit stacked PR comments as one review
b P	open a pull request for the current branch
d	review the working tree against something else: d base branch, c last commit, b a branch, s a commit, w HEAD
y / Y	copy feedback as markdown (file / all)
y	on a status or PR-list row, copy what it points at: a pull request as its URL, a commit as its sha, a file or folder as its repo-relative path
gf	find any tracked file: Enter opens it, b blames it, e sends it to $EDITOR
B	blame the file under the cursor, at that line (b toggles the column, <cr> reviews the commit)
L	language breakdown of the repo: files, lines, code, comments per language (s sorts)
e	open the file in $EDITOR
?	full keymap for the current screen
q	back / quit

Every binding is remappable, see docs/config.example.toml.

The diff view is two panes: a file sidebar and the selected file's diff. h and l (or the left/right arrows) focus the sidebar and the diff; j/k change the selected file from the sidebar or scroll the diff when focused there, and <c-d>/<c-u> page whichever pane has the keyboard; J/K or <c-n>/<c-p> step through files from either; <tab> (or za) folds the folder or section under the sidebar cursor.

Diffs are compared on the syntax tree, so a reindented or rewrapped block highlights only the tokens that actually differ.

The mouse works too (including over tmux): the wheel scrolls the pane under the pointer, and a left click selects a row. Clicking a section, directory, or recent-commits header folds it, and clicking a sidebar file opens it. Mouse capture means the terminal's own text selection needs the usual override (Shift, or Option in iTerm2).

How it compares

Pagers like delta render diffs beautifully, and lazygit and gitui are great general git TUIs. diffler is review-first: comments live on diff lines, an agent reads and answers them over MCP while you watch, and the same threads work against real GitHub, GitLab and Forgejo pull requests, including ones whose branch you never checked out.

You may also want to check tuicr, the closest alternative.

MCP tools

While the TUI is running, diffler serves an MCP server the agent uses to read your review and respond in place. See docs/mcp.md.

Configuration

Layered TOML: defaults, then ~/.config/diffler/config.toml (XDG respected, macOS included), then <repo>/.diffler/config.toml, then CLI flags. Every option and key remap, documented with its default, lives in docs/config.example.toml. Inspect the merged result and where each value came from:

diffler config --dump

Themes

Switchable live with T, or set ui.theme. The gallery shows each one.

Development

just ci     # core gate: fmt + clippy + tests
just e2e    # PTY end-to-end suite (needs uv)

Requires Rust 1.88+, just, cargo-nextest. Hooks: prek install.

License

MIT or Apache-2.0, at your option.