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

cargo binstall diffler

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

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

yay -S diffler-bin

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

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

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

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:

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; <tab>/<s-tab>, J/K, or <c-n>/<c-p> step through files from either.

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.