Diffler Mcp

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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. 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

The installed command is always diffler. Pick whatever fits:

# Rust: compile from source, or grab the prebuilt with cargo-binstall
cargo install diffler
cargo binstall diffler

# Homebrew (macOS / Linux)
brew tap matheusfillipe/diffler https://github.com/matheusfillipe/diffler
brew install diffler

# Scoop (Windows)
scoop bucket add diffler https://github.com/matheusfillipe/diffler
scoop install diffler

# Arch (AUR)
yay -S diffler-bin

# Nix (flake, runs the prebuilt binary)
nix run github:matheusfillipe/diffler
nix profile install github:matheusfillipe/diffler

# npm: prebuilt binary, one-off or global
npx @mattfillipe/diffler
npm install -g @mattfillipe/diffler

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

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.

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. TAB moves focus between them; j/k change the selected file from the sidebar or scroll the diff when focused there; J/K (or <c-n>/<c-p>) switch files from either.

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/Forgejo PRs, including PRs whose branch you never checked out.

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

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.