rrubocop MCP server

rrubocop

10x faster RuboCop drop-in — same CLI, .rubocop.yml, and offense output, without maintaining RuboCop gems. Linting and simple config need no Ruby; complex ERB still does. Point it at an existing project and use it like RuboCop.

One binary — runs the same way regardless of rbenv, rvm, system Ruby, or Docker. Uses tree-sitter; no Ruby runtime required for linting or simple ERB. Unsupported ERB falls back to ruby / bundle exec ruby.

Drop-in parity: reads your existing .rubocop.yml, emits RuboCop-like text/JSON, supports -a/-A autocorrect, and grows cop coverage over time.

Baseline (shown in --help / --version): rubocop 1.91.0 with rubocop-rails 2.37.0, rubocop-performance 1.27.0, rubocop-rspec 3.9.0, rubocop-rspecrails 2.32.0, rubocop-factorybot 2.28.0 — pinned in src/resources/baseline.json.

Parity runs have been verified over 600+ installed Ruby gem projects (RuboCop vs rrubocop on the same trees).

Install

brew install adrianov/rrubocop/rrubocop

cargo install rrubocop

macOS (.tar.gz from GitHub Releases; binary + man):

# Apple Silicon — use the *-x86_64-apple-darwin.tar.gz asset on Intel Macs
curl -LO https://github.com/adrianov/rrubocop/releases/download/v0.8.10/rrubocop-0.8.10-aarch64-apple-darwin.tar.gz
tar -xzf rrubocop-0.8.10-aarch64-apple-darwin.tar.gz
sudo cp rrubocop-0.8.10-aarch64-apple-darwin/rrubocop /usr/local/bin/
sudo mkdir -p /usr/local/share/man/man1
sudo cp rrubocop-0.8.10-aarch64-apple-darwin/rrubocop.1 /usr/local/share/man/man1/

Ubuntu / Debian (.deb from GitHub Releases; amd64, Ubuntu 22.04+ / Debian bookworm+):

# example for v0.8.10 — use the asset name from the release page
curl -LO https://github.com/adrianov/rrubocop/releases/download/v0.8.10/rrubocop_0.8.10-1_amd64.deb
sudo dpkg -i rrubocop_0.8.10-1_amd64.deb
man rrubocop

rrubocop [OPTIONS] [PATH]...

Features

• Config — RuboCop-compatible resolution: walk-up discovery, inheritfrom / inheritgem / require/plugins, inheritmode (merge/override), nested .rubocop.yml overrides, DisabledByDefault, NewCops / Enabled: pending, plus per-cop Enabled / Exclude / Include / options; public gem defaults/inheritgem YAML are vendored by version (from Gemfile.lock, with same_as aliases when YAML is identical) and parsed in memory; private/unlisted gems fall back to bundle info --path; simple ERB in YAML expands natively (Ruby only for unsupported tags)
• Autocorrect — -a (safe) / -A (all)
• Output — progress (marks stream as files finish), text, json, github, quiet, files, … (TTY color like RuboCop; --color / --no-color)
• Directives — # rubocop:disable / enable
• Parser — tree-sitter-ruby (no Prism / no CRuby)
• Cache — content-addressed cache.redb under $RRUBOCOPCACHEDIR or $XDGCACHEHOME/rrubocop / ~/.cache/rrubocop (same style as abcop); --cache false skips reads but still writes
• Prefer MCP with LLMs. rrubocop --mcp is the best way to use rrubocop from an agent: the model gets offenses as soon as it writes, so it can fix and autocorrect in the same turn and ship effective code right away — not after a later CLI/CI pass. Official Rust rmcp SDK; same tools as RuboCop 1.85+: rubocopinspection and rubocopautocorrection

Reference implementations: nitrocop (architecture & fixtures), upstream RuboCop.

Built-in cops

Departments grow breadth-first from common RuboCop plugin sets (nitrocop / gem sources). Notable coverage:

Shortened. The full README is on GitHub.