About this Skill
ub-mode is a compact coding-agent Skill organized around making a change work, improving its design and following a repeatable practice. It asks for a failing test before a change where practical, attention to domain boundaries and idempotency, root-cause fixes, behavior-focused tests and refactoring. It references separate CRAP score, duplication and mutation-testing tools.
Why we picked it
A concise set of coding-agent instructions covering small changes, domain boundaries and quality gates. It also asks the agent to keep an action log and commit and push work; review those practices against your own project instructions.
What it helps with
- Guide a coding agent through a small, test-driven change.
- Review duplication, complexity and mutation-testing results during refactoring.
- Make architectural boundaries and data validation explicit in a software project.
How it works
Make it work
Prefer small changes, model the data and write a failing test first when an honest test is practical.
Make it right
Reproduce and fix root causes, test observable behavior, refactor and use the separately installed quality tools.
Follow project practice
Record actions and review cleanup or Git operations against the project’s own rules.
Installation and companion tools
The author documents copying the single SKILL.md into an agent-specific skills directory. The example below targets Claude Code; Cursor and Grok use the respective directories listed in the README.
The quality tools are separate projects. Their availability, setup and language support depend on each tool.
| Command | What it helps with |
|---|---|
mkdir -p ~/.claude/skills/ub-mode && curl -fL https://raw.githubusercontent.com/unclebob/ub-mode/master/SKILL.md -o ~/.claude/skills/ub-mode/SKILL.md | Copy the Skill entrypoint to the Claude Code skills directory. |
Upstream README and installationCrapper quality toolDryer duplication toolMutator mutation testing
Before you use it
- Copy the upstream SKILL.md into a supported agent’s skills directory. The repository documents Claude Code, Cursor and Grok installation paths.
- Crapper, Dryer and Mutator are separate repositories and must be installed or made available separately for their respective checks.
- The instructions request action logging, worktree cleanup, commits and a push to the main line. Follow your project’s own permissions and Git workflow when applying them.
- The upstream repository does not specify a license.
Supported agents
Sources & references
Original sources are linked below. Practical starting points are editorial suggestions from SkillHey.
