Impeccable

Impeccable is an open-source project by Paul Bakaus that gives AI coding agents a shared design vocabulary and a set of deterministic anti-pattern rules to prevent generic, "AI-slopped" frontend output. It ships as an agent skill installable into Cursor, Claude Code, Gemini CLI, Codex CLI, GitHub Copilot, and other major AI harnesses, alongside a CLI and Chrome extension. The project is licensed under Apache 2.0 and is free for everyone.

What It Is

Impeccable is an agent skill framework — a collection of 23 commands, 7 domain reference files, and a detection engine — that plugs into AI coding harnesses to improve the visual quality of generated frontend code. Rather than replacing the AI model, it provides structured design guidance (typography, color, spatial design, motion, interaction, responsive, UX writing) that the model reads before generating or refining UI. The project originated from Anthropic's frontend-design skill and has been substantially extended.

The Command Vocabulary

The 23 commands are accessed through a single /impeccable entry point and cover the full design lifecycle:

• Create: /impeccable craft, /impeccable shape — plan and build UI in one flow
• Evaluate: /impeccable critique, /impeccable audit — design review and technical quality checks
• Refine: /impeccable typeset, /impeccable colorize, /impeccable animate, /impeccable layout, /impeccable bolder, /impeccable quieter, /impeccable overdrive, /impeccable delight
• Simplify: /impeccable distill, /impeccable clarify, /impeccable adapt
• Harden: /impeccable polish, /impeccable optimize, /impeccable harden, /impeccable onboard
• System: /impeccable document, /impeccable extract, /impeccable live, /impeccable init

Commands accept optional arguments to focus on a specific area (e.g., /impeccable audit the header). Frequently used commands can be pinned as standalone shortcuts via /impeccable pin <command>.

Slop Detection and CI Integration

A core feature is the deterministic anti-pattern detector, which the project describes as covering 41 rules (27 deterministic + a 12-rule LLM critique pass in the skill itself, plus additional CLI rules). The CLI runs with no LLM and no API key:

• npx impeccable detect src/ scans a directory
• npx impeccable detect https://example.com scans a live URL via Puppeteer
• JSON output and exit codes make it suitable for PR checks and build gates

The Chrome extension runs the same detector as an overlay on any page in the browser.

Live Mode and Source Writes

Live Mode (currently in beta) lets developers pick any element in a running dev server, annotate it, and generate three production-quality variants that cycle in via the framework's HMR. Accepting a variant writes it directly to the source file as an ordinary edit — not a throwaway mock — so it can be reviewed, committed, or undone.

Design System Awareness

Impeccable reads existing project context before designing. It scans tokens, Tailwind config, and component files, and loads a PRODUCT.md brief and DESIGN.md spec on every command. The /impeccable document command generates a DESIGN.md in the Google Stitch format, making the visual system portable and readable by other DESIGN.md-aware tools. New work is matched to the existing system rather than overwriting it with model defaults.

Update: CLI v2.3.2

The latest release is CLI v2.3.2, published on 2026-05-30, with the repository last pushed on 2026-06-01. The GitHub repository shows 32,000+ stars and over 1,700 forks as of the data collected. Supported harnesses include Cursor, Claude Code, OpenCode, Pi, Gemini CLI, Codex CLI, VS Code Copilot, Kiro, Trae, Rovo Dev, and Qoder.