Impeccable

Impeccable is an open-source design language for AI coding agents, with around 85,800 stars on GitHub under the Apache-2.0 license. It gives your AI harness a shared design vocabulary: one skill, twenty-four commands, live browser iteration, and sixty-two deterministic detector rules for AI-generated frontend design.

Overview

Impeccable starts from a familiar frustration. Every model trained on the same SaaS templates produces the same handful of tells: Inter for everything, purple-to-blue gradients, cards nested in cards, gray text on colored backgrounds, and the rounded-square icon tile above every heading. Impeccable counters with a full workflow. A setup flow records durable product truth in a PRODUCT.md file, so later commands know the audience, purpose, and constraints. From there, twenty-four commands cover the whole design job, and a live mode iterates on elements directly in the browser.

Key Features

• Twenty-four commands: A shared vocabulary with your AI, including craft, init, audit, critique, polish, bolder, quieter, distill, harden, animate, colorize, typeset, layout, and live, each addressing one concrete design task.
• Sixty-two deterministic detector rules: The CLI and browser extension run these rules with no LLM and no API key, catching anti-patterns such as overused fonts, gray text on colored backgrounds, and nested cards.
• Live browser iteration: Live mode lets the agent generate and refine visual variants of a named element in the real browser, instead of guessing from code alone.
• Product truth first: The init command inspects the project, asks only for missing material facts, and writes PRODUCT.md, while visual direction lives separately in DESIGN.md.
• Works across harnesses: Install once and use it with Claude Code, Cursor, Codex, Gemini CLI, Grok Build, GitHub Copilot, and many other supported tools, with provider-native hooks where available.
• Case studies and demos: The project site shows before-and-after transformations of real projects.
• Flexible installation: Install with the CLI installer, a Git submodule, a plugin install, a website download, or a manual copy from the repository.

💳 Pricing

Impeccable is free and open source under the Apache-2.0 license. There is no paid tier; the skill, CLI, and detector rules are all available to everyone.

Who Is It For

Impeccable is for developers who build frontends with AI coding agents and want the output to look designed rather than generated. It suits solo builders shipping products, teams standardizing design quality across AI-assisted work, and anyone who reviews AI-written interfaces and keeps spotting the same visual clichés.