skill CX Codex

anthropic-ui-skills — Claude Code skill: Anthropic UI design system

Q: How do I install anthropic-ui-skills in Claude?

Run `npx skills add ihlamury/design-skills --skill anthropic-ui-skills -a claude-code`. The skill lands at `~/.claude/skills/anthropic/SKILL.md`.

Hands your agent a fixed set of rules for Anthropic-style interfaces: light surfaces, Inter, a 4px grid. Useful when you keep re-explaining the palette in every prompt.

Install into Claude Code · Skills CLI (Vercel) All methods and platforms ↓

npx skills add ihlamury/design-skills --skill anthropic-ui-skills -a claude-code
npx skills add ihlamury/design-skills --skill anthropic -a claude-code

Open on GitHub

What anthropic-ui-skills does

The skill is a list of constraints the agent follows while writing UI code. It covers colors, typography, spacing, border radius and interactive states, so those decisions stop being made ad hoc. Inside are semantic token tables with hex values, a font size scale from 10px to 68px, 4px grid rules and an animation section.

Some rules are absolute. Page background is #ECE9E0, the primary family is Inter, text contrast stays at 4.5:1 or better, and focus uses a 2px outline in #5E6AD2. Animation is off unless you ask for it; when you do, only transform and opacity, capped at 200ms. A few entries are surprising: input height 0px, h-dvh instead of h-screen, and an aria-label on every icon-only button.

Install runs through npx skills add and drops the skill file into the folder of the agent you name, so the command differs per tool. One caveat: the layout rules assume a 1920px base viewport, and narrow screens are your problem to solve. MIT licensed.

What it helps with

build a light theme with Anthropic's palette
keep a 4px spacing grid consistent across a project
pick Inter sizes and weights for headings and body copy
check text contrast against 4.5:1
stop the agent from adding unrequested animations

Example prompts for the agent

Build the login page following the anthropic-ui-skills rules
Align my current colors and spacing with the design system in the anthropic skill
Audit my buttons and inputs against anthropic-ui-skills

How to install anthropic-ui-skills

1Skills CLI (Vercel)

npx skills add ihlamury/design-skills --skill anthropic-ui-skills -a claude-code

npx skills add ihlamury/design-skills --skill anthropic -a claude-code

2Manually: put the files in place

~/.claude/skills/anthropic/SKILL.md

Copy the whole skill folder; for one project use .claude/skills/anthropic/

1Skills CLI (Vercel)

npx skills add ihlamury/design-skills --skill anthropic -a codex

2Manually: put the files in place

.agents/skills/anthropic/SKILL.md

For all projects use ~/.agents/skills/

1Skills CLI (Vercel)

npx skills add ihlamury/design-skills --skill anthropic -a cursor

2Manually: put the files in place

.cursor/skills/anthropic/SKILL.md

Cursor also reads .agents/skills/ and .claude/skills/

1GitHub CLI

gh skill install ihlamury/design-skills anthropic

2Manually: put the files in place

.github/skills/anthropic/SKILL.md

1Skills CLI (Vercel)

npx skills add ihlamury/design-skills --skill anthropic -a gemini-cli

2Platform CLI

gemini skills install https://github.com/ihlamury/design-skills --path skills/anthropic

Manually: put the files in place

.devin/skills/anthropic/SKILL.md

The legacy .windsurf/skills/ path still works

Skills CLI (Vercel)

npx skills add ihlamury/design-skills --skill anthropic -a opencode

Step by step, with commands for each platform: How to install skills in Claude Code: five ways

Questions about anthropic-ui-skills

How do I install anthropic-ui-skills in Claude?

Run npx skills add ihlamury/design-skills --skill anthropic-ui-skills -a claude-code. The skill lands at ~/.claude/skills/anthropic/SKILL.md.

What does anthropic-ui-skills do?

It gives the agent rules for Anthropic-style interfaces: light surfaces, Inter, a 4px grid, fixed color tokens and animation limits.

Which platforms can use this skill?

There are install commands for Claude, Codex, Cursor, GitHub Copilot, Gemini CLI and OpenCode. On GitHub Copilot you use gh skill install ihlamury/design-skills anthropic.

Source text

SKILL.md · MIT

---
name: anthropic-ui-skills
description: Anthropic's UI design system. Use when building interfaces inspired by Anthropic's aesthetic - light mode, Inter font, 4px grid.
license: MIT
metadata:
  author: design-skills
  version: "1.0.0"
  source: https://www.anthropic.com
---

# Anthropic UI Skills

Opinionated constraints for building Anthropic-style interfaces with AI agents.

## When to Apply

Reference these guidelines when:
- Building light-mode interfaces
- Creating Anthropic-inspired design systems
- Implementing UIs with Inter font and 4px grid

## Colors

- SHOULD use light backgrounds for primary surfaces
- MUST use `#ECE9E0` as page background (`surface-base`)
- SHOULD limit color palette to 8 distinct colors
- MUST maintain text contrast ratio of at least 4.5:1 for accessibility

### Semantic Tokens

| Token | HEX | RGB | Usage |
|-------|-----|-----|-------|
| `surface-base` | #ECE9E0 | rgb(236,233,224) | Page background |
| `surface-raised` | #DBD1C0 | rgb(219,209,192) | Cards, modals, raised surfaces |
| `surface-overlay` | #0F0F10 | rgb(15,15,16) | Overlays, tooltips, dropdowns |
| `text-primary` | #625F59 | rgb(98,95,89) | Headings, body text |
| `text-secondary` | #9F9F9C | rgb(159,159,156) | Secondary, muted text |
| `text-tertiary` | #454036 | rgb(69,64,54) | Additional text |

## Typography

- MUST use `Inter` as primary font family
- SHOULD use single font family for consistency
- MUST use `68px` / `700` for primary headings
- MUST use `33px` / `semi_bold` for body text
- SHOULD reduce font weights (currently 5 detected)
- MUST use `text-balance` for headings and `text-pretty` for body text
- SHOULD use `tabular-nums` for numeric data
- NEVER modify letter-spacing unless explicitly requested

### Text Styles

| Style | Font | Size | Weight | Color | Count |
|-------|------|------|--------|-------|-------|
| `heading-1` | Inter | 68px | 700 | #201F1D | 1 |
| `body` | Inter | 33px | semi_bold | #35312A | 1 |
| `text-23px` | Inter | 23px | 500 | #403D37 | 1 |
| `text-21px` | Inter | 21px | 400 | #3D362C | 1 |
| `text-21px` | Inter | 21px | 400 | #3B352B | 1 |
| `text-20px` | Inter | 20px | 400 | #494237 | 1 |
| `text-17px` | Inter | 17px | 500 | #423F3B | 1 |
| `text-16px` | Inter | 16px | 400 | #454036 | 1 |
| `text-14px` | Inter | 14px | 500 | #3F3931 | 1 |
| `text-14px` | Inter | 14px | 400 | #A2A3A0 | 1 |

### Typography Reference

**Font Families:**
- `Inter` (used 16x)

**Font Sizes:** 10px, 11px, 14px, 16px, 17px, 20px, 21px, 23px, 33px, 68px

## Spacing

- MUST use 4px grid for spacing
- SHOULD use spacing from scale: 3px, 4px, 5px, 6px
- SHOULD use 5px as default gap between elements
- NEVER use arbitrary spacing values (use design scale)
- SHOULD maintain consistent padding within containers

## Borders

- MUST use border-radius from scale: 3px, 15px
- SHOULD use 3px as default border-radius
- NEVER use arbitrary border-radius values (use design scale)
- SHOULD use subtle borders (1px) for element separation

### Border Radius Reference

**Scale:** 3px, 15px

## Layout

- MUST design for 1920px base viewport width
- SHOULD use consistent element widths: 10px, 18px, 146px, 579px
- SHOULD maintain text-heavy layout with clear hierarchy
- NEVER use `h-screen`, use `h-dvh` for full viewport height
- MUST respect `safe-area-inset` for fixed elements
- SHOULD use `size-*` for square elements instead of `w-*` + `h-*`

### Detected Layout Patterns

- **Main Content**: width: 1920px, height: 1004px
- **Main Content**: width: 1920px, height: 673px

## Components

- MUST use `0px` height for input fields

### Buttons

| Variant | Background | Text | Border | Height | Radius |
|---------|------------|------|--------|--------|--------|
| Ghost | transparent | #9F9F9C | none | - | - |

### Inputs

- Height: `0px`

## Interactive States

### Focus

- MUST use `2px` outline with accent color (`#5E6AD2`)
- MUST use `2px` outline-offset
- NEVER remove focus indicators

### Hover

- Buttons (primary): lighten background by 10%
- Buttons (secondary): use `#DBD1C0` background
- List items: use `#DBD1C0` background

### Disabled

- MUST use `opacity: 0.5`
- MUST use `cursor: not-allowed`

## Interaction

- MUST use an `AlertDialog` for destructive or irreversible actions
- SHOULD use structural skeletons for loading states
- MUST show errors next to where the action happens
- NEVER block paste in `input` or `textarea` elements
- MUST add an `aria-label` to icon-only buttons

## Animation

- NEVER add animation unless it is explicitly requested
- MUST animate only compositor props (`transform`, `opacity`)
- NEVER animate layout properties (`width`, `height`, `top`, `left`, `margin`, `padding`)
- SHOULD use `ease-out` on entrance animations
- NEVER exceed `200ms` for interaction feedback
- SHOULD respect `prefers-reduced-motion`

## Performance

- NEVER animate large `blur()` or `backdrop-filter` surfaces
- NEVER apply `will-change` outside an active animation
- NEVER use `useEffect` for anything that can be expressed as render logic

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