shadcn-ui

A set of guidelines for shadcn/ui, a collection of interface components whose source code is copied into your project and customized. It uses Tailwind CSS for styling and CSS variables for shared design values.

In plain words
What is it for?
Use it to initialize shadcn/ui, add buttons, cards, inputs, and dialogs, organize component files, and safely combine conditional Tailwind classes.
Why use it?
It provides a consistent way to add and customize common controls without treating the components as an unchangeable package.

Cursor rule

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/renvia-code/best-cursor-rules/shadcn-ui
Clone the repo
git clone --depth 1 https://github.com/Renvia-code/best-cursor-rules
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 2,257 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.02257
Opus 5 $0.00000 $0.01128
Sonnet 5 $0.00000 $0.00451
Haiku 4.5 $0.00000 $0.00226

Measured 3d ago against content hash 7428df54a772, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

shadcn-ui scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

rules/styling/shadcn-ui.mdc · 400 lines

How it starts

The opening of the file, as written. The whole thing — 400 lines — stays where its author put it; the contents beside it link to each section on GitHub.

shadcn/ui Best Practices

Overview

Aspect Recommendation
Installation Copy components, don't npm install
Location components/ui/ directory
Customization Edit component source directly
Styling Tailwind CSS + CSS variables

Installation

Initial Setup

# Initialize shadcn/ui in your project
npx shadcn@latest init

# Add components as needed
npx shadcn@latest add button
npx shadcn@latest add card
npx shadcn@latest add input
npx shadcn@latest add dialog

Project Structure

src/
├── components/
│   ├── ui/              # shadcn/ui components
│   │   ├── button.tsx
│   │   ├── card.tsx
│   │   ├── input.tsx
│   │   └── ...
│   └── custom/          # Your custom components
├── lib/
│   └── utils.ts         # cn() utility
└── styles/
    └── globals.css      # CSS variables

Core Utility: cn()

// lib/utils.ts
import { clsx, type ClassValue } from "clsx"
import { twMerge } from "tailwind-merge"

export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs))
}

Usage

import { cn } from "@/lib/utils"

// Merge classes safely
<button className={cn(
  "px-4 py-2 rounded-lg",
  isPrimary && "bg-blue-600 text-white",
  isDisabled && "opacity-50 cursor-not-allowed",
  className // Allow custom classes to override
)}>
  Click me
</button>

Button Patterns

Button Variants

import { Button } from "@/components/ui/button"

// Variants
<Button variant="default">Default</Button>
<Button variant="destructive">Delete</Button>
<Button variant="outline">Outline</Button>
<Button variant="secondary">Secondary</Button>
<Button variant="ghost">Ghost</Button>
<Button variant="link">Link</Button>

// Sizes
<Button size="default">Default</Button>
<Button size="sm">Small</Button>
<Button size="lg">Large</Button>
<Button size="icon"><IconPlus /></Button>

// With loading state
<Button disabled={isLoading}>
  {isLoading && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
  {isLoading ? 'Loading...' : 'Submit'}
</Button>

// As child (render as different element)
<Button asChild>
  <Link href="/dashboard">Go to Dashboard</Link>
</Button>

Read the full file on GitHub · 400 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 400 lines · 0 tokens per session scan A 7428df54a772

Subscribe to this mod's changes

shadcn-ui is a cursor rule published in the GitHub repository Renvia-code/best-cursor-rules (12 stars, last pushed 9mo ago), licensed CC0-1.0. It costs nothing until one of its globs matches a file; then it loads 2,257 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.