/shadcn-detection

name: shadcn-detection
description: "Use when determining which component base (Base UI, Radix UI or React Aria) a shadcn/ui project uses, before any component work or migration."
versions:
  shadcn-ui: "4.x"
  radix-ui: "1.x"
  base-ui: "1.x"
user-invocable: true
allowed-tools: Read, Glob, Grep, Bash
references: references/radix-patterns.md, references/baseui-patterns.md, references/detection-algorithm.md, references/templates/detection-script.md
related-skills: shadcn-components, shadcn-migration

<objective> Detects which of the three shadcn/ui component bases a project uses: Base UI (`base`, default for new projects since July 2026), Radix (`radix`, fully supported) or React Aria (`aria`, added July 2026). Authoritative signal first (`shadcn info --json` -> `config.base`), then a 5-signal weighted scan: package.json dependencies, components.json's style prefix, source import patterns, data-attribute conventions (`data-state` vs `data-open` vs `data-entering`), and the lockfile-detected package manager.

Produces a Base UI / Radix / React Aria / Mixed (migration needed) / None (fresh setup) verdict that gates every downstream shadcn component or migration task. </objective>

shadcn Detection

Agent Workflow (MANDATORY)

Before detection, spawn agents in parallel, one `Agent` call each with a `name`:

1. **fuse-ai-pilot:explore-codebase** - Scan project structure 2. **fuse-ai-pilot:research-expert** - Verify latest primitive patterns

After: Use results to configure component workflow.

---

Overview

| Feature | Description | |---------|-------------| | **CLI probe (authoritative)** | `{runner} shadcn@latest info --json` -> `.config.base` = `base` \| `radix` \| `aria` (plus `.config.style`, `.components`, `.links`) | | **Package scan** | Detect `@base-ui/react`, `radix-ui` / `@radix-ui/*`, `react-aria-components` | | **Config check** | Analyze components.json style prefix (`base-*`, `radix-*`/`new-york`, `aria-*`) | | **Import analysis** | Scan source for import patterns | | **Attribute scan** | `data-state=` (Radix) vs `data-open` (Base UI) vs `data-entering`/`data-placement` (React Aria) | | **Package manager** | Detect bun/npm/pnpm/yarn via lockfile |

| Base | Package | Style prefix | Composition | Docs | |------|---------|--------------|-------------|------| | Base UI (default) | `@base-ui/react` | `base-*` | `render` prop | `/docs/components/base/<name>` | | Radix | `radix-ui` (legacy `@radix-ui/react-*`) | `radix-*`, legacy `new-york` | `asChild` | `/docs/components/radix/<name>` | | React Aria | `react-aria-components` | `aria-*` | Trigger wrapper (`DialogTrigger > Button + Dialog`), `slot`, `onPress` | `/docs/components/aria/<name>` |

Known cross-base dependencies (NOT a mixed project): `radix-*` Combobox imports `@base-ui/react` (Radix has no Combobox); Questionnaire and MessageScroller import `@shadcn/react` on every base; every current component imports `cn` from the `cn` package.

---

Critical Rules

1. **ALWAYS run detection** before any component work 2. **CHECK all 5 signals** for maximum accuracy 3. **HANDLE mixed state** as migration case, never ignore 4. **CACHE result** for session duration, no re-detection needed 5. **DETECT package manager** via lockfile priority order

---

Architecture

project/
├── package.json            # Step 1: deps scan
├── components.json         # Step 2: style field
├── bun.lock|bun.lockb|pnpm-lock.yaml|yarn.lock|package-lock.json  # Step 5: PM
└── src/|components/|app/   # Step 3-4: imports + attrs

→ See [detection-script.md](references/templates/detection-script.md) for complete example

---

5-Step Detection Algorithm

Step 0: if `components.json` exists, `{runner} shadcn@latest info --json` gives the base directly; the weighted scan below confirms it and catches mixed projects.

| Step | Signal | Weight | |------|--------|--------| | 1 | `package.json` deps (`@base-ui/react`, `radix-ui` / `@radix-ui/*`, `react-aria-components`) | 40% | | 2 | `components.json` style prefix (`base-*`, `radix-*`/`new-york`, `aria-*`) | 20% | | 3 | Import patterns in source files | 25% | | 4 | Data attributes (`data-state=` / `data-open` / `data-entering`) | 15% | | 5 | Package manager (lockfile → `bunx`/`npx`/`pnpm dlx`/`yarn dlx`) | - |

---

Decision Table

Each base gets its own score (0-100).

| Scores | Result | Action | |--------|--------|--------| | Only Base UI >50 | **Base UI** | Use Base UI patterns (`render`) | | Only Radix >50 | **Radix** | Use Radix patterns (`asChild`) | | Only React Aria >50 | **React Aria** | Use React Aria patterns (trigger wrapper, `onPress`) | | Two or more >0 (after discounting the known cross-base deps above) | **Mixed** | Migration needed | | All 0 | **None** | Fresh setup: `init` defaults to Base UI; pass `-b radix` or `-b aria` to choose |

---

Best Practices

DO

• Run detection BEFORE any component work
• Check all 5 signals for accuracy
• Handle "mixed" state as migration case

DON'T

• Assume Radix (or Base UI, the new default) without checking
• Skip components.json analysis
• Ignore data-attribute signals
• Count `@base-ui/react` from a Radix-style Combobox as a mixed project

---

Reference Guide

Concepts

| Topic | Reference | When to Consult | |-------|-----------|-----------------| | **Radix Patterns** | [radix-patterns.md](references/radix-patterns.md) | Identifying Radix UI signals | | **Base UI Patterns** | [baseui-patterns.md](references/baseui-patterns.md) | Identifying Base UI signals | | **Algorithm** | [detection-algorithm.md](references/detection-algorithm.md) | Understanding scoring logic, React Aria signals |

Templates

| Template | When to Use | |----------|-------------| | [detection-script.md](references/templates/detection-script.md) | Running detection on a project |