# clerk-astro-patterns

Walks your agent through Clerk inside Astro: middleware, protected SSR pages, API route auth and island components.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 14300 installs · ★ 89
- Author: clerk
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/clerk/skills/tree/HEAD/skills/clerk-astro-patterns/SKILL.md
- Updated: 2026-10-23
- HTML: https://affpapa.org/en/nevibecode/skills/clerk-astro-patterns

## What it does

The skill covers how Clerk auth behaves across Astro's two rendering modes. SSR pages read `Astro.locals.auth()`, filled in by the middleware. Static pages with `export const prerender = true` skip that middleware entirely, so auth there lives in client-side hooks inside islands.

Inside are task-based references: middleware setup, SSR page protection, Clerk in island components, auth in API routes, and React in Astro. A pitfalls table maps symptoms to causes. `Astro.locals.auth` comes back undefined when `src/middleware.ts` has no `clerkMiddleware`; an island that ignores sign-in usually just lacks the `client:load` directive.

You need `@clerk/astro` v4+ and Astro 5+. Two env vars go in `.env`: `PUBLIC_CLERK_PUBLISHABLE_KEY` and `CLERK_SECRET_KEY`. Astro exposes client variables with the `PUBLIC_` prefix, not `NEXT_PUBLIC_`. If your codebase still calls `createRouteMatcher`, that is worth checking before you upgrade: the function was removed in `@clerk/astro` 4.0, and those checks have to move into pages and API routes.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add clerk/skills --skill clerk-astro-patterns -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/clerk-astro-patterns/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/clerk-astro-patterns/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add clerk/skills --skill clerk-astro-patterns -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/clerk-astro-patterns/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add clerk/skills --skill clerk-astro-patterns -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/clerk-astro-patterns/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install clerk/skills clerk-astro-patterns
```

2. **Manually: put the files in place**
- File: `.github/skills/clerk-astro-patterns/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add clerk/skills --skill clerk-astro-patterns -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/clerk/skills --path skills/clerk-astro-patterns
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/clerk-astro-patterns/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add clerk/skills --skill clerk-astro-patterns -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/clerk/skills/tree/HEAD/skills/clerk-astro-patterns/SKILL.md

## When to use it
- protect an SSR page and redirect signed-out visitors
- check the user inside an API route and return 401
- wire Clerk into a React island component
- debug auth that works in dev but fails in production
- migrate off `createRouteMatcher` to per-page checks

## Example prompts
- Set up clerkMiddleware in src/middleware.ts and show me how to protect an SSR page
- Add a userId check to src/pages/api/data.ts and return 401 without a session
- Why does my island ignore sign-in? Check the client:load directive

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 3ed41437aa25383f.

BEGIN THIRD-PARTY FILE 3ed41437aa25383f
````text
---
name: clerk-astro-patterns
description: 'Astro patterns with Clerk — middleware, SSR pages, island components,
  API routes, static vs SSR rendering. Triggers on: astro clerk, clerk astro middleware,
  astro protected page, clerk island component, astro API route auth, clerk astro
  SSR.'
license: MIT
allowed-tools: WebFetch
metadata:
  author: clerk
  version: 1.0.0
---

# Astro Patterns

SDK: `@clerk/astro` v4+. Requires Astro 5+.

## What Do You Need?

| Task | Reference |
|------|-----------|
| Configure middleware (bare `clerkMiddleware()`, checks per page) | references/middleware.md |
| Protect SSR pages | references/ssr-pages.md |
| Use Clerk in island components | references/island-components.md |
| Auth in API routes | references/api-routes.md |
| Use Clerk with React in Astro | references/astro-react.md |

## Mental Model

Astro has two rendering modes per page: **SSR** and **static prerender**. Clerk works differently in each:

- **SSR pages** — use `Astro.locals.auth()` which is populated by the middleware
- **Static pages** (`export const prerender = true`) — Clerk middleware skips them; use client-side hooks in islands
- **Islands** — React/Vue/Svelte components; use `useAuth()` and other hooks from `@clerk/astro/react`

```
Request → clerkMiddleware() → SSR page → Astro.locals.auth()
                                ↓
                         Island (.client) → useAuth() hook
```

## Setup

### astro.config.mjs

```ts
import { defineConfig } from 'astro/config'
import clerk from '@clerk/astro'

export default defineConfig({
  integrations: [clerk()],
  output: 'server',
})
```

### src/middleware.ts

```ts
import { clerkMiddleware } from '@clerk/astro/server'

export const onRequest = clerkMiddleware()
```

The middleware populates `Astro.locals.auth()`. Each page and API route checks for itself. `createRouteMatcher` was removed in `@clerk/astro` 4.0 (deprecated in 3.x). Don't add it. Existing uses must move to page and API-route checks before upgrading. See the [Astro `clerkMiddleware()` reference](https://clerk.com/docs/reference/astro/clerk-middleware).

## SSR Page Auth

```astro
---
const { userId, orgId } = Astro.locals.auth()
if (!userId) return Astro.redirect('/sign-in')
---

<h1>Dashboard</h1>
```

## API Route Auth

```ts
// src/pages/api/data.ts
import type { APIRoute } from 'astro'

export const GET: APIRoute = ({ locals }) => {
  const { userId } = locals.auth()
  if (!userId) return new Response('Unauthorized', { status: 401 })

  return Response.json({ userId })
}
```

## Common Pitfalls

| Symptom | Cause | Fix |
|---------|-------|-----|
````
END THIRD-PARTY FILE 3ed41437aa25383f

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