301-clerk-patterns

301-clerk-patterns is a cursor rule for Cursor from johnpolacek/vibecode.party.starter. It costs 0 tokens per session (966 once invoked), scanned A, original, MIT.

A set of authentication patterns for Clerk, a service that manages user sign-in and accounts, in a Next.js application. It shows how server and browser code checks whether a user is signed in.

In plain words
What is it for?
It helps protect server actions, conditionally show authenticated content, display sign-in prompts, and use reusable Clerk sign-in components.
Why use it?
It reduces inconsistent login checks and helps prevent protected actions or content from being used by signed-out visitors.

Cursor rule for Cursor

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/johnpolacek/vibecode.party.starter/301-clerk-patterns
Clone the repo
git clone --depth 1 https://github.com/johnpolacek/vibecode.party.starter

Made for: Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for 301-clerk-patterns

README.md
[![agentmods](https://agentmods.dev/badge/rules/johnpolacek/vibecode.party.starter/301-clerk-patterns.svg)](https://agentmods.dev/rules/johnpolacek/vibecode.party.starter/301-clerk-patterns)
Your own site
<a href="https://agentmods.dev/rules/johnpolacek/vibecode.party.starter/301-clerk-patterns"><img src="https://agentmods.dev/badge/rules/johnpolacek/vibecode.party.starter/301-clerk-patterns.svg" alt="Measured on agentmods" height="20"></a>
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 966 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 $0.00966
Opus 5 $0.00000 $0.00483
Sonnet 5 $0.00000 $0.00193
Haiku 4.5 $0.00000 $0.00097

Measured 5d ago against content hash 2f43551fcabe, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

301-clerk-patterns 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 5d 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.

.cursor/rules/300-auth/301-clerk-patterns.mdc · 157 lines

How it starts

The opening of the file, as written. The whole thing — 157 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Clerk Authentication Patterns

Description

This rule documents the standard patterns for implementing authentication with Clerk in our application, including reusable components and best practices.

Server-Side Authentication

Server Components

import { auth } from "@clerk/nextjs/server"

export default async function ServerComponent() {
  const { userId } = await auth()
  
  // Use userId to conditionally render content
  if (!userId) {
    return <SignInPrompt />
  }
  
  return <AuthenticatedContent />
}

Server Actions

import { auth } from "@clerk/nextjs/server"

export async function serverAction() {
  const { userId } = await auth()
  if (!userId) {
    throw new Error("Unauthorized")
  }
  // Proceed with authenticated action
}

Client-Side Authentication

Client Components

"use client"
import { useUser, SignInButton } from "@clerk/nextjs"

export function ClientComponent() {
  const { isSignedIn, isLoaded, user } = useUser()
  
  if (!isLoaded) return <LoadingState />
  if (!isSignedIn) return <SignInPrompt />
  
  return <AuthenticatedContent />
}

Reusable Components

SignInButton

The SignInButton component from Clerk should be used with our custom Button component:

import { SignInButton } from "@clerk/nextjs"
import { Button } from "@/components/ui/button"

<SignInButton mode="modal">
  <Button size="lg">Sign in to Continue</Button>
</SignInButton>

Auth Buttons

For navigation/header auth controls, use our AuthButtons component:

import AuthButtons from "@/components/nav/auth-buttons"

<AuthButtons />

Sign In Prompt Card

For gating features behind authentication, use this pattern:

<Card>
  <CardContent className="flex flex-col items-center gap-6 py-16">
    <div className="text-center space-y-2">
      <h2 className="text-2xl font-semibold">Sign in to Continue</h2>
      <p className="text-muted-foreground">Create an account or sign in to access this feature</p>
    </div>
    <SignInButton mode="modal">
      <Button size="lg">Sign in to Continue</Button>
    </SignInButton>
  </CardContent>
</Card>

Read the full file on GitHub · 157 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. 5d ago First seen · 157 lines · 966 tokens per session scan A 2f43551fcabe

Subscribe to this mod's changes

301-clerk-patterns is a cursor rule published in the GitHub repository johnpolacek/vibecode.party.starter (27 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 966 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.