nextjs15-params

A set of rules for Next.js 15 pages and layouts, where route parameters and search parameters are asynchronous values.

In plain words
What is it for?
Use it when writing pages, layouts, or metadata functions that read URL route parameters or search parameters in Next.js 15.
Why use it?
It prevents code written for Next.js 14 from failing because it reads these values before awaiting them.

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/vibestackdev/vibe-stack/nextjs15-params
Clone the repo
git clone --depth 1 https://github.com/vibestackdev/vibe-stack

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 389 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 $0.00389
Opus 5 $0.00000 $0.00195
Sonnet 5 $0.00000 $0.00078
Haiku 4.5 $0.00000 $0.00039

Measured yesterday against content hash 5fa107fdcf43, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

nextjs15-params 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 yesterday.

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/nextjs15-params.mdc · 56 lines

What it actually says

Next.js 15 Async Params (BREAKING CHANGE)

CRITICAL: In Next.js 15+, params and searchParams are ASYNC Promises. This is a breaking change from Next.js 14. The AI MUST await them.

Rule: Always Use Promise Types

✅ CORRECT (Next.js 15):

type PageProps = { 
  params: Promise<{ slug: string }> 
  searchParams: Promise<{ [key: string]: string | string[] | undefined }> 
}

export default async function Page({ params, searchParams }: PageProps) {
  const { slug } = await params;
  const search = await searchParams;
}

❌ WRONG (outdated Next.js 14 pattern — will crash silently):

// DO NOT GENERATE THIS PATTERN
export default function Page({ params }: { params: { slug: string } }) {
  const { slug } = params; // BREAKS: params is a Promise in Next.js 15
}

Rule: generateMetadata Also Uses Async Params

export async function generateMetadata({ params }: { params: Promise<{ slug: string }> }) {
  const { slug } = await params;
  return { title: `Post: ${slug}` }
}

Rule: Layout Components MUST Await Params

export default async function Layout({
  children,
  params,
}: {
  children: React.ReactNode
  params: Promise<{ teamId: string }>
}) {
  const { teamId } = await params;
  return <div>{children}</div>
}
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. yesterday First seen · 56 lines · 0 tokens per session scan A 5fa107fdcf43

Subscribe to this mod's changes

nextjs15-params is a cursor rule published in the GitHub repository vibestackdev/vibe-stack (7 stars, last pushed 2d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 389 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 2026-08-31.