690326:2212 Fixing Refactor ADR-019 Naming convention uuid #08

specs/99-archives/skills-backup/next-best-practices-original/async-patterns.md

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+# Async Patterns
+
+In Next.js 15+, `params`, `searchParams`, `cookies()`, and `headers()` are asynchronous.
+
+## Async Params and SearchParams
+
+Always type them as `Promise<...>` and await them.
+
+### Pages and Layouts
+
+```tsx
+type Props = { params: Promise<{ slug: string }> };
+
+export default async function Page({ params }: Props) {
+  const { slug } = await params;
+}
+```
+
+### Route Handlers
+
+```tsx
+export async function GET(request: Request, { params }: { params: Promise<{ id: string }> }) {
+  const { id } = await params;
+}
+```
+
+### SearchParams
+
+```tsx
+type Props = {
+  params: Promise<{ slug: string }>;
+  searchParams: Promise<{ query?: string }>;
+};
+
+export default async function Page({ params, searchParams }: Props) {
+  const { slug } = await params;
+  const { query } = await searchParams;
+}
+```
+
+### Synchronous Components
+
+Use `React.use()` for non-async components:
+
+```tsx
+import { use } from 'react';
+
+type Props = { params: Promise<{ slug: string }> };
+
+export default function Page({ params }: Props) {
+  const { slug } = use(params);
+}
+```
+
+### generateMetadata
+
+```tsx
+type Props = { params: Promise<{ slug: string }> };
+
+export async function generateMetadata({ params }: Props): Promise<Metadata> {
+  const { slug } = await params;
+  return { title: slug };
+}
+```
+
+## Async Cookies and Headers
+
+```tsx
+import { cookies, headers } from 'next/headers';
+
+export default async function Page() {
+  const cookieStore = await cookies();
+  const headersList = await headers();
+
+  const theme = cookieStore.get('theme');
+  const userAgent = headersList.get('user-agent');
+}
+```
+
+## Migration Codemod
+
+```bash
+npx @next/codemod@latest next-async-request-api .
+```