Next.js

Install

pnpm add @flagctl/next

FlagBoundary

import { FlagBoundary } from '@flagctl/next';

export default function Page() {
return (
  <FlagBoundary flag="checkout.v2" fallback={<OldCheckout />}>
    <NewCheckout />
  </FlagBoundary>
);
}

Evaluates on the server. Streams the on-branch only — clients never receive the off-branch markup.

Sticky bucketing

@flagctl/next reads the user identity from a configurable source (cookie, header, session) and hashes it with the flag key to assign a sticky bucket per percent rollout.