What problem does it solve? Feature flag APIs change frequently and outdated training data leads to broken implementations. This Skill provides current guidance for the Vercel Flags platform and the flags SDK (v4+), covering flag definition, provider adapters, Flags Explorer setup, and precompute patterns so you avoid deprecated APIs like @vercel/flags v3. ## Core Features & Use Cases - Flag Definition & Evaluation: Define boolean and multi-variant flags with flag() from flags/next or flags/sveltekit, with server-only evaluation and no call-site arguments. - Provider Adapters: Connect Vercel Flags via @flags-sdk/vercel or third-party providers (LaunchDarkly, Statsig, GrowthBook, PostHog) through @flags-sdk/* adapters, including an OpenFeature bridge. - Flags Explorer & Precompute: Set up the .well-known/vercel/flags discovery endpoint for toolbar overrides, and use precompute patterns to serve static personalized page variants via middleware. - Use Case: You are rolling out a redesigned checkout to 10% of users. Define a show-new-checkout flag with the Vercel adapter, configure percentage targeting in the Vercel dashboard, and let developers override it locally through Flags Explorer. ## Quick Start Ask the assistant to define a boolean feature flag using the flags/next SDK with the Vercel adapter and wire up the Flags Explorer discovery endpoint in a Next.js App Router project.