Flags SDK skill

---
name: vercel-flags
description: >
  Feature flags, A/B tests, and gradual rollouts with Vercel Flags, in any app or framework.
  Use whenever the user is planning, adding, changing, or cleaning up a feature flag, toggle, kill switch,
  experiment, percentage rollout, or targeting rule, or wants to gate or hide a feature for some
  users, even before a library or provider is chosen. Covers choosing an integration (Flags SDK,
  `@vercel/flags-core`, OpenFeature), the Vercel dashboard, the `vercel flags` CLI (create, inspect,
  set, split, rollout, rules, segments, evaluations, archive, connections), Project Connections, OIDC vs SDK keys, `FLAGS_SECRET`, and
  Flags Explorer overrides. For `flag()` declarations, adapters, precompute, and the Flags Explorer
  endpoint in Next.js or SvelteKit code, load the `flags-sdk` skill.
---

# Vercel Flags

Vercel Flags is Vercel's feature flags platform. Flags are created and managed in the Vercel dashboard or with the `vercel flags` CLI, evaluated server-side in your app, and switched per environment (Development, Preview, Production) without a redeploy.

- Docs: https://vercel.com/docs/flags
- CLI reference: https://vercel.com/docs/cli/flags

Use this skill to decide how a feature should be flagged, to create and change flags, and to run rollouts and experiments. Write app code with the skill that matches the stack (see [Choose an approach](#choose-an-approach)). Do not leave CLI steps as "next steps" for the user; execute them yourself.

## Route the request

- **Planning** ("put this behind a flag", "roll this out to 10%", "A/B test the pricing page", "add a kill switch"): follow [Plan a flag](#plan-a-flag), then [Choose an approach](#choose-an-approach).
- **Create or manage a flag with no code change** (create, inspect, enable, set, split, rollout, rules, archive): follow [Manage flags with the CLI](#manage-flags-with-the-cli). This needs an authenticated CLI, not SDK packages, Toolbar, Flags Explorer, or `.env.local` (except `vercel flags override`, which reads `FLAGS_SECRET`).
- **Share flags between projects**: follow [Project Connections](references/cli.md#project-connections) to connect projects in the same team, then configure the consumer application.
- **Clean up or remove a flag** ("remove this flag", "clean up stale flags", "inline this flag"): follow [references/cleanup.md](references/cleanup.md), then [Lifecycle and safety](references/cli.md#lifecycle-and-safety) before archiving.
- **Add a flag to an app that already uses the Flags SDK** (`flags` in `package.json`): load the `flags-sdk` skill right away; it creates the flag on Vercel and declares it in code.
- **Implement in code otherwise**: follow [Choose an approach](#choose-an-approach) and load the matching skill or reference. Inside an app repository, treat an ambiguous request as plan, create, and implement.

## Choose an approach

Check the project before writing code.

- **Already using another flag provider** (Statsig, LaunchDarkly, PostHog, GrowthBook, and so on): keep it. On Next.js or SvelteKit, the Flags SDK connects to it through an adapter; load the `flags-sdk` skill. On any other stack, use the provider's own SDK. Rollouts, targeting, and experiments for that provider are configured in its own dashboard, not with `vercel flags`; the CLI and lifecycle sections of this skill do not apply.
- **No provider yet**: use Vercel Flags. Pick the integration by stack ([SDKs](https://vercel.com/docs/flags/vercel-flags/sdks)):
  - **Next.js or SvelteKit**: the Flags SDK (`flags` + `@flags-sdk/vercel`). It adds Flags Explorer integration and precompute for static pages. Load the `flags-sdk` skill. If it is not available, suggest `npx skills add vercel/flags@flags-sdk` (do not auto-install).
  - **Any other framework or a plain server** (for example Express): `@vercel/flags-core`. See [Other frameworks](#other-frameworks).
  - **The user wants provider portability or already uses OpenFeature**: the Vercel Flags OpenFeature provider ([Using OpenFeature with Vercel Flags](https://vercel.com/docs/flags/vercel-flags/sdks/openfeature)).

The dashboard and the `vercel flags` CLI work the same for every integration.

## Plan a flag