flags

vercel/next.js · Agent Skill

Manages experimental Next.js feature flags, including adding, modifying, and integrating them into code.

Overview

Publisher	vercelOrganization
Repository	vercel/next.js ↗
Skill folder	`flags`
Stars	142,171
Bundled files	1
License	MIT
Last updated	June 23, 2026
Links	Skill source ↗ · Repository ↗

Mozgi check

What we found in the skill files. Details come with a subscription.

Security

low risk · no obvious risks found — the full report shows the details

Compatibility

instructions only — works with most agents

Similar skills

144 similar skills found

Also with subscription

Installation

A skill is a folder with a SKILL.md file. Pick your agent and run the commands in a terminal (macOS, Linux or Git Bash on Windows) from your project root.

Copy the prompt into Claude, Codex or another assistant: it will review the skill and install it for you.

Install the “flags” skill from mozgi.io (https://mozgi.io/skills/flags/) for me.

1. Download the archive: https://mozgi.io/skills/flags/download
   If it fails, take the skill folder from the source: https://github.com/vercel/next.js/tree/canary/.agents/skills/flags
2. Read SKILL.md and the other files. Check the skill is safe: no hidden commands, no sending data elsewhere, no scripts doing something other than described. If anything looks suspicious, stop and tell me.
3. Put the “flags” folder into your agent's skills folder: .claude/skills/ for Claude Code, .agents/skills/ for Codex, .cursor/skills/ for Cursor, .gemini/skills/ for Gemini CLI. Inside the project if we are in one, otherwise in the home folder (~/.claude/skills/ etc.).
4. Make sure <skills folder>/flags/SKILL.md exists.
5. Briefly tell me what this skill does and offer to try it on my task.

If you cannot do a step yourself, tell me what to click or type.

git clone --depth 1 --branch canary https://github.com/vercel/next.js.git /tmp/next.js
mkdir -p .claude/skills
cp -r /tmp/next.js/.agents/skills/flags .claude/skills/flags

Restart Claude Code — the skill appears in the list; call it manually with /flags. For all projects use ~/.claude/skills.

git clone --depth 1 --branch canary https://github.com/vercel/next.js.git /tmp/next.js
mkdir -p .agents/skills
cp -r /tmp/next.js/.agents/skills/flags .agents/skills/flags

Codex looks for skills in .agents/skills from the current folder up to the repo root; call one with /skills or $flags. For all projects use ~/.agents/skills.

git clone --depth 1 --branch canary https://github.com/vercel/next.js.git /tmp/next.js
mkdir -p .cursor/skills
cp -r /tmp/next.js/.agents/skills/flags .cursor/skills/flags

Cursor picks the skill up on start; call it with “/” in Agent chat. Cursor also reads .claude/skills and .agents/skills. For all projects use ~/.cursor/skills.

git clone --depth 1 --branch canary https://github.com/vercel/next.js.git /tmp/next.js
mkdir -p .gemini/skills
cp -r /tmp/next.js/.agents/skills/flags .gemini/skills/flags

Gemini CLI offers to activate the skill when a task matches — you approve it. For all projects use ~/.gemini/skills.

Review the source files

1 file Download Zip

Read SKILL.md and any companion files before deciding whether to install. Click a file to preview it.

SKILL.md contents

Original author text · read-only

Feature Flags

Use this skill when adding or changing framework feature flags in Next.js internals.

Required Wiring

All flags need: config-shared.ts (type) → config-schema.ts (zod). If the flag is consumed in user-bundled code (client components, edge routes, app-page.ts template), also add it to define-env.ts for build-time injection. Runtime-only flags consumed exclusively in pre-compiled bundles can skip define-env.ts.

Where the Flag Is Consumed

Client/bundled code only (e.g. __NEXT_PPR in client components): define-env.ts is sufficient. Webpack/Turbopack replaces process.env.X at the user's build time.

Pre-compiled runtime bundles (e.g. code in app-render.tsx): The flag must also be set as a real process.env var at runtime, because app-render.tsx runs from pre-compiled bundles where define-env.ts doesn't reach. Two approaches:

Runtime env var: Set in next-server.ts + export/worker.ts. Both code paths stay in one bundle. Simple but increases bundle size.
Separate bundle variant: Add DefinePlugin entry in next-runtime.webpack-config.js (scoped to bundleType === 'app'), new taskfile tasks, update module.compiled.js selector, and still set env var in next-server.ts + export/worker.ts for bundle selection. Eliminates dead code but adds build complexity.

For runtime flags, also add the field to the NextConfigRuntime Pick type in config-shared.ts.

Runtime-Bundle Model

Runtime bundles are built by next-runtime.webpack-config.js (rspack) via taskfile.js bundle tasks.
Bundle selection occurs at runtime in src/server/route-modules/app-page/module.compiled.js based on process.env vars.
Variants: {turbo/webpack} × {experimental/stable/nodestreams/experimental-nodestreams} × {dev/prod} = up to 16 bundles per route type.
define-env.ts affects user bundling, not pre-compiled runtime internals.
process.env.X checks in app-render.tsx are either replaced by DefinePlugin at runtime-bundle-build time, or read as actual env vars at server startup. They are NOT affected by the user's defines from define-env.ts.
Gotcha: DefinePlugin entries in next-runtime.webpack-config.js must be scoped to the correct bundleType (e.g. app only, not server) to avoid replacing assignment targets in next-server.ts.

Related Skills

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$react-vendoring - entry-base boundaries and vendored React
$runtime-debug - reproduction and verification workflow

Frequently asked questions

What does the flags skill do?

Manages experimental Next.js feature flags, including adding, modifying, and integrating them into code.

How do I install flags?

Open the “Installation” block on this page and pick your agent — Claude Code, Codex, Cursor or Gemini CLI — for ready-made commands that copy the skill folder to the right place. Or copy the prompt from the “Via assistant” tab and let the assistant review and install the skill.

Which AI models work with flags?

Skills are plain Markdown instructions (the Agent Skills format), so flags works with any agent that reads SKILL.md: Claude Code, Codex, Cursor, Gemini CLI, GitHub Copilot, OpenCode and more. The model loads the instructions only when a task matches the skill's description.

Is flags free?

The skill is published openly by vercel under the MIT license. The skill itself costs nothing — you only pay your AI provider for the tokens you use.

Is it safe to install skills?

A skill is a set of instructions your agent will follow, so read SKILL.md and its companion files before installing. Scripts in the skill folder only run if your agent runs them — keep an eye on what it does and do not grant unnecessary permissions.

How is a skill different from an MCP server or a plugin?

An MCP server or plugin gives the model new tools — code that runs and returns a result. A skill gives it knowledge and process: how to approach a task, which steps to follow and what good output looks like. It needs no server or API key.

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