@vercel/next-browser

@vercel/next-browser

Programmatic access to React DevTools and the Next.js dev server. Everything you'd click through in a GUI — component trees, props, hooks, PPR shells, build errors, Suspense boundaries — exposed as shell commands that return structured text.

Built for agents. An LLM can't read a DevTools panel, but it can run next-browser tree, parse the output, and decide what to inspect next. Each command is a stateless one-shot against a long-lived browser daemon, so an agent loop can fire them off without managing browser lifecycle.

Getting started

You don't install or run this directly. Your agent does.

• Add the skill to your project. From your Next.js repo:

  npx skills add vercel-labs/next-browser
  

  Works with Claude Code, Cursor, Cline, and others.

• Start your agent in that project.

• Type /next-browser to invoke the skill.

• The skill checks for the CLI and installs @vercel/next-browser globally if it's missing (plus playwright install chromium).

• It asks for your dev server URL and any cookies it needs, opens the browser, and from there it's pair programming — tell it what you're debugging and it drives the tree, navigates pages, inspects components, and reads errors for you.

That's the whole flow. Run npx skills upgrade later to pull updates.

The rest of this README documents the raw CLI for the rare case where you're scripting it yourself.

Manual install

pnpm add -g @vercel/next-browser

Requires Node >=20.

Commands

open <url> [--cookies-json <file>]  launch browser and navigate
close              close browser and daemon

goto <url>         full-page navigation (new document load)
push [path]        client-side navigation (interactive picker if no path)
back               go back in history
reload             reload current page
capture-goto [url] capture loading sequence (PPR shell → hydration → data)
restart-server     restart the Next.js dev server (clears fs cache)

ppr lock           enter PPR instant-navigation mode (requires cacheComponents)
ppr unlock         exit PPR mode and show shell analysis

tree               show React component tree
tree <id>          inspect component (props, hooks, state, source)

viewport [WxH]     show or set viewport size (e.g. 1280x720)
screenshot         save full-page screenshot to tmp file
eval <script>      evaluate JS in page context

errors             show build/runtime errors
logs               show recent dev server log output
network [idx]      list network requests, or inspect one

License

MIT