Live preview

When an agent is working on a web app, you don't have to pull the branch to see it. Open the Preview tab and FlareCode starts the project's dev server inside the sandbox and shows it running, live, on a private URL.

Open a preview

Click the Preview tab in a session. The first time you open it, FlareCode starts the dev server automatically — no setup. It keeps running while you switch tabs; it stops when you close it or the agent is paused.

You don't normally configure anything. FlareCode detects the framework and package manager, installs dependencies if needed, runs the dev server, and proxies the port to a private https URL that renders in the panel.

What's auto-detected

• Frameworks — Next.js, Vite, SvelteKit, Nuxt, Astro, Remix, Angular, Create React App, and any project with a dev or start script (plain Node). A static site with an index.html (root, public/, dist/, or src/) is served directly.
• Package manager — pnpm, npm, Yarn, or Bun, from your lockfile (defaults to pnpm).
• Monorepos — if the repo root has no app but has workspaces, FlareCode picks the frontend workspace (prefers apps/, then conventional names like web, app, frontend).

Need something specific? You can override the command and port when you start the preview.

Troubleshooting

• "No dev server detected." The repo has no dev/start script and isn't a framework FlareCode recognizes. Add a dev or start script to package.json, or — for a static site — make sure there's an index.html and it'll be served automatically.
• It's taking a while to start. First boot installs dependencies and waits for the server to bind — up to about 90 seconds, longer for big installs. Leave the tab open; it polls and shows the URL as soon as the server answers.
• "Your browser can't reach the preview." FlareCode automatically falls back to a tunnel if the direct URL doesn't resolve in your browser. If both fail, the app is running in the container but your network is blocking the connection — rare, and usually a corporate proxy or certificate issue.
• A paused or just-resumed agent. Opening a preview wakes the agent automatically. The first start right after an idle pause is slower while the encrypted workspace restores.
• The page went blank or stopped responding. If the dev server crashes or the container goes idle, the preview reconnects and relaunches it for you, then reloads the frame.

Preview is not the PR

A preview is for seeing the work in progress — it runs in the sandbox and is reachable only by you. It's separate from the change itself, which still lands as a Pull Request you review and merge. See Submit a task.

Related

• Interactive vs goals — the two ways to drive an agent.
• Security model — how the sandbox and its network are bounded.