---
title: Watch Agents Build in Real Time
summary: Agents run a full development workstation in a sandboxed container and serve what they build straight to your browser through a secured live preview.
date: 2026-09-09
---

# Watch Agents Build in Real Time

Agents run a full development workstation in a sandboxed container and serve what they build straight to your browser through a secured live preview.

## What an agent can actually run

Beyond calling tools, an agent gets a full, sandboxed development workstation for any task that needs one: Python with pip, Node.js 20 with npm, yarn, and pnpm, git, curl, and a C toolchain for building native packages. Heavier tools, a headless browser, ffmpeg, OCR, and PDF utilities, install on demand rather than bloating every environment by default.

## Starting a live preview

When an agent starts a dev server or any long-running process, it gets back a live preview URL you can open immediately: the same running process, not a screenshot or a description of one. That process can be stopped on request, and everything currently running, with its preview link, is listed on demand.

## How the preview stays secure

The sandboxed container that runs your agent's code has no path to the internet and no path to your browser directly. A dedicated preview proxy bridges the two, and three things make that safe:

- **Authenticated per request**: every request to a preview carries a signed token; the organization in that token has to match the organization that owns the running service, or the request is refused outright.
- **A circuit breaker, not endless retries**: three consecutive failed connections to the service trip the breaker. The proxy stops trying, tells the frontend the service crashed, and shows a clean "Service Stopped" response instead of hanging. A successful response resets it automatically the moment the service recovers.
- **URL rewriting**: a web app's own absolute paths (like `/static/js/main.js` or `/api/data`) are rewritten so they still resolve correctly even though the app isn't actually running at the root of your browser's address bar.

## Visual decisions, not just text

For choices with a visual answer, like picking a layout or a color direction, an agent can present 2 to 4 options side by side, each with its own preview, instead of describing them in a paragraph and asking you to imagine the difference.

## Related

- [Planning](/en/docs/features/planning): the plan an agent follows before it starts building anything
- [Built-In Tools](/en/docs/guides/built-in-tools): every capability, including the ones described here, an agent has without any integration connected