HeartBeatAgents

Watch Agents Build in Real Time

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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.

  • Planning: the plan an agent follows before it starts building anything
  • Built-In Tools: every capability, including the ones described here, an agent has without any integration connected