I asked an agent to make a product video. It wrote HTML and rendered an MP4 - Dota Companion

I needed two videos for a Chrome extension I built: a promo and a walkthrough. I did not want to open a video editor.

So I used HyperFrames — HeyGen's open-source (Apache 2.0) HTML-to-MP4 framework. Compositions are plain HTML and CSS. No JSX, no bundler, no build step. Timing lives in data attributes; motion comes from GSAP. A headless Chrome seeks the timeline frame by frame and FFmpeg encodes it.

That design matters for one specific reason: an agent can read and edit a plain HTML file. It cannot meaningfully iterate on a timeline in a GUI.

Both videos below were authored as HTML, narrated with a local TTS model, and rendered locally. Here's what came out, then the three things that actually cost me time.

The promo (29s)