I tried Bento for a few slide decks.
Disclaimer: slides have never been my strong suit.
It's an interesting project. But when I had an agent one-shot a presentation, the slides flowed poorly and the content was shallow.
I used a Codex harness pointed at Bento's agents.md. It produced a decent-looking deck. I ran the same prompt without the Bento guidance, and the same model produced HTML slides — with much better content and flow.
My hypothesis: agents.md's context. Its instructions are all about formatting slides for visual spectacle. But before you can format slides to look good, you need content worth presenting.
Putting agents.md up front shifts the agent's attention toward formatting the deck — before any content or flow is in place.
Next: start with existing HTML or Markdown, then have agents convert it to Bento.