Composer began as one of those "wouldn't it be nice if" conversations with a presenter who enjoyed the stream-of-conscious nature of writing their shows out in Markdown, liked and used many of the dedicated Markdown-based tools built specifically for that job, but found themselves always coming back to Keynote for the actual show itself – and having to tediously transfer each slide over by hand to dial it all in again.

Other projects have worked toward bridging this gap over the years, but they've always done so from a very Markdown-centric POV, requiring Theme-level tweaks Keynote-side to get a simple Title + Bullets slide up and running – nothing that could really scale toward the diversity of a full pitch kit in an actual production setting. So I came from the opposite direction: what would we need to do to let Keynote itself define those terms and conventions? How could we use Markdown to direct targeted production objectives in Keynote in a predictable, repeatable way – in whatever theme I pointed it at?

Composer's what I came up with: a deterministic orchestration layer that maps structured Markdown input into custom AppleScript build routines that construct your presentation in Keynote for you. A production-facing bot that follows your specifications, targets your own themes and customizations, and doesn't invent anything along the way.

It uses Latent Intent to map your script to the appropriate standard Keynote layouts (an h2 Title element + a List element = a Title + Bullets Layout, broadly speaking), or to layouts you specify yourself with tags, and generates a custom Build plan. Build Script outputs are open, native AppleScript files for MacOS Script Editor: so you can examine every command or make your own edits before runtime, retaining full control of final execution on your Mac.

It uses standard Keynote conventions and understands layouts through what's called a Theme Target Manifest (TTM) – which describes the layouts, objects, and placeholders that AppleScript can target in any particular theme. So whenever you do want an LLM's assistance drafting a show or building something fairly complex, you can teach it precisely how your system or specific slides are actually structured.

Still web-based for now, completely Free to use (an Account is required), doesn't require anything to be installed to get up and running, and works with any standard Keynote theme in any language Keynote supports. No retention, tracking, or any of that nonsense: just a bot ready to push some pixels in Keynote whenever you need a hand.

I'm actively evaluating whether it might make sense to push all of this toward an MCP-type API to open it up a bit more on the LLM side of the equation – likewise exploring refactoring toward a Mac app to clean up the clutter of Browser/Script Editor/Keynote windows a bit.

Very open to feedback/criticism – have been running a fairly quiet Beta among a pretty close-knit group over this past year, but starting to open things up a bit more broadly of late and especially curious as to how this all resonates with folks outside my usual bubble.

Show HN: Composer – A Markdown-driven automation engine for Apple Keynote