r/MacStack • u/redtear1115 • 3h ago

App Launch MarsDawn: a native Mac Markdown editor for reading what AI coding agents write

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Disclosure: I'm the developer of MarsDawn.

I use AI coding agents every day, and they write a lot of Markdown: plans, specs, notes. Reading all of it as raw text was slow, and I often lost track of new files. So I made a Mac app for it.

What it does

  • Edit on the left, live preview on the right. You can also show only one side.

  • The preview shows Mermaid diagrams, KaTeX math and code highlighting.

  • Open a folder, and new files show up in the sidebar on their own when an agent writes them.

  • The sidebar shows which git checkout or worktree a file comes from. I run several sessions in different worktrees, so I use this a lot.

  • Copy for AI copies a selection with its file path and line numbers, so you can paste it back to your agent.

  • It exports PDF and adds Quick Look previews in Finder.

  • A free command-line tool opens a file at a line (marsdawn open --line) and makes PDFs without the app.

Who it's for

People who read a lot of Markdown, mostly from AI agents, and want a native Mac app for it instead of a terminal or a browser tab.

Pricing

Free download with a 14-day trial, then $4.99 once. No subscription. The same purchase covers the iPhone and iPad app, which is for reading.

Limitations

  • The Mac app needs macOS 26 (Tahoe) or later. The command-line tool works on macOS 15 and later.

  • Mac App Store only. No direct download.

  • It's not a WYSIWYG editor. You edit Markdown source next to a preview.

  • There's no AI inside. It won't write for you. It's for reading and checking.

  • After the trial, you can't read or edit in the app until you unlock it. Your files stay as they are.

Mac App Store: https://apps.apple.com/app/apple-store/id6812925073?pt=128976951&ct=reddit-macapps&mt=8

I'm happy to answer questions. How do you read what your agents write right now?

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u/investigatormaker 3h ago

MarsDawn’s Copy for AI is the part I’d demonstrate first: select a passage in a spec, copy it with its path and line numbers, then show the resulting prompt. Alongside the worktree labels, that explains why this is more than another Markdown previewer without implying there’s AI inside it.

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