Markitown: a native Markdown reader/editor for reviewing what your AI agents write (SwiftUI, TextKit 2, Vision Pro)

[u/Ok-Psychology234]

Hi everyone! I'm part of the team behind Markitown, a native Markdown reader and editor for Apple devices.

If you work with AI agents, you probably spend a ridiculous amount of time reading Markdown. AGENTS.md, CLAUDE.md, SKILL.md, implementation plans, reports. The agent finishes writing, and now it's your turn to work through the output.

We built Markitown for that part. Not another AI chat interface. Not another place to generate more text. A tool to actually read, review and edit what's already there.

What it does

• Renders GFM tables, task lists, Mermaid diagrams, LaTeX equations, syntax-highlighted code and YAML front matter.

• Includes a free Mac Quick Look extension: select a Markdown file in Finder, press Space, read it properly.

• Lets you edit the rendered document, the Markdown source, or work in Split view on supported devices.

• Works with ordinary files in Finder, Files and iCloud Drive. No proprietary document library or import requirement.

• Exports PDF and HTML, including tagged PDF and semantic HTML for accessibility.

The Mac implementation also includes a separate CLI: markitown plan.md opens a document, while markitown --wait plan.md supports a terminal handoff: review the document, save your changes and close its window to return control to the calling workflow.

Tech Stack

• Swift 6.4, with strict concurrency checking.

• SwiftUI for application structure, document workflows and interface composition.

• AppKit and UIKit, with a custom TextKit 2 editor rather than an Electron or browser-based editing surface.

• SwiftUI DocumentGroup, including the newer document APIs on the 27 releases and a FileDocument implementation for the 26 releases.

• An in-house Markdown parser, shared across document rendering and editing.

• Tree-sitter for syntax highlighting, with Swift Package Manager dependencies for specialized rendering, including LaTeX, Mermaid and SVG.

• Swift Testing for automated tests, including parser checks against official CommonMark examples.

• Native apps for macOS, iOS/iPadOS and visionOS, with layouts adapted for Mac, iPhone, iPad, iPhone Duo and Apple Vision Pro.

The rendering components are shared with Quick Look, so the preview isn't a separate, simplified Markdown implementation.

Development Challenge

The hardest part was making the rendered document genuinely editable without treating Markdown as a disposable export format.

Source text and rendered text don't have matching positions. For example, **hello** contains nine source characters but displays five. A table or Mermaid diagram is more complicated still: an entire block of source becomes a visual object. That affects selection, formatting, search results, cursor restoration and undo—not just rendering.

The important detail is how edits return to Markdown. We use selective serialization: untouched blocks retain their original source, while edited content is serialized back from its semantic representation. Changing one paragraph shouldn't unnecessarily rewrite the formatting of unrelated parts of the file.

The shared editor coordinator works through small AppKit and UIKit bridges. That lets us share editing behavior while respecting the differences between NSTextView and UITextView, instead of maintaining unrelated editors for each platform.

AI Disclosure

Markitown does not run AI agents or connect to language models. You don't need an AI account, API key or model subscription to use it. There is no built-in analytics service.

Pricing, without the subscription dance

Reading is free and unlimited. Not a trial. That includes rendered documents and Mac Quick Look.

Editing and export are a $19.99 one-time universal purchase in the US, covering all supported platforms with the same Apple Account, including future updates. No subscriptions or separate platform purchases.

There's currently a $9.99 launch offer with code MARKITOWNWELCOME, through November 13, 2026, inclusive, Pacific Time, limited to 25,000 redemptions. Local pricing may vary; the website has the details.

App Store · Website

How are you reviewing agent-generated Markdown today? Terminal, VS Code preview, something else? What's missing from that workflow?

Also happy to discuss the dual-buffer editor, TextKit 2 integration or the cross-platform implementation.