Apple Silicon
Built for M series Macs, where it opens in about a second and then gets out of the way. Intel has been finished on the Mac for years and we saw no reason to pretend otherwise.
Open source
Not everything we build is for sale.
Eldris maintains MacDown SE, the Apple Silicon continuation of MacDown, the native Markdown editor a lot of Mac users have had open for years. It is still MIT licensed, it still has nothing in it that phones home, and it now speaks MCP, so the AI tools you already use can work inside it.
Why we did it
A good app should not die of neglect.
MacDown has been the quiet default for writing Markdown on a Mac for a long time. It is fast, it is native, and it never asked anybody for an account. Active development stopped in 2020, and the distance between the app and the operating system underneath it grew with every macOS release.
We use it. A fair amount of the firm's writing goes through it, including notes behind OOMU. When something you rely on every day stops moving, you either settle for something worse or you pick it up.
We picked it up.
What changed
Modernized, not rewritten.
The point was to keep the app people already like and repair what had gone stale underneath it. Nothing was redesigned for the sake of looking new.
Still AppKit, still not Electron
A native macOS application rather than a browser engine wearing an app icon. The memory use is the tell.
MCP built in
A Model Context Protocol server inside the editor, so AI tools can read and change what you have open. More on that below.
Current toolchain
Rebuilt against modern SDKs so it keeps working as macOS moves, instead of accumulating another five years of drift.
Nothing phones home
No telemetry, no analytics, no sign-in. It works with the network switched off, which is the correct behavior for a text editor.
Still MIT
The license did not change and will not. Read it, fork it, ship it, sell it. That was the deal when we found it and it is the deal we are passing on.
The useful software of the last twenty years was given away. Some of the next twenty should be too.
MCP
The editor your AI tools can actually reach.
MacDown SE runs a Model Context Protocol server. MCP is an open standard, so this is not an integration with one company's assistant. Anything that speaks MCP can drive the editor: Claude, Codex, Cursor, Gemini, and whatever ships next.
- It can read what is open An assistant sees the document as it stands in the window, not a copy you remembered to paste somewhere else first.
- It can change the text in place Edits land in the buffer you are working in, in the window you are already looking at, where you can read them and undo them.
- It can render the preview A tool can produce the HTML output and check how a document actually comes out, rather than reasoning about the source and hoping.
- An open standard, not a partnership There is no vendor deal behind this and none is needed. If a client supports MCP, it works, and nobody has to ship an update to bless it.
Why a firm does this
It is the same argument as the product.
Eldris builds OOMU on a plain position: AI should work through the software people already have, on the machine they already own, without a meter running in the background. MacDown SE is that position in miniature. An editor people have used for years, still free, now able to work with whichever assistant they choose rather than the one that bought the integration.
It is also how a firm earns the right to have opinions about software. Plenty of people discuss open source in a governance deck. Fewer maintain any. The code is there to read, which is a more useful credential than a slide.
The repository is the argument.
Go and take it.
MIT licensed, free, and no account anywhere in it. If it is useful to you, it is yours. Bugs and requests belong in the issue tracker, where everyone can see them.