SuperMD is a native Markdown editor written in Rust on GPUI, the UI framework behind Zed. Files stay plain CommonMark on disk. Syntax markers hide while you write and reappear when the cursor touches them; tables, images and Mermaid diagrams render in place and turn back into source when you edit them.
It is the lab’s writing tool rather than part of the agent stack. I spend a lot of my day in Markdown, and it is also where I test a Rust-native UI stack against the needs of a real application.
What it does:
- Wiki links, backlinks, tags and a graph view of the workspace, all computed from the plain files with no database.
- A diff of the open file against git HEAD, read with pure-Rust git, without staging or committing anything.
- Plugins as WebAssembly components, sandboxed with no filesystem or network access unless you consent per plugin (and per domain), and cut off if they hang for 2 seconds. Fourteen ship first-party.
- Autosave with atomic writes, per-session backups, and detection of external changes that never silently overwrites a file.
The editing core (buffer, selection, undo, styling, display transform) is pure Rust under a test suite, and the GPU shell stays thin. CI enforces a 90% line-coverage floor. There is also a Mac App Store build, which is sandboxed.
The README calls it “early and moving fast”, built as a working editor first and a product second. macOS is the main platform. Linux and Windows builds are newer, and the Windows builds are not yet code-signed.