Lettera - Markdown Editor for macOS
The Context
Lettera is a Markdown editor for macOS by Shiny Frog, the team behind Bear. It carries the editing experience people know from Bear – live styling, tables, inline images, code, math – but points it at ordinary files: a single .md document you opened for a quick edit, or a folder on disk that becomes a workspace with a directory sidebar.
The project was known as “Panda” during its long incubation as Bear’s editor testbed, and became Lettera when it grew into an app of its own. It went into public beta in June 2026.
I joined the team in December 2025 as a contract macOS developer.
Technical Challenges
Text editing is the part of app development where the invisible details decide everything. A Markdown editor that styles while you type is not a document viewer with a text box; it is a text engine with opinions, and every one of those opinions has to survive selection, undo, IME input, and a 30,000-word document.
But this app had a good editor from the start: we inherited Bear’s editing engine and “just” needed to figure out the file handling.
Just. Heh.
The problems that shape this kind of app:
- The file is the truth. Editing files in place instead of a database means the app has to cope with everything the file system can do to a document while it is open: renames, moves, external edits from another editor, sync clients rewriting bytes underneath you. This can go wrong in many ways.
- Editor behavior nobody notices when it is right. Typewriter mode, caret placement across styled ranges, scrolling that lands where the writer expects. I had already written up the overscrolling math for typewriter mode years before from my own editor work; revisiting those notes for this project was a small pleasure. I yet have to convince the world of the one true formula, but we’re getting there, empirically.
The codebase is Swift with AppKit and TextKit 1 (never 2!) under Swift 6’s strict concurrency, so the text pipeline has to be explicit about actor isolation rather than relying on “it happens on main anyway.”
Team Dynamics
Lettera is Shiny Frog’s app. It is built by a small, tight-knit team that has spent a decade on one editor and knows exactly which details are worth arguing about. The latest new hire works with the team for 6 years already, so it’s not a fast-growing team, and people who work there tend to stick.
That is a different mode of work from my own products, where I decide and ship. Here the value I add is being a second pair of experienced macOS hands on a codebase with a very high bar for feel – proposing, prototyping, and then deferring to a team that has earned its opinions. The decision process is not formal. It’s everything but. Developing a shared sense of taste is part of becoming a team member.
Personal Reflections
I have spent years building on plain text: The Archive, the Zettelkasten work, my own notes. The premise of Lettera – Bear’s editor on top of a folder you own – is close to what I want to use everyday. There just was no general-purpose Markdown editor on Mac that does things well, yet, in a “get out of my way” style like TextEdit.
The other lesson is about pace. Working on someone else’s product means shipping at their cadence and their standard of done. On a text editor, that standard is unusually high, and watching how much care goes into behavior users will never consciously notice has changed how I judge my own editors.
Impact
Lettera entered free public beta via TestFlight in June 2026, with a feedback thread on community.bear.app. It gives writers who live in plain text an editor with Bear’s polish that never asks them to move their files into anyone’s database.