Twain
Twain vs Lettera
Lettera, from the team behind Bear, edits Markdown files on disk in a native editor. It is the closest new app to Twain in intent, and the differences are specific.
Not shipped yet. The signed, notarised build is in progress; the download and checkout open together when it's ready.
The short version
Lettera is the closest new app to Twain in intent. It is built by Shiny Frog (the Bear team) on the Bear 2 engine, it opens files and folders on disk in place, and, going by its own screenshots, it is aimed at people reviewing AI-written Markdown. That is Twain's audience. Three things separate them today. Lettera is macOS 26 (Tahoe) only by design, so it will not run on the Sonoma and Sequoia Macs most people are on. It is in a waitlisted beta with no announced price, so it cannot be downloaded or bought yet. And it has none of the repo-shaped features: no Quick Look, no MDX, no CLI, no review tooling. Twain runs on macOS 14 and later, ships all of those, and 1.0 is out now with a free viewer and a 7-day Pro trial.
you are on macOS 14 or 15 (most Macs today), your files include MDX or live in a documentation repo, or you want Quick Look, review tooling and an app you can download today.
you are on macOS 26, you want the Bear 2 editing engine, and writing feel matters more to you than Finder integration, MDX or review tools.
At a glance
Twain next to Lettera on the things that decide it. Every fact is dated against Lettera's public material.
| Twain | Letteraverified 17 Jul 2026 | |
|---|---|---|
| Opens files / folders on disk, in place | Yes | Yes |
| Minimum macOS | macOS 14 (Sonoma) | macOS 26 (Tahoe) only, by design |
| Finder Quick Look | Yes (MD + MDX) | No |
| MDX | Yes: safe rendering | No |
| Maths / Mermaid | KaTeX and Mermaid | MathJax and Mermaid |
| Review tooling (diagnostics, diff, annotations, AI report) | Yes | No |
| CLI / MCP for agents | CLI (check, render, export) and read-only MCP ship in the app; separate packages pending | No CLI or MCP |
| Editor | Block-based visual editor (Pro) | Bear 2 engine |
| Frontmatter | Rendered as a key-and-value card | No (open request) |
| Release status | Shipped: 1.0, 31 July 2026 | Public TestFlight beta, waitlist full |
| Price | Free viewer; $19 Pro once (7-day trial) | Unannounced |
Side by side
What Twain has that Lettera doesn't
- Runs on macOS 14 and later, Apple silicon or Intel. Lettera requires macOS 26 (Tahoe) by explicit design choice, so it cannot run on the Sonoma and Sequoia Macs that are most of the installed base.
- Finder Quick Look for Markdown and MDX. Lettera has none.
- MDX rendering. Lettera renders CommonMark, not MDX.
- Review tooling built for documentation: diagnostics, anchored annotations, a rendered diff, and a Copy Report for Agent. Lettera is an editor without these.
- A CLI (check, render, export) and a read-only MCP server ship in the app, so agents and CI can check what a document renders to. Lettera has neither.
- Available today, at a stated price: the free viewer downloads now, and Pro is $19 once with a 7-day trial. Lettera's beta is waitlisted and its pricing is unannounced.
What Lettera has that Twain doesn't
- Editor engine. Lettera is built on the Bear 2 editor engine by Shiny Frog, the studio behind Bear.
- Native-macOS design. Lettera commits to stock macOS Tahoe styling.
The closest app to Twain, and where it stops
Lettera and Twain agree on the important first principle: your Markdown should stay in files on disk, not in a database. Lettera even courts the same user we do; its own screenshots are full of files named for Claude and AI instructions, and reviewers use it to open agent-written Markdown. The difference is what happens next. Lettera gives you an editor for that file. Twain pairs its own block-based editor with Quick Look, MDX rendering, diagnostics, a rendered diff and an agent report, which is the reviewing layer Lettera has not built.
macOS 26 only is a real gap
Lettera requires macOS 26 (Tahoe), a decision its developers made deliberately to avoid supporting older systems. Every Mac still on Sonoma or Sequoia (macOS 14 or 15), which is most of them for at least the next year, cannot run Lettera at all. Twain targets macOS 14 and later. If you are not already on Tahoe, this alone decides it.
A moving target
Lettera is early and still changing: its beta added Mermaid and typography settings within two weeks. Frontmatter and working wikilinks are requested and may come; Twain renders frontmatter as a key-and-value card today. This comparison reflects the beta as of mid-July 2026, and we re-check it monthly. What is unlikely to change soon is the shape of the app: an editor first, on the newest macOS, from a team whose centre of gravity is writers rather than documentation repos.
Questions
Can I download Lettera today?
Not easily. Lettera is in a public TestFlight beta whose waitlist is full, so new testers join a queue, and there is no released version to buy. Twain 1.0 shipped on 31 July 2026: the free viewer downloads immediately, and Pro has a 7-day trial.
What macOS does Lettera need?
macOS 26 (Tahoe) only, by the developers' explicit choice. It will not run on macOS 14 (Sonoma) or 15 (Sequoia). Twain runs on macOS 14 and later.
Does Lettera do MDX or Quick Look?
No to both. Lettera renders CommonMark Markdown and has no Finder Quick Look or MDX support. Twain provides both.
Is Lettera made by the Bear team?
Yes. Lettera is built by Shiny Frog, the studio behind Bear, on the same Bear 2 editor engine. Twain pairs its own block-based editor with the layer Lettera has not built: Finder Quick Look, MDX rendering, review tooling and a CLI.
Verification date shown reflects Lettera's public material as of that day; capabilities and prices can change. Lettera is in beta, so we re-check this page monthly. Twain facts describe what the app does today; see the full comparison tables and all comparisons. Prices are in USD.
Try Twain
The free viewer, with a 7-day Pro trial built in.
Not shipped yet. The signed, notarised build is in progress; the download and checkout open together when it's ready.