底本 teihon · the base text of an edition the authoritative copy every variant is recorded against
Two panes over one document. Type in either and the other keeps up — and when something else rewrites the file underneath you, Teihon shows you exactly what moved.
Free while in beta · macOS 12+ and Windows 10+
Change review
When a file changes on disk, the new text arrives in the open window and every altered line is marked — in both panes, at the same time. Step through the changes one by one, reveal what a line used to say, and clear the marks when you have read them.
No diff view to open, no second window. The document you are reading is the document that changed.
Terminal
Several shells at once, as named tabs, opening in the folder you have open rather than wherever you happened to be. One for the agent, one for the dev server, one for git.
Real shells, with your own profile and your own aliases — not a command runner pretending to be one.
Markdown source on the left, a fully editable rendered view on the right. Edit either. The caret is mirrored in the pane you are not typing in, so you never lose your place.
Open a folder and see every document in it, each marked with what git would say about it — modified, added, untracked. You can tell at a glance what is not committed yet.
A fenced mermaid block draws itself. Sequence diagrams,
flowcharts, state machines — written in the document, so an agent can
revise the picture along with the paragraph that explains it.
Search across every document in the folder, follow links between them, and see which specs point at the one you are reading.
Autosave is on. There are no unsaved-changes dots and no dialog when you close a window, because there is nothing left to write.
No account, no telemetry, no cloud. Your documents are files in a folder, and they stay that way.
Free while in beta. Updates arrive quietly and install when you say so.
Open a folder of specs and point an agent at it.