Collaborative editing for Matra. No CRDT, no dependency — the engine can already rebase a step over someone else's edit, so this is a version counter and a transport on top of that.

npm i @matrajs/core @matrajs/collab

import { collab, sendableSteps, getVersion } from '@matrajs/collab'

const editor = createEditor({
  extensions: [...starterKit, collab({ clientId })],
  content,
})

// Send what we have; the authority accepts only if we are current.
const sendable = sendableSteps(editor)
if (sendable) {
  const accepted = await post(sendable)
  if (accepted) editor.commands.confirmCollabSteps(sendable.steps.length)
}

// Pull what we missed. Local work is rewound, remote steps applied, then local
// work replayed on top — so unsent edits survive someone else's.
editor.commands.receiveCollabSteps(await since(getVersion(editor)))

Authority is the server half, deliberately transport-free so the same object works over WebSocket, HTTP polling, or an in-memory channel in a test.

remoteCursors() draws everyone else's caret and selection, as decorations rather than as document content — so nothing about presence travels with a copy, an export, or an undo.

import { collab, remoteCursors, remoteCursorCSS } from '@matrajs/collab'

const editor = createEditor({
  extensions: [...starterKit, collab({ clientId }), remoteCursors()],
})

// Whatever your transport delivers.
socket.on('presence', (p) => editor.commands.setPresence(p))
socket.on('left', (id) => editor.commands.removePresence(id))

A caret arrives as a position in the sender's document, and is wrong the moment anything is typed locally. Each one is mapped through the same steps the local document went through, which is the only thing that keeps a caret on the word it was actually next to — clamping it to the document size, the obvious shortcut, silently points every cursor at the wrong place.

Colours come from colorFor(clientId), derived rather than assigned, so two clients that never speak still agree on what colour a third person is. Drop in remoteCursorCSS for enough styling to see a caret, or write your own against .matra-remote-cursor, .matra-remote-cursor-label and .matra-remote-selection.

Source: https://github.com/amrelaco/matra

Licence

Source-available under the Matra Commercial License, not MIT — unlike @matrajs/core, which is MIT and stays that way.

Free for evaluation, development, testing, personal projects, education, and internal tools at organisations with fewer than three developers on the codebase. Paid, one seat per developer, for production use beyond that. No licence key and no phone-home: the licence is the agreement, not a mechanism.

Versions up to and including 0.5.0 were published under MIT, and that grant cannot be withdrawn — if you are already on 0.5.0 you may keep using it under MIT indefinitely. The commercial licence applies from 0.6.0 onward.

licensing@amrela.co