Undo and redo

Reverse an edit #

Use the Plexus wrappers for document history:

plexus.undo();
plexus.redo();

The wrappers manage internal tracking during replay, so changes caused by undo and redo are not themselves recorded as new undoable edits. Use them instead of calling the underlying Yjs UndoManager directly.

Group a user action #

A synchronous @syncing.action method groups its changes into one undo unit per document it touches:

import { PlexusModel, syncing } from "@here.build/plexus";

@syncing("Task")
class Task extends PlexusModel {
  @syncing accessor title = "";
  @syncing accessor done = false;

  @syncing.action
  finish(title: string) {
    this.title = title;
    this.done = true;
  }
}

Call the method on a model in a document. Ordinary edits use the underlying undo manager's 500 ms capture window. Reactivity and transactions explains action boundaries, synchronous execution, and crash behavior.

What history records #

Content changes are reversible. Structural bookkeeping, such as creating entity shells and materializing collection containers, is excluded from history. Undoing a content edit does not erase the underlying entity's identity.

Undo is also separate from rollback: an undo happens after a change, while a matching rollbackIf condition can discard a buffered action before it is broadcast. See action crash behavior.