Editor undo/redo

How Cmd+Z works in the visual editor since real-time co-editing landed.

Where history lives

History does not live in the Zustand store anymore. It lives in the collab binding (src/admin/pages/site/store/slices/site/collabBinding.ts) as one Y.UndoManager per collab document — one per page, Visual Component, and layout, plus one for the site shell/rosters. The store only mirrors availability flags (canUndo / canRedo) and exposes the undo / redo actions, which delegate to the binding (site/undoRedoActions.ts).

Because each manager tracks LOCAL_ORIGIN only, undo is per-editor by construction: your Cmd+Z reverts your edits, never a peer’s — the co-editing invariant.

The mutation path

Every store mutation still runs through runHistoricMutation (site/helpers.ts): the recipe mutates a Mutative draft, the resulting site-relative patches are handed to applyLocalSitePatches (the binding), which translates them into Y operations on the touched docs (@core/collab applySitePatchesToDocs). The Y transaction is what the UndoManager captures — the undo stack IS the CRDT edit history.

Undoing pops the doc’s stack; the resulting doc change projects back into the store through the binding’s projection path (the same path remote peers’ edits use), synchronously flushed so undo repaints immediately.

Coalescing (typing bursts)

Per-keystroke mutations (text edits, number sliders) pass a stable coalesceKey such as props:<nodeId>:<prop> through the mutate* helpers. The managers run with an infinite captureTimeout; the binding calls stopCapturing() exactly when the incoming key differs from the previous one — so consecutive same-key edits merge into ONE undo step, and any non-coalescing mutation, undo/redo, or inline-edit session boundary (collabBreakCoalescing) starts a fresh step. Typing a word is one Cmd+Z.

Multi-doc undo groups

A single mutation can touch several docs (convert-to-component writes the page, the new component, and the site roster; Super Import touches everything). The binding records each undoable step as a group of docIds whose managers captured a new stack item, and undo() reverts the whole group — one Cmd+Z, one logical mutation, across all its documents. The site doc always sorts first in a group so roster reverts project after row-level reverts.

Lifecycle

createSite / loadSite / clearSite call resetCollabDocsFromSite, which rebuilds the doc world for the new document and clears every undo manager — history never survives a document swap. In detached mode (tests, the pre-connect window) docs seed locally from the loaded site; in connected mode every doc rebinds through the provider and the server seeds it.

Editor-local state (selection, zoom, panel visibility) is not undoable — only document content flows through the docs.

It is, however, reconciled. A projection can remove nodes the editor is still pointing at — an undo reverting an insertion, or a peer deleting the subtree you had selected. The projection path therefore runs pruneCanvasSelectionDraft after the new site lands, exactly as a local deleteNode does: selections are pruned by tree-membership (survivors keep theirs, the anchor re-syncs, descendants swept with a subtree drop out), and an inline-edit session whose node vanished is closed. This is why selection state has one pruning implementation rather than one per write path.

Key files

• src/admin/pages/site/store/slices/site/collabBinding.ts — undo managers, routing groups, coalescing, projection
• src/admin/pages/site/store/slices/site/helpers.ts — runHistoricMutation and the six mutate* helpers (unchanged recipe API)
• src/admin/pages/site/store/slices/site/undoRedoActions.ts — the store’s undo/redo delegates
• src/core/collab/applyPatches.ts — patch → Y translation
• Tests: src/__tests__/editor-store/undo-redo.test.ts (behavioral contract), src/__tests__/collab/* (round-trip identity)