Slate v2 overlay architecture

Purpose

This is the research-layer architecture map for the Slate v2 overlay system.

It is not the rollout plan. It is the stable architecture read behind the plan.

Shape

Three lanes:

• Decoration transient, overlap-friendly, mapped or externally indexed
• Annotation durable, id-bearing, bookmark-backed
• Widget anchored UI, geometry-derived, narrower public surface

Ownership

• slate logical ranges, bookmarks, lower-level live-ref machinery, runtime identity
• slate-react overlay kernel, projection indexing, subscriptions, annotation mirrors, widget placement/runtime
• slate-dom DOM mapping, selection fidelity, clipboard/browser boundary

Public-surface stance

• Bookmark is the durable public anchor noun
• RangeRef is lower-level runtime machinery
• annotation metadata may stay outside the editor runtime
• widget placement can stay internal at first
• generic widget registration can stay internal at first
• public path-based widget anchors are cut
• callback/array-first APIs are not the preferred flagship surface

Runtime posture

• explicit refresh/invalidation
• narrow subscriptions
• active editing corridor stays urgent
• side panes and other non-visible work can lag safely

React 19.2 posture

React 19.2 strengthens this architecture where it actually matters:

• useSyncExternalStore makes selector/store subscriptions first-class
• startTransition and useDeferredValue make non-urgent derived UI first-class
• Activity makes hidden panes a real preserved-state lane

That makes Slate v2 a credible React-native perf architecture.

It does not, by itself, make the system universally better than ProseMirror, Lexical, or VS Code.

Why this system shape won

• ProseMirror proved mapped overlay and bookmark discipline
• Lexical proved mark/store/decorator separation
• Tiptap proved product-layer comments and suggestions stay distinct
• VS Code proved typed channels
• TanStack DB proved store/controller APIs
• local Slate v2 proved runtime ids, bookmarks, and projection slices

Why it beats legacy Slate

Legacy Slate treated decorate like the center of the overlay world.

That made one callback pretend it could own:

• transient highlighting
• durable anchors
• anchored widget UI
• browser-facing composition decoration
• large-document invalidation

Slate v2 is better because it stopped doing that.

It now has:

• separate Decoration, Annotation, and Widget lanes
• Bookmark as the durable public anchor story
• RangeRef demoted to lower-level runtime machinery
• store/controller-style annotation ownership
• widget UI that is not forced through text-decoration semantics
• explicit large-document overlay posture

Relative to the field

• better than legacy Slate by a lot
• aligned with ProseMirror on mapped overlays and durable anchors
• aligned with Lexical on store/decorator lane separation
• informed by Tiptap on product-layer comment/suggestion separation
• informed by VS Code and TanStack DB on typed channels and stable stores
• not the universal winner over ProseMirror or Lexical as total engines

Best next reshape if perfection matters

If this lane wants the strongest possible perf-architecture claim, the next reshape should target invalidation below the React layer:

• source-scoped dirtiness
• more indexed projection recompute
• less full-source projection rebuild per committed snapshot

React 19.2 is already good enough for the UI side. The remaining gap, if any, is deeper than React.