Slate React Runtime One-Shot Breakup Plan

Requirements Summary

Break up the former packages/slate-react/test/runtime.tsx runtime landfill into behavior-domain proof owners.

The plan must:

• preserve current green behavior
• move tests by behavior domain, not by arbitrary line chunks
• keep shared mount/test plumbing in one reusable helper
• keep surface-contract.tsx on API/surface ownership
• leave explicit behavior-domain proof owners instead of one runtime bucket

Current State

Current files:

• surface-contract.tsx 496 lines
• provider-hooks-contract.tsx 560 lines
• react-editor-contract.tsx 542 lines
• primitives-contract.tsx 985 lines
• editable-behavior.tsx 755 lines
• projections-and-selection-contract.tsx 302 lines
• app-owned-customization.tsx 639 lines
• large-doc-and-scroll.tsx 424 lines
• runtime-fixtures.ts 1174 lines
• test-utils.ts 106 lines

What is now real:

• runtime.tsx is gone
• provider/hooks, withReact / ReactEditor, primitives, mounted editable behavior, projection/ref behavior, app-owned customization, and large-doc lanes now have explicit owners
• mount helpers are shared in test-utils.ts
• runtime fixtures are centralized in runtime-fixtures.ts

Source Learnings

• ReactEditor and withReact should ride the mounted bridge, not a fake old plugin stack: 2026-04-09-slate-v2-reacteditor-should-ride-the-mounted-bridge-and-keep-base-components-standalone.md
• renderer contracts should move into stable owner surfaces instead of living forever as proof-file copy-paste: 2026-04-04-v2-renderer-primitives-should-own-node-shapes-not-example-markup.md

Target File Architecture

After the one-shot breakup, packages/slate-react/test/ should look like:

• surface-contract.tsx API-facing surface and low-level public behavior already split out
• test-utils.ts shared JSDOM mount helpers only
• large-doc-and-scroll.tsx large-document shells, promotion, full-doc select-all/paste, scroll behavior
• provider-hooks-contract.tsx provider/editor lifecycle, useSlateStatic, useSlateSelector, useSlateWithV, editor/readOnly/focused/composing hooks, element hooks
• react-editor-contract.tsx withReact, ReactEditor, DOM translation, root/window/shadow-root helpers, mounted bridge seam
• primitives-contract.tsx ZeroWidthString, TextString, SlateText, SlateLeaf, SlateElement, SlateSpacer, SlatePlaceholder, EditableText, EditableTextBlocks, VoidElement
• editable-behavior.tsx root mounting, DOM-to-snapshot reconciliation, keydown/paste forwarding, readOnly, controlled replacement, rich-inline anchor reset/refocus
• projections-and-selection-contract.tsx projection store behavior, range-ref-backed projections, root/node ref hooks, selector invalidation locality
• app-owned-customization.tsx markdown preview, markdown shortcuts, forced layout, styling, hovering toolbar, image/embed actions, table rendering

runtime.tsx is gone.

Exact Test Ownership

1. provider-hooks-contract.tsx

Move these runtime rows:

• selector subscriptions stay slice-scoped across a transaction
• useSlateStatic returns the provider editor and updates when the provider editor changes
• Slate initializes fresh editors from initialValue and re-initializes when the provider editor changes
• Slate publishes onChange, onValueChange, and onSelectionChange on the current snapshot seam
• slate-react hook surface exposes editor, selection, readOnly, and current boolean contexts
• slate-react focused and readOnly hooks stay correct outside Editable descendants
• slate-react element hooks expose current element context and selected state
• useSlateSelector keeps referential stability when custom equality says values are equal
• useSlateWithV exposes the provider editor with the current snapshot version
• switching provider editor instances updates subscribers to the new editor

Why:

• one domain: provider and hook contract
• no need to open DOM bridge or render primitive files for hook regressions

2. react-editor-contract.tsx

Move these runtime rows:

• withReact and ReactEditor expose the current compatibility seam
• withReact composes with withLinks and honors wrapper-owned inline behavior
• withReact composes with withMentions and honors wrapper-owned insertMention behavior
• withReact composes with runtime forced-layout behavior
• ReactEditor DOM target and event helpers expose the current mounted bridge seam
• ReactEditor root/window helpers expose the mounted document boundary
• ReactEditor root/window helpers expose the mounted shadow-root boundary

Why:

• one domain: mounted bridge and ReactEditor compatibility surface
• matches the repo learning exactly

3. primitives-contract.tsx

Move these runtime rows:

• slate-react exports the current named render and component prop types
• ZeroWidthString renders line-break placeholders without FEFF by default
• ZeroWidthString retains FEFF for non-linebreak placeholders
• TextString repairs stale native text on rerender
• SlateText and SlateLeaf own the v2 text-node shape
• SlateElement and SlateSpacer own the v2 element and spacer shape
• SlatePlaceholder owns the v2 placeholder overlay shape
• SlatePlaceholder supports arbitrary intrinsic tags through as
• EditableText composes text, zero-width, and optional placeholder branches
• EditableText forwards arbitrary intrinsic placeholder tags
• EditableText supports renderPlaceholder
• EditableText supports renderText
• EditableText splits a text node into projected leaves and refreshes segment data
• EditableText exposes text and leafPosition to renderLeaf
• EditableText exposes leaf marks to renderSegment
• EditableBlocks exposes renderLeaf
• EditableBlocks forwards renderText
• EditableBlocks exposes renderElement attributes
• EditableBlocks preserves existing text marks during DOM reconciliation
• EditableText renders zero-length projection slices as mark placeholders
• EditableText can derive text and runtime binding from a path
• EditableTextBlocks can render from the public editor + projectionStore surface
• EditableBlocks aliases the public top-level text-block surface
• EditableBlocks can render mixed inline descendants through the public surface
• EditableBlocks falls back to editor.isInline when no isInline prop is supplied
• EditableElement owns the minimal editable element wrapper shape
• EditableElement supports arbitrary intrinsic tags through as
• VoidElement owns the minimal void wrapper and spacer shape
• VoidElement supports arbitrary intrinsic tags for wrapper and content

Why:

• one domain: render and primitive surface
• directly follows the renderer-primitive learning

4. editable-behavior.tsx

Move these runtime rows:

• Editable owns root mounting and DOM-to-snapshot reconciliation
• EditableBlocks survives text-to-inline replacement on the same path without hook-order crashes
• EditableBlocks forwards keydown handlers to app-owned keyboard policy
• EditableBlocks forwards paste handlers to app-owned paste policy
• EditableBlocks supports readOnly on the structured editing surface
• optional Activity boundary preserves local state and resumes on latest committed snapshot
• controlled replacement works through package hooks without effect mirroring
• EditableBlocks rich-inline anchor reset establishes a new history boundary without effect mirroring
• EditableBlocks rich-inline anchor restores DOM selection on refocus after reset
• EditableBlocks rich-inline anchor keeps selector invalidation local
• EditableBlocks keeps unchanged text segments stable across top-level prepends

Why:

• one domain: mounted editing surface behavior

5. projections-and-selection-contract.tsx

Move these runtime rows:

• root and node ref hooks delegate DOM ownership to slate-dom
• projection subscriptions stay local when external decoration state changes
• selection-derived annotation projections track committed selection changes
• range-ref-backed projections support persistent annotation anchors

Why:

• one domain: projection and ref-locality semantics
• separate from general provider hooks and from rendering primitives

6. app-owned-customization.tsx

Move these runtime rows:

• EditableBlocks supports app-owned markdown preview projections
• EditableBlocks supports app-owned markdown shortcuts
• EditableBlocks supports app-owned forced layout enforcement
• EditableBlocks forced layout restores the second paragraph when only a title remains
• EditableBlocks supports app-owned styling surfaces
• EditableBlocks supports app-owned hovering toolbar state
• VoidElement supports app-owned editable void controls without mutating editor content
• EditableBlocks supports app-owned image and embed void actions

Why:

• one domain: app-owned extension and customization surface

7. Keep As-Is

• surface-contract.tsx
• large-doc-and-scroll.tsx
• test-utils.ts

Execution Order

Executed order:

1. Extract provider-hooks-contract.tsx
2. Extract react-editor-contract.tsx
3. Extract primitives-contract.tsx
4. Extract editable-behavior.tsx
5. Extract projections-and-selection-contract.tsx
6. Extract app-owned-customization.tsx
7. Delete runtime.tsx

Editing Rules

1. Do not duplicate mountApp or mountAppInShadowRoot. Use test-utils.ts.
2. Keep imports local to each file’s domain.
3. If a moved test needs shared factory data, extract only the narrow helper.
4. Do not mix ReactEditor bridge rows into provider-hook files.
5. Do not mix app-owned customization rows into primitive files.
6. If one file still crosses two domains after extraction, split again in the same pass.

Verification

After the full breakup:

1. pnpm turbo build --filter=./packages/slate-react
2. pnpm turbo typecheck --filter=./packages/slate-react
3. pnpm --filter slate-react test
4. pnpm lint:fix
5. LSP diagnostics on every new file
6. architect review on:
   • surface-contract.tsx
   • provider-hooks-contract.tsx
   • react-editor-contract.tsx
   • primitives-contract.tsx
   • editable-behavior.tsx
   • projections-and-selection-contract.tsx
   • app-owned-customization.tsx
   • large-doc-and-scroll.tsx
   • test-utils.ts

Acceptance Criteria

• runtime.tsx no longer acts as the default owner for unrelated React package behavior
• each extracted file has one dominant behavior domain
• no helper file is matched as a test file
• package tests stay green without hidden fixture duplication
• a future agent can find the owner for a withReact, ReactEditor, projection, primitive, editable behavior, or app-owned customization regression in one file open

Risks

• too much helper extraction turns into a utility swamp mitigation: only share mount/setup code and narrow fixture factories
• app-owned customization rows may still hide cross-domain subgroups mitigation: split again only if that file becomes another landfill
• surface-contract.tsx still contains some mounted behavior rows mitigation: leave it alone in this one-shot pass unless they clearly belong in one of the extracted files; do not widen the plan into churn for churn’s sake

Hard Read

If you do this one-shot pass well, runtime.tsx stops being “the React bucket” and becomes either tiny or dead.

That is the point.