Slate React native beforeinput formatting needs semantic command handlers

Problem

Slate React formatting examples used raw onDOMBeforeInput parsing for normal editor behavior. That made users handle browser event spellings directly and encouraged callback memoization ceremony around a runtime-owned native listener.

Symptoms

• hovering-toolbar switched on event.inputType values such as formatBold.
• The example wrapped the handler in useMemo(() => callback, [editor]).
• Native input listener wiring depended on app callback identity.
• Raw browser-event examples became the path people copied for model behavior.

What Didn't Work

• Keeping formatting in raw onDOMBeforeInput. It preserves native access, but it teaches browser quirks as normal Slate API.
• Asking users to wrap event props in useMemo or useCallback. That exports runtime listener churn as app responsibility.
• Hard-coding a default mark mutation for raw Slate. Slate can report intent without deciding whether the app uses bold, strong, or a custom schema.

Solution

Keep onDOMBeforeInput as the raw native escape hatch, but route normal formatting behavior through a semantic command handler:

<Editable
  onCommand={(command, { editor }) => {
    if (command.kind !== 'format') return

    switch (command.format) {
      case 'bold':
      case 'italic':
      case 'underline':
        toggleMark(editor, command.format)
        return true
    }
  }}
/>

Inside the runtime, classify native format* beforeinput and matching hotkeys into command objects, then invoke the semantic handler before default fallback. Keep native listeners attached to the root and read the latest app handlers from stable runtime state.

Why This Works

The runtime owns native event normalization, command classification, and DOM repair. App code owns mark schema policy. Splitting those boundaries gives raw Slate native access without forcing common examples to parse DOM event strings or memoize callbacks for listener stability.

Prevention

• Use semantic command/input-rule surfaces for model behavior.
• Reserve onDOMBeforeInput examples for advanced native event escape hatches.
• Add tests that prove latest callbacks are read without native listener reattachment.
• Add browser proof for real native format beforeinput behavior when examples change.

Related Issues

• docs/solutions/test-failures/2026-04-29-slate-browser-command-rows-must-share-app-text-policy-with-native-input.md
• docs/solutions/ui-bugs/2026-04-30-slate-react-beforeinput-delete-commands-must-refresh-synced-selection.md
• docs/plans/2026-05-14-slate-v2-callback-memoization-dx-ralplan.md