Slate React model-owned insert must repair the DOM caret

Problem

Typing through the browser at the end of a rich-text block updated the Slate model correctly, but the visible browser caret could render in the wrong place.

The missed case was inserting before trailing punctuation in a custom-rendered leaf. The model selection moved after the inserted text, but the DOM selection stayed collapsed on a wrapper span at offset 0, so Chrome painted the caret before the inserted character.

Why model-only tests missed it

The Slate selection and text were both correct:

• model text contained the inserted character
• model selection moved to the expected offset

But the browser selection was not canonical:

• anchor node was an element wrapper, not a text node
• anchor offset was 0
• the visual caret painted before the inserted text

Model selection assertions and text assertions cannot catch this. Browser tests must also assert the DOM caret node and offset, or compare caret rectangles.

Fix

For model-owned insertText in Editable, schedule a DOM selection repair after React commits the updated text.

Also avoid treating a collapsed wrapper-element DOM selection as good enough just because it maps back to the same Slate range. If the browser caret is on a wrapper instead of a text node, force the DOM selection to the canonical DOM range for the current Slate selection.

Prevention

• Add browser rows that assert text, model selection, and DOM caret location.
• Include insertion before punctuation and insertion inside a text leaf, not only append-at-end cases.
• Treat element-wrapper collapsed selections as suspicious after model-owned text insertion.
• Rebuild slate-react before Playwright rows that consume package dist; source-mode/dev-server proof alone can hide stale package output.