Retain four native phases for thirteen keyboard-driven cases: authored input, splits, cold-reopened splits and joins. Cover formatting and empty boundaries, nested children, lists, completed tags, cells, soft breaks and text before hyperlinks.

Verify original paragraph identities, child transfer and tag retention. Empty-prefix joins keep the left paragraph but adopt the right text identity; list and indentation changes are recorded separately from joining.

Checks: 127 Python tests; four 14-page native comparisons with 5,945 explicit format values each; thirteen split graphs and thirteen joins with 5,300 normalized style comparisons. All disposable VMs removed.

Assisted-by: gpt-6-astra