The five Divi write tools extend DiviWriteAbility (final permission and execute, change() per tool, shared output schema). DiviErrors holds the unknown-node, position and compose-error mapping; DiviContentComposer uses the same mapping (ledger T9). ToolNamingTest skips abstract classes. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7