- Table synced_blocks (source of truth) + page_synced_blocks (references) - Migration 15 + service app/services/synced_blocks.py - API endpoints: CRUD synced blocks, add/remove page references - Editor: /synced slash command, synced block rendering with badge - Realtime: _propagate_synced broadcasts updates to all referencing rooms - Export: synced blocks resolved in Markdown/HTML/PDF - 18 tests in tests/test_v514_synced_blocks.py Co-authored-by: FlowDeck <[email protected]>