Plan JSON gained wall arcs and paper size but kept version 1, so an older core reads a curved document silently, as the chord with no sheet. It is documented, not prevented.
From the Grok pain-radar digests, Nov 1-2 2026 (Nov 1 8:41 AM ET through Nov 2 7:41 AM ET digests plus the Haitch editions). Verified live 2026-11-02: issue/PR read; title and state confirmed.