MAX OPEN $ (2026-08-06) — set (or clear with null) the DESK-level cap on how much money any ONE bot may have committed across all its open positions at once. Every bot on the desk obeys it unless the bot sets its own (per-bot wins). Session-owner scoped like the other desk mutations; 404 if the desk is not the caller's (cloak).

It is a PER-BOT ceiling applied desk-wide, NOT a desk total — the desk's own limit is its cash, which the buying-power gate already enforces over the whole book. A LIVE-FILL knob: the walk refuses a NEW entry that would take a bot over it, with its own distinct reason, and never touches any verdict. Nothing is reserved: the committed total is derived fresh every walk, so closing a position frees the room on the next one.