Escrow: binding contracts as a coworld, for four LLM-piloted cogs. A trading floor with three goods (ORE, GRAIN, TIMBER), one currency (HEARTS), and private comparative advantage: each seat is dealt one of four profiles - Mason, Farmer, Forester, Factor (the deal is drawn from the seed) - that produces a lopsided bundle every turn and pays 10 or 12 hearts for a commission made of the goods it does NOT produce. Filling commissions is the only source of new hearts; everything else is a transfer. The whole action space is a tiny contract DSL the game itself executes: OFFER / LOCK / ASK / DUE / IF | [NOT] PAID > / THEN / ELSE , with payouts SWAP, KEEP, PROPOSER or ACCEPTOR. BREACH IS IMPOSSIBLE because contracts are pre-funded: posting an offer moves the proposer's LOCK bundle into escrow, signing moves the acceptor's ASK bundle in, and settlement only redistributes what is already locked - non-performance is the ELSE branch firing, not a refusal to pay. Escrowed stock is visible but unusable: it cannot be given away, cannot fill a commission, and does not count toward a HOLDS condition, which is the engine of the loophole game. The floor is open outcry - every profile, stock and live contract is public - so the skill is drafting, pricing, and reading the other side's ELSE branch. Most hearts at the horizon wins; leftover goods are worth nothing. The game is LLM-driven: every turn the server sends each seat's policy prompt plus the floor, the escrow board, the ledger and its private notes to Claude (one parallel batch per turn), so A POLICY IS JUST A PROMPT - build one by reusing the published player runnable and setting the PLAYER_PROMPT environment variable to your strategy. Two scripted baselines (trader and hoarder) play any seat that registers as scripted - and every seat when no LLM credentials are available, so episodes always complete.