An offline arena that agrees with the protocol arena

The engine arena plays complete games inside one process using the server's rules engine. A seat receives only what a protocol participant would receive: its own redacted observation and its own event batches, with theft receipts delivered only to thief and victim. Games take an explicit seed, so every lineup rotation sees the same board and opening order, and the 32 cores of this machine finish 512 builder games in under a second.

This tier is for development, sweeps, and structural measurements. It is not the authoritative protocol arena: there is no network, no turn clock, and player trades resolve by asking recipients in seat order. The experiment program defines both tiers and requires a fresh protocol cohort before the evidence boundary changes.

The frozen reference loses to the builders

Run 4969a9d0-cbcf-4b74-9b57-1e25f09ffa2c seated the reference expectimax-v1 at its default configuration against two ETA builders and one fast builder. It won 34 of 256 slot-games (13.3%) against ETA's 30.1% and 32.4% in the other two slots. The paired contrast against ETA is −0.168 (95% interval −0.251 to −0.085). Its decisions took 338 ms on average.

Unregistered exploratory runs on 8 seeds gave the same picture at larger budgets (depth 2 with a 256 node allocation, and depth 4 with beam 6 and a 512 allocation): 4 wins of 32 in each. Depth did not help the reference, which points at its leaf and its trading rather than at search effort. The reference stays frozen as the comparator that the tunable search is measured against.