Wraps the single-round engine rather than changing it: engine.py is the rules
oracle the TypeScript client is differential-tested against, and the round
itself is unchanged by the match. Only two rules live up here, both from the
Kosmos rulebook -- three rounds decided on the summed total, and "the player who
has more points begins" the next one. That is not alternating, and it is not
what reset_from_order hardcoded, so it takes a first_player argument now.
The rulebook says nothing about an exact tie, so the starter falls back to a
coin flip. A deterministic tie-break would give one seat a standing edge in
symmetric self-play and the agent would learn to steer for it. Round one needs
no special case: carry is (0, 0) there, so the tie branch already yields the
coin, which is exactly the rulebook's arbitrary "oldest player begins".
All randomness -- three deals and three coins -- is drawn in match_reset and
stored in the state, so match_step stays deterministic and needs no PRNG key
threaded through every rollout, eval, and gate body. It also makes a mirrored
match (same deals, seats swapped, same coins) a pure seat relabel, which the
antithetic pairing later depends on.
Tests cover the deck clock (44 deck draws a round, discard draws extend it),
carry banking each round exactly once, the start-player rule across all three
branches, a fair round-one coin, mirror symmetry, and that the running total
does not jump across a round boundary -- the last one matters because potential
shaping will be built on it.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XBQKgvBbxbheiTF1AVy1Sh
coolguyandClaude Opus 4.8
7cd299dd1e