Heads-Up No-Limit Hold'em — rules

Two-player no-limit Texas Hold'em. A match is 10 independent hands; the player with the higher cumulative chip delta across all 10 hands wins.

Per-hand setup

Each hand is independent. Whatever you win or lose in hand N does not change your starting stack for hand N+1 — both players start every hand with exactly 200 chips. The match score (match_chips) tracks the running sum of per-hand chip deltas; this is what's compared after hand 10.

Streets

Each hand runs through up to four betting rounds, with shared community cards revealed between them.

Bet sizes are not fixed. On any street, a bet or raise can be any whole-chip amount that satisfies the no-limit min/max constraints below.

Legal actions

The player to act is determined by the engine:

• Preflop: small blind (button) acts first.
• Flop / turn / river: big blind (non-button) acts first.

The engine produces an explicit legal_actions list every turn. The grammar of the actions is:

The engine enumerates every concrete bet:N and raise-to:N value in legal_actions for the current state — so if a value isn't in the list, it's illegal.

Bet / raise sizing rules (no-limit)

• The minimum opening bet on any street is the big blind (2 chips). Above that, any integer up to your stack is legal.
• The minimum raise increment equals the size of the previous bet or raise on the current street. If a player goes all-in for less than a full raise (a "short all-in"), that is still legal but it does not reopen the action — the previous full-raise size is preserved as the minimum for any subsequent raise.
• The maximum bet or raise is your remaining stack (no chip can come from outside).
• raise-to:N always references your total chips committed this round, not the increment.

Calls and short all-ins

When to_match exceeds your stack, calling commits all remaining chips. Excess chips owed by the opponent are returned (no side pots in heads-up).

Showdown

If both players see the river without folding, hands are evaluated as standard 5-card poker from the 7 available cards (2 hole + 5 board). Standard ranking: straight flush > four of a kind > full house > flush > straight > three of a kind > two pair > one pair > high card. Ties split the pot; an odd chip in a split pot goes to the non-button.

Match termination

After hand 10, the player with the higher match_chips total wins. Equal totals → no winner (logged as a draw).

Forfeits

Any illegal action — outside the legal_actions set, out of turn, or malformed — is a hard forfeit. The player who attempted the illegal action loses the match outright.