Protocol

Markets & order book

Every Thassa market is a binary YES/NO order book priced in cents. A share pays $1 to the winning side. Price is probability: YES at 62¢ is the book saying 62%.

The pricing model

• An order is always “buy side at limit price p cents for shares shares” — there is no separate sell verb; exiting a YES position means buying NO (or redeeming after settlement).
• Limit prices are integers 1..99 cents.
• Escrow: a YES buyer at p escrows p × shares cents; a NO buyer at q escrows q × shares cents (all in payment-token base units).
• Crossing: buy YES @ p matches resting buy NO @ q whenever p + q ≥ 100 — together the pair fully collateralizes the $1 payout.

Matching rules

Matching happens at order placement: the incoming order takes the best crossing price levels first, then any remainder rests on the book as a maker order.

• Price-time priority. Better-priced resting orders fill first; within a price level, first in, first filled (FIFO).
• Execution at the maker’s price. The resting order’s level sets the execution price — a taker’s aggressive limit only widens what can cross; it never worsens the fill.

Resting (maker):  buy NO  @ 40¢ × 500 shares     — the maker
Incoming (taker): buy YES @ 65¢ × 300 shares     — crosses: 65 + 40 ≥ 100

Execution: 300 shares AT THE MAKER'S LEVEL — taker pays 100 − 40 = 60¢/share
  taker escrow used:  300 × $0.60 = $180  (+ taker fee)
  maker escrow used:  300 × $0.40 = $120
  → each matched pair holds $1.00/share, fully collateralized

Under the hood the book is gas-friendly: per market and side, a uint128 price-level bitmap gives O(1) best-price discovery, and each level holds a FIFO queue of packed orders.

Market lifecycle

Markets move through six one-word states, used verbatim across the app, the API, and these docs:

Order states

Creating a market

Market creation is free — no protocol fee — but the creator’s initial order must deposit at least $1 of capital. That opening bet is the market’s first liquidity, and the creator is committed to it: the market shows OPEN until someone takes the other side, then MATCHED. Both the question and the structured settlement query are stored onchain as public strings at creation.

Fees

Kalshi-style, taker-side only. Makers pay nothing. The fee on each match, at execution price p (the maker’s price, in cents):

fee = ceil(7% × shares × p × (100 − p) / 10000)   // dollars, p = execution price in cents
    = ceil(takerFeeBps × shares × p × (100 − p) / 10000 / 10000)   // takerFeeBps = 700

The fee is quadratic in uncertainty — largest at 50¢, vanishing toward 1¢/99¢ — and is deducted from the taker’s escrow, rounded up at the token’s base unit.

Worked examples

Where fees go

• 10% of every collected fee accrues to the market creator (claimable via claimCreatorFees).
• 5% goes to the affiliate — the post whose market widget routed the order (affiliatePostId; 0 = none, in which case the share goes to the protocol).
• The remainder goes to the protocol vault.

Flat fees

Settlement & redemption

1. Anyone calls settleMarket(marketId) and pays the $0.05 trigger. Status → SETTLING.
2. The oracle pipeline resolves the outcome — see Settlement & sources. Status → SETTLEDYES.
3. Winners call redeem(marketId) for $1/share, minus the flat withdrawal fee. Unmatched or resting deposits are refundable any time via withdraw.