Order Book (CLOB)

OddsZero also ships an optional centralized limit-order-book (CLOB) venue, order_book.move, independent of the AMM. It is a parallel, price-time priority venue for traders who prefer limit orders over AMM swaps.

The CLOB is intentionally separate from the AMM. Positions opened on the CLOB are not auto-reconciled with AMM positions, and resolution/redemption integration is a documented future extension. Use it as an independent venue.

Mechanics

• create_book<T>(market_id, num_outcomes) — creates a shared OrderBook.
• Each Order stores only plain fields (id, owner, side, outcome, price_bps, shares, filled, escrow). All escrowed coins live in a single escrow_vault: Balance<T>.
• Buy order escrows shares · price_bps / 10000 (max cost).
• Sell order escrows shares · (10000 − price_bps) / 10000 (short cover).
• place_buy_order / place_sell_order automatically match against resting opposites (price-time priority) via match_orders.
• On a fill, collateral moves logically from buyer escrow to seller escrow (vault total unchanged); the book updates its own long_positions / short_positions ledgers and emits OrderFilled.
• cancel_order refunds only the unfilled portion of the escrow (prevents a fully-filled seller from reclaiming collateral the buyer already paid).

Price-time priority

crosses(a, b) requires opposite sides, same outcome, remaining size > 0, and compatible price (buy.price_bps ≥ sell.price_bps or vice versa). Execution price is the maker's (resting order's) price.

View helpers

• order_count, volume, escrow_balance.
• best_bid(outcome), best_ask(outcome).
• get_long(owner, outcome), get_short(owner, outcome).

Events

• OrderPlaced, OrderFilled, OrderCancelled.

Settlement

After the market resolves, the book must be settled (once settled, no new orders). settle_positions computes net P&L from long/short positions using the market's authoritative winning outcome. For a winning short seller, the full escrow (cover + buyer's cost) is refunded. On a Push, all positions are settled at 100% (both long and short receive their escrow back). The book is marked settled = true after first settlement; no new orders may be placed.