Opening auction, market making, and arbitrage as a capital business

Inventory, holding period, and funding first

The archive describes a proprietary-desk workflow for an opening-auction book, a specialist-like inventory role, and overnight merger or pairs inventory. Each procedure is written through the inventory that may be held, how long that inventory may stay open, and the capital that carries the book.

The opening book, the market-making book, and the overnight book are not introduced as three separate forecasts of a single name or index. They are introduced as uses of the same kind of facility: a book that can take the other side of an imbalance and still remain funded.

Firm-capital and the size of the book

Exchange membership plus a modest clearing deposit was described as unlocking the clearing firm's capital for the trader's own book, with trading profits kept rather than split. A later proprietary-firm copy of that floor model asked traders for only a small risk deposit while the firm supplied buying power and the trader kept profits.

Firm-supplied buying power was explicitly distinguished from retail margin. The stated difference was the size of the inventory book that could be carried, not a larger personal loan. That supplied buying power is firm-capital: buying power supplied by a proprietary book so inventory can be carried without treating that book as the trader's personal margin loan.

Participation in the opening-gap procedure was described as available only when traders used firm-capital rather than a personal retail account.

Two-sided opening inventory

One opening-auction procedure placed premarket limits both to buy and to sell short the same list, expecting only the names that gapped through those limits to fill. That pairing is two-sided-opening-inventory: buy and sell-short limits on the same name so a gap through either side can create a fill without a prior directional call.

Each of those limits was an opening-only-order, a premarket limit that can fill in the opening auction or first prints and is not meant to work as a regular-session rest order. The opening-only book was run with an automated gray-box assistant rather than as a purely manual gap fade.

Surrogate-market-making without a forecast

Surrogate specialist and market-making roles were presented as substitutes for having to forecast the direction of a single stock or index. That stance is surrogate-market-making: standing ready to take the opposite side of an opening or intraday imbalance in a specialist-like inventory role rather than forecasting a trend.

Editorial: once the book is allowed to be two-sided, the first testable object is the inventory role, not a directional entry on one name.

Overnight-arbitrage after the bell

Merger and correlated-pairs arbitrage were characterized as overnight uses of capital, unlike opening-only inventory that can be flat shortly after the bell. Overnight-arbitrage is merger or correlated-pairs inventory that stays on the book past the close and therefore needs a facility that can warehouse multi-session capital.

Editorial: the holding-period difference is why the three procedures cannot be specified as three isolated signals. An opening-only-order can be designed to finish near the open. Overnight-arbitrage cannot. Both still depend on firm-capital large enough to carry the intended book.