A-book / B-book / hybrid

Broker execution models: A-book passes client orders to the market, B-book internalizes them with the broker as counterparty, and most retail CFD brokers run a hybrid. Because a B-book venue can degrade execution for clients who become profitable, fill-quality drift can flag how you are being handled, independent of your edge.

First used in Lesson 3.5 · Monitoring, decay & the venue — the lesson that makes this term real.