It can technically happen, but a broker who plans on it is showing you a red flag. Your real protection is the lender's float-down policy. Brokers operate under agreements with their wholesale lenders, and the understanding is that a loan locked with a lender closes with that lender. A broker who routinely pulls locked loans and re-places them elsewhere is burning those relationships, which raises a fair question about how they do business. You do not want your loan riding on that maneuver. You also do not need it. Most lenders have a renegotiation or float-down policy for a meaningful drop after lock, and the lender's incentive is simple: their profit shrinks if they renegotiate you to a lower rate, and it goes to zero if you walk and the loan never closes. Faced with losing the deal entirely, most would rather give up some margin and keep it. So ask up front, when you lock: how far do rates have to move, when in the process can the float-down be exercised, and what does it cost. Get those terms clearly and you have a legitimate path to benefit from a big drop. Nobody can promise rates fall after you lock, but a good lock comes with a known policy in case they do.