What type of lien is valid against a BFP as an unrecorded interest?

In the context of real estate transactions, a mechanic's lien is unique among the options presented because it can be valid against a bona fide purchaser (BFP) even if it is unrecorded. Mechanic's liens are a type of statutory lien that provides security to contractors and subcontractors for materials and labor they provide to improve a property.

The key aspect of mechanic's liens is that they are typically created to protect the interests of those who contribute labor or materials to a property improvement. If a property is sold, a new owner could still be responsible for the mechanics' lien, even if they were unaware of its existence at the time of purchase, because these liens can attach automatically when work begins, and they can affect the property regardless of whether they have been formally recorded in public records.

This potential to assert a claim despite the lack of recording distinguishes mechanic's liens from the other types of liens listed. Mortgage liens and judicial liens usually require proper recording to gain priority and enforceability against subsequent purchasers. Assignable liens, which refer to a lien that can be transferred to another party, do not specifically relate to the protection of a BFP in the same way mechanic's liens do. Thus, the nature of mechanic's liens means that