  The availability-finality dilemma says that blockchain protocols cannot be
both available under dynamic participation and safe under network partition.
Snap-and-chat protocols have recently been proposed as a resolution to this
dilemma. A snap-and-chat protocol produces an always available ledger
containing a finalized prefix ledger which is always safe and catches up with
the available ledger whenever network conditions permit. In contrast to
existing handcrafted finality gadget based designs like Ethereum 2.0's
consensus protocol Gasper, snap-and-chat protocols are constructed as a
black-box composition of off-the-shelf BFT and longest chain protocols. In this
paper, we consider system aspects of snap-and-chat protocols and show how they
can provide two important features: 1) accountability, 2) support of light
clients. Through this investigation, a deeper understanding of the strengths
and challenges of snap-and-chat protocols is gained.
