  Bra-ket wormholes are non-trivial saddles in Euclidean gravity. They have to
be sustained by negative Casimir energy of matter fields inside the throat.
However, Casimir energy is very sensitive to boundary conditions and in
presence of gauge symmetries one has to integrate over all possible boundary
conditions for the matter fields, as they are a part of bra-ket wormhole
moduli. For non- Abelian gauge groups the corresponding measure for the
boundary conditions, which we call Casimir entropy, is non-trivial and it
competes with the Casimir energy. We find that for large gauge groups this
significantly affects the bra-ket wormhole action and modifies the phase
diagram. Despite that, we do not find any violations of strong subadditivity in
the setup proposed by Chen, Gorbenko and Maldacena.
