  The algebraic tools used to study topological phases of matter are not
clearly suited to studying processes in which the bulk energy gap closes, such
as phase transitions. We describe an elementary two edge thought experiment
which reveals the effect of an anyon condensation phase transition on the
robust edge properties of a sample, bypassing a limitation of the algebraic
description. In particular, the two edge construction allows some edge degrees
of freedom to be tracked through the transition, despite the bulk gap closing.
The two edge model demonstrates that bulk anyon condensation induces symmetry
breaking in the edge model. Further, the construction recovers the expected
result that the number of chiral current carrying modes at the edge cannot
change through anyon condensation. We illustrate the construction through
detailed analysis of anyon condensation transitions in an achiral phase, the
toric code, and in chiral phases, the Kitaev spin liquids.
