We study the holomorphic twist of 3d ${\cal N}=2$ gauge theories in the
presence of boundaries, and the algebraic structure of bulk and boundary local
operators. In the holomorphic twist, both bulk and boundary local operators
form chiral algebras (\emph{a.k.a.} vertex operator algebras). The bulk algebra
is commutative, endowed with a shifted Poisson bracket and a "higher" stress
tensor; while the boundary algebra is a module for the bulk, may not be
commutative, and may or may not have a stress tensor. We explicitly construct
bulk and boundary algebras for free theories and Landau-Ginzburg models. We
construct boundary algebras for gauge theories with matter and/or Chern-Simons
couplings, leaving a full description of bulk algebras to future work. We
briefly discuss the presence of higher A-infinity like structures.