  We develop a method by which vacuum transitions may be included in
light-front calculations. This allows tadpole contributions which are important
for symmetry-breaking effects and yet are missing from standard light-front
calculations. These transitions also dictate a nontrivial vacuum and
contributions from vacuum bubbles to physical states. In nonperturbative
calculations these separate classes of contributions (tadpoles and bubbles)
cannot be filtered; instead, we regulate the bubbles and subtract the vacuum
energy from the eigenenergy of physical states. The key is replacement of
momentum-conserving delta functions with model functions of finite width; the
width becomes the regulator and is removed after subtractions. The approach is
illustrated in free scalar theory, quenched scalar Yukawa theory, and in a
limited Fock-space truncation of $\phi^4$ theory.
