  The hydrodynamic exchange of a protoplanet's envelope material with the
background protoplanetary disk has been proposed as one mechanism to account
for the diversity of observed planet envelopes which range in mass fractions of
~1% for super-Earths to ~90% for giants. Here we present and analyze 3D
radiation-hydrodynamics models of protoplanet envelopes to understand how the
exchange of mass and energy between the protoplanet and background disk
influences the formation process. Our protoplanet envelope simulations show an
exchange of material bringing the outer <0.4Rbondi envelope to steady state.
This exchange provides a continuous source of energy, which acts to increase
the observed luminosity beyond that inferred from the binding energy liberated
from Kelvin-Helmholtz contraction alone -- a finding important for potential
protoplanet observations. The inner <0.4Rbondi, on the other hand, appears
insulated -- growing in accordance with 1D quasi-static theory. We incorporate
these 3D hydrodynamic effects into an extensible 1D framework with a physically
motivated three-layer recycling parameterization. Specializing to the case of
Jupiter, recycling produces minimal changes to the growth rate with the planet
still entering runaway accretion and becoming a gas giant in ~1 Myr. Even in
the inner disk (0.1 AU), our 1D models suggest that recycling is not so robust
and ubiquitous as to stop all cores from becoming giants. At the same time
however, this recycling can delay a runaway phase by an order-of-magnitude
depending on the inner disk conditions and core mass.
