Biomolecular condensates formed by liquid-liquid phase separation organize many cellular processes, yet it remains unclear how condensate localization is coupled to protein synthesis. In particular, proteins are often translated on polysomes, where multiple ribosomes on a single mRNA generate a bottlebrush-like assembly of nascent chains, raising the possibility that translation itself could be spatially coupled to condensates. Here we develop a theoretical framework for Co-Translational Condensation (CTC), in which nascent chains on a polysome for condensate proteins interact with their condensate and thus localize translation there. Using coarse-grained simulations, we show that protein domain architecture dictates the thermodynamics of CTC, consistent with a Langmuir adsorption model. Proteins with high-affinity regions exposed early on nascent chains display much stronger condensate association than architectures in which these regions appear only late in translation. A bioinformatic analysis of 7667 condensate-associated proteins further shows that sequence architectures compatible with strong CTC are common. At the dynamical level, combining simulations with reaction-diffusion modeling reveals that CTC is kinetically feasible within typical polysome lifetimes, either through densely-packed polysomes nucleating new condensates or via diffusion to pre-existing condensates. As an illustrative consequence, we show that CTC can reduce the accumulation of unmodified protein intermediates by localizing their synthesis with condensates, where modification can occur promptly. Together, our results establish physical principles for how translation can couple to phase separation and identify protein architectures and cellular regimes that favor CTC.