OpenAI describes Deployment Simulation, a method for previewing how a candidate model will behave in the real world before release by replaying recent, de-identified production conversations with the new model. This episode reads OpenAI's write-up in full and closes with a deeper, paper-based look at the technical methodology: the five-step resampling pipeline, how forecast error is decomposed, and the tool-simulator affordances that make agentic simulation realistic.