Former Sims 4 developer rewrote the sims' AI mid-development

David "Rez" Graham, now director of game programming at San Francisco's Academy of Art University, worked QA on 1999's Sim City 3000 and later served as lead AI programmer on The Sims 4. The AI Graham refers to is the programmed NPC behavior, not generative AI.

Playing a build of the game, he found sims weren’t choosing behaviors or solving motives the way he wanted. With two work machines—one for development and one running the build—he spent about a week working nights on a separate branch to rewrite the core logic, a risky move as the project approached alpha.

Graham approached lead gameplay engineer Peter Ingebretson, walked him through the reasoning, and then admitted he had already implemented the new system. The team gave him time and QA support to debug the changes, and after resolving a large stack of bugs he swapped the new AI into the wider build.

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