Factory's @TaylorTheSavage argues that Claude Code and Codex aren't necessarily the best tools for their own AI models, and third-party harnesses can actually outperform them: "One thing that I deeply believed before I started at Factory was that the harnesses created by the model companies are going to be the best for their models. Claude Code is going to be the best for Anthropic models, obviously, and Codex is going to be the best for OpenAI models, obviously." "Starting at Factory, I realized that is just not true at all. You can actually do a lot better than those harnesses, certainly on specific types of workloads, but also even in the general case. Different incentives than you have if you’re building a third-party harness." "Keeping them separate also allows you to not get too overfit towards one model. You need to be able to delegate between the different models, not just models from one particular company." "Like Shelby Cobra, you’ve got tuners of cars that can take a car that’s built by Ford and make it work better than it rolled off the factory line. You get things coming out from one OEM, and then you’ve got other people that tune it aftermarket. I think that’s absolutely true with harnesses and models." @FactoryAI