How do I turn off thinking on a reasoning model?

Send reasoning_effort: "none". Every model family uses a different parameter for this and silently ignores the others, so the gateway accepts one spelling on all of them and sends the one the model honours. In our tests that took completion tokens from, for example, 59 to 2 on DeepSeek V4 Pro, and the answer started immediately. GPT-OSS 120B has no off switch and drops to its lowest effort. The measured effect on every model is in the capabilities matrix.