If you have such a world changing technology, why sell an API when you can capture all the value yourself? That's what every provider is asking themselves.
Cursor will be fine after this, as they have their own first party models and can potentially use open weight models via API or their own hardware, which have gotten good enough to Opus and Fable quality now for many use cases.
Being a pure play model provider is completely untenable right now. Coding agents own your demand; Nvidia, data centers, and DRAM manufacturers own your supply. You're getting squeezed by open weight models. Your only bet to making money off this thing is by locking your model down to your program to have some semblance of a moat. The fact that businesses can change providers with just the change of an API key is unsustainable. You have neither the "hard to switch" lock-in of a traditional software company nor do you have the near-zero marginal cost of production they have. Each token of inference costs you money, not to mention the training costs. At least locking the models down to your harness lets you get some sort of lock-in.