Why AI API providers have reached sustainable product-market fit

Simon Willison argues that Anthropic and OpenAI have moved beyond the hype cycle—they've found genuine, durable product-market fit as API providers. The signals are clear: developer adoption is sticky, pricing models are stable, and the competitive moat around model quality and reliability keeps customers locked in. For indie makers, this means the era of free-tier experimentation is ending; building on these platforms now requires serious commitment to long-term costs.