HN turned Mozilla's Prompt API pushback into a browser-AI lock-in warning

Hacker News did not read Mozilla's new objection to Chrome's Prompt API as a dry standards filing. The thread took off because people immediately saw an old web problem returning in a new costume: once developers tune prompts to one model's odd habits, the portable web starts bending around a vendor-specific AI stack.

The Mozilla comment that sparked the discussion lays out three objections. First is interoperability. Jake Archibald argues that system prompts get iterated against the quirks of the model in front of them, which means a prompt that works on Google's model may overcorrect or break on another vendor's model. From there the path gets ugly fast: rival browsers may need to license Google's model or imitate its behavior just to keep sites working. Developers, expecting that risk, could start fingerprinting models and branching prompts by vendor, which HN compared to the browser-specific code paths the web spent years trying to escape.

The second objection is updateability. If web apps quietly depend on one model's personality, even Chrome's own model upgrades become risky. A better model can still feel worse if all the prompts in the wild were tuned to yesterday's quirks. That line landed on HN because it frames AI drift not as a lab problem but as a platform problem. Top comments pushed the idea further: some suggested browsers would need a shared pool of standard models, while others questioned the assumption that browsers should ship this class of API before the ecosystem has a neutral way to target it.

The third issue is neutrality. Mozilla points to Chrome documentation that requires developers to acknowledge Google's generative AI use policy before using the API. HN readers saw that as more than legal fine print. If a site adds a summarize button and the underlying model has vendor-specific content rules, responsibility gets muddy fast: is the user, the site owner, or the model provider on the hook when things go sideways? That uncertainty gives developers even more reason to detect which model is behind the browser and tailor behavior around it.

That is why the thread had energy. HN was not arguing about whether browser AI is cool. It was arguing about whether the first popular browser AI API is quietly reintroducing lock-in, compatibility hacks, and terms-of-service baggage at the exact layer the web usually tries hardest to keep neutral.