Anthropic has had to balance protecting against distillation with avoiding API changes that make the user experience painful.

“And actually something like how do we preserve thinking blocks across turns and make that something that's more required is something that we've explored back for a while. And what we... where we were at was we always have this really, really hard trade-off that we have to make between user experience, like user experience changes that are maybe painful for users of the API versus protection against distillation.”