> For my tastes telling me "no" instead of hallucinating an answer is a real breakthrough.
It's all anecdata--I'm convinced anecdata is the least bad way to evaluate these models, benchmarks don't work--but this is the behavior I've come to expect from earlier Claude models as well, especially after several back and forth passes where you rejected the initial answers. I don't think it's new.
I can concur that previous models would say "No, that isn't possible" or "No, that doesn't exist". There was one time where I asked it to update a Go module from version X.XX to version X.YY and it would refuse to do so because version X.YY "didn't exist". This back with 3.7 if I recall, and to be clear, that version was released before its knowledge cut off.
I wish I remembered the exact versions involved. I mostly just recall how pissed I was that it was fighting me on changing a single line in my go.mod.
alas, 4.5 often hallucinates academic papers or creates false quotes. I think it's better at knowing that coding answers have deterministic output and being firm there.