[astrange]

They don't ever fall back to cheaper models silently.

What Anthropic does do is poke the model to tell you to go to bed if you use it too long ("long conversation reminder") which distracts it from actually answering.

Sometimes they do have associations with things like the day of the year and might be lazier some months than others.

[pankajdoharey]

If they are real slime balls they can justify it by saying you see we use speculative decoding so we first use a smaller faster model model first and then then answer is enhanced by larger model blah blah ..... "FOr the best User experience"