But, of course, OP is an empirical claim to the contrary, and I'd be curious to see if anyone (who's been capturing data over these timeframes) can replicate the same results and if Anthropic has any comment.
However, I also agree that I haven't seen any robust data from someone tracking it daily/weekly. The handful of sites purporting to do this aren't even running it enough times to hit stat sig.
edit: someone linked one elsewhere in this thread called AI Stupid Level - they "run 7 trials instead of just 1". I don't blame them. Doing this in a statistically sound manner would cost a small fortune.
In any case, I am willing to believe it's possible something degraded, but so far I have not seen any empirical evidence of it since the previous incident with the inference and harness bugs. I lean towards Anthropic probably not intentionally doing anything like this without disclosing it beforehand.
For example "We didn't change any settings, but when GPU use gets high the run time of a prompt is lessened. But you must remember this is always in effect so nothing changed at all. This happens occasionally on random prompts some of the time, and when it's busy it happens all of the time".
In someones eye this would fit the letter of the law but not the spirit of the law that you hold.