Claude finally bit me with a surprising hallucination on a simple fact...

I use Claude extensively, 20x plan, in Chat, in Code, and in Cowork. Despite all the complaints in recent times about quality degradation, usage limits, etc., I've never once run into those problems. In fact, the only time I've had any real complaint is when there were periods of outages/downtime, but that's life, I guess I've just been a lucky guy.

However, this morning, when doing some very simple client research with web search enabled, on a task that wouldn't strain even a far simpler model, I was stunned to see Opus 4.6 give me this shocker:

"June 5 is a Thursday in 2027 — worth confirming whether that's the actual ceremony date or if they're looking at the surrounding weekend (June 5-6-7)"

Ummm, Excuse me. June 5 is a Saturday.

While I can still occasionally see some hallucinations pop up, particularly in long context windows and with complex topics, it's still pretty rare and often something subtle and hard to verify. This one... wow.

On one hand, it was easy enough for me to spot and double-check. On the other hand, it's amazing how much this has shaken my confidence about Claude. It's still the best out there, and I'll still be using it, but now my entire morning has this sense of anxiety. Not a pleasant feeling :\

Has anyone seem an uptick in hallucinations on simple facts in recent times? Or was this just an unfortunate one-off for me?