The same experience here: Claude with the pro plan over the summer was really doing a good job. The last 4 weeks? Constant slow-downs or API errors, more halucinating then before, and many mistakes. It appears to me that they are throttling to handle loads that they can't actually handle.

Last 4 weeks have been awful, I have barely used my max in comparison to the month before and it's an active deterrent to use it because you don't know if it's going to work or hit an unpredictable limit before getting to the bottom of getting something working.

I don't feel Claude would do this intentionally, and am reminded how I kept Claude for use for some things but not generally.