Pro Plan disbelief - Good for cooking recipes, bad for anything complex

Sonnet 4 is so weird, or it has been programmed to fail after the project grows. I was having good time vibing with it, but once couple of files hit 1000 rows, it magically went insane. Project instructions - who cares, my requests - well I'll do something else etc. Insane!

I can use Opus 4 to get sane answers for the same project, but pro plan hits the limits after - one 1000 row document. ONE.

So stupid. Are they trying to push open source coding LLM's to take over? Twenty bucks gives you nothing, but kick ass curry recipes.