I don’t understand why this particular 4th model CONSTANTLY hallucinates, reports the existence of something in the code that is not there and offers such erroneous solutions that I am shocked. The previous Claude 3.7 Sonnet works perfectly. Fellow developers, have you encountered this?
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Same here, Sonnet 4 cannot be trusted at all - some might argue that no AI can be trusted, but 4 is ridiculous, it is lying, cheating, skipping - at least from my pov. I switched back to 3.7 and it will take some convincing to bring me back to that mess.
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I notice the same thing, but only throughout the day. During night, it is perfect, not even comparable, not sure how but during the day it is quite unusable for various reasons and every night, boom, magically it works like a charm.
Its literally the load in a specific regional server center and how the connection from your internet to that area is routed.
In my area lots of people complain to have so many issues with certain models, where I’m prompting the same model and its super smooth (but I use VPN which improves my connection and likely re-routes the request to better regional hub).
For Sonnet 4 hallucinations, each model requires some adjustments on prompts and to get a feeling for how to instruct it. Best is to start small and build up in complexity.
It happens to me often with well working prompts on one model, when i switch to another its compleltey useless. So for some tasks I still use Claude 3.5 Sonnet because its just performing so well.
We might need a library of well working prompts and stuff that makes responses better or worse.
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Something special happened from last night to this morning (NY time). Claude 4.0 started fixing issues without a blink…I am sure something happened in the backend after all the ranting in this forum.
Thank you!
No the ranting didnt particularly help but users who reported issues helped identify causes 
still ■■■■■ actually imagining stuff that doesnt exist and not following clear instructions dont recommend 3.7 is still much better
It’s been a long time, eventually I’ve pretty much given up on claude 4 sonnet, I only use gemini 2.5 pro and o3. I don’t understand how you can use claude 4 in real tasks that require accuracy, it’s only good for jokes. 