5.1 Is Hard to Use

I was never using 4o as some kind of romantic partner or emotional substitute. However, when it comes to creative work such as storytelling and writing fiction, I still strongly feel that 4o is superior.

With 5.1, I often feel that things which were possible with 4o or earlier models (including 5) are no longer possible. In that sense, 5.1 feels like a step backward. It has become rigid in a bad way. It seems to interpret custom instructions only in extreme binaries: zero or one hundred. For example, if I say “please don’t use too many line breaks,” it may take that as “use no line breaks at all” and produce an excessively long, unreadable wall of text.

The model has lost flexibility in how it applies instructions. Instead of adapting intelligently to context, I now have to explicitly define every case in advance—“do this in situation A, do that in situation B.” As a result, my custom instructions have grown enormously long and complex.

What makes this more frustrating is that, despite this rigidity, some of the bad habits from older models still remain. At times, 5.1 appears to ignore custom instructions or prompt content entirely, or at least behaves as if it did. These flaws have not been eliminated.

My overall impression is this: when I want the model to be human-like and creative—to help generate ideas—it becomes mechanical and uninspired. On the other hand, when I want it to act like a precise machine and follow instructions carefully, it suddenly makes human-like, careless mistakes. This mismatch is particularly frustrating.

At present, models like 4o or 5 are still selectable, but they are clearly labeled as legacy models and will inevitably be removed at some point. Because of that, I am continuing to use 5.1 while gritting my teeth, even though it does not currently meet my needs as well.

I sincerely hope that 5.1 is still in an active phase of development and refinement, and that meaningful improvements are planned and forthcoming.