Yes. Most common failure mode for sota models is to put ```json\n first, but they often do just fail often enough to be worth calling api with json response schema.
1000% I was just doing some spot checking of GPT-5.2 for evaluating model migration and the tool I used didn't have the setup to use schema constrained inference.
The model is like:
"Here is what I came up with... ```{json}``` and this is why I am proud of it!"
