I used to be able to see a “prettified” version of the JSON output in the OpenAI Traces panel/dashboard (for my agents). It’s now just bunched-up JSON.
I now need to use a third party to be able to easily read it (i.e., make it “pretty”).
The toggle “Format as text” / “Format as JSON” icon next to the “assistant” label does nothing.
This may not be a bug by the way some of GPT-5 models work. Specifically the JSON output might be a result of changes for CFG (related to structured outputs).
While I can not directly answer your questions, I am thinking that with the changes to GPT-5 models, e.g. CFG, the models now create a more specific form of JSON via CFG and thus the nice formatting is no longer returned.
I also suspect that if you provide a different CFG for creating JSON, it should be able to produce the nicely formatted JSON you seek.
At present this is the best related post to CFG on this forum
In particular pay attention to the replies by Michal_Moskal