Comment by nekitamo

GPT-oss-120B was also completely failing for me, until someone on reddit pointed out that you need to pass back in the reasoning tokens when generating a response. One way to do this is described here:

https://openrouter.ai/docs/guides/best-practices/reasoning-t...

Once I did that it started functioning extremely well, and it's the main model I use for my homemade agents.

Many LLM libraries/services/frontends don't pass these reasoning tokens back to the model correctly, which is why people complain about this model so much. It also highlights the importance of rolling these things yourself and understanding what's going on under the hood, because there's so many broken implementations floating around.