In VS Code there is simply a button at the bottom to pick what LLM model you want to use, I haven't been able to figure out how to do it in IntelliJ.
More specifically I would like to use Claude Sonnet, if anyone knows a work around.
The IntelliJ plugin lags behind the VSCode plugin and switching models is not implemented (which sucks).
If you want to chat, you can go to the copilot chat page on github and select a different model. The main drawback is that the model won't have access to the context in IntelliJ so you would need to provide more data in your questions.
Another alternative is to have the project open on VSCode too and do any heavy chat there.
It's a real shame as o1 and GPT 4o often fail to answer questions or they go into a loop repeating the last 2 answers compared to Claude 3.5.