How are people defining agency? Because GPT-4 can have agency, it just needs to be put in specific situations to have that agency. For example, I could theoretically hook up my Home Assistant instance to GPT-4 and run a script every 10 minutes telling GPT-4 the temperature and asking for a yes or no response to whether I should turn on the AC or heat. That sounds to me like the AI now has agency over the temperature…
You can have it access to actions/tools with an inner monologue as the driver of completions running essentially forever.