"User agent" but do users run LLMs behind their agents on their hardware? No, it's run in an AI datacenter. They can easily make a deal to route that without involving user's machine, or they can route this via user's machine but attach a signature. Of course both parties must agree on that, but technically there's nothing stopping them

No, you only get to use the Adobe LLM, which you pay adobe from. And yes, it runs remotely so they can charge you per-use.