I think LLMs are fine for a "first pass" on a topic, but if I am researching something, I want a primary source rather than just the LLM-generated output. Do they have the primary source?

No different from what people said about Wikipedia when it was new (and justifiably so). How should one deal with people who trust Wikipedia?

Ask the nice AI to cite sources, and then have another AI fact check their sources. The agentic era is interesting.