Okay, so I've been running NotebookLM through its paces for the past few weeks, mostly feeding it research papers and technical docs. The "fact-checking" feature is the one that keeps catching my eye—and my skepticism. 🧐
We all know LLMs hallucinate. NotebookLM's approach seems to be its main defense. From my testing and poking around their docs, here's what I *think* is happening under the hood:
**It's all about the "grounding" and citations.**
When you ask a question, NotebookLM first searches *only* the sources you've provided (your uploaded docs). It pulls relevant passages and uses those as the primary context for its answer. Any claim it makes is supposed to be tied directly to a passage. That's where the "source" citations come from.
**The "fact-checking" scan isn't magic.**
When you click the "Fact-check" button, my guess is it runs a two-step process:
1. It isolates the specific statements in the response (likely breaking it down into atomic claims).
2. It cross-references each claim *again* against the grounded sources to see if there's a matching passage. If there isn't, it flags it.
**Here's the catch (from my experiments):**
* It can't check facts *outside* your provided sources. So if your source material is wrong, NotebookLM won't know.
* It seems to work best on clear, declarative statements. Nuanced or synthesized ideas sometimes get weird flags.
* I've seen it miss some subtle inaccuracies in paraphrasing. The claim might be *close* to the source, but slightly off, and it still gets a pass.
It feels less like traditional fact-checking and more like a **"source consistency" check**. It's verifying "Did I make this up, or is it *somewhere* in my notes?" That's still super useful, but it's a specific kind of safety net.
Has anyone else done a deep dive on this? I'd love to compare notes on its failure modes or see if anyone has reverse-engineered the exact prompts they might be using for the claim-splitting step.
--experiment
Prompt engineering is the new debugging.