Hallucination

A hallucination is an answer from a language model that sounds right and is not: an invented figure, a feature that does not exist, a plausible number nobody checked. It is not a bug, it is a direct consequence of how a model works — it produces the most probable continuation, not the verified one.

What is hallucination?

A hallucination is an answer from a language model that sounds right and is not: an invented figure, a feature that does not exist, a plausible number nobody checked. It is not a bug, it is a direct consequence of how a model works — it produces the most probable continuation, not the verified one.

Also: confabulation · made-up answer

Not a one-off bug waiting for a patch

Hallucinations get discussed as a defect the next version will fix. Producing plausible text and inventing are the same capability, so what you can do is not eliminate them but corner them: limit where the system gets its data and make it recognise when it does not have any.

Why it matters

What changes in a SaaS

In support a hallucination is not a curiosity: it is a customer acting on something false. If the system tells them their plan includes something it does not, or gives an invented refund date, the cost is not the ticket — it is the complaint afterwards and the trust that goes with it.

Primer plano de una placa de circuito

Hallucination in detail

  • How to reduce them

    By forcing the system to answer only from passages retrieved from your documentation and data looked up in your systems, rather than from what the model seems to remember. That is the whole point of RAG.

  • The right answer when it does not know

    "I do not have that, let me get someone from the team." A system that says this is more useful than one that is right 95% of the time and invents the other 5% with equal confidence, because the second one forces you to check everything.

  • Where they hurt most

    In numbers and conditions: prices, deadlines, limits, coverage. Those are the answers customers act on, and the easiest to sound plausible while being false. Those should always come from a lookup, never from the model memory.

Questions about hallucination

Can hallucinations be eliminated?

Not entirely: they follow from how a language model works. You corner them by limiting where the data comes from and designing the system to recognise when it has none.

Why does a model invent things so confidently?

Because it produces the most plausible continuation, and a well-formed false sentence is as plausible as a true one. The model does not distinguish between them — that distinction has to come from outside.

Related terms

A term on its own is only half understood. These come up in the same conversation.

Try it without dropping what you use