# What is an AI hallucination?

A hallucination is output that is fluent, plausible and false. The model is not malfunctioning when it happens: it is predicting likely text, and a likely sentence is not always a true one. It matters most where the output is a fact somebody will act on, such as a name, a price, or an email address.

Also called: confabulation, made-up output
Checked: 2026-09-27

In one line

Fluent, plausible, false. The model is working as designed.

## Why it matters to you

Treating this as a model-quality problem leads nowhere useful, because a better model hallucinates less often and more convincingly. The fix is structural: do not let a model be the source of a fact it could invent.

In practice that means extraction is checked against the fetched page. On the WhoFits lead engine nothing a model returns is trusted unless the text is literally present in the page that was fetched, which is what stops an invented email address reaching a send queue. Every extracted email then passes five further checks, including a domain match against the business name.

The same idea drives citation in a retrieval system, and it is why an answer with a source attached is a different product from an answer without one.

## Where it turns up in something we run

- Model output is discarded unless the text appears literally in the fetched page, which keeps invented contact details out of the send queue (recorded 2026-04-15, [WhoFits Agency](https://octyn.co/casestudies/whofits-agency))
- An earlier version of the craft retailer's outreach pipeline wrote emails with invented details the brands did not have, which is why drafting now passes a hard lint before it can be queued (recorded 2026-07-29)

## Next to this

- [Retrieval augmented generation](https://octyn.co/glossary/retrieval-augmented-generation)
- [Human in the loop](https://octyn.co/glossary/human-in-the-loop)
- [Dry run](https://octyn.co/glossary/dry-run)

## Argued out at length

- [What production ready means for an AI system](https://octyn.co/compare/production-ready-ai-system)

## Related

- [What production ready means for an AI system](https://octyn.co/compare/production-ready-ai-system)
- [Retrieval augmented generation](https://octyn.co/glossary/retrieval-augmented-generation)
- [The Consult](https://octyn.co/consult)

Canonical: https://octyn.co/glossary/hallucination