## TL;DR

The agent acted on a test name it invented. The rule is simple: never trust a recalled test name; always verify with `dbt ls --select [NAME]` or list tests with `dbt ls --resource-type test` first. If the name does not exist, find the real one before doing anything.

## Error

```text
agent hallucinated a dbt test name that doesn't exist: verification error
```

## Steps

1. Stop and verify: `dbt ls --select [CLAIMED NAME]`. Expected: either the test exists (proceed) or it does not (the hallucination is confirmed).
2. If it does not exist, list the real tests: `dbt ls --resource-type test | grep -i [KEYWORD]`. Expected: the actual test names matching the intent.
3. Match the intent to a real test name and confirm it with one more `dbt ls`. Expected: a verified, exact name.
4. Log the correction (claimed vs actual) so the mistake is visible. Expected: the record shows what happened.
5. Proceed using only the verified name. Expected: no further hallucinated references.

## When to use

- An agent names a dbt test that turns out not to exist.
- Any agent workflow that recalls resource names from memory.

## When not to use

- The test exists but fails (a real test problem, not a hallucination).
- The agent quoted the name from actual command output (that is verification already).

## Tool compatibility

- dbt Core 1.0 and later. `dbt ls` is the source of truth for names.

## Variant phrasings

### Agent ran dbt test --select with a wrong name

`dbt test` with no matches is the symptom; verification is the prevention.

### Agent edited a test file that does not exist

Same rule applied to files: list before editing.

## Why it happens

Language models complete patterns plausibly, and dbt test names follow predictable patterns (`not_null_[MODEL]_[COLUMN]`). Plausible is not the same as real, and acting on a plausible name wastes runs or edits the wrong thing.

## Edge cases

- Test names include the package and test type; a partial name may match nothing even when the test exists.
- Custom test names (singular tests) are the easiest to hallucinate; always list `tests/` too.
- Make verification a habit for every name the agent did not copy from tool output.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_G-XMLRBBhyhRpXZ1LNOAwQ