# `failure.undeclared_propagation`

Failure that can leave is not listed after `fails`.

Area 4, [Failures](../topics/failures.md); not declinable; the next step is usually the agent's.

```jadpo
type Note = Text {}

type RegistrationClosed = Failure {
    kind: FailureKind.conflict
}

action register(note: Note) -> Note {
    reject RegistrationClosed
}
```

```text
error: `RegistrationClosed` can leave `register`, but its `fails` list doesn't say so
 --> main.jadpo:8:5
  |
8 |     reject RegistrationClosed
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^ rejected here
  reason: `fails` lists exactly the failures that can leave an action, so every caller knows what it must handle.
  next: Add `RegistrationClosed` to `register`'s `fails` list (agent)
  rule: failure.undeclared_propagation
  help: https://jadpo.dev/docs/errors/failure.undeclared_propagation

check failed: 1 error, 1 file
```