---
url: 'https://adk.nht.io/api/@nhtio/adk/exceptions/variables/E_NOT_A_SPOOL_READER.md'
description: >-
  Thrown when a {@link @nhtio/adk!SpooledArtifact} is constructed with a value
  that does not implement the {@link @nhtio/adk!SpoolReader} interface.
---

# Variable: E\_NOT\_A\_SPOOL\_READER

```ts
const E_NOT_A_SPOOL_READER: CreatedException<[]>;
```

Defined in: [lib/exceptions/runtime.ts:310](https://github.com/NHTIO/ADK/blob/v1.20260605.0/src/lib/exceptions/runtime.ts#L310)

Thrown when a [@nhtio/adk!SpooledArtifact](../../spooled_artifact/classes/SpooledArtifact.md) is constructed with a value that does not implement the
[@nhtio/adk!SpoolReader](../../spooled_artifact/interfaces/SpoolReader.md) interface.

## Remarks

Validated at construction time via [@nhtio/adk!implementsSpoolReader](../../spooled_artifact/functions/implementsSpoolReader.md). Passing anything that lacks
`line`, `byteLength`, or `lineCount` as callable functions signals a programming error in the
caller.