# RECOGNIZER

URL: https://tailrace.dev/docs/reference/errors/RECOGNIZER

> A recognizer threw while scanning input.



## What it means [#what-it-means]

`RecognizerError` (`code: RECOGNIZER`). A detection engine threw during `scan`.

## Message shape [#message-shape]

```text
<reason> → https://tailrace.dev/docs/reference/errors/RECOGNIZER
```

## Common causes [#common-causes]

1. Custom recognizer bug.
2. Optional Tier 1 engine misconfiguration (should degrade to Tier 0 with a warning - if you see this, the recognizer threw instead of failing open).

## Fixes [#fixes]

1. Fix or remove the custom recognizer.
2. Ensure Tier 1 optional models fail open per product rules - never crash the host for a missing model.

## Safe to catch? [#safe-to-catch]

For `block`-configured entity classes, fail closed if detection cannot run. For availability of optional Tier 1, prefer degrade-to-Tier-0.