# Errors

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

> Stable Tailrace error codes - what each means and where to fix the call site.



Every Tailrace error extends `TailraceError` with a stable `code`. Messages never include detected values - only entity classes, rule paths, and hashes. Each thrown message ends with a docs URL for that code.

| Code                                                          | Class                     | When                                          |
| ------------------------------------------------------------- | ------------------------- | --------------------------------------------- |
| [`POLICY_VIOLATION`](/docs/reference/errors/POLICY_VIOLATION) | `PolicyViolationError`    | A `block` rule matched                        |
| [`POLICY_INVALID`](/docs/reference/errors/POLICY_INVALID)     | `PolicyValidationError`   | Policy document failed validation             |
| [`INVARIANT`](/docs/reference/errors/INVARIANT)               | `InvariantViolationError` | Contract breach (e.g. restore at non-egress)  |
| [`VAULT`](/docs/reference/errors/VAULT)                       | `VaultError`              | Vault storage / crypto / lookup failure       |
| [`RECOGNIZER`](/docs/reference/errors/RECOGNIZER)             | `RecognizerError`         | Recognizer threw while scanning               |
| [`NOT_IMPLEMENTED`](/docs/reference/errors/NOT_IMPLEMENTED)   | `NotImplementedError`     | Specified but not shipped yet (e.g. `review`) |