---
title: "format_check: error code"
description: "aontu error code format_check: class internal: the engine surprised itself. Introduced in 0.56.0."
source: "https://aontu.dev/errors/format_check/"
---

[← every error code](https://aontu.dev/errors)

# `format_check`

Class

[`internal`](https://aontu.dev/errors#internal)

Since

`0.56.0`

Kind

fixed code

## What it means

the engine surprised itself.

## What to do

a bug worth reporting

## Where this comes from

[`test/spec/errcodes.tsv`](https://github.com/aontu-lang/aontu/blob/main/test/spec/errcodes.tsv), the shared registry both implementations execute and assert set equality against. The _message text_ is deliberately not reproduced here: the engines are its catalogue, and a copy on this site would be a second source of truth for something already generated once. To read it, run the engine: or see [the skill's error-code guide](https://github.com/aontu-lang/aontu/blob/main/docs/skill/error-codes.md).

This page as data: [`/errors/format_check.json`](https://aontu.dev/errors/format_check.json)