---
url: /docs/5.x/reference/diagnostics/kubb-format-failed.md
description: >-
  The KUBB_FORMAT_FAILED diagnostic fires when the formatter pass over the
  generated files fails.
---

# KUBB\_FORMAT\_FAILED: Format failed

Code: `KUBB_FORMAT_FAILED`
Level: error

The formatter pass over the generated files failed. Formatting runs after generation. The files are written, but the run is marked failed.

## What happened

When `output.format` is set, Kubb runs the configured formatter (oxfmt, biome, or prettier) over the output directory. A non-zero exit from the formatter shows up here, in the summary, and in `--reporter json`. Earlier versions swallowed it, so a broken formatter config went unnoticed.

## How to fix it

* Confirm the formatter is installed and its config is valid.
* Run it manually on the output to see the underlying error, for example `biome check --write ./src/gen`.
* Remove or change `output.format` if you do not want a formatter pass.

## Common causes

* The formatter is not installed in the project.
* The formatter config is invalid or points at a missing file.
* The formatter rejects the generated code.

## Example output

```text [Terminal]
[KUBB_FORMAT_FAILED]: formatter failed: Cannot find module 'oxfmt'
  fix: Check that the tool is installed and that the command and its config are correct.
  see: https://kubb.dev/docs/5.x/reference/diagnostics/kubb-format-failed
```

## See also

* [Configuration](/docs/5.x/reference/configuration)
* [`KUBB_LINT_FAILED`](/docs/5.x/reference/diagnostics/kubb-lint-failed)
* [Diagnostics reference](/docs/5.x/reference/diagnostics)