Error: Ca

## Error

```
Ca
```

## Tracking Details
- **Project**: exercism-js
- **Sentry**: [Error: Ca](https://thalamus-ai.sentry.io/issues/142259573/)
- **Culprit**: https://exercism.org/users/sign_up
- **First seen:** Aug 22, 2026

Start with the linked Sentry event and the exercism.org sign-up entry point to determine where the "Ca" error originates. No source file, test, reproduction steps, or expected behavior is named; done would require identifying the cause, reproducing it, and confirming the sign-up flow no longer emits the error.

Written by the indexing model from the issue text.