Broken Form Validation in Vibecoded Apps

Broken form validation shows up in several ways. Fields may accept clearly invalid data like letters in phone number fields or malformed email addresses. Alternatively, overly strict validation rejects legitimate inputs — international phone formats, plus-addressed emails, or names with hyphens and apostrophes.

Another common symptom is silent failure. The user submits the form, nothing visibly happens, and no error message appears. In vibecoded apps, AI often wires up validation logic that throws errors to the console but never surfaces them in the UI. Check your browser console while testing forms to catch these hidden failures.

Start with boundary testing. Enter empty strings, single characters, maximum-length inputs, and special characters like angle brackets, quotes, and Unicode emoji. Try pasting data instead of typing it, as some validation only triggers on keypress events and misses pasted input entirely.

Test required field enforcement by submitting with each required field left empty one at a time. Then test combinations of invalid fields. Many vibecoded apps only validate the first field and stop, leaving subsequent errors unreported until the user fixes each one in sequence.

The fix usually involves adding both client-side and server-side validation. Client-side gives instant feedback; server-side prevents bad data from ever reaching your database. AI tools often generate only one or the other.

Use a validation library like Zod or Yup rather than hand-rolled regex patterns. These libraries handle edge cases that AI-generated regex consistently misses. Make sure error messages are specific and positioned next to the relevant field, not in a generic banner at the top of the form.