# React troubleshooting

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## The form is unstyled

Import `form0-react/index.css` once in the application entry point. Confirm that the bundler allows
CSS imports from dependencies.

## A field says it is unsupported

Confirm that the type is listed in the [Core field catalog](/core/fields/catalog). If the type is
known but intentionally replaced, verify that the component is registered in the same
`FieldRegistryProvider` subtree as `FormRenderer`.

## The schema fails during rendering

`FormRenderer` validates `schema.form` and requires `form.elements`. Use
[`form0 validate`](/cli/schemas/validate-preview) before loading the schema in the application.

## Worker mode cannot load the worker

First return to `engineMode="main-thread"`. For Vite, keep the worker constructor statically
analyzable and exclude `form0-react` from dependency optimization as shown in the maintained web
starter. Other bundlers must support ESM module workers based on `new URL(..., import.meta.url)`.

Custom `workerUrl` and `createWorker` options are not part of the public `FormRenderer` API.

## Updates do not appear during local package development

Rebuild `form0-react`, restart the consuming development server, and clear only that bundler’s
dependency cache if necessary. Vite can retain an optimized copy of a linked or previously
installed package.

## Submission does not run

Check that `onSubmit` is a function, the form is in edit mode, `submitBlockedReason` is empty, and
the validation summary has no errors. For overlays returning a promise, handle rejection so the
application can present the failure while the overlay remains open.