Fixing Form Error Display with superforms and shadcn-svelte in Svelte 5

Description

Learn how to resolve issues with error messages not appearing in SvelteKit forms using superforms and shadcn-svelte in Svelte 5 with progressive enhancement. --- This video is based on the question https://stackoverflow.com/q/79320873/ asked by the user 'DevOskar' ( https://stackoverflow.com/u/18571385/ ) and on the answer https://stackoverflow.com/a/79368859/ provided by the user 'DevOskar' ( https://stackoverflow.com/u/18571385/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Form Enhancement with Superforms and Shadcn Svelte does not work in svelte 5 Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license. If anything seems off to you, please feel free to drop me a comment under this video. --- Resolving Form Error Display Issues in Svelte 5 with Superforms and shadcn-svelte When building forms in SvelteKit using the superforms library and shadcn-svelte UI components, upgrading to Svelte 5 may cause form error messages not to display as expected—especially when using progressive enhancement. The Problem Error messages set via setError(form, 'email', 'Message') from the load function fail to show on the client. Network requests succeed and send the error payload, but UI does not update. Disabling progressive enhancement makes errors appear normally. Sometimes errors appear randomly after hot reloads. Underlying Cause The root of this strange behavior often lies outside the form code itself. In one reported case, a UI component named ParaglideJS, which may be part of a freshly scaffolded SvelteKit project, caused interference. How to Fix It Step 1: Isolate Conflicting Components Check your root layout (e.g., + layout.svelte) for any pre-installed UI or script components like ParaglideJS. Temporarily comment out these components and test the form error rendering. Step 2: Verify Progressive Enhancement Setup Ensure you are using the use:enhance action properly alongside superforms: Initialize your form with superForm(data.form, { validators: zodClient(formSchema) }). Destructure { form: formData, enhance, submitting } from the superform. Apply use:enhance on the <form> element. Step 3: Confirm Correct Error Passing The error should be set server-side using setError targeting the correct form fields. Confirm that errors are present in the data sent back and bound in $formData. Best Practices with Svelte 5 and Superforms Keep third-party UI/system scripts modular and check for conflicts. Use bind:value={$formData.fieldName} to correctly sync form state. Always handle loading and submitting states gracefully (e.g., disable submit button). Summary If you notice errors sent via superforms aren't showing but the server response indicates success, inspect other layout-level or root components that might interfere with Svelte's reactive updates. Removing or isolating such components often resolves the issue without disabling progressive enhancement. This will restore your form error visibility and maintain smooth progressive enhancement benefits in Svelte 5.