Known Limitations

Most of these fail silently - no error, no warning, just a missing label or a validation message that never appears - so they're worth reading once.

Setup

• Inputs are not auto-registered. The module only adds a plugin, the composables, and FUDataView/FUDataEdit/FUDataDebug/FUAutoForm. The nuxtUI* input and output types exist only once your formkit.config.ts registers them via createNuxtUiFormkitConfig(), and that file is only picked up if @formkit/nuxt is in your modules.
• Multi-step needs its plugin. nuxtUIMultiStep/nuxtUIStep do nothing unless you call createNuxtUiFormkitConfig({ multiStep: true }) (or register createMultiStepPlugin() yourself). In development a nuxtUIMultiStep without the plugin logs a console warning saying so. See Multi-Step.
• Don't override plugins after spreading the helper. defaultConfig({ ...createNuxtUiFormkitConfig(), plugins: [x] }) replaces the whole array and silently drops the asterisk plugin (required fields lose their *). Pass yours as createNuxtUiFormkitConfig({ plugins: [x] }), which appends them.
• Schemas can only use globally registered Nuxt UI components. The module registers UButton, UIcon, UTabs, UUser and UTooltip. Any other $cmp: 'UXxx' in a schema renders as an unstyled custom element.
• Server rendering has a few things that only appear after hydration. The editor is built in the browser (the content below it moves down by about 73px when it mounts), a multi-step's tab strip appears after hydration, and a date field without an explicit timeZone shows the server's day until the page mounts. None of this is a hydration mismatch. See Server-Side Rendering.

Validation timing

FormKit reveals validation messages on blur by default, and Nuxt UI components don't all emit one.

• nuxtUIColorPicker is pointer-only. Nothing inside UColorPicker is focusable, so "blur" means releasing the pointer after picking a color; keyboard users can't operate it at all.
• nuxtUISelect reveals on dropdown close only. Tabbing through without opening it shows nothing. Use 'live', or nuxtUISelectMenu, which has no such gap. See Selection Components.
• required passes for a boolean false. On nuxtUICheckbox/nuxtUISwitch, use the accepted rule instead.

Forms and composables

• useFormKitForm(id) is keyed on the form's id, not its name, and the form must be mounted in the DOM. submit() can't report when FormKit's own submission finishes; isLoading only wraps the handler you pass.
• hasErrors is not !isValid. hasErrors counts only error messages (e.g. from setErrors); a form with failed validation rules reports hasErrors: false. Use isValid for rule failures.
• isDirty is sticky by default - it stays true after a field is edited back to its original value. Set dirty-behavior="compare" (FUDataEdit has a dirtyBehavior prop) to track the live difference.
• Overlays aren't concurrent. useFormKitOverlay().edit()/auto() share one overlay instance; a second call before the first resolves takes it over. See One Overlay Instance at a Time.
• Autosave attaches at form creation only. It needs a stable form name, covers the root form (not nested groups), and can't be added later from useFormKitForm. See createAutosavePlugin.

Repeaters and schemas

• node.at('items.0.email') can't reach into nuxtUIRepeater. The repeater's outer and inner nodes share a name, so FormKit's address lookup fails silently. The Standard Schema bridge works around this; your own code addressing repeater rows has to as well.
• Inside repeater rows, read sibling values with $node.value.<field>. $get(name) resolves by id, not by name.
• The schema expression language has no unary !. if: '!$value' is silently ignored; compare explicitly instead.

Inputs

• Date inputs emit @internationalized/date objects by default (CalendarDate etc.), which aren't JSON-serializable. Set valueType: 'date' or 'iso' for plain values - see nuxtUIInputDate.
• color is overridden while a field is invalid - the wrapped component is switched to its error color.
• FormKit's own label/help/messages chrome always surrounds the Nuxt UI component, so you won't get Nuxt UI's UFormField layout.
• @formkit/addons plugins that assume native FormKit types silently no-op. createMaxLengthCountdownPlugin and createFloatingLabelsPlugin don't work with nuxtUI* types.

FUAutoForm

• Fields it can't map are dropped, not errored. null, undefined, functions and other non-plain values never become inputs; with Zod, only string, number, boolean, date, array and object schemas map - enums, unions and literals are skipped.
• Schema introspection is by duck-typing, tested against Valibot 1.x and Zod 4. Zod 3 isn't supported, and other Standard Schema libraries (e.g. ArkType) get no inference - they work for validation, not for building the form.

Localization

Built-in labels are English-only unless noted: "Save"/"Cancel"/"Reset" on FUDataEdit and the overlays, "Keep editing"/"Discard" in the confirmDiscard prompt, "Yes"/"No" on FUOutputBoolean, and "Add Item" on the repeater. Multi-step's Previous/Next resolve through FormKit's $ui.prev/$ui.next i18n keys. Most of these can be overridden through props.

Not implemented

UStepper as a multi-step display mode (tabs only), FUOutputAvatar, and FUOutputProgressGroup.