Slots, intercepts, and React errors

Route "..." declares layout.errorFallback, but layout errorFallback is no longer supported. Use layout.error instead.

Symptom A layout using an old fallback API fails validation.

Cause The removed layout.errorFallback field is still present.

Fix Rename layout.errorFallback to layout.error.

Route "..." declares layout.loading/layout.error, but no active layout view exists.

Symptom Validation fails on layout fallback fields.

Cause layout.loading or layout.error is declared where neither the route nor an ancestor has layout.view.

Fix Use route.loading/route.error for route-local fallbacks or declare layout.view on this route or an ancestor.

Route "..." declares layout.slots, but no active layout view exists in its ancestor tree.

Symptom Validation fails on layout.slots.

Cause Slots were declared without an active layout view to render them.

Fix Declare layout.view on the same route or an ancestor route, or remove layout.slots.

Route "..." layout.slots must be an object.

Symptom Validation fails on layout.slots.

Cause layout.slots was provided but is not an object.

Fix Use layout.slots: { name: true } or layout.slots: { name: { view, meta, routes } }.

Route "..." defines a slot with an empty name.

Symptom Validation fails while reading slot entries.

Cause layout.slots contains an empty-string key.

Fix Use a non-empty slot name such as header, sidebar, or modal.

Missing slot "..." for route "...".

Symptom Validation fails on a child slot declaration.

Cause A child route declares layout.slots.<name>, but no active ancestor layout declares that slot and the current route does not own a layout view.

Fix Declare the slot on an active ancestor layout or remove the child slot declaration.

Route "..." declares invalid configuration for slot "...".

Symptom Validation fails on a slot value.

Cause The slot is false, null, undefined, or otherwise not a supported slot declaration.

Fix Use true, a slot view component, or an object with view, meta, and/or routes.

Route "..." defines invalid configuration for slot "...".

Symptom Validation fails on a slot config object.

Cause The slot config is null, an array, or another invalid value where an object config was expected.

Fix Use a valid slot config object.

Route "..." declares "layout.slots....id", but slot IDs are no longer supported.

Symptom Validation fails on a removed slot field.

Cause The slot config still uses the removed id property.

Fix Remove layout.slots.<name>.id. The slot key is the slot identity.

Unsupported slot fallback: slot fallbacks are no longer supported on route "...".

Symptom Validation fails on a removed slot field.

Cause The slot config still uses the removed fallback property.

Fix Remove layout.slots.<name>.fallback. Use the slot declaration itself and render fallback UI from the layout if needed.

Unsupported slot key "..." on route "...".

Symptom Validation fails on an unknown slot config key.

Cause The slot config contains a key other than view, meta, or routes.

Fix Remove the unsupported key or move that information into slot meta.

Route "..." slot "..." routes must be an array.

Symptom Validation fails on slot routes.

Cause layout.slots.<name>.routes was provided but is not an array.

Fix Use routes: [...] or omit routes.

Route "..." intercepts must be an object.

Symptom Validation fails on intercepts.

Cause intercepts was provided but is not an object.

Fix Use intercepts: { slotName: { to, view } } or remove intercepts.

Route "..." defines an intercept with an empty slot name.

Symptom Validation fails while reading intercept entries.

Cause intercepts contains an empty-string key.

Fix Use a non-empty slot name that matches a declared layout slot.

Route "..." intercept for slot "..." must be an object.

Symptom Validation fails on an intercept config.

Cause The intercept slot value is missing, null, or not an object.

Fix Use { to: "target.route", view: InterceptView }.

Invalid intercept slot "..." on route "...".

Symptom Validation fails because the intercept slot is not declared.

Cause The route configures an intercept for a slot that is not declared on this route or an active ancestor layout.

Fix Declare layout.slots.<name> on the source route layout or an active ancestor layout, or remove the intercept.

Route "..." intercept for slot "..." must define view.

Symptom Validation fails on an intercept config.

Cause The intercept config does not provide a view.

Fix Add the intercept view component.

Route "..." intercept for slot "..." must define at least one target route id.

Symptom Validation fails on intercept.to.

Cause The intercept target list is empty.

Fix Provide a target route id string or a non-empty array of target route ids.

Route "..." intercept for slot "..." defines an empty target route id.

Symptom Validation fails on intercept.to.

Cause The intercept target string or one of the target array entries is empty.

Fix Replace it with a valid target route id.

Route "..." intercept "..." targets unknown route id "...".

Symptom Validation fails after all routes have been collected.

Cause The intercept points to a route id that does not exist in the route tree.

Fix Fix the target route id or add the missing route.

use... must be used inside <RouterProvider> or <StaticRouterProvider>.

Cause: a router hook read RouterContext outside either provider.

Fix: render the component under RouterProvider or StaticRouterProvider. Moving only the hook into a helper does not create context.

Outlet context ... was requested in strict mode, but no context was provided ...

Cause: useOutletContext({ strict: true }) ran without context from the parent Outlet or Slot.

Fix: provide context at the rendering outlet/slot, or use non-strict access when absence is valid.

Slot errors replace a larger route boundary

This is not a validation error. Without errorFallback, a thrown slot view intentionally bubbles to the nearest route/provider boundary. Set errorFallback={null}, a component, or a render function on <Slot /> to isolate the failure.