diff --git a/frontend/src/components/Initializers/AdditionalInitializers.test.tsx b/frontend/src/components/Initializers/AdditionalInitializers.test.tsx
index d0d0438436..c05d401cd8 100644
--- a/frontend/src/components/Initializers/AdditionalInitializers.test.tsx
+++ b/frontend/src/components/Initializers/AdditionalInitializers.test.tsx
@@ -365,4 +365,35 @@ describe('AdditionalInitializers', () => {
 
     expect(defaultProps.onAdd).toHaveBeenCalledWith('load_default_datasets', null)
   })
+
+  it('should show a server error inside the add dialog when onAdd fails', async () => {
+    const user = userEvent.setup()
+
+    const props = {
+      ...defaultProps,
+      registeredInitializers: [refreshInitializer],
+      onAdd: jest.fn().mockRejectedValue(new Error('Invalid days value.')),
+    }
+
+    render(
+      <TestWrapper>
+        <AdditionalInitializers {...props} />
+      </TestWrapper>,
+    )
+
+    fireEvent.change(screen.getByRole('combobox', { name: 'Initializer to add' }), {
+      target: { value: 'refresh_datasets' },
+    })
+    await user.click(screen.getByRole('button', { name: 'Add initializer' }))
+
+    const dialog = await screen.findByRole('dialog', {}, { timeout: 3000 })
+    await within(dialog).findByText('Add refresh_datasets initializer')
+    fireEvent.change(within(dialog).getByTestId('param-days'), { target: { value: '12' } })
+    await user.click(await within(dialog).findByRole('button', { name: 'Add', hidden: true }))
+
+    expect(await within(dialog).findByRole('alert', { hidden: true })).toHaveTextContent(
+      'Invalid days value.',
+    )
+    expect(dialog).toBeInTheDocument()
+  })
 })
diff --git a/frontend/src/components/Initializers/AdditionalInitializers.tsx b/frontend/src/components/Initializers/AdditionalInitializers.tsx
index 9ad4a8c06a..e415eba4a7 100644
--- a/frontend/src/components/Initializers/AdditionalInitializers.tsx
+++ b/frontend/src/components/Initializers/AdditionalInitializers.tsx
@@ -14,6 +14,7 @@ import type {
   UpdateAdditionalInitializerRequest,
 } from '@/types'
 
+import { toApiError } from '@/services/errors'
 import { useAdditionalInitializersStyles } from './AdditionalInitializers.styles'
 import { formatInitializerParameters, formatSupportedParameterSummary } from './initializerFormatting'
 import { resolveRegisteredInitializer } from './initializerLookup'
@@ -153,6 +154,7 @@ export default function AdditionalInitializers({
   const listStyles = useAdditionalInitializersStyles()
   const [selectedInitializerName, setSelectedInitializerName] = useState('')
   const [addDialogOpen, setAddDialogOpen] = useState(false)
+  const [addError, setAddError] = useState<string | null>(null)
   const initializerName = selectedInitializerName || registeredInitializers[0]?.initializer_name || ''
   const selectedInitializer = registeredInitializers.find(
     (initializer) => initializer.initializer_name === initializerName,
@@ -162,9 +164,14 @@ export default function AdditionalInitializers({
     if (!initializerName) {
       return
     }
-    const added = await onAdd(initializerName, parameters)
-    if (added) {
-      setAddDialogOpen(false)
+    setAddError(null)
+    try {
+      const added = await onAdd(initializerName, parameters)
+      if (added) {
+        setAddDialogOpen(false)
+      }
+    } catch (e) {
+      setAddError(toApiError(e).detail)
     }
   }
 
@@ -231,8 +238,14 @@ export default function AdditionalInitializers({
           initializer={selectedInitializer}
           initialParameters={null}
           submitting={creating}
+          externalError={addError}
           onSubmit={handleAdd}
-          onOpenChange={setAddDialogOpen}
+          onOpenChange={(open) => {
+            setAddDialogOpen(open)
+            if (!open) {
+              setAddError(null)
+            }
+          }}
         />
       )}
     </section>
diff --git a/frontend/src/components/Initializers/InitializerParametersDialog.test.tsx b/frontend/src/components/Initializers/InitializerParametersDialog.test.tsx
index d0fda42461..5fa0d84c73 100644
--- a/frontend/src/components/Initializers/InitializerParametersDialog.test.tsx
+++ b/frontend/src/components/Initializers/InitializerParametersDialog.test.tsx
@@ -207,4 +207,18 @@ describe('InitializerParametersDialog', () => {
     expect(screen.getByRole('button', { name: 'Add...' })).toBeDisabled()
     expect(screen.getByRole('button', { name: 'Cancel' })).toBeDisabled()
   })
+
+  it('displays an external error passed via externalError prop', () => {
+    render(
+      <TestWrapper>
+        <InitializerParametersDialog
+          {...baseProps}
+          initializer={numericInitializer}
+          externalError="Server rejected the request."
+        />
+      </TestWrapper>,
+    )
+
+    expect(screen.getByRole('alert')).toHaveTextContent('Server rejected the request.')
+  })
 })
diff --git a/frontend/src/components/Initializers/InitializerParametersDialog.tsx b/frontend/src/components/Initializers/InitializerParametersDialog.tsx
index 44e8ba832d..1d2c56dd8f 100644
--- a/frontend/src/components/Initializers/InitializerParametersDialog.tsx
+++ b/frontend/src/components/Initializers/InitializerParametersDialog.tsx
@@ -31,6 +31,7 @@ interface InitializerParametersDialogProps {
   initializer: RegisteredInitializer | null
   initialParameters?: Record<string, unknown> | null
   submitting?: boolean
+  externalError?: string | null
   onSubmit: (parameters: Record<string, unknown> | null) => void | Promise<void>
   onOpenChange: (open: boolean) => void
 }
@@ -41,6 +42,7 @@ export default function InitializerParametersDialog({
   initializer,
   initialParameters = null,
   submitting = false,
+  externalError = null,
   onSubmit,
   onOpenChange,
 }: InitializerParametersDialogProps) {
@@ -112,9 +114,9 @@ export default function InitializerParametersDialog({
                 This initializer takes no parameters.
               </Text>
             )}
-            {error && (
+            {(error || externalError) && (
               <Text role="alert" className={styles.errorText}>
-                {error}
+                {error || externalError}
               </Text>
             )}
           </DialogContent>
diff --git a/frontend/src/components/Initializers/Initializers.tsx b/frontend/src/components/Initializers/Initializers.tsx
index 684f085675..6b2c6f2f4b 100644
--- a/frontend/src/components/Initializers/Initializers.tsx
+++ b/frontend/src/components/Initializers/Initializers.tsx
@@ -94,8 +94,9 @@ export default function Initializers() {
       await refetchSettingsOnly()
       return true
     } catch (error) {
-      setStatusMessage({ intent: 'error', text: toApiError(error).detail })
-      return false
+      const detail = toApiError(error).detail
+      setStatusMessage({ intent: 'error', text: detail })
+      throw error
     } finally {
       setCreating(false)
     }