diff --git a/src/components/admin/DesignerForm.tsx b/src/components/admin/DesignerForm.tsx
index a0cb554f..485d035c 100644
--- a/src/components/admin/DesignerForm.tsx
+++ b/src/components/admin/DesignerForm.tsx
@@ -83,6 +83,8 @@ export function DesignerForm({ onSubmit, onCancel, initialData }: DesignerFormPr
               ...data,
               company_type: 'designer' as const,
               founded_year: data.founded_year ? parseInt(String(data.founded_year)) : undefined,
+              founded_date: undefined,
+              founded_date_precision: undefined,
               banner_image_id: undefined,
               banner_image_url: undefined,
               card_image_id: undefined,
diff --git a/src/components/admin/OperatorForm.tsx b/src/components/admin/OperatorForm.tsx
index d29f6fb2..a1ff84ee 100644
--- a/src/components/admin/OperatorForm.tsx
+++ b/src/components/admin/OperatorForm.tsx
@@ -83,6 +83,8 @@ export function OperatorForm({ onSubmit, onCancel, initialData }: OperatorFormPr
               ...data,
               company_type: 'operator' as const,
               founded_year: data.founded_year ? parseInt(String(data.founded_year)) : undefined,
+              founded_date: undefined,
+              founded_date_precision: undefined,
               banner_image_id: undefined,
               banner_image_url: undefined,
               card_image_id: undefined,
diff --git a/src/components/admin/PropertyOwnerForm.tsx b/src/components/admin/PropertyOwnerForm.tsx
index 83469e2e..abf2c8d7 100644
--- a/src/components/admin/PropertyOwnerForm.tsx
+++ b/src/components/admin/PropertyOwnerForm.tsx
@@ -83,6 +83,8 @@ export function PropertyOwnerForm({ onSubmit, onCancel, initialData }: PropertyO
               ...data,
               company_type: 'property_owner' as const,
               founded_year: data.founded_year ? parseInt(String(data.founded_year)) : undefined,
+              founded_date: undefined,
+              founded_date_precision: undefined,
               banner_image_id: undefined,
               banner_image_url: undefined,
               card_image_id: undefined,
diff --git a/src/components/admin/RideForm.tsx b/src/components/admin/RideForm.tsx
index 62d79f04..61328cde 100644
--- a/src/components/admin/RideForm.tsx
+++ b/src/components/admin/RideForm.tsx
@@ -661,7 +661,7 @@ export function RideForm({ onSubmit, onCancel, initialData, isEditing = false }:
               <div className="grid grid-cols-1 md:grid-cols-3 gap-6">
                 <div className="space-y-2">
                   <Label>Coaster Type</Label>
-                  <Select onValueChange={(value) => setValue('coaster_type', value)} defaultValue={initialData?.coaster_type}>
+                  <Select onValueChange={(value) => setValue('coaster_type', value)} defaultValue={initialData?.coaster_type ?? undefined}>
                     <SelectTrigger>
                       <SelectValue placeholder="Select type" />
                     </SelectTrigger>
@@ -677,7 +677,7 @@ export function RideForm({ onSubmit, onCancel, initialData, isEditing = false }:
 
                 <div className="space-y-2">
                   <Label>Seating Type</Label>
-                  <Select onValueChange={(value) => setValue('seating_type', value)} defaultValue={initialData?.seating_type}>
+                  <Select onValueChange={(value) => setValue('seating_type', value)} defaultValue={initialData?.seating_type ?? undefined}>
                     <SelectTrigger>
                       <SelectValue placeholder="Select seating" />
                     </SelectTrigger>
@@ -693,7 +693,7 @@ export function RideForm({ onSubmit, onCancel, initialData, isEditing = false }:
 
                 <div className="space-y-2">
                   <Label>Intensity Level</Label>
-                  <Select onValueChange={(value) => setValue('intensity_level', value)} defaultValue={initialData?.intensity_level}>
+                  <Select onValueChange={(value) => setValue('intensity_level', value)} defaultValue={initialData?.intensity_level ?? undefined}>
                     <SelectTrigger>
                       <SelectValue placeholder="Select intensity" />
                     </SelectTrigger>
@@ -846,7 +846,7 @@ export function RideForm({ onSubmit, onCancel, initialData, isEditing = false }:
 
                 <div className="space-y-2">
                   <Label>Wetness Level</Label>
-                  <Select onValueChange={(value) => setValue('wetness_level', value as 'dry' | 'light' | 'moderate' | 'soaked')} defaultValue={initialData?.wetness_level}>
+                  <Select onValueChange={(value) => setValue('wetness_level', value as 'dry' | 'light' | 'moderate' | 'soaked')} defaultValue={initialData?.wetness_level ?? undefined}>
                     <SelectTrigger>
                       <SelectValue placeholder="Select wetness level" />
                     </SelectTrigger>
@@ -969,7 +969,7 @@ export function RideForm({ onSubmit, onCancel, initialData, isEditing = false }:
               <div className="grid grid-cols-1 md:grid-cols-3 gap-6">
                 <div className="space-y-2">
                   <Label>Rotation Type</Label>
-                  <Select onValueChange={(value) => setValue('rotation_type', value as 'horizontal' | 'vertical' | 'multi_axis' | 'pendulum' | 'none')} defaultValue={initialData?.rotation_type}>
+                  <Select onValueChange={(value) => setValue('rotation_type', value as 'horizontal' | 'vertical' | 'multi_axis' | 'pendulum' | 'none')} defaultValue={initialData?.rotation_type ?? undefined}>
                     <SelectTrigger>
                       <SelectValue placeholder="Select rotation type" />
                     </SelectTrigger>
@@ -1114,7 +1114,7 @@ export function RideForm({ onSubmit, onCancel, initialData, isEditing = false }:
               <div className="grid grid-cols-1 md:grid-cols-3 gap-6">
                 <div className="space-y-2">
                   <Label>Transport Type</Label>
-                  <Select onValueChange={(value) => setValue('transport_type', value as 'train' | 'monorail' | 'skylift' | 'ferry' | 'peoplemover' | 'cable_car')} defaultValue={initialData?.transport_type}>
+                  <Select onValueChange={(value) => setValue('transport_type', value as 'train' | 'monorail' | 'skylift' | 'ferry' | 'peoplemover' | 'cable_car')} defaultValue={initialData?.transport_type ?? undefined}>
                     <SelectTrigger>
                       <SelectValue placeholder="Select transport type" />
                     </SelectTrigger>
diff --git a/src/lib/entityValidationSchemas.ts b/src/lib/entityValidationSchemas.ts
index cd756c68..790079f1 100644
--- a/src/lib/entityValidationSchemas.ts
+++ b/src/lib/entityValidationSchemas.ts
@@ -25,24 +25,24 @@ const imageAssignmentSchema = z.object({
 export const parkValidationSchema = z.object({
   name: z.string().trim().min(1, 'Park name is required').max(200, 'Name must be less than 200 characters'),
   slug: z.string().trim().min(1, 'Slug is required').regex(/^[a-z0-9-]+$/, 'Slug must contain only lowercase letters, numbers, and hyphens'),
-  description: z.string().trim().max(2000, 'Description must be less than 2000 characters').optional().or(z.literal('')),
+  description: z.string().trim().max(2000, 'Description must be less than 2000 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
   park_type: z.string().min(1, 'Park type is required'),
   status: z.enum(['operating', 'closed_permanently', 'closed_temporarily', 'under_construction', 'planned', 'abandoned']),
-  opening_date: z.string().optional().or(z.literal('')).refine((val) => {
+  opening_date: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined).refine((val) => {
     if (!val) return true;
     const date = new Date(val);
     return date <= new Date();
   }, 'Opening date cannot be in the future'),
-  opening_date_precision: z.enum(['day', 'month', 'year']).optional(),
-  closing_date: z.string().optional().or(z.literal('')),
-  closing_date_precision: z.enum(['day', 'month', 'year']).optional(),
+  opening_date_precision: z.enum(['day', 'month', 'year']).nullable().optional(),
+  closing_date: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  closing_date_precision: z.enum(['day', 'month', 'year']).nullable().optional(),
   location_id: z.string().uuid().optional().nullable(),
-  website_url: z.string().trim().optional().or(z.literal('')).refine((val) => {
+  website_url: z.string().trim().nullable().optional().or(z.literal('')).transform(val => val || undefined).refine((val) => {
     if (!val || val === '') return true;
     return z.string().url().safeParse(val).success;
   }, 'Invalid URL format'),
-  phone: z.string().trim().max(50, 'Phone must be less than 50 characters').optional().or(z.literal('')),
-  email: z.string().trim().optional().or(z.literal('')).refine((val) => {
+  phone: z.string().trim().max(50, 'Phone must be less than 50 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  email: z.string().trim().nullable().optional().or(z.literal('')).transform(val => val || undefined).refine((val) => {
     if (!val || val === '') return true;
     return z.string().email().safeParse(val).success;
   }, 'Invalid email format'),
@@ -64,19 +64,21 @@ export const parkValidationSchema = z.object({
     .nullable()
     .or(z.literal(''))
     .transform(val => val || undefined),
-  banner_image_id: z.string().optional().or(z.literal('')).transform(val => val || undefined),
-  banner_image_url: z.string().optional().or(z.literal('')).transform(val => val || undefined),
-  card_image_id: z.string().optional().or(z.literal('')).transform(val => val || undefined),
-  card_image_url: z.string().optional().or(z.literal('')).transform(val => val || undefined),
+  banner_image_id: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  banner_image_url: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  card_image_id: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  card_image_url: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
   images: imageAssignmentSchema,
-  source_url: z.string().trim().optional().or(z.literal('')).refine((val) => {
+  source_url: z.string().trim().nullable().optional().or(z.literal('')).transform(val => val || undefined).refine((val) => {
     if (!val || val === '') return true;
     return z.string().url().safeParse(val).success;
   }, 'Invalid URL format. Must be a valid URL starting with http:// or https://'),
   submission_notes: z.string().trim()
     .max(1000, 'Submission notes must be less than 1000 characters')
+    .nullable()
     .optional()
-    .or(z.literal('')),
+    .or(z.literal(''))
+    .transform(val => val || undefined),
 }).refine((data) => {
   if (data.closing_date && data.opening_date) {
     return new Date(data.closing_date) >= new Date(data.opening_date);
@@ -94,9 +96,9 @@ export const parkValidationSchema = z.object({
 export const rideValidationSchema = z.object({
   name: z.string().trim().min(1, 'Ride name is required').max(200, 'Name must be less than 200 characters'),
   slug: z.string().trim().min(1, 'Slug is required').regex(/^[a-z0-9-]+$/, 'Slug must contain only lowercase letters, numbers, and hyphens'),
-  description: z.string().trim().max(2000, 'Description must be less than 2000 characters').optional().or(z.literal('')),
+  description: z.string().trim().max(2000, 'Description must be less than 2000 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
   category: z.string().min(1, 'Category is required'),
-  ride_sub_type: z.string().trim().max(100, 'Sub type must be less than 100 characters').optional().or(z.literal('')),
+  ride_sub_type: z.string().trim().max(100, 'Sub type must be less than 100 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
   status: z.enum(['operating', 'closed_permanently', 'closed_temporarily', 'under_construction', 'relocated', 'stored', 'demolished']),
   park_id: z.string().uuid().optional().nullable(),
   designer_id: z.string()
@@ -106,10 +108,10 @@ export const rideValidationSchema = z.object({
     )
     .optional()
     .nullable(),
-  opening_date: z.string().optional().or(z.literal('')),
-  opening_date_precision: z.enum(['day', 'month', 'year']).optional(),
-  closing_date: z.string().optional().or(z.literal('')),
-  closing_date_precision: z.enum(['day', 'month', 'year']).optional(),
+  opening_date: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  opening_date_precision: z.enum(['day', 'month', 'year']).nullable().optional(),
+  closing_date: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  closing_date_precision: z.enum(['day', 'month', 'year']).nullable().optional(),
   height_requirement: z.preprocess(
     (val) => val === '' || val === null || val === undefined ? undefined : Number(val),
     z.number().int().min(0, 'Height requirement must be positive').max(300, 'Height requirement must be less than 300cm').optional()
@@ -164,9 +166,9 @@ export const rideValidationSchema = z.object({
     )
     .optional()
     .nullable(),
-  coaster_type: z.string().optional(),
-  seating_type: z.string().optional(),
-  intensity_level: z.string().optional(),
+  coaster_type: z.string().nullable().optional(),
+  seating_type: z.string().nullable().optional(),
+  intensity_level: z.string().nullable().optional(),
   track_material: z.array(z.string()).optional().nullable(),
   support_material: z.array(z.string()).optional().nullable(),
   propulsion_method: z.array(z.string()).optional().nullable(),
@@ -179,15 +181,15 @@ export const rideValidationSchema = z.object({
     (val) => val === '' || val === null || val === undefined ? undefined : Number(val),
     z.number().min(0, 'Splash height must be positive').max(100, 'Splash height must be less than 100 meters').optional()
   ),
-  wetness_level: z.enum(['dry', 'light', 'moderate', 'soaked']).optional(),
-  flume_type: z.string().trim().max(100, 'Flume type must be less than 100 characters').optional().or(z.literal('')),
+  wetness_level: z.enum(['dry', 'light', 'moderate', 'soaked']).nullable().optional(),
+  flume_type: z.string().trim().max(100, 'Flume type must be less than 100 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
   boat_capacity: z.preprocess(
     (val) => val === '' || val === null || val === undefined ? undefined : Number(val),
     z.number().int().min(1, 'Boat capacity must be positive').max(100, 'Boat capacity must be less than 100').optional()
   ),
   // Dark ride specific fields
-  theme_name: z.string().trim().max(200, 'Theme name must be less than 200 characters').optional().or(z.literal('')),
-  story_description: z.string().trim().max(2000, 'Story description must be less than 2000 characters').optional().or(z.literal('')),
+  theme_name: z.string().trim().max(200, 'Theme name must be less than 200 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  story_description: z.string().trim().max(2000, 'Story description must be less than 2000 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
   show_duration_seconds: z.preprocess(
     (val) => val === '' || val === null || val === undefined ? undefined : Number(val),
     z.number().int().min(0, 'Show duration must be positive').max(7200, 'Show duration must be less than 2 hours').optional()
@@ -196,15 +198,15 @@ export const rideValidationSchema = z.object({
     (val) => val === '' || val === null || val === undefined ? undefined : Number(val),
     z.number().int().min(0, 'Animatronics count must be positive').max(1000, 'Animatronics count must be less than 1000').optional()
   ),
-  projection_type: z.string().trim().max(100, 'Projection type must be less than 100 characters').optional().or(z.literal('')),
-  ride_system: z.string().trim().max(100, 'Ride system must be less than 100 characters').optional().or(z.literal('')),
+  projection_type: z.string().trim().max(100, 'Projection type must be less than 100 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  ride_system: z.string().trim().max(100, 'Ride system must be less than 100 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
   scenes_count: z.preprocess(
     (val) => val === '' || val === null || val === undefined ? undefined : Number(val),
     z.number().int().min(0, 'Scenes count must be positive').max(100, 'Scenes count must be less than 100').optional()
   ),
   // Flat ride specific fields
-  rotation_type: z.enum(['horizontal', 'vertical', 'multi_axis', 'pendulum', 'none']).optional(),
-  motion_pattern: z.string().trim().max(200, 'Motion pattern must be less than 200 characters').optional().or(z.literal('')),
+  rotation_type: z.enum(['horizontal', 'vertical', 'multi_axis', 'pendulum', 'none']).nullable().optional(),
+  motion_pattern: z.string().trim().max(200, 'Motion pattern must be less than 200 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
   platform_count: z.preprocess(
     (val) => val === '' || val === null || val === undefined ? undefined : Number(val),
     z.number().int().min(1, 'Platform count must be positive').max(100, 'Platform count must be less than 100').optional()
@@ -234,10 +236,10 @@ export const rideValidationSchema = z.object({
     (val) => val === '' || val === null || val === undefined ? undefined : Number(val),
     z.number().int().min(0, 'Max age must be positive').max(18, 'Max age must be less than 18').optional()
   ),
-  educational_theme: z.string().trim().max(200, 'Educational theme must be less than 200 characters').optional().or(z.literal('')),
-  character_theme: z.string().trim().max(200, 'Character theme must be less than 200 characters').optional().or(z.literal('')),
+  educational_theme: z.string().trim().max(200, 'Educational theme must be less than 200 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  character_theme: z.string().trim().max(200, 'Character theme must be less than 200 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
   // Transportation ride specific fields
-  transport_type: z.enum(['train', 'monorail', 'skylift', 'ferry', 'peoplemover', 'cable_car']).optional(),
+  transport_type: z.enum(['train', 'monorail', 'skylift', 'ferry', 'peoplemover', 'cable_car']).nullable().optional(),
   route_length_meters: z.preprocess(
     (val) => val === '' || val === null || val === undefined ? undefined : Number(val),
     z.number().min(0, 'Route length must be positive').max(50000, 'Route length must be less than 50km').optional()
@@ -258,19 +260,21 @@ export const rideValidationSchema = z.object({
     (val) => val === '' || val === null || val === undefined ? undefined : Number(val),
     z.number().int().min(0, 'Round trip duration must be positive').max(7200, 'Round trip duration must be less than 2 hours').optional()
   ),
-  banner_image_id: z.string().optional().or(z.literal('')).transform(val => val || undefined),
-  banner_image_url: z.string().optional().or(z.literal('')).transform(val => val || undefined),
-  card_image_id: z.string().optional().or(z.literal('')).transform(val => val || undefined),
-  card_image_url: z.string().optional().or(z.literal('')).transform(val => val || undefined),
+  banner_image_id: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  banner_image_url: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  card_image_id: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  card_image_url: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
   images: imageAssignmentSchema,
-  source_url: z.string().trim().optional().or(z.literal('')).refine((val) => {
+  source_url: z.string().trim().nullable().optional().or(z.literal('')).transform(val => val || undefined).refine((val) => {
     if (!val || val === '') return true;
     return z.string().url().safeParse(val).success;
   }, 'Invalid URL format. Must be a valid URL starting with http:// or https://'),
   submission_notes: z.string().trim()
     .max(1000, 'Submission notes must be less than 1000 characters')
+    .nullable()
     .optional()
-    .or(z.literal('')),
+    .or(z.literal(''))
+    .transform(val => val || undefined),
 });
 
 // ============================================
@@ -281,32 +285,34 @@ export const companyValidationSchema = z.object({
   name: z.string().trim().min(1, 'Company name is required').max(200, 'Name must be less than 200 characters'),
   slug: z.string().trim().min(1, 'Slug is required').regex(/^[a-z0-9-]+$/, 'Slug must contain only lowercase letters, numbers, and hyphens'),
   company_type: z.enum(['manufacturer', 'designer', 'operator', 'property_owner']),
-  description: z.string().trim().max(2000, 'Description must be less than 2000 characters').optional().or(z.literal('')),
+  description: z.string().trim().max(2000, 'Description must be less than 2000 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
   person_type: z.enum(['company', 'individual', 'firm', 'organization']),
-  founded_date: z.string().optional().or(z.literal('')),
-  founded_date_precision: z.enum(['day', 'month', 'year']).optional(),
+  founded_date: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  founded_date_precision: z.enum(['day', 'month', 'year']).nullable().optional(),
   founded_year: z.preprocess(
     (val) => val === '' || val === null || val === undefined ? undefined : Number(val),
     z.number().int().min(1800, 'Founded year must be after 1800').max(currentYear, `Founded year cannot be after ${currentYear}`).optional()
   ),
-  headquarters_location: z.string().trim().max(200, 'Location must be less than 200 characters').optional().or(z.literal('')),
-  website_url: z.string().trim().optional().or(z.literal('')).refine((val) => {
+  headquarters_location: z.string().trim().max(200, 'Location must be less than 200 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  website_url: z.string().trim().nullable().optional().or(z.literal('')).transform(val => val || undefined).refine((val) => {
     if (!val || val === '') return true;
     return z.string().url().safeParse(val).success;
   }, 'Invalid URL format'),
-  banner_image_id: z.string().optional().or(z.literal('')).transform(val => val || undefined),
-  banner_image_url: z.string().optional().or(z.literal('')).transform(val => val || undefined),
-  card_image_id: z.string().optional().or(z.literal('')).transform(val => val || undefined),
-  card_image_url: z.string().optional().or(z.literal('')).transform(val => val || undefined),
+  banner_image_id: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  banner_image_url: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  card_image_id: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
+  card_image_url: z.string().nullable().optional().or(z.literal('')).transform(val => val || undefined),
   images: imageAssignmentSchema,
-  source_url: z.string().trim().optional().or(z.literal('')).refine((val) => {
+  source_url: z.string().trim().nullable().optional().or(z.literal('')).transform(val => val || undefined).refine((val) => {
     if (!val || val === '') return true;
     return z.string().url().safeParse(val).success;
   }, 'Invalid URL format. Must be a valid URL starting with http:// or https://'),
   submission_notes: z.string().trim()
     .max(1000, 'Submission notes must be less than 1000 characters')
+    .nullable()
     .optional()
-    .or(z.literal('')),
+    .or(z.literal(''))
+    .transform(val => val || undefined),
 });
 
 // ============================================
@@ -318,21 +324,23 @@ export const rideModelValidationSchema = z.object({
   slug: z.string().trim().min(1, 'Slug is required').regex(/^[a-z0-9-]+$/, 'Slug must contain only lowercase letters, numbers, and hyphens'),
   category: z.string().min(1, 'Category is required'),
   ride_type: z.string().trim().min(1, 'Ride type is required').max(100, 'Ride type must be less than 100 characters'),
-  description: z.string().trim().max(2000, 'Description must be less than 2000 characters').optional().or(z.literal('')),
+  description: z.string().trim().max(2000, 'Description must be less than 2000 characters').nullable().optional().or(z.literal('')).transform(val => val || undefined),
   manufacturer_id: z.string()
     .refine(
       val => !val || val === '' || val.startsWith('temp-') || /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i.test(val),
       'Must be a valid UUID or temporary placeholder'
     )
     .optional(),
-  source_url: z.string().trim().optional().or(z.literal('')).refine((val) => {
+  source_url: z.string().trim().nullable().optional().or(z.literal('')).transform(val => val || undefined).refine((val) => {
     if (!val || val === '') return true;
     return z.string().url().safeParse(val).success;
   }, 'Invalid URL format. Must be a valid URL starting with http:// or https://'),
   submission_notes: z.string().trim()
     .max(1000, 'Submission notes must be less than 1000 characters')
+    .nullable()
     .optional()
-    .or(z.literal('')),
+    .or(z.literal(''))
+    .transform(val => val || undefined),
 });
 
 // ============================================