diff --git a/integration-tests-definitions/todo-lists.yaml b/integration-tests-definitions/todo-lists.yaml
index d58aa57a5..2ef159672 100644
--- a/integration-tests-definitions/todo-lists.yaml
+++ b/integration-tests-definitions/todo-lists.yaml
@@ -171,6 +171,9 @@ components:
         created:
           type: string
           format: date-time
+          x-alpha-transform:
+            fn: (it) => new Date(it)
+            type: Date
         updated:
           type: string
           format: date-time
diff --git a/integration-tests/typescript-angular/src/generated/todo-lists.yaml/models.ts b/integration-tests/typescript-angular/src/generated/todo-lists.yaml/models.ts
index 28740557b..6633a8fe6 100644
--- a/integration-tests/typescript-angular/src/generated/todo-lists.yaml/models.ts
+++ b/integration-tests/typescript-angular/src/generated/todo-lists.yaml/models.ts
@@ -12,7 +12,7 @@ export type t_CreateUpdateTodoList = {
 }
 
 export type t_TodoList = {
-  created: string
+  created: Date
   id: string
   incompleteItemCount: number
   name: string
diff --git a/integration-tests/typescript-axios/src/generated/todo-lists.yaml/models.ts b/integration-tests/typescript-axios/src/generated/todo-lists.yaml/models.ts
index 28740557b..6633a8fe6 100644
--- a/integration-tests/typescript-axios/src/generated/todo-lists.yaml/models.ts
+++ b/integration-tests/typescript-axios/src/generated/todo-lists.yaml/models.ts
@@ -12,7 +12,7 @@ export type t_CreateUpdateTodoList = {
 }
 
 export type t_TodoList = {
-  created: string
+  created: Date
   id: string
   incompleteItemCount: number
   name: string
diff --git a/integration-tests/typescript-fetch/src/generated/todo-lists.yaml/models.ts b/integration-tests/typescript-fetch/src/generated/todo-lists.yaml/models.ts
index 28740557b..6633a8fe6 100644
--- a/integration-tests/typescript-fetch/src/generated/todo-lists.yaml/models.ts
+++ b/integration-tests/typescript-fetch/src/generated/todo-lists.yaml/models.ts
@@ -12,7 +12,7 @@ export type t_CreateUpdateTodoList = {
 }
 
 export type t_TodoList = {
-  created: string
+  created: Date
   id: string
   incompleteItemCount: number
   name: string
diff --git a/integration-tests/typescript-koa/src/generated/api.github.com.yaml/generated.ts b/integration-tests/typescript-koa/src/generated/api.github.com.yaml/generated.ts
index ef65cc54c..576d96c54 100644
--- a/integration-tests/typescript-koa/src/generated/api.github.com.yaml/generated.ts
+++ b/integration-tests/typescript-koa/src/generated/api.github.com.yaml/generated.ts
@@ -34177,7 +34177,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const migrationsListForOrgQuerySchema = z.object({
     per_page: z.coerce.number().optional(),
     page: z.coerce.number().optional(),
-    exclude: z.array(z.enum(["repositories"])).optional(),
+    exclude: z
+      .union([z.array(z.enum(["repositories"])), z.enum(["repositories"])])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const migrationsListForOrgResponseValidator = responseValidationFactory(
@@ -34304,7 +34307,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const migrationsGetStatusForOrgQuerySchema = z.object({
-    exclude: z.array(z.enum(["repositories"])).optional(),
+    exclude: z
+      .union([z.array(z.enum(["repositories"])), z.enum(["repositories"])])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const migrationsGetStatusForOrgResponseValidator = responseValidationFactory(
@@ -36199,7 +36205,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
     page: z.coerce.number().optional(),
     sort: z.enum(["created_at"]).optional(),
     direction: z.enum(["asc", "desc"]).optional(),
-    owner: z.array(z.string()).max(10).optional(),
+    owner: z
+      .union([z.array(z.string()).max(10), z.string()])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     repository: z.string().optional(),
     permission: z.string().optional(),
     last_used_before: z.string().datetime({ offset: true }).optional(),
@@ -36508,7 +36517,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
     page: z.coerce.number().optional(),
     sort: z.enum(["created_at"]).optional(),
     direction: z.enum(["asc", "desc"]).optional(),
-    owner: z.array(z.string()).max(10).optional(),
+    owner: z
+      .union([z.array(z.string()).max(10), z.string()])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     repository: z.string().optional(),
     permission: z.string().optional(),
     last_used_before: z.string().datetime({ offset: true }).optional(),
@@ -77418,7 +77430,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const migrationsGetStatusForAuthenticatedUserQuerySchema = z.object({
-    exclude: z.array(z.string()).optional(),
+    exclude: z
+      .union([z.array(z.string()), z.string()])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const migrationsGetStatusForAuthenticatedUserResponseValidator =
diff --git a/integration-tests/typescript-koa/src/generated/azure-core-data-plane-service.tsp/generated.ts b/integration-tests/typescript-koa/src/generated/azure-core-data-plane-service.tsp/generated.ts
index cfe4d3124..11a4923b4 100644
--- a/integration-tests/typescript-koa/src/generated/azure-core-data-plane-service.tsp/generated.ts
+++ b/integration-tests/typescript-koa/src/generated/azure-core-data-plane-service.tsp/generated.ts
@@ -1040,7 +1040,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
     top: z.coerce.number().optional(),
     skip: z.coerce.number().optional(),
     maxpagesize: z.coerce.number().optional(),
-    select: z.array(z.string()).optional(),
+    select: z
+      .union([z.array(z.string()), z.string()])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const widgetsListWidgetsResponseValidator = responseValidationFactory(
diff --git a/integration-tests/typescript-koa/src/generated/petstore-expanded.yaml/generated.ts b/integration-tests/typescript-koa/src/generated/petstore-expanded.yaml/generated.ts
index e3e0d0e7d..56e9014fc 100644
--- a/integration-tests/typescript-koa/src/generated/petstore-expanded.yaml/generated.ts
+++ b/integration-tests/typescript-koa/src/generated/petstore-expanded.yaml/generated.ts
@@ -102,7 +102,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const router = new KoaRouter()
 
   const findPetsQuerySchema = z.object({
-    tags: z.array(z.string()).optional(),
+    tags: z
+      .union([z.array(z.string()), z.string()])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
   })
 
diff --git a/integration-tests/typescript-koa/src/generated/stripe.yaml/generated.ts b/integration-tests/typescript-koa/src/generated/stripe.yaml/generated.ts
index 73d3b5f00..c170deb7c 100644
--- a/integration-tests/typescript-koa/src/generated/stripe.yaml/generated.ts
+++ b/integration-tests/typescript-koa/src/generated/stripe.yaml/generated.ts
@@ -13515,7 +13515,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const router = new KoaRouter()
 
   const getAccountQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getAccountBodySchema = z.object({}).optional()
@@ -13785,7 +13788,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().optional(),
   })
@@ -14508,7 +14514,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getAccountsAccountQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getAccountsAccountBodySchema = z.object({}).optional()
@@ -15289,7 +15298,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getAccountsAccountBankAccountsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getAccountsAccountBankAccountsIdBodySchema = z.object({}).optional()
@@ -15434,7 +15446,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getAccountsAccountCapabilitiesQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getAccountsAccountCapabilitiesBodySchema = z.object({}).optional()
@@ -15515,7 +15530,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getAccountsAccountCapabilitiesCapabilityQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getAccountsAccountCapabilitiesCapabilityBodySchema = z
@@ -15646,7 +15664,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getAccountsAccountExternalAccountsQuerySchema = z.object({
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     object: z.enum(["bank_account", "card"]).optional(),
     starting_after: z.string().optional(),
@@ -15883,7 +15904,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getAccountsAccountExternalAccountsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getAccountsAccountExternalAccountsIdBodySchema = z.object({}).optional()
@@ -16088,7 +16112,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getAccountsAccountPeopleQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     relationship: z
       .object({
@@ -16436,7 +16463,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getAccountsAccountPeoplePersonQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getAccountsAccountPeoplePersonBodySchema = z.object({}).optional()
@@ -16697,7 +16727,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getAccountsAccountPersonsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     relationship: z
       .object({
@@ -17045,7 +17078,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getAccountsAccountPersonsPersonQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getAccountsAccountPersonsPersonBodySchema = z.object({}).optional()
@@ -17362,7 +17398,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getApplePayDomainsQuerySchema = z.object({
     domain_name: z.string().max(5000).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -17544,7 +17583,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getApplePayDomainsDomainQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getApplePayDomainsDomainBodySchema = z.object({}).optional()
@@ -17617,7 +17659,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -17695,7 +17740,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getApplicationFeesFeeRefundsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getApplicationFeesFeeRefundsIdBodySchema = z.object({}).optional()
@@ -17815,7 +17863,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getApplicationFeesIdParamSchema = z.object({ id: z.string().max(5000) })
 
   const getApplicationFeesIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getApplicationFeesIdBodySchema = z.object({}).optional()
@@ -17940,7 +17991,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getApplicationFeesIdRefundsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -18079,7 +18133,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getAppsSecretsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     scope: z.object({
       type: z.enum(["account", "user"]),
@@ -18260,7 +18317,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   )
 
   const getAppsSecretsFindQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     name: z.string().max(5000),
     scope: z.object({
       type: z.enum(["account", "user"]),
@@ -18321,7 +18381,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   )
 
   const getBalanceQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getBalanceBodySchema = z.object({}).optional()
@@ -18386,7 +18449,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     currency: z.string().optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     payout: z.string().max(5000).optional(),
     source: z.string().max(5000).optional(),
@@ -18463,7 +18529,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getBalanceHistoryIdParamSchema = z.object({ id: z.string().max(5000) })
 
   const getBalanceHistoryIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getBalanceHistoryIdBodySchema = z.object({}).optional()
@@ -18536,7 +18605,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     currency: z.string().optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     payout: z.string().max(5000).optional(),
     source: z.string().max(5000).optional(),
@@ -18619,7 +18691,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getBalanceTransactionsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getBalanceTransactionsIdBodySchema = z.object({}).optional()
@@ -18788,7 +18863,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getBillingMetersQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     status: z.enum(["active", "inactive"]).optional(),
@@ -18919,7 +18997,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getBillingMetersIdParamSchema = z.object({ id: z.string().max(5000) })
 
   const getBillingMetersIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getBillingMetersIdBodySchema = z.object({}).optional()
@@ -19101,7 +19182,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
     customer: z.string().max(5000),
     end_time: z.coerce.number(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     start_time: z.coerce.number(),
     starting_after: z.string().max(5000).optional(),
@@ -19242,7 +19326,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getBillingPortalConfigurationsQuerySchema = z.object({
     active: PermissiveBoolean.optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     is_default: PermissiveBoolean.optional(),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
@@ -19459,7 +19546,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getBillingPortalConfigurationsConfigurationQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getBillingPortalConfigurationsConfigurationBodySchema = z
@@ -19859,7 +19949,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     customer: z.string().max(5000).optional(),
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     payment_intent: z.string().max(5000).optional(),
     starting_after: z.string().optional(),
@@ -20046,7 +20139,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getChargesSearchQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     page: z.string().max(5000).optional(),
     query: z.string().max(5000),
@@ -20122,7 +20218,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getChargesChargeParamSchema = z.object({ charge: z.string().max(5000) })
 
   const getChargesChargeQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getChargesChargeBodySchema = z.object({}).optional()
@@ -20332,7 +20431,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getChargesChargeDisputeQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getChargesChargeDisputeBodySchema = z.object({}).optional()
@@ -20613,7 +20715,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getChargesChargeRefundsQuerySchema = z.object({
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().optional(),
   })
@@ -20767,7 +20872,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getChargesChargeRefundsRefundQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getChargesChargeRefundsRefundBodySchema = z.object({}).optional()
@@ -20899,7 +21007,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
     customer: z.string().max(5000).optional(),
     customer_details: z.object({ email: z.string() }).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     payment_intent: z.string().max(5000).optional(),
     payment_link: z.string().max(5000).optional(),
@@ -21993,7 +22104,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getCheckoutSessionsSessionQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCheckoutSessionsSessionBodySchema = z.object({}).optional()
@@ -22117,7 +22231,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getCheckoutSessionsSessionLineItemsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -22199,7 +22316,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getClimateOrdersQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -22324,7 +22444,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getClimateOrdersOrderQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getClimateOrdersOrderBodySchema = z.object({}).optional()
@@ -22510,7 +22633,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getClimateProductsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -22587,7 +22713,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getClimateProductsProductQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getClimateProductsProductBodySchema = z.object({}).optional()
@@ -22648,7 +22777,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getClimateSuppliersQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -22725,7 +22857,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getClimateSuppliersSupplierQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getClimateSuppliersSupplierBodySchema = z.object({}).optional()
@@ -22787,7 +22922,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getConfirmationTokensConfirmationTokenQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getConfirmationTokensConfirmationTokenBodySchema = z
@@ -22851,7 +22989,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getCountrySpecsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -22924,7 +23065,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getCountrySpecsCountryQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCountrySpecsCountryBodySchema = z.object({}).optional()
@@ -22996,7 +23140,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -23187,7 +23334,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getCouponsCouponParamSchema = z.object({ coupon: z.string().max(5000) })
 
   const getCouponsCouponQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCouponsCouponBodySchema = z.object({}).optional()
@@ -23317,7 +23467,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     customer: z.string().max(5000).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     invoice: z.string().max(5000).optional(),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
@@ -23484,10 +23637,39 @@ export function createRouter(implementation: Implementation): KoaRouter {
     amount: z.coerce.number().optional(),
     credit_amount: z.coerce.number().optional(),
     effective_at: z.coerce.number().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     invoice: z.string().max(5000),
     lines: z
-      .array(
+      .union([
+        z.array(
+          z.object({
+            amount: z.coerce.number().optional(),
+            description: z.string().max(5000).optional(),
+            invoice_line_item: z.string().max(5000).optional(),
+            quantity: z.coerce.number().optional(),
+            tax_amounts: z
+              .union([
+                z.array(
+                  z.object({
+                    amount: z.coerce.number(),
+                    tax_rate: z.string().max(5000),
+                    taxable_amount: z.coerce.number(),
+                  }),
+                ),
+                z.enum([""]),
+              ])
+              .optional(),
+            tax_rates: z
+              .union([z.array(z.string().max(5000)), z.enum([""])])
+              .optional(),
+            type: z.enum(["custom_line_item", "invoice_line_item"]),
+            unit_amount: z.coerce.number().optional(),
+            unit_amount_decimal: z.string().optional(),
+          }),
+        ),
         z.object({
           amount: z.coerce.number().optional(),
           description: z.string().max(5000).optional(),
@@ -23512,8 +23694,9 @@ export function createRouter(implementation: Implementation): KoaRouter {
           unit_amount: z.coerce.number().optional(),
           unit_amount_decimal: z.string().optional(),
         }),
-      )
-      .optional(),
+      ])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     memo: z.string().max(5000).optional(),
     metadata: z.record(z.string()).optional(),
     out_of_band_amount: z.coerce.number().optional(),
@@ -23589,11 +23772,40 @@ export function createRouter(implementation: Implementation): KoaRouter {
     credit_amount: z.coerce.number().optional(),
     effective_at: z.coerce.number().optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     invoice: z.string().max(5000),
     limit: z.coerce.number().optional(),
     lines: z
-      .array(
+      .union([
+        z.array(
+          z.object({
+            amount: z.coerce.number().optional(),
+            description: z.string().max(5000).optional(),
+            invoice_line_item: z.string().max(5000).optional(),
+            quantity: z.coerce.number().optional(),
+            tax_amounts: z
+              .union([
+                z.array(
+                  z.object({
+                    amount: z.coerce.number(),
+                    tax_rate: z.string().max(5000),
+                    taxable_amount: z.coerce.number(),
+                  }),
+                ),
+                z.enum([""]),
+              ])
+              .optional(),
+            tax_rates: z
+              .union([z.array(z.string().max(5000)), z.enum([""])])
+              .optional(),
+            type: z.enum(["custom_line_item", "invoice_line_item"]),
+            unit_amount: z.coerce.number().optional(),
+            unit_amount_decimal: z.string().optional(),
+          }),
+        ),
         z.object({
           amount: z.coerce.number().optional(),
           description: z.string().max(5000).optional(),
@@ -23618,8 +23830,9 @@ export function createRouter(implementation: Implementation): KoaRouter {
           unit_amount: z.coerce.number().optional(),
           unit_amount_decimal: z.string().optional(),
         }),
-      )
-      .optional(),
+      ])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     memo: z.string().max(5000).optional(),
     metadata: z.record(z.string()).optional(),
     out_of_band_amount: z.coerce.number().optional(),
@@ -23712,7 +23925,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getCreditNotesCreditNoteLinesQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -23792,7 +24008,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getCreditNotesIdParamSchema = z.object({ id: z.string().max(5000) })
 
   const getCreditNotesIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCreditNotesIdBodySchema = z.object({}).optional()
@@ -24034,7 +24253,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     email: z.string().max(512).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     test_clock: z.string().max(5000).optional(),
@@ -24322,7 +24544,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getCustomersSearchQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     page: z.string().max(5000).optional(),
     query: z.string().max(5000),
@@ -24460,7 +24685,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getCustomersCustomerQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCustomersCustomerBodySchema = z.object({}).optional()
@@ -24710,7 +24938,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getCustomersCustomerBalanceTransactionsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -24862,7 +25093,12 @@ export function createRouter(implementation: Implementation): KoaRouter {
     z.object({ customer: z.string().max(5000), transaction: z.string() })
 
   const getCustomersCustomerBalanceTransactionsTransactionQuerySchema =
-    z.object({ expand: z.array(z.string().max(5000)).optional() })
+    z.object({
+      expand: z
+        .union([z.array(z.string().max(5000)), z.string().max(5000)])
+        .optional()
+        .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
+    })
 
   const getCustomersCustomerBalanceTransactionsTransactionBodySchema = z
     .object({})
@@ -25010,7 +25246,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getCustomersCustomerBankAccountsQuerySchema = z.object({
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().optional(),
   })
@@ -25261,7 +25500,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getCustomersCustomerBankAccountsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCustomersCustomerBankAccountsIdBodySchema = z.object({}).optional()
@@ -25493,7 +25735,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getCustomersCustomerCardsQuerySchema = z.object({
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().optional(),
   })
@@ -25739,7 +25984,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getCustomersCustomerCardsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCustomersCustomerCardsIdBodySchema = z.object({}).optional()
@@ -25901,7 +26149,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getCustomersCustomerCashBalanceQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCustomersCustomerCashBalanceBodySchema = z.object({}).optional()
@@ -26029,7 +26280,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getCustomersCustomerCashBalanceTransactionsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -26115,7 +26369,12 @@ export function createRouter(implementation: Implementation): KoaRouter {
     z.object({ customer: z.string().max(5000), transaction: z.string() })
 
   const getCustomersCustomerCashBalanceTransactionsTransactionQuerySchema =
-    z.object({ expand: z.array(z.string().max(5000)).optional() })
+    z.object({
+      expand: z
+        .union([z.array(z.string().max(5000)), z.string().max(5000)])
+        .optional()
+        .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
+    })
 
   const getCustomersCustomerCashBalanceTransactionsTransactionBodySchema = z
     .object({})
@@ -26245,7 +26504,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getCustomersCustomerDiscountQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCustomersCustomerDiscountBodySchema = z.object({}).optional()
@@ -26383,7 +26645,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getCustomersCustomerPaymentMethodsQuerySchema = z.object({
     allow_redisplay: z.enum(["always", "limited", "unspecified"]).optional(),
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().optional(),
     type: z
@@ -26510,7 +26775,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getCustomersCustomerPaymentMethodsPaymentMethodQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCustomersCustomerPaymentMethodsPaymentMethodBodySchema = z
@@ -26579,7 +26847,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getCustomersCustomerSourcesQuerySchema = z.object({
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     object: z.string().max(5000).optional(),
     starting_after: z.string().optional(),
@@ -26831,7 +27102,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getCustomersCustomerSourcesIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCustomersCustomerSourcesIdBodySchema = z.object({}).optional()
@@ -27057,7 +27331,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getCustomersCustomerSubscriptionsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -27608,7 +27885,12 @@ export function createRouter(implementation: Implementation): KoaRouter {
     })
 
   const getCustomersCustomerSubscriptionsSubscriptionExposedIdQuerySchema =
-    z.object({ expand: z.array(z.string().max(5000)).optional() })
+    z.object({
+      expand: z
+        .union([z.array(z.string().max(5000)), z.string().max(5000)])
+        .optional()
+        .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
+    })
 
   const getCustomersCustomerSubscriptionsSubscriptionExposedIdBodySchema = z
     .object({})
@@ -28178,7 +28460,12 @@ export function createRouter(implementation: Implementation): KoaRouter {
     })
 
   const getCustomersCustomerSubscriptionsSubscriptionExposedIdDiscountQuerySchema =
-    z.object({ expand: z.array(z.string().max(5000)).optional() })
+    z.object({
+      expand: z
+        .union([z.array(z.string().max(5000)), z.string().max(5000)])
+        .optional()
+        .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
+    })
 
   const getCustomersCustomerSubscriptionsSubscriptionExposedIdDiscountBodySchema =
     z.object({}).optional()
@@ -28249,7 +28536,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getCustomersCustomerTaxIdsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -28517,7 +28807,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getCustomersCustomerTaxIdsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getCustomersCustomerTaxIdsIdBodySchema = z.object({}).optional()
@@ -28588,7 +28881,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     payment_intent: z.string().max(5000).optional(),
     starting_after: z.string().max(5000).optional(),
@@ -28662,7 +28958,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getDisputesDisputeQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getDisputesDisputeBodySchema = z.object({}).optional()
@@ -28875,7 +29174,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getEntitlementsActiveEntitlementsQuerySchema = z.object({
     customer: z.string().max(5000),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -28956,7 +29258,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getEntitlementsActiveEntitlementsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getEntitlementsActiveEntitlementsIdBodySchema = z.object({}).optional()
@@ -29022,7 +29327,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getEntitlementsFeaturesQuerySchema = z.object({
     archived: PermissiveBoolean.optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     lookup_key: z.string().max(5000).optional(),
     starting_after: z.string().max(5000).optional(),
@@ -29156,7 +29464,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getEntitlementsFeaturesIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getEntitlementsFeaturesIdBodySchema = z.object({}).optional()
@@ -29402,11 +29713,17 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     delivery_success: PermissiveBoolean.optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     type: z.string().max(5000).optional(),
-    types: z.array(z.string().max(5000)).optional(),
+    types: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getEventsBodySchema = z.object({}).optional()
@@ -29475,7 +29792,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getEventsIdParamSchema = z.object({ id: z.string().max(5000) })
 
   const getEventsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getEventsIdBodySchema = z.object({}).optional()
@@ -29532,7 +29852,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getExchangeRatesQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -29605,7 +29928,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getExchangeRatesRateIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getExchangeRatesRateIdBodySchema = z.object({}).optional()
@@ -29677,7 +30003,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     expired: PermissiveBoolean.optional(),
     file: z.string().max(5000).optional(),
     limit: z.coerce.number().optional(),
@@ -29799,7 +30128,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getFileLinksLinkParamSchema = z.object({ link: z.string() })
 
   const getFileLinksLinkQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getFileLinksLinkBodySchema = z.object({}).optional()
@@ -29929,7 +30261,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     purpose: z
       .enum([
@@ -30085,7 +30420,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getFilesFileParamSchema = z.object({ file: z.string().max(5000) })
 
   const getFilesFileQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getFilesFileBodySchema = z.object({}).optional()
@@ -30148,7 +30486,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       })
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     session: z.string().max(5000).optional(),
     starting_after: z.string().max(5000).optional(),
@@ -30230,7 +30571,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getFinancialConnectionsAccountsAccountQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getFinancialConnectionsAccountsAccountBodySchema = z
@@ -30368,7 +30712,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getFinancialConnectionsAccountsAccountOwnersQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     ownership: z.string().max(5000),
     starting_after: z.string().max(5000).optional(),
@@ -30719,7 +31066,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getFinancialConnectionsSessionsSessionQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getFinancialConnectionsSessionsSessionBodySchema = z
@@ -30787,7 +31137,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getFinancialConnectionsTransactionsQuerySchema = z.object({
     account: z.string().max(5000),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     transacted_at: z
@@ -30883,7 +31236,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getFinancialConnectionsTransactionsTransactionQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getFinancialConnectionsTransactionsTransactionBodySchema = z
@@ -30961,7 +31317,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       })
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -31106,7 +31465,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getForwardingRequestsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getForwardingRequestsIdBodySchema = z.object({}).optional()
@@ -31179,7 +31541,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     type: z.enum(["document", "id_number"]).optional(),
@@ -31262,7 +31627,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getIdentityVerificationReportsReportQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getIdentityVerificationReportsReportBodySchema = z.object({}).optional()
@@ -31339,7 +31707,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     status: z
@@ -31501,7 +31872,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getIdentityVerificationSessionsSessionQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getIdentityVerificationSessionsSessionBodySchema = z
@@ -31790,7 +32164,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     customer: z.string().max(5000).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     invoice: z.string().max(5000).optional(),
     limit: z.coerce.number().optional(),
     pending: PermissiveBoolean.optional(),
@@ -32006,7 +32383,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getInvoiceitemsInvoiceitemQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getInvoiceitemsInvoiceitemBodySchema = z.object({}).optional()
@@ -32192,7 +32572,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     status: z
@@ -33113,7 +33496,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   )
 
   const getInvoicesSearchQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     page: z.string().max(5000).optional(),
     query: z.string().max(5000),
@@ -33334,9 +33720,59 @@ export function createRouter(implementation: Implementation): KoaRouter {
         z.enum([""]),
       ])
       .optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     invoice_items: z
-      .array(
+      .union([
+        z.array(
+          z.object({
+            amount: z.coerce.number().optional(),
+            currency: z.string().optional(),
+            description: z.string().max(5000).optional(),
+            discountable: PermissiveBoolean.optional(),
+            discounts: z
+              .union([
+                z.array(
+                  z.object({
+                    coupon: z.string().max(5000).optional(),
+                    discount: z.string().max(5000).optional(),
+                    promotion_code: z.string().max(5000).optional(),
+                  }),
+                ),
+                z.enum([""]),
+              ])
+              .optional(),
+            invoiceitem: z.string().max(5000).optional(),
+            metadata: z.union([z.record(z.string()), z.enum([""])]).optional(),
+            period: z
+              .object({ end: z.coerce.number(), start: z.coerce.number() })
+              .optional(),
+            price: z.string().max(5000).optional(),
+            price_data: z
+              .object({
+                currency: z.string(),
+                product: z.string().max(5000),
+                tax_behavior: z
+                  .enum(["exclusive", "inclusive", "unspecified"])
+                  .optional(),
+                unit_amount: z.coerce.number().optional(),
+                unit_amount_decimal: z.string().optional(),
+              })
+              .optional(),
+            quantity: z.coerce.number().optional(),
+            tax_behavior: z
+              .enum(["exclusive", "inclusive", "unspecified"])
+              .optional(),
+            tax_code: z.union([z.string(), z.enum([""])]).optional(),
+            tax_rates: z
+              .union([z.array(z.string().max(5000)), z.enum([""])])
+              .optional(),
+            unit_amount: z.coerce.number().optional(),
+            unit_amount_decimal: z.string().optional(),
+          }),
+        ),
         z.object({
           amount: z.coerce.number().optional(),
           currency: z.string().optional(),
@@ -33382,8 +33818,9 @@ export function createRouter(implementation: Implementation): KoaRouter {
           unit_amount: z.coerce.number().optional(),
           unit_amount_decimal: z.string().optional(),
         }),
-      )
-      .optional(),
+      ])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     issuer: z
       .object({
         account: z.string().optional(),
@@ -33647,7 +34084,50 @@ export function createRouter(implementation: Implementation): KoaRouter {
       })
       .optional(),
     subscription_items: z
-      .array(
+      .union([
+        z.array(
+          z.object({
+            billing_thresholds: z
+              .union([z.object({ usage_gte: z.coerce.number() }), z.enum([""])])
+              .optional(),
+            clear_usage: PermissiveBoolean.optional(),
+            deleted: PermissiveBoolean.optional(),
+            discounts: z
+              .union([
+                z.array(
+                  z.object({
+                    coupon: z.string().max(5000).optional(),
+                    discount: z.string().max(5000).optional(),
+                    promotion_code: z.string().max(5000).optional(),
+                  }),
+                ),
+                z.enum([""]),
+              ])
+              .optional(),
+            id: z.string().max(5000).optional(),
+            metadata: z.union([z.record(z.string()), z.enum([""])]).optional(),
+            price: z.string().max(5000).optional(),
+            price_data: z
+              .object({
+                currency: z.string(),
+                product: z.string().max(5000),
+                recurring: z.object({
+                  interval: z.enum(["day", "month", "week", "year"]),
+                  interval_count: z.coerce.number().optional(),
+                }),
+                tax_behavior: z
+                  .enum(["exclusive", "inclusive", "unspecified"])
+                  .optional(),
+                unit_amount: z.coerce.number().optional(),
+                unit_amount_decimal: z.string().optional(),
+              })
+              .optional(),
+            quantity: z.coerce.number().optional(),
+            tax_rates: z
+              .union([z.array(z.string().max(5000)), z.enum([""])])
+              .optional(),
+          }),
+        ),
         z.object({
           billing_thresholds: z
             .union([z.object({ usage_gte: z.coerce.number() }), z.enum([""])])
@@ -33689,8 +34169,9 @@ export function createRouter(implementation: Implementation): KoaRouter {
             .union([z.array(z.string().max(5000)), z.enum([""])])
             .optional(),
         }),
-      )
-      .optional(),
+      ])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     subscription_proration_behavior: z
       .enum(["always_invoice", "create_prorations", "none"])
       .optional(),
@@ -33903,9 +34384,59 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     invoice_items: z
-      .array(
+      .union([
+        z.array(
+          z.object({
+            amount: z.coerce.number().optional(),
+            currency: z.string().optional(),
+            description: z.string().max(5000).optional(),
+            discountable: PermissiveBoolean.optional(),
+            discounts: z
+              .union([
+                z.array(
+                  z.object({
+                    coupon: z.string().max(5000).optional(),
+                    discount: z.string().max(5000).optional(),
+                    promotion_code: z.string().max(5000).optional(),
+                  }),
+                ),
+                z.enum([""]),
+              ])
+              .optional(),
+            invoiceitem: z.string().max(5000).optional(),
+            metadata: z.union([z.record(z.string()), z.enum([""])]).optional(),
+            period: z
+              .object({ end: z.coerce.number(), start: z.coerce.number() })
+              .optional(),
+            price: z.string().max(5000).optional(),
+            price_data: z
+              .object({
+                currency: z.string(),
+                product: z.string().max(5000),
+                tax_behavior: z
+                  .enum(["exclusive", "inclusive", "unspecified"])
+                  .optional(),
+                unit_amount: z.coerce.number().optional(),
+                unit_amount_decimal: z.string().optional(),
+              })
+              .optional(),
+            quantity: z.coerce.number().optional(),
+            tax_behavior: z
+              .enum(["exclusive", "inclusive", "unspecified"])
+              .optional(),
+            tax_code: z.union([z.string(), z.enum([""])]).optional(),
+            tax_rates: z
+              .union([z.array(z.string().max(5000)), z.enum([""])])
+              .optional(),
+            unit_amount: z.coerce.number().optional(),
+            unit_amount_decimal: z.string().optional(),
+          }),
+        ),
         z.object({
           amount: z.coerce.number().optional(),
           currency: z.string().optional(),
@@ -33951,8 +34482,9 @@ export function createRouter(implementation: Implementation): KoaRouter {
           unit_amount: z.coerce.number().optional(),
           unit_amount_decimal: z.string().optional(),
         }),
-      )
-      .optional(),
+      ])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     issuer: z
       .object({
         account: z.string().optional(),
@@ -34218,7 +34750,50 @@ export function createRouter(implementation: Implementation): KoaRouter {
       })
       .optional(),
     subscription_items: z
-      .array(
+      .union([
+        z.array(
+          z.object({
+            billing_thresholds: z
+              .union([z.object({ usage_gte: z.coerce.number() }), z.enum([""])])
+              .optional(),
+            clear_usage: PermissiveBoolean.optional(),
+            deleted: PermissiveBoolean.optional(),
+            discounts: z
+              .union([
+                z.array(
+                  z.object({
+                    coupon: z.string().max(5000).optional(),
+                    discount: z.string().max(5000).optional(),
+                    promotion_code: z.string().max(5000).optional(),
+                  }),
+                ),
+                z.enum([""]),
+              ])
+              .optional(),
+            id: z.string().max(5000).optional(),
+            metadata: z.union([z.record(z.string()), z.enum([""])]).optional(),
+            price: z.string().max(5000).optional(),
+            price_data: z
+              .object({
+                currency: z.string(),
+                product: z.string().max(5000),
+                recurring: z.object({
+                  interval: z.enum(["day", "month", "week", "year"]),
+                  interval_count: z.coerce.number().optional(),
+                }),
+                tax_behavior: z
+                  .enum(["exclusive", "inclusive", "unspecified"])
+                  .optional(),
+                unit_amount: z.coerce.number().optional(),
+                unit_amount_decimal: z.string().optional(),
+              })
+              .optional(),
+            quantity: z.coerce.number().optional(),
+            tax_rates: z
+              .union([z.array(z.string().max(5000)), z.enum([""])])
+              .optional(),
+          }),
+        ),
         z.object({
           billing_thresholds: z
             .union([z.object({ usage_gte: z.coerce.number() }), z.enum([""])])
@@ -34260,8 +34835,9 @@ export function createRouter(implementation: Implementation): KoaRouter {
             .union([z.array(z.string().max(5000)), z.enum([""])])
             .optional(),
         }),
-      )
-      .optional(),
+      ])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     subscription_proration_behavior: z
       .enum(["always_invoice", "create_prorations", "none"])
       .optional(),
@@ -34401,7 +34977,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getInvoicesInvoiceQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getInvoicesInvoiceBodySchema = z.object({}).optional()
@@ -34890,7 +35469,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getInvoicesInvoiceLinesQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -35364,7 +35946,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     status: z.enum(["closed", "pending", "reversed"]).optional(),
@@ -35445,7 +36030,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getIssuingAuthorizationsAuthorizationQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getIssuingAuthorizationsAuthorizationBodySchema = z
@@ -35708,7 +36296,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     email: z.string().optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     phone_number: z.string().optional(),
     starting_after: z.string().max(5000).optional(),
@@ -36822,7 +37413,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getIssuingCardholdersCardholderQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getIssuingCardholdersCardholderBodySchema = z.object({}).optional()
@@ -37934,7 +38528,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
     ending_before: z.string().max(5000).optional(),
     exp_month: z.coerce.number().optional(),
     exp_year: z.coerce.number().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     last4: z.string().max(5000).optional(),
     limit: z.coerce.number().optional(),
     personalization_design: z.string().max(5000).optional(),
@@ -39016,7 +39613,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getIssuingCardsCardQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getIssuingCardsCardBodySchema = z.object({}).optional()
@@ -40079,7 +40679,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     status: z
@@ -40394,7 +40997,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getIssuingDisputesDisputeQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getIssuingDisputesDisputeBodySchema = z.object({}).optional()
@@ -40754,9 +41360,15 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getIssuingPersonalizationDesignsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
-    lookup_keys: z.array(z.string().max(200)).optional(),
+    lookup_keys: z
+      .union([z.array(z.string().max(200)), z.string().max(200)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     preferences: z
       .object({
         is_default: PermissiveBoolean.optional(),
@@ -40911,7 +41523,12 @@ export function createRouter(implementation: Implementation): KoaRouter {
     z.object({ personalization_design: z.string().max(5000) })
 
   const getIssuingPersonalizationDesignsPersonalizationDesignQuerySchema =
-    z.object({ expand: z.array(z.string().max(5000)).optional() })
+    z.object({
+      expand: z
+        .union([z.array(z.string().max(5000)), z.string().max(5000)])
+        .optional()
+        .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
+    })
 
   const getIssuingPersonalizationDesignsPersonalizationDesignBodySchema = z
     .object({})
@@ -41076,7 +41693,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getIssuingPhysicalBundlesQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     status: z.enum(["active", "inactive", "review"]).optional(),
@@ -41158,7 +41778,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getIssuingPhysicalBundlesPhysicalBundleQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getIssuingPhysicalBundlesPhysicalBundleBodySchema = z
@@ -41225,7 +41848,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getIssuingSettlementsSettlementQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getIssuingSettlementsSettlementBodySchema = z.object({}).optional()
@@ -41355,7 +41981,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     status: z.enum(["active", "deleted", "requested", "suspended"]).optional(),
@@ -41429,7 +42058,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getIssuingTokensTokenQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getIssuingTokensTokenBodySchema = z.object({}).optional()
@@ -41562,7 +42194,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     type: z.enum(["capture", "refund"]).optional(),
@@ -41643,7 +42278,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getIssuingTransactionsTransactionQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getIssuingTransactionsTransactionBodySchema = z.object({}).optional()
@@ -41835,7 +42473,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getLinkAccountSessionsSessionQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getLinkAccountSessionsSessionBodySchema = z.object({}).optional()
@@ -41903,7 +42544,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       })
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     session: z.string().max(5000).optional(),
     starting_after: z.string().max(5000).optional(),
@@ -41980,7 +42624,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getLinkedAccountsAccountQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getLinkedAccountsAccountBodySchema = z.object({}).optional()
@@ -42107,7 +42754,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getLinkedAccountsAccountOwnersQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     ownership: z.string().max(5000),
     starting_after: z.string().max(5000).optional(),
@@ -42248,7 +42898,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getMandatesMandateParamSchema = z.object({ mandate: z.string() })
 
   const getMandatesMandateQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getMandatesMandateBodySchema = z.object({}).optional()
@@ -42321,7 +42974,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     customer: z.string().max(5000).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -43394,7 +44050,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   )
 
   const getPaymentIntentsSearchQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     page: z.string().max(5000).optional(),
     query: z.string().max(5000),
@@ -43477,7 +44136,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getPaymentIntentsIntentQuerySchema = z.object({
     client_secret: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getPaymentIntentsIntentBodySchema = z.object({}).optional()
@@ -45866,7 +46528,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getPaymentLinksQuerySchema = z.object({
     active: PermissiveBoolean.optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -46466,7 +47131,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getPaymentLinksPaymentLinkQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getPaymentLinksPaymentLinkBodySchema = z.object({}).optional()
@@ -47069,7 +47737,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getPaymentLinksPaymentLinkLineItemsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -47152,7 +47823,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getPaymentMethodConfigurationsQuerySchema = z.object({
     application: z.union([z.string().max(100), z.enum([""])]).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -47568,7 +48242,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getPaymentMethodConfigurationsConfigurationQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getPaymentMethodConfigurationsConfigurationBodySchema = z
@@ -47983,7 +48660,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
     domain_name: z.string().max(5000).optional(),
     enabled: PermissiveBoolean.optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -48115,7 +48795,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getPaymentMethodDomainsPaymentMethodDomainQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getPaymentMethodDomainsPaymentMethodDomainBodySchema = z
@@ -48305,7 +48988,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getPaymentMethodsQuerySchema = z.object({
     customer: z.string().max(5000).optional(),
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().optional(),
     type: z
@@ -48748,7 +49434,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getPaymentMethodsPaymentMethodQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getPaymentMethodsPaymentMethodBodySchema = z.object({}).optional()
@@ -49049,7 +49738,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     destination: z.string().optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     status: z.string().max(5000).optional(),
@@ -49175,7 +49867,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getPayoutsPayoutParamSchema = z.object({ payout: z.string().max(5000) })
 
   const getPayoutsPayoutQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getPayoutsPayoutBodySchema = z.object({}).optional()
@@ -49420,7 +50115,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     product: z.string().max(5000).optional(),
     starting_after: z.string().max(5000).optional(),
@@ -49633,7 +50331,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getPlansPlanParamSchema = z.object({ plan: z.string().max(5000) })
 
   const getPlansPlanQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getPlansPlanBodySchema = z.object({}).optional()
@@ -49762,9 +50463,15 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     currency: z.string().optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
-    lookup_keys: z.array(z.string().max(5000)).optional(),
+    lookup_keys: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     product: z.string().max(5000).optional(),
     recurring: z
       .object({
@@ -49973,7 +50680,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getPricesSearchQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     page: z.string().max(5000).optional(),
     query: z.string().max(5000),
@@ -50049,7 +50759,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getPricesPriceParamSchema = z.object({ price: z.string().max(5000) })
 
   const getPricesPriceQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getPricesPriceBodySchema = z.object({}).optional()
@@ -50213,8 +50926,14 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
-    ids: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
+    ids: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     shippable: PermissiveBoolean.optional(),
     starting_after: z.string().max(5000).optional(),
@@ -50399,7 +51118,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getProductsSearchQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     page: z.string().max(5000).optional(),
     query: z.string().max(5000),
@@ -50525,7 +51247,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getProductsIdParamSchema = z.object({ id: z.string().max(5000) })
 
   const getProductsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getProductsIdBodySchema = z.object({}).optional()
@@ -50668,7 +51393,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getProductsProductFeaturesQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -50862,7 +51590,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getProductsProductFeaturesIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getProductsProductFeaturesIdBodySchema = z.object({}).optional()
@@ -50936,7 +51667,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     customer: z.string().max(5000).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -51076,7 +51810,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getPromotionCodesPromotionCodeQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getPromotionCodesPromotionCodeBodySchema = z.object({}).optional()
@@ -51203,7 +51940,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getQuotesQuerySchema = z.object({
     customer: z.string().max(5000).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     status: z.enum(["accepted", "canceled", "draft", "open"]).optional(),
@@ -51450,7 +52190,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getQuotesQuoteParamSchema = z.object({ quote: z.string().max(5000) })
 
   const getQuotesQuoteQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getQuotesQuoteBodySchema = z.object({}).optional()
@@ -51801,7 +52544,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getQuotesQuoteComputedUpfrontLineItemsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -51950,7 +52696,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getQuotesQuoteLineItemsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -52029,7 +52778,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getQuotesQuotePdfParamSchema = z.object({ quote: z.string().max(5000) })
 
   const getQuotesQuotePdfQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getQuotesQuotePdfBodySchema = z.object({}).optional()
@@ -52102,7 +52854,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     payment_intent: z.string().max(5000).optional(),
     starting_after: z.string().max(5000).optional(),
@@ -52183,7 +52938,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getRadarEarlyFraudWarningsEarlyFraudWarningQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getRadarEarlyFraudWarningsEarlyFraudWarningBodySchema = z
@@ -52258,7 +53016,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     value: z.string().max(800).optional(),
@@ -52449,7 +53210,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getRadarValueListItemsItemQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getRadarValueListItemsItemBodySchema = z.object({}).optional()
@@ -52523,7 +53287,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -52721,7 +53488,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getRadarValueListsValueListQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getRadarValueListsValueListBodySchema = z.object({}).optional()
@@ -52853,7 +53623,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     payment_intent: z.string().max(5000).optional(),
     starting_after: z.string().optional(),
@@ -52986,7 +53759,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getRefundsRefundParamSchema = z.object({ refund: z.string() })
 
   const getRefundsRefundQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getRefundsRefundBodySchema = z.object({}).optional()
@@ -53165,7 +53941,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -53949,7 +54728,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getReportingReportRunsReportRunQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getReportingReportRunsReportRunBodySchema = z.object({}).optional()
@@ -54007,7 +54789,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   )
 
   const getReportingReportTypesQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getReportingReportTypesBodySchema = z.object({}).optional()
@@ -54082,7 +54867,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getReportingReportTypesReportTypeQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getReportingReportTypesReportTypeBodySchema = z.object({}).optional()
@@ -54155,7 +54943,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -54226,7 +55017,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getReviewsReviewParamSchema = z.object({ review: z.string().max(5000) })
 
   const getReviewsReviewQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getReviewsReviewBodySchema = z.object({}).optional()
@@ -54352,7 +55146,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     setup_intent: z.string().max(5000),
     starting_after: z.string().max(5000).optional(),
@@ -54436,7 +55233,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     customer: z.string().max(5000).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     payment_method: z.string().max(5000).optional(),
     starting_after: z.string().max(5000).optional(),
@@ -54998,7 +55798,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getSetupIntentsIntentQuerySchema = z.object({
     client_secret: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getSetupIntentsIntentBodySchema = z.object({}).optional()
@@ -56151,7 +56954,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     currency: z.string().optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -56307,7 +57113,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getShippingRatesShippingRateTokenQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getShippingRatesShippingRateTokenBodySchema = z.object({}).optional()
@@ -56449,7 +57258,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getSigmaScheduledQueryRunsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -56529,7 +57341,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getSigmaScheduledQueryRunsScheduledQueryRunQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getSigmaScheduledQueryRunsScheduledQueryRunBodySchema = z
@@ -56745,7 +57560,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getSourcesSourceQuerySchema = z.object({
     client_secret: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getSourcesSourceBodySchema = z.object({}).optional()
@@ -56947,7 +57765,12 @@ export function createRouter(implementation: Implementation): KoaRouter {
     })
 
   const getSourcesSourceMandateNotificationsMandateNotificationQuerySchema =
-    z.object({ expand: z.array(z.string().max(5000)).optional() })
+    z.object({
+      expand: z
+        .union([z.array(z.string().max(5000)), z.string().max(5000)])
+        .optional()
+        .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
+    })
 
   const getSourcesSourceMandateNotificationsMandateNotificationBodySchema = z
     .object({})
@@ -57019,7 +57842,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getSourcesSourceSourceTransactionsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -57106,7 +57932,12 @@ export function createRouter(implementation: Implementation): KoaRouter {
     })
 
   const getSourcesSourceSourceTransactionsSourceTransactionQuerySchema =
-    z.object({ expand: z.array(z.string().max(5000)).optional() })
+    z.object({
+      expand: z
+        .union([z.array(z.string().max(5000)), z.string().max(5000)])
+        .optional()
+        .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
+    })
 
   const getSourcesSourceSourceTransactionsSourceTransactionBodySchema = z
     .object({})
@@ -57233,7 +58064,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getSubscriptionItemsQuerySchema = z.object({
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().optional(),
     subscription: z.string().max(5000),
@@ -57475,7 +58309,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getSubscriptionItemsItemQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getSubscriptionItemsItemBodySchema = z.object({}).optional()
@@ -57649,7 +58486,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getSubscriptionItemsSubscriptionItemUsageRecordSummariesQuerySchema =
     z.object({
       ending_before: z.string().max(5000).optional(),
-      expand: z.array(z.string().max(5000)).optional(),
+      expand: z
+        .union([z.array(z.string().max(5000)), z.string().max(5000)])
+        .optional()
+        .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
       limit: z.coerce.number().optional(),
       starting_after: z.string().max(5000).optional(),
     })
@@ -57839,7 +58679,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     customer: z.string().max(5000).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     released_at: z
       .union([
@@ -58200,7 +59043,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getSubscriptionSchedulesScheduleQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getSubscriptionSchedulesScheduleBodySchema = z.object({}).optional()
@@ -58702,7 +59548,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     customer: z.string().max(5000).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     price: z.string().max(5000).optional(),
     starting_after: z.string().max(5000).optional(),
@@ -59174,7 +60023,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getSubscriptionsSearchQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     page: z.string().max(5000).optional(),
     query: z.string().max(5000),
@@ -59337,7 +60189,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getSubscriptionsSubscriptionExposedIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getSubscriptionsSubscriptionExposedIdBodySchema = z
@@ -60143,7 +60998,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTaxCalculationsCalculationLineItemsQuerySchema = z.object({
     ending_before: z.string().max(500).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(500).optional(),
   })
@@ -60230,7 +61088,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTaxRegistrationsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     status: z.enum(["active", "all", "expired", "scheduled"]).optional(),
@@ -60685,7 +61546,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTaxRegistrationsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTaxRegistrationsIdBodySchema = z.object({}).optional()
@@ -60809,7 +61673,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   )
 
   const getTaxSettingsQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTaxSettingsBodySchema = z.object({}).optional()
@@ -61058,7 +61925,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTaxTransactionsTransactionQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTaxTransactionsTransactionBodySchema = z.object({}).optional()
@@ -61121,7 +61991,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTaxTransactionsTransactionLineItemsQuerySchema = z.object({
     ending_before: z.string().max(500).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(500).optional(),
   })
@@ -61208,7 +62081,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTaxCodesQuerySchema = z.object({
     ending_before: z.string().optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().optional(),
   })
@@ -61279,7 +62155,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getTaxCodesIdParamSchema = z.object({ id: z.string().max(5000) })
 
   const getTaxCodesIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTaxCodesIdBodySchema = z.object({}).optional()
@@ -61336,7 +62215,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTaxIdsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     owner: z
       .object({
@@ -61592,7 +62474,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getTaxIdsIdParamSchema = z.object({ id: z.string().max(5000) })
 
   const getTaxIdsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTaxIdsIdBodySchema = z.object({}).optional()
@@ -61661,7 +62546,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     inclusive: PermissiveBoolean.optional(),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
@@ -61806,7 +62694,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTaxRatesTaxRateQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTaxRatesTaxRateBodySchema = z.object({}).optional()
@@ -61950,7 +62841,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTerminalConfigurationsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     is_account_default: PermissiveBoolean.optional(),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
@@ -62269,7 +63163,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTerminalConfigurationsConfigurationQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTerminalConfigurationsConfigurationBodySchema = z
@@ -62604,7 +63501,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTerminalLocationsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -62799,7 +63699,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTerminalLocationsLocationQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTerminalLocationsLocationBodySchema = z.object({}).optional()
@@ -62952,7 +63855,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     location: z.string().max(5000).optional(),
     serial_number: z.string().max(5000).optional(),
@@ -63140,7 +64046,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTerminalReadersReaderQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTerminalReadersReaderBodySchema = z.object({}).optional()
@@ -66288,7 +67197,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTestHelpersTestClocksQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -66480,7 +67392,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTestHelpersTestClocksTestClockQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTestHelpersTestClocksTestClockBodySchema = z.object({}).optional()
@@ -67930,7 +68845,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getTokensTokenParamSchema = z.object({ token: z.string().max(5000) })
 
   const getTokensTokenQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTokensTokenBodySchema = z.object({}).optional()
@@ -68009,7 +68927,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     status: z.enum(["canceled", "failed", "pending", "succeeded"]).optional(),
@@ -68134,7 +69055,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   const getTopupsTopupParamSchema = z.object({ topup: z.string().max(5000) })
 
   const getTopupsTopupQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTopupsTopupBodySchema = z.object({}).optional()
@@ -68317,7 +69241,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     destination: z.string().max(5000).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
     transfer_group: z.string().max(5000).optional(),
@@ -68446,7 +69373,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTransfersIdReversalsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -68591,7 +69521,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTransfersTransferQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTransfersTransferBodySchema = z.object({}).optional()
@@ -68718,7 +69651,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTransfersTransferReversalsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTransfersTransferReversalsIdBodySchema = z.object({}).optional()
@@ -68837,7 +69773,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTreasuryCreditReversalsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     financial_account: z.string(),
     limit: z.coerce.number().optional(),
     received_credit: z.string().max(5000).optional(),
@@ -68967,7 +69906,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTreasuryCreditReversalsCreditReversalQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTreasuryCreditReversalsCreditReversalBodySchema = z
@@ -69031,7 +69973,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTreasuryDebitReversalsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     financial_account: z.string(),
     limit: z.coerce.number().optional(),
     received_debit: z.string().max(5000).optional(),
@@ -69164,7 +70109,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTreasuryDebitReversalsDebitReversalQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTreasuryDebitReversalsDebitReversalBodySchema = z
@@ -69239,7 +70187,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -69413,7 +70364,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTreasuryFinancialAccountsFinancialAccountQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTreasuryFinancialAccountsFinancialAccountBodySchema = z
@@ -69584,7 +70538,12 @@ export function createRouter(implementation: Implementation): KoaRouter {
     z.object({ financial_account: z.string().max(5000) })
 
   const getTreasuryFinancialAccountsFinancialAccountFeaturesQuerySchema =
-    z.object({ expand: z.array(z.string().max(5000)).optional() })
+    z.object({
+      expand: z
+        .union([z.array(z.string().max(5000)), z.string().max(5000)])
+        .optional()
+        .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
+    })
 
   const getTreasuryFinancialAccountsFinancialAccountFeaturesBodySchema = z
     .object({})
@@ -69752,7 +70711,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTreasuryInboundTransfersQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     financial_account: z.string(),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
@@ -69889,7 +70851,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTreasuryInboundTransfersIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTreasuryInboundTransfersIdBodySchema = z.object({}).optional()
@@ -70024,7 +70989,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       .optional(),
     customer: z.string().max(5000).optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     financial_account: z.string(),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
@@ -70216,7 +71184,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTreasuryOutboundPaymentsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTreasuryOutboundPaymentsIdBodySchema = z.object({}).optional()
@@ -70334,7 +71305,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTreasuryOutboundTransfersQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     financial_account: z.string(),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
@@ -70483,7 +71457,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTreasuryOutboundTransfersOutboundTransferQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTreasuryOutboundTransfersOutboundTransferBodySchema = z
@@ -70610,7 +71587,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTreasuryReceivedCreditsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     financial_account: z.string(),
     limit: z.coerce.number().optional(),
     linked_flows: z
@@ -70699,7 +71679,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTreasuryReceivedCreditsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTreasuryReceivedCreditsIdBodySchema = z.object({}).optional()
@@ -70758,7 +71741,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getTreasuryReceivedDebitsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     financial_account: z.string(),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
@@ -70837,7 +71823,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTreasuryReceivedDebitsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTreasuryReceivedDebitsIdBodySchema = z.object({}).optional()
@@ -70918,7 +71907,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     financial_account: z.string(),
     limit: z.coerce.number().optional(),
     order_by: z.enum(["created", "effective_at"]).optional(),
@@ -71002,7 +71994,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTreasuryTransactionEntriesIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTreasuryTransactionEntriesIdBodySchema = z.object({}).optional()
@@ -71072,7 +72067,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
       ])
       .optional(),
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     financial_account: z.string(),
     limit: z.coerce.number().optional(),
     order_by: z.enum(["created", "posted_at"]).optional(),
@@ -71167,7 +72165,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getTreasuryTransactionsIdQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getTreasuryTransactionsIdBodySchema = z.object({}).optional()
@@ -71228,7 +72229,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
 
   const getWebhookEndpointsQuerySchema = z.object({
     ending_before: z.string().max(5000).optional(),
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
     limit: z.coerce.number().optional(),
     starting_after: z.string().max(5000).optional(),
   })
@@ -71762,7 +72766,10 @@ export function createRouter(implementation: Implementation): KoaRouter {
   })
 
   const getWebhookEndpointsWebhookEndpointQuerySchema = z.object({
-    expand: z.array(z.string().max(5000)).optional(),
+    expand: z
+      .union([z.array(z.string().max(5000)), z.string().max(5000)])
+      .optional()
+      .transform((it) => (Array.isArray(it) || it === undefined ? it : [it])),
   })
 
   const getWebhookEndpointsWebhookEndpointBodySchema = z.object({}).optional()
diff --git a/integration-tests/typescript-koa/src/generated/todo-lists.yaml/models.ts b/integration-tests/typescript-koa/src/generated/todo-lists.yaml/models.ts
index da6dcb289..693c813d7 100644
--- a/integration-tests/typescript-koa/src/generated/todo-lists.yaml/models.ts
+++ b/integration-tests/typescript-koa/src/generated/todo-lists.yaml/models.ts
@@ -8,7 +8,7 @@ export type t_Error = {
 }
 
 export type t_TodoList = {
-  created: string
+  created: Date
   id: string
   incompleteItemCount: number
   name: string
diff --git a/integration-tests/typescript-koa/src/generated/todo-lists.yaml/schemas.ts b/integration-tests/typescript-koa/src/generated/todo-lists.yaml/schemas.ts
index 3c99ec6ce..b276b1a7d 100644
--- a/integration-tests/typescript-koa/src/generated/todo-lists.yaml/schemas.ts
+++ b/integration-tests/typescript-koa/src/generated/todo-lists.yaml/schemas.ts
@@ -11,7 +11,10 @@ export const s_TodoList = z.object({
   name: z.string(),
   totalItemCount: z.coerce.number(),
   incompleteItemCount: z.coerce.number(),
-  created: z.string().datetime({ offset: true }),
+  created: z
+    .string()
+    .datetime({ offset: true })
+    .transform((it) => new Date(it)),
   updated: z.string().datetime({ offset: true }),
 })
 
diff --git a/packages/openapi-code-generator/src/core/input.ts b/packages/openapi-code-generator/src/core/input.ts
index 7aadbebec..85f1a1a91 100644
--- a/packages/openapi-code-generator/src/core/input.ts
+++ b/packages/openapi-code-generator/src/core/input.ts
@@ -368,6 +368,7 @@ function normalizeSchemaObject(
   const base: IRModelBase = {
     nullable: schemaObject.nullable || false,
     readOnly: schemaObject.readOnly || false,
+    "x-alpha-transform": schemaObject["x-alpha-transform"],
   }
 
   switch (schemaObject.type) {
diff --git a/packages/openapi-code-generator/src/core/openapi-types-normalized.ts b/packages/openapi-code-generator/src/core/openapi-types-normalized.ts
index da549f446..f583423c0 100644
--- a/packages/openapi-code-generator/src/core/openapi-types-normalized.ts
+++ b/packages/openapi-code-generator/src/core/openapi-types-normalized.ts
@@ -8,6 +8,13 @@ export interface IRModelBase {
   // Note: meaningless for top level objects, maybe we can exclude these somehow in that case
   nullable: boolean /* false */
   readOnly: boolean /* false */
+
+  "x-alpha-transform"?:
+    | {
+        fn?: string | undefined
+        type?: string | undefined
+      }
+    | undefined
 }
 
 export type IRModelNumericFormat = "int32" | "int64" | "float" | "double"
diff --git a/packages/openapi-code-generator/src/core/openapi-types.ts b/packages/openapi-code-generator/src/core/openapi-types.ts
index bd4cef0ff..4f9ad16b8 100644
--- a/packages/openapi-code-generator/src/core/openapi-types.ts
+++ b/packages/openapi-code-generator/src/core/openapi-types.ts
@@ -248,6 +248,14 @@ export interface Schema {
   externalDocs?: ExternalDocumentation | undefined
   deprecated?: boolean | undefined
   // xml?: XML | undefined
+
+  // TODO: not yet supported by joi
+  "x-alpha-transform"?:
+    | {
+        fn?: string | undefined
+        type?: string | undefined
+      }
+    | undefined
 }
 
 export interface Discriminator {
diff --git a/packages/openapi-code-generator/src/typescript/common/schema-builders/abstract-schema-builder.ts b/packages/openapi-code-generator/src/typescript/common/schema-builders/abstract-schema-builder.ts
index 4c30f120e..2459e8fed 100644
--- a/packages/openapi-code-generator/src/typescript/common/schema-builders/abstract-schema-builder.ts
+++ b/packages/openapi-code-generator/src/typescript/common/schema-builders/abstract-schema-builder.ts
@@ -163,7 +163,31 @@ export abstract class AbstractSchemaBuilder<
       if (parameter.required) {
         model.required.push(parameter.name)
       }
-      model.properties[parameter.name] = parameter.schema
+
+      // TODO: support $ref properly
+      if (
+        parameter.in === "query" &&
+        !isRef(parameter.schema) &&
+        parameter.schema.type === "array"
+      ) {
+        model.properties[parameter.name] = {
+          type: "object",
+          additionalProperties: false,
+          properties: {},
+          readOnly: false,
+          allOf: [],
+          nullable: false,
+          oneOf: [],
+          required: [],
+          anyOf: [parameter.schema, parameter.schema.items],
+          "x-alpha-transform": {
+            fn: ((it: unknown) =>
+              Array.isArray(it) || it === undefined ? it : [it]).toString(),
+          },
+        }
+      } else {
+        model.properties[parameter.name] = parameter.schema
+      }
     }
 
     return this.fromModel(model, true, true)
@@ -304,6 +328,10 @@ export abstract class AbstractSchemaBuilder<
 
     result = required ? this.required(result) : this.optional(result)
 
+    if (model["x-alpha-transform"]?.fn) {
+      result = this.transform(result, model["x-alpha-transform"]?.fn)
+    }
+
     return result
   }
 
@@ -327,6 +355,11 @@ export abstract class AbstractSchemaBuilder<
 
   protected abstract union(schemas: string[]): string
 
+  protected abstract transform(
+    schema: string,
+    transformation: string | ((it: unknown) => unknown),
+  ): string
+
   protected abstract nullable(schema: string): string
 
   protected abstract optional(schema: string): string
diff --git a/packages/openapi-code-generator/src/typescript/common/schema-builders/joi-schema-builder.ts b/packages/openapi-code-generator/src/typescript/common/schema-builders/joi-schema-builder.ts
index 837086ef1..eea526797 100644
--- a/packages/openapi-code-generator/src/typescript/common/schema-builders/joi-schema-builder.ts
+++ b/packages/openapi-code-generator/src/typescript/common/schema-builders/joi-schema-builder.ts
@@ -108,6 +108,14 @@ export class JoiBuilder extends AbstractSchemaBuilder<
       .join(".")
   }
 
+  protected transform(
+    schema: string,
+    transformation: string | ((it: unknown) => unknown),
+  ) {
+    // TODO: is it possible to do arbitrary transformations with `joi`?
+    return schema
+  }
+
   protected nullable(schema: string): string {
     return [schema, "allow(null)"].join(".")
   }
diff --git a/packages/openapi-code-generator/src/typescript/common/schema-builders/zod-schema-builder.ts b/packages/openapi-code-generator/src/typescript/common/schema-builders/zod-schema-builder.ts
index 3876b3208..7f161c5bf 100644
--- a/packages/openapi-code-generator/src/typescript/common/schema-builders/zod-schema-builder.ts
+++ b/packages/openapi-code-generator/src/typescript/common/schema-builders/zod-schema-builder.ts
@@ -133,6 +133,15 @@ export class ZodBuilder extends AbstractSchemaBuilder<
       .join(".")
   }
 
+  protected transform(
+    schema: string,
+    transformation: string | ((it: unknown) => unknown),
+  ) {
+    return [schema, `transform(${transformation.toString()})`]
+      .filter(isDefined)
+      .join(".")
+  }
+
   protected nullable(schema: string): string {
     return [schema, "nullable()"].filter(isDefined).join(".")
   }
diff --git a/packages/openapi-code-generator/src/typescript/common/type-builder.ts b/packages/openapi-code-generator/src/typescript/common/type-builder.ts
index 41b3627a8..169cf0de5 100644
--- a/packages/openapi-code-generator/src/typescript/common/type-builder.ts
+++ b/packages/openapi-code-generator/src/typescript/common/type-builder.ts
@@ -145,7 +145,9 @@ export class TypeBuilder implements ICompilable {
       result.push(...schemaObject.anyOf.flatMap(this.schemaObjectToTypes))
     }
 
-    if (result.length === 0) {
+    if (schemaObject["x-alpha-transform"]?.type) {
+      result.push(schemaObject["x-alpha-transform"]?.type)
+    } else if (result.length === 0) {
       switch (schemaObject.type) {
         case "array": {
           result.push(array(this.schemaObjectToType(schemaObject.items)))
diff --git a/packages/openapi-code-generator/src/typescript/typescript-koa/typescript-koa.generator.ts b/packages/openapi-code-generator/src/typescript/typescript-koa/typescript-koa.generator.ts
index 701a9cb87..ff290fc54 100644
--- a/packages/openapi-code-generator/src/typescript/typescript-koa/typescript-koa.generator.ts
+++ b/packages/openapi-code-generator/src/typescript/typescript-koa/typescript-koa.generator.ts
@@ -25,14 +25,14 @@ import {
 
 function reduceParamsToOpenApiSchema(parameters: IRParameter[]): IRModelObject {
   return parameters.reduce(
-    (acc, parameter) => {
-      acc.properties[parameter.name] = parameter.schema
+    (model, parameter) => {
+      model.properties[parameter.name] = parameter.schema
 
       if (parameter.required) {
-        acc.required.push(parameter.name)
+        model.required.push(parameter.name)
       }
 
-      return acc
+      return model
     },
     {
       type: "object",