diff --git a/packages/global/openapi/core/chat/completion/api.ts b/packages/global/openapi/core/chat/completion/api.ts
index d9ed35a327..a48e07a9d0 100644
--- a/packages/global/openapi/core/chat/completion/api.ts
+++ b/packages/global/openapi/core/chat/completion/api.ts
@@ -8,23 +8,28 @@ import { OutLinkChatAuthSchema } from '../../../../support/permission/chat';
 import { StoreEdgeItemTypeSchema } from '../../../../core/workflow/type/edge';
 import { OpenAPIStoreNodeItemTypeSchema } from '../../workflow/node';
 
+const nullishToUndefined = <T extends z.ZodTypeAny>(schema: T) =>
+  z.preprocess((v) => v ?? undefined, schema);
+
 const WebCompletionsSchema = z.object({
-  chatId: z
-    .string()
-    .max(1024)
-    .nullish()
-    .meta({ description: '聊天ID, 传入的话会自动获取历史记录，不传入则认为是新对话' }),
-  appId: ObjectIdSchema.nullish(),
-  customUid: z.string().max(1024).nullish().meta({ description: '自定义用户ID(分享链接)' }),
-  metadata: z.record(z.string(), z.any()).nullish().meta({ description: '元数据' })
+  chatId: nullishToUndefined(z.string().max(1024).optional()).meta({
+    description: '聊天ID, 传入的话会自动获取历史记录，不传入则认为是新对话'
+  }),
+  appId: nullishToUndefined(ObjectIdSchema.optional()),
+  customUid: nullishToUndefined(z.string().max(1024).optional()).meta({
+    description: '自定义用户ID(分享链接)'
+  }),
+  metadata: nullishToUndefined(z.record(z.string(), z.any()).optional()).meta({
+    description: '元数据'
+  })
 });
 
 // completions 接口实际上并没有用完所有字段，所以这里就取局部即可
 const ChatCompletionCreateParamsSchema = z.object({
-  messages: z.array(ChatCompletionMessageParamSchema).nullish().default([]).meta({
+  messages: nullishToUndefined(z.array(ChatCompletionMessageParamSchema).default([])).meta({
     description: '消息列表'
   }),
-  stream: z.boolean().nullish().default(false).meta({
+  stream: nullishToUndefined(z.boolean().default(false)).meta({
     description: '是否流式返回'
   })
 });
@@ -32,23 +37,24 @@ const ChatCompletionCreateParamsSchema = z.object({
 export const CompletionsPropsSchema = OutLinkChatAuthSchema.extend(WebCompletionsSchema.shape)
   .extend(ChatCompletionCreateParamsSchema.shape)
   .extend({
-    variables: z.record(z.string(), z.any()).nullish().default({}).meta({
+    variables: nullishToUndefined(z.record(z.string(), z.any()).default({})).meta({
       description: '全局变量或插件输入'
     }),
-    responseChatItemId: z
-      .string()
-      .nullish()
-      .default(() => getNanoid())
-      .meta({
-        description: '自定义响应的 assistant 的消息 ID，如果不传入，则自动生成一个'
-      }),
-    detail: z.boolean().nullish().default(false).meta({
+    responseChatItemId: nullishToUndefined(
+      z
+        .string()
+        .default(() => getNanoid())
+        .meta({
+          description: '自定义响应的 assistant 的消息 ID，如果不传入，则自动生成一个'
+        })
+    ),
+    detail: nullishToUndefined(z.boolean().default(false)).meta({
       description: '是否返回详细信息，包括 reasoning_content, tool_calls, usage 等'
     }),
-    retainDatasetCite: z.boolean().nullish().default(false).meta({
+    retainDatasetCite: nullishToUndefined(z.boolean().default(false)).meta({
       description: '是否保留数据集引用'
     }),
-    showSkillReferences: z.boolean().nullish().default(false).meta({
+    showSkillReferences: nullishToUndefined(z.boolean().default(false)).meta({
       description: '是否显示技能引用'
     })
   });
@@ -134,7 +140,7 @@ export const ChatTestPropsSchema = z.object({
   nodes: z.array(OpenAPIStoreNodeItemTypeSchema).meta({ description: '节点列表' }),
   edges: z.array(StoreEdgeItemTypeSchema).meta({ description: '边列表' }),
   chatConfig: AppChatConfigTypeSchema.meta({ description: '聊天配置' }),
-  variables: z.record(z.string(), z.any()).nullish().default({}).meta({
+  variables: nullishToUndefined(z.record(z.string(), z.any()).default({})).meta({
     description: '全局变量或插件输入'
   }),
   appId: ObjectIdSchema.meta({ description: '应用ID' }),