diff --git a/content/docs/references/data/object.mdx b/content/docs/references/data/object.mdx
index b9a67b513..174338899 100644
--- a/content/docs/references/data/object.mdx
+++ b/content/docs/references/data/object.mdx
@@ -85,7 +85,7 @@ const result = ApiMethodSchema.parse(data);
 | **abstract** | `boolean` | optional | Is abstract base object (cannot be instantiated) |
 | **datasource** | `string` | optional | Target Datasource ID. "default" is the primary DB. |
 | **tableName** | `string` | optional | Physical table/collection name in the target datasource |
-| **fields** | `Record<string, object>` | ✅ | Field definitions map |
+| **fields** | `Record<string, object>` | ✅ | Field definitions map. Keys must be snake_case identifiers. |
 | **indexes** | `object[]` | optional | Database performance indexes |
 | **tenancy** | `object` | optional | Multi-tenancy configuration for SaaS applications |
 | **softDelete** | `object` | optional | Soft delete (trash/recycle bin) configuration |
diff --git a/examples/msw-react-crud/objectstack.config.ts b/examples/msw-react-crud/objectstack.config.ts
index 9334ecec8..0896fa296 100644
--- a/examples/msw-react-crud/objectstack.config.ts
+++ b/examples/msw-react-crud/objectstack.config.ts
@@ -20,8 +20,8 @@ export const TaskObject = {
     id: { name: 'id', label: 'ID', type: 'text', required: true },
     subject: { name: 'subject', label: 'Subject', type: 'text', required: true },
     priority: { name: 'priority', label: 'Priority', type: 'number', defaultValue: 5 },
-    isCompleted: { name: 'isCompleted', label: 'Completed', type: 'boolean', defaultValue: false },
-    createdAt: { name: 'createdAt', label: 'Created At', type: 'datetime' }
+    is_completed: { name: 'is_completed', label: 'Completed', type: 'boolean', defaultValue: false },
+    created_at: { name: 'created_at', label: 'Created At', type: 'datetime' }
   }
 };
 
diff --git a/packages/spec/json-schema/data/Object.json b/packages/spec/json-schema/data/Object.json
index e4a43d83c..6bccad7b1 100644
--- a/packages/spec/json-schema/data/Object.json
+++ b/packages/spec/json-schema/data/Object.json
@@ -913,7 +913,10 @@
             ],
             "additionalProperties": false
           },
-          "description": "Field definitions map"
+          "propertyNames": {
+            "pattern": "^[a-z_][a-z0-9_]*$"
+          },
+          "description": "Field definitions map. Keys must be snake_case identifiers."
         },
         "indexes": {
           "type": "array",
diff --git a/packages/spec/src/data/object.test.ts b/packages/spec/src/data/object.test.ts
index 19185f8fc..2692bc146 100644
--- a/packages/spec/src/data/object.test.ts
+++ b/packages/spec/src/data/object.test.ts
@@ -136,6 +136,129 @@ describe('ObjectSchema', () => {
 
       expect(() => ObjectSchema.parse(objectWithFields)).not.toThrow();
     });
+
+    it('should enforce snake_case for field names', () => {
+      // Valid snake_case field names
+      const validFieldNames = ['first_name', 'last_name', 'email', 'company_name', 'annual_revenue', '_system_id'];
+      
+      validFieldNames.forEach(fieldName => {
+        const obj = {
+          name: 'test_object',
+          fields: {
+            [fieldName]: {
+              type: 'text' as const,
+              label: 'Test Field',
+            },
+          },
+        };
+        expect(() => ObjectSchema.parse(obj)).not.toThrow();
+      });
+    });
+
+    it('should reject PascalCase field names', () => {
+      const invalidObject = {
+        name: 'lead',
+        fields: {
+          FirstName: {
+            type: 'text' as const,
+            label: '名',
+          },
+        },
+      };
+
+      expect(() => ObjectSchema.parse(invalidObject)).toThrow();
+      expect(() => ObjectSchema.parse(invalidObject)).toThrow(/Field names must be lowercase snake_case/);
+    });
+
+    it('should reject camelCase field names', () => {
+      const invalidObject = {
+        name: 'lead',
+        fields: {
+          firstName: {
+            type: 'text' as const,
+            label: 'First Name',
+          },
+        },
+      };
+
+      expect(() => ObjectSchema.parse(invalidObject)).toThrow();
+      expect(() => ObjectSchema.parse(invalidObject)).toThrow(/Field names must be lowercase snake_case/);
+    });
+
+    it('should reject kebab-case field names', () => {
+      const invalidObject = {
+        name: 'lead',
+        fields: {
+          'first-name': {
+            type: 'text' as const,
+            label: 'First Name',
+          },
+        },
+      };
+
+      expect(() => ObjectSchema.parse(invalidObject)).toThrow();
+      expect(() => ObjectSchema.parse(invalidObject)).toThrow(/Field names must be lowercase snake_case/);
+    });
+
+    it('should reject field names with spaces', () => {
+      const invalidObject = {
+        name: 'lead',
+        fields: {
+          'first name': {
+            type: 'text' as const,
+            label: 'First Name',
+          },
+        },
+      };
+
+      expect(() => ObjectSchema.parse(invalidObject)).toThrow();
+      expect(() => ObjectSchema.parse(invalidObject)).toThrow(/Field names must be lowercase snake_case/);
+    });
+
+    it('should reject field names starting with numbers', () => {
+      const invalidObject = {
+        name: 'lead',
+        fields: {
+          '123field': {
+            type: 'text' as const,
+            label: 'Field',
+          },
+        },
+      };
+
+      expect(() => ObjectSchema.parse(invalidObject)).toThrow();
+      expect(() => ObjectSchema.parse(invalidObject)).toThrow(/Field names must be lowercase snake_case/);
+    });
+
+    it('should reject mixed-case field names like in AI-generated objects', () => {
+      // This is the exact problem from the issue
+      const aiGeneratedObject = {
+        name: 'lead',
+        label: '线索',
+        fields: {
+          FirstName: {
+            type: 'text' as const,
+            label: '名',
+            maxLength: 40,
+          },
+          LastName: {
+            type: 'text' as const,
+            label: '姓',
+            required: true,
+            maxLength: 80,
+          },
+          Company: {
+            type: 'text' as const,
+            label: '公司',
+            required: true,
+            maxLength: 255,
+          },
+        },
+      };
+
+      expect(() => ObjectSchema.parse(aiGeneratedObject)).toThrow();
+      expect(() => ObjectSchema.parse(aiGeneratedObject)).toThrow(/Field names must be lowercase snake_case/);
+    });
   });
 
   describe('Object Metadata', () => {
diff --git a/packages/spec/src/data/object.zod.ts b/packages/spec/src/data/object.zod.ts
index e4f239c1c..dc4796961 100644
--- a/packages/spec/src/data/object.zod.ts
+++ b/packages/spec/src/data/object.zod.ts
@@ -217,7 +217,9 @@ const ObjectSchemaBase = z.object({
   /** 
    * Data Model 
    */
-  fields: z.record(FieldSchema).describe('Field definitions map'),
+  fields: z.record(z.string().regex(/^[a-z_][a-z0-9_]*$/, {
+    message: 'Field names must be lowercase snake_case (e.g., "first_name", "company", "annual_revenue")',
+  }), FieldSchema).describe('Field definitions map. Keys must be snake_case identifiers.'),
   indexes: z.array(IndexSchema).optional().describe('Database performance indexes'),
   
   /**