diff --git a/packages/language/src/generated/ast.ts b/packages/language/src/generated/ast.ts
index 98b461285..b4d7e6d82 100644
--- a/packages/language/src/generated/ast.ts
+++ b/packages/language/src/generated/ast.ts
@@ -20,7 +20,7 @@ export const ZModelTerminals = {
     SL_COMMENT: /\/\/[^\n\r]*/,
 };
 
-export type AbstractDeclaration = Attribute | DataModel | DataSource | Enum | FunctionDecl | GeneratorDecl | Plugin;
+export type AbstractDeclaration = Attribute | DataModel | DataSource | Enum | FunctionDecl | GeneratorDecl | Plugin | TypeDef;
 
 export const AbstractDeclaration = 'AbstractDeclaration';
 
@@ -78,10 +78,10 @@ export function isReferenceTarget(item: unknown): item is ReferenceTarget {
     return reflection.isInstance(item, ReferenceTarget);
 }
 
-export type RegularID = 'abstract' | 'attribute' | 'datasource' | 'enum' | 'import' | 'in' | 'model' | 'plugin' | 'view' | string;
+export type RegularID = 'abstract' | 'attribute' | 'datasource' | 'enum' | 'import' | 'in' | 'model' | 'plugin' | 'type' | 'view' | string;
 
 export function isRegularID(item: unknown): item is RegularID {
-    return item === 'model' || item === 'enum' || item === 'attribute' || item === 'datasource' || item === 'plugin' || item === 'abstract' || item === 'in' || item === 'view' || item === 'import' || (typeof item === 'string' && (/[_a-zA-Z][\w_]*/.test(item)));
+    return item === 'model' || item === 'enum' || item === 'attribute' || item === 'datasource' || item === 'plugin' || item === 'abstract' || item === 'in' || item === 'view' || item === 'import' || item === 'type' || (typeof item === 'string' && (/[_a-zA-Z][\w_]*/.test(item)));
 }
 
 export type RegularIDWithTypeNames = 'Any' | 'BigInt' | 'Boolean' | 'Bytes' | 'DateTime' | 'Decimal' | 'Float' | 'Int' | 'Json' | 'Null' | 'Object' | 'String' | 'Unsupported' | RegularID;
@@ -90,7 +90,7 @@ export function isRegularIDWithTypeNames(item: unknown): item is RegularIDWithTy
     return isRegularID(item) || item === 'String' || item === 'Boolean' || item === 'Int' || item === 'BigInt' || item === 'Float' || item === 'Decimal' || item === 'DateTime' || item === 'Json' || item === 'Bytes' || item === 'Null' || item === 'Object' || item === 'Any' || item === 'Unsupported';
 }
 
-export type TypeDeclaration = DataModel | Enum;
+export type TypeDeclaration = DataModel | Enum | TypeDef;
 
 export const TypeDeclaration = 'TypeDeclaration';
 
@@ -305,7 +305,7 @@ export function isDataModelField(item: unknown): item is DataModelField {
 }
 
 export interface DataModelFieldAttribute extends AstNode {
-    readonly $container: DataModelField | EnumField;
+    readonly $container: DataModelField | EnumField | TypeDefField;
     readonly $type: 'DataModelFieldAttribute';
     args: Array<AttributeArg>
     decl: Reference<Attribute>
@@ -620,6 +620,50 @@ export function isThisExpr(item: unknown): item is ThisExpr {
     return reflection.isInstance(item, ThisExpr);
 }
 
+export interface TypeDef extends AstNode {
+    readonly $container: Model;
+    readonly $type: 'TypeDef';
+    comments: Array<string>
+    fields: Array<TypeDefField>
+    name: RegularID
+}
+
+export const TypeDef = 'TypeDef';
+
+export function isTypeDef(item: unknown): item is TypeDef {
+    return reflection.isInstance(item, TypeDef);
+}
+
+export interface TypeDefField extends AstNode {
+    readonly $container: TypeDef;
+    readonly $type: 'TypeDefField';
+    attributes: Array<DataModelFieldAttribute>
+    comments: Array<string>
+    name: RegularIDWithTypeNames
+    type: TypeDefFieldType
+}
+
+export const TypeDefField = 'TypeDefField';
+
+export function isTypeDefField(item: unknown): item is TypeDefField {
+    return reflection.isInstance(item, TypeDefField);
+}
+
+export interface TypeDefFieldType extends AstNode {
+    readonly $container: TypeDefField;
+    readonly $type: 'TypeDefFieldType';
+    array: boolean
+    optional: boolean
+    reference?: Reference<TypeDef>
+    type?: BuiltinType
+}
+
+export const TypeDefFieldType = 'TypeDefFieldType';
+
+export function isTypeDefFieldType(item: unknown): item is TypeDefFieldType {
+    return reflection.isInstance(item, TypeDefFieldType);
+}
+
 export interface UnaryExpr extends AstNode {
     readonly $container: Argument | ArrayExpr | AttributeArg | BinaryExpr | ConfigArrayExpr | ConfigField | ConfigInvocationArg | FieldInitializer | FunctionDecl | MemberAccessExpr | PluginField | ReferenceArg | UnaryExpr | UnsupportedFieldType;
     readonly $type: 'UnaryExpr';
@@ -691,6 +735,9 @@ export type ZModelAstType = {
     StringLiteral: StringLiteral
     ThisExpr: ThisExpr
     TypeDeclaration: TypeDeclaration
+    TypeDef: TypeDef
+    TypeDefField: TypeDefField
+    TypeDefFieldType: TypeDefFieldType
     UnaryExpr: UnaryExpr
     UnsupportedFieldType: UnsupportedFieldType
 }
@@ -698,7 +745,7 @@ export type ZModelAstType = {
 export class ZModelAstReflection extends AbstractAstReflection {
 
     getAllTypes(): string[] {
-        return ['AbstractDeclaration', 'Argument', 'ArrayExpr', 'Attribute', 'AttributeArg', 'AttributeParam', 'AttributeParamType', 'BinaryExpr', 'BooleanLiteral', 'ConfigArrayExpr', 'ConfigExpr', 'ConfigField', 'ConfigInvocationArg', 'ConfigInvocationExpr', 'DataModel', 'DataModelAttribute', 'DataModelField', 'DataModelFieldAttribute', 'DataModelFieldType', 'DataSource', 'Enum', 'EnumField', 'Expression', 'FieldInitializer', 'FunctionDecl', 'FunctionParam', 'FunctionParamType', 'GeneratorDecl', 'InternalAttribute', 'InvocationExpr', 'LiteralExpr', 'MemberAccessExpr', 'Model', 'ModelImport', 'NullExpr', 'NumberLiteral', 'ObjectExpr', 'Plugin', 'PluginField', 'ReferenceArg', 'ReferenceExpr', 'ReferenceTarget', 'StringLiteral', 'ThisExpr', 'TypeDeclaration', 'UnaryExpr', 'UnsupportedFieldType'];
+        return ['AbstractDeclaration', 'Argument', 'ArrayExpr', 'Attribute', 'AttributeArg', 'AttributeParam', 'AttributeParamType', 'BinaryExpr', 'BooleanLiteral', 'ConfigArrayExpr', 'ConfigExpr', 'ConfigField', 'ConfigInvocationArg', 'ConfigInvocationExpr', 'DataModel', 'DataModelAttribute', 'DataModelField', 'DataModelFieldAttribute', 'DataModelFieldType', 'DataSource', 'Enum', 'EnumField', 'Expression', 'FieldInitializer', 'FunctionDecl', 'FunctionParam', 'FunctionParamType', 'GeneratorDecl', 'InternalAttribute', 'InvocationExpr', 'LiteralExpr', 'MemberAccessExpr', 'Model', 'ModelImport', 'NullExpr', 'NumberLiteral', 'ObjectExpr', 'Plugin', 'PluginField', 'ReferenceArg', 'ReferenceExpr', 'ReferenceTarget', 'StringLiteral', 'ThisExpr', 'TypeDeclaration', 'TypeDef', 'TypeDefField', 'TypeDefFieldType', 'UnaryExpr', 'UnsupportedFieldType'];
     }
 
     protected override computeIsSubtype(subtype: string, supertype: string): boolean {
@@ -729,7 +776,8 @@ export class ZModelAstReflection extends AbstractAstReflection {
                 return this.isSubtype(ConfigExpr, supertype);
             }
             case DataModel:
-            case Enum: {
+            case Enum:
+            case TypeDef: {
                 return this.isSubtype(AbstractDeclaration, supertype) || this.isSubtype(TypeDeclaration, supertype);
             }
             case DataModelField:
@@ -772,6 +820,9 @@ export class ZModelAstReflection extends AbstractAstReflection {
             case 'ReferenceExpr:target': {
                 return ReferenceTarget;
             }
+            case 'TypeDefFieldType:reference': {
+                return TypeDef;
+            }
             default: {
                 throw new Error(`${referenceId} is not a valid reference id.`);
             }
@@ -989,6 +1040,33 @@ export class ZModelAstReflection extends AbstractAstReflection {
                     ]
                 };
             }
+            case 'TypeDef': {
+                return {
+                    name: 'TypeDef',
+                    mandatory: [
+                        { name: 'comments', type: 'array' },
+                        { name: 'fields', type: 'array' }
+                    ]
+                };
+            }
+            case 'TypeDefField': {
+                return {
+                    name: 'TypeDefField',
+                    mandatory: [
+                        { name: 'attributes', type: 'array' },
+                        { name: 'comments', type: 'array' }
+                    ]
+                };
+            }
+            case 'TypeDefFieldType': {
+                return {
+                    name: 'TypeDefFieldType',
+                    mandatory: [
+                        { name: 'array', type: 'boolean' },
+                        { name: 'optional', type: 'boolean' }
+                    ]
+                };
+            }
             default: {
                 return {
                     name: type,
diff --git a/packages/language/src/generated/grammar.ts b/packages/language/src/generated/grammar.ts
index 3b172570d..01c492bd5 100644
--- a/packages/language/src/generated/grammar.ts
+++ b/packages/language/src/generated/grammar.ts
@@ -70,7 +70,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@64"
+                "$ref": "#/rules@67"
               },
               "arguments": []
             }
@@ -126,21 +126,28 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@41"
+              "$ref": "#/rules@40"
             },
             "arguments": []
           },
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@43"
+              "$ref": "#/rules@44"
             },
             "arguments": []
           },
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@48"
+              "$ref": "#/rules@46"
+            },
+            "arguments": []
+          },
+          {
+            "$type": "RuleCall",
+            "rule": {
+              "$ref": "#/rules@51"
             },
             "arguments": []
           }
@@ -162,7 +169,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@66"
+              "$ref": "#/rules@69"
             },
             "arguments": [],
             "cardinality": "*"
@@ -178,7 +185,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@46"
+                "$ref": "#/rules@49"
               },
               "arguments": []
             }
@@ -222,7 +229,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@66"
+              "$ref": "#/rules@69"
             },
             "arguments": [],
             "cardinality": "*"
@@ -238,7 +245,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@46"
+                "$ref": "#/rules@49"
               },
               "arguments": []
             }
@@ -282,7 +289,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@66"
+              "$ref": "#/rules@69"
             },
             "arguments": [],
             "cardinality": "*"
@@ -294,7 +301,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@46"
+                "$ref": "#/rules@49"
               },
               "arguments": []
             }
@@ -333,7 +340,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@66"
+              "$ref": "#/rules@69"
             },
             "arguments": [],
             "cardinality": "*"
@@ -349,7 +356,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@46"
+                "$ref": "#/rules@49"
               },
               "arguments": []
             }
@@ -393,7 +400,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@66"
+              "$ref": "#/rules@69"
             },
             "arguments": [],
             "cardinality": "*"
@@ -405,7 +412,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@46"
+                "$ref": "#/rules@49"
               },
               "arguments": []
             }
@@ -481,7 +488,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
         "terminal": {
           "$type": "RuleCall",
           "rule": {
-            "$ref": "#/rules@65"
+            "$ref": "#/rules@68"
           },
           "arguments": []
         }
@@ -503,7 +510,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
         "terminal": {
           "$type": "RuleCall",
           "rule": {
-            "$ref": "#/rules@64"
+            "$ref": "#/rules@67"
           },
           "arguments": []
         }
@@ -525,7 +532,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
         "terminal": {
           "$type": "RuleCall",
           "rule": {
-            "$ref": "#/rules@58"
+            "$ref": "#/rules@61"
           },
           "arguments": []
         }
@@ -649,7 +656,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@63"
+                "$ref": "#/rules@66"
               },
               "arguments": []
             }
@@ -747,7 +754,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@63"
+                "$ref": "#/rules@66"
               },
               "arguments": []
             }
@@ -956,7 +963,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
               "terminal": {
                 "$type": "RuleCall",
                 "rule": {
-                  "$ref": "#/rules@47"
+                  "$ref": "#/rules@50"
                 },
                 "arguments": []
               },
@@ -1055,7 +1062,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@63"
+                "$ref": "#/rules@66"
               },
               "arguments": []
             }
@@ -1169,14 +1176,14 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@46"
+                    "$ref": "#/rules@49"
                   },
                   "arguments": []
                 },
                 {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@64"
+                    "$ref": "#/rules@67"
                   },
                   "arguments": []
                 }
@@ -1221,7 +1228,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "CrossReference",
               "type": {
-                "$ref": "#/rules@43"
+                "$ref": "#/rules@46"
               },
               "deprecatedSyntax": false
             }
@@ -1894,7 +1901,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@66"
+                "$ref": "#/rules@69"
               },
               "arguments": []
             },
@@ -1927,7 +1934,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                     "terminal": {
                       "$type": "RuleCall",
                       "rule": {
-                        "$ref": "#/rules@46"
+                        "$ref": "#/rules@49"
                       },
                       "arguments": []
                     }
@@ -1997,7 +2004,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                     "terminal": {
                       "$type": "RuleCall",
                       "rule": {
-                        "$ref": "#/rules@46"
+                        "$ref": "#/rules@49"
                       },
                       "arguments": []
                     }
@@ -2032,7 +2039,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 "terminal": {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@52"
+                    "$ref": "#/rules@55"
                   },
                   "arguments": []
                 }
@@ -2066,7 +2073,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@66"
+                "$ref": "#/rules@69"
               },
               "arguments": []
             },
@@ -2079,7 +2086,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@47"
+                "$ref": "#/rules@50"
               },
               "arguments": []
             }
@@ -2103,7 +2110,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@51"
+                "$ref": "#/rules@54"
               },
               "arguments": []
             },
@@ -2134,7 +2141,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 "terminal": {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@57"
+                    "$ref": "#/rules@60"
                   },
                   "arguments": []
                 }
@@ -2146,7 +2153,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 "terminal": {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@40"
+                    "$ref": "#/rules@43"
                   },
                   "arguments": []
                 }
@@ -2163,7 +2170,217 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                   "terminal": {
                     "$type": "RuleCall",
                     "rule": {
-                      "$ref": "#/rules@46"
+                      "$ref": "#/rules@49"
+                    },
+                    "arguments": []
+                  },
+                  "deprecatedSyntax": false
+                }
+              }
+            ]
+          },
+          {
+            "$type": "Group",
+            "elements": [
+              {
+                "$type": "Assignment",
+                "feature": "array",
+                "operator": "?=",
+                "terminal": {
+                  "$type": "Keyword",
+                  "value": "["
+                }
+              },
+              {
+                "$type": "Keyword",
+                "value": "]"
+              }
+            ],
+            "cardinality": "?"
+          },
+          {
+            "$type": "Assignment",
+            "feature": "optional",
+            "operator": "?=",
+            "terminal": {
+              "$type": "Keyword",
+              "value": "?"
+            },
+            "cardinality": "?"
+          }
+        ]
+      },
+      "definesHiddenTokens": false,
+      "entry": false,
+      "fragment": false,
+      "hiddenTokens": [],
+      "parameters": [],
+      "wildcard": false
+    },
+    {
+      "$type": "ParserRule",
+      "name": "TypeDef",
+      "definition": {
+        "$type": "Group",
+        "elements": [
+          {
+            "$type": "Assignment",
+            "feature": "comments",
+            "operator": "+=",
+            "terminal": {
+              "$type": "RuleCall",
+              "rule": {
+                "$ref": "#/rules@69"
+              },
+              "arguments": []
+            },
+            "cardinality": "*"
+          },
+          {
+            "$type": "Keyword",
+            "value": "type"
+          },
+          {
+            "$type": "Assignment",
+            "feature": "name",
+            "operator": "=",
+            "terminal": {
+              "$type": "RuleCall",
+              "rule": {
+                "$ref": "#/rules@49"
+              },
+              "arguments": []
+            }
+          },
+          {
+            "$type": "Keyword",
+            "value": "{"
+          },
+          {
+            "$type": "Assignment",
+            "feature": "fields",
+            "operator": "+=",
+            "terminal": {
+              "$type": "RuleCall",
+              "rule": {
+                "$ref": "#/rules@41"
+              },
+              "arguments": []
+            },
+            "cardinality": "+"
+          },
+          {
+            "$type": "Keyword",
+            "value": "}"
+          }
+        ]
+      },
+      "definesHiddenTokens": false,
+      "entry": false,
+      "fragment": false,
+      "hiddenTokens": [],
+      "parameters": [],
+      "wildcard": false
+    },
+    {
+      "$type": "ParserRule",
+      "name": "TypeDefField",
+      "definition": {
+        "$type": "Group",
+        "elements": [
+          {
+            "$type": "Assignment",
+            "feature": "comments",
+            "operator": "+=",
+            "terminal": {
+              "$type": "RuleCall",
+              "rule": {
+                "$ref": "#/rules@69"
+              },
+              "arguments": []
+            },
+            "cardinality": "*"
+          },
+          {
+            "$type": "Assignment",
+            "feature": "name",
+            "operator": "=",
+            "terminal": {
+              "$type": "RuleCall",
+              "rule": {
+                "$ref": "#/rules@50"
+              },
+              "arguments": []
+            }
+          },
+          {
+            "$type": "Assignment",
+            "feature": "type",
+            "operator": "=",
+            "terminal": {
+              "$type": "RuleCall",
+              "rule": {
+                "$ref": "#/rules@42"
+              },
+              "arguments": []
+            }
+          },
+          {
+            "$type": "Assignment",
+            "feature": "attributes",
+            "operator": "+=",
+            "terminal": {
+              "$type": "RuleCall",
+              "rule": {
+                "$ref": "#/rules@54"
+              },
+              "arguments": []
+            },
+            "cardinality": "*"
+          }
+        ]
+      },
+      "definesHiddenTokens": false,
+      "entry": false,
+      "fragment": false,
+      "hiddenTokens": [],
+      "parameters": [],
+      "wildcard": false
+    },
+    {
+      "$type": "ParserRule",
+      "name": "TypeDefFieldType",
+      "definition": {
+        "$type": "Group",
+        "elements": [
+          {
+            "$type": "Alternatives",
+            "elements": [
+              {
+                "$type": "Assignment",
+                "feature": "type",
+                "operator": "=",
+                "terminal": {
+                  "$type": "RuleCall",
+                  "rule": {
+                    "$ref": "#/rules@60"
+                  },
+                  "arguments": []
+                }
+              },
+              {
+                "$type": "Assignment",
+                "feature": "reference",
+                "operator": "=",
+                "terminal": {
+                  "$type": "CrossReference",
+                  "type": {
+                    "$ref": "#/rules@40"
+                  },
+                  "terminal": {
+                    "$type": "RuleCall",
+                    "rule": {
+                      "$ref": "#/rules@49"
                     },
                     "arguments": []
                   },
@@ -2262,7 +2479,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@66"
+                "$ref": "#/rules@69"
               },
               "arguments": []
             },
@@ -2279,7 +2496,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@46"
+                "$ref": "#/rules@49"
               },
               "arguments": []
             }
@@ -2298,7 +2515,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 "terminal": {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@42"
+                    "$ref": "#/rules@45"
                   },
                   "arguments": []
                 }
@@ -2310,7 +2527,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 "terminal": {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@52"
+                    "$ref": "#/rules@55"
                   },
                   "arguments": []
                 }
@@ -2344,7 +2561,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@66"
+                "$ref": "#/rules@69"
               },
               "arguments": []
             },
@@ -2357,7 +2574,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@47"
+                "$ref": "#/rules@50"
               },
               "arguments": []
             }
@@ -2369,7 +2586,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@51"
+                "$ref": "#/rules@54"
               },
               "arguments": []
             },
@@ -2393,7 +2610,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@66"
+              "$ref": "#/rules@69"
             },
             "arguments": [],
             "cardinality": "*"
@@ -2409,7 +2626,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@46"
+                "$ref": "#/rules@49"
               },
               "arguments": []
             }
@@ -2428,7 +2645,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 "terminal": {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@44"
+                    "$ref": "#/rules@47"
                   },
                   "arguments": []
                 }
@@ -2447,7 +2664,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                     "terminal": {
                       "$type": "RuleCall",
                       "rule": {
-                        "$ref": "#/rules@44"
+                        "$ref": "#/rules@47"
                       },
                       "arguments": []
                     }
@@ -2473,7 +2690,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@45"
+                "$ref": "#/rules@48"
               },
               "arguments": []
             }
@@ -2506,7 +2723,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@53"
+                "$ref": "#/rules@56"
               },
               "arguments": []
             },
@@ -2530,7 +2747,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@66"
+              "$ref": "#/rules@69"
             },
             "arguments": [],
             "cardinality": "*"
@@ -2542,7 +2759,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@46"
+                "$ref": "#/rules@49"
               },
               "arguments": []
             }
@@ -2558,7 +2775,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@45"
+                "$ref": "#/rules@48"
               },
               "arguments": []
             }
@@ -2598,7 +2815,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 "terminal": {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@56"
+                    "$ref": "#/rules@59"
                   },
                   "arguments": []
                 }
@@ -2615,7 +2832,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                   "terminal": {
                     "$type": "RuleCall",
                     "rule": {
-                      "$ref": "#/rules@46"
+                      "$ref": "#/rules@49"
                     },
                     "arguments": []
                   },
@@ -2662,7 +2879,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@63"
+              "$ref": "#/rules@66"
             },
             "arguments": []
           },
@@ -2701,6 +2918,10 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "Keyword",
             "value": "import"
+          },
+          {
+            "$type": "Keyword",
+            "value": "type"
           }
         ]
       },
@@ -2721,7 +2942,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@46"
+              "$ref": "#/rules@49"
             },
             "arguments": []
           },
@@ -2799,7 +3020,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@66"
+                "$ref": "#/rules@69"
               },
               "arguments": []
             },
@@ -2819,21 +3040,21 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@60"
+                    "$ref": "#/rules@63"
                   },
                   "arguments": []
                 },
                 {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@61"
+                    "$ref": "#/rules@64"
                   },
                   "arguments": []
                 },
                 {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@62"
+                    "$ref": "#/rules@65"
                   },
                   "arguments": []
                 }
@@ -2854,7 +3075,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 "terminal": {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@49"
+                    "$ref": "#/rules@52"
                   },
                   "arguments": []
                 }
@@ -2873,7 +3094,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                     "terminal": {
                       "$type": "RuleCall",
                       "rule": {
-                        "$ref": "#/rules@49"
+                        "$ref": "#/rules@52"
                       },
                       "arguments": []
                     }
@@ -2895,7 +3116,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@53"
+                "$ref": "#/rules@56"
               },
               "arguments": []
             },
@@ -2923,7 +3144,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@66"
+                "$ref": "#/rules@69"
               },
               "arguments": []
             },
@@ -2946,7 +3167,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@46"
+                "$ref": "#/rules@49"
               },
               "arguments": []
             }
@@ -2962,7 +3183,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@50"
+                "$ref": "#/rules@53"
               },
               "arguments": []
             }
@@ -2974,7 +3195,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@53"
+                "$ref": "#/rules@56"
               },
               "arguments": []
             },
@@ -3008,7 +3229,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                     {
                       "$type": "RuleCall",
                       "rule": {
-                        "$ref": "#/rules@56"
+                        "$ref": "#/rules@59"
                       },
                       "arguments": []
                     },
@@ -3039,7 +3260,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                   "terminal": {
                     "$type": "RuleCall",
                     "rule": {
-                      "$ref": "#/rules@46"
+                      "$ref": "#/rules@49"
                     },
                     "arguments": []
                   },
@@ -3099,12 +3320,12 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "CrossReference",
               "type": {
-                "$ref": "#/rules@48"
+                "$ref": "#/rules@51"
               },
               "terminal": {
                 "$type": "RuleCall",
                 "rule": {
-                  "$ref": "#/rules@62"
+                  "$ref": "#/rules@65"
                 },
                 "arguments": []
               },
@@ -3121,7 +3342,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
               {
                 "$type": "RuleCall",
                 "rule": {
-                  "$ref": "#/rules@54"
+                  "$ref": "#/rules@57"
                 },
                 "arguments": [],
                 "cardinality": "?"
@@ -3151,7 +3372,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "RuleCall",
             "rule": {
-              "$ref": "#/rules@66"
+              "$ref": "#/rules@69"
             },
             "arguments": [],
             "cardinality": "*"
@@ -3163,12 +3384,12 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "CrossReference",
               "type": {
-                "$ref": "#/rules@48"
+                "$ref": "#/rules@51"
               },
               "terminal": {
                 "$type": "RuleCall",
                 "rule": {
-                  "$ref": "#/rules@61"
+                  "$ref": "#/rules@64"
                 },
                 "arguments": []
               },
@@ -3185,7 +3406,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
               {
                 "$type": "RuleCall",
                 "rule": {
-                  "$ref": "#/rules@54"
+                  "$ref": "#/rules@57"
                 },
                 "arguments": [],
                 "cardinality": "?"
@@ -3219,12 +3440,12 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "CrossReference",
               "type": {
-                "$ref": "#/rules@48"
+                "$ref": "#/rules@51"
               },
               "terminal": {
                 "$type": "RuleCall",
                 "rule": {
-                  "$ref": "#/rules@60"
+                  "$ref": "#/rules@63"
                 },
                 "arguments": []
               },
@@ -3241,7 +3462,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
               {
                 "$type": "RuleCall",
                 "rule": {
-                  "$ref": "#/rules@54"
+                  "$ref": "#/rules@57"
                 },
                 "arguments": [],
                 "cardinality": "?"
@@ -3276,7 +3497,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
             "terminal": {
               "$type": "RuleCall",
               "rule": {
-                "$ref": "#/rules@55"
+                "$ref": "#/rules@58"
               },
               "arguments": []
             }
@@ -3295,7 +3516,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 "terminal": {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@55"
+                    "$ref": "#/rules@58"
                   },
                   "arguments": []
                 }
@@ -3327,7 +3548,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
                 "terminal": {
                   "$type": "RuleCall",
                   "rule": {
-                    "$ref": "#/rules@46"
+                    "$ref": "#/rules@49"
                   },
                   "arguments": []
                 }
@@ -3599,7 +3820,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "SimpleType",
             "typeRef": {
-              "$ref": "#/rules@44"
+              "$ref": "#/rules@47"
             }
           },
           {
@@ -3611,7 +3832,7 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "SimpleType",
             "typeRef": {
-              "$ref": "#/rules@42"
+              "$ref": "#/rules@45"
             }
           }
         ]
@@ -3632,7 +3853,13 @@ export const ZModelGrammar = (): Grammar => loadedZModelGrammar ?? (loadedZModel
           {
             "$type": "SimpleType",
             "typeRef": {
-              "$ref": "#/rules@41"
+              "$ref": "#/rules@40"
+            }
+          },
+          {
+            "$type": "SimpleType",
+            "typeRef": {
+              "$ref": "#/rules@44"
             }
           }
         ]
diff --git a/packages/language/src/zmodel.langium b/packages/language/src/zmodel.langium
index 4f12159d6..d66ea5f32 100644
--- a/packages/language/src/zmodel.langium
+++ b/packages/language/src/zmodel.langium
@@ -11,7 +11,7 @@ ModelImport:
     'import' path=STRING  ';'?;
 
 AbstractDeclaration:
-    DataSource | GeneratorDecl| Plugin | DataModel | Enum | FunctionDecl | Attribute;
+    DataSource | GeneratorDecl| Plugin | DataModel | TypeDef | Enum | FunctionDecl | Attribute;
 
 // datasource
 DataSource:
@@ -113,22 +113,6 @@ CollectionPredicateExpr infers Expression:
         '[' right=Expression ']'
     )*;
 
-// TODO: support arithmetics?
-//
-// MultDivExpr infers Expression:
-//     CollectionPredicateExpr (
-//         {infer BinaryExpr.left=current}
-//         operator=('*'|'/')
-//         right=CollectionPredicateExpr
-//     )*;
-
-// AddSubExpr infers Expression:
-//     MultDivExpr (
-//         {infer BinaryExpr.left=current}
-//         operator=('+'|'-')
-//         right=MultDivExpr
-//     )*;
-
 InExpr infers Expression:
     CollectionPredicateExpr (
         {infer BinaryExpr.left=current}
@@ -195,6 +179,20 @@ DataModelField:
 DataModelFieldType:
     (type=BuiltinType | unsupported=UnsupportedFieldType | reference=[TypeDeclaration:RegularID]) (array?='[' ']')? (optional?='?')?;
 
+TypeDef:
+    (comments+=TRIPLE_SLASH_COMMENT)*
+    'type' name=RegularID '{' (
+           fields+=TypeDefField
+        )+
+    '}';
+
+TypeDefField:
+    (comments+=TRIPLE_SLASH_COMMENT)*
+    name=RegularIDWithTypeNames type=TypeDefFieldType (attributes+=DataModelFieldAttribute)*;
+
+TypeDefFieldType:
+    (type=BuiltinType | reference=[TypeDef:RegularID]) (array?='[' ']')? (optional?='?')?;
+
 UnsupportedFieldType:
     'Unsupported' '(' (value=LiteralExpr) ')';
 
@@ -224,7 +222,7 @@ FunctionParamType:
 // https://github.com/langium/langium/discussions/1012
 RegularID returns string:
     // include keywords that we'd like to work as ID in most places
-    ID | 'model' | 'enum' | 'attribute' | 'datasource' | 'plugin' | 'abstract' | 'in' | 'view' | 'import';
+    ID | 'model' | 'enum' | 'attribute' | 'datasource' | 'plugin' | 'abstract' | 'in' | 'view' | 'import' | 'type';
 
 RegularIDWithTypeNames returns string:
     RegularID | 'String' | 'Boolean' | 'Int' | 'BigInt' | 'Float' | 'Decimal' | 'DateTime' | 'Json' | 'Bytes' | 'Null' | 'Object' | 'Any' | 'Unsupported';
@@ -241,7 +239,7 @@ AttributeParam:
 AttributeParamType:
     (type=(ExpressionType | 'FieldReference' | 'TransitiveFieldReference' | 'ContextType') | reference=[TypeDeclaration:RegularID]) (array?='[' ']')? (optional?='?')?;
 
-type TypeDeclaration = DataModel | Enum;
+type TypeDeclaration = DataModel | TypeDef | Enum;
 DataModelFieldAttribute:
     decl=[Attribute:FIELD_ATTRIBUTE_NAME] ('(' AttributeArgList? ')')?;
 
diff --git a/packages/language/syntaxes/zmodel.tmLanguage b/packages/language/syntaxes/zmodel.tmLanguage
index 6102b919d..40b92fb9a 100644
--- a/packages/language/syntaxes/zmodel.tmLanguage
+++ b/packages/language/syntaxes/zmodel.tmLanguage
@@ -20,7 +20,7 @@
         <key>name</key>
         <string>keyword.control.zmodel</string>
         <key>match</key>
-        <string>\b(Any|BigInt|Boolean|Bytes|ContextType|DateTime|Decimal|FieldReference|Float|Int|Json|Null|Object|String|TransitiveFieldReference|Unsupported|abstract|attribute|datasource|enum|extends|false|function|generator|import|in|model|null|plugin|this|true|view)\b</string>
+        <string>\b(Any|BigInt|Boolean|Bytes|ContextType|DateTime|Decimal|FieldReference|Float|Int|Json|Null|Object|String|TransitiveFieldReference|Unsupported|abstract|attribute|datasource|enum|extends|false|function|generator|import|in|model|null|plugin|this|true|type|view)\b</string>
       </dict>
       <dict>
         <key>name</key>
diff --git a/packages/language/syntaxes/zmodel.tmLanguage.json b/packages/language/syntaxes/zmodel.tmLanguage.json
index aad6a38c7..0fb0227e5 100644
--- a/packages/language/syntaxes/zmodel.tmLanguage.json
+++ b/packages/language/syntaxes/zmodel.tmLanguage.json
@@ -10,7 +10,7 @@
     },
     {
       "name": "keyword.control.zmodel",
-      "match": "\\b(Any|BigInt|Boolean|Bytes|ContextType|DateTime|Decimal|FieldReference|Float|Int|Json|Null|Object|String|TransitiveFieldReference|Unsupported|abstract|attribute|datasource|enum|extends|false|function|generator|import|in|model|null|plugin|this|true|view)\\b"
+      "match": "\\b(Any|BigInt|Boolean|Bytes|ContextType|DateTime|Decimal|FieldReference|Float|Int|Json|Null|Object|String|TransitiveFieldReference|Unsupported|abstract|attribute|datasource|enum|extends|false|function|generator|import|in|model|null|plugin|this|true|type|view)\\b"
     },
     {
       "name": "string.quoted.double.zmodel",
diff --git a/packages/plugins/swr/src/generator.ts b/packages/plugins/swr/src/generator.ts
index 46d18d296..967be9727 100644
--- a/packages/plugins/swr/src/generator.ts
+++ b/packages/plugins/swr/src/generator.ts
@@ -10,7 +10,7 @@ import {
     resolvePath,
     saveProject,
 } from '@zenstackhq/sdk';
-import { DataModel, DataModelFieldType, Model, isEnum } from '@zenstackhq/sdk/ast';
+import { DataModel, DataModelFieldType, Model, isEnum, isTypeDef } from '@zenstackhq/sdk/ast';
 import { getPrismaClientImportSpec, supportCreateMany, type DMMF } from '@zenstackhq/sdk/prisma';
 import { paramCase } from 'change-case';
 import path from 'path';
@@ -28,8 +28,9 @@ export async function generate(model: Model, options: PluginOptions, dmmf: DMMF.
     const warnings: string[] = [];
 
     const models = getDataModels(model);
+    const typeDefs = model.declarations.filter(isTypeDef);
 
-    await generateModelMeta(project, models, {
+    await generateModelMeta(project, models, typeDefs, {
         output: path.join(outDir, '__model_meta.ts'),
         generateAttributes: false,
     });
diff --git a/packages/plugins/tanstack-query/src/generator.ts b/packages/plugins/tanstack-query/src/generator.ts
index afb86f9c7..8833f77f9 100644
--- a/packages/plugins/tanstack-query/src/generator.ts
+++ b/packages/plugins/tanstack-query/src/generator.ts
@@ -11,7 +11,7 @@ import {
     resolvePath,
     saveProject,
 } from '@zenstackhq/sdk';
-import { DataModel, DataModelFieldType, Model, isEnum } from '@zenstackhq/sdk/ast';
+import { DataModel, DataModelFieldType, Model, isEnum, isTypeDef } from '@zenstackhq/sdk/ast';
 import { getPrismaClientImportSpec, supportCreateMany, type DMMF } from '@zenstackhq/sdk/prisma';
 import { paramCase } from 'change-case';
 import { lowerCaseFirst } from 'lower-case-first';
@@ -29,6 +29,7 @@ export async function generate(model: Model, options: PluginOptions, dmmf: DMMF.
     const project = createProject();
     const warnings: string[] = [];
     const models = getDataModels(model);
+    const typeDefs = model.declarations.filter(isTypeDef);
 
     const target = requireOption<string>(options, 'target', name);
     if (!supportedTargets.includes(target)) {
@@ -44,7 +45,7 @@ export async function generate(model: Model, options: PluginOptions, dmmf: DMMF.
     outDir = resolvePath(outDir, options);
     ensureEmptyDir(outDir);
 
-    await generateModelMeta(project, models, {
+    await generateModelMeta(project, models, typeDefs, {
         output: path.join(outDir, '__model_meta.ts'),
         generateAttributes: false,
     });
diff --git a/packages/runtime/src/cross/model-meta.ts b/packages/runtime/src/cross/model-meta.ts
index 3eb6b3786..3b27f1686 100644
--- a/packages/runtime/src/cross/model-meta.ts
+++ b/packages/runtime/src/cross/model-meta.ts
@@ -44,6 +44,11 @@ export type FieldInfo = {
      */
     isDataModel?: boolean;
 
+    /**
+     * If the field type is a type def (or an optional/array of type def)
+     */
+    isTypeDef?: boolean;
+
     /**
      * If the field is an array
      */
@@ -143,6 +148,21 @@ export type ModelInfo = {
     discriminator?: string;
 };
 
+/**
+ * Metadata for a type def
+ */
+export type TypeDefInfo = {
+    /**
+     * TypeDef name
+     */
+    name: string;
+
+    /**
+     * Fields
+     */
+    fields: Record<string, FieldInfo>;
+};
+
 /**
  * ZModel data model metadata
  */
@@ -152,6 +172,11 @@ export type ModelMeta = {
      */
     models: Record<string, ModelInfo>;
 
+    /**
+     * Type defs
+     */
+    typeDefs?: Record<string, TypeDefInfo>;
+
     /**
      * Mapping from model name to models that will be deleted because of it due to cascade delete
      */
@@ -171,15 +196,21 @@ export type ModelMeta = {
 /**
  * Resolves a model field to its metadata. Returns undefined if not found.
  */
-export function resolveField(modelMeta: ModelMeta, model: string, field: string): FieldInfo | undefined {
-    return modelMeta.models[lowerCaseFirst(model)]?.fields?.[field];
+export function resolveField(
+    modelMeta: ModelMeta,
+    modelOrTypeDef: string,
+    field: string,
+    isTypeDef = false
+): FieldInfo | undefined {
+    const container = isTypeDef ? modelMeta.typeDefs : modelMeta.models;
+    return container?.[lowerCaseFirst(modelOrTypeDef)]?.fields?.[field];
 }
 
 /**
  * Resolves a model field to its metadata. Throws an error if not found.
  */
-export function requireField(modelMeta: ModelMeta, model: string, field: string) {
-    const f = resolveField(modelMeta, model, field);
+export function requireField(modelMeta: ModelMeta, model: string, field: string, isTypeDef = false) {
+    const f = resolveField(modelMeta, model, field, isTypeDef);
     if (!f) {
         throw new Error(`Field ${model}.${field} cannot be resolved`);
     }
diff --git a/packages/runtime/src/cross/utils.ts b/packages/runtime/src/cross/utils.ts
index 304b9b618..b1cb67e12 100644
--- a/packages/runtime/src/cross/utils.ts
+++ b/packages/runtime/src/cross/utils.ts
@@ -1,5 +1,5 @@
 import { lowerCaseFirst } from 'lower-case-first';
-import { requireField, type ModelInfo, type ModelMeta } from '.';
+import { requireField, type ModelInfo, type ModelMeta, type TypeDefInfo } from '.';
 
 /**
  * Gets field names in a data model entity, filtering out internal fields.
@@ -46,6 +46,9 @@ export function zip<T1, T2>(x: Enumerable<T1>, y: Enumerable<T2>): Array<[T1, T2
     }
 }
 
+/**
+ * Gets ID fields of a model.
+ */
 export function getIdFields(modelMeta: ModelMeta, model: string, throwIfNotFound = false) {
     const uniqueConstraints = modelMeta.models[lowerCaseFirst(model)]?.uniqueConstraints ?? {};
 
@@ -60,6 +63,9 @@ export function getIdFields(modelMeta: ModelMeta, model: string, throwIfNotFound
     return entries[0].fields.map((f) => requireField(modelMeta, model, f));
 }
 
+/**
+ * Gets info for a model.
+ */
 export function getModelInfo<Throw extends boolean = false>(
     modelMeta: ModelMeta,
     model: string,
@@ -72,6 +78,25 @@ export function getModelInfo<Throw extends boolean = false>(
     return info;
 }
 
+/**
+ * Gets info for a type def.
+ */
+export function getTypeDefInfo<Throw extends boolean = false>(
+    modelMeta: ModelMeta,
+    typeDef: string,
+    throwIfNotFound: Throw = false as Throw
+): Throw extends true ? TypeDefInfo : TypeDefInfo | undefined {
+    const info = modelMeta.typeDefs?.[lowerCaseFirst(typeDef)];
+    if (!info && throwIfNotFound) {
+        throw new Error(`Unable to load info for ${typeDef}`);
+    }
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    return info as any;
+}
+
+/**
+ * Checks if a model is a delegate model.
+ */
 export function isDelegateModel(modelMeta: ModelMeta, model: string) {
     return !!getModelInfo(modelMeta, model)?.attributes?.some((attr) => attr.name === '@@delegate');
 }
diff --git a/packages/runtime/src/enhancements/edge/json-processor.ts b/packages/runtime/src/enhancements/edge/json-processor.ts
new file mode 120000
index 000000000..4144fc6f4
--- /dev/null
+++ b/packages/runtime/src/enhancements/edge/json-processor.ts
@@ -0,0 +1 @@
+../node/json-processor.ts
\ No newline at end of file
diff --git a/packages/runtime/src/enhancements/node/create-enhancement.ts b/packages/runtime/src/enhancements/node/create-enhancement.ts
index 263e12192..adec1fdf2 100644
--- a/packages/runtime/src/enhancements/node/create-enhancement.ts
+++ b/packages/runtime/src/enhancements/node/create-enhancement.ts
@@ -10,6 +10,7 @@ import type {
 } from '../../types';
 import { withDefaultAuth } from './default-auth';
 import { withDelegate } from './delegate';
+import { withJsonProcessor } from './json-processor';
 import { Logger } from './logger';
 import { withOmit } from './omit';
 import { withPassword } from './password';
@@ -90,10 +91,18 @@ export function createEnhancement<DbClient extends object>(
 
     // TODO: move the detection logic into each enhancement
     // TODO: how to properly cache the detection result?
+
     const allFields = Object.values(options.modelMeta.models).flatMap((modelInfo) => Object.values(modelInfo.fields));
+    if (options.modelMeta.typeDefs) {
+        allFields.push(
+            ...Object.values(options.modelMeta.typeDefs).flatMap((typeDefInfo) => Object.values(typeDefInfo.fields))
+        );
+    }
+
     const hasPassword = allFields.some((field) => field.attributes?.some((attr) => attr.name === '@password'));
     const hasOmit = allFields.some((field) => field.attributes?.some((attr) => attr.name === '@omit'));
     const hasDefaultAuth = allFields.some((field) => field.defaultValueProvider);
+    const hasTypeDefField = allFields.some((field) => field.isTypeDef);
 
     const kinds = options.kinds ?? ALL_ENHANCEMENTS;
     let result = prisma;
@@ -142,5 +151,9 @@ export function createEnhancement<DbClient extends object>(
         result = withOmit(result, options);
     }
 
+    if (hasTypeDefField) {
+        result = withJsonProcessor(result, options);
+    }
+
     return result;
 }
diff --git a/packages/runtime/src/enhancements/node/default-auth.ts b/packages/runtime/src/enhancements/node/default-auth.ts
index 3852069c8..03ce3750c 100644
--- a/packages/runtime/src/enhancements/node/default-auth.ts
+++ b/packages/runtime/src/enhancements/node/default-auth.ts
@@ -8,6 +8,7 @@ import {
     clone,
     enumerate,
     getFields,
+    getTypeDefInfo,
     requireField,
 } from '../../cross';
 import { DbClientContract, EnhancementContext } from '../../types';
@@ -70,6 +71,11 @@ class DefaultAuthHandler extends DefaultPrismaProxyHandler {
         const processCreatePayload = (model: string, data: any) => {
             const fields = getFields(this.options.modelMeta, model);
             for (const fieldInfo of Object.values(fields)) {
+                if (fieldInfo.isTypeDef) {
+                    this.setDefaultValueForTypeDefData(fieldInfo.type, data[fieldInfo.name]);
+                    continue;
+                }
+
                 if (fieldInfo.name in data) {
                     // create payload already sets field value
                     continue;
@@ -80,10 +86,10 @@ class DefaultAuthHandler extends DefaultPrismaProxyHandler {
                     continue;
                 }
 
-                const authDefaultValue = this.getDefaultValueFromAuth(fieldInfo);
-                if (authDefaultValue !== undefined) {
+                const defaultValue = this.getDefaultValue(fieldInfo);
+                if (defaultValue !== undefined) {
                     // set field value extracted from `auth()`
-                    this.setAuthDefaultValue(fieldInfo, model, data, authDefaultValue);
+                    this.setDefaultValueForModelData(fieldInfo, model, data, defaultValue);
                 }
             }
         };
@@ -109,7 +115,7 @@ class DefaultAuthHandler extends DefaultPrismaProxyHandler {
         return newArgs;
     }
 
-    private setAuthDefaultValue(fieldInfo: FieldInfo, model: string, data: any, authDefaultValue: unknown) {
+    private setDefaultValueForModelData(fieldInfo: FieldInfo, model: string, data: any, authDefaultValue: unknown) {
         if (fieldInfo.isForeignKey && fieldInfo.relationField && fieldInfo.relationField in data) {
             // if the field is a fk, and the relation field is already set, we should not override it
             return;
@@ -155,7 +161,7 @@ class DefaultAuthHandler extends DefaultPrismaProxyHandler {
         return entry?.[0];
     }
 
-    private getDefaultValueFromAuth(fieldInfo: FieldInfo) {
+    private getDefaultValue(fieldInfo: FieldInfo) {
         if (!this.userContext) {
             throw prismaClientValidationError(
                 this.prisma,
@@ -165,4 +171,34 @@ class DefaultAuthHandler extends DefaultPrismaProxyHandler {
         }
         return fieldInfo.defaultValueProvider?.(this.userContext);
     }
+
+    private setDefaultValueForTypeDefData(type: string, data: any) {
+        if (!data || (typeof data !== 'object' && !Array.isArray(data))) {
+            return;
+        }
+
+        const typeDef = getTypeDefInfo(this.options.modelMeta, type);
+        if (!typeDef) {
+            return;
+        }
+
+        enumerate(data).forEach((item) => {
+            if (!item || typeof item !== 'object') {
+                return;
+            }
+
+            for (const fieldInfo of Object.values(typeDef.fields)) {
+                if (fieldInfo.isTypeDef) {
+                    // recurse
+                    this.setDefaultValueForTypeDefData(fieldInfo.type, item[fieldInfo.name]);
+                } else if (!(fieldInfo.name in item)) {
+                    // set default value if the payload doesn't set the field
+                    const defaultValue = this.getDefaultValue(fieldInfo);
+                    if (defaultValue !== undefined) {
+                        item[fieldInfo.name] = defaultValue;
+                    }
+                }
+            }
+        });
+    }
 }
diff --git a/packages/runtime/src/enhancements/node/json-processor.ts b/packages/runtime/src/enhancements/node/json-processor.ts
new file mode 100644
index 000000000..6cf204a6f
--- /dev/null
+++ b/packages/runtime/src/enhancements/node/json-processor.ts
@@ -0,0 +1,92 @@
+/* eslint-disable @typescript-eslint/no-explicit-any */
+import { enumerate, getModelFields, resolveField } from '../../cross';
+import { DbClientContract } from '../../types';
+import { InternalEnhancementOptions } from './create-enhancement';
+import { DefaultPrismaProxyHandler, makeProxy, PrismaProxyActions } from './proxy';
+import { QueryUtils } from './query-utils';
+
+/**
+ * Gets an enhanced Prisma client that post-processes JSON values.
+ *
+ * @private
+ */
+export function withJsonProcessor<DbClient extends object = any>(
+    prisma: DbClient,
+    options: InternalEnhancementOptions
+): DbClient {
+    return makeProxy(
+        prisma,
+        options.modelMeta,
+        (_prisma, model) => new JsonProcessorHandler(_prisma as DbClientContract, model, options),
+        'json-processor'
+    );
+}
+
+class JsonProcessorHandler extends DefaultPrismaProxyHandler {
+    private queryUtils: QueryUtils;
+
+    constructor(prisma: DbClientContract, model: string, options: InternalEnhancementOptions) {
+        super(prisma, model, options);
+        this.queryUtils = new QueryUtils(prisma, options);
+    }
+
+    protected override async processResultEntity<T>(_method: PrismaProxyActions, data: T): Promise<T> {
+        for (const value of enumerate(data)) {
+            await this.doPostProcess(value, this.model);
+        }
+        return data;
+    }
+
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    private async doPostProcess(entityData: any, model: string) {
+        const realModel = this.queryUtils.getDelegateConcreteModel(model, entityData);
+
+        for (const field of getModelFields(entityData)) {
+            const fieldInfo = await resolveField(this.options.modelMeta, realModel, field);
+            if (!fieldInfo) {
+                continue;
+            }
+
+            if (fieldInfo.isTypeDef) {
+                this.fixJsonDateFields(entityData[field], fieldInfo.type);
+            } else if (fieldInfo.isDataModel) {
+                const items =
+                    fieldInfo.isArray && Array.isArray(entityData[field]) ? entityData[field] : [entityData[field]];
+                for (const item of items) {
+                    // recurse
+                    await this.doPostProcess(item, fieldInfo.type);
+                }
+            }
+        }
+    }
+
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    private fixJsonDateFields(entityData: any, typeDef: string) {
+        if (typeof entityData !== 'object' && !Array.isArray(entityData)) {
+            return;
+        }
+
+        enumerate(entityData).forEach((item) => {
+            if (!item || typeof item !== 'object') {
+                return;
+            }
+
+            for (const [key, value] of Object.entries(item)) {
+                const fieldInfo = resolveField(this.options.modelMeta, typeDef, key, true);
+                if (!fieldInfo) {
+                    continue;
+                }
+                if (fieldInfo.isTypeDef) {
+                    // recurse
+                    this.fixJsonDateFields(value, fieldInfo.type);
+                } else if (fieldInfo.type === 'DateTime' && typeof value === 'string') {
+                    // convert to Date
+                    const parsed = Date.parse(value);
+                    if (!isNaN(parsed)) {
+                        item[key] = new Date(parsed);
+                    }
+                }
+            }
+        });
+    }
+}
diff --git a/packages/schema/src/cli/plugin-runner.ts b/packages/schema/src/cli/plugin-runner.ts
index 2912bfb60..4158bd256 100644
--- a/packages/schema/src/cli/plugin-runner.ts
+++ b/packages/schema/src/cli/plugin-runner.ts
@@ -1,6 +1,6 @@
 /* eslint-disable @typescript-eslint/no-explicit-any */
 /* eslint-disable @typescript-eslint/no-var-requires */
-import { isPlugin, Model, Plugin } from '@zenstackhq/language/ast';
+import { DataModel, isPlugin, isTypeDef, Model, Plugin } from '@zenstackhq/language/ast';
 import {
     createProject,
     emitProject,
@@ -311,7 +311,11 @@ export class PluginRunner {
     }
 
     private hasValidation(schema: Model) {
-        return getDataModels(schema).some((model) => hasValidationAttributes(model));
+        return getDataModels(schema).some((model) => hasValidationAttributes(model) || this.hasTypeDefFields(model));
+    }
+
+    private hasTypeDefFields(model: DataModel) {
+        return model.fields.some((f) => isTypeDef(f.type.reference?.ref));
     }
 
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
diff --git a/packages/schema/src/language-server/validator/attribute-application-validator.ts b/packages/schema/src/language-server/validator/attribute-application-validator.ts
index 9ec2074be..2a7f43c29 100644
--- a/packages/schema/src/language-server/validator/attribute-application-validator.ts
+++ b/packages/schema/src/language-server/validator/attribute-application-validator.ts
@@ -14,8 +14,11 @@ import {
     isDataModelField,
     isEnum,
     isReferenceExpr,
+    isTypeDef,
+    isTypeDefField,
 } from '@zenstackhq/language/ast';
 import {
+    hasAttribute,
     isDataModelFieldReference,
     isDelegateModel,
     isFutureExpr,
@@ -62,6 +65,10 @@ export default class AttributeApplicationValidator implements AstValidator<Attri
             accept('error', `attribute "${decl.name}" cannot be used on this type of field`, { node: attr });
         }
 
+        if (isTypeDefField(targetDecl) && !hasAttribute(decl, '@@@supportTypeDef')) {
+            accept('error', `attribute "${decl.name}" cannot be used on type declaration fields`, { node: attr });
+        }
+
         const filledParams = new Set<AttributeParam>();
 
         for (const arg of attr.args) {
@@ -345,6 +352,9 @@ function isValidAttributeTarget(attrDecl: Attribute, targetDecl: DataModelField)
             case 'ModelField':
                 allowed = allowed || isDataModel(targetDecl.type.reference?.ref);
                 break;
+            case 'TypeDefField':
+                allowed = allowed || isTypeDef(targetDecl.type.reference?.ref);
+                break;
             default:
                 break;
         }
diff --git a/packages/schema/src/language-server/validator/datamodel-validator.ts b/packages/schema/src/language-server/validator/datamodel-validator.ts
index e463f740f..f2a3d6737 100644
--- a/packages/schema/src/language-server/validator/datamodel-validator.ts
+++ b/packages/schema/src/language-server/validator/datamodel-validator.ts
@@ -6,8 +6,16 @@ import {
     isDataModel,
     isEnum,
     isStringLiteral,
+    isTypeDef,
 } from '@zenstackhq/language/ast';
-import { getModelFieldsWithBases, getModelIdFields, getModelUniqueFields, isDelegateModel } from '@zenstackhq/sdk';
+import {
+    getDataSourceProvider,
+    getModelFieldsWithBases,
+    getModelIdFields,
+    getModelUniqueFields,
+    hasAttribute,
+    isDelegateModel,
+} from '@zenstackhq/sdk';
 import { AstNode, DiagnosticInfo, ValidationAcceptor, getDocument } from 'langium';
 import { findUpInheritance } from '../../utils/ast-utils';
 import { IssueCodes, SCALAR_TYPES } from '../constants';
@@ -95,6 +103,16 @@ export default class DataModelValidator implements AstValidator<DataModel> {
         }
 
         field.attributes.forEach((attr) => validateAttributeApplication(attr, accept));
+
+        if (isTypeDef(field.type.reference?.ref)) {
+            if (!hasAttribute(field, '@json')) {
+                accept('error', 'Custom-typed field must have @json attribute', { node: field });
+            }
+
+            if (getDataSourceProvider(field.$container.$container) !== 'postgresql') {
+                accept('error', 'Custom-typed field is only supported with "postgresql" provider', { node: field });
+            }
+        }
     }
 
     private validateAttributes(dm: DataModel, accept: ValidationAcceptor) {
diff --git a/packages/schema/src/language-server/validator/typedef-validator.ts b/packages/schema/src/language-server/validator/typedef-validator.ts
new file mode 100644
index 000000000..55c127d7d
--- /dev/null
+++ b/packages/schema/src/language-server/validator/typedef-validator.ts
@@ -0,0 +1,23 @@
+import { TypeDef, TypeDefField } from '@zenstackhq/language/ast';
+import { ValidationAcceptor } from 'langium';
+import { AstValidator } from '../types';
+import { validateAttributeApplication } from './attribute-application-validator';
+import { validateDuplicatedDeclarations } from './utils';
+
+/**
+ * Validates type def declarations.
+ */
+export default class TypeDefValidator implements AstValidator<TypeDef> {
+    validate(typeDef: TypeDef, accept: ValidationAcceptor): void {
+        validateDuplicatedDeclarations(typeDef, typeDef.fields, accept);
+        this.validateFields(typeDef, accept);
+    }
+
+    private validateFields(typeDef: TypeDef, accept: ValidationAcceptor) {
+        typeDef.fields.forEach((field) => this.validateField(field, accept));
+    }
+
+    private validateField(field: TypeDefField, accept: ValidationAcceptor): void {
+        field.attributes.forEach((attr) => validateAttributeApplication(attr, accept));
+    }
+}
diff --git a/packages/schema/src/language-server/validator/zmodel-validator.ts b/packages/schema/src/language-server/validator/zmodel-validator.ts
index 493bc5f89..c1dcbb09e 100644
--- a/packages/schema/src/language-server/validator/zmodel-validator.ts
+++ b/packages/schema/src/language-server/validator/zmodel-validator.ts
@@ -7,6 +7,7 @@ import {
     FunctionDecl,
     InvocationExpr,
     Model,
+    TypeDef,
     ZModelAstType,
 } from '@zenstackhq/language/ast';
 import { AstNode, LangiumDocument, ValidationAcceptor, ValidationChecks, ValidationRegistry } from 'langium';
@@ -19,6 +20,7 @@ import ExpressionValidator from './expression-validator';
 import FunctionDeclValidator from './function-decl-validator';
 import FunctionInvocationValidator from './function-invocation-validator';
 import SchemaValidator from './schema-validator';
+import TypeDefValidator from './typedef-validator';
 
 /**
  * Registry for validation checks.
@@ -31,6 +33,7 @@ export class ZModelValidationRegistry extends ValidationRegistry {
             Model: validator.checkModel,
             DataSource: validator.checkDataSource,
             DataModel: validator.checkDataModel,
+            TypeDef: validator.checkTypeDef,
             Enum: validator.checkEnum,
             Attribute: validator.checkAttribute,
             Expression: validator.checkExpression,
@@ -73,6 +76,10 @@ export class ZModelValidator {
         this.shouldCheck(node) && new DataModelValidator().validate(node, accept);
     }
 
+    checkTypeDef(node: TypeDef, accept: ValidationAcceptor): void {
+        this.shouldCheck(node) && new TypeDefValidator().validate(node, accept);
+    }
+
     checkEnum(node: Enum, accept: ValidationAcceptor): void {
         this.shouldCheck(node) && new EnumValidator().validate(node, accept);
     }
diff --git a/packages/schema/src/plugins/enhancer/enhance/index.ts b/packages/schema/src/plugins/enhancer/enhance/index.ts
index 34cf26640..3230d72f9 100644
--- a/packages/schema/src/plugins/enhancer/enhance/index.ts
+++ b/packages/schema/src/plugins/enhancer/enhance/index.ts
@@ -19,6 +19,7 @@ import {
     isDataModel,
     isGeneratorDecl,
     isReferenceExpr,
+    isTypeDef,
     type Model,
 } from '@zenstackhq/sdk/ast';
 import { getDMMF, getPrismaClientImportSpec, getPrismaVersion, type DMMF } from '@zenstackhq/sdk/prisma';
@@ -45,6 +46,7 @@ import { PrismaSchemaGenerator } from '../../prisma/schema-generator';
 import { isDefaultWithAuth } from '../enhancer-utils';
 import { generateAuthType } from './auth-type-generator';
 import { generateCheckerType } from './checker-type-generator';
+import { generateTypeDefType } from './model-typedef-generator';
 
 // information of delegate models and their sub models
 type DelegateInfo = [DataModel, DataModel[]][];
@@ -60,35 +62,27 @@ export class EnhancerGenerator {
     ) {}
 
     async generate(): Promise<{ dmmf: DMMF.Document | undefined }> {
-        let logicalPrismaClientDir: string | undefined;
         let dmmf: DMMF.Document | undefined;
 
         const prismaImport = getPrismaClientImportSpec(this.outDir, this.options);
+        let prismaTypesFixed = false;
+        let resultPrismaImport = prismaImport;
 
-        if (this.needsLogicalClient()) {
-            // schema contains delegate models, need to generate a logical prisma schema
+        if (this.needsLogicalClient || this.needsPrismaClientTypeFixes) {
+            prismaTypesFixed = true;
+            resultPrismaImport = `${LOGICAL_CLIENT_GENERATION_PATH}/index-fixed`;
             const result = await this.generateLogicalPrisma();
-
-            logicalPrismaClientDir = LOGICAL_CLIENT_GENERATION_PATH;
             dmmf = result.dmmf;
-
-            // create a reexport of the logical prisma client
-            const prismaDts = this.project.createSourceFile(
-                path.join(this.outDir, 'models.d.ts'),
-                `export type * from '${logicalPrismaClientDir}/index-fixed';`,
-                { overwrite: true }
-            );
-            await prismaDts.save();
-        } else {
-            // just reexport the prisma client
-            const prismaDts = this.project.createSourceFile(
-                path.join(this.outDir, 'models.d.ts'),
-                `export type * from '${prismaImport}';`,
-                { overwrite: true }
-            );
-            await prismaDts.save();
         }
 
+        // reexport PrismaClient types (original or fixed)
+        const prismaDts = this.project.createSourceFile(
+            path.join(this.outDir, 'models.d.ts'),
+            `export type * from '${resultPrismaImport}';`,
+            { overwrite: true }
+        );
+        await prismaDts.save();
+
         const authModel = getAuthModel(getDataModels(this.model));
         const authTypes = authModel ? generateAuthType(this.model, authModel) : '';
         const authTypeParam = authModel ? `auth.${authModel.name}` : 'AuthUser';
@@ -112,8 +106,8 @@ ${
 }
 
 ${
-    logicalPrismaClientDir
-        ? this.createLogicalPrismaImports(prismaImport, logicalPrismaClientDir)
+    prismaTypesFixed
+        ? this.createLogicalPrismaImports(prismaImport, resultPrismaImport)
         : this.createSimplePrismaImports(prismaImport)
 }
 
@@ -122,7 +116,7 @@ ${authTypes}
 ${checkerTypes}
 
 ${
-    logicalPrismaClientDir
+    prismaTypesFixed
         ? this.createLogicalPrismaEnhanceFunction(authTypeParam)
         : this.createSimplePrismaEnhanceFunction(authTypeParam)
 }
@@ -185,11 +179,11 @@ export function enhance<DbClient extends object>(prisma: DbClient, context?: Enh
             `;
     }
 
-    private createLogicalPrismaImports(prismaImport: string, logicalPrismaClientDir: string) {
+    private createLogicalPrismaImports(prismaImport: string, prismaClientImport: string) {
         return `import { Prisma as _Prisma, PrismaClient as _PrismaClient } from '${prismaImport}';
 import type { InternalArgs, DynamicClientExtensionThis } from '${prismaImport}/runtime/library';
-import type * as _P from '${logicalPrismaClientDir}/index-fixed';
-import type { Prisma, PrismaClient } from '${logicalPrismaClientDir}/index-fixed';
+import type * as _P from '${prismaClientImport}';
+import type { Prisma, PrismaClient } from '${prismaClientImport}';
 export type { PrismaClient };
 `;
     }
@@ -229,10 +223,14 @@ export function enhance(prisma: any, context?: EnhancementContext<${authTypePara
 `;
     }
 
-    private needsLogicalClient() {
+    private get needsLogicalClient() {
         return this.hasDelegateModel(this.model) || this.hasAuthInDefault(this.model);
     }
 
+    private get needsPrismaClientTypeFixes() {
+        return this.hasTypeDef(this.model);
+    }
+
     private hasDelegateModel(model: Model) {
         const dataModels = getDataModels(model);
         return dataModels.some(
@@ -246,6 +244,10 @@ export function enhance(prisma: any, context?: EnhancementContext<${authTypePara
         );
     }
 
+    private hasTypeDef(model: Model) {
+        return model.declarations.some(isTypeDef);
+    }
+
     private async generateLogicalPrisma() {
         const prismaGenerator = new PrismaSchemaGenerator(this.model);
 
@@ -349,18 +351,27 @@ export function enhance(prisma: any, context?: EnhancementContext<${authTypePara
             overwrite: true,
         });
 
-        if (delegateInfo.length > 0) {
-            // transform types for delegated models
-            this.transformDelegate(sf, sfNew, delegateInfo);
-            sfNew.formatText();
-        } else {
-            // just copy
-            sfNew.replaceWithText(sf.getFullText());
-        }
+        this.transformPrismaTypes(sf, sfNew, delegateInfo);
+
+        this.generateExtraTypes(sfNew);
+        sfNew.formatText();
+
+        // if (delegateInfo.length > 0) {
+        //     // transform types for delegated models
+        //     this.transformDelegate(sf, sfNew, delegateInfo);
+        //     sfNew.formatText();
+        // } else {
+
+        //     this.transformJsonFields(sf, sfNew);
+
+        //     // // just copy
+        //     // sfNew.replaceWithText(sf.getFullText());
+        // }
+
         await sfNew.save();
     }
 
-    private transformDelegate(sf: SourceFile, sfNew: SourceFile, delegateInfo: DelegateInfo) {
+    private transformPrismaTypes(sf: SourceFile, sfNew: SourceFile, delegateInfo: DelegateInfo) {
         // copy toplevel imports
         sfNew.addImportDeclarations(sf.getImportDeclarations().map((n) => n.getStructure()));
 
@@ -493,10 +504,72 @@ export function enhance(prisma: any, context?: EnhancementContext<${authTypePara
         // fix delegate payload union type
         source = this.fixDelegatePayloadType(typeAlias, delegateInfo, source);
 
+        // fix json field type
+        source = this.fixJsonFieldType(typeAlias, source);
+
         structure.type = source;
         return structure;
     }
 
+    private fixJsonFieldType(typeAlias: TypeAliasDeclaration, source: string) {
+        const modelsWithTypeField = this.model.declarations.filter(
+            (d): d is DataModel => isDataModel(d) && d.fields.some((f) => isTypeDef(f.type.reference?.ref))
+        );
+        const typeName = typeAlias.getName();
+
+        const getTypedJsonFields = (model: DataModel) => {
+            return model.fields.filter((f) => isTypeDef(f.type.reference?.ref));
+        };
+
+        const replacePrismaJson = (source: string, field: DataModelField) => {
+            return source.replace(
+                new RegExp(`(${field.name}\\??\\s*):[^\\n]+`),
+                `$1: ${field.type.reference!.$refText}${field.type.array ? '[]' : ''}${
+                    field.type.optional ? ' | null' : ''
+                }`
+            );
+        };
+
+        // fix "$[Model]Payload" type
+        const payloadModelMatch = modelsWithTypeField.find((m) => `$${m.name}Payload` === typeName);
+        if (payloadModelMatch) {
+            const scalars = typeAlias
+                .getDescendantsOfKind(SyntaxKind.PropertySignature)
+                .find((p) => p.getName() === 'scalars');
+            if (!scalars) {
+                return source;
+            }
+
+            const fieldsToFix = getTypedJsonFields(payloadModelMatch);
+            for (const field of fieldsToFix) {
+                source = replacePrismaJson(source, field);
+            }
+        }
+
+        // fix input/output types, "[Model]CreateInput", etc.
+        const inputOutputModelMatch = modelsWithTypeField.find((m) => typeName.startsWith(m.name));
+        if (inputOutputModelMatch) {
+            const relevantTypePatterns = [
+                'GroupByOutputType',
+                '(Unchecked)?Create(\\S+?)?Input',
+                '(Unchecked)?Update(\\S+?)?Input',
+                'CreateManyInput',
+                '(Unchecked)?UpdateMany(Mutation)?Input',
+            ];
+            const typeRegex = modelsWithTypeField.map(
+                (m) => new RegExp(`^(${m.name})(${relevantTypePatterns.join('|')})$`)
+            );
+            if (typeRegex.some((r) => r.test(typeName))) {
+                const fieldsToFix = getTypedJsonFields(inputOutputModelMatch);
+                for (const field of fieldsToFix) {
+                    source = replacePrismaJson(source, field);
+                }
+            }
+        }
+
+        return source;
+    }
+
     private fixDelegatePayloadType(typeAlias: TypeAliasDeclaration, delegateInfo: DelegateInfo, source: string) {
         // change the type of `$<DelegateModel>Payload` type of delegate model to a union of concrete types
         const typeName = typeAlias.getName();
@@ -677,4 +750,12 @@ export function enhance(prisma: any, context?: EnhancementContext<${authTypePara
     private get generatePermissionChecker() {
         return this.options.generatePermissionChecker === true;
     }
+
+    private async generateExtraTypes(sf: SourceFile) {
+        for (const decl of this.model.declarations) {
+            if (isTypeDef(decl)) {
+                generateTypeDefType(sf, decl);
+            }
+        }
+    }
 }
diff --git a/packages/schema/src/plugins/enhancer/enhance/model-typedef-generator.ts b/packages/schema/src/plugins/enhancer/enhance/model-typedef-generator.ts
new file mode 100644
index 000000000..40bc3e5b4
--- /dev/null
+++ b/packages/schema/src/plugins/enhancer/enhance/model-typedef-generator.ts
@@ -0,0 +1,63 @@
+import { PluginError } from '@zenstackhq/sdk';
+import { BuiltinType, TypeDef, TypeDefFieldType } from '@zenstackhq/sdk/ast';
+import { SourceFile } from 'ts-morph';
+import { match } from 'ts-pattern';
+import { name } from '..';
+
+export function generateTypeDefType(sourceFile: SourceFile, decl: TypeDef) {
+    sourceFile.addTypeAlias({
+        name: decl.name,
+        isExported: true,
+        docs: decl.comments.map((c) => unwrapTripleSlashComment(c)),
+        type: (writer) => {
+            writer.block(() => {
+                decl.fields.forEach((field) => {
+                    if (field.comments.length > 0) {
+                        writer.writeLine(`    /**`);
+                        field.comments.forEach((c) => writer.writeLine(`     * ${unwrapTripleSlashComment(c)}`));
+                        writer.writeLine(`     */`);
+                    }
+                    writer.writeLine(
+                        `    ${field.name}${field.type.optional ? '?' : ''}: ${zmodelTypeToTsType(field.type)};`
+                    );
+                });
+            });
+        },
+    });
+}
+
+function unwrapTripleSlashComment(c: string): string {
+    return c.replace(/^[/]*\s*/, '');
+}
+
+function zmodelTypeToTsType(type: TypeDefFieldType) {
+    let result: string;
+
+    if (type.type) {
+        result = builtinTypeToTsType(type.type);
+    } else if (type.reference?.ref) {
+        result = type.reference.ref.name;
+    } else {
+        throw new PluginError(name, `Unsupported field type: ${type}`);
+    }
+
+    if (type.array) {
+        result += '[]';
+    }
+
+    return result;
+}
+
+function builtinTypeToTsType(type: BuiltinType) {
+    return match(type)
+        .with('Boolean', () => 'boolean')
+        .with('BigInt', () => 'bigint')
+        .with('Int', () => 'number')
+        .with('Float', () => 'number')
+        .with('Decimal', () => 'Prisma.Decimal')
+        .with('String', () => 'string')
+        .with('Bytes', () => 'Uint8Array')
+        .with('DateTime', () => 'Date')
+        .with('Json', () => 'unknown')
+        .exhaustive();
+}
diff --git a/packages/schema/src/plugins/enhancer/model-meta/index.ts b/packages/schema/src/plugins/enhancer/model-meta/index.ts
index 38757ae6f..53fecdb82 100644
--- a/packages/schema/src/plugins/enhancer/model-meta/index.ts
+++ b/packages/schema/src/plugins/enhancer/model-meta/index.ts
@@ -1,15 +1,16 @@
 import { generateModelMeta, getDataModels, type PluginOptions } from '@zenstackhq/sdk';
-import type { Model } from '@zenstackhq/sdk/ast';
+import { isTypeDef, type Model } from '@zenstackhq/sdk/ast';
 import path from 'path';
 import type { Project } from 'ts-morph';
 
 export async function generate(model: Model, options: PluginOptions, project: Project, outDir: string) {
     const outFile = path.join(outDir, 'model-meta.ts');
     const dataModels = getDataModels(model);
+    const typeDefs = model.declarations.filter(isTypeDef);
 
     // save ts files if requested explicitly or the user provided
     const preserveTsFiles = options.preserveTsFiles === true || !!options.output;
-    await generateModelMeta(project, dataModels, {
+    await generateModelMeta(project, dataModels, typeDefs, {
         output: outFile,
         generateAttributes: true,
         preserveTsFiles,
diff --git a/packages/schema/src/plugins/enhancer/policy/policy-guard-generator.ts b/packages/schema/src/plugins/enhancer/policy/policy-guard-generator.ts
index aa54c80d8..62469f744 100644
--- a/packages/schema/src/plugins/enhancer/policy/policy-guard-generator.ts
+++ b/packages/schema/src/plugins/enhancer/policy/policy-guard-generator.ts
@@ -11,6 +11,7 @@ import {
     isMemberAccessExpr,
     isReferenceExpr,
     isThisExpr,
+    isTypeDef,
 } from '@zenstackhq/language/ast';
 import { PolicyCrudKind, type PolicyOperationKind } from '@zenstackhq/runtime';
 import {
@@ -747,7 +748,14 @@ export class PolicyGenerator {
             for (const model of models) {
                 writer.write(`${lowerCaseFirst(model.name)}:`);
                 writer.inlineBlock(() => {
-                    writer.write(`hasValidation: ${hasValidationAttributes(model)}`);
+                    writer.write(
+                        `hasValidation: ${
+                            // explicit validation rules
+                            hasValidationAttributes(model) ||
+                            // type-def fields require schema validation
+                            this.hasTypeDefFields(model)
+                        }`
+                    );
                 });
                 writer.writeLine(',');
             }
@@ -755,5 +763,9 @@ export class PolicyGenerator {
         writer.writeLine(',');
     }
 
+    private hasTypeDefFields(model: DataModel): boolean {
+        return model.fields.some((f) => isTypeDef(f.type.reference?.ref));
+    }
+
     // #endregion
 }
diff --git a/packages/schema/src/plugins/prisma/schema-generator.ts b/packages/schema/src/plugins/prisma/schema-generator.ts
index f3dcba460..9a787ab8b 100644
--- a/packages/schema/src/plugins/prisma/schema-generator.ts
+++ b/packages/schema/src/plugins/prisma/schema-generator.ts
@@ -23,6 +23,7 @@ import {
     isNullExpr,
     isReferenceExpr,
     isStringLiteral,
+    isTypeDef,
     LiteralExpr,
     Model,
     NumberLiteral,
@@ -785,13 +786,34 @@ export class PrismaSchemaGenerator {
     }
 
     private generateModelField(model: PrismaDataModel, field: DataModelField, addToFront = false) {
-        const fieldType =
-            field.type.type || field.type.reference?.ref?.name || this.getUnsupportedFieldType(field.type);
+        let fieldType: string | undefined;
+
+        if (field.type.type) {
+            // intrinsic type
+            fieldType = field.type.type;
+        } else if (field.type.reference?.ref) {
+            // model, enum, or type-def
+            if (isTypeDef(field.type.reference.ref)) {
+                fieldType = 'Json';
+            } else {
+                fieldType = field.type.reference.ref.name;
+            }
+        } else {
+            // Unsupported type
+            const unsupported = this.getUnsupportedFieldType(field.type);
+            if (unsupported) {
+                fieldType = unsupported;
+            }
+        }
+
         if (!fieldType) {
             throw new PluginError(name, `Field type is not resolved: ${field.$container.name}.${field.name}`);
         }
 
-        const type = new ModelFieldType(fieldType, field.type.array, field.type.optional);
+        const isArray =
+            // typed-JSON fields should be translated to scalar Json type
+            isTypeDef(field.type.reference?.ref) ? false : field.type.array;
+        const type = new ModelFieldType(fieldType, isArray, field.type.optional);
 
         const attributes = field.attributes
             .filter((attr) => this.isPrismaAttribute(attr))
diff --git a/packages/schema/src/plugins/zod/generator.ts b/packages/schema/src/plugins/zod/generator.ts
index ca26ffabe..01a5920ff 100644
--- a/packages/schema/src/plugins/zod/generator.ts
+++ b/packages/schema/src/plugins/zod/generator.ts
@@ -14,12 +14,12 @@ import {
     parseOptionAsStrings,
     resolvePath,
 } from '@zenstackhq/sdk';
-import { DataModel, EnumField, Model, isDataModel, isEnum } from '@zenstackhq/sdk/ast';
+import { DataModel, EnumField, Model, TypeDef, isDataModel, isEnum, isTypeDef } from '@zenstackhq/sdk/ast';
 import { addMissingInputObjectTypes, resolveAggregateOperationSupport } from '@zenstackhq/sdk/dmmf-helpers';
 import { getPrismaClientImportSpec, supportCreateMany, type DMMF } from '@zenstackhq/sdk/prisma';
 import { streamAllContents } from 'langium';
 import path from 'path';
-import type { SourceFile } from 'ts-morph';
+import type { CodeBlockWriter, SourceFile } from 'ts-morph';
 import { upperCaseFirst } from 'upper-case-first';
 import { name } from '.';
 import { getDefaultOutputFolder } from '../plugin-utils';
@@ -274,6 +274,12 @@ export class ZodSchemaGenerator {
             }
         }
 
+        for (const typeDef of this.model.declarations.filter(isTypeDef)) {
+            if (!excludedModels.includes(typeDef.name)) {
+                schemaNames.push(await this.generateTypeDefSchema(typeDef, output));
+            }
+        }
+
         this.sourceFiles.push(
             this.project.createSourceFile(
                 path.join(output, 'models', 'index.ts'),
@@ -283,6 +289,89 @@ export class ZodSchemaGenerator {
         );
     }
 
+    private generateTypeDefSchema(typeDef: TypeDef, output: string) {
+        const schemaName = `${upperCaseFirst(typeDef.name)}.schema`;
+        const sf = this.project.createSourceFile(path.join(output, 'models', `${schemaName}.ts`), undefined, {
+            overwrite: true,
+        });
+        this.sourceFiles.push(sf);
+        sf.replaceWithText((writer) => {
+            this.addPreludeAndImports(typeDef, writer, output);
+
+            writer.write(`export const ${typeDef.name}Schema = z.object(`);
+            writer.inlineBlock(() => {
+                typeDef.fields.forEach((field) => {
+                    writer.writeLine(`${field.name}: ${makeFieldSchema(field)},`);
+                });
+            });
+
+            switch (this.options.mode) {
+                case 'strip':
+                    // zod strips by default
+                    writer.writeLine(')');
+                    break;
+                case 'passthrough':
+                    writer.writeLine(').passthrough();');
+                    break;
+                default:
+                    writer.writeLine(').strict();');
+                    break;
+            }
+        });
+
+        // TODO: "@@validate" refinements
+
+        return schemaName;
+    }
+
+    private addPreludeAndImports(decl: DataModel | TypeDef, writer: CodeBlockWriter, output: string) {
+        writer.writeLine('/* eslint-disable */');
+        writer.writeLine(`import { z } from 'zod';`);
+
+        // import user-defined enums from Prisma as they might be referenced in the expressions
+        const importEnums = new Set<string>();
+        for (const node of streamAllContents(decl)) {
+            if (isEnumFieldReference(node)) {
+                const field = node.target.ref as EnumField;
+                if (!isFromStdlib(field.$container)) {
+                    importEnums.add(field.$container.name);
+                }
+            }
+        }
+        if (importEnums.size > 0) {
+            const prismaImport = computePrismaClientImport(path.join(output, 'models'), this.options);
+            writer.writeLine(`import { ${[...importEnums].join(', ')} } from '${prismaImport}';`);
+        }
+
+        // import enum schemas
+        const importedEnumSchemas = new Set<string>();
+        for (const field of decl.fields) {
+            if (field.type.reference?.ref && isEnum(field.type.reference?.ref)) {
+                const name = upperCaseFirst(field.type.reference?.ref.name);
+                if (!importedEnumSchemas.has(name)) {
+                    writer.writeLine(`import { ${name}Schema } from '../enums/${name}.schema';`);
+                    importedEnumSchemas.add(name);
+                }
+            }
+        }
+
+        // import Decimal
+        if (decl.fields.some((field) => field.type.type === 'Decimal')) {
+            writer.writeLine(`import { DecimalSchema } from '../common';`);
+            writer.writeLine(`import { Decimal } from 'decimal.js';`);
+        }
+
+        // import referenced types' schemas
+        const referencedTypes = new Set(
+            decl.fields
+                .filter((field) => isTypeDef(field.type.reference?.ref) && field.type.reference?.ref.name !== decl.name)
+                .map((field) => field.type.reference!.ref!.name)
+        );
+        for (const refType of referencedTypes) {
+            writer.writeLine(`import { ${upperCaseFirst(refType)}Schema } from './${upperCaseFirst(refType)}.schema';`);
+        }
+    }
+
     private async generateModelSchema(model: DataModel, output: string) {
         const schemaName = `${upperCaseFirst(model.name)}.schema`;
         const sf = this.project.createSourceFile(path.join(output, 'models', `${schemaName}.ts`), undefined, {
@@ -301,41 +390,7 @@ export class ZodSchemaGenerator {
             const relations = model.fields.filter((field) => isDataModel(field.type.reference?.ref));
             const fkFields = model.fields.filter((field) => isForeignKeyField(field));
 
-            writer.writeLine('/* eslint-disable */');
-            writer.writeLine(`import { z } from 'zod';`);
-
-            // import user-defined enums from Prisma as they might be referenced in the expressions
-            const importEnums = new Set<string>();
-            for (const node of streamAllContents(model)) {
-                if (isEnumFieldReference(node)) {
-                    const field = node.target.ref as EnumField;
-                    if (!isFromStdlib(field.$container)) {
-                        importEnums.add(field.$container.name);
-                    }
-                }
-            }
-            if (importEnums.size > 0) {
-                const prismaImport = computePrismaClientImport(path.join(output, 'models'), this.options);
-                writer.writeLine(`import { ${[...importEnums].join(', ')} } from '${prismaImport}';`);
-            }
-
-            // import enum schemas
-            const importedEnumSchemas = new Set<string>();
-            for (const field of scalarFields) {
-                if (field.type.reference?.ref && isEnum(field.type.reference?.ref)) {
-                    const name = upperCaseFirst(field.type.reference?.ref.name);
-                    if (!importedEnumSchemas.has(name)) {
-                        writer.writeLine(`import { ${name}Schema } from '../enums/${name}.schema';`);
-                        importedEnumSchemas.add(name);
-                    }
-                }
-            }
-
-            // import Decimal
-            if (scalarFields.some((field) => field.type.type === 'Decimal')) {
-                writer.writeLine(`import { DecimalSchema } from '../common';`);
-                writer.writeLine(`import { Decimal } from 'decimal.js';`);
-            }
+            this.addPreludeAndImports(model, writer, output);
 
             // base schema - including all scalar fields, with optionality following the schema
             writer.write(`const baseSchema = z.object(`);
diff --git a/packages/schema/src/plugins/zod/transformer.ts b/packages/schema/src/plugins/zod/transformer.ts
index 698ad2ac6..6b83e5723 100644
--- a/packages/schema/src/plugins/zod/transformer.ts
+++ b/packages/schema/src/plugins/zod/transformer.ts
@@ -1,6 +1,6 @@
 /* eslint-disable @typescript-eslint/ban-ts-comment */
 import { indentString, isDiscriminatorField, type PluginOptions } from '@zenstackhq/sdk';
-import { DataModel, isDataModel, type Model } from '@zenstackhq/sdk/ast';
+import { DataModel, isDataModel, isTypeDef, type Model } from '@zenstackhq/sdk/ast';
 import { checkModelHasModelRelation, findModelByName, isAggregateInputType } from '@zenstackhq/sdk/dmmf-helpers';
 import { supportCreateMany, type DMMF as PrismaDMMF } from '@zenstackhq/sdk/prisma';
 import path from 'path';
@@ -88,29 +88,33 @@ export default class Transformer {
     }
 
     generateObjectSchema(generateUnchecked: boolean, options: PluginOptions) {
-        const zodObjectSchemaFields = this.generateObjectSchemaFields(generateUnchecked);
-        const objectSchema = this.prepareObjectSchema(zodObjectSchemaFields, options);
+        const { schemaFields, extraImports } = this.generateObjectSchemaFields(generateUnchecked);
+        const objectSchema = this.prepareObjectSchema(schemaFields, options);
 
         const filePath = path.join(Transformer.outputPath, `objects/${this.name}.schema.ts`);
-        const content = '/* eslint-disable */\n' + objectSchema;
+        const content = '/* eslint-disable */\n' + extraImports.join('\n\n') + objectSchema;
         this.sourceFiles.push(this.project.createSourceFile(filePath, content, { overwrite: true }));
         return `${this.name}.schema`;
     }
 
-    private delegateCreateUpdateInputRegex = /(\S+)(Unchecked)?(Create|Update).*Input/;
+    private createUpdateInputRegex = /(\S+?)(Unchecked)?(Create|Update|CreateMany|UpdateMany).*Input/;
 
     generateObjectSchemaFields(generateUnchecked: boolean) {
         let fields = this.fields;
+        let contextDataModel: DataModel | undefined;
+        const extraImports: string[] = [];
 
         // exclude discriminator fields from create/update input schemas
-        const createUpdateMatch = this.delegateCreateUpdateInputRegex.exec(this.name);
+        const createUpdateMatch = this.createUpdateInputRegex.exec(this.name);
         if (createUpdateMatch) {
             const modelName = createUpdateMatch[1];
-            const dataModel = this.zmodel.declarations.find(
+            contextDataModel = this.zmodel.declarations.find(
                 (d): d is DataModel => isDataModel(d) && d.name === modelName
             );
-            if (dataModel) {
-                const discriminatorFields = dataModel.fields.filter(isDiscriminatorField);
+
+            if (contextDataModel) {
+                // exclude discriminator fields from create/update input schemas
+                const discriminatorFields = contextDataModel.fields.filter(isDiscriminatorField);
                 if (discriminatorFields.length > 0) {
                     fields = fields.filter((field) => {
                         return !discriminatorFields.some(
@@ -118,11 +122,23 @@ export default class Transformer {
                         );
                     });
                 }
+
+                // import type-def's schemas
+                const typeDefFields = contextDataModel.fields.filter((f) => isTypeDef(f.type.reference?.ref));
+                typeDefFields.forEach((field) => {
+                    const typeName = upperCaseFirst(field.type.reference!.$refText);
+                    const importLine = `import { ${typeName}Schema } from '../models/${typeName}.schema';`;
+                    if (!extraImports.includes(importLine)) {
+                        extraImports.push(importLine);
+                    }
+                });
             }
         }
 
         const zodObjectSchemaFields = fields
-            .map((field) => this.generateObjectSchemaField(field, generateUnchecked))
+            .map((field) =>
+                this.generateObjectSchemaField(field, contextDataModel, generateUnchecked, !!createUpdateMatch)
+            )
             .flatMap((item) => item)
             .map((item) => {
                 const [zodStringWithMainType, field, skipValidators] = item;
@@ -133,12 +149,14 @@ export default class Transformer {
 
                 return value.trim();
             });
-        return zodObjectSchemaFields;
+        return { schemaFields: zodObjectSchemaFields, extraImports };
     }
 
     generateObjectSchemaField(
         field: PrismaDMMF.SchemaArg,
-        generateUnchecked: boolean
+        contextDataModel: DataModel | undefined,
+        generateUnchecked: boolean,
+        replaceJsonWithTypeDef = false
     ): [string, PrismaDMMF.SchemaArg, boolean][] {
         const lines = field.inputTypes;
 
@@ -146,64 +164,75 @@ export default class Transformer {
             return [];
         }
 
-        let alternatives = lines.reduce<string[]>((result, inputType) => {
-            if (!generateUnchecked && typeof inputType.type === 'string' && inputType.type.includes('Unchecked')) {
-                return result;
-            }
+        let alternatives: string[] | undefined = undefined;
 
-            if (inputType.type.includes('CreateMany') && !supportCreateMany(this.zmodel)) {
-                return result;
+        if (replaceJsonWithTypeDef) {
+            const dmField = contextDataModel?.fields.find((f) => f.name === field.name);
+            if (isTypeDef(dmField?.type.reference?.ref)) {
+                alternatives = [`z.lazy(() => ${upperCaseFirst(dmField?.type.reference!.$refText)}Schema)`];
             }
+        }
 
-            // TODO: unify the following with `schema-gen.ts`
-
-            if (inputType.type === 'String') {
-                result.push(this.wrapWithZodValidators('z.string()', field, inputType));
-            } else if (inputType.type === 'Int' || inputType.type === 'Float') {
-                result.push(this.wrapWithZodValidators('z.number()', field, inputType));
-            } else if (inputType.type === 'Decimal') {
-                this.hasDecimal = true;
-                result.push(this.wrapWithZodValidators('DecimalSchema', field, inputType));
-            } else if (inputType.type === 'BigInt') {
-                result.push(this.wrapWithZodValidators('z.bigint()', field, inputType));
-            } else if (inputType.type === 'Boolean') {
-                result.push(this.wrapWithZodValidators('z.boolean()', field, inputType));
-            } else if (inputType.type === 'DateTime') {
-                result.push(this.wrapWithZodValidators(['z.date()', 'z.string().datetime()'], field, inputType));
-            } else if (inputType.type === 'Bytes') {
-                result.push(
-                    this.wrapWithZodValidators(
-                        `z.custom<Buffer | Uint8Array>(data => data instanceof Uint8Array)`,
-                        field,
-                        inputType
-                    )
-                );
-            } else if (inputType.type === 'Json') {
-                this.hasJson = true;
-                result.push(this.wrapWithZodValidators('jsonSchema', field, inputType));
-            } else if (inputType.type === 'True') {
-                result.push(this.wrapWithZodValidators('z.literal(true)', field, inputType));
-            } else if (inputType.type === 'Null') {
-                result.push(this.wrapWithZodValidators('z.null()', field, inputType));
-            } else {
-                const isEnum = inputType.location === 'enumTypes';
-                const isFieldRef = inputType.location === 'fieldRefTypes';
-
-                if (
-                    // fieldRefTypes refer to other fields in the model and don't need to be generated as part of schema
-                    !isFieldRef &&
-                    (inputType.namespace === 'prisma' || isEnum)
-                ) {
-                    if (inputType.type !== this.originalName && typeof inputType.type === 'string') {
-                        this.addSchemaImport(inputType.type);
-                    }
+        if (!alternatives) {
+            alternatives = lines.reduce<string[]>((result, inputType) => {
+                if (!generateUnchecked && typeof inputType.type === 'string' && inputType.type.includes('Unchecked')) {
+                    return result;
+                }
 
-                    result.push(this.generatePrismaStringLine(field, inputType, lines.length));
+                if (inputType.type.includes('CreateMany') && !supportCreateMany(this.zmodel)) {
+                    return result;
+                }
+
+                // TODO: unify the following with `schema-gen.ts`
+
+                if (inputType.type === 'String') {
+                    result.push(this.wrapWithZodValidators('z.string()', field, inputType));
+                } else if (inputType.type === 'Int' || inputType.type === 'Float') {
+                    result.push(this.wrapWithZodValidators('z.number()', field, inputType));
+                } else if (inputType.type === 'Decimal') {
+                    this.hasDecimal = true;
+                    result.push(this.wrapWithZodValidators('DecimalSchema', field, inputType));
+                } else if (inputType.type === 'BigInt') {
+                    result.push(this.wrapWithZodValidators('z.bigint()', field, inputType));
+                } else if (inputType.type === 'Boolean') {
+                    result.push(this.wrapWithZodValidators('z.boolean()', field, inputType));
+                } else if (inputType.type === 'DateTime') {
+                    result.push(this.wrapWithZodValidators(['z.date()', 'z.string().datetime()'], field, inputType));
+                } else if (inputType.type === 'Bytes') {
+                    result.push(
+                        this.wrapWithZodValidators(
+                            `z.custom<Buffer | Uint8Array>(data => data instanceof Uint8Array)`,
+                            field,
+                            inputType
+                        )
+                    );
+                } else if (inputType.type === 'Json') {
+                    this.hasJson = true;
+                    result.push(this.wrapWithZodValidators('jsonSchema', field, inputType));
+                } else if (inputType.type === 'True') {
+                    result.push(this.wrapWithZodValidators('z.literal(true)', field, inputType));
+                } else if (inputType.type === 'Null') {
+                    result.push(this.wrapWithZodValidators('z.null()', field, inputType));
+                } else {
+                    const isEnum = inputType.location === 'enumTypes';
+                    const isFieldRef = inputType.location === 'fieldRefTypes';
+
+                    if (
+                        // fieldRefTypes refer to other fields in the model and don't need to be generated as part of schema
+                        !isFieldRef &&
+                        (inputType.namespace === 'prisma' || isEnum)
+                    ) {
+                        if (inputType.type !== this.originalName && typeof inputType.type === 'string') {
+                            this.addSchemaImport(inputType.type);
+                        }
+
+                        result.push(this.generatePrismaStringLine(field, inputType, lines.length));
+                    }
                 }
-            }
 
-            return result;
-        }, []);
+                return result;
+            }, []);
+        }
 
         if (alternatives.length === 0) {
             return [];
diff --git a/packages/schema/src/plugins/zod/utils/schema-gen.ts b/packages/schema/src/plugins/zod/utils/schema-gen.ts
index ee46390ff..c130934b2 100644
--- a/packages/schema/src/plugins/zod/utils/schema-gen.ts
+++ b/packages/schema/src/plugins/zod/utils/schema-gen.ts
@@ -1,32 +1,34 @@
 import {
     ExpressionContext,
-    PluginError,
-    TypeScriptExpressionTransformer,
-    TypeScriptExpressionTransformerError,
     getAttributeArg,
     getAttributeArgLiteral,
     getLiteral,
     getLiteralArray,
     isDataModelFieldReference,
     isFromStdlib,
+    PluginError,
+    TypeScriptExpressionTransformer,
+    TypeScriptExpressionTransformerError,
 } from '@zenstackhq/sdk';
 import {
     DataModel,
     DataModelField,
     DataModelFieldAttribute,
-    isDataModel,
     isArrayExpr,
+    isBooleanLiteral,
+    isDataModel,
     isEnum,
     isInvocationExpr,
     isNumberLiteral,
     isStringLiteral,
-    isBooleanLiteral
+    isTypeDef,
+    TypeDefField,
 } from '@zenstackhq/sdk/ast';
 import { upperCaseFirst } from 'upper-case-first';
 import { name } from '..';
 import { isDefaultWithAuth } from '../../enhancer/enhancer-utils';
 
-export function makeFieldSchema(field: DataModelField) {
+export function makeFieldSchema(field: DataModelField | TypeDefField) {
     if (isDataModel(field.type.reference?.ref)) {
         if (field.type.array) {
             // array field is always optional
@@ -172,11 +174,17 @@ export function makeFieldSchema(field: DataModelField) {
     return schema;
 }
 
-function makeZodSchema(field: DataModelField) {
+function makeZodSchema(field: DataModelField | TypeDefField) {
     let schema: string;
 
-    if (field.type.reference?.ref && isEnum(field.type.reference?.ref)) {
-        schema = `${upperCaseFirst(field.type.reference.ref.name)}Schema`;
+    if (field.type.reference?.ref) {
+        if (isEnum(field.type.reference?.ref)) {
+            schema = `${upperCaseFirst(field.type.reference.ref.name)}Schema`;
+        } else if (isTypeDef(field.type.reference?.ref)) {
+            schema = `z.lazy(() => ${upperCaseFirst(field.type.reference.ref.name)}Schema)`;
+        } else {
+            schema = 'z.any()';
+        }
     } else {
         switch (field.type.type) {
             case 'Int':
@@ -227,7 +235,8 @@ export function makeValidationRefinements(model: DataModel) {
             const message = messageArg ? `message: ${JSON.stringify(messageArg)},` : '';
 
             const pathArg = getAttributeArg(attr, 'path');
-            const path = pathArg && isArrayExpr(pathArg) ? `path: ['${getLiteralArray<string>(pathArg)?.join(`', '`)}'],` : '';
+            const path =
+                pathArg && isArrayExpr(pathArg) ? `path: ['${getLiteralArray<string>(pathArg)?.join(`', '`)}'],` : '';
 
             const options = `, { ${message} ${path} }`;
 
@@ -272,7 +281,7 @@ function refineDecimal(op: 'gt' | 'gte' | 'lt' | 'lte', value: number, messageAr
     }${messageArg})`;
 }
 
-export function getFieldSchemaDefault(field: DataModelField) {
+export function getFieldSchemaDefault(field: DataModelField | TypeDefField) {
     const attr = field.attributes.find((attr) => attr.decl.ref?.name === '@default');
     if (!attr) {
         return undefined;
diff --git a/packages/schema/src/res/stdlib.zmodel b/packages/schema/src/res/stdlib.zmodel
index a436ea4a8..62cefd36e 100644
--- a/packages/schema/src/res/stdlib.zmodel
+++ b/packages/schema/src/res/stdlib.zmodel
@@ -47,6 +47,7 @@ enum AttributeTargetField {
     JsonField
     BytesField
     ModelField
+    TypeDefField
 }
 
 /**
@@ -175,6 +176,11 @@ function isEmpty(field: Any[]): Boolean {
  */
 attribute @@@targetField(_ targetField: AttributeTargetField[])
 
+/**
+ * Marks an attribute to be applicable to type defs and fields.
+ */
+attribute @@@supportTypeDef()
+
 /**
  * Marks an attribute to be used for data validation.
  */
@@ -209,7 +215,7 @@ attribute @id(map: String?, length: Int?, sort: SortOrder?, clustered: Boolean?)
  * Defines a default value for a field.
  * @param value: An expression (e.g. 5, true, now(), auth()).
  */
-attribute @default(_ value: ContextType, map: String?) @@@prisma
+attribute @default(_ value: ContextType, map: String?) @@@prisma @@@supportTypeDef
 
 /**
  * Defines a unique constraint for this field.
@@ -558,77 +564,77 @@ attribute @omit()
 /**
  * Validates length of a string field.
  */
-attribute @length(_ min: Int?, _ max: Int?, _ message: String?) @@@targetField([StringField]) @@@validation
+attribute @length(_ min: Int?, _ max: Int?, _ message: String?) @@@targetField([StringField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates a string field value starts with the given text.
  */
-attribute @startsWith(_ text: String, _ message: String?) @@@targetField([StringField]) @@@validation
+attribute @startsWith(_ text: String, _ message: String?) @@@targetField([StringField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates a string field value ends with the given text.
  */
-attribute @endsWith(_ text: String, _ message: String?) @@@targetField([StringField]) @@@validation
+attribute @endsWith(_ text: String, _ message: String?) @@@targetField([StringField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates a string field value contains the given text.
  */
-attribute @contains(_ text: String, _ message: String?) @@@targetField([StringField]) @@@validation
+attribute @contains(_ text: String, _ message: String?) @@@targetField([StringField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates a string field value matches a regex.
  */
-attribute @regex(_ regex: String, _ message: String?) @@@targetField([StringField]) @@@validation
+attribute @regex(_ regex: String, _ message: String?) @@@targetField([StringField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates a string field value is a valid email address.
  */
-attribute @email(_ message: String?) @@@targetField([StringField]) @@@validation
+attribute @email(_ message: String?) @@@targetField([StringField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates a string field value is a valid ISO datetime.
  */
-attribute @datetime(_ message: String?) @@@targetField([StringField]) @@@validation
+attribute @datetime(_ message: String?) @@@targetField([StringField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates a string field value is a valid url.
  */
-attribute @url(_ message: String?) @@@targetField([StringField]) @@@validation
+attribute @url(_ message: String?) @@@targetField([StringField]) @@@validation @@@supportTypeDef
 
 /**
  * Trims whitespaces from the start and end of the string.
  */
-attribute @trim() @@@targetField([StringField]) @@@validation
+attribute @trim() @@@targetField([StringField]) @@@validation @@@supportTypeDef
 
 /**
  * Transform entire string toLowerCase.
  */
-attribute @lower() @@@targetField([StringField]) @@@validation
+attribute @lower() @@@targetField([StringField]) @@@validation @@@supportTypeDef
 
 /**
  * Transform entire string toUpperCase.
  */
-attribute @upper() @@@targetField([StringField]) @@@validation
+attribute @upper() @@@targetField([StringField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates a number field is greater than the given value.
  */
-attribute @gt(_ value: Int, _ message: String?) @@@targetField([IntField, FloatField, DecimalField]) @@@validation
+attribute @gt(_ value: Int, _ message: String?) @@@targetField([IntField, FloatField, DecimalField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates a number field is greater than or equal to the given value.
  */
-attribute @gte(_ value: Int, _ message: String?) @@@targetField([IntField, FloatField, DecimalField]) @@@validation
+attribute @gte(_ value: Int, _ message: String?) @@@targetField([IntField, FloatField, DecimalField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates a number field is less than the given value.
  */
-attribute @lt(_ value: Int, _ message: String?) @@@targetField([IntField, FloatField, DecimalField]) @@@validation
+attribute @lt(_ value: Int, _ message: String?) @@@targetField([IntField, FloatField, DecimalField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates a number field is less than or equal to the given value.
  */
-attribute @lte(_ value: Int, _ message: String?) @@@targetField([IntField, FloatField, DecimalField]) @@@validation
+attribute @lte(_ value: Int, _ message: String?) @@@targetField([IntField, FloatField, DecimalField]) @@@validation @@@supportTypeDef
 
 /**
  * Validates the entity with a complex condition.
@@ -700,3 +706,8 @@ attribute @@delegate(_ discriminator: FieldReference)
  */
 function raw(value: String): Any {
 } @@@expressionContext([Index])
+
+/**
+ * Marks a field to be strong-typed JSON.
+ */
+attribute @json() @@@targetField([TypeDefField])
diff --git a/packages/schema/tests/schema/validation/attribute-validation.test.ts b/packages/schema/tests/schema/validation/attribute-validation.test.ts
index 0c89c61ae..4d86837d0 100644
--- a/packages/schema/tests/schema/validation/attribute-validation.test.ts
+++ b/packages/schema/tests/schema/validation/attribute-validation.test.ts
@@ -1354,4 +1354,19 @@ describe('Attribute tests', () => {
             'Field-level policy rules with "update" or "all" kind are not allowed for relation fields. Put rules on foreign-key fields instead.'
         );
     });
+
+    it('type def field attribute', async () => {
+        await expect(
+            loadModelWithError(`
+            model User {
+                id String @id
+                profile Profile
+            }
+            
+            type Profile {
+                email String @omit
+            }
+        `)
+        ).resolves.toContain(`attribute "@omit" cannot be used on type declaration fields`);
+    });
 });
diff --git a/packages/sdk/src/model-meta-generator.ts b/packages/sdk/src/model-meta-generator.ts
index 469cfa888..859399673 100644
--- a/packages/sdk/src/model-meta-generator.ts
+++ b/packages/sdk/src/model-meta-generator.ts
@@ -6,11 +6,15 @@ import {
     isArrayExpr,
     isBooleanLiteral,
     isDataModel,
+    isDataModelField,
     isInvocationExpr,
     isNumberLiteral,
     isReferenceExpr,
     isStringLiteral,
+    isTypeDef,
     ReferenceExpr,
+    TypeDef,
+    TypeDefField,
 } from '@zenstackhq/language/ast';
 import type { RuntimeAttribute } from '@zenstackhq/runtime';
 import { streamAst } from 'langium';
@@ -62,13 +66,18 @@ export type ModelMetaGeneratorOptions = {
     shortNameMap?: Map<string, string>;
 };
 
-export async function generate(project: Project, models: DataModel[], options: ModelMetaGeneratorOptions) {
+export async function generate(
+    project: Project,
+    models: DataModel[],
+    typeDefs: TypeDef[],
+    options: ModelMetaGeneratorOptions
+) {
     const sf = project.createSourceFile(options.output, undefined, { overwrite: true });
     sf.addStatements('/* eslint-disable */');
     sf.addVariableStatement({
         declarationKind: VariableDeclarationKind.Const,
         declarations: [
-            { name: 'metadata', initializer: (writer) => generateModelMetadata(models, sf, writer, options) },
+            { name: 'metadata', initializer: (writer) => generateModelMetadata(models, typeDefs, sf, writer, options) },
         ],
     });
     sf.addStatements('export default metadata;');
@@ -82,12 +91,14 @@ export async function generate(project: Project, models: DataModel[], options: M
 
 function generateModelMetadata(
     dataModels: DataModel[],
+    typeDefs: TypeDef[],
     sourceFile: SourceFile,
     writer: CodeBlockWriter,
     options: ModelMetaGeneratorOptions
 ) {
     writer.block(() => {
         writeModels(sourceFile, writer, dataModels, options);
+        writeTypeDefs(sourceFile, writer, typeDefs, options);
         writeDeleteCascade(writer, dataModels);
         writeShortNameMap(options, writer);
         writeAuthModel(writer, dataModels);
@@ -120,6 +131,29 @@ function writeModels(
     writer.writeLine(',');
 }
 
+function writeTypeDefs(
+    sourceFile: SourceFile,
+    writer: CodeBlockWriter,
+    typedDefs: TypeDef[],
+    options: ModelMetaGeneratorOptions
+) {
+    if (typedDefs.length === 0) {
+        return;
+    }
+    writer.write('typeDefs:');
+    writer.block(() => {
+        for (const typeDef of typedDefs) {
+            writer.write(`${lowerCaseFirst(typeDef.name)}:`);
+            writer.block(() => {
+                writer.write(`name: '${typeDef.name}',`);
+                writeFields(sourceFile, writer, typeDef, options);
+            });
+            writer.writeLine(',');
+        }
+    });
+    writer.writeLine(',');
+}
+
 function writeBaseTypes(writer: CodeBlockWriter, model: DataModel) {
     if (model.superTypes.length > 0) {
         writer.write('baseTypes: [');
@@ -189,14 +223,14 @@ function writeDiscriminator(writer: CodeBlockWriter, model: DataModel) {
 function writeFields(
     sourceFile: SourceFile,
     writer: CodeBlockWriter,
-    model: DataModel,
+    container: DataModel | TypeDef,
     options: ModelMetaGeneratorOptions
 ) {
     writer.write('fields:');
     writer.block(() => {
-        for (const f of model.fields) {
-            const backlink = getBackLink(f);
-            const fkMapping = generateForeignKeyMapping(f);
+        for (const f of container.fields) {
+            const dmField = isDataModelField(f) ? f : undefined;
+
             writer.write(`${f.name}: {`);
 
             writer.write(`
@@ -208,7 +242,7 @@ function writeFields(
                   f.type.type!
         }",`);
 
-            if (isIdField(f)) {
+            if (dmField && isIdField(dmField)) {
                 writer.write(`
         isId: true,`);
             }
@@ -216,6 +250,9 @@ function writeFields(
             if (isDataModel(f.type.reference?.ref)) {
                 writer.write(`
         isDataModel: true,`);
+            } else if (isTypeDef(f.type.reference?.ref)) {
+                writer.write(`
+        isTypeDef: true,`);
             }
 
             if (f.type.array) {
@@ -243,46 +280,53 @@ function writeFields(
                 }
             }
 
-            if (backlink) {
+            const defaultValueProvider = generateDefaultValueProvider(f, sourceFile);
+            if (defaultValueProvider) {
                 writer.write(`
-        backLink: '${backlink.name}',`);
+            defaultValueProvider: ${defaultValueProvider},`);
             }
 
-            if (isRelationOwner(f, backlink)) {
-                writer.write(`
+            if (dmField) {
+                // metadata specific to DataModelField
+
+                const backlink = getBackLink(dmField);
+                const fkMapping = generateForeignKeyMapping(dmField);
+
+                if (backlink) {
+                    writer.write(`
+        backLink: '${backlink.name}',`);
+                }
+
+                if (isRelationOwner(dmField, backlink)) {
+                    writer.write(`
         isRelationOwner: true,`);
-            }
+                }
 
-            if (isForeignKeyField(f)) {
-                writer.write(`
-        isForeignKey: true,`);
-                const relationField = getRelationField(f);
-                if (relationField) {
+                if (isForeignKeyField(dmField)) {
                     writer.write(`
+        isForeignKey: true,`);
+                    const relationField = getRelationField(dmField);
+                    if (relationField) {
+                        writer.write(`
         relationField: '${relationField.name}',`);
+                    }
                 }
-            }
 
-            if (fkMapping && Object.keys(fkMapping).length > 0) {
-                writer.write(`
+                if (fkMapping && Object.keys(fkMapping).length > 0) {
+                    writer.write(`
         foreignKeyMapping: ${JSON.stringify(fkMapping)},`);
-            }
-
-            const defaultValueProvider = generateDefaultValueProvider(f, sourceFile);
-            if (defaultValueProvider) {
-                writer.write(`
-                defaultValueProvider: ${defaultValueProvider},`);
-            }
+                }
 
-            const inheritedFromDelegate = getInheritedFromDelegate(f);
-            if (inheritedFromDelegate && !isIdField(f)) {
-                writer.write(`
+                const inheritedFromDelegate = getInheritedFromDelegate(dmField);
+                if (inheritedFromDelegate && !isIdField(dmField)) {
+                    writer.write(`
         inheritedFrom: ${JSON.stringify(inheritedFromDelegate.name)},`);
-            }
+                }
 
-            if (isAutoIncrement(f)) {
-                writer.write(`
+                if (isAutoIncrement(dmField)) {
+                    writer.write(`
         isAutoIncrement: true,`);
+                }
             }
 
             writer.write(`
@@ -337,7 +381,7 @@ function getRelationName(field: DataModelField) {
     return getAttributeArgLiteral(relAttr, 'name');
 }
 
-function getAttributes(target: DataModelField | DataModel): RuntimeAttribute[] {
+function getAttributes(target: DataModelField | DataModel | TypeDefField): RuntimeAttribute[] {
     return target.attributes
         .map((attr) => {
             const args: Array<{ name?: string; value: unknown }> = [];
@@ -498,7 +542,7 @@ function getDeleteCascades(model: DataModel): string[] {
         .map((m) => m.name);
 }
 
-function generateDefaultValueProvider(field: DataModelField, sourceFile: SourceFile) {
+function generateDefaultValueProvider(field: DataModelField | TypeDefField, sourceFile: SourceFile) {
     const defaultAttr = getAttribute(field, '@default');
     if (!defaultAttr) {
         return undefined;
diff --git a/packages/sdk/src/utils.ts b/packages/sdk/src/utils.ts
index 6fbcfcbf3..6b2bfe868 100644
--- a/packages/sdk/src/utils.ts
+++ b/packages/sdk/src/utils.ts
@@ -30,6 +30,7 @@ import {
     Model,
     Reference,
     ReferenceExpr,
+    TypeDefField,
 } from '@zenstackhq/language/ast';
 import fs from 'node:fs';
 import path from 'path';
@@ -123,7 +124,7 @@ export function hasAttribute(
 }
 
 export function getAttribute(
-    decl: DataModel | DataModelField | Enum | EnumField | FunctionDecl | Attribute | AttributeParam,
+    decl: DataModel | DataModelField | TypeDefField | Enum | EnumField | FunctionDecl | Attribute | AttributeParam,
     name: string
 ) {
     return (decl.attributes as (DataModelAttribute | DataModelFieldAttribute)[]).find(
@@ -460,6 +461,9 @@ export function isDelegateModel(node: AstNode) {
 }
 
 export function isDiscriminatorField(field: DataModelField) {
+    if (!isDataModel(field.$container)) {
+        return false;
+    }
     const model = field.$inheritedFrom ?? field.$container;
     const delegateAttr = getAttribute(model, '@@delegate');
     if (!delegateAttr) {
diff --git a/packages/sdk/src/validation.ts b/packages/sdk/src/validation.ts
index e7edc21fc..8872b667e 100644
--- a/packages/sdk/src/validation.ts
+++ b/packages/sdk/src/validation.ts
@@ -1,4 +1,11 @@
-import type { DataModel, DataModelAttribute, DataModelFieldAttribute } from './ast';
+import {
+    isDataModel,
+    isTypeDef,
+    type DataModel,
+    type DataModelAttribute,
+    type DataModelFieldAttribute,
+    type TypeDef,
+} from './ast';
 
 function isValidationAttribute(attr: DataModelAttribute | DataModelFieldAttribute) {
     return attr.decl.ref?.attributes.some((attr) => attr.decl.$refText === '@@@validation');
@@ -8,12 +15,30 @@ function isValidationAttribute(attr: DataModelAttribute | DataModelFieldAttribut
  * Returns if the given model contains any data validation rules (both at the model
  * level and at the field level).
  */
-export function hasValidationAttributes(model: DataModel) {
-    if (model.attributes.some((attr) => isValidationAttribute(attr))) {
-        return true;
+export function hasValidationAttributes(
+    decl: DataModel | TypeDef,
+    seen: Set<DataModel | TypeDef> = new Set()
+): boolean {
+    if (seen.has(decl)) {
+        return false;
+    }
+    seen.add(decl);
+
+    if (isDataModel(decl)) {
+        if (decl.attributes.some((attr) => isValidationAttribute(attr))) {
+            return true;
+        }
     }
 
-    if (model.fields.some((field) => field.attributes.some((attr) => isValidationAttribute(attr)))) {
+    if (
+        decl.fields.some((field) => {
+            if (isTypeDef(field.type.reference?.ref)) {
+                return hasValidationAttributes(field.type.reference?.ref);
+            } else {
+                return field.attributes.some((attr) => isValidationAttribute(attr));
+            }
+        })
+    ) {
         return true;
     }
 
diff --git a/tests/integration/tests/enhancements/json/crud.test.ts b/tests/integration/tests/enhancements/json/crud.test.ts
new file mode 100644
index 000000000..af3705a95
--- /dev/null
+++ b/tests/integration/tests/enhancements/json/crud.test.ts
@@ -0,0 +1,270 @@
+import { createPostgresDb, dropPostgresDb, loadSchema } from '@zenstackhq/testtools';
+
+describe('Json field CRUD', () => {
+    let dbUrl: string;
+    let prisma: any;
+
+    beforeEach(async () => {
+        dbUrl = await createPostgresDb('json-field-typing');
+    });
+
+    afterEach(async () => {
+        if (prisma) {
+            await prisma.$disconnect();
+        }
+        await dropPostgresDb(dbUrl);
+    });
+
+    it('works with simple cases', async () => {
+        const params = await loadSchema(
+            `
+            type Address {
+                city String
+            }
+
+            type Profile {
+                age Int
+                address Address?
+            }
+            
+            model User {
+                id Int @id @default(autoincrement())
+                profile Profile @json
+                posts Post[]
+            }
+
+            model Post {
+                id Int @id @default(autoincrement())
+                title String
+                user User @relation(fields: [userId], references: [id])
+                userId Int
+            }
+            `,
+            {
+                provider: 'postgresql',
+                dbUrl,
+                enhancements: ['validation'],
+            }
+        );
+
+        prisma = params.prisma;
+        const db = params.enhance();
+
+        // expecting object
+        await expect(db.user.create({ data: { profile: 1 } })).toBeRejectedByPolicy();
+        await expect(db.user.create({ data: { profile: [{ age: 18 }] } })).toBeRejectedByPolicy();
+        await expect(db.user.create({ data: { profile: { myAge: 18 } } })).toBeRejectedByPolicy();
+        await expect(db.user.create({ data: { profile: { address: { city: 'NY' } } } })).toBeRejectedByPolicy();
+        await expect(db.user.create({ data: { profile: { age: 18, address: { x: 1 } } } })).toBeRejectedByPolicy();
+
+        await expect(
+            db.user.create({ data: { profile: { age: 18 }, posts: { create: { title: 'Post1' } } } })
+        ).resolves.toMatchObject({
+            profile: { age: 18 },
+        });
+        await expect(
+            db.user.create({
+                data: { profile: { age: 20, address: { city: 'NY' } }, posts: { create: { title: 'Post1' } } },
+            })
+        ).resolves.toMatchObject({
+            profile: { age: 20, address: { city: 'NY' } },
+        });
+    });
+
+    it('works with array', async () => {
+        const params = await loadSchema(
+            `
+            type Address {
+                city String
+            }
+
+            type Profile {
+                age Int
+                address Address?
+            }
+            
+            model User {
+                id Int @id @default(autoincrement())
+                profiles Profile[] @json
+                @@allow('all', true)
+            }
+            `,
+            {
+                provider: 'postgresql',
+                dbUrl,
+            }
+        );
+
+        prisma = params.prisma;
+        const db = params.enhance();
+
+        // expecting array
+        await expect(
+            db.user.create({ data: { profiles: { age: 18, address: { city: 'NY' } } } })
+        ).toBeRejectedByPolicy();
+
+        await expect(
+            db.user.create({ data: { profiles: [{ age: 18, address: { city: 'NY' } }] } })
+        ).resolves.toMatchObject({
+            profiles: expect.arrayContaining([expect.objectContaining({ age: 18, address: { city: 'NY' } })]),
+        });
+    });
+
+    it('respects validation rules', async () => {
+        const params = await loadSchema(
+            `
+            type Address {
+                city String @length(2, 10)
+            }
+
+            type Profile {
+                age Int @gte(18)
+                address Address?
+            }
+            
+            model User {
+                id Int @id @default(autoincrement())
+                profile Profile @json
+                foo Foo?
+                @@allow('all', true)
+            }
+
+            model Foo {
+                id Int @id @default(autoincrement())
+                user User @relation(fields: [userId], references: [id])
+                userId Int @unique
+                @@allow('all', true)
+            }
+            `,
+            {
+                provider: 'postgresql',
+                dbUrl,
+            }
+        );
+
+        prisma = params.prisma;
+        const db = params.enhance();
+
+        // create
+        await expect(db.user.create({ data: { profile: { age: 10 } } })).toBeRejectedByPolicy();
+        await expect(db.user.create({ data: { profile: { age: 18, address: { city: 'N' } } } })).toBeRejectedByPolicy();
+        const u1 = await db.user.create({ data: { profile: { age: 18, address: { city: 'NY' } } } });
+        expect(u1).toMatchObject({
+            profile: { age: 18, address: { city: 'NY' } },
+        });
+
+        // update
+        await expect(db.user.update({ where: { id: u1.id }, data: { profile: { age: 10 } } })).toBeRejectedByPolicy();
+        await expect(
+            db.user.update({ where: { id: u1.id }, data: { profile: { age: 20, address: { city: 'B' } } } })
+        ).toBeRejectedByPolicy();
+        await expect(
+            db.user.update({ where: { id: u1.id }, data: { profile: { age: 20, address: { city: 'BJ' } } } })
+        ).resolves.toMatchObject({
+            profile: { age: 20, address: { city: 'BJ' } },
+        });
+
+        // nested create
+        await expect(db.foo.create({ data: { user: { create: { profile: { age: 10 } } } } })).toBeRejectedByPolicy();
+        await expect(db.foo.create({ data: { user: { create: { profile: { age: 20 } } } } })).toResolveTruthy();
+
+        // upsert
+        await expect(
+            db.user.upsert({ where: { id: 10 }, create: { id: 10, profile: { age: 10 } }, update: {} })
+        ).toBeRejectedByPolicy();
+        await expect(
+            db.user.upsert({ where: { id: 10 }, create: { id: 10, profile: { age: 20 } }, update: {} })
+        ).toResolveTruthy();
+        await expect(
+            db.user.upsert({
+                where: { id: 10 },
+                create: { id: 10, profile: { age: 20 } },
+                update: { profile: { age: 10 } },
+            })
+        ).toBeRejectedByPolicy();
+        await expect(
+            db.user.upsert({
+                where: { id: 10 },
+                create: { id: 10, profile: { age: 20 } },
+                update: { profile: { age: 20 } },
+            })
+        ).toResolveTruthy();
+    });
+
+    it('respects @default', async () => {
+        const params = await loadSchema(
+            `
+            type Address {
+                state String
+                city String @default('Issaquah')
+            }
+
+            type Profile {
+                createdAt DateTime @default(now())
+                address Address?
+            }
+            
+            model User {
+                id Int @id @default(autoincrement())
+                profile Profile @json
+                @@allow('all', true)
+            }
+            `,
+            {
+                provider: 'postgresql',
+                dbUrl,
+            }
+        );
+
+        prisma = params.prisma;
+        const db = params.enhance();
+
+        // default value
+        await expect(db.user.create({ data: { profile: { address: { state: 'WA' } } } })).resolves.toMatchObject({
+            profile: { address: { state: 'WA', city: 'Issaquah' }, createdAt: expect.any(Date) },
+        });
+
+        // override default
+        await expect(
+            db.user.create({ data: { profile: { address: { state: 'WA', city: 'Seattle' } } } })
+        ).resolves.toMatchObject({
+            profile: { address: { state: 'WA', city: 'Seattle' } },
+        });
+    });
+
+    it('works auth() in @default', async () => {
+        const params = await loadSchema(
+            `
+            type NestedProfile {
+                userId Int @default(auth().id)
+            }
+
+            type Profile {
+                ownerId Int @default(auth().id)
+                nested NestedProfile
+            }
+            
+            model User {
+                id Int @id @default(autoincrement())
+                profile Profile @json
+                @@allow('all', true)
+            }
+            `,
+            {
+                provider: 'postgresql',
+                dbUrl,
+            }
+        );
+
+        prisma = params.prisma;
+
+        const db = params.enhance({ id: 1 });
+        const u1 = await db.user.create({ data: { profile: { nested: {} } } });
+        expect(u1.profile.ownerId).toBe(1);
+        expect(u1.profile.nested.userId).toBe(1);
+
+        const u2 = await db.user.create({ data: { profile: { ownerId: 2, nested: { userId: 3 } } } });
+        expect(u2.profile.ownerId).toBe(2);
+        expect(u2.profile.nested.userId).toBe(3);
+    });
+});
diff --git a/tests/integration/tests/enhancements/json/typing.test.ts b/tests/integration/tests/enhancements/json/typing.test.ts
new file mode 100644
index 000000000..1905a179e
--- /dev/null
+++ b/tests/integration/tests/enhancements/json/typing.test.ts
@@ -0,0 +1,181 @@
+import { loadSchema } from '@zenstackhq/testtools';
+
+describe('JSON field typing', () => {
+    it('works with simple field', async () => {
+        await loadSchema(
+            `
+            type Profile {
+                age Int @gt(0)
+            }
+            
+            model User {
+                id Int @id @default(autoincrement())
+                profile Profile @json
+                posts Post[]
+                @@allow('all', true)
+            }
+
+            model Post {
+                id Int @id @default(autoincrement())
+                title String
+                user User @relation(fields: [userId], references: [id])
+                userId Int
+            }
+            `,
+            {
+                provider: 'postgresql',
+                pushDb: false,
+                compile: true,
+                extraSourceFiles: [
+                    {
+                        name: 'main.ts',
+                        content: `
+import { enhance } from '.zenstack/enhance';
+import { PrismaClient } from '@prisma/client';
+const prisma = new PrismaClient();
+const db = enhance(prisma);
+
+async function main() {
+    const u = await db.user.create({ data: { profile: { age: 18 }, posts: { create: { title: 'Post1' }} } });
+    console.log(u.profile.age);
+    const u1 = await db.user.findUnique({ where: { id: u.id } });
+    console.log(u1?.profile.age);
+    const u2 = await db.user.findMany({include: { posts: true }});
+    console.log(u2[0].profile.age);
+}
+                `,
+                    },
+                ],
+            }
+        );
+    });
+
+    it('works with optional field', async () => {
+        await loadSchema(
+            `
+            type Profile {
+                age Int @gt(0)
+            }
+            
+            model User {
+                id Int @id @default(autoincrement())
+                profile Profile? @json
+                @@allow('all', true)
+            }
+            `,
+            {
+                provider: 'postgresql',
+                pushDb: false,
+                compile: true,
+                extraSourceFiles: [
+                    {
+                        name: 'main.ts',
+                        content: `
+import { enhance } from '.zenstack/enhance';
+import { PrismaClient } from '@prisma/client';
+const prisma = new PrismaClient();
+const db = enhance(prisma);
+
+async function main() {
+    const u = await db.user.create({ data: { profile: { age: 18 } } });
+    console.log(u.profile?.age);
+    const u1 = await db.user.findUnique({ where: { id: u.id } });
+    console.log(u1?.profile?.age);
+    const u2 = await db.user.findMany();
+    console.log(u2[0].profile?.age);
+}
+                `,
+                    },
+                ],
+            }
+        );
+    });
+
+    it('works with array field', async () => {
+        await loadSchema(
+            `
+            type Profile {
+                age Int @gt(0)
+            }
+            
+            model User {
+                id Int @id @default(autoincrement())
+                profiles Profile[] @json
+                @@allow('all', true)
+            }
+            `,
+            {
+                provider: 'postgresql',
+                pushDb: false,
+                compile: true,
+                extraSourceFiles: [
+                    {
+                        name: 'main.ts',
+                        content: `
+import { enhance } from '.zenstack/enhance';
+import { PrismaClient } from '@prisma/client';
+const prisma = new PrismaClient();
+const db = enhance(prisma);
+
+async function main() {
+    const u = await db.user.create({ data: { profiles: [{ age: 18 }] } });
+    console.log(u.profiles[0].age);
+    const u1 = await db.user.findUnique({ where: { id: u.id } });
+    console.log(u1?.profiles[0].age);
+    const u2 = await db.user.findMany();
+    console.log(u2[0].profiles[0].age);
+}
+                `,
+                    },
+                ],
+            }
+        );
+    });
+
+    it('works with type nesting', async () => {
+        await loadSchema(
+            `
+            type Profile {
+                age Int @gt(0)
+                address Address?
+            }
+
+            type Address {
+                city String
+            }
+            
+            model User {
+                id Int @id @default(autoincrement())
+                profile Profile @json
+                @@allow('all', true)
+            }
+            `,
+            {
+                provider: 'postgresql',
+                pushDb: false,
+                compile: true,
+                extraSourceFiles: [
+                    {
+                        name: 'main.ts',
+                        content: `
+import { enhance } from '.zenstack/enhance';
+import { PrismaClient } from '@prisma/client';
+const prisma = new PrismaClient();
+const db = enhance(prisma);
+
+async function main() {
+    const u = await db.user.create({ data: { profile: { age: 18, address: { city: 'Issaquah' } } } });
+    console.log(u.profile.address?.city);
+    const u1 = await db.user.findUnique({ where: { id: u.id } });
+    console.log(u1?.profile.address?.city);
+    const u2 = await db.user.findMany();
+    console.log(u2[0].profile.address?.city);
+    await db.user.create({ data: { profile: { age: 20 } } });
+}
+                `,
+                    },
+                ],
+            }
+        );
+    });
+});
diff --git a/tests/integration/tests/enhancements/json/validation.test.ts b/tests/integration/tests/enhancements/json/validation.test.ts
new file mode 100644
index 000000000..2643056fe
--- /dev/null
+++ b/tests/integration/tests/enhancements/json/validation.test.ts
@@ -0,0 +1,39 @@
+import { loadModelWithError } from '@zenstackhq/testtools';
+
+describe('JSON field typing', () => {
+    it('is only supported by postgres', async () => {
+        await expect(
+            loadModelWithError(
+                `
+            type Profile {
+                age Int @gt(0)
+            }
+            
+            model User {
+                id Int @id @default(autoincrement())
+                profile Profile @json
+                @@allow('all', true)
+            }
+            `
+            )
+        ).resolves.toContain('Custom-typed field is only supported with "postgresql" provider');
+    });
+
+    it('requires field to have @json attribute', async () => {
+        await expect(
+            loadModelWithError(
+                `
+            type Profile {
+                age Int @gt(0)
+            }
+            
+            model User {
+                id Int @id @default(autoincrement())
+                profile Profile
+                @@allow('all', true)
+            }
+            `
+            )
+        ).resolves.toContain('Custom-typed field must have @json attribute');
+    });
+});
diff --git a/tests/integration/tests/plugins/zod.test.ts b/tests/integration/tests/plugins/zod.test.ts
index 5af7f4077..aba94261c 100644
--- a/tests/integration/tests/plugins/zod.test.ts
+++ b/tests/integration/tests/plugins/zod.test.ts
@@ -1025,4 +1025,60 @@ describe('Zod plugin tests', () => {
             )
         ).rejects.toThrow(/Invalid mode/);
     });
+
+    it('supports type def', async () => {
+        const { zodSchemas } = await loadSchema(
+            `
+            datasource db {
+                provider = 'postgresql'
+                url = env('DATABASE_URL')
+            }
+            
+            generator js {
+                provider = 'prisma-client-js'
+            }
+
+            plugin zod {
+                provider = '@core/zod'
+            }
+
+            type Address {
+                city String @length(2, 20)
+            }
+
+            type Profile {
+                age Int @gte(18)
+                address Address?
+            }
+        
+            model User {
+                id Int @id @default(autoincrement())
+                profile Profile @json
+            }
+            `,
+            { addPrelude: false, pushDb: false }
+        );
+
+        const schemas = zodSchemas.models;
+
+        let parsed = schemas.ProfileSchema.safeParse({ age: 18, address: { city: 'NY' } });
+        expect(parsed.success).toBeTruthy();
+        expect(parsed.data).toEqual({ age: 18, address: { city: 'NY' } });
+
+        expect(schemas.ProfileSchema.safeParse({ age: 18 })).toMatchObject({ success: true });
+        expect(schemas.ProfileSchema.safeParse({ age: 10 })).toMatchObject({ success: false });
+        expect(schemas.ProfileSchema.safeParse({ address: { city: 'NY' } })).toMatchObject({ success: false });
+        expect(schemas.ProfileSchema.safeParse({ address: { age: 18, city: 'N' } })).toMatchObject({ success: false });
+
+        expect(schemas.UserSchema.safeParse({ id: 1, profile: { age: 18 } })).toMatchObject({ success: true });
+        expect(schemas.UserSchema.safeParse({ id: 1, profile: { age: 10 } })).toMatchObject({ success: false });
+
+        const objectSchemas = zodSchemas.objects;
+        expect(objectSchemas.UserCreateInputObjectSchema.safeParse({ profile: { age: 18 } })).toMatchObject({
+            success: true,
+        });
+        expect(objectSchemas.UserCreateInputObjectSchema.safeParse({ profile: { age: 10 } })).toMatchObject({
+            success: false,
+        });
+    });
 });