diff --git a/compiler/src/model/metamodel.ts b/compiler/src/model/metamodel.ts
index 3802951a3c..8c28e2847d 100644
--- a/compiler/src/model/metamodel.ts
+++ b/compiler/src/model/metamodel.ts
@@ -209,6 +209,7 @@ export class Container extends VariantBase {
 
 export class Untagged extends VariantBase {
   kind: 'untagged'
+  untyped_variant: Inherits
 }
 
 /**
diff --git a/compiler/src/model/utils.ts b/compiler/src/model/utils.ts
index dc4f3787a8..ed9f92ae4c 100644
--- a/compiler/src/model/utils.ts
+++ b/compiler/src/model/utils.ts
@@ -1110,24 +1110,34 @@ export function parseVariantsTag (jsDoc: JSDoc[]): model.Variants | undefined {
     }
   }
 
+  if (type === 'internal') {
+    const pairs = parseKeyValues(jsDoc, values, 'tag', 'default')
+    assert(jsDoc, typeof pairs.tag === 'string', 'Internal variant requires a tag definition')
+    return {
+      kind: 'internal_tag',
+      nonExhaustive: nonExhaustive,
+      tag: pairs.tag,
+      defaultTag: pairs.default
+    }
+  }
+
   if (type === 'untagged') {
+    const pairs = parseKeyValues(jsDoc, values, 'untyped')
+    assert(jsDoc, typeof pairs.untyped === 'string', 'Untagged variant requires an untyped definition')
+    const fqn = pairs.untyped.split('.')
     return {
       kind: 'untagged',
-      nonExhaustive: nonExhaustive
+      nonExhaustive: nonExhaustive,
+      untyped_variant: {
+        type: {
+          namespace: fqn.slice(0, fqn.length - 1).join('.'),
+          name: fqn[fqn.length - 1]
+        }
+      }
     }
   }
 
-  assert(jsDoc, type === 'internal', `Bad variant type: ${type}`)
-
-  const pairs = parseKeyValues(jsDoc, values, 'tag', 'default')
-  assert(jsDoc, typeof pairs.tag === 'string', 'Internal variant requires a tag definition')
-
-  return {
-    kind: 'internal_tag',
-    nonExhaustive: nonExhaustive,
-    tag: pairs.tag,
-    defaultTag: pairs.default
-  }
+  assert(jsDoc, false, `Bad variant type: ${type}`)
 }
 
 /**
diff --git a/compiler/src/steps/validate-model.ts b/compiler/src/steps/validate-model.ts
index 5c9b9a94ed..269ef660f6 100644
--- a/compiler/src/steps/validate-model.ts
+++ b/compiler/src/steps/validate-model.ts
@@ -559,14 +559,14 @@ export default async function validateModel (apiModel: model.Model, restSpec: Ma
       if (typeDef.type.kind !== 'union_of') {
         modelError('The "variants" tag only applies to unions')
       } else {
-        validateTaggedUnion(typeDef.type, typeDef.variants)
+        validateTaggedUnion(typeDef.name, typeDef.type, typeDef.variants)
       }
     } else {
       validateValueOf(typeDef.type, openGenerics)
     }
   }
 
-  function validateTaggedUnion (valueOf: model.UnionOf, variants: model.InternalTag | model.ExternalTag | model.Untagged): void {
+  function validateTaggedUnion (parentName: TypeName, valueOf: model.UnionOf, variants: model.InternalTag | model.ExternalTag | model.Untagged): void {
     if (variants.kind === 'external_tag') {
       // All items must have a 'variant' attribute
       const items = flattenUnionMembers(valueOf)
@@ -611,9 +611,20 @@ export default async function validateModel (apiModel: model.Model, restSpec: Ma
 
       validateValueOf(valueOf, new Set())
     } else if (variants.kind === 'untagged') {
-      const items = flattenUnionMembers(valueOf)
+      if (fqn(parentName) !== '_types.query_dsl:DecayFunction' &&
+          fqn(parentName) !== '_types.query_dsl:DistanceFeatureQuery' &&
+          fqn(parentName) !== '_types.query_dsl:RangeQuery') {
+        throw new Error(`Please contact the devtools team before adding new untagged variant ${fqn(parentName)}`)
+      }
+
+      const untyped_variant = getTypeDef(variants.untyped_variant.type)
+      if (untyped_variant == null) {
+        modelError(`Type ${fqn(variants.untyped_variant.type)} not found`)
+      }
 
+      const items = flattenUnionMembers(valueOf)
       const baseTypes = new Set<string>()
+      let found_untyped = false;
 
       for (const item of items) {
         if (item.kind !== 'instance_of') {
@@ -628,6 +639,10 @@ export default async function validateModel (apiModel: model.Model, restSpec: Ma
               modelError(`Type ${fqn(item.type)} must be an interface to be used in an untagged union`)
               continue
             }
+            
+            if (fqn(item.type) === fqn(untyped_variant!.name)) {
+              found_untyped = true
+            }
 
             if (type.inherits == null) {
               modelError(`Type ${fqn(item.type)} must derive from a base type to be used in an untagged union`)
@@ -657,6 +672,10 @@ export default async function validateModel (apiModel: model.Model, restSpec: Ma
       if (baseTypes.size !== 1) {
         modelError('All items of an untagged union must derive from the same common base type')
       }
+      
+      if (!found_untyped) {
+        modelError('The untyped variant of an untagged variant must be contained in the union items')
+      }
     }
   }
 
diff --git a/docs/modeling-guide.md b/docs/modeling-guide.md
index fab7329982..123a844acb 100644
--- a/docs/modeling-guide.md
+++ b/docs/modeling-guide.md
@@ -455,16 +455,17 @@ For example:
 ```ts
 export class MyTypeBase<T1, T2, ...> { ... }
 
+export class MyTypeUntyped extends MyTypeBase<UserDefinedValue> {}
 export class MyTypeSpecialized1 extends MyTypeBase<int> {}
 export class MyTypeSpecialized2 extends MyTypeBase<string> {}
 export class MyTypeSpecialized3 extends MyTypeBase<bool> {}
 
 /**
- * @codegen_names mytype1, mytypet2, mytype3 
- * @variant untagged
+ * @codegen_names untyped, mytype1, mytypet2, mytype3 
+ * @variant untagged untyped=_types.MyTypeUntyped
  */
 // Note: deserialization depends on value types
-export type MyType = MyTypeSpecialized1 | MyTypeSpecialized2 | MyTypeSpecialized3 
+export type MyType = MyTypeUntyped | MyTypeSpecialized1 | MyTypeSpecialized2 | MyTypeSpecialized3 
 ```
 
 ### Shortcut properties
diff --git a/output/schema/schema.json b/output/schema/schema.json
index 6a7ea111e5..7947ab75dc 100644
--- a/output/schema/schema.json
+++ b/output/schema/schema.json
@@ -75116,7 +75116,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/compound.ts#L28-L52"
+      "specLocation": "_types/query_dsl/compound.ts#L29-L53"
     },
     {
       "inherits": {
@@ -75168,7 +75168,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/compound.ts#L54-L67"
+      "specLocation": "_types/query_dsl/compound.ts#L55-L68"
     },
     {
       "kind": "enum",
@@ -75434,57 +75434,45 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/compound.ts#L69-L76"
+      "specLocation": "_types/query_dsl/compound.ts#L70-L77"
     },
     {
       "attachedBehaviors": [
         "AdditionalProperty"
       ],
-      "behaviors": [
-        {
-          "generics": [
-            {
-              "kind": "instance_of",
-              "type": {
-                "name": "Field",
-                "namespace": "_types"
-              }
-            },
-            {
-              "generics": [
-                {
-                  "kind": "instance_of",
-                  "type": {
-                    "name": "DateMath",
-                    "namespace": "_types"
-                  }
-                },
-                {
-                  "kind": "instance_of",
-                  "type": {
-                    "name": "Duration",
-                    "namespace": "_types"
-                  }
+      "inherits": {
+        "generics": [
+          {
+            "kind": "instance_of",
+            "type": {
+              "name": "Field",
+              "namespace": "_types"
+            }
+          },
+          {
+            "generics": [
+              {
+                "kind": "instance_of",
+                "type": {
+                  "name": "DateMath",
+                  "namespace": "_types"
+                }
+              },
+              {
+                "kind": "instance_of",
+                "type": {
+                  "name": "Duration",
+                  "namespace": "_types"
                 }
-              ],
-              "kind": "instance_of",
-              "type": {
-                "name": "DecayPlacement",
-                "namespace": "_types.query_dsl"
               }
+            ],
+            "kind": "instance_of",
+            "type": {
+              "name": "DecayPlacement",
+              "namespace": "_types.query_dsl"
             }
-          ],
-          "meta": {
-            "key": "field",
-            "value": "placement"
-          },
-          "type": {
-            "name": "AdditionalProperty",
-            "namespace": "_spec_utils"
           }
-        }
-      ],
-      "inherits": {
+        ],
         "type": {
           "name": "DecayFunctionBase",
           "namespace": "_types.query_dsl"
@@ -75496,7 +75484,7 @@
         "namespace": "_types.query_dsl"
       },
       "properties": [],
-      "specLocation": "_types/query_dsl/compound.ts#L189-L194"
+      "specLocation": "_types/query_dsl/compound.ts#L190-L190"
     },
     {
       "inherits": {
@@ -75527,10 +75515,19 @@
         "namespace": "_types.query_dsl"
       },
       "properties": [],
-      "specLocation": "_types/query_dsl/specialized.ts#L67-L70"
+      "specLocation": "_types/query_dsl/specialized.ts#L72-L75"
     },
     {
       "inherits": {
+        "generics": [
+          {
+            "kind": "instance_of",
+            "type": {
+              "name": "DateMath",
+              "namespace": "_types"
+            }
+          }
+        ],
         "type": {
           "name": "RangeQueryBase",
           "namespace": "_types.query_dsl"
@@ -75542,100 +75539,6 @@
         "namespace": "_types.query_dsl"
       },
       "properties": [
-        {
-          "description": "Greater than.",
-          "name": "gt",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "DateMath",
-              "namespace": "_types"
-            }
-          }
-        },
-        {
-          "description": "Greater than or equal to.",
-          "name": "gte",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "DateMath",
-              "namespace": "_types"
-            }
-          }
-        },
-        {
-          "description": "Less than.",
-          "name": "lt",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "DateMath",
-              "namespace": "_types"
-            }
-          }
-        },
-        {
-          "description": "Less than or equal to.",
-          "name": "lte",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "DateMath",
-              "namespace": "_types"
-            }
-          }
-        },
-        {
-          "name": "from",
-          "required": false,
-          "type": {
-            "items": [
-              {
-                "kind": "instance_of",
-                "type": {
-                  "name": "DateMath",
-                  "namespace": "_types"
-                }
-              },
-              {
-                "kind": "instance_of",
-                "type": {
-                  "name": "null",
-                  "namespace": "_builtins"
-                }
-              }
-            ],
-            "kind": "union_of"
-          }
-        },
-        {
-          "name": "to",
-          "required": false,
-          "type": {
-            "items": [
-              {
-                "kind": "instance_of",
-                "type": {
-                  "name": "DateMath",
-                  "namespace": "_types"
-                }
-              },
-              {
-                "kind": "instance_of",
-                "type": {
-                  "name": "null",
-                  "namespace": "_builtins"
-                }
-              }
-            ],
-            "kind": "union_of"
-          }
-        },
         {
           "description": "Date format used to convert `date` values in the query.",
           "name": "format",
@@ -75661,10 +75564,11 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/term.ts#L116-L143"
+      "specLocation": "_types/query_dsl/term.ts#L146-L155"
     },
     {
       "codegenNames": [
+        "untyped",
         "date",
         "numeric",
         "geo"
@@ -75674,9 +75578,16 @@
         "name": "DecayFunction",
         "namespace": "_types.query_dsl"
       },
-      "specLocation": "_types/query_dsl/compound.ts#L203-L208",
+      "specLocation": "_types/query_dsl/compound.ts#L193-L202",
       "type": {
         "items": [
+          {
+            "kind": "instance_of",
+            "type": {
+              "name": "UntypedDecayFunction",
+              "namespace": "_types.query_dsl"
+            }
+          },
           {
             "kind": "instance_of",
             "type": {
@@ -75700,9 +75611,59 @@
           }
         ],
         "kind": "union_of"
+      },
+      "variants": {
+        "kind": "untagged",
+        "untyped_variant": {
+          "type": {
+            "name": "UntypedDecayFunction",
+            "namespace": "_types.query_dsl"
+          }
+        }
       }
     },
     {
+      "attachedBehaviors": [
+        "AdditionalProperty"
+      ],
+      "behaviors": [
+        {
+          "generics": [
+            {
+              "kind": "instance_of",
+              "type": {
+                "name": "TOrigin",
+                "namespace": "_types.query_dsl.DecayFunctionBase"
+              }
+            },
+            {
+              "kind": "instance_of",
+              "type": {
+                "name": "TScale",
+                "namespace": "_types.query_dsl.DecayFunctionBase"
+              }
+            }
+          ],
+          "meta": {
+            "key": "field",
+            "value": "placement"
+          },
+          "type": {
+            "name": "AdditionalProperty",
+            "namespace": "_spec_utils"
+          }
+        }
+      ],
+      "generics": [
+        {
+          "name": "TOrigin",
+          "namespace": "_types.query_dsl.DecayFunctionBase"
+        },
+        {
+          "name": "TScale",
+          "namespace": "_types.query_dsl.DecayFunctionBase"
+        }
+      ],
       "kind": "interface",
       "name": {
         "name": "DecayFunctionBase",
@@ -75723,7 +75684,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/compound.ts#L174-L180"
+      "specLocation": "_types/query_dsl/compound.ts#L175-L186"
     },
     {
       "generics": [
@@ -75793,7 +75754,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/compound.ts#L153-L172"
+      "specLocation": "_types/query_dsl/compound.ts#L154-L173"
     },
     {
       "inherits": {
@@ -75837,10 +75798,11 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/compound.ts#L78-L90"
+      "specLocation": "_types/query_dsl/compound.ts#L79-L91"
     },
     {
       "codegenNames": [
+        "untyped",
         "geo",
         "date"
       ],
@@ -75849,9 +75811,16 @@
         "name": "DistanceFeatureQuery",
         "namespace": "_types.query_dsl"
       },
-      "specLocation": "_types/query_dsl/specialized.ts#L72-L76",
+      "specLocation": "_types/query_dsl/specialized.ts#L77-L85",
       "type": {
         "items": [
+          {
+            "kind": "instance_of",
+            "type": {
+              "name": "UntypedDistanceFeatureQuery",
+              "namespace": "_types.query_dsl"
+            }
+          },
           {
             "kind": "instance_of",
             "type": {
@@ -75868,6 +75837,15 @@
           }
         ],
         "kind": "union_of"
+      },
+      "variants": {
+        "kind": "untagged",
+        "untyped_variant": {
+          "type": {
+            "name": "UntypedDistanceFeatureQuery",
+            "namespace": "_types.query_dsl"
+          }
+        }
       }
     },
     {
@@ -75958,7 +75936,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/term.ts#L36-L41"
+      "specLocation": "_types/query_dsl/term.ts#L37-L42"
     },
     {
       "description": "A reference to a field with formatting instructions on how to return the value",
@@ -76113,7 +76091,7 @@
         "name": "FieldValueFactorModifier",
         "namespace": "_types.query_dsl"
       },
-      "specLocation": "_types/query_dsl/compound.ts#L307-L350"
+      "specLocation": "_types/query_dsl/compound.ts#L301-L344"
     },
     {
       "kind": "interface",
@@ -76172,7 +76150,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/compound.ts#L132-L151"
+      "specLocation": "_types/query_dsl/compound.ts#L133-L152"
     },
     {
       "kind": "enum",
@@ -76206,7 +76184,7 @@
         "name": "FunctionBoostMode",
         "namespace": "_types.query_dsl"
       },
-      "specLocation": "_types/query_dsl/compound.ts#L279-L305"
+      "specLocation": "_types/query_dsl/compound.ts#L273-L299"
     },
     {
       "esQuirk": "this container is valid without a variant. Despite being documented as a function, 'weight'\nis actually a container property that can be combined with a function. Comment in the ES code\n(SearchModule#registerScoreFunctions) says: Weight doesn't have its own parser, so every function\nsupports it out of the box. Can be a single function too when not associated to any other function,\nwhich is why it needs to be registered manually here.",
@@ -76313,7 +76291,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/compound.ts#L210-L250",
+      "specLocation": "_types/query_dsl/compound.ts#L204-L244",
       "variants": {
         "kind": "container"
       }
@@ -76350,7 +76328,7 @@
         "name": "FunctionScoreMode",
         "namespace": "_types.query_dsl"
       },
-      "specLocation": "_types/query_dsl/compound.ts#L252-L277"
+      "specLocation": "_types/query_dsl/compound.ts#L246-L271"
     },
     {
       "inherits": {
@@ -76443,7 +76421,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/compound.ts#L92-L118"
+      "specLocation": "_types/query_dsl/compound.ts#L93-L119"
     },
     {
       "inherits": {
@@ -76559,7 +76537,7 @@
         }
       ],
       "shortcutProperty": "value",
-      "specLocation": "_types/query_dsl/term.ts#L43-L78"
+      "specLocation": "_types/query_dsl/term.ts#L44-L79"
     },
     {
       "attachedBehaviors": [
@@ -76653,51 +76631,39 @@
       "attachedBehaviors": [
         "AdditionalProperty"
       ],
-      "behaviors": [
-        {
-          "generics": [
-            {
-              "kind": "instance_of",
-              "type": {
-                "name": "Field",
-                "namespace": "_types"
-              }
-            },
-            {
-              "generics": [
-                {
-                  "kind": "instance_of",
-                  "type": {
-                    "name": "GeoLocation",
-                    "namespace": "_types"
-                  }
-                },
-                {
-                  "kind": "instance_of",
-                  "type": {
-                    "name": "Distance",
-                    "namespace": "_types"
-                  }
+      "inherits": {
+        "generics": [
+          {
+            "kind": "instance_of",
+            "type": {
+              "name": "Field",
+              "namespace": "_types"
+            }
+          },
+          {
+            "generics": [
+              {
+                "kind": "instance_of",
+                "type": {
+                  "name": "GeoLocation",
+                  "namespace": "_types"
+                }
+              },
+              {
+                "kind": "instance_of",
+                "type": {
+                  "name": "Distance",
+                  "namespace": "_types"
                 }
-              ],
-              "kind": "instance_of",
-              "type": {
-                "name": "DecayPlacement",
-                "namespace": "_types.query_dsl"
               }
+            ],
+            "kind": "instance_of",
+            "type": {
+              "name": "DecayPlacement",
+              "namespace": "_types.query_dsl"
             }
-          ],
-          "meta": {
-            "key": "field",
-            "value": "placement"
-          },
-          "type": {
-            "name": "AdditionalProperty",
-            "namespace": "_spec_utils"
           }
-        }
-      ],
-      "inherits": {
+        ],
         "type": {
           "name": "DecayFunctionBase",
           "namespace": "_types.query_dsl"
@@ -76709,7 +76675,7 @@
         "namespace": "_types.query_dsl"
       },
       "properties": [],
-      "specLocation": "_types/query_dsl/compound.ts#L196-L201"
+      "specLocation": "_types/query_dsl/compound.ts#L191-L191"
     },
     {
       "inherits": {
@@ -76740,7 +76706,7 @@
         "namespace": "_types.query_dsl"
       },
       "properties": [],
-      "specLocation": "_types/query_dsl/specialized.ts#L62-L65"
+      "specLocation": "_types/query_dsl/specialized.ts#L67-L70"
     },
     {
       "attachedBehaviors": [
@@ -77293,7 +77259,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/term.ts#L80-L85"
+      "specLocation": "_types/query_dsl/term.ts#L81-L86"
     },
     {
       "kind": "interface",
@@ -77974,7 +77940,7 @@
         "name": "Like",
         "namespace": "_types.query_dsl"
       },
-      "specLocation": "_types/query_dsl/specialized.ts#L186-L191",
+      "specLocation": "_types/query_dsl/specialized.ts#L195-L200",
       "type": {
         "items": [
           {
@@ -78106,7 +78072,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L162-L184"
+      "specLocation": "_types/query_dsl/specialized.ts#L171-L193"
     },
     {
       "inherits": {
@@ -78909,7 +78875,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L78-L160"
+      "specLocation": "_types/query_dsl/specialized.ts#L87-L169"
     },
     {
       "inherits": {
@@ -79176,7 +79142,7 @@
         "name": "MultiValueMode",
         "namespace": "_types.query_dsl"
       },
-      "specLocation": "_types/query_dsl/compound.ts#L352-L369"
+      "specLocation": "_types/query_dsl/compound.ts#L346-L363"
     },
     {
       "inherits": {
@@ -79260,6 +79226,15 @@
     },
     {
       "inherits": {
+        "generics": [
+          {
+            "kind": "instance_of",
+            "type": {
+              "name": "double",
+              "namespace": "_types"
+            }
+          }
+        ],
         "type": {
           "name": "RangeQueryBase",
           "namespace": "_types.query_dsl"
@@ -79270,60 +79245,24 @@
         "name": "NumberRangeQuery",
         "namespace": "_types.query_dsl"
       },
-      "properties": [
-        {
-          "description": "Greater than.",
-          "name": "gt",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "double",
-              "namespace": "_types"
-            }
-          }
-        },
-        {
-          "description": "Greater than or equal to.",
-          "name": "gte",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "double",
-              "namespace": "_types"
-            }
-          }
-        },
-        {
-          "description": "Less than.",
-          "name": "lt",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "double",
-              "namespace": "_types"
-            }
-          }
-        },
-        {
-          "description": "Less than or equal to.",
-          "name": "lte",
-          "required": false,
-          "type": {
+      "properties": [],
+      "specLocation": "_types/query_dsl/term.ts#L157-L157"
+    },
+    {
+      "attachedBehaviors": [
+        "AdditionalProperty"
+      ],
+      "inherits": {
+        "generics": [
+          {
             "kind": "instance_of",
             "type": {
-              "name": "double",
+              "name": "Field",
               "namespace": "_types"
             }
-          }
-        },
-        {
-          "name": "from",
-          "required": false,
-          "type": {
-            "items": [
+          },
+          {
+            "generics": [
               {
                 "kind": "instance_of",
                 "type": {
@@ -79331,92 +79270,21 @@
                   "namespace": "_types"
                 }
               },
-              {
-                "kind": "instance_of",
-                "type": {
-                  "name": "null",
-                  "namespace": "_builtins"
-                }
-              }
-            ],
-            "kind": "union_of"
-          }
-        },
-        {
-          "name": "to",
-          "required": false,
-          "type": {
-            "items": [
               {
                 "kind": "instance_of",
                 "type": {
                   "name": "double",
                   "namespace": "_types"
                 }
-              },
-              {
-                "kind": "instance_of",
-                "type": {
-                  "name": "null",
-                  "namespace": "_builtins"
-                }
               }
             ],
-            "kind": "union_of"
-          }
-        }
-      ],
-      "specLocation": "_types/query_dsl/term.ts#L145-L164"
-    },
-    {
-      "attachedBehaviors": [
-        "AdditionalProperty"
-      ],
-      "behaviors": [
-        {
-          "generics": [
-            {
-              "kind": "instance_of",
-              "type": {
-                "name": "Field",
-                "namespace": "_types"
-              }
-            },
-            {
-              "generics": [
-                {
-                  "kind": "instance_of",
-                  "type": {
-                    "name": "double",
-                    "namespace": "_types"
-                  }
-                },
-                {
-                  "kind": "instance_of",
-                  "type": {
-                    "name": "double",
-                    "namespace": "_types"
-                  }
-                }
-              ],
-              "kind": "instance_of",
-              "type": {
-                "name": "DecayPlacement",
-                "namespace": "_types.query_dsl"
-              }
+            "kind": "instance_of",
+            "type": {
+              "name": "DecayPlacement",
+              "namespace": "_types.query_dsl"
             }
-          ],
-          "meta": {
-            "key": "field",
-            "value": "placement"
-          },
-          "type": {
-            "name": "AdditionalProperty",
-            "namespace": "_spec_utils"
           }
-        }
-      ],
-      "inherits": {
+        ],
         "type": {
           "name": "DecayFunctionBase",
           "namespace": "_types.query_dsl"
@@ -79428,7 +79296,7 @@
         "namespace": "_types.query_dsl"
       },
       "properties": [],
-      "specLocation": "_types/query_dsl/compound.ts#L182-L187"
+      "specLocation": "_types/query_dsl/compound.ts#L189-L189"
     },
     {
       "kind": "enum",
@@ -79622,7 +79490,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L193-L230"
+      "specLocation": "_types/query_dsl/specialized.ts#L202-L239"
     },
     {
       "kind": "interface",
@@ -79656,7 +79524,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L253-L262"
+      "specLocation": "_types/query_dsl/specialized.ts#L262-L271"
     },
     {
       "inherits": {
@@ -79715,7 +79583,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L232-L251",
+      "specLocation": "_types/query_dsl/specialized.ts#L241-L260",
       "variants": {
         "kind": "container"
       }
@@ -79781,7 +79649,7 @@
         }
       ],
       "shortcutProperty": "value",
-      "specLocation": "_types/query_dsl/term.ts#L87-L106"
+      "specLocation": "_types/query_dsl/term.ts#L88-L107"
     },
     {
       "kind": "interface",
@@ -81272,22 +81140,30 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/compound.ts#L127-L130"
+      "specLocation": "_types/query_dsl/compound.ts#L128-L131"
     },
     {
       "codegenNames": [
+        "untyped",
         "date",
         "number",
-        "terms"
+        "term"
       ],
       "kind": "type_alias",
       "name": {
         "name": "RangeQuery",
         "namespace": "_types.query_dsl"
       },
-      "specLocation": "_types/query_dsl/term.ts#L187-L189",
+      "specLocation": "_types/query_dsl/term.ts#L161-L166",
       "type": {
         "items": [
+          {
+            "kind": "instance_of",
+            "type": {
+              "name": "UntypedRangeQuery",
+              "namespace": "_types.query_dsl"
+            }
+          },
           {
             "kind": "instance_of",
             "type": {
@@ -81305,15 +81181,30 @@
           {
             "kind": "instance_of",
             "type": {
-              "name": "TermsRangeQuery",
+              "name": "TermRangeQuery",
               "namespace": "_types.query_dsl"
             }
           }
         ],
         "kind": "union_of"
+      },
+      "variants": {
+        "kind": "untagged",
+        "untyped_variant": {
+          "type": {
+            "name": "UntypedRangeQuery",
+            "namespace": "_types.query_dsl"
+          }
+        }
       }
     },
     {
+      "generics": [
+        {
+          "name": "T",
+          "namespace": "_types.query_dsl.RangeQueryBase"
+        }
+      ],
       "inherits": {
         "type": {
           "name": "QueryBase",
@@ -81327,20 +81218,114 @@
       },
       "properties": [
         {
-          "description": "Indicates how the range query matches values for `range` fields.",
-          "name": "relation",
+          "description": "Indicates how the range query matches values for `range` fields.",
+          "name": "relation",
+          "required": false,
+          "serverDefault": "intersects",
+          "type": {
+            "kind": "instance_of",
+            "type": {
+              "name": "RangeRelation",
+              "namespace": "_types.query_dsl"
+            }
+          }
+        },
+        {
+          "description": "Greater than.",
+          "name": "gt",
+          "required": false,
+          "type": {
+            "kind": "instance_of",
+            "type": {
+              "name": "T",
+              "namespace": "_types.query_dsl.RangeQueryBase"
+            }
+          }
+        },
+        {
+          "description": "Greater than or equal to.",
+          "name": "gte",
+          "required": false,
+          "type": {
+            "kind": "instance_of",
+            "type": {
+              "name": "T",
+              "namespace": "_types.query_dsl.RangeQueryBase"
+            }
+          }
+        },
+        {
+          "description": "Less than.",
+          "name": "lt",
+          "required": false,
+          "type": {
+            "kind": "instance_of",
+            "type": {
+              "name": "T",
+              "namespace": "_types.query_dsl.RangeQueryBase"
+            }
+          }
+        },
+        {
+          "description": "Less than or equal to.",
+          "name": "lte",
+          "required": false,
+          "type": {
+            "kind": "instance_of",
+            "type": {
+              "name": "T",
+              "namespace": "_types.query_dsl.RangeQueryBase"
+            }
+          }
+        },
+        {
+          "name": "from",
+          "required": false,
+          "type": {
+            "items": [
+              {
+                "kind": "instance_of",
+                "type": {
+                  "name": "T",
+                  "namespace": "_types.query_dsl.RangeQueryBase"
+                }
+              },
+              {
+                "kind": "instance_of",
+                "type": {
+                  "name": "null",
+                  "namespace": "_builtins"
+                }
+              }
+            ],
+            "kind": "union_of"
+          }
+        },
+        {
+          "name": "to",
           "required": false,
-          "serverDefault": "intersects",
           "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "RangeRelation",
-              "namespace": "_types.query_dsl"
-            }
+            "items": [
+              {
+                "kind": "instance_of",
+                "type": {
+                  "name": "T",
+                  "namespace": "_types.query_dsl.RangeQueryBase"
+                }
+              },
+              {
+                "kind": "instance_of",
+                "type": {
+                  "name": "null",
+                  "namespace": "_builtins"
+                }
+              }
+            ],
+            "kind": "union_of"
           }
         }
       ],
-      "specLocation": "_types/query_dsl/term.ts#L108-L114"
+      "specLocation": "_types/query_dsl/term.ts#L109-L133"
     },
     {
       "kind": "enum",
@@ -81362,7 +81347,7 @@
         "name": "RangeRelation",
         "namespace": "_types.query_dsl"
       },
-      "specLocation": "_types/query_dsl/term.ts#L191-L204"
+      "specLocation": "_types/query_dsl/term.ts#L168-L181"
     },
     {
       "kind": "interface",
@@ -81371,7 +81356,7 @@
         "namespace": "_types.query_dsl"
       },
       "properties": [],
-      "specLocation": "_types/query_dsl/specialized.ts#L264-L264"
+      "specLocation": "_types/query_dsl/specialized.ts#L273-L273"
     },
     {
       "inherits": {
@@ -81386,7 +81371,7 @@
         "namespace": "_types.query_dsl"
       },
       "properties": [],
-      "specLocation": "_types/query_dsl/specialized.ts#L266-L266"
+      "specLocation": "_types/query_dsl/specialized.ts#L275-L275"
     },
     {
       "inherits": {
@@ -81414,7 +81399,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L268-L273"
+      "specLocation": "_types/query_dsl/specialized.ts#L277-L282"
     },
     {
       "inherits": {
@@ -81442,7 +81427,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L275-L280"
+      "specLocation": "_types/query_dsl/specialized.ts#L284-L289"
     },
     {
       "inherits": {
@@ -81482,7 +81467,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L282-L291"
+      "specLocation": "_types/query_dsl/specialized.ts#L291-L300"
     },
     {
       "inherits": {
@@ -81558,7 +81543,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L293-L316"
+      "specLocation": "_types/query_dsl/specialized.ts#L302-L325"
     },
     {
       "inherits": {
@@ -81650,7 +81635,7 @@
         }
       ],
       "shortcutProperty": "value",
-      "specLocation": "_types/query_dsl/term.ts#L206-L236"
+      "specLocation": "_types/query_dsl/term.ts#L183-L213"
     },
     {
       "inherits": {
@@ -81698,7 +81683,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L372-L376"
+      "specLocation": "_types/query_dsl/specialized.ts#L381-L385"
     },
     {
       "inherits": {
@@ -81726,7 +81711,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L318-L324"
+      "specLocation": "_types/query_dsl/specialized.ts#L327-L333"
     },
     {
       "kind": "interface",
@@ -81748,7 +81733,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/compound.ts#L120-L125"
+      "specLocation": "_types/query_dsl/compound.ts#L121-L126"
     },
     {
       "inherits": {
@@ -81800,7 +81785,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L326-L340"
+      "specLocation": "_types/query_dsl/specialized.ts#L335-L349"
     },
     {
       "inherits": {
@@ -81886,7 +81871,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L357-L370"
+      "specLocation": "_types/query_dsl/specialized.ts#L366-L379"
     },
     {
       "attachedBehaviors": [
@@ -81945,7 +81930,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/specialized.ts#L342-L355"
+      "specLocation": "_types/query_dsl/specialized.ts#L351-L364"
     },
     {
       "kind": "enum",
@@ -82946,7 +82931,31 @@
         }
       ],
       "shortcutProperty": "value",
-      "specLocation": "_types/query_dsl/term.ts#L238-L252"
+      "specLocation": "_types/query_dsl/term.ts#L215-L229"
+    },
+    {
+      "inherits": {
+        "generics": [
+          {
+            "kind": "instance_of",
+            "type": {
+              "name": "string",
+              "namespace": "_builtins"
+            }
+          }
+        ],
+        "type": {
+          "name": "RangeQueryBase",
+          "namespace": "_types.query_dsl"
+        }
+      },
+      "kind": "interface",
+      "name": {
+        "name": "TermRangeQuery",
+        "namespace": "_types.query_dsl"
+      },
+      "properties": [],
+      "specLocation": "_types/query_dsl/term.ts#L159-L159"
     },
     {
       "kind": "interface",
@@ -83000,7 +83009,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/term.ts#L266-L271"
+      "specLocation": "_types/query_dsl/term.ts#L243-L248"
     },
     {
       "attachedBehaviors": [
@@ -83046,7 +83055,7 @@
         "namespace": "_types.query_dsl"
       },
       "properties": [],
-      "specLocation": "_types/query_dsl/term.ts#L254-L259"
+      "specLocation": "_types/query_dsl/term.ts#L231-L236"
     },
     {
       "codegenNames": [
@@ -83058,7 +83067,7 @@
         "name": "TermsQueryField",
         "namespace": "_types.query_dsl"
       },
-      "specLocation": "_types/query_dsl/term.ts#L261-L264",
+      "specLocation": "_types/query_dsl/term.ts#L238-L241",
       "type": {
         "items": [
           {
@@ -83082,116 +83091,6 @@
         "kind": "union_of"
       }
     },
-    {
-      "inherits": {
-        "type": {
-          "name": "RangeQueryBase",
-          "namespace": "_types.query_dsl"
-        }
-      },
-      "kind": "interface",
-      "name": {
-        "name": "TermsRangeQuery",
-        "namespace": "_types.query_dsl"
-      },
-      "properties": [
-        {
-          "description": "Greater than.",
-          "name": "gt",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "string",
-              "namespace": "_builtins"
-            }
-          }
-        },
-        {
-          "description": "Greater than or equal to.",
-          "name": "gte",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "string",
-              "namespace": "_builtins"
-            }
-          }
-        },
-        {
-          "description": "Less than.",
-          "name": "lt",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "string",
-              "namespace": "_builtins"
-            }
-          }
-        },
-        {
-          "description": "Less than or equal to.",
-          "name": "lte",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "string",
-              "namespace": "_builtins"
-            }
-          }
-        },
-        {
-          "name": "from",
-          "required": false,
-          "type": {
-            "items": [
-              {
-                "kind": "instance_of",
-                "type": {
-                  "name": "string",
-                  "namespace": "_builtins"
-                }
-              },
-              {
-                "kind": "instance_of",
-                "type": {
-                  "name": "null",
-                  "namespace": "_builtins"
-                }
-              }
-            ],
-            "kind": "union_of"
-          }
-        },
-        {
-          "name": "to",
-          "required": false,
-          "type": {
-            "items": [
-              {
-                "kind": "instance_of",
-                "type": {
-                  "name": "string",
-                  "namespace": "_builtins"
-                }
-              },
-              {
-                "kind": "instance_of",
-                "type": {
-                  "name": "null",
-                  "namespace": "_builtins"
-                }
-              }
-            ],
-            "kind": "union_of"
-          }
-        }
-      ],
-      "specLocation": "_types/query_dsl/term.ts#L166-L185"
-    },
     {
       "inherits": {
         "type": {
@@ -83245,7 +83144,7 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/term.ts#L273-L286"
+      "specLocation": "_types/query_dsl/term.ts#L250-L263"
     },
     {
       "inherits": {
@@ -83418,7 +83317,105 @@
           }
         }
       ],
-      "specLocation": "_types/query_dsl/term.ts#L288-L290"
+      "specLocation": "_types/query_dsl/term.ts#L265-L267"
+    },
+    {
+      "attachedBehaviors": [
+        "AdditionalProperty"
+      ],
+      "inherits": {
+        "generics": [
+          {
+            "kind": "instance_of",
+            "type": {
+              "name": "Field",
+              "namespace": "_types"
+            }
+          },
+          {
+            "kind": "user_defined_value"
+          }
+        ],
+        "type": {
+          "name": "DecayFunctionBase",
+          "namespace": "_types.query_dsl"
+        }
+      },
+      "kind": "interface",
+      "name": {
+        "name": "UntypedDecayFunction",
+        "namespace": "_types.query_dsl"
+      },
+      "properties": [],
+      "specLocation": "_types/query_dsl/compound.ts#L188-L188"
+    },
+    {
+      "inherits": {
+        "generics": [
+          {
+            "kind": "user_defined_value"
+          },
+          {
+            "kind": "user_defined_value"
+          }
+        ],
+        "type": {
+          "name": "DistanceFeatureQueryBase",
+          "namespace": "_types.query_dsl"
+        }
+      },
+      "kind": "interface",
+      "name": {
+        "name": "UntypedDistanceFeatureQuery",
+        "namespace": "_types.query_dsl"
+      },
+      "properties": [],
+      "specLocation": "_types/query_dsl/specialized.ts#L62-L65"
+    },
+    {
+      "inherits": {
+        "generics": [
+          {
+            "kind": "user_defined_value"
+          }
+        ],
+        "type": {
+          "name": "RangeQueryBase",
+          "namespace": "_types.query_dsl"
+        }
+      },
+      "kind": "interface",
+      "name": {
+        "name": "UntypedRangeQuery",
+        "namespace": "_types.query_dsl"
+      },
+      "properties": [
+        {
+          "description": "Date format used to convert `date` values in the query.",
+          "name": "format",
+          "required": false,
+          "type": {
+            "kind": "instance_of",
+            "type": {
+              "name": "DateFormat",
+              "namespace": "_types"
+            }
+          }
+        },
+        {
+          "description": "Coordinated Universal Time (UTC) offset or IANA time zone used to convert `date` values in the query to UTC.",
+          "name": "time_zone",
+          "required": false,
+          "type": {
+            "kind": "instance_of",
+            "type": {
+              "name": "TimeZone",
+              "namespace": "_types"
+            }
+          }
+        }
+      ],
+      "specLocation": "_types/query_dsl/term.ts#L135-L144"
     },
     {
       "inherits": {
@@ -83543,7 +83540,7 @@
         }
       ],
       "shortcutProperty": "value",
-      "specLocation": "_types/query_dsl/term.ts#L292-L309"
+      "specLocation": "_types/query_dsl/term.ts#L269-L286"
     },
     {
       "inherits": {
diff --git a/specification/_types/query_dsl/compound.ts b/specification/_types/query_dsl/compound.ts
index d613b08a76..7e256f0385 100644
--- a/specification/_types/query_dsl/compound.ts
+++ b/specification/_types/query_dsl/compound.ts
@@ -24,6 +24,7 @@ import { double, float, long } from '@_types/Numeric'
 import { Script } from '@_types/Scripting'
 import { DateMath, Duration } from '@_types/Time'
 import { QueryBase, QueryContainer } from './abstractions'
+import { UserDefinedValue } from '@spec_utils/UserDefinedValue'
 
 export class BoolQuery extends QueryBase {
   /**
@@ -171,7 +172,12 @@ export class DecayPlacement<TOrigin, TScale> {
   origin?: TOrigin
 }
 
-export class DecayFunctionBase {
+/**
+ * @behavior_meta AdditionalProperty key=field value=placement
+ */
+export class DecayFunctionBase<TOrigin, TScale>
+  implements AdditionalProperty<TOrigin, TScale>
+{
   /**
    * Determines how the distance is calculated when a field used for computing the decay contains multiple values.
    * @server_default min
@@ -179,30 +185,18 @@ export class DecayFunctionBase {
   multi_value_mode?: MultiValueMode
 }
 
-/**
- * @behavior_meta AdditionalProperty key=field value=placement
- */
-export class NumericDecayFunction
-  extends DecayFunctionBase
-  implements AdditionalProperty<Field, DecayPlacement<double, double>> {}
-
-/**
- * @behavior_meta AdditionalProperty key=field value=placement
- */
-export class DateDecayFunction
-  extends DecayFunctionBase
-  implements AdditionalProperty<Field, DecayPlacement<DateMath, Duration>> {}
+export class UntypedDecayFunction extends DecayFunctionBase<Field, UserDefinedValue> {}
+export class NumericDecayFunction extends DecayFunctionBase<Field, DecayPlacement<double, double>> {}
+export class DateDecayFunction extends DecayFunctionBase<Field, DecayPlacement<DateMath, Duration>> {}
+export class GeoDecayFunction extends DecayFunctionBase<Field, DecayPlacement<GeoLocation, Distance>> {}
 
 /**
- * @behavior_meta AdditionalProperty key=field value=placement
+ * @codegen_names untyped, date, numeric, geo
+ * @variants untagged untyped=_types.query_dsl.UntypedDecayFunction
  */
-export class GeoDecayFunction
-  extends DecayFunctionBase
-  implements AdditionalProperty<Field, DecayPlacement<GeoLocation, Distance>> {}
-
-/** @codegen_names date, numeric, geo */
 // Note: deserialization depends on value types
 export type DecayFunction =
+  | UntypedDecayFunction
   | DateDecayFunction
   | NumericDecayFunction
   | GeoDecayFunction
diff --git a/specification/_types/query_dsl/specialized.ts b/specification/_types/query_dsl/specialized.ts
index 29fb2d81c4..5d9997f5fd 100644
--- a/specification/_types/query_dsl/specialized.ts
+++ b/specification/_types/query_dsl/specialized.ts
@@ -59,6 +59,11 @@ export class DistanceFeatureQueryBase<TOrigin, TDistance> extends QueryBase {
   field: Field
 }
 
+export class UntypedDistanceFeatureQuery extends DistanceFeatureQueryBase<
+  UserDefinedValue,
+  UserDefinedValue
+> {}
+
 export class GeoDistanceFeatureQuery extends DistanceFeatureQueryBase<
   GeoLocation,
   Distance
@@ -70,11 +75,12 @@ export class DateDistanceFeatureQuery extends DistanceFeatureQueryBase<
 > {}
 
 /**
- * @codegen_names geo, date
- * @variants untagged
+ * @codegen_names untyped, geo, date
+ * @variants untagged untyped=_types.query_dsl.UntypedDistanceFeatureQuery
  */
 // Note: deserialization depends on value types
 export type DistanceFeatureQuery =
+  | UntypedDistanceFeatureQuery
   | GeoDistanceFeatureQuery
   | DateDistanceFeatureQuery
 
diff --git a/specification/_types/query_dsl/term.ts b/specification/_types/query_dsl/term.ts
index 6de7bd40c2..e1a9f76347 100644
--- a/specification/_types/query_dsl/term.ts
+++ b/specification/_types/query_dsl/term.ts
@@ -32,6 +32,7 @@ import { Script } from '@_types/Scripting'
 import { DateFormat, DateMath, TimeZone } from '@_types/Time'
 import { QueryBase } from './abstractions'
 import { AdditionalProperty } from '@spec_utils/behaviors'
+import { UserDefinedValue } from '@spec_utils/UserDefinedValue'
 
 export class ExistsQuery extends QueryBase {
   /**
@@ -129,6 +130,9 @@ export class RangeQueryBase<T> extends QueryBase {
   lte?: T
   from?: T | null
   to?: T | null
+}
+
+export class UntypedRangeQuery extends RangeQueryBase<UserDefinedValue> {
   /**
    * Date format used to convert `date` values in the query.
    */
@@ -139,18 +143,27 @@ export class RangeQueryBase<T> extends QueryBase {
   time_zone?: TimeZone
 }
 
-export class DateRangeQuery extends RangeQueryBase<DateMath> {}
+export class DateRangeQuery extends RangeQueryBase<DateMath> {
+  /**
+   * Date format used to convert `date` values in the query.
+   */
+  format?: DateFormat
+  /**
+   *  Coordinated Universal Time (UTC) offset or IANA time zone used to convert `date` values in the query to UTC.
+   */
+  time_zone?: TimeZone
+}
 
 export class NumberRangeQuery extends RangeQueryBase<double> {}
 
 export class TermRangeQuery extends RangeQueryBase<string> {}
 
 /**
- * @codegen_names date, number, term
- * @variants untagged
+ * @codegen_names untyped, date, number, term
+ * @variants untagged untyped=_types.query_dsl.UntypedRangeQuery
  */
 // Note: deserialization depends on value types
-export type RangeQuery = DateRangeQuery | NumberRangeQuery | TermRangeQuery
+export type RangeQuery = UntypedRangeQuery | DateRangeQuery | NumberRangeQuery | TermRangeQuery
 
 export enum RangeRelation {
   /**
diff --git a/typescript-generator/src/metamodel.ts b/typescript-generator/src/metamodel.ts
index 3802951a3c..8c28e2847d 100644
--- a/typescript-generator/src/metamodel.ts
+++ b/typescript-generator/src/metamodel.ts
@@ -209,6 +209,7 @@ export class Container extends VariantBase {
 
 export class Untagged extends VariantBase {
   kind: 'untagged'
+  untyped_variant: Inherits
 }
 
 /**