diff --git a/modules/core/src/main/scala/playground/CompilationError.scala b/modules/core/src/main/scala/playground/CompilationError.scala
index f83391a9..ce14976f 100644
--- a/modules/core/src/main/scala/playground/CompilationError.scala
+++ b/modules/core/src/main/scala/playground/CompilationError.scala
@@ -138,6 +138,9 @@ sealed trait CompilationErrorDetails extends Product with Serializable {
       case EmptyStruct(possibleValues) =>
         s"found empty struct, expected one of: ${possibleValues.mkString_(", ")}."
 
+      case InvalidIntEnumValue(value) =>
+        s"Invalid value for open int enum: $value - must be an integer."
+
       case UnknownEnumValue(name, possibleValues) =>
         s"Unknown enum value: $name. Available values: ${possibleValues.mkString(", ")}"
 
@@ -228,6 +231,10 @@ object CompilationErrorDetails {
     possibleValues: NonEmptyList[String]
   ) extends CompilationErrorDetails
 
+  final case class InvalidIntEnumValue(
+    value: String
+  ) extends CompilationErrorDetails
+
   final case class UnknownEnumValue(
     value: String,
     possibleValues: List[String],
diff --git a/modules/core/src/main/scala/playground/NodeEncoderVisitor.scala b/modules/core/src/main/scala/playground/NodeEncoderVisitor.scala
index 691ddaf1..ede62fd3 100644
--- a/modules/core/src/main/scala/playground/NodeEncoderVisitor.scala
+++ b/modules/core/src/main/scala/playground/NodeEncoderVisitor.scala
@@ -28,6 +28,7 @@ import smithy4s.capability.EncoderK
 import smithy4s.schema.Alt
 import smithy4s.schema.CollectionTag
 import smithy4s.schema.EnumTag
+import smithy4s.schema.EnumTag._
 import smithy4s.schema.EnumValue
 import smithy4s.schema.Field
 import smithy4s.schema.Primitive
@@ -164,7 +165,12 @@ object NodeEncoderVisitor extends SchemaVisitor[NodeEncoder] { self =>
     tag: EnumTag[E],
     values: List[EnumValue[E]],
     total: E => EnumValue[E],
-  ): NodeEncoder[E] = string.contramap(total(_).name)
+  ): NodeEncoder[E] =
+    tag match {
+      case ClosedIntEnum | ClosedStringEnum => string.contramap(total(_).name)
+      // todo: test
+      case OpenIntEnum(_) | OpenStringEnum(_) => string.contramap(total(_).stringValue)
+    }
 
   def struct[S](
     shapeId: ShapeId,
diff --git a/modules/core/src/main/scala/playground/QueryCompilerVisitor.scala b/modules/core/src/main/scala/playground/QueryCompilerVisitor.scala
index b31b9534..af8eae81 100644
--- a/modules/core/src/main/scala/playground/QueryCompilerVisitor.scala
+++ b/modules/core/src/main/scala/playground/QueryCompilerVisitor.scala
@@ -21,6 +21,8 @@ import smithy4s.Timestamp
 import smithy4s.schema.Alt
 import smithy4s.schema.CollectionTag
 import smithy4s.schema.EnumTag
+import smithy4s.schema.EnumTag.OpenIntEnum
+import smithy4s.schema.EnumTag.OpenStringEnum
 import smithy4s.schema.EnumValue
 import smithy4s.schema.Field
 import smithy4s.schema.Primitive
@@ -483,7 +485,20 @@ object QueryCompilerVisitorInternal extends SchemaVisitor[QueryCompiler] {
         Ior.bothNec(CompilationError.warning(EnumFallback(v.name), range).deprecated, v.value)
 
       case (None, None) =>
-        Ior.leftNec(CompilationError.error(UnknownEnumValue(name, values.map(_.name)), range))
+        tag match {
+          // todo: test
+          case OpenIntEnum(unknown) =>
+            name
+              .toIntOption
+              .toRightIor(CompilationError.error(InvalidIntEnumValue(name), range))
+              .toIorNec
+              .map(unknown)
+
+          // todo: test
+          case OpenStringEnum(unknown) => unknown(name).pure[QueryCompiler.Result]
+          case _ =>
+            Ior.leftNec(CompilationError.error(UnknownEnumValue(name, values.map(_.name)), range))
+        }
     }
 
   }
diff --git a/modules/core/src/test/smithy/demo.smithy b/modules/core/src/test/smithy/demo.smithy
index 80f04d05..5dc63131 100644
--- a/modules/core/src/test/smithy/demo.smithy
+++ b/modules/core/src/test/smithy/demo.smithy
@@ -3,6 +3,7 @@ $version: "2"
 namespace demo.smithy
 
 use alloy#UUID
+use alloy#openEnum
 use alloy#simpleRestJson
 use smithy4s.meta#indexedSeq
 use smithy4s.meta#refinement
@@ -67,9 +68,10 @@ structure CreateHeroInput {
     friendSet: FriendSet
     hasNewtypes: HasNewtypes
     hasDeprecations: HasDeprecations
-    doc: Document,
-    sparse: SampleSparseList,
+    doc: Document
+    sparse: SampleSparseList
     sparseMap: SampleSparseMap
+    tier: PrivacyTier
 }
 
 @uniqueItems
@@ -290,7 +292,6 @@ structure HasMixin with [SampleMixin] {
     name: String
 }
 
-
 @sparse
 list SampleSparseList {
     member: Integer
@@ -301,3 +302,15 @@ map SampleSparseMap {
     key: String
     value: Integer
 }
+
+@openEnum
+enum OpenStringEnum {
+    ICE
+    FIRE
+}
+
+@openEnum
+intEnum OpenIntEnum {
+    ICE = 1
+    FIRE = 2
+}
diff --git a/modules/language-support/src/main/scala/playground/language/CompletionVisitor.scala b/modules/language-support/src/main/scala/playground/language/CompletionVisitor.scala
index f8421a93..783cc16e 100644
--- a/modules/language-support/src/main/scala/playground/language/CompletionVisitor.scala
+++ b/modules/language-support/src/main/scala/playground/language/CompletionVisitor.scala
@@ -33,7 +33,7 @@ import smithy4s.dynamic.DynamicSchemaIndex
 import smithy4s.schema.Alt
 import smithy4s.schema.CollectionTag
 import smithy4s.schema.EnumTag
-import smithy4s.schema.EnumTag.IntEnum
+import smithy4s.schema.EnumTag._
 import smithy4s.schema.EnumValue
 import smithy4s.schema.Field
 import smithy4s.schema.Primitive
@@ -251,8 +251,10 @@ object CompletionItem {
 
       case e @ EnumerationSchema(_, _, _, _, _) =>
         e.tag match {
-          case IntEnum() => now(s"intEnum ${e.shapeId.name}")
-          case _         => now(s"enum ${e.shapeId.name}")
+          case ClosedIntEnum     => now(s"intEnum ${e.shapeId.name}")
+          case OpenIntEnum(_)    => now(s"@openEnum intEnum ${e.shapeId.name}")
+          case OpenStringEnum(_) => now(s"@openEnum enum ${e.shapeId.name}")
+          case ClosedStringEnum  => now(s"enum ${e.shapeId.name}")
         }
 
       case MapSchema(shapeId, _, key, value) =>
diff --git a/project/plugins.sbt b/project/plugins.sbt
index b4014537..816f4c66 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -1,5 +1,3 @@
-ThisBuild / libraryDependencySchemes += "org.scala-lang.modules" %% "scala-xml" % VersionScheme.Always
-
 addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.5.11")
 addSbtPlugin("org.typelevel" % "sbt-tpolecat" % "0.5.2")