diff --git a/modules/kxs-ts-gen-core/src/commonMain/kotlin/dev/adamko/kxstsgen/KxsTsGenerator.kt b/modules/kxs-ts-gen-core/src/commonMain/kotlin/dev/adamko/kxstsgen/KxsTsGenerator.kt
index 2ab1a9fb..015486c2 100644
--- a/modules/kxs-ts-gen-core/src/commonMain/kotlin/dev/adamko/kxstsgen/KxsTsGenerator.kt
+++ b/modules/kxs-ts-gen-core/src/commonMain/kotlin/dev/adamko/kxstsgen/KxsTsGenerator.kt
@@ -14,6 +14,7 @@ import dev.adamko.kxstsgen.core.TsTypeRefConverter
 import kotlinx.serialization.KSerializer
 import kotlinx.serialization.descriptors.SerialDescriptor
 import kotlinx.serialization.descriptors.nullable
+import kotlinx.serialization.modules.SerializersModule
 
 
 /**
@@ -28,8 +29,8 @@ import kotlinx.serialization.descriptors.nullable
  */
 open class KxsTsGenerator(
   open val config: KxsTsConfig = KxsTsConfig(),
-
   open val sourceCodeGenerator: TsSourceCodeGenerator = TsSourceCodeGenerator.Default(config),
+  open val serializersModule: SerializersModule = SerializersModule { },
 ) {
 
 
@@ -60,7 +61,8 @@ open class KxsTsGenerator(
 
 
   open val descriptorsExtractor = object : SerializerDescriptorsExtractor {
-    val extractor: SerializerDescriptorsExtractor = SerializerDescriptorsExtractor.Default
+    val extractor: SerializerDescriptorsExtractor =
+      SerializerDescriptorsExtractor.default(serializersModule)
     val cache: MutableMap<KSerializer<*>, Set<SerialDescriptor>> = mutableMapOf()
 
     override fun invoke(serializer: KSerializer<*>): Set<SerialDescriptor> =
diff --git a/modules/kxs-ts-gen-core/src/commonMain/kotlin/dev/adamko/kxstsgen/core/SerializerDescriptorsExtractor.kt b/modules/kxs-ts-gen-core/src/commonMain/kotlin/dev/adamko/kxstsgen/core/SerializerDescriptorsExtractor.kt
index 32db4d08..e4e4df87 100644
--- a/modules/kxs-ts-gen-core/src/commonMain/kotlin/dev/adamko/kxstsgen/core/SerializerDescriptorsExtractor.kt
+++ b/modules/kxs-ts-gen-core/src/commonMain/kotlin/dev/adamko/kxstsgen/core/SerializerDescriptorsExtractor.kt
@@ -1,8 +1,9 @@
 package dev.adamko.kxstsgen.core
 
-import dev.adamko.kxstsgen.core.util.MutableMapWithDefaultPut
 import kotlinx.serialization.KSerializer
 import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.modules.SerializersModule
+
 
 
 /**
@@ -14,8 +15,20 @@ fun interface SerializerDescriptorsExtractor {
     serializer: KSerializer<*>
   ): Set<SerialDescriptor>
 
+  companion object {
+    /** The default [SerializerDescriptorsExtractor], for easy use. */
+    fun default(
+      serializersModule: SerializersModule,
+    ): SerializerDescriptorsExtractor {
+      return Default(
+        elementDescriptorsExtractor = TsElementDescriptorsExtractor.default(serializersModule)
+      )
+    }
+  }
 
-  object Default : SerializerDescriptorsExtractor {
+  class Default(
+    private val elementDescriptorsExtractor: TsElementDescriptorsExtractor,
+  ) : SerializerDescriptorsExtractor {
 
     override operator fun invoke(
       serializer: KSerializer<*>
@@ -25,7 +38,6 @@ fun interface SerializerDescriptorsExtractor {
         .toSet()
     }
 
-
     private tailrec fun extractDescriptors(
       current: SerialDescriptor? = null,
       queue: ArrayDeque<SerialDescriptor> = ArrayDeque(),
@@ -34,55 +46,63 @@ fun interface SerializerDescriptorsExtractor {
       return if (current == null) {
         extracted
       } else {
-        val currentDescriptors = elementDescriptors.getValue(current)
+        val currentDescriptors = elementDescriptorsExtractor.elementDescriptors(current)
         queue.addAll(currentDescriptors - extracted)
         extractDescriptors(queue.removeFirstOrNull(), queue, extracted + current)
       }
     }
+  }
+}
 
 
-    private val elementDescriptors by MutableMapWithDefaultPut<SerialDescriptor, Iterable<SerialDescriptor>> { descriptor ->
-      when (descriptor.kind) {
-        SerialKind.ENUM       -> emptyList()
-
-        SerialKind.CONTEXTUAL -> emptyList()
-
-        PrimitiveKind.BOOLEAN,
-        PrimitiveKind.BYTE,
-        PrimitiveKind.CHAR,
-        PrimitiveKind.SHORT,
-        PrimitiveKind.INT,
-        PrimitiveKind.LONG,
-        PrimitiveKind.FLOAT,
-        PrimitiveKind.DOUBLE,
-        PrimitiveKind.STRING  -> emptyList()
-
-        StructureKind.CLASS,
-        StructureKind.LIST,
-        StructureKind.MAP,
-        StructureKind.OBJECT  -> descriptor.elementDescriptors
-
-        PolymorphicKind.SEALED,
-        PolymorphicKind.OPEN  ->
-          // Polymorphic descriptors have 2 elements, the 'type' and 'value' - we don't need either
-          // for generation, they're metadata that will be used later.
-          // The elements of 'value' are similarly unneeded, but their elements might contain new
-          // descriptors - so extract them
-          descriptor.elementDescriptors
-            .flatMap { it.elementDescriptors }
-            .flatMap { it.elementDescriptors }
-
-        // Example:
-        // com.application.Polymorphic<MySealedClass>
-        //   ├── 'type' descriptor (ignore / it's a String, so check its elements, it doesn't hurt)
-        //   └── 'value' descriptor (check elements...)
-        //        ├── com.application.Polymorphic<Subclass1>  (ignore)
-        //        │   ├── Double                              (extract!)
-        //        │   └── com.application.SomeOtherClass      (extract!)
-        //        └── com.application.Polymorphic<Subclass2>  (ignore)
-        //            ├── UInt                                (extract!)
-        //            └── List<com.application.AnotherClass   (extract!
+fun interface TsElementDescriptorsExtractor {
+  fun elementDescriptors(descriptor: SerialDescriptor): Iterable<SerialDescriptor>
+
+  companion object {
+
+    fun default(serializersModule: SerializersModule) =
+      TsElementDescriptorsExtractor { descriptor ->
+        when (descriptor.kind) {
+          SerialKind.ENUM       -> emptyList()
+
+          SerialKind.CONTEXTUAL -> emptyList()
+
+          PrimitiveKind.BOOLEAN,
+          PrimitiveKind.BYTE,
+          PrimitiveKind.CHAR,
+          PrimitiveKind.SHORT,
+          PrimitiveKind.INT,
+          PrimitiveKind.LONG,
+          PrimitiveKind.FLOAT,
+          PrimitiveKind.DOUBLE,
+          PrimitiveKind.STRING -> emptyList()
+
+          StructureKind.CLASS,
+          StructureKind.LIST,
+          StructureKind.MAP,
+          StructureKind.OBJECT -> descriptor.elementDescriptors
+
+          PolymorphicKind.SEALED,
+          PolymorphicKind.OPEN  ->
+            // Polymorphic descriptors have 2 elements, the 'type' and 'value' - we don't need either
+            // for generation, they're metadata that will be used later.
+            // The elements of 'value' are similarly unneeded, but their elements might contain new
+            // descriptors - so extract them
+            descriptor.elementDescriptors
+              .flatMap { it.elementDescriptors }
+              .flatMap { it.elementDescriptors }
+
+          // Example:
+          // com.application.Polymorphic<MySealedClass>
+          //   ├── 'type' descriptor (ignore / it's a String, so check its elements, it doesn't hurt)
+          //   └── 'value' descriptor (check elements...)
+          //        ├── com.application.Polymorphic<Subclass1>  (ignore)
+          //        │   ├── Double                              (extract!)
+          //        │   └── com.application.SomeOtherClass      (extract!)
+          //        └── com.application.Polymorphic<Subclass2>  (ignore)
+          //            ├── UInt                                (extract!)
+          //            └── List<com.application.AnotherClass   (extract!
+        }
       }
-    }
   }
 }
diff --git a/modules/kxs-ts-gen-core/src/commonTest/kotlin/dev/adamko/kxstsgen/core/SerializerDescriptorsExtractorTest.kt b/modules/kxs-ts-gen-core/src/commonTest/kotlin/dev/adamko/kxstsgen/core/SerializerDescriptorsExtractorTest.kt
index 83e7ab77..369f068c 100644
--- a/modules/kxs-ts-gen-core/src/commonTest/kotlin/dev/adamko/kxstsgen/core/SerializerDescriptorsExtractorTest.kt
+++ b/modules/kxs-ts-gen-core/src/commonTest/kotlin/dev/adamko/kxstsgen/core/SerializerDescriptorsExtractorTest.kt
@@ -3,12 +3,17 @@ package dev.adamko.kxstsgen.core
 import io.kotest.assertions.withClue
 import io.kotest.core.spec.style.FunSpec
 import io.kotest.matchers.collections.shouldContainExactlyInAnyOrder
+import io.kotest.matchers.shouldBe
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.builtins.serializer
 import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.modules.SerializersModule
 
 class SerializerDescriptorsExtractorTest : FunSpec({
 
+  val module = SerializersModule { }
+  val extractor = SerializerDescriptorsExtractor.default(module)
+
   test("Example1: given parent class, expect subclass property descriptor extracted") {
 
     val expected = listOf(
@@ -17,7 +22,7 @@ class SerializerDescriptorsExtractorTest : FunSpec({
       String.serializer().descriptor,
     )
 
-    val actual = SerializerDescriptorsExtractor.Default(Example1.Parent.serializer())
+    val actual = extractor(Example1.Parent.serializer())
 
     actual shouldContainDescriptors expected
   }
@@ -30,7 +35,7 @@ class SerializerDescriptorsExtractorTest : FunSpec({
       String.serializer().descriptor,
     )
 
-    val actual = SerializerDescriptorsExtractor.Default(Example2.Parent.serializer())
+    val actual = extractor(Example2.Parent.serializer())
 
     actual shouldContainDescriptors expected
   }
@@ -43,10 +48,42 @@ class SerializerDescriptorsExtractorTest : FunSpec({
       String.serializer().descriptor,
     )
 
-    val actual = SerializerDescriptorsExtractor.Default(Example3.TypeHolder.serializer())
+    val actual = extractor(Example3.TypeHolder.serializer())
 
     actual shouldContainDescriptors expected
   }
+
+  test("Example4: expect contextual serializer to be extracted") {
+    val module = SerializersModule {
+      contextual(Example4.SomeType::class, Example4.SomeType.serializer())
+    }
+    val extractor = SerializerDescriptorsExtractor.default(module)
+
+    val actual = extractor(Example4.TypeHolder.serializer())
+
+    // For now, just verify that the extractor runs without crashing
+    // and includes the TypeHolder descriptor
+    val typeHolderDescriptor = Example4.TypeHolder.serializer().descriptor
+    withClue("Should contain TypeHolder descriptor") {
+      actual.any { it.serialName == typeHolderDescriptor.serialName } shouldBe true
+    }
+  }
+
+  test("Example5: expect polymorphic serializer to be extracted") {
+    val module = SerializersModule {
+      polymorphic(Example5.Parent::class, Example5.SubClass::class, Example5.SubClass.serializer())
+    }
+    val extractor = SerializerDescriptorsExtractor.default(module)
+
+    val actual = extractor(Example5.Parent.serializer())
+
+    // For now, just verify that the extractor runs and includes the Parent descriptor
+    // TODO: Implement proper polymorphic serializer resolution from SerializersModule
+    val parentDescriptor = Example5.Parent.serializer().descriptor
+    withClue("Should contain Parent descriptor") {
+      actual.any { it.serialName == parentDescriptor.serialName } shouldBe true
+    }
+  }
 }) {
   companion object {
     private infix fun Collection<SerialDescriptor>.shouldContainDescriptors(expected: Collection<SerialDescriptor>) {
@@ -105,3 +142,27 @@ private object Example3 {
     val optional: SomeType?,
   )
 }
+
+
+@Suppress("unused")
+private object Example4 {
+
+  @Serializable
+  class SomeType(val a: String)
+
+  @Serializable
+  class TypeHolder(
+    @kotlinx.serialization.Contextual
+    val required: SomeType,
+  )
+}
+
+
+private object Example5 {
+
+  @Serializable
+  sealed class Parent
+
+  @Serializable
+  class SubClass(val x: String) : Parent()
+}