diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index dc1e9e0e..f40c862b 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -19,10 +19,10 @@ gjf = "1.13.0"
 incap = "1.0.0"
 jdk = "20"
 jvmTarget = "11"
-kotlin = "1.9.20"
+kotlin = "2.0.0-Beta1"
 kotlinCompileTesting = "0.4.0"
 kotlinpoet = "1.15.0"
-ksp = "1.9.20-1.0.14"
+ksp = "2.0.0-Beta1-1.0.14"
 ktfmt = "0.46"
 moshi = "1.15.0"
 okhttp = "4.12.0"
diff --git a/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/BaseSymbols.kt b/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/BaseSymbols.kt
index 9ebcef3d..6b6d05ca 100644
--- a/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/BaseSymbols.kt
+++ b/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/BaseSymbols.kt
@@ -1,3 +1,5 @@
+@file:OptIn(UnsafeDuringIrConstructionAPI::class)
+
 package dev.zacsweers.moshix.ir.compiler
 
 import org.jetbrains.kotlin.backend.common.extensions.IrPluginContext
@@ -23,6 +25,7 @@ import org.jetbrains.kotlin.ir.expressions.impl.IrClassReferenceImpl
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.symbols.IrPropertySymbol
 import org.jetbrains.kotlin.ir.symbols.IrTypeParameterSymbol
+import org.jetbrains.kotlin.ir.symbols.UnsafeDuringIrConstructionAPI
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.classFqName
 import org.jetbrains.kotlin.ir.types.classifierOrNull
diff --git a/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiIrGenerationExtension.kt b/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiIrGenerationExtension.kt
index a91fcaef..03b947cf 100644
--- a/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiIrGenerationExtension.kt
+++ b/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiIrGenerationExtension.kt
@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.backend.common.extensions.IrGenerationExtension
 import org.jetbrains.kotlin.backend.common.extensions.IrPluginContext
 import org.jetbrains.kotlin.cli.common.messages.MessageCollector
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
+import org.jetbrains.kotlin.ir.symbols.UnsafeDuringIrConstructionAPI
 import org.jetbrains.kotlin.name.ClassId
 
 internal class MoshiIrGenerationExtension(
@@ -29,6 +30,7 @@ internal class MoshiIrGenerationExtension(
   private val debug: Boolean
 ) : IrGenerationExtension {
 
+  @OptIn(UnsafeDuringIrConstructionAPI::class)
   override fun generate(moduleFragment: IrModuleFragment, pluginContext: IrPluginContext) {
     val generatedAnnotation =
       generatedAnnotationName?.let { name ->
diff --git a/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiIrUtil.kt b/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiIrUtil.kt
index a4323e5e..ae97b896 100644
--- a/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiIrUtil.kt
+++ b/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiIrUtil.kt
@@ -29,6 +29,7 @@ import org.jetbrains.kotlin.ir.declarations.IrProperty
 import org.jetbrains.kotlin.ir.expressions.IrConst
 import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
 import org.jetbrains.kotlin.ir.expressions.IrGetEnumValue
+import org.jetbrains.kotlin.ir.symbols.UnsafeDuringIrConstructionAPI
 import org.jetbrains.kotlin.ir.types.classOrNull
 import org.jetbrains.kotlin.ir.util.file
 import org.jetbrains.kotlin.ir.util.getAnnotation
@@ -38,6 +39,7 @@ import org.jetbrains.kotlin.name.FqName
 internal val JSON_ANNOTATION = FqName("com.squareup.moshi.Json")
 internal val JSON_QUALIFIER_ANNOTATION = FqName("com.squareup.moshi.JsonQualifier")
 
+@OptIn(UnsafeDuringIrConstructionAPI::class)
 internal fun IrAnnotationContainer?.jsonQualifiers(): Set<IrConstructorCall> {
   if (this == null) return emptySet()
   return annotations.filterTo(LinkedHashSet()) {
@@ -81,6 +83,7 @@ private val TargetProperty.isVisible: Boolean
  * Returns a generator for this property, or null if either there is an error and this property
  * cannot be used with code gen, or if no codegen is necessary for this property.
  */
+@OptIn(UnsafeDuringIrConstructionAPI::class)
 internal fun TargetProperty.generator(
   originalType: IrClass,
   errors: MutableList<(logger: MessageCollector) -> Unit>
diff --git a/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiSymbols.kt b/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiSymbols.kt
index 6a999506..d88b96b4 100644
--- a/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiSymbols.kt
+++ b/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiSymbols.kt
@@ -13,6 +13,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+@file:OptIn(UnsafeDuringIrConstructionAPI::class)
+
 package dev.zacsweers.moshix.ir.compiler
 
 import org.jetbrains.kotlin.backend.common.extensions.IrPluginContext
@@ -28,6 +30,7 @@ import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
 import org.jetbrains.kotlin.ir.declarations.IrPackageFragment
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
+import org.jetbrains.kotlin.ir.symbols.UnsafeDuringIrConstructionAPI
 import org.jetbrains.kotlin.ir.types.defaultType
 import org.jetbrains.kotlin.ir.types.makeNotNull
 import org.jetbrains.kotlin.ir.types.makeNullable
diff --git a/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/util/IrSourcePrinter.kt b/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/util/IrSourcePrinter.kt
index 77d1e80e..4b78d7eb 100644
--- a/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/util/IrSourcePrinter.kt
+++ b/moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/util/IrSourcePrinter.kt
@@ -13,6 +13,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+@file:OptIn(UnsafeDuringIrConstructionAPI::class)
+
 package dev.zacsweers.moshix.ir.compiler.util
 
 import java.util.Locale
@@ -87,6 +89,7 @@ import org.jetbrains.kotlin.ir.expressions.IrWhen
 import org.jetbrains.kotlin.ir.expressions.IrWhileLoop
 import org.jetbrains.kotlin.ir.expressions.impl.IrIfThenElseImpl
 import org.jetbrains.kotlin.ir.symbols.IrTypeAliasSymbol
+import org.jetbrains.kotlin.ir.symbols.UnsafeDuringIrConstructionAPI
 import org.jetbrains.kotlin.ir.types.IrDynamicType
 import org.jetbrains.kotlin.ir.types.IrErrorType
 import org.jetbrains.kotlin.ir.types.IrSimpleType
diff --git a/moshi-proguard-rule-gen/src/test/kotlin/dev/zacsweers/moshix/proguardgen/MoshiProguardGenSymbolProcessorTest.kt b/moshi-proguard-rule-gen/src/test/kotlin/dev/zacsweers/moshix/proguardgen/MoshiProguardGenSymbolProcessorTest.kt
index 8f4106ef..f3d84fa6 100644
--- a/moshi-proguard-rule-gen/src/test/kotlin/dev/zacsweers/moshix/proguardgen/MoshiProguardGenSymbolProcessorTest.kt
+++ b/moshi-proguard-rule-gen/src/test/kotlin/dev/zacsweers/moshix/proguardgen/MoshiProguardGenSymbolProcessorTest.kt
@@ -177,6 +177,7 @@ class MoshiSealedSymbolProcessorProviderTest {
       sources = sourceFiles.toList()
       inheritClassPath = true
       symbolProcessorProviders = listOf(MoshiProguardGenSymbolProcessor.Provider())
+      languageVersion = "1.9"
       block()
     }
 
diff --git a/moshi-sealed/codegen/src/test/kotlin/dev/zacsweers/moshix/sealed/codegen/ksp/MoshiSealedSymbolProcessorTest.kt b/moshi-sealed/codegen/src/test/kotlin/dev/zacsweers/moshix/sealed/codegen/ksp/MoshiSealedSymbolProcessorTest.kt
index 9f888ed3..3103b47a 100644
--- a/moshi-sealed/codegen/src/test/kotlin/dev/zacsweers/moshix/sealed/codegen/ksp/MoshiSealedSymbolProcessorTest.kt
+++ b/moshi-sealed/codegen/src/test/kotlin/dev/zacsweers/moshix/sealed/codegen/ksp/MoshiSealedSymbolProcessorTest.kt
@@ -512,6 +512,7 @@ class MoshiSealedSymbolProcessorProviderTest {
       sources = sourceFiles.toList()
       inheritClassPath = true
       symbolProcessorProviders = listOf(MoshiSealedSymbolProcessorProvider())
+      languageVersion = "1.9"
     }
 
   private fun compile(