diff --git a/build.gradle.kts b/build.gradle.kts
index df0931c57..256d1186b 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -232,7 +232,7 @@ tasks.check {
   dependsOn(
     tasks.withType<Test>(),
     // TODO: https://youtrack.jetbrains.com/issue/KT-78525
-    tasks.checkLegacyAbi,
+    tasks.checkKotlinAbi,
   )
 }
 
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 2044b7720..58d9b4779 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -1,7 +1,7 @@
 [versions]
 jdkRelease = "17"
 minGradle = "9.0.0"
-kotlin = "2.3.0"
+kotlin = "2.3.20-Beta1"
 moshi = "1.15.2"
 pluginPublish = "2.0.0"
 
diff --git a/src/documentTest/kotlin/com/github/jengelman/gradle/plugins/shadow/snippet/SnippetExecutable.kt b/src/documentTest/kotlin/com/github/jengelman/gradle/plugins/shadow/snippet/SnippetExecutable.kt
index 3d02c49ec..ed9b81655 100644
--- a/src/documentTest/kotlin/com/github/jengelman/gradle/plugins/shadow/snippet/SnippetExecutable.kt
+++ b/src/documentTest/kotlin/com/github/jengelman/gradle/plugins/shadow/snippet/SnippetExecutable.kt
@@ -2,7 +2,6 @@ package com.github.jengelman.gradle.plugins.shadow.snippet
 
 import com.github.jengelman.gradle.plugins.shadow.testkit.assertNoDeprecationWarnings
 import com.github.jengelman.gradle.plugins.shadow.testkit.gradleRunner
-import com.github.jengelman.gradle.plugins.shadow.testkit.toWarningsAsErrors
 import java.nio.file.Path
 import java.util.jar.JarOutputStream
 import kotlin.io.path.createDirectory
@@ -92,11 +91,7 @@ sealed class SnippetExecutable : Executable {
     }
 
     try {
-      gradleRunner(
-          projectDir = projectRoot,
-          arguments = listOf("build", "--stacktrace"),
-          warningsAsErrors = mainScript.toWarningsAsErrors(),
-        )
+      gradleRunner(projectDir = projectRoot, arguments = listOf("build", "--stacktrace"))
         .build()
         .assertNoDeprecationWarnings()
     } catch (t: Throwable) {
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/BasePluginTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/BasePluginTest.kt
index 416e97836..01b1a3d42 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/BasePluginTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/BasePluginTest.kt
@@ -13,7 +13,6 @@ import com.github.jengelman.gradle.plugins.shadow.testkit.assertNoDeprecationWar
 import com.github.jengelman.gradle.plugins.shadow.testkit.commonGradleArgs
 import com.github.jengelman.gradle.plugins.shadow.testkit.gradleRunner
 import com.github.jengelman.gradle.plugins.shadow.testkit.requireResourceAsPath
-import com.github.jengelman.gradle.plugins.shadow.testkit.toWarningsAsErrors
 import com.github.jengelman.gradle.plugins.shadow.transformers.ResourceTransformer
 import com.github.jengelman.gradle.plugins.shadow.util.AppendableMavenRepository
 import com.github.jengelman.gradle.plugins.shadow.util.JarBuilder
@@ -378,16 +377,9 @@ abstract class BasePluginTest {
   }
 
   private fun runner(arguments: Iterable<String>, block: GradleRunner.() -> Unit): GradleRunner {
-    val warningsAsErrors =
-      try {
-        projectScript.readText().toWarningsAsErrors()
-      } catch (_: UninitializedPropertyAccessException) {
-        true // Default warning mode if projectScript is not initialized yet.
-      }
     return gradleRunner(
       projectDir = projectRoot,
       arguments = commonGradleArgs + arguments,
-      warningsAsErrors = warningsAsErrors,
       block = block,
     )
   }
diff --git a/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/GradleRunner.kt b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/GradleRunner.kt
index 749af3cb9..1e58d14d2 100644
--- a/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/GradleRunner.kt
+++ b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/GradleRunner.kt
@@ -60,6 +60,3 @@ fun BuildResult.assertNoDeprecationWarnings() = apply {
       "will fail with an error in Gradle",
     )
 }
-
-// TODO: https://youtrack.jetbrains.com/issue/KT-78620
-fun String.toWarningsAsErrors(): Boolean = !contains("org.jetbrains.kotlin.multiplatform")