Plugin upgrade to 2026.2 causes kotlin bundle exceptions?

got a mail notifying me that 2026.2 is going to be released soon, and i should make my plugin ready. I tried to bump the intellij target to the release candidate and bumped intelliJPlatform gradle plugin to latest (2.18.0) but now when i try to run my tests i get a lot of errors that seems unrelated to my code.

the plugin seems to work just fine if i test it with runIde so currently it seems to be a tests only problem.

anyone else experiencing this, and/or know the fix ?

EDIT: looks like i am forced to include kotlin as a bundled plugin now to get rid of these errors for some reason, i guess its to intertwined with the java plugin that i use or something like that.

org.jetbrains.kotlin 
Caused by: java.lang.AssertionError: 'hints.codevision.script.definition.name' is not found (baseBundleName=messages.KotlinBaseScriptingBundle, bundle=com.intellij.IntelliJResourceBundle@3bfd9f6a)
	at com.intellij.openapi.diagnostic.DefaultLogger.error(DefaultLogger.java:91)
	at com.intellij.openapi.diagnostic.Logger.error(Logger.java:378)
	at com.intellij.BundleBaseKt.useDefaultValue(BundleBase.kt:284)
	at com.intellij.IntelliJResourceBundle.getMessage(IntelliJResourceBundle.kt:41)
	at com.intellij.BundleBaseKt.messageOrDefault(BundleBase.kt:247)
	at com.intellij.AbstractBundle.getMessage(AbstractBundle.kt:112)
	at org.jetbrains.kotlin.util.AbstractKotlinBundle.getMessage(AbstractKotlinBundle.kt:17)
	at org.jetbrains.kotlin.idea.core.script.shared.KotlinBaseScriptingBundle.message(KotlinBaseScriptingBundle.kt:15)
	at org.jetbrains.kotlin.idea.core.script.k2.definitions.KotlinScriptDefinitionCodeVisionProvider.<init>(KotlinScriptDefinitionCodeVisionProvider.kt:26)
	at com.intellij.serviceContainer.ComponentManagerImpl.findConstructorAndInstantiateClass(ComponentManagerImpl.kt:965)
	at com.intellij.serviceContainer.ComponentManagerImpl.doInstantiateClass(ComponentManagerImpl.kt:974)
	... 39 more
Caused by: java.lang.Throwable: 'hints.codevision.script.definition.name' is not found (baseBundleName=messages.KotlinBaseScriptingBundle, bundle=com.intellij.IntelliJResourceBundle@3bfd9f6a)
	... 49 more
Caused by: com.intellij.diagnostic.PluginException: Cannot create class org.jetbrains.kotlin.idea.core.script.k2.definitions.KotlinScriptDefinitionCodeVisionProvider (classloader=com.intellij.util.lang.PathClassLoader@6adede5) [Plugin: org.jetbrains.kotlin]
	at com.intellij.serviceContainer.ComponentManagerImpl.doInstantiateClass(ComponentManagerImpl.kt:983)
	at com.intellij.serviceContainer.ComponentManagerImpl.instantiateClass$lambda$1$0(ComponentManagerImpl.kt:958)
	at com.intellij.concurrency.ThreadContext.installThreadContext(threadContext.kt:307)
	at com.intellij.concurrency.ThreadContext.installThreadContext$default(threadContext.kt:304)
	at com.intellij.serviceContainer.ComponentManagerImpl.instantiateClass$lambda$1(ComponentManagerImpl.kt:957)
	at com.intellij.concurrency.ThreadContext.resetThreadContext(threadContext.kt:295)
	at com.intellij.serviceContainer.ComponentManagerImpl.instantiateClass(ComponentManagerImpl.kt:956)
	at com.intellij.openapi.extensions.impl.SimpleConstructorInjectionAdapter.instantiateClass(XmlExtensionAdapter.kt:112)
com.intellij.diagnostic.PluginException: Cannot create extension (class=org.jetbrains.kotlin.idea.core.script.k2.definitions.KotlinScriptDefinitionCodeVisionProvider) [Plugin: org.jetbrains.kotlin]
	at com.intellij.serviceContainer.ComponentManagerImpl.createError(ComponentManagerImpl.kt:1047)
	at com.intellij.openapi.extensions.impl.XmlExtensionAdapter.doCreateInstance(XmlExtensionAdapter.kt:83)
	at com.intellij.openapi.extensions.impl.XmlExtensionAdapter.createInstance(XmlExtensionAdapter.kt:43)
	at com.intellij.openapi.extensions.impl.ExtensionPointImpl.processAdapter(ExtensionPointImpl.kt:398)
	at com.intellij.openapi.extensions.impl.ExtensionPointImpl.createExtensionInstances(ExtensionPointImpl.kt:382)
	at com.intellij.openapi.extensions.impl.ExtensionPointImpl.getExtensionList(ExtensionPointImpl.kt:236)
	at com.intellij.openapi.extensions.ExtensionPointName.getExtensionList(ExtensionPointName.kt:55)
	at com.intellij.codeInsight.hints.codeVision.DaemonBoundCodeVisionProviderFactory.createProviders(DaemonBoundCodeVisionProviderFactory.kt:10)
	at com.intellij.codeInsight.codeVision.CodeVisionProviderFactory$Companion.createAllProviders$lambda$0(CodeVisionProviderFactory.kt:21)
	at com.intellij.codeInsight.codeVision.CodeVisionProviderFactory$Companion.createAllProviders$lambda$1(CodeVisionProviderFactory.kt:20)
	at com.intellij.openapi.extensions.ExtensionPointName.forEachExtensionSafe(ExtensionPointName.kt:62)
	at com.intellij.codeInsight.codeVision.CodeVisionProviderFactory$Companion.createAllProviders(CodeVisionProviderFactory.kt:20)
	at com.intellij.codeInsight.codeVision.CodeVisionHost.<init>(CodeVisionHost.kt:118)
	at java.base/java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:735)
	at com.intellij.platform.instanceContainer.instantiation.InstantiateKt.instantiate$lambda$0(instantiate.kt:52)
	at com.intellij.platform.instanceContainer.instantiation.InstantiateKt.instantiate$lambda$3$0(instantiate.kt:294)
	at com.intellij.platform.instanceContainer.instantiation.InstantiateKt.withStoredTemporaryContext(instantiate.kt:310)
	at com.intellij.platform.instanceContainer.instantiation.InstantiateKt.instantiate(instantiate.kt:293)
	at com.intellij.platform.instanceContainer.instantiation.InstantiateKt.instantiate(instantiate.kt:45)
	at com.intellij.serviceContainer.ServiceInstanceInitializer.createInstance$suspendImpl(ServiceInstanceInitializer.kt:33)
	at com.intellij.serviceContainer.ServiceInstanceInitializer.createInstance(ServiceInstanceInitializer.kt)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder$initialize$1$1.invokeSuspend(LazyInstanceHolder.kt:181)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder$initialize$1$1.invoke(LazyInstanceHolder.kt)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder$initialize$1$1.invoke(LazyInstanceHolder.kt)
	at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndspatched(Undispatched.kt:67)
	at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:43)
	at kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext(Builders.common.kt:165)
	at kotlinx.coroutines.BuildersKt.withContext(Unknown Source)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder$initialize$1.invokeSuspend(LazyInstanceHolder.kt:179)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder$initialize$1.invoke(LazyInstanceHolder.kt)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder$initialize$1.invoke(LazyInstanceHolder.kt)
	at kotlinx.coroutines.intrinsics.UndispatchedKt.startCoroutineUndispatched(Undispatched.kt:20)
	at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:360)
	at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:134)
	at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:53)
	at kotlinx.coroutines.BuildersKt.launch(Unknown Source)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder.initialize(LazyInstanceHolder.kt:164)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder.access$initialize(LazyInstanceHolder.kt:29)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder.tryInitialize(LazyInstanceHolder.kt:154)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder.getInstance(LazyInstanceHolder.kt:112)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder.getInstance$suspendImpl(LazyInstanceHolder.kt:100)
	at com.intellij.platform.instanceContainer.internal.LazyInstanceHolder.getInstance(LazyInstanceHolder.kt)
	at com.intellij.platform.instanceContainer.internal.InstanceContainerImpl.instance(InstanceContainerImpl.kt:83)
	at com.intellij.serviceContainer.ComponentManagerImpl.getServiceAsync(ComponentManagerImpl.kt:744)
	at com.intellij.codeInsight.codeVision.AppCodeVisionInitializationHost.runForProjectIfNotInitialized(CodeVisionInitializer.kt:50)
	at com.intellij.codeInsight.codeVision.CodeVisionInitializer$CodeVisionInitializerStartupActivity.execute(CodeVisionInitializer.kt:28)
	at com.intellij.ide.startup.impl.StartupManagerImplKt$launchActivity$1.invokeSuspend(StartupManagerImpl.kt:536)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:34)
	at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:610)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runDefaultDispatcherTask(CoroutineScheduler.kt:1194)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:906)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:775)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:762)

I encountered the same problem, but as @m0rkeulv pointed out including the kotlin plugin, e.g. testBundledPlugin("org.jetbrains.kotlin") helps.