Projects and java fixes

buildSrc/src/main/kotlin/intellij-plugin-common-conventions.gradle.kts

@@ -147,14 +147,20 @@ private fun findModulePackage(project: Project): String? {
 private fun verifyClasses(project: Project) {
   val pkg = findModulePackage(project) ?: return
   val expectedDir = pkg.replace('.', '/')
+  // Packages the module explicitly opted out for, see `VERIFY_CLASSES_ALLOWED_PACKAGES`.
+  val allowedDirs = (project.findProperty(VERIFY_CLASSES_ALLOWED_PACKAGES) as? String)
+    .orEmpty()
+    .split(',')
+    .map { it.trim().replace('.', '/') }
+    .filter { it.isNotEmpty() }
 
   var hasErrors = false
   for (classesDir in project.sourceSets.main.get().output.classesDirs) {
     val basePath = classesDir.toPath()
     for (file in classesDir.walk()) {
       if (file.isFile && file.extension == "class") {
         val relativePath = basePath.relativize(file.toPath())
-        if (!relativePath.startsWith(expectedDir)) {
+        if (!relativePath.startsWith(expectedDir) && allowedDirs.none { relativePath.startsWith(it) }) {
           logger.error("Wrong package of `${relativePath.joinToString(".").removeSuffix(".class")}` class. Expected `$pkg`")
           hasErrors = true
         }

buildSrc/src/main/kotlin/intellijUtils.kt

@@ -8,6 +8,13 @@ import kotlin.reflect.KProperty
 
 const val VERIFY_CLASSES_TASK_NAME = "verifyClasses"
 
+/**
+ * Extra property a module sets to let [VERIFY_CLASSES_TASK_NAME] accept classes outside its own package.
+ * Comma-separated package prefixes. Only for shims that must sit in a platform package to reach its
+ * package-private or `internal` API -- there is no other way to call it.
+ */
+const val VERIFY_CLASSES_ALLOWED_PACKAGES = "verifyClassesAllowedPackages"
+
 private const val IDE_IDEA = "idea"
 private const val IDE_CLION = "clion"
 private const val IDE_PYCHARM = "pycharm"

gradle-252.properties

@@ -4,7 +4,7 @@ customUntilBuild=252.*
 # Existent IDE versions can be found in the following repos:
 # https://www.jetbrains.com/intellij-repository/releases/
 # https://www.jetbrains.com/intellij-repository/snapshots/
-ideaVersion=IU-2025.2.4
-clionVersion=CL-2025.2.4
-pycharmVersion=PC-2025.2.4
-riderVersion=RD-2025.2.4
+ideaVersion=IU-2025.2.6.3
+clionVersion=CL-2025.2.6.2
+pycharmVersion=PC-2025.2.6.2
+riderVersion=RD-2025.2.6.1

gradle-253.properties

@@ -4,7 +4,7 @@ customUntilBuild=253.*
 # Existent IDE versions can be found in the following repos:
 # https://www.jetbrains.com/intellij-repository/releases/
 # https://www.jetbrains.com/intellij-repository/snapshots/
-ideaVersion=IU-2025.3
-clionVersion=CL-2025.3
-pycharmVersion=PC-2025.3
-riderVersion=RD-2025.3
+ideaVersion=IU-2025.3.6.1
+clionVersion=CL-2025.3.6.1
+pycharmVersion=PC-2025.3.6.1
+riderVersion=RD-2025.3.5

gradle.properties

@@ -1,7 +1,7 @@
 # supported values: 252, 253, 261, 262
 environmentName=262
 
-pluginVersion=2026.18
+pluginVersion=2026.20
 
 # type of IDE (IDEA, CLion, etc.) used to build/test running
 # for more details see `Different IDEs` section in `PlatformVersions.md`

gradle/libs.versions.toml

@@ -1,39 +1,39 @@
 [versions]
 educational-ml-library = "1.0.65"
-jackson = "2.21.2"
-kotlin = "2.3.21"
-okhttp = "5.3.2"
+jackson = "2.22.2"
+kotlin = "2.4.10"
+okhttp = "5.5.0"
 retrofit = "3.0.0"
 
 [libraries]
-annotations = { group = "org.jetbrains", name = "annotations", version = "23.0.0" }
-clikt-core = { module = "com.github.ajalt.clikt:clikt-core", version = "5.0.1" }
+annotations = { group = "org.jetbrains", name = "annotations", version = "26.1.0" }
+clikt-core = { module = "com.github.ajalt.clikt:clikt-core", version = "5.1.0" }
 converter-jackson = { group = "com.squareup.retrofit2", name = "converter-jackson", version.ref = "retrofit" }
 educational-ml-library-core = { group = "com.jetbrains.educational.ml", name = "educational-ml-library-core", version.ref = "educational-ml-library" }
 educational-ml-library-debugger = { group = "com.jetbrains.educational.ml", name = "educational-ml-library-debugger", version.ref = "educational-ml-library" }
 jackson-dataformat-yaml = { group = "com.fasterxml.jackson.dataformat", name = "jackson-dataformat-yaml", version.ref = "jackson" }
 jackson-datatype-jsr310 = { group = "com.fasterxml.jackson.datatype", name = "jackson-datatype-jsr310", version.ref = "jackson" }
 jackson-module-kotlin = { group = "com.fasterxml.jackson.module", name = "jackson-module-kotlin", version.ref = "jackson" }
-jsoup = { group = "org.jsoup", name = "jsoup", version = "1.17.2" }
-kotlin-css-jvm = { group = "org.jetbrains.kotlin-wrappers", name = "kotlin-css-jvm", version = "2026.4.12" }
+jsoup = { group = "org.jsoup", name = "jsoup", version = "1.23.1" }
+kotlin-css-jvm = { group = "org.jetbrains.kotlin-wrappers", name = "kotlin-css-jvm", version = "2026.8.4" }
 kotlin-stdlib = { group = "org.jetbrains.kotlin", name = "kotlin-stdlib", version.ref = "kotlin" }
-kotlinx-serialization = { group = "org.jetbrains.kotlinx", name = "kotlinx-serialization-json", version = "1.8.0" }
+kotlinx-serialization = { group = "org.jetbrains.kotlinx", name = "kotlinx-serialization-json", version = "1.9.0" }
 logging-interceptor = { group = "com.squareup.okhttp3", name = "logging-interceptor", version.ref = "okhttp" }
 okhttp = { group = "com.squareup.okhttp3", name = "okhttp", version.ref = "okhttp" }
 retrofit = { group = "com.squareup.retrofit2", name = "retrofit", version.ref = "retrofit" }
 
 # test dependencies
-classgraph = { module = "io.github.classgraph:classgraph", version = "4.8.179" }
+classgraph = { module = "io.github.classgraph:classgraph", version = "4.8.193" }
 junit = { group = "junit", name = "junit", version = "4.13.2" }
 kotlin-test-junit = { group = "org.jetbrains.kotlin", name = "kotlin-test-junit", version.ref = "kotlin" }
-mockk = { group = "io.mockk", name = "mockk", version = "1.13.13" }
+mockk = { group = "io.mockk", name = "mockk", version = "1.14.11" }
 mockwebserver = { group = "com.squareup.okhttp3", name = "mockwebserver", version.ref = "okhttp" }
 openTest4J = { group = "org.opentest4j", name = "opentest4j", version = "1.3.0" }
-hamcrest = { group = "org.hamcrest", name = "hamcrest", version="2.2" }
+hamcrest = { group = "org.hamcrest", name = "hamcrest", version="3.0" }
 
 [plugins]
-intelliJPlatformPlugin = { id = "org.jetbrains.intellij.platform", version = "2.15.0" }
+intelliJPlatformPlugin = { id = "org.jetbrains.intellij.platform", version = "2.18.1" }
 kotlinPlugin = { id = "org.jetbrains.kotlin.jvm", version.ref = "kotlin" }
 kotlinSerializationPlugin = { id = "org.jetbrains.kotlin.plugin.serialization", version.ref = "kotlin" }
 propertiesPlugin = { id = "net.saliman.properties", version = "1.6.0" }
-testRetryPlugin = { id = "org.gradle.test-retry", version = "1.6.4" }
+testRetryPlugin = { id = "org.gradle.test-retry", version = "1.6.5" }

hs-edu-format/src/org/hyperskill/academy/learning/courseFormat/ItemContainer.kt

@@ -20,18 +20,28 @@ abstract class ItemContainer : StudyItem() {
     return items.firstOrNull { it.name == name }
   }
 
+  /**
+   * Adding an item also makes this container its [StudyItem.parent].
+   *
+   * Otherwise the item would stay in the container while [StudyItem.parent] throws, and every consumer walking up
+   * the tree (course view presentation, YAML reload, task description) breaks on an item that looks perfectly fine
+   * in [items]. [init] still (re)initializes a whole subtree, this only keeps a single insertion consistent.
+   */
   fun addItem(item: StudyItem) {
     _items.add(item)
+    item.parent = this
   }
 
   fun addItem(index: Int, item: StudyItem) {
     _items.add(index, item)
+    item.parent = this
   }
 
   fun replaceItem(existingItem: StudyItem, newItem: StudyItem) {
     val index = _items.indexOf(existingItem)
     if (index < 0) return
     _items[index] = newItem
+    newItem.parent = this
   }
 
   fun removeItem(item: StudyItem) {

hs-edu-format/src/org/hyperskill/academy/learning/courseFormat/StudyItem.kt

@@ -23,6 +23,22 @@ abstract class StudyItem() {
   var id: Int = 0 // id on remote resource (Stepik, Marketplace)
   var contentTags: List<String> = listOf()
 
+  /**
+   * `true` when this item's children could not be fully resolved during the last load: a child directory or its config
+   * file was missing, or a child failed to deserialize. Such an item holds fewer children than the config file on disk
+   * claims, so writing it back would persist the truncated `content:` list and permanently drop the missing children.
+   *
+   * [org.hyperskill.academy.learning.yaml.YamlFormatSynchronizer.saveItem] refuses to write the *structural* config
+   * while this is set; the remote config keeps being written, as it holds no `content:` list.
+   * It is recomputed on every load rather than latched, so a later complete load clears it again.
+   *
+   * Note this covers children only. A [org.hyperskill.academy.learning.courseFormat.tasks.Task] whose task files
+   * could not be resolved is deliberately *not* marked here: its `status` lives in the same config file, so blocking
+   * the save would stop the solved state from being persisted.
+   */
+  @Transient
+  var isPartiallyLoaded: Boolean = false
+
   @Transient
   private var _parent: ItemContainer? = null
 

hs-edu-format/src/org/hyperskill/academy/learning/network/RetrofitExt.kt

@@ -121,34 +121,41 @@ fun <T> Response<T>.executeParsingErrors(omitErrors: Boolean = false): Result<Re
       Err("${message("error.service.maintenance")}\n\n$error") // 502, 503
     in HTTP_INTERNAL_ERROR..HTTP_VERSION ->
       Err("${message("error.service.down")}\n\n$error") // 500x
-    HTTP_FORBIDDEN, HTTP_UNAUTHORIZED -> {
-      val errorMessage = processForbiddenErrorMessage(error) ?: message("error.access.denied")
-      Err(errorMessage)
-    }
+    // 401 means the access token is not valid anymore, and it's the generic message that makes
+    // `StepikBasedConnector.withTokenRefreshIfFailed` refresh the tokens and repeat the request
+    HTTP_UNAUTHORIZED -> Err(processErrorMessage(error, MESSAGE_FIELD) ?: message("error.access.denied"))
+
+    // Unlike 401, 403 is not about an expired token: the server explains why the request is not allowed,
+    // e.g. that the stage is locked behind a subscription, so its own text is the useful one
+    HTTP_FORBIDDEN -> Err(processErrorMessage(error, MESSAGE_FIELD, DETAIL_FIELD) ?: message("error.access.denied"))
 
     HTTP_UNAVAILABLE_FOR_LEGAL_REASONS -> { // 451
       LOG.warning(message("error.agreement.not.accepted"))
       Err(fullErrorText)
     }
 
-    in HTTP_BAD_REQUEST..HTTP_UNSUPPORTED_TYPE ->
-      Err(message("error.unexpected.error", error)) // 400x
+    in HTTP_BAD_REQUEST..HTTP_UNSUPPORTED_TYPE -> // 400x
+      Err(processErrorMessage(error, MESSAGE_FIELD, DETAIL_FIELD) ?: message("error.unexpected.error", error))
     else -> {
       LOG.warning("Code $code is not handled")
       Err(message("error.unexpected.error", error))
     }
   }
 }
 
-private fun processForbiddenErrorMessage(jsonText: String): String? {
+/**
+ * Extracts the explanation the server put into the error body, looking at [fields] in the given order.
+ * Returns `null` when the body is not a JSON object or none of the fields carries any text.
+ */
+private fun processErrorMessage(jsonText: String, vararg fields: String): String? {
   return try {
     val factory = JsonFactory()
     val mapper = ObjectMapper(factory)
     val module = SimpleModule()
     mapper.registerModule(module)
     mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
-    val courseNode = mapper.readTree(jsonText) as ObjectNode
-    courseNode.get("message")?.asText()
+    val errorNode = mapper.readTree(jsonText) as ObjectNode
+    fields.firstNotNullOfOrNull { field -> errorNode.get(field)?.asText()?.takeIf { it.isNotBlank() } }
   }
   catch (_: ClassCastException) {
     null
@@ -158,4 +165,7 @@ private fun processForbiddenErrorMessage(jsonText: String): String? {
   }
 }
 
+private const val MESSAGE_FIELD = "message"
+private const val DETAIL_FIELD = "detail"
+
 const val HTTP_UNAVAILABLE_FOR_LEGAL_REASONS: Int = 451

intellij-plugin/hs-Go/build.gradle.kts

@@ -7,7 +7,7 @@ dependencies {
     intellijIde(ideaVersion)
     bundledModulesSince(ideaVersion, 262, "intellij.platform.smRunner", "intellij.platform.testRunner")
 
-    intellijPlugins(goPlugin, intelliLangPlugin)
+    intellijPlugins(goPlugin)
     // Workaround to make tests work - the module is not loaded automatically
     bundledModule("com.intellij.modules.ultimate")
     testIntellijPlatformFramework(project)

intellij-plugin/hs-Java/src/org/hyperskill/academy/java/JLanguageSettings.kt

@@ -1,27 +1,14 @@
 package org.hyperskill.academy.java
 
-import com.intellij.openapi.projectRoots.JavaSdk
 import com.intellij.openapi.projectRoots.JavaSdkVersion
-import com.intellij.openapi.roots.ui.configuration.projectRoot.ProjectSdksModel
 import org.hyperskill.academy.jvm.JavaVersionParseSuccess
 import org.hyperskill.academy.jvm.JdkLanguageSettings
 import org.hyperskill.academy.jvm.ParsedJavaVersion
 import org.hyperskill.academy.learning.courseFormat.Course
 
 open class JLanguageSettings : JdkLanguageSettings() {
 
-  // Note: setupProjectSdksModel is intentionally not overridden here.
-  // Adding SDK via model.addSdk() on EDT is prohibited in IntelliJ 2025.3+.
-  // Bundled JDK is added in addBundledJdkIfNeeded() which is called from background thread.
-
-  override fun addBundledJdkIfNeeded(model: ProjectSdksModel) {
-    val (jdkPath, sdk) = findBundledJdk(model) ?: return
-    if (sdk == null) {
-      model.addSdk(JavaSdk.getInstance(), jdkPath, null)
-    }
-  }
-
-  override fun minJvmSdkVersion(course: Course): ParsedJavaVersion {
+  override fun requiredJdkVersion(course: Course): ParsedJavaVersion {
     val javaVersionDescription = course.languageVersion ?: return JavaVersionParseSuccess(DEFAULT_JAVA)
     return ParsedJavaVersion.fromJavaSdkDescriptionString(javaVersionDescription)
   }

intellij-plugin/hs-Java/src/org/hyperskill/academy/java/hyperskill/JHyperskillConfigurator.kt

@@ -6,10 +6,10 @@ import org.hyperskill.academy.java.JConfigurator
 import org.hyperskill.academy.java.JCourseBuilder
 import org.hyperskill.academy.jvm.JdkLanguageSettings
 import org.hyperskill.academy.jvm.JdkProjectSettings
-import org.hyperskill.academy.jvm.ParsedJavaVersion
 import org.hyperskill.academy.jvm.gradle.GradleCourseBuilderBase
 import org.hyperskill.academy.jvm.gradle.GradleHyperskillConfigurator
 import org.hyperskill.academy.jvm.gradle.generation.GradleCourseProjectGenerator
+import org.hyperskill.academy.jvm.requiredJdkVersion
 import org.hyperskill.academy.learning.EduCourseBuilder
 import org.hyperskill.academy.learning.EduNames
 import org.hyperskill.academy.learning.courseFormat.Course
@@ -45,10 +45,9 @@ class JHyperskillConfigurator : GradleHyperskillConfigurator<JdkProjectSettings>
     GradleCourseProjectGenerator(builder, course) {
 
     override fun getJdk(settings: JdkProjectSettings): Sdk? {
-      return super.getJdk(settings) ?: JdkLanguageSettings.findSuitableJdk(
-        ParsedJavaVersion.fromJavaSdkDescriptionString(course.languageVersion),
-        settings.model
-      )
+      // `course.languageVersion` is the language level of a Hyperskill Java course ("11"), not the JDK its checker
+      // needs, so it must not be used here: it would accept a JDK the course cannot be checked with
+      return super.getJdk(settings) ?: JdkLanguageSettings.findSuitableJdk(course.requiredJdkVersion, settings.model)
     }
   }
 

intellij-plugin/hs-Java/src/org/hyperskill/academy/java/hyperskill/JHyperskillLanguageSettings.kt

@@ -7,7 +7,7 @@ import org.hyperskill.academy.jvm.hyperskillJdkVersion
 import org.hyperskill.academy.learning.courseFormat.Course
 
 class JHyperskillLanguageSettings : JLanguageSettings() {
-  override fun minJvmSdkVersion(course: Course): ParsedJavaVersion {
+  override fun requiredJdkVersion(course: Course): ParsedJavaVersion {
     return JavaVersionParseSuccess(hyperskillJdkVersion)
   }
 }

intellij-plugin/hs-Python/build.gradle.kts

@@ -2,6 +2,11 @@ plugins {
   id("intellij-plugin-module-conventions")
 }
 
+// `branches/261|262/src/com/jetbrains/python/**` holds copies of and shims around Python plugin internals
+// (`PyTargetEnvCreationManager`, the `compat.kt` files). They call package-private and `internal` members of the
+// Python plugin, which is only possible from that plugin's own package, so `verifyClasses` has to allow them.
+ext[VERIFY_CLASSES_ALLOWED_PACKAGES] = "com.jetbrains.python"
+
 private val pythonPlatformModuleDependenciesMarker = "<!-- PYTHON_PLATFORM_MODULE_DEPENDENCIES -->"
 private val pythonPlatformModuleDependencies = if (environmentName.toInt() >= 262) {
   listOf(

intellij-plugin/hs-core/branches/252/src/org/hyperskill/academy/platform/TestOnlyThreadingCompat.kt

@@ -0,0 +1,12 @@
+package org.hyperskill.academy.platform
+
+/**
+ * `com.intellij.openapi.application.impl.TestOnlyThreading` only exists since 2025.3.
+ * On 2025.2 the caller does not hold the write intent lock while dispatching invocation events, so the action runs
+ * as is -- exactly what this code did before the lock dance was introduced in `Release fixes (#54)`.
+ *
+ * BACKCOMPAT: 252 -- drop this branch copy once 2025.2 is no longer supported.
+ */
+fun runWithoutWriteIntentLock(action: () -> Unit) {
+  action()
+}

intellij-plugin/hs-core/branches/253/src/org/hyperskill/academy/platform/TestOnlyThreadingCompat.kt

@@ -0,0 +1,12 @@
+package org.hyperskill.academy.platform
+
+import com.intellij.openapi.application.impl.TestOnlyThreading
+
+/**
+ * On 2025.3 `releaseTheAcquiredWriteIntentLockThenExecuteActionAndTakeWriteIntentLockBack` is a Kotlin function
+ * taking `() -> T` and returning its result. Since 2026.1 it takes a `java.lang.Runnable` and returns nothing,
+ * and on 2025.2 the class does not exist at all -- hence one copy of this shim per branch.
+ */
+fun runWithoutWriteIntentLock(action: () -> Unit) {
+  TestOnlyThreading.releaseTheAcquiredWriteIntentLockThenExecuteActionAndTakeWriteIntentLockBack(action)
+}

intellij-plugin/hs-core/branches/261/src/org/hyperskill/academy/platform/TestOnlyThreadingCompat.kt

@@ -0,0 +1,12 @@
+package org.hyperskill.academy.platform
+
+import com.intellij.openapi.application.impl.TestOnlyThreading
+
+/**
+ * Since 2026.1 `releaseTheAcquiredWriteIntentLockThenExecuteActionAndTakeWriteIntentLockBack` takes a
+ * `java.lang.Runnable` and returns nothing. On 2025.3 it takes a Kotlin `() -> T`, and on 2025.2 the class does not
+ * exist at all -- hence one copy of this shim per branch.
+ */
+fun runWithoutWriteIntentLock(action: () -> Unit) {
+  TestOnlyThreading.releaseTheAcquiredWriteIntentLockThenExecuteActionAndTakeWriteIntentLockBack(Runnable { action() })
+}

intellij-plugin/hs-core/branches/262/src/org/hyperskill/academy/platform/TestOnlyThreadingCompat.kt

@@ -0,0 +1,12 @@
+package org.hyperskill.academy.platform
+
+import com.intellij.openapi.application.impl.TestOnlyThreading
+
+/**
+ * Since 2026.1 `releaseTheAcquiredWriteIntentLockThenExecuteActionAndTakeWriteIntentLockBack` takes a
+ * `java.lang.Runnable` and returns nothing. On 2025.3 it takes a Kotlin `() -> T`, and on 2025.2 the class does not
+ * exist at all -- hence one copy of this shim per branch.
+ */
+fun runWithoutWriteIntentLock(action: () -> Unit) {
+  TestOnlyThreading.releaseTheAcquiredWriteIntentLockThenExecuteActionAndTakeWriteIntentLockBack(Runnable { action() })
+}

intellij-plugin/hs-core/resources/fileTemplates/internal/hyperskill-settings.gradle.ft

@@ -13,6 +13,12 @@ buildscript {
   }
 }
 
+## Lets Gradle download the Java toolchain requested in build.gradle instead of failing with
+## "Toolchain download repositories have not been configured" when that JDK is not installed locally.
+plugins {
+  id 'org.gradle.toolchains.foojay-resolver-convention' version '1.0.0'
+}
+
 ## Should be the same as `org.hyperskill.academy.learning.courseGeneration.GeneratorUtils.sanitizeName`
 
 static String sanitizeName(String name) {

intellij-plugin/hs-core/resources/messages/EduCoreBundle.properties

@@ -246,6 +246,12 @@ error.failed.to.post.solution=Failed to post solution
 error.failed.to.post.solution.to=Failed to post solution to {0}
 error.failed.to.post.solution.with.guide=Failed to post solution to {0}. For more information, \
   see <a href=\"{1}\">the Troubleshooting guide</a>
+# Ex.: Can't post a submission for this stage. Upgrade your subscription.<br/>For more information, \
+#   see <a href="">the Troubleshooting guide</a>
+error.failed.to.post.solution.reason={0}<br/>For more information, \
+  see <a href=\"{1}\">the Troubleshooting guide</a>
+# Ex.: Your solution was not accepted by JetBrains Academy
+error.solution.rejected=Your solution was not accepted by {0}
 hyperskill.error.empty.check.profile=Check profile is empty for task {0}. Please try to {1} or contact support.
 error.failed.to.refresh.tokens=Failed to refresh tokens
 error.invalid.rename.message=This rename operation can break the course