Fix installation

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

@@ -1,5 +1,6 @@
 import org.gradle.jvm.tasks.Jar
 import org.jetbrains.intellij.platform.gradle.extensions.intellijPlatform
+import java.util.zip.ZipFile
 
 plugins {
   id("intellij-plugin-common-conventions")
@@ -36,6 +37,31 @@ afterEvaluate {
   }
 }
 
+val verifyModuleDescriptor = tasks.register("verifyModuleDescriptor") {
+  val composedJar = tasks.named<Jar>("composedJar")
+  inputs.file(composedJar.flatMap { it.archiveFile })
+  doLast {
+    val archive = composedJar.get().archiveFile.get().asFile
+    ZipFile(archive).use { zip ->
+      val descriptors = zip.entries().asSequence().filter { entry ->
+        !entry.isDirectory && '/' !in entry.name && entry.name.endsWith(".xml")
+      }
+      for (descriptor in descriptors) {
+        val content = zip.getInputStream(descriptor).bufferedReader().use { it.readText() }
+        check(!Regex("""<\s*xi:include\b""").containsMatchIn(content)) {
+          "Module descriptor `${archive.name}!/${descriptor.name}` contains an XInclude. " +
+            "IntelliJ loads descriptors from separate module JARs without an XInclude path resolver; " +
+            "generate a flattened descriptor instead."
+        }
+      }
+    }
+  }
+}
+
+tasks.named<Jar>("composedJar") {
+  finalizedBy(verifyModuleDescriptor)
+}
+
 fun findModuleDescriptorName(): String? {
   val resourcesDirs = sourceSets.main.get().resources.srcDirs
   for (resourcesDir in resourcesDirs) {

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

@@ -2,6 +2,18 @@ plugins {
   id("intellij-plugin-module-conventions")
 }
 
+private val riderPlatformModuleDependenciesMarker = "<!-- RIDER_PLATFORM_MODULE_DEPENDENCIES -->"
+private val riderPlatformModuleDependencies = if (environmentName.toInt() >= 262) {
+  listOf(
+    "intellij.rd.client",
+    "intellij.rider.languages",
+    "intellij.rider.rdclient.dotnet",
+  ).joinToString("\n") { "    <module name=\"$it\"/>" }
+}
+else {
+  ""
+}
+
 dependencies {
   intellijPlatform {
     intellijIde(riderVersion)
@@ -23,6 +35,15 @@ dependencies {
 }
 
 tasks {
+  processResources {
+    inputs.property("riderPlatformModuleDependencies", riderPlatformModuleDependencies)
+    filesMatching("hs-CSharp.xml") {
+      filter { line ->
+        if (riderPlatformModuleDependenciesMarker in line) riderPlatformModuleDependencies else line
+      }
+    }
+  }
+
   // Tests are disabled due to failures on TeamCity with 2025.2+
   // Rider's testFramework.jar location differs from other IDEs
   // TODO: EDU-XXXX - investigate and fix CSharp test failures

intellij-plugin/hs-CSharp/resources/hs-CSharp.xml

@@ -1,16 +1,13 @@
-<idea-plugin xmlns:xi="http://www.w3.org/2001/XInclude" package="org.hyperskill.academy.csharp">
+<idea-plugin package="org.hyperskill.academy.csharp">
   <!--suppress PluginXmlValidity -->
   <dependencies>
     <plugin id="com.intellij.modules.rider"/>
     <plugin id="com.intellij.resharper.unity"/>
     <module name="intellij.rider"/>
+    <!-- Rider 2026.2+ module dependencies are inserted here by build.gradle.kts. -->
+    <!-- RIDER_PLATFORM_MODULE_DEPENDENCIES -->
   </dependencies>
 
-  <!-- Rider 2026.2 splits these APIs out of `intellij.rider`. -->
-  <xi:include href="/META-INF/rider-platform-modules.xml">
-    <xi:fallback/>
-  </xi:include>
-
   <resource-bundle>messages.EduCoreBundle</resource-bundle>
 
   <actions>