diff --git a/analysis/analysis-api-standalone/src/org/jetbrains/kotlin/analysis/api/standalone/StandaloneAnalysisAPISessionBuilder.kt b/analysis/analysis-api-standalone/src/org/jetbrains/kotlin/analysis/api/standalone/StandaloneAnalysisAPISessionBuilder.kt
index fb954786cb7..f2f15ce3cec 100644
--- a/analysis/analysis-api-standalone/src/org/jetbrains/kotlin/analysis/api/standalone/StandaloneAnalysisAPISessionBuilder.kt
+++ b/analysis/analysis-api-standalone/src/org/jetbrains/kotlin/analysis/api/standalone/StandaloneAnalysisAPISessionBuilder.kt
@@ -24,7 +24,6 @@ import org.jetbrains.kotlin.analysis.api.standalone.base.project.structure.Stand
 import org.jetbrains.kotlin.analysis.decompiled.light.classes.ClsJavaStubByVirtualFileCache
 import org.jetbrains.kotlin.analysis.low.level.api.fir.api.services.FirSealedClassInheritorsProcessorFactory
 import org.jetbrains.kotlin.analysis.low.level.api.fir.project.structure.LLFirBuiltinsSessionFactory
-import org.jetbrains.kotlin.analysis.low.level.api.fir.project.structure.LLFirLibrarySessionFactory
 import org.jetbrains.kotlin.analysis.project.structure.KtModuleScopeProvider
 import org.jetbrains.kotlin.analysis.project.structure.KtModuleScopeProviderImpl
 import org.jetbrains.kotlin.analysis.project.structure.ProjectStructureProvider
@@ -59,6 +58,11 @@ public class StandaloneAnalysisAPISessionBuilder(
     projectDisposable: Disposable,
 ) {
     init {
+        // We depend on swing (indirectly through PSI or something), so we want to declare headless mode,
+        // to avoid accidentally starting the UI thread. But, don't set it if it was set externally.
+        if (System.getProperty("java.awt.headless") == null) {
+            System.setProperty("java.awt.headless", "true")
+        }
         setupIdeaStandaloneExecution()
     }