diff --git a/compiler/frontend/src/org/jetbrains/kotlin/script/KotlinScriptDefinition.kt b/compiler/frontend/src/org/jetbrains/kotlin/script/KotlinScriptDefinition.kt
index d6f1ebe089a..ca0d446d522 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/script/KotlinScriptDefinition.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/script/KotlinScriptDefinition.kt
@@ -69,6 +69,13 @@ class KotlinScriptExternalDependenciesUnion(val dependencies: Iterable<KotlinScr
     override val sources: Iterable<File> get() = dependencies.flatMap { it.sources }
 }
 
+fun Iterable<File>.isSameClasspathAs(other: Iterable<File>): Boolean {
+    val c1 = map { it.canonicalPath }.toHashSet()
+    val c2 = other.map { it.canonicalPath }.toHashSet()
+    return c1.size == c2.size &&
+           c1.zip(c2).all { it.first == it.second }
+}
+
 data class ScriptParameter(val name: Name, val type: KotlinType)
 
 fun <TF> getFileName(file: TF): String = when (file) {
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/script/KotlinScriptExternalImportsProvider.kt b/compiler/frontend/src/org/jetbrains/kotlin/script/KotlinScriptExternalImportsProvider.kt
index 587acb6bd33..6ac2ef260fc 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/script/KotlinScriptExternalImportsProvider.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/script/KotlinScriptExternalImportsProvider.kt
@@ -49,6 +49,7 @@ class KotlinScriptExternalImportsProvider(val project: Project, private val scri
         }
     }
 
+    // optimized for initial caching, additional handling of possible duplicates to save a call to distinct
     fun <TF> cacheExternalImports(files: Iterable<TF>): Unit = cacheLock.write {
         val uncached = hashSetOf<String>()
         files.forEach { file ->
@@ -71,6 +72,36 @@ class KotlinScriptExternalImportsProvider(val project: Project, private val scri
         }
     }
 
+    // optimized for update, no special duplicates handling
+    fun <TF: Any> updateExternalImportsCache(files: Iterable<TF>): Iterable<TF> = cacheLock.write {
+        files.mapNotNull { file ->
+            val path = getFilePath(file)
+            val scriptDef = scriptDefinitionProvider.findScriptDefinition(file)
+            if (scriptDef != null) {
+                val deps = scriptDef.getDependenciesFor(file, project)
+                val oldDeps = cache[path]
+                when {
+                    deps != null && (oldDeps == null ||
+                                     !deps.classpath.isSameClasspathAs(oldDeps.classpath) || !deps.sources.isSameClasspathAs(oldDeps.sources)) -> {
+                        // changed or new
+                        cache.put(path, deps)
+                        cacheOfNulls.remove(path)
+                        file
+                    }
+                    deps != null -> {
+                        // same as before
+                        null
+                    }
+                    else -> {
+                        if (cache.remove(path) != null || cacheOfNulls.remove(path)) file // cleared
+                        else null // same as before
+                    }
+                }
+            }
+            else null // not a script
+        }
+    }
+
     fun invalidateCaches() {
         cacheLock.write {
             cache.keys.toList().apply {
diff --git a/idea/idea-core/src/org/jetbrains/kotlin/idea/core/script/KotlinScriptConfigurationManager.kt b/idea/idea-core/src/org/jetbrains/kotlin/idea/core/script/KotlinScriptConfigurationManager.kt
index 429048b2c1d..10e62bd0731 100644
--- a/idea/idea-core/src/org/jetbrains/kotlin/idea/core/script/KotlinScriptConfigurationManager.kt
+++ b/idea/idea-core/src/org/jetbrains/kotlin/idea/core/script/KotlinScriptConfigurationManager.kt
@@ -17,24 +17,33 @@
 package org.jetbrains.kotlin.idea.core.script
 
 import com.intellij.openapi.components.ServiceManager
+import com.intellij.openapi.project.DumbService
 import com.intellij.openapi.project.Project
+import com.intellij.openapi.roots.ex.ProjectRootManagerEx
+import com.intellij.openapi.util.EmptyRunnable
 import com.intellij.openapi.vfs.StandardFileSystems
 import com.intellij.openapi.vfs.VirtualFile
+import com.intellij.openapi.vfs.VirtualFileManager
+import com.intellij.openapi.vfs.newvfs.BulkFileListener
+import com.intellij.openapi.vfs.newvfs.events.VFileEvent
 import com.intellij.psi.search.FileTypeIndex
 import com.intellij.psi.search.GlobalSearchScope
 import com.intellij.util.indexing.IndexableSetContributor
 import com.intellij.util.io.URLUtil
 import org.jetbrains.kotlin.idea.caches.resolve.FileLibraryScope
 import org.jetbrains.kotlin.idea.util.application.runReadAction
+import org.jetbrains.kotlin.idea.util.application.runWriteAction
 import org.jetbrains.kotlin.script.*
 import org.jetbrains.kotlin.utils.PathUtil
 import java.io.File
 import java.io.FileNotFoundException
 import java.util.concurrent.locks.ReentrantReadWriteLock
 import kotlin.concurrent.read
+import kotlin.concurrent.write
 
 class KotlinScriptConfigurationManager(
         private val project: Project,
+        private val dumbService: DumbService,
         private val scriptDefinitionProvider: KotlinScriptDefinitionProvider,
         private val scriptExternalImportsProvider: KotlinScriptExternalImportsProvider?
 ) {
@@ -47,11 +56,28 @@ class KotlinScriptConfigurationManager(
         reloadScriptDefinitions()
         // TODO: sort out read/write action business and if possible make it lazy (e.g. move to getAllScriptsClasspath)
         runReadAction { cacheAllScriptsExtraImports() }
+
+        project.messageBus.connect().subscribe(VirtualFileManager.VFS_CHANGES, object : BulkFileListener.Adapter() {
+            override fun after(events: List<VFileEvent>) {
+                val isChanged = scriptExternalImportsProvider?.updateExternalImportsCache( events.mapNotNull { it.file })?.any() ?: false
+                if (isChanged) {
+                    // TODO: consider more fine-grained update
+                    cacheLock.write {
+                        allScriptsClasspathCache = null
+                    }
+                    notifyRootsChanged()
+                }
+            }
+        })
     }
 
     private var allScriptsClasspathCache: List<VirtualFile>? = null
     private val cacheLock = ReentrantReadWriteLock()
 
+    private fun notifyRootsChanged() {
+        runWriteAction { ProjectRootManagerEx.getInstanceEx(project)?.makeRootsChange(EmptyRunnable.getInstance(), false, true) }
+    }
+
     fun getScriptClasspath(file: VirtualFile): List<VirtualFile> =
             scriptExternalImportsProvider
                     ?.getExternalImports(file)
@@ -61,12 +87,17 @@ class KotlinScriptConfigurationManager(
 
     fun getAllScriptsClasspath(): List<VirtualFile> = cacheLock.read {
         if (allScriptsClasspathCache == null) {
-            allScriptsClasspathCache =
-                    (scriptExternalImportsProvider?.getKnownCombinedClasspath() ?: emptyList())
-                    .distinct()
-                    .mapNotNull { it.classpathEntryToVfs() }
+            dumbService.runWhenSmart {
+                cacheLock.write {
+                    allScriptsClasspathCache =
+                            (scriptExternalImportsProvider?.getKnownCombinedClasspath() ?: emptyList())
+                                    .distinct()
+                                    .mapNotNull { it.classpathEntryToVfs() }
+                }
+                notifyRootsChanged()
+            }
         }
-        return allScriptsClasspathCache!!
+        return allScriptsClasspathCache ?: emptyList()
     }
 
     private fun File.classpathEntryToVfs(): VirtualFile =