diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/AbstractCompilerBasedTestForFir.kt b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/AbstractCompilerBasedTestForFir.kt
index 5b3a760cca9..de24e0cea9d 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/AbstractCompilerBasedTestForFir.kt
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/AbstractCompilerBasedTestForFir.kt
@@ -47,6 +47,7 @@ abstract class AbstractCompilerBasedTestForFir : AbstractCompilerBasedTest() {
         configureTest()
         defaultConfiguration(this)
         registerAnalysisApiBaseTestServices(disposable, FirLowLevelCompilerBasedTestConfigurator)
+        usePreAnalysisHandlers(::SealedClassesInheritorsCaclulatorPreAnalysisHandler)
 
         firHandlersStep {
             useHandlers(::LLDiagnosticParameterChecker)
diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/LowLevelFirAnalyzerFacade.kt b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/LowLevelFirAnalyzerFacade.kt
index c0dcfbf9ce4..7d6304d0f1c 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/LowLevelFirAnalyzerFacade.kt
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/LowLevelFirAnalyzerFacade.kt
@@ -30,7 +30,6 @@ class LowLevelFirAnalyzerFacade(
         get() = ScopeSession()
 
     override fun runCheckers(): Map<FirFile, List<KtDiagnostic>> {
-        findSealedInheritors()
         return allFirFiles.values.associateWith { firFile ->
             val ktFile = firFile.psi as KtFile
             val diagnostics = ktFile.collectDiagnosticsForFile(firResolveSession, diagnosticCheckerFilter)
@@ -39,14 +38,6 @@ class LowLevelFirAnalyzerFacade(
         }
     }
 
-    private fun findSealedInheritors() {
-        allFirFiles.values.forEach { firFile ->
-            firFile.ensureResolved(FirResolvePhase.SUPER_TYPES)
-        }
-        val sealedProcessor = FirSealedClassInheritorsProcessor(allFirFiles.values.first().moduleData.session, ScopeSession())
-        sealedProcessor.process(allFirFiles.values)
-    }
-
     override fun runResolution(): List<FirFile> = shouldNotBeCalled()
     override fun convertToIr(fir2IrExtensions: Fir2IrExtensions): Fir2IrResult = shouldNotBeCalled()
 }
diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/SealedClassesInheritorsCaclulatorPreAnalysisHandler.kt b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/SealedClassesInheritorsCaclulatorPreAnalysisHandler.kt
index 494ddc2813e..4e46f1442ef 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/SealedClassesInheritorsCaclulatorPreAnalysisHandler.kt
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/compiler/based/SealedClassesInheritorsCaclulatorPreAnalysisHandler.kt
@@ -5,15 +5,19 @@
 
 package org.jetbrains.kotlin.analysis.low.level.api.fir.compiler.based
 
+import org.jetbrains.kotlin.analysis.low.level.api.fir.api.LLFirResolveSession
 import org.jetbrains.kotlin.analysis.low.level.api.fir.api.getOrBuildFirFile
-import org.jetbrains.kotlin.analysis.low.level.api.fir.api.getFirResolveSession
+import org.jetbrains.kotlin.analysis.low.level.api.fir.api.services.FirSealedClassInheritorsProcessorFactory
+import org.jetbrains.kotlin.analysis.low.level.api.fir.createFirResolveSessionForNoCaching
+import org.jetbrains.kotlin.analysis.low.level.api.fir.services.LLFirSealedClassInheritorsProcessorFactoryForTests
 import org.jetbrains.kotlin.analysis.project.structure.ProjectStructureProvider
 import org.jetbrains.kotlin.analysis.test.framework.project.structure.ktModuleProvider
 import org.jetbrains.kotlin.fir.declarations.FirFile
+import org.jetbrains.kotlin.fir.declarations.FirRegularClass
 import org.jetbrains.kotlin.fir.declarations.FirResolvePhase
-import org.jetbrains.kotlin.fir.resolve.ScopeSession
 import org.jetbrains.kotlin.fir.resolve.transformers.FirSealedClassInheritorsProcessor
 import org.jetbrains.kotlin.fir.symbols.ensureResolved
+import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.test.services.PreAnalysisHandler
 import org.jetbrains.kotlin.test.services.TestModuleStructure
@@ -27,30 +31,37 @@ class SealedClassesInheritorsCaclulatorPreAnalysisHandler(
     override fun preprocessModuleStructure(moduleStructure: TestModuleStructure) {
     }
 
+    // Manually process all inheritors of sealed classes so that SealedClassInheritorsProviderTestImpl can work correctly for tests.
+    // In the actual IDE, SealedClassInheritorsProviderIdeImpl works by finding inheritors from the index instead of do a
+    // preprocessing of all files. Therefore, the IDE does not rely on such a pre-analysis pass of all files in the module.
     override fun prepareSealedClassInheritors(moduleStructure: TestModuleStructure) {
         val ktFilesByModule = moduleStructure.modules.associateWith { testModule ->
             testServices.ktModuleProvider.getModuleFiles(testModule).filterIsInstance<KtFile>()
         }
 
-        ktFilesByModule.forEach { (testModule, ktFiles) ->
+        for ((testModule, ktFiles) in ktFilesByModule) {
+            if (ktFiles.isEmpty()) continue
             val project = testServices.compilerConfigurationProvider.getProject(testModule)
-            // Manually process all inheritors of sealed classes so that SealedClassInheritorsProviderTestImpl can work correctly for tests.
-            // In the actual IDE, SealedClassInheritorsProviderIdeImpl works by finding inheritors from the index instead of do a
-            // preprocessing of all files. Therefore, the IDE does not rely on such a pre-analysis pass of all files in the module.
             val ktModuleProvider = project.getService(ProjectStructureProvider::class.java)
-            val allFirFiles = mutableListOf<FirFile>()
-            ktFiles.forEach { ktFile ->
-                val ktModule = ktModuleProvider.getKtModuleForKtElement(ktFile)
-                val firResolveSession = ktModule.getFirResolveSession(project)
-                allFirFiles.add(ktFile.getOrBuildFirFile(firResolveSession))
-            }
-            allFirFiles.groupBy { it.moduleData.session }.forEach { (session, firFiles) ->
-                for (firFile in firFiles) {
-                    firFile.ensureResolved(FirResolvePhase.TYPES)
-                }
-                val sealedProcessor = FirSealedClassInheritorsProcessor(session, ScopeSession())
-                sealedProcessor.process(firFiles)
-            }
+            val ktModule = ktFiles.map(ktModuleProvider::getKtModuleForKtElement).distinct().single()
+
+            val tmpFirResolveSession = createFirResolveSessionForNoCaching(ktModule, project)
+            val firFiles = ktFiles.map { it.getOrBuildFirFile(tmpFirResolveSession) }
+            val sealedInheritors = collectSealedClassInheritors(firFiles, tmpFirResolveSession)
+            val provider =
+                project.getService(FirSealedClassInheritorsProcessorFactory::class.java) as LLFirSealedClassInheritorsProcessorFactoryForTests
+            provider.registerInheritors(ktModule, sealedInheritors)
         }
     }
+
+    private fun collectSealedClassInheritors(
+        firFiles: List<FirFile>,
+        tmpFirResolveSession: LLFirResolveSession
+    ): Map<ClassId, List<ClassId>> {
+        firFiles.forEach { it.ensureResolved(FirResolvePhase.TYPES) }
+        val inheritorsCollector = FirSealedClassInheritorsProcessor.InheritorsCollector(tmpFirResolveSession.useSiteFirSession)
+        val sealedClassInheritorsMap = mutableMapOf<FirRegularClass, MutableList<ClassId>>()
+        firFiles.forEach { it.accept(inheritorsCollector, sealedClassInheritorsMap) }
+        return sealedClassInheritorsMap.mapKeys { (firClass, _) -> firClass.symbol.classId }
+    }
 }
diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/services/LLFirSealedClassInheritorsProcessorFactoryForTests.kt b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/services/LLFirSealedClassInheritorsProcessorFactoryForTests.kt
index 3860f7ca12f..0e7a0a94d5e 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/services/LLFirSealedClassInheritorsProcessorFactoryForTests.kt
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/services/LLFirSealedClassInheritorsProcessorFactoryForTests.kt
@@ -6,11 +6,32 @@
 package org.jetbrains.kotlin.analysis.low.level.api.fir.services
 
 import org.jetbrains.kotlin.analysis.low.level.api.fir.api.services.FirSealedClassInheritorsProcessorFactory
+import org.jetbrains.kotlin.analysis.low.level.api.fir.project.structure.llFirModuleData
+import org.jetbrains.kotlin.analysis.project.structure.KtModule
+import org.jetbrains.kotlin.fir.declarations.FirRegularClass
 import org.jetbrains.kotlin.fir.declarations.SealedClassInheritorsProvider
-import org.jetbrains.kotlin.fir.declarations.SealedClassInheritorsProviderImpl
+import org.jetbrains.kotlin.fir.declarations.utils.classId
+import org.jetbrains.kotlin.name.ClassId
 
 internal class LLFirSealedClassInheritorsProcessorFactoryForTests : FirSealedClassInheritorsProcessorFactory() {
-    override fun createSealedClassInheritorsProvider(): SealedClassInheritorsProvider {
-        return SealedClassInheritorsProviderImpl
+    private val inheritorsByModule = mutableMapOf<KtModule, Map<ClassId, List<ClassId>>>()
+
+    fun registerInheritors(ktModule: KtModule, inheritors: Map<ClassId, List<ClassId>>) {
+        inheritorsByModule[ktModule] = inheritors
     }
+
+    override fun createSealedClassInheritorsProvider(): SealedClassInheritorsProvider {
+        return SealedClassInheritorsProviderForTests(inheritorsByModule)
+    }
+}
+
+private class SealedClassInheritorsProviderForTests(
+    private val inheritorsByModule: Map<KtModule, Map<ClassId, List<ClassId>>>
+) : SealedClassInheritorsProvider() {
+    override fun getSealedClassInheritors(firClass: FirRegularClass): List<ClassId> {
+        val ktModule = firClass.llFirModuleData.ktModule
+        val inheritorsForModuleMap = inheritorsByModule.getValue(ktModule)
+        return inheritorsForModuleMap[firClass.classId].orEmpty()
+    }
+
 }
\ No newline at end of file
diff --git a/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/TestRunner.kt b/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/TestRunner.kt
index ea278ef6380..148a9a7a573 100644
--- a/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/TestRunner.kt
+++ b/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/TestRunner.kt
@@ -81,6 +81,10 @@ class TestRunner(private val testConfiguration: TestConfiguration) {
             preprocessor.preprocessModuleStructure(moduleStructure)
         }
 
+        testConfiguration.preAnalysisHandlers.forEach { preprocessor ->
+            preprocessor.prepareSealedClassInheritors(moduleStructure)
+        }
+
         for (module in modules) {
             val shouldProcessNextModules = processModule(module, dependencyProvider)
             if (!shouldProcessNextModules) break
diff --git a/compiler/testData/diagnostics/tests/multimodule/kt14249.kt b/compiler/testData/diagnostics/tests/multimodule/kt14249.kt
index 746330f9db1..77a92d1d3fd 100644
--- a/compiler/testData/diagnostics/tests/multimodule/kt14249.kt
+++ b/compiler/testData/diagnostics/tests/multimodule/kt14249.kt
@@ -1,4 +1,3 @@
-// FIR_IDE_IGNORE
 // FIR_IDENTICAL
 // MODULE: m1
 // FILE: test/Foo.java