diff --git a/Android.bp b/Android.bp
index 34f9bf0..bd4b40f 100644
--- a/Android.bp
+++ b/Android.bp
@@ -161,10 +161,11 @@
     name: "system-build.prop",
     stem: "build.prop",
     product_config: ":product_config",
-    // Currently, only microdroid and cf system image can refer to system-build.prop
+    // Currently, only microdroid, Ravenwood, and cf system image can refer to system-build.prop
     visibility: [
         "//build/make/target/product/generic",
         "//packages/modules/Virtualization/build/microdroid",
+        "//frameworks/base/ravenwood",
     ],
 }
 
diff --git a/android/prebuilt.go b/android/prebuilt.go
index 19f12f0..5d75b62 100644
--- a/android/prebuilt.go
+++ b/android/prebuilt.go
@@ -272,6 +272,25 @@
 	InitPrebuiltModuleWithSrcSupplier(module, srcsSupplier, "srcs")
 }
 
+// InitConfigurablePrebuiltModuleString is the same as InitPrebuiltModule, but uses a
+// Configurable string property instead of a regular list of strings. It only produces a single
+// source file.
+func InitConfigurablePrebuiltModuleString(module PrebuiltInterface, srcs *proptools.Configurable[string], propertyName string) {
+	if srcs == nil {
+		panic(fmt.Errorf("%s must not be nil", propertyName))
+	}
+
+	srcsSupplier := func(ctx BaseModuleContext, _ Module) []string {
+		src := srcs.GetOrDefault(ctx, "")
+		if src == "" {
+			return nil
+		}
+		return []string{src}
+	}
+
+	InitPrebuiltModuleWithSrcSupplier(module, srcsSupplier, propertyName)
+}
+
 func InitSingleSourcePrebuiltModule(module PrebuiltInterface, srcProps interface{}, srcField string) {
 	srcPropsValue := reflect.ValueOf(srcProps).Elem()
 	srcStructField, _ := srcPropsValue.Type().FieldByName(srcField)
diff --git a/filesystem/filesystem.go b/filesystem/filesystem.go
index 1e816a7..8c59df3 100644
--- a/filesystem/filesystem.go
+++ b/filesystem/filesystem.go
@@ -198,6 +198,10 @@
 	unknown
 )
 
+func (fs fsType) IsUnknown() bool {
+	return fs == unknown
+}
+
 type FilesystemInfo struct {
 	// A text file containing the list of paths installed on the partition.
 	FileListFile android.Path
@@ -205,8 +209,7 @@
 
 var FilesystemProvider = blueprint.NewProvider[FilesystemInfo]()
 
-func (f *filesystem) fsType(ctx android.ModuleContext) fsType {
-	typeStr := proptools.StringDefault(f.properties.Type, "ext4")
+func GetFsTypeFromString(ctx android.EarlyModuleContext, typeStr string) fsType {
 	switch typeStr {
 	case "ext4":
 		return ext4Type
@@ -217,11 +220,19 @@
 	case "cpio":
 		return cpioType
 	default:
-		ctx.PropertyErrorf("type", "%q not supported", typeStr)
 		return unknown
 	}
 }
 
+func (f *filesystem) fsType(ctx android.ModuleContext) fsType {
+	typeStr := proptools.StringDefault(f.properties.Type, "ext4")
+	fsType := GetFsTypeFromString(ctx, typeStr)
+	if fsType == unknown {
+		ctx.PropertyErrorf("type", "%q not supported", typeStr)
+	}
+	return fsType
+}
+
 func (f *filesystem) installFileName() string {
 	return f.BaseModuleName() + ".img"
 }
diff --git a/fsgen/filesystem_creator.go b/fsgen/filesystem_creator.go
index ed0c390..d5e0c58 100644
--- a/fsgen/filesystem_creator.go
+++ b/fsgen/filesystem_creator.go
@@ -114,7 +114,11 @@
 }
 
 func (f *filesystemCreator) createInternalModules(ctx android.LoadHookContext) {
-	for _, partitionType := range []string{"system"} {
+	partitionTypes := []string{"system"}
+	if ctx.DeviceConfig().SystemExtPath() == "system_ext" { // system_ext exists
+		partitionTypes = append(partitionTypes, "system_ext")
+	}
+	for _, partitionType := range partitionTypes {
 		if f.createPartition(ctx, partitionType) {
 			f.properties.Generated_partition_types = append(f.properties.Generated_partition_types, partitionType)
 		} else {
@@ -143,15 +147,23 @@
 		Name: proptools.StringPtr(f.generatedModuleName(ctx.Config(), "device")),
 	}
 
-	// Currently, only the system partition module is created.
+	// Currently, only the system and system_ext partition module is created.
 	partitionProps := &filesystem.PartitionNameProperties{}
 	if android.InList("system", f.properties.Generated_partition_types) {
 		partitionProps.System_partition_name = proptools.StringPtr(f.generatedModuleNameForPartition(ctx.Config(), "system"))
 	}
+	if android.InList("system_ext", f.properties.Generated_partition_types) {
+		partitionProps.System_ext_partition_name = proptools.StringPtr(f.generatedModuleNameForPartition(ctx.Config(), "system_ext"))
+	}
 
 	ctx.CreateModule(filesystem.AndroidDeviceFactory, baseProps, partitionProps)
 }
 
+var (
+	// https://source.corp.google.com/h/googleplex-android/platform/build/+/639d79f5012a6542ab1f733b0697db45761ab0f3:core/packaging/flags.mk;l=21;drc=5ba8a8b77507f93aa48cc61c5ba3f31a4d0cbf37;bpv=1;bpt=0
+	partitionsWithAconfig = []string{"system", "product", "vendor"}
+)
+
 // Creates a soong module to build the given partition. Returns false if we can't support building
 // it.
 func (f *filesystemCreator) createPartition(ctx android.LoadHookContext, partitionType string) bool {
@@ -183,17 +195,19 @@
 
 	fsProps.Partition_name = proptools.StringPtr(partitionType)
 	// BOARD_SYSTEMIMAGE_FILE_SYSTEM_TYPE
-	fsProps.Type = proptools.StringPtr(specificPartitionVars.BoardFileSystemType)
-	if *fsProps.Type != "ext4" {
-		// TODO(b/372522486): Support other FS types.
-		// Currently the android_filesystem module type only supports ext4:
-		// https://cs.android.com/android/platform/superproject/main/+/main:build/soong/filesystem/filesystem.go;l=416;drc=98047cfd07944b297a12d173453bc984806760d2
+	fsType := specificPartitionVars.BoardFileSystemType
+	if fsType == "" {
+		fsType = "ext4" //default
+	}
+	fsProps.Type = proptools.StringPtr(fsType)
+	if filesystem.GetFsTypeFromString(ctx, *fsProps.Type).IsUnknown() {
+		// Currently the android_filesystem module type only supports a handful of FS types like ext4, erofs
 		return false
 	}
 
 	fsProps.Base_dir = proptools.StringPtr(partitionType)
 
-	fsProps.Gen_aconfig_flags_pb = proptools.BoolPtr(true)
+	fsProps.Gen_aconfig_flags_pb = proptools.BoolPtr(android.InList(partitionType, partitionsWithAconfig))
 
 	// Identical to that of the generic_system_image
 	fsProps.Fsverity.Inputs = []string{
@@ -222,6 +236,8 @@
 	if partitionType == "system" {
 		module = ctx.CreateModule(filesystem.SystemImageFactory, baseProps, fsProps)
 	} else {
+		// Explicitly set the partition.
+		fsProps.Partition_type = proptools.StringPtr(partitionType)
 		module = ctx.CreateModule(filesystem.FilesystemFactory, baseProps, fsProps)
 	}
 	module.HideFromMake()
diff --git a/java/app_import.go b/java/app_import.go
index a54cf2f..f5d9f3e 100644
--- a/java/app_import.go
+++ b/java/app_import.go
@@ -61,6 +61,9 @@
 func RegisterAppImportBuildComponents(ctx android.RegistrationContext) {
 	ctx.RegisterModuleType("android_app_import", AndroidAppImportFactory)
 	ctx.RegisterModuleType("android_test_import", AndroidTestImportFactory)
+	ctx.PreArchMutators(func(ctx android.RegisterMutatorsContext) {
+		ctx.BottomUp("disable_prebuilts_without_apk", disablePrebuiltsWithoutApkMutator)
+	})
 }
 
 type AndroidAppImport struct {
@@ -90,7 +93,7 @@
 
 type AndroidAppImportProperties struct {
 	// A prebuilt apk to import
-	Apk *string `android:"path"`
+	Apk proptools.Configurable[string] `android:"path,replace_instead_of_append"`
 
 	// The name of a certificate in the default certificate directory or an android_app_certificate
 	// module name in the form ":module". Should be empty if presigned or default_dev_cert is set.
@@ -193,13 +196,6 @@
 			}
 		}
 	}
-
-	if String(a.properties.Apk) == "" {
-		// Disable this module since the apk property is still empty after processing all matching
-		// variants. This likely means there is no matching variant, and the default variant doesn't
-		// have an apk property value either.
-		a.Disable()
-	}
 }
 
 func MergePropertiesFromVariant(ctx android.EarlyModuleContext,
@@ -219,6 +215,30 @@
 	}
 }
 
+// disablePrebuiltsWithoutApkMutator is a pre-arch mutator that disables AndroidAppImport or
+// AndroidTestImport modules that don't have an apk set. We need this separate mutator instead
+// of doing it in processVariants because processVariants is a defaultable hook, and configurable
+// properties can only be evaluated after the defaults (and eventually, base configurabtion)
+// mutators.
+func disablePrebuiltsWithoutApkMutator(ctx android.BottomUpMutatorContext) {
+	switch a := ctx.Module().(type) {
+	case *AndroidAppImport:
+		if a.properties.Apk.GetOrDefault(ctx, "") == "" {
+			// Disable this module since the apk property is still empty after processing all
+			// matching variants. This likely means there is no matching variant, and the default
+			// variant doesn't have an apk property value either.
+			a.Disable()
+		}
+	case *AndroidTestImport:
+		if a.properties.Apk.GetOrDefault(ctx, "") == "" {
+			// Disable this module since the apk property is still empty after processing all
+			// matching variants. This likely means there is no matching variant, and the default
+			// variant doesn't have an apk property value either.
+			a.Disable()
+		}
+	}
+}
+
 func (a *AndroidAppImport) DepsMutator(ctx android.BottomUpMutatorContext) {
 	cert := android.SrcIsModule(String(a.properties.Certificate))
 	if cert != "" {
@@ -409,7 +429,7 @@
 
 	if apexInfo.IsForPlatform() {
 		a.installPath = ctx.InstallFile(installDir, apkFilename, a.outputFile)
-		artifactPath := android.PathForModuleSrc(ctx, *a.properties.Apk)
+		artifactPath := android.PathForModuleSrc(ctx, a.properties.Apk.GetOrDefault(ctx, ""))
 		a.provenanceMetaDataFile = provenance.GenerateArtifactProvenanceMetaData(ctx, artifactPath, a.installPath)
 	}
 
@@ -633,7 +653,7 @@
 	android.InitApexModule(module)
 	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
 	android.InitDefaultableModule(module)
-	android.InitSingleSourcePrebuiltModule(module, &module.properties, "Apk")
+	android.InitConfigurablePrebuiltModuleString(module, &module.properties.Apk, "Apk")
 
 	module.usesLibrary.enforce = true
 
@@ -686,7 +706,7 @@
 	android.InitApexModule(module)
 	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
 	android.InitDefaultableModule(module)
-	android.InitSingleSourcePrebuiltModule(module, &module.properties, "Apk")
+	android.InitConfigurablePrebuiltModuleString(module, &module.properties.Apk, "Apk")
 
 	return module
 }
diff --git a/ui/build/androidmk_denylist.go b/ui/build/androidmk_denylist.go
index 2ec8972..a8044df 100644
--- a/ui/build/androidmk_denylist.go
+++ b/ui/build/androidmk_denylist.go
@@ -16,6 +16,8 @@
 
 import (
 	"strings"
+
+	"android/soong/android"
 )
 
 var androidmk_denylist []string = []string{
@@ -64,3 +66,29 @@
 		}
 	}
 }
+
+// The Android.mk files in these directories are for NDK build system.
+var external_ndk_androidmks []string = []string{
+	"external/fmtlib/",
+	"external/google-breakpad/",
+	"external/googletest/",
+	"external/libaom/",
+	"external/libusb/",
+	"external/libvpx/",
+	"external/libwebm/",
+	"external/libwebsockets/",
+	"external/vulkan-validation-layers/",
+	"external/walt/",
+	"external/webp/",
+}
+
+func ignoreNdkAndroidMks(androidMks []string) []string {
+	return android.FilterListPred(androidMks, func(s string) bool {
+		for _, d := range external_ndk_androidmks {
+			if strings.HasPrefix(s, d) {
+				return false
+			}
+		}
+		return true
+	})
+}
diff --git a/ui/build/finder.go b/ui/build/finder.go
index 573df21..a899822 100644
--- a/ui/build/finder.go
+++ b/ui/build/finder.go
@@ -128,6 +128,7 @@
 
 	// Stop searching a subdirectory recursively after finding an Android.mk.
 	androidMks := f.FindFirstNamedAt(".", "Android.mk")
+	androidMks = ignoreNdkAndroidMks(androidMks)
 	blockAndroidMks(ctx, androidMks)
 	err := dumpListToFile(ctx, config, androidMks, filepath.Join(dumpDir, "Android.mk.list"))
 	if err != nil {