diff --git a/java/prebuilt_apis.go b/java/prebuilt_apis.go
index f7841b53d..44650a6d0 100644
--- a/java/prebuilt_apis.go
+++ b/java/prebuilt_apis.go
@@ -38,6 +38,11 @@ type prebuiltApisProperties struct {
 	// list of api version directories
 	Api_dirs []string
 
+	// Directory containing finalized api txt files for extension versions.
+	// Extension versions higher than the base sdk extension version will
+	// be assumed to be finalized later than all Api_dirs.
+	Extensions_dir *string
+
 	// The next API directory can optionally point to a directory where
 	// files incompatibility-tracking files are stored for the current
 	// "in progress" API. Each module present in one of the api_dirs will have
@@ -152,6 +157,13 @@ func globApiDirs(mctx android.LoadHookContext, p *prebuiltApis, api_dir_glob str
 	return files
 }
 
+// globExtensionDirs collects all the files under the extension dir (for all versions and scopes) that match the given glob
+// <extension-dir>/<version>/<scope>/<glob> for all version and scope.
+func globExtensionDirs(mctx android.LoadHookContext, p *prebuiltApis, extension_dir_glob string) []string {
+	// <extensions-dir>/<num>/<extension-dir-glob>
+	return globScopeDir(mctx, *p.properties.Extensions_dir+"/*", extension_dir_glob)
+}
+
 // globScopeDir collects all the files in the given subdir across all scopes that match the given glob, e.g. '*.jar' or 'api/*.txt'.
 // <subdir>/<scope>/<glob> for all scope.
 func globScopeDir(mctx android.LoadHookContext, subdir string, subdir_glob string) []string {
@@ -222,17 +234,32 @@ func prebuiltApiFiles(mctx android.LoadHookContext, p *prebuiltApis) {
 		version             int
 	}
 
-	latest := make(map[string]latestApiInfo)
-	for _, f := range apiLevelFiles {
-		module, version, scope := parseFinalizedPrebuiltPath(mctx, f)
-		if strings.HasSuffix(module, "incompatibilities") {
-			continue
+	getLatest := func(files []string) map[string]latestApiInfo {
+		m := make(map[string]latestApiInfo)
+		for _, f := range files {
+			module, version, scope := parseFinalizedPrebuiltPath(mctx, f)
+			if strings.HasSuffix(module, "incompatibilities") {
+				continue
+			}
+			key := module + "." + scope
+			info, exists := m[key]
+			if !exists || version > info.version {
+				m[key] = latestApiInfo{module, scope, f, version}
+			}
 		}
+		return m
+	}
 
-		key := module + "." + scope
-		info, exists := latest[key]
-		if !exists || version > info.version {
-			latest[key] = latestApiInfo{module, scope, f, version}
+	latest := getLatest(apiLevelFiles)
+	if p.properties.Extensions_dir != nil {
+		extensionApiFiles := globExtensionDirs(mctx, p, "api/*.txt")
+		for k, v := range getLatest(extensionApiFiles) {
+			if v.version > mctx.Config().PlatformBaseSdkExtensionVersion() {
+				if _, exists := latest[k]; !exists {
+					mctx.ModuleErrorf("Module %v finalized for extension %d but never during an API level; likely error", v.module, v.version)
+				}
+				latest[k] = v
+			}
 		}
 	}
 
diff --git a/java/prebuilt_apis_test.go b/java/prebuilt_apis_test.go
index 79f42250b..75422ad45 100644
--- a/java/prebuilt_apis_test.go
+++ b/java/prebuilt_apis_test.go
@@ -20,9 +20,14 @@ import (
 	"testing"
 
 	"android/soong/android"
+
 	"github.com/google/blueprint"
 )
 
+func intPtr(v int) *int {
+	return &v
+}
+
 func TestPrebuiltApis_SystemModulesCreation(t *testing.T) {
 	result := android.GroupFixturePreparers(
 		prepareForJavaTest,
@@ -54,3 +59,34 @@ func TestPrebuiltApis_SystemModulesCreation(t *testing.T) {
 	sort.Strings(expected)
 	android.AssertArrayString(t, "sdk system modules", expected, sdkSystemModules)
 }
+
+func TestPrebuiltApis_WithExtensions(t *testing.T) {
+	runTestWithBaseExtensionLevel := func(v int) (foo_input string, bar_input string) {
+		result := android.GroupFixturePreparers(
+			prepareForJavaTest,
+			android.FixtureModifyProductVariables(func(variables android.FixtureProductVariables) {
+				variables.Platform_base_sdk_extension_version = intPtr(v)
+			}),
+			FixtureWithPrebuiltApisAndExtensions(map[string][]string{
+				"31":      {"foo"},
+				"32":      {"foo", "bar"},
+				"current": {"foo", "bar"},
+			}, map[string][]string{
+				"1": {"foo"},
+				"2": {"foo", "bar"},
+			}),
+		).RunTest(t)
+		foo_input = result.ModuleForTests("foo.api.public.latest", "").Rule("generator").Implicits[0].String()
+		bar_input = result.ModuleForTests("bar.api.public.latest", "").Rule("generator").Implicits[0].String()
+		return
+	}
+	// Here, the base extension level is 1, so extension level 2 is the latest
+	foo_input, bar_input := runTestWithBaseExtensionLevel(1)
+	android.AssertStringEquals(t, "Expected latest = extension level 2", "prebuilts/sdk/extensions/2/public/api/foo.txt", foo_input)
+	android.AssertStringEquals(t, "Expected latest = extension level 2", "prebuilts/sdk/extensions/2/public/api/bar.txt", bar_input)
+
+	// Here, the base extension level is 2, so 2 is not later than 32.
+	foo_input, bar_input = runTestWithBaseExtensionLevel(2)
+	android.AssertStringEquals(t, "Expected latest = api level 32", "prebuilts/sdk/32/public/api/foo.txt", foo_input)
+	android.AssertStringEquals(t, "Expected latest = api level 32", "prebuilts/sdk/32/public/api/bar.txt", bar_input)
+}
diff --git a/java/testing.go b/java/testing.go
index 6c49bc866..82aa29b61 100644
--- a/java/testing.go
+++ b/java/testing.go
@@ -146,6 +146,10 @@ var PrepareForTestWithPrebuiltsOfCurrentApi = FixtureWithPrebuiltApis(map[string
 // This defines a file in the mock file system in a predefined location (prebuilts/sdk/Android.bp)
 // and so only one instance of this can be used in each fixture.
 func FixtureWithPrebuiltApis(release2Modules map[string][]string) android.FixturePreparer {
+	return FixtureWithPrebuiltApisAndExtensions(release2Modules, nil)
+}
+
+func FixtureWithPrebuiltApisAndExtensions(apiLevel2Modules map[string][]string, extensionLevel2Modules map[string][]string) android.FixturePreparer {
 	mockFS := android.MockFS{}
 	path := "prebuilts/sdk/Android.bp"
 
@@ -153,14 +157,20 @@ func FixtureWithPrebuiltApis(release2Modules map[string][]string) android.Fixtur
 			prebuilt_apis {
 				name: "sdk",
 				api_dirs: ["%s"],
+				extensions_dir: "extensions",
 				imports_sdk_version: "none",
 				imports_compile_dex: true,
 			}
-		`, strings.Join(android.SortedStringKeys(release2Modules), `", "`))
+		`, strings.Join(android.SortedStringKeys(apiLevel2Modules), `", "`))
 
-	for release, modules := range release2Modules {
+	for release, modules := range apiLevel2Modules {
 		mockFS.Merge(prebuiltApisFilesForModules([]string{release}, modules))
 	}
+	if extensionLevel2Modules != nil {
+		for release, modules := range extensionLevel2Modules {
+			mockFS.Merge(prebuiltExtensionApiFiles([]string{release}, modules))
+		}
+	}
 	return android.GroupFixturePreparers(
 		android.FixtureAddTextFile(path, bp),
 		android.FixtureMergeMockFs(mockFS),
@@ -198,6 +208,19 @@ func prebuiltApisFilesForModules(apiLevels []string, modules []string) map[strin
 	return fs
 }
 
+func prebuiltExtensionApiFiles(extensionLevels []string, modules []string) map[string][]byte {
+	fs := make(map[string][]byte)
+	for _, level := range extensionLevels {
+		for _, sdkKind := range []android.SdkKind{android.SdkPublic, android.SdkSystem, android.SdkModule, android.SdkSystemServer} {
+			for _, lib := range modules {
+				fs[fmt.Sprintf("prebuilts/sdk/extensions/%s/%s/api/%s.txt", level, sdkKind, lib)] = nil
+				fs[fmt.Sprintf("prebuilts/sdk/extensions/%s/%s/api/%s-removed.txt", level, sdkKind, lib)] = nil
+			}
+		}
+	}
+	return fs
+}
+
 // FixtureConfigureBootJars configures the boot jars in both the dexpreopt.GlobalConfig and
 // Config.productVariables structs. As a side effect that enables dexpreopt.
 func FixtureConfigureBootJars(bootJars ...string) android.FixturePreparer {
diff --git a/scripts/build-ndk-prebuilts.sh b/scripts/build-ndk-prebuilts.sh
index 4783037b2..15745873c 100755
--- a/scripts/build-ndk-prebuilts.sh
+++ b/scripts/build-ndk-prebuilts.sh
@@ -23,6 +23,7 @@ TOP=$(pwd)
 
 source build/envsetup.sh
 PLATFORM_SDK_VERSION=$(get_build_var PLATFORM_SDK_VERSION)
+PLATFORM_BASE_SDK_EXTENSION_VERSION=$(get_build_var PLATFORM_BASE_SDK_EXTENSION_VERSION)
 PLATFORM_VERSION_ALL_CODENAMES=$(get_build_var PLATFORM_VERSION_ALL_CODENAMES)
 
 # PLATFORM_VERSION_ALL_CODENAMES is a comma separated list like O,P. We need to
@@ -46,6 +47,7 @@ mkdir -p ${SOONG_OUT}
 cat > ${SOONG_OUT}/soong.variables << EOF
 {
     "Platform_sdk_version": ${PLATFORM_SDK_VERSION},
+    "Platform_base_sdk_extension_version": ${PLATFORM_BASE_SDK_EXTENSION_VERSION},
     "Platform_version_active_codenames": ${PLATFORM_VERSION_ALL_CODENAMES},
 
     "DeviceName": "generic_arm64",