diff --git a/Android.bp b/Android.bp
index 63c8fb6..5efcb77 100644
--- a/Android.bp
+++ b/Android.bp
@@ -561,6 +561,12 @@
     ],
 }
 
+java_library {
+    name: "framework-annotations-lib",
+    srcs: [ ":framework-annotations" ],
+    sdk_version: "current",
+}
+
 filegroup {
     name: "framework-networkstack-shared-srcs",
     srcs: [
diff --git a/apex/sdkext/Android.bp b/apex/sdkext/Android.bp
index 60d657d..b8dcb90 100644
--- a/apex/sdkext/Android.bp
+++ b/apex/sdkext/Android.bp
@@ -15,6 +15,7 @@
 apex {
     name: "com.android.sdkext",
     manifest: "manifest.json",
+    java_libs: [ "framework-sdkext" ],
     key: "com.android.sdkext.key",
     certificate: ":com.android.sdkext.certificate",
 }
diff --git a/apex/sdkext/framework/Android.bp b/apex/sdkext/framework/Android.bp
index bc7857fe..b17f0f8 100644
--- a/apex/sdkext/framework/Android.bp
+++ b/apex/sdkext/framework/Android.bp
@@ -19,3 +19,12 @@
     ],
     path: "java",
 }
+
+java_library {
+    name: "framework-sdkext",
+    srcs: [ ":framework-sdkext-sources" ],
+    sdk_version: "system_current",
+    libs: [ "framework-annotations-lib" ],
+    permitted_packages: [ "android.os.ext" ],
+    installable: true,
+}
diff --git a/apex/sdkext/framework/java/android/os/ext/SdkExtensions.java b/apex/sdkext/framework/java/android/os/ext/SdkExtensions.java
new file mode 100644
index 0000000..c039a82
--- /dev/null
+++ b/apex/sdkext/framework/java/android/os/ext/SdkExtensions.java
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.os.ext;
+
+import android.annotation.IntDef;
+import android.os.Build.VERSION_CODES;
+import android.os.SystemProperties;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/** @hide */
+public class SdkExtensions {
+
+    private static final int R_EXTENSION_INT;
+    static {
+        R_EXTENSION_INT = SystemProperties.getInt("persist.com.android.sdkext.sdk_info", 0);
+    }
+
+    /** Values suitable as parameters for {@link #getExtensionVersion(int)}. */
+    @IntDef(value = { VERSION_CODES.R })
+    @Retention(RetentionPolicy.SOURCE)
+    public @interface SdkVersion {}
+
+    /**
+     * Return the version of the extension to the given SDK.
+     *
+     * @param sdk the SDK version to get the extension version of.
+     * @see SdkVersion
+     * @throws IllegalArgumentException if sdk is not an sdk version with extensions
+     */
+    public static int getExtensionVersion(@SdkVersion int sdk) {
+        if (sdk < VERSION_CODES.R) {
+            throw new IllegalArgumentException();
+        }
+        return R_EXTENSION_INT;
+    }
+
+}
diff --git a/apex/sdkext/framework/java/android/os/ext/package.html b/apex/sdkext/framework/java/android/os/ext/package.html
new file mode 100644
index 0000000..34c1697
--- /dev/null
+++ b/apex/sdkext/framework/java/android/os/ext/package.html
@@ -0,0 +1,5 @@
+<HTML>
+<BODY>
+Provides APIs to interface with the SDK extensions.
+</BODY>
+</HTML>
diff --git a/apex/sdkext/framework/tests/Android.bp b/apex/sdkext/framework/tests/Android.bp
new file mode 100644
index 0000000..3d5dbb3
--- /dev/null
+++ b/apex/sdkext/framework/tests/Android.bp
@@ -0,0 +1,10 @@
+android_test {
+    name: "framework-sdkext-tests",
+    srcs: ["src/**/*.java"],
+    libs: [
+        "android.test.base",
+        "android.test.runner",
+    ],
+    static_libs: [ "framework-sdkext" ],
+    platform_apis: true,
+}
diff --git a/apex/sdkext/framework/tests/AndroidManifest.xml b/apex/sdkext/framework/tests/AndroidManifest.xml
new file mode 100644
index 0000000..831f132
--- /dev/null
+++ b/apex/sdkext/framework/tests/AndroidManifest.xml
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2019 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+          package="com.android.sdkext.tests">
+
+    <application>
+        <uses-library android:name="android.test.runner" />
+    </application>
+
+    <instrumentation android:name="android.test.InstrumentationTestRunner"
+            android:targetPackage="com.android.sdkext.tests" />
+
+</manifest>
diff --git a/apex/sdkext/framework/tests/src/android/os/ext/SdkExtensionsTest.java b/apex/sdkext/framework/tests/src/android/os/ext/SdkExtensionsTest.java
new file mode 100644
index 0000000..6885110
--- /dev/null
+++ b/apex/sdkext/framework/tests/src/android/os/ext/SdkExtensionsTest.java
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.os.ext;
+
+import android.os.Build;
+import android.test.suitebuilder.annotation.SmallTest;
+
+import junit.framework.TestCase;
+
+public class SdkExtensionsTest extends TestCase {
+
+    @SmallTest
+    public void testBadArgument() throws Exception {
+        try {
+            SdkExtensions.getExtensionVersion(Build.VERSION_CODES.Q);
+            fail("expected IllegalArgumentException");
+        } catch (IllegalArgumentException expected) { }
+
+        try {
+            SdkExtensions.getExtensionVersion(999999);
+            fail("expected IllegalArgumentException");
+        } catch (IllegalArgumentException expected) { }
+    }
+
+    @SmallTest
+    public void testDefault() throws Exception {
+        int r = SdkExtensions.getExtensionVersion(Build.VERSION_CODES.R);
+        assertTrue(r >= 0);
+    }
+
+}