diff --git a/src/main/java/com/android/tools/r8/experimental/startup/StartupOptions.java b/src/main/java/com/android/tools/r8/experimental/startup/StartupOptions.java
index 7d1b4dc..afb4691 100644
--- a/src/main/java/com/android/tools/r8/experimental/startup/StartupOptions.java
+++ b/src/main/java/com/android/tools/r8/experimental/startup/StartupOptions.java
@@ -6,8 +6,8 @@
 
 import static com.android.tools.r8.utils.SystemPropertyUtils.parseSystemPropertyForDevelopmentOrDefault;
 
-import com.android.tools.r8.StartupProfileProvider;
 import com.android.tools.r8.StringResource;
+import com.android.tools.r8.startup.StartupProfileProvider;
 import com.android.tools.r8.utils.SystemPropertyUtils;
 import java.nio.file.Paths;
 
diff --git a/src/main/java/com/android/tools/r8/experimental/startup/StartupProfile.java b/src/main/java/com/android/tools/r8/experimental/startup/StartupProfile.java
index 20cd31b..6b6076f 100644
--- a/src/main/java/com/android/tools/r8/experimental/startup/StartupProfile.java
+++ b/src/main/java/com/android/tools/r8/experimental/startup/StartupProfile.java
@@ -4,9 +4,9 @@
 
 package com.android.tools.r8.experimental.startup;
 
-import com.android.tools.r8.StartupProfileProvider;
 import com.android.tools.r8.graph.DexMethod;
 import com.android.tools.r8.graph.DexType;
+import com.android.tools.r8.startup.StartupProfileProvider;
 import com.android.tools.r8.utils.InternalOptions;
 import com.android.tools.r8.utils.StringDiagnostic;
 import com.android.tools.r8.utils.StringUtils;
diff --git a/src/main/java/com/android/tools/r8/startup/StartupClassBuilder.java b/src/main/java/com/android/tools/r8/startup/StartupClassBuilder.java
new file mode 100644
index 0000000..d156ebd
--- /dev/null
+++ b/src/main/java/com/android/tools/r8/startup/StartupClassBuilder.java
@@ -0,0 +1,12 @@
+// Copyright (c) 2022, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.android.tools.r8.startup;
+
+import com.android.tools.r8.references.ClassReference;
+
+public interface StartupClassBuilder {
+
+  StartupClassBuilder setClassReference(ClassReference classReference);
+}
diff --git a/src/main/java/com/android/tools/r8/startup/StartupMethodBuilder.java b/src/main/java/com/android/tools/r8/startup/StartupMethodBuilder.java
new file mode 100644
index 0000000..fe3bb70
--- /dev/null
+++ b/src/main/java/com/android/tools/r8/startup/StartupMethodBuilder.java
@@ -0,0 +1,12 @@
+// Copyright (c) 2022, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.android.tools.r8.startup;
+
+import com.android.tools.r8.references.MethodReference;
+
+public interface StartupMethodBuilder {
+
+  StartupMethodBuilder setMethodReference(MethodReference methodReference);
+}
diff --git a/src/main/java/com/android/tools/r8/startup/StartupProfileBuilder.java b/src/main/java/com/android/tools/r8/startup/StartupProfileBuilder.java
new file mode 100644
index 0000000..9764a06
--- /dev/null
+++ b/src/main/java/com/android/tools/r8/startup/StartupProfileBuilder.java
@@ -0,0 +1,18 @@
+// Copyright (c) 2022, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.android.tools.r8.startup;
+
+import java.util.function.Consumer;
+
+public interface StartupProfileBuilder {
+
+  StartupProfileBuilder addStartupClass(Consumer<StartupClassBuilder> startupClassBuilderConsumer);
+
+  StartupProfileBuilder addStartupMethod(
+      Consumer<StartupMethodBuilder> startupMethodBuilderConsumer);
+
+  StartupProfileBuilder addSyntheticStartupMethod(
+      Consumer<SyntheticStartupMethodBuilder> syntheticStartupMethodBuilderConsumer);
+}
diff --git a/src/main/java/com/android/tools/r8/StartupProfileProvider.java b/src/main/java/com/android/tools/r8/startup/StartupProfileProvider.java
similarity index 91%
rename from src/main/java/com/android/tools/r8/StartupProfileProvider.java
rename to src/main/java/com/android/tools/r8/startup/StartupProfileProvider.java
index fc5e4b1..3c4a036 100644
--- a/src/main/java/com/android/tools/r8/StartupProfileProvider.java
+++ b/src/main/java/com/android/tools/r8/startup/StartupProfileProvider.java
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-package com.android.tools.r8;
+package com.android.tools.r8.startup;
 
 /** Interface for providing a startup profile to the compiler. */
 @FunctionalInterface
diff --git a/src/main/java/com/android/tools/r8/startup/SyntheticStartupMethodBuilder.java b/src/main/java/com/android/tools/r8/startup/SyntheticStartupMethodBuilder.java
new file mode 100644
index 0000000..a1f9c49
--- /dev/null
+++ b/src/main/java/com/android/tools/r8/startup/SyntheticStartupMethodBuilder.java
@@ -0,0 +1,12 @@
+// Copyright (c) 2022, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.android.tools.r8.startup;
+
+import com.android.tools.r8.references.ClassReference;
+
+public interface SyntheticStartupMethodBuilder {
+
+  SyntheticStartupMethodBuilder setSyntheticContextReference(ClassReference classReference);
+}
diff --git a/src/test/java/com/android/tools/r8/classmerging/horizontal/HorizontalClassMergingWithStartupClassesTest.java b/src/test/java/com/android/tools/r8/classmerging/horizontal/HorizontalClassMergingWithStartupClassesTest.java
index 417a097..3288e20 100644
--- a/src/test/java/com/android/tools/r8/classmerging/horizontal/HorizontalClassMergingWithStartupClassesTest.java
+++ b/src/test/java/com/android/tools/r8/classmerging/horizontal/HorizontalClassMergingWithStartupClassesTest.java
@@ -5,12 +5,12 @@
 package com.android.tools.r8.classmerging.horizontal;
 
 import com.android.tools.r8.NeverInline;
-import com.android.tools.r8.StartupProfileProvider;
 import com.android.tools.r8.TestBase;
 import com.android.tools.r8.TestParameters;
 import com.android.tools.r8.experimental.startup.StartupClass;
 import com.android.tools.r8.experimental.startup.StartupProfile;
 import com.android.tools.r8.graph.DexItemFactory;
+import com.android.tools.r8.startup.StartupProfileProvider;
 import com.android.tools.r8.utils.BooleanUtils;
 import com.google.common.collect.ImmutableList;
 import java.util.Collections;
diff --git a/src/test/java/com/android/tools/r8/internal/YouTubeV1719Test.java b/src/test/java/com/android/tools/r8/internal/YouTubeV1719Test.java
index e293b6e..a44f221 100644
--- a/src/test/java/com/android/tools/r8/internal/YouTubeV1719Test.java
+++ b/src/test/java/com/android/tools/r8/internal/YouTubeV1719Test.java
@@ -21,13 +21,13 @@
 import com.android.tools.r8.R8FullTestBuilder;
 import com.android.tools.r8.R8TestCompileResult;
 import com.android.tools.r8.ResourceException;
-import com.android.tools.r8.StartupProfileProvider;
 import com.android.tools.r8.StringConsumer.FileConsumer;
 import com.android.tools.r8.StringResource;
 import com.android.tools.r8.TestCompileResult;
 import com.android.tools.r8.TestParameters;
 import com.android.tools.r8.TestParametersCollection;
 import com.android.tools.r8.ThrowableConsumer;
+import com.android.tools.r8.startup.StartupProfileProvider;
 import com.android.tools.r8.tracereferences.TraceReferences;
 import com.android.tools.r8.tracereferences.TraceReferencesCommand;
 import com.android.tools.r8.tracereferences.TraceReferencesKeepRules;
diff --git a/src/test/java/com/android/tools/r8/internal/startup/ChromeStartupTest.java b/src/test/java/com/android/tools/r8/internal/startup/ChromeStartupTest.java
index 89b37d0..1e65ba1 100644
--- a/src/test/java/com/android/tools/r8/internal/startup/ChromeStartupTest.java
+++ b/src/test/java/com/android/tools/r8/internal/startup/ChromeStartupTest.java
@@ -13,13 +13,13 @@
 import com.android.tools.r8.ArchiveProgramResourceProvider;
 import com.android.tools.r8.DexIndexedConsumer;
 import com.android.tools.r8.R8FullTestBuilder;
-import com.android.tools.r8.StartupProfileProvider;
 import com.android.tools.r8.StringResource;
 import com.android.tools.r8.TestBase;
 import com.android.tools.r8.TestParameters;
 import com.android.tools.r8.TestParametersCollection;
 import com.android.tools.r8.ThrowableConsumer;
 import com.android.tools.r8.ToolHelper;
+import com.android.tools.r8.startup.StartupProfileProvider;
 import com.android.tools.r8.utils.AndroidApiLevel;
 import com.android.tools.r8.utils.ZipUtils;
 import com.android.tools.r8.utils.codeinspector.CodeInspector;
diff --git a/src/test/java/com/android/tools/r8/startup/utils/StartupTestingUtils.java b/src/test/java/com/android/tools/r8/startup/utils/StartupTestingUtils.java
index ec7e59f..ad1af08 100644
--- a/src/test/java/com/android/tools/r8/startup/utils/StartupTestingUtils.java
+++ b/src/test/java/com/android/tools/r8/startup/utils/StartupTestingUtils.java
@@ -10,7 +10,6 @@
 import com.android.tools.r8.CompilationFailedException;
 import com.android.tools.r8.D8TestBuilder;
 import com.android.tools.r8.D8TestRunResult;
-import com.android.tools.r8.StartupProfileProvider;
 import com.android.tools.r8.TestBase;
 import com.android.tools.r8.TestCompilerBuilder;
 import com.android.tools.r8.TestParameters;
@@ -25,6 +24,7 @@
 import com.android.tools.r8.references.ClassReference;
 import com.android.tools.r8.references.MethodReference;
 import com.android.tools.r8.references.TypeReference;
+import com.android.tools.r8.startup.StartupProfileProvider;
 import com.android.tools.r8.utils.AndroidApiLevel;
 import com.android.tools.r8.utils.ClassReferenceUtils;
 import com.android.tools.r8.utils.MethodReferenceUtils;