diff --git a/react-packager/src/ModuleGraph/ModuleGraph.js b/react-packager/src/ModuleGraph/ModuleGraph.js
new file mode 100644
index 00000000..bd559940
--- /dev/null
+++ b/react-packager/src/ModuleGraph/ModuleGraph.js
@@ -0,0 +1,102 @@
+/**
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @flow
+ */
+'use strict';
+
+const defaults = require('../../../defaults');
+const nullthrows = require('fbjs/lib/nullthrows');
+const parallel = require('async/parallel');
+const seq = require('async/seq');
+
+const {virtualModule} = require('./output/util');
+
+import type {
+  Callback,
+  GraphFn,
+  GraphResult,
+  Module,
+} from './types.flow';
+
+type BuildFn = (
+  entryPoints: Iterable<string>,
+  options: BuildOptions,
+  callback: Callback<{modules: Iterable<Module>, entryModules: Iterable<Module>}>,
+) => void;
+
+type BuildOptions = {|
+  optimize?: boolean,
+  platform?: string,
+|};
+
+exports.createBuildSetup = (
+  graph: GraphFn,
+  translateDefaultsPath: string => string = x => x,
+): BuildFn =>
+  (entryPoints, options, callback) => {
+    const {
+      optimize = false,
+      platform = defaults.platforms[0],
+    } = options;
+    const graphOptions = {optimize};
+
+    const graphWithOptions =
+      (entry, cb) => graph(entry, platform, graphOptions, cb);
+    const graphOnlyModules = seq(graphWithOptions, getModules);
+
+    parallel({
+      graph: cb => graphWithOptions(
+        concat(defaults.runBeforeMainModule, entryPoints),
+        cb,
+      ),
+      moduleSystem: cb => graphOnlyModules(
+        [translateDefaultsPath(defaults.moduleSystem)],
+        cb,
+      ),
+      polyfills: cb => graphOnlyModules(
+        defaults.polyfills.map(translateDefaultsPath),
+        cb,
+      ),
+    }, (
+      error: ?Error,
+      result?: {graph: GraphResult, moduleSystem: Array<Module>, polyfills: Array<Module>},
+    ) => {
+      if (error) {
+        callback(error);
+        return;
+      }
+
+
+      const {
+        graph: {modules, entryModules},
+        moduleSystem,
+        polyfills,
+      } = nullthrows(result);
+
+      callback(null, {
+        entryModules,
+        modules: concat([prelude(optimize)], moduleSystem, polyfills, modules),
+      });
+    });
+  };
+
+const getModules = (x, cb) => cb(null, x.modules);
+
+function* concat<T>(...iterables: Array<Iterable<T>>): Iterable<T> {
+  for (const it of iterables) {
+    yield* it;
+  }
+}
+
+function prelude(optimize) {
+  return virtualModule(
+    `var __DEV__= ${String(!optimize)
+    }, __BUNDLE_START_TIME__ = Date.now();`
+  );
+}
diff --git a/react-packager/src/ModuleGraph/output/as-plain-bundle.js b/react-packager/src/ModuleGraph/output/as-plain-bundle.js
index e0bf8a2c..2cf40dde 100644
--- a/react-packager/src/ModuleGraph/output/as-plain-bundle.js
+++ b/react-packager/src/ModuleGraph/output/as-plain-bundle.js
@@ -13,36 +13,32 @@
 const {createIndexMap} = require('./source-map');
 const {addModuleIdsToModuleWrapper} = require('./util');
 
-import type {Module} from '../types.flow';
-import type {SourceMap} from './source-map';
+import type {OutputFn} from '../types.flow';
 
 module.exports = (
-  modules: Iterable<Module>,
-  filename?: string,
-  idForPath: {path: string} => number,
-): {code: string, map: SourceMap} => {
-  let code = '';
-  let line = 0;
-  const sections = [];
+  (modules, filename, idForPath) => {
+    let code = '';
+    let line = 0;
+    const sections = [];
 
-  for (const module of modules) {
-    const {file} = module;
-    const moduleCode = file.type === 'module'
-      ? addModuleIdsToModuleWrapper(module, idForPath)
-      : file.code;
+    for (const module of modules) {
+      const {file} = module;
+      const moduleCode = file.type === 'module'
+        ? addModuleIdsToModuleWrapper(module, idForPath)
+        : file.code;
 
-    code += moduleCode + '\n';
-    if (file.map) {
-      sections.push({
-        map: file.map,
-        offset: {column: 0, line}
-      });
+      code += moduleCode + '\n';
+      if (file.map) {
+        sections.push({
+          map: file.map,
+          offset: {column: 0, line}
+        });
+      }
+      line += countLines(moduleCode);
     }
-    line += countLines(moduleCode);
-  }
 
-  return {code, map: createIndexMap({file: filename, sections})};
-};
+    return {code, map: createIndexMap({file: filename, sections})};
+  }: OutputFn);
 
 const reLine = /^/gm;
 function countLines(string: string): number {
diff --git a/react-packager/src/ModuleGraph/output/util.js b/react-packager/src/ModuleGraph/output/util.js
index 2f3d8fe0..d233817e 100644
--- a/react-packager/src/ModuleGraph/output/util.js
+++ b/react-packager/src/ModuleGraph/output/util.js
@@ -10,7 +10,7 @@
  */
 'use strict';
 
-import type {Module} from '../types.flow';
+import type {IdForPathFn, Module} from '../types.flow';
 
 // Transformed modules have the form
 //   __d(function(require, module, global, exports, dependencyMap) {
@@ -59,11 +59,27 @@ exports.createIdForPathFn = (): ({path: string} => number) => {
   };
 };
 
-exports.virtualModule = (code: string): Module => ({
-  dependencies: [],
-  file: {
-    code,
-    path: '',
-    type: 'script',
+// creates a series of virtual modules with require calls to the passed-in
+// modules.
+exports.requireCallsTo = function* (
+  modules: Iterable<Module>,
+  idForPath: IdForPathFn,
+): Iterable<Module> {
+  for (const module of modules) {
+    yield virtualModule(`require(${idForPath(module.file)});`);
   }
-});
+};
+
+// creates a virtual module (i.e. not corresponding to a file on disk)
+// with the given source code.
+exports.virtualModule = virtualModule;
+function virtualModule(code: string) {
+  return {
+    dependencies: [],
+    file: {
+      code,
+      path: '',
+      type: 'script',
+    }
+  };
+}
diff --git a/react-packager/src/ModuleGraph/package.json b/react-packager/src/ModuleGraph/package.json
new file mode 100644
index 00000000..4c0d77b8
--- /dev/null
+++ b/react-packager/src/ModuleGraph/package.json
@@ -0,0 +1 @@
+{"main": "ModuleGraph.js"}
diff --git a/react-packager/src/ModuleGraph/types.flow.js b/react-packager/src/ModuleGraph/types.flow.js
index 707bca57..d3910cfd 100644
--- a/react-packager/src/ModuleGraph/types.flow.js
+++ b/react-packager/src/ModuleGraph/types.flow.js
@@ -10,29 +10,13 @@
  */
 'use strict';
 
+import type {SourceMap} from './output/source-map';
 import type {Console} from 'console';
 
 export type Callback<A = void, B = void>
   = (Error => mixed)
   & ((null | void, A, B) => mixed);
 
-type ResolveOptions = {
-  log?: Console,
-};
-
-type LoadOptions = {|
-  log?: Console,
-  optimize?: boolean,
-  platform?: string,
-|};
-
-type GraphOptions = {|
-  cwd?: string,
-  log?: Console,
-  optimize?: boolean,
-  skip?: Set<string>,
-|};
-
 type Dependency = {|
   id: string,
   path: string,
@@ -47,11 +31,6 @@ export type File = {|
 
 type FileTypes = 'module' | 'script';
 
-export type Module = {|
-  dependencies: Array<Dependency>,
-  file: File,
-|};
-
 export type GraphFn = (
   entryPoints: Iterable<string>,
   platform: string,
@@ -59,11 +38,55 @@ export type GraphFn = (
   callback?: Callback<GraphResult>,
 ) => void;
 
+type GraphOptions = {|
+  cwd?: string,
+  log?: Console,
+  optimize?: boolean,
+  skip?: Set<string>,
+|};
+
 export type GraphResult = {
   entryModules: Array<Module>,
   modules: Array<Module>,
 };
 
+export type IdForPathFn = {path: string} => number;
+
+export type LoadFn = (
+  file: string,
+  options: LoadOptions,
+  callback: Callback<File, Array<string>>,
+) => void;
+
+type LoadOptions = {|
+  log?: Console,
+  optimize?: boolean,
+  platform?: string,
+|};
+
+export type Module = {|
+  dependencies: Array<Dependency>,
+  file: File,
+|};
+
+export type OutputFn = (
+  modules: Iterable<Module>,
+  filename?: string,
+  idForPath: IdForPathFn,
+) => OutputResult;
+
+type OutputResult = {
+  code: string,
+  map: SourceMap,
+};
+
+export type PackageData = {|
+  browser?: Object | string,
+  main?: string,
+  name?: string,
+  'react-native'?: Object | string,
+|};
+
 export type ResolveFn = (
   id: string,
   source: string,
@@ -72,12 +95,25 @@ export type ResolveFn = (
   callback: Callback<string>,
 ) => void;
 
-export type LoadFn = (
-  file: string,
-  options: LoadOptions,
-  callback: Callback<File, Array<string>>,
+type ResolveOptions = {
+  log?: Console,
+};
+
+export type TransformFn = (
+  data: {|
+    filename: string,
+    options?: Object,
+    plugins?: Array<string | Object | [string | Object, any]>,
+    sourceCode: string,
+  |},
+  callback: Callback<TransformFnResult>
 ) => void;
 
+
+export type TransformFnResult = {
+  ast: Object,
+};
+
 export type TransformResult = {|
   code: string,
   dependencies: Array<string>,
@@ -93,24 +129,3 @@ export type TransformedFile = {
   transformed: {[variant: string]: TransformResult},
   type: FileTypes,
 };
-
-export type PackageData = {|
-  browser?: Object | string,
-  main?: string,
-  name?: string,
-  'react-native'?: Object | string,
-|};
-
-export type TransformFnResult = {
-  ast: Object,
-};
-
-export type TransformFn = (
-  data: {|
-    filename: string,
-    options?: Object,
-    plugins?: Array<string | Object | [string | Object, any]>,
-    sourceCode: string,
-  |},
-  callback: Callback<TransformFnResult>
-) => void;