diff --git a/react-packager/src/Bundler/Bundle.js b/react-packager/src/Bundler/Bundle.js
index 2641550a..9700af08 100644
--- a/react-packager/src/Bundler/Bundle.js
+++ b/react-packager/src/Bundler/Bundle.js
@@ -206,7 +206,7 @@ class Bundle extends BundleBase {
   _getCombinedSourceMaps(options) {
     const result = {
       version: 3,
-      file: 'bundle.js',
+      file: this._getSourceMapFile(),
       sections: [],
     };
 
@@ -246,7 +246,7 @@ class Bundle extends BundleBase {
 
     const mappings = this._getMappings();
     const map = {
-      file: 'bundle.js',
+      file: this._getSourceMapFile(),
       sources: _.pluck(super.getModules(), 'sourcePath'),
       version: 3,
       names: [],
@@ -262,6 +262,12 @@ class Bundle extends BundleBase {
     return eTag;
   }
 
+  _getSourceMapFile() {
+    return this._sourceMapUrl
+      ? this._sourceMapUrl.replace('.map', '.bundle')
+      : 'bundle.js';
+  }
+
   _getMappings() {
     const modules = super.getModules();
 
diff --git a/react-packager/src/Bundler/BundleBase.js b/react-packager/src/Bundler/BundleBase.js
index b9e1cbe3..79cbfefc 100644
--- a/react-packager/src/Bundler/BundleBase.js
+++ b/react-packager/src/Bundler/BundleBase.js
@@ -19,6 +19,10 @@ class BundleBase {
     this._mainModuleId = this._mainModuleName = undefined;
   }
 
+  isEmpty() {
+    return this._modules.length === 0 && this._assets.length === 0;
+  }
+
   getMainModuleId() {
     return this._mainModuleId;
   }
diff --git a/react-packager/src/Bundler/HMRBundle.js b/react-packager/src/Bundler/HMRBundle.js
index fa8c95db..49a21dfd 100644
--- a/react-packager/src/Bundler/HMRBundle.js
+++ b/react-packager/src/Bundler/HMRBundle.js
@@ -8,12 +8,17 @@
  */
 'use strict';
 
+const _ = require('underscore');
 const BundleBase = require('./BundleBase');
 const ModuleTransport = require('../lib/ModuleTransport');
 
 class HMRBundle extends BundleBase {
-  constructor() {
+  constructor({sourceURLFn, sourceMappingURLFn}) {
     super();
+    this._sourceURLFn = sourceURLFn
+    this._sourceMappingURLFn = sourceMappingURLFn;
+    this._sourceURLs = [];
+    this._sourceMappingURLs = [];
   }
 
   addModule(resolver, response, module, transformed) {
@@ -21,14 +26,8 @@ class HMRBundle extends BundleBase {
       module,
       transformed.code,
     ).then(({name, code}) => {
-      code = `
-        __accept(
-          '${name}',
-          function(global, require, module, exports) {
-            ${code}
-          }
-        );
-      `;
+      // need to be in single line so that lines match on sourcemaps
+      code = `__accept(${JSON.stringify(name)}, function(global, require, module, exports) { ${code} });`;
 
       const moduleTransport = new ModuleTransport({
         code,
@@ -40,8 +39,22 @@ class HMRBundle extends BundleBase {
       });
 
       super.addModule(moduleTransport);
+      this._sourceMappingURLs.push(this._sourceMappingURLFn(moduleTransport.sourcePath));
+      this._sourceURLs.push(this._sourceURLFn(moduleTransport.sourcePath));
     });
   }
+
+  getModulesCode() {
+    return this._modules.map(module => module.code);
+  }
+
+  getSourceURLs() {
+    return this._sourceURLs;
+  }
+
+  getSourceMappingURLs() {
+    return this._sourceMappingURLs;
+  }
 }
 
 module.exports = HMRBundle;
diff --git a/react-packager/src/Bundler/__tests__/Bundle-test.js b/react-packager/src/Bundler/__tests__/Bundle-test.js
index 5e5fca22..b4152a7b 100644
--- a/react-packager/src/Bundler/__tests__/Bundle-test.js
+++ b/react-packager/src/Bundler/__tests__/Bundle-test.js
@@ -214,7 +214,7 @@ describe('Bundle', () => {
 
         const sourceMap = otherBundle.getSourceMap({dev: true});
         expect(sourceMap).toEqual({
-          file: 'bundle.js',
+          file: 'test_url',
           version: 3,
           sections: [
             { offset: { line: 0, column: 0 }, map: { name: 'sourcemap foo' } },
@@ -340,7 +340,7 @@ describe('Bundle', () => {
 
 
 function genSourceMap(modules) {
-  var sourceMapGen = new SourceMapGenerator({file: 'bundle.js', version: 3});
+  var sourceMapGen = new SourceMapGenerator({file: 'test_url', version: 3});
   var bundleLineNo = 0;
   for (var i = 0; i < modules.length; i++) {
     var module = modules[i];
diff --git a/react-packager/src/Bundler/index.js b/react-packager/src/Bundler/index.js
index b6ff9133..d2852d44 100644
--- a/react-packager/src/Bundler/index.js
+++ b/react-packager/src/Bundler/index.js
@@ -166,9 +166,58 @@ class Bundler {
     });
   }
 
+  _sourceHMRURL(platform, path) {
+    return this._hmrURL(
+      'http://localhost:8081', // TODO: (martinb) avoid hardcoding
+      platform,
+      'bundle',
+      path,
+    );
+  }
+
+  _sourceMappingHMRURL(platform, path) {
+    // Chrome expects `sourceURL` when eval'ing code
+    return this._hmrURL(
+      '\/\/# sourceURL=',
+      platform,
+      'map',
+      path,
+    );
+  }
+
+  _hmrURL(prefix, platform, extensionOverride, path) {
+    const matchingRoot = this._projectRoots.find(root => path.startsWith(root));
+
+    if (!matchingRoot) {
+      throw new Error('No matching project root for ', path);
+    }
+
+    const extensionStart = path.lastIndexOf('.');
+    let resource = path.substring(
+      matchingRoot.length,
+      extensionStart !== -1 ? extensionStart : undefined,
+    );
+
+    const extension = extensionStart !== -1
+      ? path.substring(extensionStart + 1)
+      : null;
+
+    return (
+      prefix + resource +
+      '.' + extensionOverride + '?' +
+      'platform=' + platform + '&runModule=false&entryModuleOnly=true&hot=true'
+    );
+  }
+
   bundleForHMR(options) {
     return this._bundle({
-      bundle: new HMRBundle(),
+      bundle: new HMRBundle({
+        sourceURLFn: this._sourceHMRURL.bind(this, options.platform),
+        sourceMappingURLFn: this._sourceMappingHMRURL.bind(
+          this,
+          options.platform,
+        ),
+      }),
       hot: true,
       ...options,
     });
@@ -185,6 +234,7 @@ class Bundler {
     platform,
     unbundle: isUnbundle,
     hot: hot,
+    entryModuleOnly,
   }) {
     const findEventId = Activity.startEvent('find dependencies');
     let transformEventId;
@@ -195,18 +245,25 @@ class Bundler {
       bundle.setMainModuleName(response.mainModuleId);
       transformEventId = Activity.startEvent('transform');
 
-      const moduleSystemDeps = includeSystemDependencies
-        ? this._resolver.getModuleSystemDependencies(
-          { dev: isDev, platform, isUnbundle }
-        )
-        : [];
+      let dependencies;
+      if (entryModuleOnly) {
+        dependencies = response.dependencies.filter(module =>
+          module.path.endsWith(entryFile)
+        );
+      } else {
+        const moduleSystemDeps = includeSystemDependencies
+          ? this._resolver.getModuleSystemDependencies(
+            { dev: isDev, platform, isUnbundle }
+          )
+          : [];
 
-      const modulesToProcess = modules || response.dependencies;
-      const dependencies = moduleSystemDeps.concat(modulesToProcess);
+        const modulesToProcess = modules || response.dependencies;
+        const dependencies = moduleSystemDeps.concat(modulesToProcess);
 
-      bundle.setNumPrependedModules && bundle.setNumPrependedModules(
-        response.numPrependedDependencies + moduleSystemDeps.length
-      );
+        bundle.setNumPrependedModules && bundle.setNumPrependedModules(
+          response.numPrependedDependencies + moduleSystemDeps.length
+        );
+      }
 
       let bar;
       if (process.stdout.isTTY) {
diff --git a/react-packager/src/Server/__tests__/Server-test.js b/react-packager/src/Server/__tests__/Server-test.js
index 123134f8..668e162f 100644
--- a/react-packager/src/Server/__tests__/Server-test.js
+++ b/react-packager/src/Server/__tests__/Server-test.js
@@ -144,6 +144,7 @@ describe('processRequest', () => {
         platform: undefined,
         runBeforeMainModule: ['InitializeJavaScriptAppEngine'],
         unbundle: false,
+        entryModuleOnly: false,
       });
     });
   });
@@ -165,6 +166,7 @@ describe('processRequest', () => {
         platform: 'ios',
         runBeforeMainModule: ['InitializeJavaScriptAppEngine'],
         unbundle: false,
+        entryModuleOnly: false,
       });
     });
   });
@@ -321,6 +323,7 @@ describe('processRequest', () => {
           platform: undefined,
           runBeforeMainModule: ['InitializeJavaScriptAppEngine'],
           unbundle: false,
+          entryModuleOnly: false,
         })
       );
     });
@@ -341,6 +344,7 @@ describe('processRequest', () => {
             platform: undefined,
             runBeforeMainModule: ['InitializeJavaScriptAppEngine'],
             unbundle: false,
+            entryModuleOnly: false,
           })
         );
     });
diff --git a/react-packager/src/Server/index.js b/react-packager/src/Server/index.js
index 99a3472d..559fb302 100644
--- a/react-packager/src/Server/index.js
+++ b/react-packager/src/Server/index.js
@@ -118,6 +118,10 @@ const bundleOpts = declareOpts({
     type: 'boolean',
     default: false,
   },
+  entryModuleOnly: {
+    type: 'boolean',
+    default: false,
+  },
 });
 
 const dependencyOpts = declareOpts({
@@ -527,6 +531,11 @@ class Server {
         false
       ),
       platform: platform,
+      entryModuleOnly: this._getBoolOptionFromQuery(
+        urlObj.query,
+        'entryModuleOnly',
+        false,
+      ),
     };
   }