diff --git a/Gemfile b/Gemfile
index 95718d67aef4c..6a1bba85ef8b3 100644
--- a/Gemfile
+++ b/Gemfile
@@ -20,7 +20,7 @@ gem 'turbolinks'
 gem 'arel', github: 'rails/arel', branch: 'master'
 gem 'mail', github: 'mikel/mail'
 
-gem 'sprockets', '~> 3.0.0.rc.1'
+gem 'sprockets', github: 'rails/sprockets', branch: 'master'
 gem 'sprockets-rails', github: 'rails/sprockets-rails', branch: 'master'
 
 # require: false so bcrypt is loaded only when has_secure_password is used.
@@ -31,6 +31,7 @@ gem 'bcrypt', '~> 3.1.10', require: false
 # This needs to be with require false to avoid
 # it being automatically loaded by sprockets
 gem 'uglifier', '>= 1.3.0', require: false
+gem 'sass', '>= 3.3', require: false
 
 group :doc do
   gem 'sdoc', '~> 0.4.0'
diff --git a/Gemfile.lock b/Gemfile.lock
index 52e221c6fc5d9..dc355dda3e1bf 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -59,6 +59,14 @@ GIT
       activesupport (>= 4.0)
       sprockets (>= 3.0.0)
 
+GIT
+  remote: git://github.com/rails/sprockets.git
+  revision: de057b4f13deb2bb5e8684cd06b9b687f5d09792
+  branch: master
+  specs:
+    sprockets (4.0.0)
+      rack (~> 1.0)
+
 PATH
   remote: .
   specs:
@@ -215,6 +223,7 @@ GEM
       resque (~> 1.25)
       rufus-scheduler (~> 3.0)
     rufus-scheduler (3.1.3)
+    sass (3.4.16)
     sdoc (0.4.1)
       json (~> 1.7, >= 1.7.7)
       rdoc (~> 4.0)
@@ -237,8 +246,6 @@ GEM
       serverengine (~> 1.5.5)
       thor
       thread (~> 0.1.7)
-    sprockets (3.0.3)
-      rack (~> 1.0)
     sqlite3 (1.3.10)
     stackprof (0.2.7)
     sucker_punch (1.5.0)
@@ -303,11 +310,12 @@ DEPENDENCIES
   redcarpet (~> 3.2.3)
   resque
   resque-scheduler
+  sass (>= 3.3)
   sdoc (~> 0.4.0)
   sequel
   sidekiq
   sneakers
-  sprockets (~> 3.0.0.rc.1)
+  sprockets!
   sprockets-rails!
   sqlite3 (~> 1.3.6)
   stackprof
diff --git a/railties/lib/rails/generators/app_base.rb b/railties/lib/rails/generators/app_base.rb
index 249fe96772e40..a5fdfdcf2fe53 100644
--- a/railties/lib/rails/generators/app_base.rb
+++ b/railties/lib/rails/generators/app_base.rb
@@ -209,12 +209,16 @@ def rails_gemfile_entry
           [
             GemfileEntry.path('rails', Rails::Generators::RAILS_DEV_PATH),
             GemfileEntry.github('sprockets-rails', 'rails/sprockets-rails'),
+            GemfileEntry.github('sprockets', 'rails/sprockets'),
+            GemfileEntry.github('sass-rails', 'rails/sass-rails'),
             GemfileEntry.github('arel', 'rails/arel')
           ]
         elsif options.edge?
           [
             GemfileEntry.github('rails', 'rails/rails'),
             GemfileEntry.github('sprockets-rails', 'rails/sprockets-rails'),
+            GemfileEntry.github('sprockets', 'rails/sprockets'),
+            GemfileEntry.github('sass-rails', 'rails/sass-rails'),
             GemfileEntry.github('arel', 'rails/arel')
           ]
         else
@@ -255,8 +259,6 @@ def assets_gemfile_entry
         return [] if options[:skip_sprockets]
 
         gems = []
-        gems << GemfileEntry.version('sass-rails', '~> 5.0',
-                                     'Use SCSS for stylesheets')
 
         gems << GemfileEntry.version('uglifier',
                                    '>= 1.3.0',
diff --git a/railties/lib/rails/generators/rails/app/templates/app/assets/manifest.js b/railties/lib/rails/generators/rails/app/templates/app/assets/manifest.js
new file mode 100644
index 0000000000000..003706715a7fe
--- /dev/null
+++ b/railties/lib/rails/generators/rails/app/templates/app/assets/manifest.js
@@ -0,0 +1,4 @@
+
+//= link_tree ./images
+//= link javascripts/application.js
+//= link stylesheets/application.css
diff --git a/railties/lib/rails/generators/rails/plugin/plugin_generator.rb b/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
index 0e1326ce4fb50..e4ef2063e9fe6 100644
--- a/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
+++ b/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
@@ -104,8 +104,9 @@ def test_dummy_config
     end
 
     def test_dummy_assets
-      template "rails/javascripts.js",  "#{dummy_path}/app/assets/javascripts/application.js", force: true
-      template "rails/stylesheets.css", "#{dummy_path}/app/assets/stylesheets/application.css", force: true
+      template "rails/javascripts.js",    "#{dummy_path}/app/assets/javascripts/application.js", force: true
+      template "rails/stylesheets.css",   "#{dummy_path}/app/assets/stylesheets/application.css", force: true
+      template "rails/dummy_manifest.js", "#{dummy_path}/app/assets/manifest.js", force: true
     end
 
     def test_dummy_clean
@@ -122,6 +123,10 @@ def test_dummy_clean
       end
     end
 
+    def assets_manifest
+      template "rails/engine_manifest.js", "app/assets/#{namespaced_name}_manifest.js"
+    end
+
     def stylesheets
       if mountable?
         copy_file "rails/stylesheets.css",
@@ -220,6 +225,10 @@ def create_lib_files
         build(:lib)
       end
 
+      def create_assets_manifest_file
+        build(:assets_manifest) unless api?
+      end
+
       def create_public_stylesheets_files
         build(:stylesheets) unless api?
       end
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/dummy_manifest.js b/railties/lib/rails/generators/rails/plugin/templates/rails/dummy_manifest.js
new file mode 100644
index 0000000000000..dca57d7c5c26d
--- /dev/null
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/dummy_manifest.js
@@ -0,0 +1,7 @@
+<% unless options.skip_javascript -%>
+// link application.js
+<% end -%>
+//= link application.css
+<% if mountable? -%>
+//= link <%= namespaced_name %>_manifest.js
+<% end -%>
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/engine_manifest.js b/railties/lib/rails/generators/rails/plugin/templates/rails/engine_manifest.js
new file mode 100644
index 0000000000000..a57d9ebcedc19
--- /dev/null
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/engine_manifest.js
@@ -0,0 +1,6 @@
+<% if mountable? -%>
+<% unless options.skip_javascript -%>
+//= link <%= namespaced_name %>/application.js
+<% end -%>
+//= link <%= namespaced_name %>/application.css
+<% end -%>
diff --git a/railties/test/application/asset_debugging_test.rb b/railties/test/application/asset_debugging_test.rb
index 36ab8109a7241..fef65adda2efc 100644
--- a/railties/test/application/asset_debugging_test.rb
+++ b/railties/test/application/asset_debugging_test.rb
@@ -48,7 +48,7 @@ class ::PostsController < ActionController::Base ; end
       assert_no_match(/<script src="\/assets\/xmlhr-([0-z]+)\.js"><\/script>/, last_response.body)
     end
 
-    test "assets aren't concatenated when compile is true is on and debug_assets params is true" do
+    test "assets are served with sourcemaps when compile is true and debug_assets params is true" do
       add_to_env_config "production", "config.assets.compile = true"
 
       ENV["RAILS_ENV"] = "production"
@@ -57,8 +57,7 @@ class ::PostsController < ActionController::Base ; end
       class ::PostsController < ActionController::Base ; end
 
       get '/posts?debug_assets=true'
-      assert_match(/<script src="\/assets\/application(\.self)?-([0-z]+)\.js\?body=1"><\/script>/, last_response.body)
-      assert_match(/<script src="\/assets\/xmlhr(\.self)?-([0-z]+)\.js\?body=1"><\/script>/, last_response.body)
+      assert_match(/<script src="\/assets\/application(\.debug)?-([0-z]+)\.js"><\/script>/, last_response.body)
     end
   end
 end
diff --git a/railties/test/application/assets_test.rb b/railties/test/application/assets_test.rb
index ba2c27d8e8f1e..e4c097557460c 100644
--- a/railties/test/application/assets_test.rb
+++ b/railties/test/application/assets_test.rb
@@ -72,6 +72,7 @@ def assert_no_file_exists(filename)
     end
 
     test "precompile creates the file, gives it the original asset's content and run in production as default" do
+      app_file "app/assets/manifest.js", "//= link_tree ./javascripts"
       app_file "app/assets/javascripts/application.js", "alert();"
       app_file "app/assets/javascripts/foo/application.js", "alert();"
 
@@ -87,6 +88,7 @@ def assert_no_file_exists(filename)
     end
 
     def test_precompile_does_not_hit_the_database
+      app_file "app/assets/manifest.js", "//= link_tree ./javascripts"
       app_file "app/assets/javascripts/application.js", "alert();"
       app_file "app/assets/javascripts/foo/application.js", "alert();"
       app_file "app/controllers/users_controller.rb", <<-eoruby
@@ -178,8 +180,11 @@ class User < ActiveRecord::Base; raise 'should not be reached'; end
     end
 
     test 'precompile use assets defined in app config and reassigned in app env config' do
-      add_to_config 'config.assets.precompile = [ "something.js" ]'
-      add_to_env_config 'production', 'config.assets.precompile += [ "another.js" ]'
+      add_to_config 'config.assets.precompile = [ "something_manifest.js" ]'
+      add_to_env_config 'production', 'config.assets.precompile += [ "another_manifest.js" ]'
+
+      app_file 'app/assets/something_manifest.js', '//= link ./javascripts/something.js'
+      app_file 'app/assets/another_manifest.js', '//= link ./javascripts/another.js'
 
       app_file 'app/assets/javascripts/something.js.erb', 'alert();'
       app_file 'app/assets/javascripts/another.js.erb', 'alert();'
@@ -190,14 +195,14 @@ class User < ActiveRecord::Base; raise 'should not be reached'; end
       assert_file_exists("#{app_path}/public/assets/another-*.js")
     end
 
-    test "asset pipeline should use a Sprockets::Index when config.assets.digest is true" do
+    test "asset pipeline should use a Sprockets::CachedEnvironment when config.assets.digest is true" do
       add_to_config "config.action_controller.perform_caching = false"
       add_to_env_config "production", "config.assets.compile = true"
 
       ENV["RAILS_ENV"] = "production"
       require "#{app_path}/config/environment"
 
-      assert_equal Sprockets::Index, Rails.application.assets.class
+      assert_equal Sprockets::CachedEnvironment, Rails.application.assets.class
     end
 
     test "precompile creates a manifest file with all the assets listed" do
@@ -289,7 +294,8 @@ class User < ActiveRecord::Base; raise 'should not be reached'; end
     test "precompile should handle utf8 filenames" do
       filename = "レイルズ.png"
       app_file "app/assets/images/#{filename}", "not an image really"
-      add_to_config "config.assets.precompile = [ /\.png$/, /application.(css|js)$/ ]"
+      app_file "app/assets/manifest.js", "//= link_tree ./images"
+      add_to_config "config.assets.precompile = %w(manifest.js)"
 
       precompile!
 
@@ -394,7 +400,7 @@ class ::PostsController < ActionController::Base ; end
       app_file "app/assets/javascripts/xmlhr.js.erb", "<%= Post.name %>"
 
       precompile!
-      assert_equal "Post;\n", File.read(Dir["#{app_path}/public/assets/application-*.js"].first)
+      assert_equal "Post\n;\n", File.read(Dir["#{app_path}/public/assets/application-*.js"].first)
     end
 
     test "initialization on the assets group should set assets_dir" do
@@ -439,9 +445,9 @@ class ::PostsController < ActionController::Base ; end
       class ::PostsController < ActionController::Base; end
 
       get '/posts', {}, {'HTTPS'=>'off'}
-      assert_match('src="http://example.com/assets/application.self.js', last_response.body)
+      assert_match('src="http://example.com/assets/application.debug.js', last_response.body)
       get '/posts', {}, {'HTTPS'=>'on'}
-      assert_match('src="https://example.com/assets/application.self.js', last_response.body)
+      assert_match('src="https://example.com/assets/application.debug.js', last_response.body)
     end
 
     test "asset urls should be protocol-relative if no request is in scope" do