diff --git a/CHANGELOG.md b/CHANGELOG.md
index 826135e7..7e4e2f4b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,8 +1,9 @@
 master
 ===
 
-# Next
+# 4.2.0
 
+* Remove Rack support in favor of `resource.filters << proc { |oldbody| newbody }`
 * Expose `development?` and `production?` helpers to template context.
 
 # 4.1.8
diff --git a/middleman-core/features/asset_hash.feature b/middleman-core/features/asset_hash.feature
index 19517e3b..6b92777c 100644
--- a/middleman-core/features/asset_hash.feature
+++ b/middleman-core/features/asset_hash.feature
@@ -188,23 +188,6 @@ Feature: Assets get file hashes appended to them and references to them are upda
     When I go to "/partials/"
     Then I should see 'href="../stylesheets/uses_partials-ec347271.css'
 
-  Scenario: The asset hash should change when a Rack-based filter changes
-    Given a fixture app "asset-hash-app"
-    And a file named "config.rb" with:
-      """
-      activate :asset_hash
-      activate :relative_assets
-      activate :directory_indexes
-      require 'lib/middleware.rb'
-      use ::Middleware
-      """
-    Given the Server is running at "asset-hash-app"
-    When I go to "/"
-    Then I should see 'href="stylesheets/site-5ad7def0.css'
-    When I go to "stylesheets/site-5ad7def0.css"
-    Then I should see 'background-image: url("../images/100px-5fd6fb90.jpg")'
-    Then I should see 'Added by Rack filter'
-
   Scenario: Hashed-asset files are not produced for ignored paths
     Given a fixture app "asset-hash-app"
     And a file named "config.rb" with:
diff --git a/middleman-core/features/endpoints.feature b/middleman-core/features/endpoints.feature
new file mode 100644
index 00000000..1ff6aaf6
--- /dev/null
+++ b/middleman-core/features/endpoints.feature
@@ -0,0 +1,17 @@
+Feature: Generic block based pages
+
+  Scenario: Static Ruby Endpoints
+    Given an empty app
+    And a file named "config.rb" with:
+    """
+    endpoint "hello.html" do
+      "world"
+    end
+    """
+    And a file named "source/index.html.erb" with:
+    """
+    Hi
+    """
+    And the Server is running at "empty_app"
+    When I go to "/hello.html"
+    Then I should see "world"
diff --git a/middleman-core/features/extension_api_deprecations.feature b/middleman-core/features/extension_api_deprecations.feature
index 8c9dd216..15f447ac 100644
--- a/middleman-core/features/extension_api_deprecations.feature
+++ b/middleman-core/features/extension_api_deprecations.feature
@@ -3,8 +3,9 @@ Feature: Extension author could use some hooks
   Scenario: When build
     Given a fixture app "extension-api-deprecations-app"
     When I run `middleman build`
-    Then the exit status should be 0
+    And the exit status should be 0
     And the output should contain "`set :layout` is deprecated"
+    And the output should contain "Project built successfully"
     And the file "build/index.html" should contain "In Index"
     And the file "build/index.html" should not contain "In Layout"
 
diff --git a/middleman-core/features/extension_hooks.feature b/middleman-core/features/extension_hooks.feature
index 1dedd9a9..11a05557 100644
--- a/middleman-core/features/extension_hooks.feature
+++ b/middleman-core/features/extension_hooks.feature
@@ -7,7 +7,6 @@ Feature: Extension author could use some hooks
     And the output should contain "/// after_configuration ///"
     And the output should contain "/// ready ///"
     And the output should contain "/// before_build ///"
-    And the output should contain "/// before ///"
     And the output should contain "/// before_render ///"
     And the output should contain "/// after_render ///"
     And the output should contain "/// after_build ///"
diff --git a/middleman-core/features/mount_rack.feature b/middleman-core/features/mount_rack.feature
deleted file mode 100644
index dcb83146..00000000
--- a/middleman-core/features/mount_rack.feature
+++ /dev/null
@@ -1,65 +0,0 @@
-Feature: Support Rack apps mounted using map
-
-  Scenario: Mounted Rack App at /sinatra
-    Given the Server is running at "sinatra-app"
-    When I go to "/"
-    Then I should see "Hello World (Middleman)"
-    When I go to "/sinatra/"
-    Then I should see "Hello World (Sinatra)"
-
-  Scenario: Built Mounted Rack App at /sinatra
-    Given a successfully built app at "sinatra-app"
-    When I cd to "build"
-    Then the following files should exist:
-      | index.html |
-    Then the following files should not exist:
-      | sinatra/index.html |
-      | sinatra/index2.html |
-
-  Scenario: Static Ruby Endpoints
-    Given a fixture app "sinatra-app"
-    And a file named "config.rb" with:
-    """
-    endpoint "hello.html" do
-      "world"
-    end
-    """
-    And the Server is running at "sinatra-app"
-    When I go to "/hello.html"
-    Then I should see "world"
-
-  Scenario: Built Mounted Rack App at /sinatra (including rack endpoints)
-    Given a fixture app "sinatra-app"
-    And a file named "config.rb" with:
-      """
-      require "sinatra"
-
-      class MySinatra < Sinatra::Base
-        get "/" do
-          "Hello World (Sinatra)"
-        end
-        get "/derp.html" do
-          "De doo"
-        end
-      end
-
-      map "/sinatra" do
-        run MySinatra
-      end
-
-      endpoint "sinatra/index2.html", path: "/sinatra/"
-
-      endpoint "dedoo.html", path: "/sinatra/derp.html"
-
-      endpoint "hello.html" do
-        "world"
-      end
-      """
-    And a successfully built app at "sinatra-app"
-    When I cd to "build"
-    Then the following files should exist:
-      | index.html |
-      | sinatra/index2.html |
-      | dedoo.html |
-    And the file "sinatra/index2.html" should contain 'Hello World (Sinatra)'
-    And the file "dedoo.html" should contain 'De doo'
\ No newline at end of file
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank11.gif b/middleman-core/fixtures/asset-host-app/source/images/blank11.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank12.gif b/middleman-core/fixtures/asset-host-app/source/images/blank12.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank41.gif b/middleman-core/fixtures/asset-host-app/source/images/blank41.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank42.gif b/middleman-core/fixtures/asset-host-app/source/images/blank42.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank5.gif b/middleman-core/fixtures/asset-host-app/source/images/blank5.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank51.gif b/middleman-core/fixtures/asset-host-app/source/images/blank51.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank52.gif b/middleman-core/fixtures/asset-host-app/source/images/blank52.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank6.gif b/middleman-core/fixtures/asset-host-app/source/images/blank6.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank61.gif b/middleman-core/fixtures/asset-host-app/source/images/blank61.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank62.gif b/middleman-core/fixtures/asset-host-app/source/images/blank62.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank7.gif b/middleman-core/fixtures/asset-host-app/source/images/blank7.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank71.gif b/middleman-core/fixtures/asset-host-app/source/images/blank71.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank72.gif b/middleman-core/fixtures/asset-host-app/source/images/blank72.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank8.gif b/middleman-core/fixtures/asset-host-app/source/images/blank8.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank81.gif b/middleman-core/fixtures/asset-host-app/source/images/blank81.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/asset-host-app/source/images/blank82.gif b/middleman-core/fixtures/asset-host-app/source/images/blank82.gif
new file mode 100644
index 00000000..e69de29b
diff --git a/middleman-core/fixtures/sinatra-app/config.rb b/middleman-core/fixtures/sinatra-app/config.rb
deleted file mode 100644
index 0251a715..00000000
--- a/middleman-core/fixtures/sinatra-app/config.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require "sinatra"
-
-class MySinatra < Sinatra::Base
-  get "/" do
-    "Hello World (Sinatra)"
-  end
-  get "/derp.html" do
-    "De doo"
-  end
-end
-
-map "/sinatra" do
-  run MySinatra
-end
diff --git a/middleman-core/fixtures/sinatra-app/source/index.html.erb b/middleman-core/fixtures/sinatra-app/source/index.html.erb
deleted file mode 100644
index 8b59c41c..00000000
--- a/middleman-core/fixtures/sinatra-app/source/index.html.erb
+++ /dev/null
@@ -1,5 +0,0 @@
----
-layout: false
----
-
-Hello World (Middleman)
\ No newline at end of file
diff --git a/middleman-core/lib/middleman-core/application.rb b/middleman-core/lib/middleman-core/application.rb
index 379d1e81..4ecd40f8 100644
--- a/middleman-core/lib/middleman-core/application.rb
+++ b/middleman-core/lib/middleman-core/application.rb
@@ -157,12 +157,12 @@ module Middleman
     define_setting :layout, :_auto_layout, 'Default layout name'
 
     # Which file extensions have a layout by default.
-    # @return [Array.<String>]
-    define_setting :extensions_with_layout, %w(.htm .html .xhtml .php), 'Which file extensions have a layout by default.'
+    # @return [Set.<String>]
+    define_setting :extensions_with_layout, %w(.htm .html .xhtml .php), 'Which file extensions have a layout by default.', set: true
 
     # Which file extensions are "assets."
     # @return [Array.<String>]
-    define_setting :asset_extensions, %w(.css .png .jpg .jpeg .webp .svg .svgz .js .gif .ttf .otf .woff .woff2 .eot .ico .map), 'Which file extensions are treated as assets.'
+    define_setting :asset_extensions, %w(.css .png .jpg .jpeg .webp .svg .svgz .js .gif .ttf .otf .woff .woff2 .eot .ico .map), 'Which file extensions are treated as assets.', set: true
 
     # Default string encoding for templates and output.
     # @return [String]
diff --git a/middleman-core/lib/middleman-core/builder.rb b/middleman-core/lib/middleman-core/builder.rb
index 1796d4d7..c84bfa39 100644
--- a/middleman-core/lib/middleman-core/builder.rb
+++ b/middleman-core/lib/middleman-core/builder.rb
@@ -2,7 +2,6 @@ require 'pathname'
 require 'fileutils'
 require 'tempfile'
 require 'parallel'
-require 'middleman-core/rack'
 require 'middleman-core/callback_manager'
 require 'middleman-core/contracts'
 
@@ -39,9 +38,6 @@ module Middleman
       @cleaning = opts.fetch(:clean)
       @parallel = opts.fetch(:parallel, true)
 
-      rack_app = ::Middleman::Rack.new(@app).to_app
-      @rack = ::Rack::MockRequest.new(rack_app)
-
       @callbacks = ::Middleman::CallbackManager.new
       @callbacks.install_methods!(self, [:on_build_event])
     end
@@ -227,15 +223,7 @@ module Middleman
           if resource.binary?
             export_file!(output_file, resource.file_descriptor[:full_path])
           else
-            response = @rack.get(::URI.escape(resource.request_path))
-
-            # If we get a response, save it to a tempfile.
-            if response.status == 200
-              export_file!(output_file, binary_encode(response.body))
-            else
-              trigger(:error, output_file, response.body)
-              return false
-            end
+            export_file!(output_file, binary_encode(resource.render))
           end
         rescue => e
           trigger(:error, output_file, "#{e}\n#{e.backtrace.join("\n")}")
diff --git a/middleman-core/lib/middleman-core/configuration.rb b/middleman-core/lib/middleman-core/configuration.rb
index c916fc90..0d6d9be7 100644
--- a/middleman-core/lib/middleman-core/configuration.rb
+++ b/middleman-core/lib/middleman-core/configuration.rb
@@ -1,3 +1,5 @@
+require 'set'
+
 module Middleman
   module Configuration
     # A class that manages a collection of documented settings.
@@ -129,23 +131,37 @@ module Middleman
 
       def initialize(key, default, description, options={})
         @value_set = false
+        @array_wrapped_value = nil
+        @array_wrapped_default = nil
         self.key = key
         self.default = default
         self.description = description
         self.options = options
+
+        @array_wrapped_default = if self.default && options[:set] && self.default.is_a?(Array)
+          Set.new(self.default)
+        end
       end
 
       # The user-supplied value for this setting, overriding the default
       def value=(value)
         @value = value
         @value_set = true
+
+        @array_wrapped_value = if @value && options[:set] && @value.is_a?(Array)
+          Set.new(@value)
+        end
       end
 
       # The effective value of the setting, which may be the default
       # if the user has not set a value themselves. Note that even if the
       # user sets the value to nil it will override the default.
       def value
-        value_set? ? @value : default
+        if value_set?
+          @array_wrapped_value ? @array_wrapped_value : @value
+        else
+          @array_wrapped_default ? @array_wrapped_default : default
+        end
       end
 
       # Whether or not there has been a value set beyond the default
diff --git a/middleman-core/lib/middleman-core/core_extensions.rb b/middleman-core/lib/middleman-core/core_extensions.rb
index e38be937..ea31f89a 100644
--- a/middleman-core/lib/middleman-core/core_extensions.rb
+++ b/middleman-core/lib/middleman-core/core_extensions.rb
@@ -19,12 +19,6 @@ Middleman::Extensions.register :data, auto_activate: :before_sitemap do
   Middleman::CoreExtensions::Data
 end
 
-# Rewrite embedded URLs via Rack
-Middleman::Extensions.register :inline_url_rewriter, auto_activate: :before_sitemap do
-  require 'middleman-core/core_extensions/inline_url_rewriter'
-  Middleman::CoreExtensions::InlineURLRewriter
-end
-
 # Catch and show exceptions at the Rack level
 Middleman::Extensions.register :show_exceptions, auto_activate: :before_configuration, modes: [:server] do
   require 'middleman-core/core_extensions/show_exceptions'
diff --git a/middleman-core/lib/middleman-core/core_extensions/inline_url_rewriter.rb b/middleman-core/lib/middleman-core/core_extensions/inline_url_rewriter.rb
deleted file mode 100644
index 43354e97..00000000
--- a/middleman-core/lib/middleman-core/core_extensions/inline_url_rewriter.rb
+++ /dev/null
@@ -1,135 +0,0 @@
-require 'rack'
-require 'rack/response'
-require 'memoist'
-require 'middleman-core/util'
-require 'middleman-core/contracts'
-
-module Middleman
-  module CoreExtensions
-    class InlineURLRewriter < ::Middleman::Extension
-      include Contracts
-
-      expose_to_application rewrite_inline_urls: :add
-
-      REWRITER_DESCRIPTOR = {
-        id: Symbol,
-        proc: Or[Proc, Method],
-        url_extensions: ArrayOf[String],
-        source_extensions: ArrayOf[String],
-        ignore: ArrayOf[::Middleman::Util::IGNORE_DESCRIPTOR],
-        after: Maybe[Symbol]
-      }.freeze
-
-      def initialize(app, options_hash={}, &block)
-        super
-
-        @rewriters = {}
-      end
-
-      Contract REWRITER_DESCRIPTOR => Any
-      def add(options)
-        @rewriters[options] = options
-      end
-
-      def after_configuration
-        return if @rewriters.empty?
-
-        rewriters = @rewriters.values.sort do |a, b|
-          if b[:after] && b[:after] == a[:id]
-            1
-          else
-            0
-          end
-        end
-
-        app.use Rack, rewriters: rewriters, middleman_app: @app
-      end
-
-      class Rack
-        extend Memoist
-        include Contracts
-
-        Contract RespondTo[:call], {
-          middleman_app: IsA['Middleman::Application'],
-          rewriters: ArrayOf[REWRITER_DESCRIPTOR]
-        } => Any
-        def initialize(app, options={})
-          @rack_app = app
-          @middleman_app = options.fetch(:middleman_app)
-          @rewriters = options.fetch(:rewriters)
-
-          all_source_exts = @rewriters
-                            .reduce([]) { |sum, rewriter| sum + rewriter[:source_extensions] }
-                            .flatten
-                            .uniq
-          @source_exts_regex_text = Regexp.union(all_source_exts).to_s
-
-          @all_asset_exts = @rewriters
-                            .reduce([]) { |sum, rewriter| sum + rewriter[:url_extensions] }
-                            .flatten
-                            .uniq
-        end
-
-        def call(env)
-          status, headers, response = @rack_app.call(env)
-
-          # Allow configuration or upstream request to skip all rewriting
-          return [status, headers, response] if env['bypass_inline_url_rewriter'] == 'true'
-
-          path = ::Middleman::Util.full_path(env['PATH_INFO'], @middleman_app)
-
-          return [status, headers, response] unless path =~ /(^\/$)|(#{@source_exts_regex_text}$)/
-          return [status, headers, response] unless body = ::Middleman::Util.extract_response_text(response)
-
-          dirpath = ::Pathname.new(File.dirname(path))
-
-          rewritten = ::Middleman::Util.instrument 'inline_url_rewriter', path: path do
-            ::Middleman::Util.rewrite_paths(body, path, @all_asset_exts, @middleman_app) do |asset_path|
-              uri = ::Middleman::Util.parse_uri(asset_path)
-
-              relative_path = uri.host.nil?
-
-              full_asset_path = if relative_path
-                dirpath.join(asset_path).to_s
-              else
-                asset_path
-              end
-
-              @rewriters.each do |rewriter|
-                uid = rewriter.fetch(:id)
-
-                # Allow upstream request to skip this specific rewriting
-                next if env["bypass_inline_url_rewriter_#{uid}"] == 'true'
-
-                exts = rewriter.fetch(:url_extensions)
-                next unless exts.include?(::File.extname(asset_path))
-
-                source_exts = rewriter.fetch(:source_extensions)
-                next unless source_exts.include?(::File.extname(path))
-
-                ignore = rewriter.fetch(:ignore)
-                next if ignore.any? { |r| ::Middleman::Util.should_ignore?(r, full_asset_path) }
-
-                rewrite_ignore = Array(rewriter[:rewrite_ignore] || [])
-                next if rewrite_ignore.any? { |i| ::Middleman::Util.path_match(i, path) }
-
-                proc = rewriter.fetch(:proc)
-
-                result = proc.call(asset_path, dirpath, path)
-                asset_path = result if result
-              end
-
-              asset_path
-            end
-          end
-
-          ::Rack::Response.new(
-            rewritten,
-            status,
-            headers
-          ).finish
-        end
-      end
-    end
-  end
-end
diff --git a/middleman-core/lib/middleman-core/extension.rb b/middleman-core/lib/middleman-core/extension.rb
index 9805455a..0d1f212d 100644
--- a/middleman-core/lib/middleman-core/extension.rb
+++ b/middleman-core/lib/middleman-core/extension.rb
@@ -60,7 +60,7 @@ module Middleman
   # There are also some less common hooks that can be listened to from within an extension's `initialize` method:
   #
   # * `app.before_render {|body, path, locs, template_class| ... }` - Manipulate template sources before they are rendered.
-  # * `app.after_render {|content, path, locs, template_class| ... }` - Manipulate output text after a template has been rendered. It is also common to install a Rack middleware to do this instead.
+  # * `app.after_render {|content, path, locs, template_class| ... }` - Manipulate output text after a template has been rendered.
   # * `app.ready { ... }` - Run code once Middleman is ready to serve or build files (after `after_configuration`).
 
   #
diff --git a/middleman-core/lib/middleman-core/extensions/asset_hash.rb b/middleman-core/lib/middleman-core/extensions/asset_hash.rb
index b0b955f9..f78eed5e 100644
--- a/middleman-core/lib/middleman-core/extensions/asset_hash.rb
+++ b/middleman-core/lib/middleman-core/extensions/asset_hash.rb
@@ -1,18 +1,15 @@
 require 'middleman-core/util'
-require 'middleman-core/rack'
 
 class Middleman::Extensions::AssetHash < ::Middleman::Extension
-  option :sources, %w(.css .htm .html .js .php .xhtml), 'List of extensions that are searched for hashable assets.'
-  option :exts, nil, 'List of extensions that get asset hashes appended to them.'
+  option :sources, %w(.css .htm .html .js .php .xhtml), 'List of extensions that are searched for hashable assets.', set: true
+  option :exts, nil, 'List of extensions that get asset hashes appended to them.', set: true
   option :ignore, [], 'Regexes of filenames to skip adding asset hashes to'
   option :rewrite_ignore, [], 'Regexes of filenames to skip processing for path rewrites'
 
   def initialize(app, options_hash={}, &block)
     super
 
-    require 'addressable/uri'
     require 'digest/sha1'
-    require 'rack/mock'
 
     # Allow specifying regexes to ignore, plus always ignore apple touch icons
     @ignore = Array(options.ignore) + [/^apple-touch-icon/]
@@ -20,14 +17,6 @@ class Middleman::Extensions::AssetHash < ::Middleman::Extension
     # Exclude .ico from the default list because browsers expect it
     # to be named "favicon.ico"
     @exts = options.exts || (app.config[:asset_extensions] - %w(.ico))
-
-    app.rewrite_inline_urls id: :asset_hash,
-                            url_extensions: @exts.sort.reverse,
-                            source_extensions: options.sources,
-                            ignore: @ignore,
-                            rewrite_ignore: options.rewrite_ignore,
-                            proc: method(:rewrite_url),
-                            after: :asset_host
   end
 
   Contract String, Or[String, Pathname], Any => Maybe[String]
@@ -45,7 +34,6 @@ class Middleman::Extensions::AssetHash < ::Middleman::Extension
 
     replacement_path = "/#{asset_page.destination_path}"
     replacement_path = Pathname.new(replacement_path).relative_path_from(dirpath).to_s if relative_path
-
     replacement_path
   end
 
@@ -53,9 +41,18 @@ class Middleman::Extensions::AssetHash < ::Middleman::Extension
   # @return Array<Middleman::Sitemap::Resource>
   Contract ResourceList => ResourceList
   def manipulate_resource_list(resources)
-    @rack_client ||= begin
-      rack_app = ::Middleman::Rack.new(app).to_app
-      ::Rack::MockRequest.new(rack_app)
+    resources.each do |r|
+      next unless r.destination_path.end_with?('/', *options.sources)
+      next if Array(options.rewrite_ignore || []).any? do |i|
+        ::Middleman::Util.path_match(i, "/#{r.destination_path}")
+      end
+
+      r.filters << ::Middleman::InlineURLRewriter.new(:asset_hash,
+                                                      app,
+                                                      r,
+                                                      url_extensions: @exts,
+                                                      ignore: options.ignore,
+                                                      proc: method(:rewrite_url))
     end
 
     # Process resources in order: binary images and fonts, then SVG, then JS/CSS.
@@ -81,15 +78,9 @@ class Middleman::Extensions::AssetHash < ::Middleman::Extension
     digest = if resource.binary?
       ::Digest::SHA1.file(resource.source_file).hexdigest[0..7]
     else
-      # Render through the Rack interface so middleware and mounted apps get a shot
-      response = @rack_client.get(
-        ::URI.escape(resource.destination_path),
-        'bypass_inline_url_rewriter_asset_hash' => 'true'
-      )
-
-      raise "#{resource.path} should be in the sitemap!" unless response.status == 200
-
-      ::Digest::SHA1.hexdigest(response.body)[0..7]
+      # Render without asset hash
+      body = resource.render { |f| !f.respond_to?(:filter_name) || f.filter_name != :asset_hash }
+      ::Digest::SHA1.hexdigest(body)[0..7]
     end
 
     resource.destination_path = resource.destination_path.sub(/\.(\w+)$/) { |ext| "-#{digest}#{ext}" }
diff --git a/middleman-core/lib/middleman-core/extensions/asset_host.rb b/middleman-core/lib/middleman-core/extensions/asset_host.rb
index 7cb83d07..b076299d 100644
--- a/middleman-core/lib/middleman-core/extensions/asset_host.rb
+++ b/middleman-core/lib/middleman-core/extensions/asset_host.rb
@@ -1,5 +1,3 @@
-require 'addressable/uri'
-
 class Middleman::Extensions::AssetHost < ::Middleman::Extension
   option :host, nil, 'The asset host to use or a Proc to determine asset host', required: true
   option :exts, nil, 'List of extensions that get cache busters strings appended to them.'
@@ -7,15 +5,22 @@ class Middleman::Extensions::AssetHost < ::Middleman::Extension
   option :ignore, [], 'Regexes of filenames to skip adding query strings to'
   option :rewrite_ignore, [], 'Regexes of filenames to skip processing for host rewrites'
 
-  def initialize(app, options_hash={}, &block)
-    super
+  Contract ResourceList => ResourceList
+  def manipulate_resource_list(resources)
+    resources.each do |r|
+      next unless r.destination_path.end_with?('/', *options.sources)
+      next if Array(options.rewrite_ignore || []).any? do |i|
+        ::Middleman::Util.path_match(i, "/#{r.destination_path}")
+      end
 
-    app.rewrite_inline_urls id: :asset_host,
-                            url_extensions: options.exts || app.config[:asset_extensions],
-                            source_extensions: options.sources,
-                            ignore: options.ignore,
-                            rewrite_ignore: options.rewrite_ignore,
-                            proc: method(:rewrite_url)
+      r.filters << ::Middleman::InlineURLRewriter.new(:asset_host,
+                                                      app,
+                                                      r,
+                                                      after_filter: :asset_hash,
+                                                      url_extensions: options.exts || app.config[:asset_extensions],
+                                                      ignore: options.ignore,
+                                                      proc: method(:rewrite_url))
+    end
   end
 
   Contract String, Or[String, Pathname], Any => String
diff --git a/middleman-core/lib/middleman-core/extensions/cache_buster.rb b/middleman-core/lib/middleman-core/extensions/cache_buster.rb
index 2de11632..ea723a81 100644
--- a/middleman-core/lib/middleman-core/extensions/cache_buster.rb
+++ b/middleman-core/lib/middleman-core/extensions/cache_buster.rb
@@ -1,19 +1,25 @@
 # The Cache Buster extension
 class Middleman::Extensions::CacheBuster < ::Middleman::Extension
-  option :exts, nil, 'List of extensions that get cache busters strings appended to them.'
-  option :sources, %w(.css .htm .html .js .php .xhtml), 'List of extensions that are searched for bustable assets.'
+  option :exts, nil, 'List of extensions that get cache busters strings appended to them.', set: true
+  option :sources, %w(.css .htm .html .js .php .xhtml), 'List of extensions that are searched for bustable assets.', set: true
   option :ignore, [], 'Regexes of filenames to skip adding query strings to'
   option :rewrite_ignore, [], 'Regexes of filenames to skip processing for path rewrites'
 
-  def initialize(app, options_hash={}, &block)
-    super
+  Contract ResourceList => ResourceList
+  def manipulate_resource_list(resources)
+    resources.each do |r|
+      next unless r.destination_path.end_with?('/', *options.sources)
+      next if Array(options.rewrite_ignore || []).any? do |i|
+        ::Middleman::Util.path_match(i, "/#{r.destination_path}")
+      end
 
-    app.rewrite_inline_urls id: :cache_buster,
-                            url_extensions: options.exts || app.config[:asset_extensions],
-                            source_extensions: options.sources,
-                            ignore: options.ignore,
-                            rewrite_ignore: options.rewrite_ignore,
-                            proc: method(:rewrite_url)
+      r.filters << ::Middleman::InlineURLRewriter.new(:cache_buster,
+                                                      app,
+                                                      r,
+                                                      url_extensions: options.exts || app.config[:asset_extensions],
+                                                      ignore: options.ignore,
+                                                      proc: method(:rewrite_url))
+    end
   end
 
   Contract String, Or[String, Pathname], Any => String
diff --git a/middleman-core/lib/middleman-core/extensions/directory_indexes.rb b/middleman-core/lib/middleman-core/extensions/directory_indexes.rb
index cef88868..3bc340ee 100644
--- a/middleman-core/lib/middleman-core/extensions/directory_indexes.rb
+++ b/middleman-core/lib/middleman-core/extensions/directory_indexes.rb
@@ -1,3 +1,5 @@
+require 'set'
+
 # Directory Indexes extension
 class Middleman::Extensions::DirectoryIndexes < ::Middleman::Extension
   # This should run after most other sitemap manipulators so that it
@@ -11,7 +13,7 @@ class Middleman::Extensions::DirectoryIndexes < ::Middleman::Extension
     index_file = app.config[:index_file]
     new_index_path = "/#{index_file}"
 
-    extensions = %w(.htm .html .php .xhtml)
+    extensions = Set.new(%w(.htm .html .php .xhtml))
 
     resources.each do |resource|
       # Check if it would be pointless to reroute
diff --git a/middleman-core/lib/middleman-core/extensions/gzip.rb b/middleman-core/lib/middleman-core/extensions/gzip.rb
index 0483fe32..a633f78f 100644
--- a/middleman-core/lib/middleman-core/extensions/gzip.rb
+++ b/middleman-core/lib/middleman-core/extensions/gzip.rb
@@ -10,7 +10,7 @@
 # to .css, .htm, .html, .js, and .xhtml
 #
 class Middleman::Extensions::Gzip < ::Middleman::Extension
-  option :exts, %w(.css .htm .html .js .svg .xhtml), 'File extensions to Gzip when building.'
+  option :exts, %w(.css .htm .html .js .svg .xhtml), 'File extensions to Gzip when building.', set: true
   option :ignore, [], 'Patterns to avoid gzipping'
   option :overwrite, false, 'Overwrite original files instead of adding .gz extension.'
 
diff --git a/middleman-core/lib/middleman-core/extensions/minify_css.rb b/middleman-core/lib/middleman-core/extensions/minify_css.rb
index 067b25bf..9174322f 100644
--- a/middleman-core/lib/middleman-core/extensions/minify_css.rb
+++ b/middleman-core/lib/middleman-core/extensions/minify_css.rb
@@ -1,5 +1,5 @@
-require 'memoist'
 require 'middleman-core/contracts'
+require 'rack/mime'
 
 # Minify CSS Extension
 class Middleman::Extensions::MinifyCss < ::Middleman::Extension
@@ -9,17 +9,10 @@ class Middleman::Extensions::MinifyCss < ::Middleman::Extension
     require 'sass'
     SassCompressor
   }, 'Set the CSS compressor to use.'
-  option :content_types, %w(text/css), 'Content types of resources that contain CSS'
-  option :inline_content_types, %w(text/html text/php), 'Content types of resources that contain inline CSS'
+  option :content_types, %w(text/css), 'Content types of resources that contain CSS', set: true
+  option :inline_content_types, %w(text/html text/php), 'Content types of resources that contain inline CSS', set: true
 
-  def ready
-    # Setup Rack middleware to minify CSS
-    app.use Rack, compressor: options[:compressor],
-                  ignore: Array(options[:ignore]) + [/\.min\./],
-                  inline: options[:inline],
-                  content_types: options[:content_types],
-                  inline_content_types: options[:inline_content_types]
-  end
+  INLINE_CSS_REGEX = /(<style[^>]*>\s*(?:\/\*<!\[CDATA\[\*\/\n)?)(.*?)((?:(?:\n\s*)?\/\*\]\]>\*\/)?\s*<\/style>)/m
 
   class SassCompressor
     def self.compress(style, options={})
@@ -29,97 +22,61 @@ class Middleman::Extensions::MinifyCss < ::Middleman::Extension
     end
   end
 
-  # Rack middleware to look for CSS and compress it
-  class Rack
-    extend Memoist
-    include Contracts
-    INLINE_CSS_REGEX = /(<style[^>]*>\s*(?:\/\*<!\[CDATA\[\*\/\n)?)(.*?)((?:(?:\n\s*)?\/\*\]\]>\*\/)?\s*<\/style>)/m
+  def initialize(app, options_hash={}, &block)
+    super
 
-    # Init
-    # @param [Class] app
-    # @param [Hash] options
-    Contract RespondTo[:call], {
-      ignore: ArrayOf[PATH_MATCHER],
-      inline: Bool,
-      compressor: Or[Proc, RespondTo[:to_proc], RespondTo[:compress]]
-    } => Any
-    def initialize(app, options={})
-      @app = app
-      @ignore = options.fetch(:ignore)
-      @inline = options.fetch(:inline)
-
-      @compressor = options.fetch(:compressor)
-      @compressor = @compressor.to_proc if @compressor.respond_to? :to_proc
-      @compressor = @compressor.call if @compressor.is_a? Proc
-      @content_types = options[:content_types]
-      @inline_content_types = options[:inline_content_types]
-    end
-
-    # Rack interface
-    # @param [Rack::Environmemt] env
-    # @return [Array]
-    def call(env)
-      status, headers, response = @app.call(env)
-
-      content_type = headers['Content-Type'].try(:slice, /^[^;]*/)
-      path = env['PATH_INFO']
-
-      minified = if @inline && minifiable_inline?(content_type)
-        minify_inline(::Middleman::Util.extract_response_text(response))
-      elsif minifiable?(content_type) && !ignore?(path)
-        minify(::Middleman::Util.extract_response_text(response))
-      end
-
-      if minified
-        headers['Content-Length'] = ::Rack::Utils.bytesize(minified).to_s
-        response = [minified]
-      end
-
-      [status, headers, response]
-    end
-
-    private
-
-    # Whether the path should be ignored
-    # @param [String] path
-    # @return [Boolean]
-    def ignore?(path)
-      @ignore.any? { |ignore| ::Middleman::Util.path_match(ignore, path) }
-    end
-    memoize :ignore?
-
-    # Whether this type of content can be minified
-    # @param [String, nil] content_type
-    # @return [Boolean]
-    def minifiable?(content_type)
-      @content_types.include?(content_type)
-    end
-    memoize :minifiable?
-
-    # Whether this type of content contains inline content that can be minified
-    # @param [String, nil] content_type
-    # @return [Boolean]
-    def minifiable_inline?(content_type)
-      @inline_content_types.include?(content_type)
-    end
-    memoize :minifiable_inline?
-
-    # Minify the content
-    # @param [String] content
-    # @return [String]
-    def minify(content)
-      @compressor.compress(content)
-    end
-    memoize :minify
-
-    # Detect and minify inline content
-    # @param [String] content
-    # @return [String]
-    def minify_inline(content)
-      content.gsub(INLINE_CSS_REGEX) do
-        $1 + minify($2) + $3
-      end
-    end
-    memoize :minify_inline
+    @ignore = Array(options[:ignore]) + [/\.min\./]
+    @compressor = options[:compressor]
+    @compressor = @compressor.to_proc if @compressor.respond_to? :to_proc
+    @compressor = @compressor.call if @compressor.is_a? Proc
   end
+
+  Contract ResourceList => ResourceList
+  def manipulate_resource_list(resources)
+    resources.each do |r|
+      type = r.content_type.try(:slice, /^[^;]*/)
+      if options[:inline] && minifiable_inline?(type)
+        r.filters << method(:minify_inline)
+      elsif minifiable?(type) && !ignore?(r.destination_path)
+        r.filters << method(:minify)
+      end
+    end
+  end
+
+  # Whether the path should be ignored
+  Contract String => Bool
+  def ignore?(path)
+    @ignore.any? { |ignore| ::Middleman::Util.path_match(ignore, path) }
+  end
+  memoize :ignore?
+
+  # Whether this type of content can be minified
+  Contract Maybe[String] => Bool
+  def minifiable?(content_type)
+    options[:content_types].include?(content_type)
+  end
+  memoize :minifiable?
+
+  # Whether this type of content contains inline content that can be minified
+  Contract Maybe[String] => Bool
+  def minifiable_inline?(content_type)
+    options[:inline_content_types].include?(content_type)
+  end
+  memoize :minifiable_inline?
+
+  # Minify the content
+  Contract String => String
+  def minify(content)
+    @compressor.compress(content)
+  end
+  memoize :minify
+
+  # Detect and minify inline content
+  Contract String => String
+  def minify_inline(content)
+    content.gsub(INLINE_CSS_REGEX) do
+      $1 + minify($2) + $3
+    end
+  end
+  memoize :minify_inline
 end
diff --git a/middleman-core/lib/middleman-core/extensions/minify_javascript.rb b/middleman-core/lib/middleman-core/extensions/minify_javascript.rb
index 48490470..02172e91 100644
--- a/middleman-core/lib/middleman-core/extensions/minify_javascript.rb
+++ b/middleman-core/lib/middleman-core/extensions/minify_javascript.rb
@@ -9,122 +9,79 @@ class Middleman::Extensions::MinifyJavascript < ::Middleman::Extension
     require 'uglifier'
     ::Uglifier.new
   }, 'Set the JS compressor to use.'
-  option :content_types, %w(application/javascript), 'Content types of resources that contain JS'
-  option :inline_content_types, %w(text/html text/php), 'Content types of resources that contain inline JS'
+  option :content_types, %w(application/javascript), 'Content types of resources that contain JS', set: true
+  option :inline_content_types, %w(text/html text/php), 'Content types of resources that contain inline JS', set: true
 
-  def ready
-    # Setup Rack middleware to minify JS
-    app.use Rack, compressor: options[:compressor],
-                  ignore: Array(options[:ignore]) + [/\.min\./],
-                  inline: options[:inline],
-                  content_types: options[:content_types],
-                  inline_content_types: options[:inline_content_types]
+  INLINE_JS_REGEX = /(<script[^>]*>\s*(?:\/\/(?:(?:<!--)|(?:<!\[CDATA\[))\n)?)(.*?)((?:(?:\n\s*)?\/\/(?:(?:-->)|(?:\]\]>)))?\s*<\/script>)/m
+
+  def initialize(app, options_hash={}, &block)
+    super
+
+    @ignore = Array(options[:ignore]) + [/\.min\./]
+    @compressor = options[:compressor]
+    @compressor = @compressor.to_proc if @compressor.respond_to? :to_proc
+    @compressor = @compressor.call if @compressor.is_a? Proc
   end
 
-  # Rack middleware to look for JS and compress it
-  class Rack
-    extend Memoist
-    include Contracts
-    INLINE_JS_REGEX = /(<script[^>]*>\s*(?:\/\/(?:(?:<!--)|(?:<!\[CDATA\[))\n)?)(.*?)((?:(?:\n\s*)?\/\/(?:(?:-->)|(?:\]\]>)))?\s*<\/script>)/m
-
-    # Init
-    # @param [Class] app
-    # @param [Hash] options
-    Contract RespondTo[:call], {
-      ignore: ArrayOf[PATH_MATCHER],
-      inline: Bool,
-      compressor: Or[Proc, RespondTo[:to_proc], RespondTo[:compress]]
-    } => Any
-    def initialize(app, options={})
-      @app = app
-      @ignore = options.fetch(:ignore)
-      @inline = options.fetch(:inline)
-
-      @compressor = options.fetch(:compressor)
-      @compressor = @compressor.to_proc if @compressor.respond_to? :to_proc
-      @compressor = @compressor.call if @compressor.is_a? Proc
-      @content_types = options[:content_types]
-      @inline_content_types = options[:inline_content_types]
-    end
-
-    # Rack interface
-    # @param [Rack::Environmemt] env
-    # @return [Array]
-    def call(env)
-      status, headers, response = @app.call(env)
-
-      type = headers['Content-Type'].try(:slice, /^[^;]*/)
-      @path = env['PATH_INFO']
-
-      minified = if @inline && minifiable_inline?(type)
-        minify_inline(::Middleman::Util.extract_response_text(response))
-      elsif minifiable?(type) && !ignore?(@path)
-        minify(::Middleman::Util.extract_response_text(response))
-      end
-
-      if minified
-        headers['Content-Length'] = ::Rack::Utils.bytesize(minified).to_s
-        response = [minified]
-      end
-
-      [status, headers, response]
-    end
-
-    private
-
-    # Whether the path should be ignored
-    # @param [String] path
-    # @return [Boolean]
-    def ignore?(path)
-      @ignore.any? { |ignore| Middleman::Util.path_match(ignore, path) }
-    end
-    memoize :ignore?
-
-    # Whether this type of content can be minified
-    # @param [String, nil] content_type
-    # @return [Boolean]
-    def minifiable?(content_type)
-      @content_types.include?(content_type)
-    end
-    memoize :minifiable?
-
-    # Whether this type of content contains inline content that can be minified
-    # @param [String, nil] content_type
-    # @return [Boolean]
-    def minifiable_inline?(content_type)
-      @inline_content_types.include?(content_type)
-    end
-    memoize :minifiable_inline?
-
-    # Minify the content
-    # @param [String] content
-    # @return [String]
-    def minify(content)
-      @compressor.compress(content)
-    rescue ExecJS::ProgramError => e
-      warn "WARNING: Couldn't compress JavaScript in #{@path}: #{e.message}"
-      content
-    end
-    memoize :minify
-
-    # Detect and minify inline content
-    # @param [String] content
-    # @return [String]
-    def minify_inline(content)
-      content.gsub(INLINE_JS_REGEX) do |match|
-        first = $1
-        inline_content = $2
-        last = $3
-
-        # Only compress script tags that contain JavaScript (as opposed to
-        # something like jQuery templates, identified with a "text/html" type).
-        if !first.include?('type=') || first.include?('text/javascript')
-          first + minify(inline_content) + last
-        else
-          match
-        end
+  Contract ResourceList => ResourceList
+  def manipulate_resource_list(resources)
+    resources.each do |r|
+      type = r.content_type.try(:slice, /^[^;]*/)
+      if options[:inline] && minifiable_inline?(type)
+        r.filters << method(:minify_inline)
+      elsif minifiable?(type) && !ignore?(r.destination_path)
+        r.filters << method(:minify)
       end
     end
-    memoize :minify_inline
   end
+
+  # Whether the path should be ignored
+  Contract String => Bool
+  def ignore?(path)
+    @ignore.any? { |ignore| ::Middleman::Util.path_match(ignore, path) }
+  end
+  memoize :ignore?
+
+  # Whether this type of content can be minified
+  Contract Maybe[String] => Bool
+  def minifiable?(content_type)
+    options[:content_types].include?(content_type)
+  end
+  memoize :minifiable?
+
+  # Whether this type of content contains inline content that can be minified
+  Contract Maybe[String] => Bool
+  def minifiable_inline?(content_type)
+    options[:inline_content_types].include?(content_type)
+  end
+  memoize :minifiable_inline?
+
+  # Minify the content
+  Contract String => String
+  def minify(content)
+    @compressor.compress(content)
+  rescue ::ExecJS::ProgramError => e
+    warn "WARNING: Couldn't compress JavaScript in #{@path}: #{e.message}"
+    content
+  end
+  memoize :minify
+
+  # Detect and minify inline content
+  Contract String => String
+  def minify_inline(content)
+    content.gsub(INLINE_JS_REGEX) do |match|
+      first = $1
+      inline_content = $2
+      last = $3
+
+      # Only compress script tags that contain JavaScript (as opposed to
+      # something like jQuery templates, identified with a "text/html" type).
+      if !first.include?('type=') || first.include?('text/javascript')
+        first + minify(inline_content) + last
+      else
+        match
+      end
+    end
+  end
+  memoize :minify_inline
 end
diff --git a/middleman-core/lib/middleman-core/extensions/relative_assets.rb b/middleman-core/lib/middleman-core/extensions/relative_assets.rb
index 853a7005..4d2e15db 100644
--- a/middleman-core/lib/middleman-core/extensions/relative_assets.rb
+++ b/middleman-core/lib/middleman-core/extensions/relative_assets.rb
@@ -1,26 +1,28 @@
-require 'addressable/uri'
-
 # Relative Assets extension
 class Middleman::Extensions::RelativeAssets < ::Middleman::Extension
-  option :exts, nil, 'List of extensions that get converted to relative paths.'
-  option :sources, %w(.css .htm .html .xhtml), 'List of extensions that are searched for relative assets.'
+  option :exts, nil, 'List of extensions that get converted to relative paths.', set: true
+  option :sources, %w(.css .htm .html .xhtml), 'List of extensions that are searched for relative assets.', set: true
   option :ignore, [], 'Regexes of filenames to skip converting to relative paths.'
   option :rewrite_ignore, [], 'Regexes of filenames to skip processing for path rewrites.'
   option :helpers_only, false, 'Allow only Ruby helpers to change paths.'
 
-  def initialize(app, options_hash={}, &block)
-    super
+  Contract ResourceList => ResourceList
+  def manipulate_resource_list(resources)
+    return resources if options[:helpers_only]
 
-    if options[:helpers_only]
-      return
+    resources.each do |r|
+      next unless r.destination_path.end_with?('/', *options.sources)
+      next if Array(options.rewrite_ignore || []).any? do |i|
+        ::Middleman::Util.path_match(i, "/#{r.destination_path}")
+      end
+
+      r.filters << ::Middleman::InlineURLRewriter.new(:relative_assets,
+                                                      app,
+                                                      r,
+                                                      url_extensions: options.exts || app.config[:asset_extensions],
+                                                      ignore: options.ignore,
+                                                      proc: method(:rewrite_url))
     end
-
-    app.rewrite_inline_urls id: :relative_assets,
-                            url_extensions: options.exts || app.config[:asset_extensions],
-                            source_extensions: options.sources,
-                            ignore: options.ignore,
-                            rewrite_ignore: options.rewrite_ignore,
-                            proc: method(:rewrite_url)
   end
 
   def mark_as_relative(file_path, opts, current_resource)
@@ -53,7 +55,7 @@ class Middleman::Extensions::RelativeAssets < ::Middleman::Extension
     end
 
     def asset_path(kind, source, options={})
-      super(kind, source,  app.extensions[:relative_assets].mark_as_relative(super, options, current_resource))
+      super(kind, source, app.extensions[:relative_assets].mark_as_relative(super, options, current_resource))
     end
   end
 
diff --git a/middleman-core/lib/middleman-core/inline_url_rewriter.rb b/middleman-core/lib/middleman-core/inline_url_rewriter.rb
new file mode 100644
index 00000000..ae572313
--- /dev/null
+++ b/middleman-core/lib/middleman-core/inline_url_rewriter.rb
@@ -0,0 +1,49 @@
+require 'middleman-core/util'
+require 'middleman-core/contracts'
+
+module Middleman
+  class InlineURLRewriter
+    include Contracts
+
+    attr_reader :filter_name
+    attr_reader :after_filter
+
+    def initialize(filter_name, app, resource, options={})
+      @filter_name = filter_name
+      @app = app
+      @resource = resource
+      @options = options
+
+      @after_filter = @options.fetch(:after_filter, nil)
+    end
+
+    Contract String => String
+    def execute_filter(body)
+      path = "/#{@resource.destination_path}"
+      dirpath = ::Pathname.new(File.dirname(path))
+
+      ::Middleman::Util.instrument 'inline_url_rewriter', path: path do
+        ::Middleman::Util.rewrite_paths(body, path, @options.fetch(:url_extensions), @app) do |asset_path|
+          uri = ::Middleman::Util.parse_uri(asset_path)
+
+          relative_path = uri.host.nil?
+          full_asset_path = if relative_path
+            dirpath.join(asset_path).to_s
+          else
+            asset_path
+          end
+
+          exts = @options.fetch(:url_extensions)
+          next unless exts.include?(::File.extname(asset_path))
+
+          next if @options.fetch(:ignore).any? { |r| ::Middleman::Util.should_ignore?(r, full_asset_path) }
+
+          result = @options.fetch(:proc).call(asset_path, dirpath, path)
+          asset_path = result if result
+
+          asset_path
+        end
+      end
+    end
+  end
+end
diff --git a/middleman-core/lib/middleman-core/rack.rb b/middleman-core/lib/middleman-core/rack.rb
index 293a2e43..797d3bf4 100644
--- a/middleman-core/lib/middleman-core/rack.rb
+++ b/middleman-core/lib/middleman-core/rack.rb
@@ -93,9 +93,6 @@ module Middleman
       request_path = ::Middleman::Util.full_path(request_path, @middleman)
       full_request_path = File.join(env['SCRIPT_NAME'], request_path) # Path including rack mount
 
-      # Run before callbacks
-      @middleman.execute_callbacks(:before)
-
       # Get the resource object for this path
       resource = @middleman.sitemap.find_resource_by_destination_path(request_path.gsub(' ', '%20'))
 
diff --git a/middleman-core/lib/middleman-core/sitemap/extensions/request_endpoints.rb b/middleman-core/lib/middleman-core/sitemap/extensions/request_endpoints.rb
index ede1cc64..85601960 100644
--- a/middleman-core/lib/middleman-core/sitemap/extensions/request_endpoints.rb
+++ b/middleman-core/lib/middleman-core/sitemap/extensions/request_endpoints.rb
@@ -9,14 +9,13 @@ module Middleman
         # Expose `endpoint`
         expose_to_config :endpoint
 
-        EndpointDescriptor = Struct.new(:path, :request_path, :block) do
+        EndpointDescriptor = Struct.new(:path, :block) do
           def execute_descriptor(app, resources)
-            r = EndpointResource.new(
+            r = ::Middleman::Sitemap::CallbackResource.new(
               app.sitemap,
               path,
-              request_path
+              &block
             )
-            r.output = block if block
 
             resources + [r]
           end
@@ -24,43 +23,10 @@ module Middleman
 
         # Setup a proxy from a path to a target
         # @param [String] path
-        # @param [Hash] opts The :path value gives a request path if it
         # differs from the output path
-        Contract String, Or[{ path: String }, Proc] => EndpointDescriptor
-        def endpoint(path, opts={}, &block)
-          if block_given?
-            EndpointDescriptor.new(path, path, block)
-          else
-            EndpointDescriptor.new(path, opts[:path] || path, nil)
-          end
-        end
-      end
-
-      class EndpointResource < ::Middleman::Sitemap::Resource
-        Contract Maybe[Proc]
-        attr_accessor :output
-
-        def initialize(store, path, request_path)
-          super(store, path)
-          @request_path = ::Middleman::Util.normalize_path(request_path)
-        end
-
-        Contract String
-        attr_reader :request_path
-
-        Contract Bool
-        def template?
-          true
-        end
-
-        Contract Args[Any] => String
-        def render(*)
-          return output.call if output
-        end
-
-        Contract Bool
-        def ignored?
-          false
+        Contract String, Proc => EndpointDescriptor
+        def endpoint(path, &block)
+          EndpointDescriptor.new(path, block)
         end
       end
     end
diff --git a/middleman-core/lib/middleman-core/sitemap/resource.rb b/middleman-core/lib/middleman-core/sitemap/resource.rb
index ce1bc100..f4a33f83 100644
--- a/middleman-core/lib/middleman-core/sitemap/resource.rb
+++ b/middleman-core/lib/middleman-core/sitemap/resource.rb
@@ -3,6 +3,7 @@ require 'middleman-core/sitemap/extensions/traversal'
 require 'middleman-core/file_renderer'
 require 'middleman-core/template_renderer'
 require 'middleman-core/contracts'
+require 'middleman-core/inline_url_rewriter'
 
 module Middleman
   # Sitemap namespace
@@ -39,24 +40,26 @@ module Middleman
       attr_reader :metadata
 
       attr_accessor :ignored
+      attr_accessor :filters
 
       # Initialize resource with parent store and URL
       # @param [Middleman::Sitemap::Store] store
       # @param [String] path
       # @param [String] source
-      Contract IsA['Middleman::Sitemap::Store'], String, Maybe[Or[IsA['Middleman::SourceFile'], String]] => Any
-      def initialize(store, path, source=nil)
+      Contract IsA['Middleman::Sitemap::Store'], String, Maybe[Any] => Any
+      def initialize(store, path, source_file=nil)
         @store       = store
         @app         = @store.app
         @path        = path
         @ignored     = false
+        @filters     = []
 
-        source = Pathname(source) if source && source.is_a?(String)
+        source_file = Pathname(source_file) if source_file && source_file.is_a?(String)
 
-        @file_descriptor = if source && source.is_a?(Pathname)
-          ::Middleman::SourceFile.new(source.relative_path_from(@app.source_dir), source, @app.source_dir, Set.new([:source]), 0)
+        @file_descriptor = if source_file && source_file.is_a?(Pathname)
+          ::Middleman::SourceFile.new(source_file.relative_path_from(@app.source_dir), source_file, @app.source_dir, Set.new([:source]), 0)
         else
-          source
+          source_file
         end
 
         @destination_path = @path
@@ -138,8 +141,45 @@ module Middleman
 
       # Render this resource
       # @return [String]
-      Contract Hash, Hash => String
+      # Contract Maybe[Hash], Maybe[Hash], Maybe[Proc] => String
       def render(opts={}, locs={})
+        body = render_without_filters(opts, locs)
+
+        return body if @filters.empty?
+
+        sortable_filters = @filters.select { |f| f.respond_to?(:filter_name) }.sort do |a, b|
+          if b.after_filter == a.filter_name
+            1
+          else
+            -1
+          end
+        end.reverse
+
+        n = 0
+        sorted_filters = @filters.sort_by do |m|
+          n += 1
+          idx = sortable_filters.index(m)
+
+          [idx.nil? ? 0 : idx, n]
+        end
+
+        sorted_filters.reduce(body) do |output, filter|
+          if block_given? && !yield(filter)
+            output
+          elsif filter.respond_to?(:execute_filter)
+            filter.execute_filter(output)
+          elsif filter.respond_to?(:call)
+            filter.call(output)
+          else
+            output
+          end
+        end
+      end
+
+      # Render this resource without content filters
+      # @return [String]
+      Contract Hash, Hash => String
+      def render_without_filters(opts={}, locs={})
         return ::Middleman::FileRenderer.new(@app, file_descriptor[:full_path].to_s).template_data_for_file unless template?
 
         md   = metadata
@@ -151,7 +191,7 @@ module Middleman
         opts[:layout] = false if !opts.key?(:layout) && !@app.config.extensions_with_layout.include?(ext)
 
         renderer = ::Middleman::TemplateRenderer.new(@app, file_descriptor[:full_path].to_s)
-        renderer.render(locs, opts)
+        renderer.render(locs, opts).to_str
       end
 
       # A path without the directory index - so foo/index.html becomes
@@ -204,9 +244,10 @@ module Middleman
     end
 
     class StringResource < Resource
-      def initialize(store, path, contents=nil, &block)
+      Contract IsA['Middleman::Sitemap::Store'], String, Maybe[Or[String, Proc]] => Any
+      def initialize(store, path, contents)
         @request_path = path
-        @contents = block_given? ? block : contents
+        @contents = contents
         super(store, path)
       end
 
@@ -215,7 +256,28 @@ module Middleman
       end
 
       def render(*)
-        @contents.respond_to?(:call) ? @contents.call : @contents
+        @contents
+      end
+
+      def binary?
+        false
+      end
+    end
+
+    class CallbackResource < Resource
+      Contract IsA['Middleman::Sitemap::Store'], String, Proc => Any
+      def initialize(store, path, &block)
+        @request_path = path
+        @contents = block
+        super(store, path)
+      end
+
+      def template?
+        true
+      end
+
+      def render(*)
+        @contents.call
       end
 
       def binary?
diff --git a/middleman-core/lib/middleman-core/util/data.rb b/middleman-core/lib/middleman-core/util/data.rb
index ce73540a..b0026293 100644
--- a/middleman-core/lib/middleman-core/util/data.rb
+++ b/middleman-core/lib/middleman-core/util/data.rb
@@ -94,7 +94,7 @@ module Middleman
                                     .transpose
                                     .map(&::Regexp.method(:union))
 
-        match = /
+        /
           \A(?:[^\r\n]*coding:[^\r\n]*\r?\n)?
           (?<start>#{start_delims})[ ]*\r?\n
           (?<frontmatter>.*?)[ ]*\r?\n?
diff --git a/middleman-core/lib/middleman-core/util/files.rb b/middleman-core/lib/middleman-core/util/files.rb
index 3d185cea..607b3bd5 100644
--- a/middleman-core/lib/middleman-core/util/files.rb
+++ b/middleman-core/lib/middleman-core/util/files.rb
@@ -56,10 +56,8 @@ module Middleman
 
     Contract String => String
     def step_through_extensions(path)
-      while ::Middleman::Util.tilt_class(path)
-        ext = ::File.extname(path)
-        break if ext.empty?
-
+      while ext = File.extname(path)
+        break if ext.empty? || !::Middleman::Util.tilt_class(ext)
         yield ext if block_given?
 
         # Strip templating extensions as long as Tilt knows them
diff --git a/middleman-core/lib/middleman-core/util/paths.rb b/middleman-core/lib/middleman-core/util/paths.rb
index 26f29442..b6543612 100644
--- a/middleman-core/lib/middleman-core/util/paths.rb
+++ b/middleman-core/lib/middleman-core/util/paths.rb
@@ -25,13 +25,15 @@ module Middleman
     def tilt_class(path)
       ::Tilt[path]
     end
-    memoize :tilt_class
+    # memoize :tilt_class
 
     # Normalize a path to not include a leading slash
     # @param [String] path
     # @return [String]
-    Contract String => String
+    Contract Any => String
     def normalize_path(path)
+      return path unless path.is_a?(String)
+
       # The tr call works around a bug in Ruby's Unicode handling
       ::URI.decode(path).sub(%r{^/}, '').tr('', '')
     end
diff --git a/middleman-core/lib/middleman-core/util/rack.rb b/middleman-core/lib/middleman-core/util/rack.rb
index 2459052b..6783ff2d 100644
--- a/middleman-core/lib/middleman-core/util/rack.rb
+++ b/middleman-core/lib/middleman-core/util/rack.rb
@@ -6,22 +6,9 @@ module Middleman
 
     module_function
 
-    # Extract the text of a Rack response as a string.
-    # Useful for extensions implemented as Rack middleware.
-    # @param response The response from #call
-    # @return [String] The whole response as a string.
-    Contract RespondTo[:each] => String
-    def extract_response_text(response)
-      # The rack spec states all response bodies must respond to each
-      result = ''
-      response.each do |part, _|
-        result << part
-      end
-      result
-    end
-
-    Contract String, String, ArrayOf[String], IsA['::Middleman::Application'], Proc => String
+    Contract String, String, SetOf[String], IsA['::Middleman::Application'], Proc => String
     def rewrite_paths(body, path, exts, app, &_block)
+      exts = exts.sort_by(&:length).reverse
       matcher = /([\'\"\(,]\s*|# sourceMappingURL=)([^\s\'\"\)\(>]+(#{::Regexp.union(exts)}))/
 
       url_fn_prefix = 'url('
diff --git a/middleman-core/lib/middleman-core/version.rb b/middleman-core/lib/middleman-core/version.rb
index 37f706a4..4fe534de 100644
--- a/middleman-core/lib/middleman-core/version.rb
+++ b/middleman-core/lib/middleman-core/version.rb
@@ -1,5 +1,5 @@
 module Middleman
   # Current Version
   # @return [String]
-  VERSION = '4.1.7'.freeze unless const_defined?(:VERSION)
+  VERSION = '4.2.0'.freeze unless const_defined?(:VERSION)
 end