diff --git a/.gitignore b/.gitignore
index 88e2e11e..aabe272b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,6 @@
+.byebug_history
 npm-debug.log
+manifest.yaml
 /.bundle
 .DS_Store
 coverage
diff --git a/middleman-core/features/front-matter-neighbor.feature b/middleman-core/features/front-matter-neighbor.feature
index e2e5cc69..9260ff41 100644
--- a/middleman-core/features/front-matter-neighbor.feature
+++ b/middleman-core/features/front-matter-neighbor.feature
@@ -22,7 +22,7 @@ Feature: Neighboring YAML Front Matter
     Then I should not see "---"
     When I go to "/raw-front-matter.php.frontmatter"
     Then I should see "File Not Found"
-    
+
   Scenario: YAML not on first line, with encoding
     Given the Server is running at "frontmatter-neighbor-app"
     When I go to "/front-matter-encoding.html"
@@ -35,7 +35,7 @@ Feature: Neighboring YAML Front Matter
     Given the Server is running at "frontmatter-neighbor-app"
     And the file "source/front-matter-change.html.erb" has the contents
       """
-      <%= current_page.data.title %>
+      FileA <%= current_page.data.title %>
       """
     And the file "source/front-matter-change.html.erb.frontmatter" has the contents
       """
@@ -43,6 +43,8 @@ Feature: Neighboring YAML Front Matter
       title: Hello World
       layout: false
       ---
+
+      FileB
       """
     When I go to "/front-matter-change.html"
     Then I should see "Hello World"
@@ -52,6 +54,8 @@ Feature: Neighboring YAML Front Matter
       title: Hola Mundo
       layout: false
       ---
+
+      FileC
       """
     When I go to "/front-matter-change.html"
     Then I should see "Hola Mundo"
diff --git a/middleman-core/lib/middleman-core/core_extensions/collections.rb b/middleman-core/lib/middleman-core/core_extensions/collections.rb
index 434455f1..22e6d281 100644
--- a/middleman-core/lib/middleman-core/core_extensions/collections.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/collections.rb
@@ -1,3 +1,4 @@
+require 'monitor'
 require 'middleman-core/core_extensions/collections/pagination'
 require 'middleman-core/core_extensions/collections/step_context'
 require 'middleman-core/core_extensions/collections/lazy_root'
@@ -41,6 +42,8 @@ module Middleman
           @values_by_name = {}
 
           @collector_roots = []
+
+          @lock = Monitor.new
         end
 
         def before_configuration
@@ -81,27 +84,35 @@ module Middleman
 
         Contract ResourceList => ResourceList
         def manipulate_resource_list(resources)
-          @collector_roots.each do |pair|
-            dataset = pair[:block].call(app, resources)
-            pair[:root].realize!(dataset)
-          end
+          @lock.synchronize do
+            @collector_roots.each do |pair|
+              dataset = pair[:block].call(app, resources)
+              pair[:root].realize!(dataset)
+            end
 
-          ctx = StepContext.new
-          leaves = @leaves.dup
+            ctx = StepContext.new
+            StepContext.current = ctx
 
-          @collectors_by_name.each do |k, v|
-            @values_by_name[k] = v.value(ctx)
-            leaves.delete v
-          end
+            leaves = @leaves.dup
 
-          # Execute code paths
-          leaves.each do |v|
-            v.value(ctx)
-          end
+            @collectors_by_name.each do |k, v|
+              @values_by_name[k] = v.value(ctx)
+              leaves.delete v
+            end
 
-          # Inject descriptors
-          ctx.descriptors.reduce(resources) do |sum, d|
-            d.execute_descriptor(app, sum)
+            # Execute code paths
+            leaves.each do |v|
+              v.value(ctx)
+            end
+
+            # Inject descriptors
+            results = ctx.descriptors.reduce(resources) do |sum, d|
+              d.execute_descriptor(app, sum)
+            end
+
+            StepContext.current = nil
+
+            results
           end
         end
       end
diff --git a/middleman-core/lib/middleman-core/core_extensions/collections/step_context.rb b/middleman-core/lib/middleman-core/core_extensions/collections/step_context.rb
index 2ce90b83..0b17870d 100644
--- a/middleman-core/lib/middleman-core/core_extensions/collections/step_context.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/collections/step_context.rb
@@ -2,8 +2,12 @@ module Middleman
   module CoreExtensions
     module Collections
       class StepContext
-        def self.add_to_context(name, &func)
-          send(:define_method, :"_internal_#{name}", &func)
+        class << self
+          attr_accessor :current
+
+          def add_to_context(name, &func)
+            send(:define_method, :"_internal_#{name}", &func)
+          end
         end
 
         attr_reader :descriptors
diff --git a/middleman-core/lib/middleman-core/core_extensions/data.rb b/middleman-core/lib/middleman-core/core_extensions/data.rb
index 18057465..d711ef4f 100644
--- a/middleman-core/lib/middleman-core/core_extensions/data.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/data.rb
@@ -88,6 +88,8 @@ module Middleman
         def update_files(updated_files, removed_files)
           updated_files.each(&method(:touch_file))
           removed_files.each(&method(:remove_file))
+
+          @app.sitemap.rebuild_resource_list!(:touched_data_file)
         end
 
         # Update the internal cache for a given file path
diff --git a/middleman-core/lib/middleman-core/core_extensions/i18n.rb b/middleman-core/lib/middleman-core/core_extensions/i18n.rb
index ac86d9a0..156f2694 100644
--- a/middleman-core/lib/middleman-core/core_extensions/i18n.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/i18n.rb
@@ -213,6 +213,8 @@ class Middleman::CoreExtensions::Internationalization < ::Middleman::Extension
   def on_file_changed(_updated_files, _removed_files)
     ::I18n.load_path |= app.files.by_type(:locales).files.map { |p| p[:full_path].to_s }
     ::I18n.reload!
+
+    @app.sitemap.rebuild_resource_list!(:touched_locale_file)
   end
 
   def configure_i18n
diff --git a/middleman-core/lib/middleman-core/extension.rb b/middleman-core/lib/middleman-core/extension.rb
index d9dc01ca..8f342e69 100644
--- a/middleman-core/lib/middleman-core/extension.rb
+++ b/middleman-core/lib/middleman-core/extension.rb
@@ -490,15 +490,14 @@ module Middleman
   class ConfigExtension < Extension
     def initialize(app, config={}, &block)
       @descriptors = {}
-      @wrapped = {}
+      @ready = false
 
       self.class.exposed_to_config.each do |k, v|
         @descriptors[k] = []
 
         define_singleton_method(:"__original_#{v}", &method(v))
         define_singleton_method(v) do |*args, &b|
-          @descriptors[k] << method(:"__original_#{v}").call(*args, &b)
-          @app.sitemap.rebuild_resource_list!(:"first_run_change_#{v}")
+          proxy_method_call(k, v, args, &b)
         end
       end
 
@@ -506,11 +505,24 @@ module Middleman
     end
 
     def after_configuration
+      context = self
+
       self.class.exposed_to_config.each do |k, v|
-        ::Middleman::CoreExtensions::Collections::StepContext.add_to_context(k, &method(:"__original_#{v}"))
+        ::Middleman::CoreExtensions::Collections::StepContext.add_to_context(k) do |*args, &b|
+          r = context.method(:"__original_#{v}").call(*args, &b)
+          self.descriptors << r if r.respond_to?(:execute_descriptor)
+        end
       end
     end
 
+    def ready
+      @ready = true
+
+      # @descriptors.each do |k, v|
+      #   @descriptors[k] = []
+      # end
+    end
+
     # Update the main sitemap resource list
     # @return Array<Middleman::Sitemap::Resource>
     Contract ResourceList => ResourceList
@@ -519,5 +531,25 @@ module Middleman
         c.execute_descriptor(app, sum)
       end
     end
+
+    Contract Symbol, Symbol, ArrayOf[Any], Maybe[Proc] => Any
+    def proxy_method_call(k, v, args, &b)
+      if @ready
+        ctx = ::Middleman::CoreExtensions::Collections::StepContext.current
+        r = method(:"__original_#{v}").call(*args, &b)
+
+        if r.respond_to?(:execute_descriptor)
+          if ctx
+            ctx.descriptors << r
+          else
+            @descriptors[k] << r
+            @app.sitemap.rebuild_resource_list!(:"first_run_change_#{v}")
+          end
+        end
+      else
+        @descriptors[k] << method(:"__original_#{v}").call(*args, &b)
+        @app.sitemap.rebuild_resource_list!(:"first_run_change_#{v}")
+      end
+    end
   end
 end