diff --git a/middleman-cli/lib/middleman-cli/build.rb b/middleman-cli/lib/middleman-cli/build.rb
index 0ec5d234..737d70f8 100644
--- a/middleman-cli/lib/middleman-cli/build.rb
+++ b/middleman-cli/lib/middleman-cli/build.rb
@@ -60,7 +60,8 @@ module Middleman::Cli
 
       builder = Middleman::Builder.new(@app,
                                        glob: options['glob'],
-                                       clean: options['clean'])
+                                       clean: options['clean'],
+                                       parallel: options['parallel'])
 
       builder.on_build_event(&method(:on_event))
 
diff --git a/middleman-core/features/more-instance_vars.feature b/middleman-core/features/more-instance_vars.feature
deleted file mode 100644
index 87fc3b0d..00000000
--- a/middleman-core/features/more-instance_vars.feature
+++ /dev/null
@@ -1,18 +0,0 @@
-Feature: Instance Vars
-  In order to share data with layouts and partials via instance variables
-
-  Scenario: Setting an instance var in a template should be visible in its layout
-    Given the Server is running at "more-instance-vars-app"
-    When I go to "/instance-var-set.html"
-    Then I should see "Var is 100"
-
-  Scenario: Setting an instance var in a template should be visible in a partial
-    Given the Server is running at "more-instance-vars-app"
-    When I go to "/instance-var-set.html"
-    Then I should see "My var is here!"
-
-  Scenario: Setting an instance var in one file should not be visible in another
-    Given the Server is running at "more-instance-vars-app"
-    When I go to "/instance-var-set.html"
-    When I go to "/no-instance-var.html"
-    Then I should see "No var..."
diff --git a/middleman-core/features/partials.feature b/middleman-core/features/partials.feature
index 965215a9..86509027 100644
--- a/middleman-core/features/partials.feature
+++ b/middleman-core/features/partials.feature
@@ -11,11 +11,6 @@ Feature: Provide Sane Defaults for Partial Behavior
     When I go to "/sub/index.html"
     Then I should see "Header"
     And I should see "Footer"
-
-  Scenario: Finds shared partials without _ prefix
-    Given the Server is running at "partials-app"
-    When I go to "/using_snippet.html"
-    Then I should see "Snippet"
     
   Scenario: Prefers partials of the same engine type
     Given the Server is running at "partials-app"
diff --git a/middleman-core/fixtures/more-instance-vars-app/config.rb b/middleman-core/fixtures/more-instance-vars-app/config.rb
deleted file mode 100644
index e69de29b..00000000
diff --git a/middleman-core/fixtures/more-instance-vars-app/source/_vartial.erb b/middleman-core/fixtures/more-instance-vars-app/source/_vartial.erb
deleted file mode 100644
index cdf13355..00000000
--- a/middleman-core/fixtures/more-instance-vars-app/source/_vartial.erb
+++ /dev/null
@@ -1,5 +0,0 @@
-<% if @my_var %>
-  My var is here!
-<% else %>
-  No var...
-<% end %>
diff --git a/middleman-core/fixtures/more-instance-vars-app/source/instance-var-set.html.erb b/middleman-core/fixtures/more-instance-vars-app/source/instance-var-set.html.erb
deleted file mode 100644
index d785330f..00000000
--- a/middleman-core/fixtures/more-instance-vars-app/source/instance-var-set.html.erb
+++ /dev/null
@@ -1,2 +0,0 @@
-<% @my_var = 100 %>
-<%= partial 'vartial' %>
diff --git a/middleman-core/fixtures/more-instance-vars-app/source/layout.erb b/middleman-core/fixtures/more-instance-vars-app/source/layout.erb
deleted file mode 100644
index cbc7ac71..00000000
--- a/middleman-core/fixtures/more-instance-vars-app/source/layout.erb
+++ /dev/null
@@ -1,3 +0,0 @@
-Var is <%= @my_var %>
-
-<%= yield %>
\ No newline at end of file
diff --git a/middleman-core/fixtures/more-instance-vars-app/source/no-instance-var.html.erb b/middleman-core/fixtures/more-instance-vars-app/source/no-instance-var.html.erb
deleted file mode 100644
index bcb8a396..00000000
--- a/middleman-core/fixtures/more-instance-vars-app/source/no-instance-var.html.erb
+++ /dev/null
@@ -1 +0,0 @@
-<%= partial 'vartial' %>
diff --git a/middleman-core/lib/middleman-core/builder.rb b/middleman-core/lib/middleman-core/builder.rb
index 0e745ea7..c1f693b1 100644
--- a/middleman-core/lib/middleman-core/builder.rb
+++ b/middleman-core/lib/middleman-core/builder.rb
@@ -50,7 +50,9 @@ module Middleman
 
       queue_current_paths if @cleaning
       prerender_css
+
       output_files
+
       clean if @cleaning
 
       ::Middleman::Profiling.report('build')
diff --git a/middleman-core/lib/middleman-core/core_extensions/i18n.rb b/middleman-core/lib/middleman-core/core_extensions/i18n.rb
index 896ccf3f..0788c9fa 100644
--- a/middleman-core/lib/middleman-core/core_extensions/i18n.rb
+++ b/middleman-core/lib/middleman-core/core_extensions/i18n.rb
@@ -82,8 +82,7 @@ class Middleman::CoreExtensions::Internationalization < ::Middleman::Extension
 
     resources.each do |resource|
       # If it uses file extension localization
-      if parse_locale_extension(resource.path)
-        result = parse_locale_extension(resource.path)
+      if result = parse_locale_extension(resource.path)
         ext_lang, path, page_id = result
         new_resources << build_resource(path, resource.path, page_id, ext_lang)
       # If it's a "localizable template"
diff --git a/middleman-core/lib/middleman-core/sources.rb b/middleman-core/lib/middleman-core/sources.rb
index b8e11426..b8050b5f 100644
--- a/middleman-core/lib/middleman-core/sources.rb
+++ b/middleman-core/lib/middleman-core/sources.rb
@@ -156,7 +156,7 @@ module Middleman
     # @return [Array<Middleman::SourceFile>]
     Contract None => ArrayOf[SourceFile]
     def files
-      watchers.map(&:files).flatten.uniq { |f| f[:relative_path] }
+      watchers.flat_map(&:files).uniq { |f| f[:relative_path] }
     end
 
     # Find a file given a type and path.
@@ -168,9 +168,10 @@ module Middleman
     Contract Symbol, String, Maybe[Bool] => Maybe[SourceFile]
     def find(type, path, glob=false)
       watchers
+          .lazy
           .select { |d| d.type == type }
           .map { |d| d.find(path, glob) }
-          .compact
+          .reject { |d| d.nil? }
           .first
     end
 
@@ -182,6 +183,7 @@ module Middleman
     Contract Symbol, String => Bool
     def exists?(type, path)
       watchers
+          .lazy
           .select { |d| d.type == type }
           .any? { |d| d.exists?(path) }
     end
@@ -194,6 +196,7 @@ module Middleman
     Contract Symbol, String => Maybe[HANDLER]
     def watcher_for_path(type, path)
       watchers
+          .lazy
           .select { |d| d.type == type }
           .find { |d| d.exists?(path) }
     end
diff --git a/middleman-core/lib/middleman-core/sources/source_watcher.rb b/middleman-core/lib/middleman-core/sources/source_watcher.rb
index e50a2aac..9fb05475 100644
--- a/middleman-core/lib/middleman-core/sources/source_watcher.rb
+++ b/middleman-core/lib/middleman-core/sources/source_watcher.rb
@@ -43,6 +43,7 @@ module Middleman
       @directory = Pathname(directory)
 
       @files = {}
+      @extensionless_files = {}
 
       @validator = options.fetch(:validator, proc { true })
       @ignored = options.fetch(:ignored, proc { false })
@@ -105,8 +106,7 @@ module Middleman
       p = @directory + p if p.relative?
 
       if glob
-        found = @files.find { |_, v| v[:relative_path].fnmatch(path) }
-        found ? found.last : nil
+        @extensionless_files[p]
       else
         @files[p]
       end
@@ -215,7 +215,7 @@ module Middleman
           .select(&method(:valid?))
 
       valid_updates.each do |f|
-        @files[f[:full_path]] = f
+        add_file_to_cache(f)
         logger.debug "== Change (#{f[:type]}): #{f[:relative_path]}"
       end
 
@@ -225,13 +225,23 @@ module Middleman
           .select(&method(:valid?))
 
       valid_removes.each do |f|
-        @files.delete(f[:full_path])
+        remove_file_from_cache(f)
         logger.debug "== Deletion (#{f[:type]}): #{f[:relative_path]}"
       end
 
       run_callbacks(@on_change_callbacks, valid_updates, valid_removes) unless valid_updates.empty? && valid_removes.empty?
     end
 
+    def add_file_to_cache(f)
+      @files[f[:full_path]] = f
+      @extensionless_files[f[:full_path].sub_ext('.*')] = f
+    end
+
+    def remove_file_from_cache(f)
+      @files.delete(f[:full_path])
+      @extensionless_files.delete(f[:full_path].sub_ext('.*'))
+    end
+
     # Check if this watcher should care about a file.
     #
     # @param [Middleman::SourceFile] file The file.
diff --git a/middleman-core/lib/middleman-core/template_context.rb b/middleman-core/lib/middleman-core/template_context.rb
index 7012e6f9..3021b41e 100644
--- a/middleman-core/lib/middleman-core/template_context.rb
+++ b/middleman-core/lib/middleman-core/template_context.rb
@@ -102,6 +102,7 @@ module Middleman
 
       partial_file = locate_partial(name)
 
+      return "" unless partial_file
       raise ::Middleman::TemplateRenderer::TemplateNotFound, "Could not locate partial: #{name}" unless partial_file
 
       source_path = sitemap.file_to_path(partial_file)
diff --git a/middleman-core/lib/middleman-core/template_renderer.rb b/middleman-core/lib/middleman-core/template_renderer.rb
index dc7e1a77..9da1fae4 100644
--- a/middleman-core/lib/middleman-core/template_renderer.rb
+++ b/middleman-core/lib/middleman-core/template_renderer.rb
@@ -9,11 +9,24 @@ module Middleman
     extend Forwardable
     include Contracts
 
-    def self.cache
-      @_cache ||= ::Tilt::Cache.new
+    class Cache
+      def initialize
+        @cache = {}
+      end
+
+      def fetch(*key)
+        @cache[key] = yield unless @cache.key?(key)
+        @cache[key]
+      end
+
+      def clear
+        @cache = {}
+      end
     end
 
-    def_delegator :"self.class", :cache
+    def self.cache
+      @_cache ||= Cache.new
+    end
 
     # Custom error class for handling
     class TemplateNotFound < RuntimeError; end
@@ -163,21 +176,9 @@ module Middleman
     # @return [String, Boolean] Either the path to the template, or false
     Contract IsA['Middleman::Application'], Or[Symbol, String], Maybe[Hash] => Maybe[IsA['Middleman::SourceFile']]
     def self.resolve_template(app, request_path, options={})
-      # Find the path by searching or using the cache
+      # Find the path by searching
       relative_path = Util.strip_leading_slash(request_path.to_s)
 
-      # Cache lookups in build mode only
-      if app.build?
-        cache.fetch(:resolve_template, relative_path, options) do
-          uncached_resolve_template(app, relative_path, options)
-        end
-      else
-        uncached_resolve_template(app, relative_path, options)
-      end
-    end
-
-    Contract IsA['Middleman::Application'], String, Hash => Maybe[IsA['Middleman::SourceFile']]
-    def self.uncached_resolve_template(app, relative_path, options)
       # By default, any engine will do
       preferred_engines = []
 
@@ -200,7 +201,16 @@ module Middleman
         path_with_ext = relative_path.dup
         path_with_ext << ('.' + preferred_engine) unless preferred_engine.nil?
 
-        file = app.files.find(:source, path_with_ext, preferred_engine == '*')
+        globbing = preferred_engine == '*'
+
+        # Cache lookups in build mode only
+        file = if app.build?
+          cache.fetch(path_with_ext, preferred_engine) do
+            app.files.find(:source, path_with_ext, globbing)
+          end
+        else
+          app.files.find(:source, path_with_ext, globbing)
+        end
 
         found_template = file if file && (preferred_engine.nil? || ::Tilt[file[:full_path]])
         break if found_template