diff --git a/Gemfile.lock b/Gemfile.lock
index 94b820f..2a5e580 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    rails-app_env (0.2.0)
+    rails-app_env (0.3.0)
       activesupport (>= 8.0.0)
       railties (>= 8.0.0)
 
diff --git a/lib/rails/app_env.rb b/lib/rails/app_env.rb
index ab51c6c..1dc55bc 100644
--- a/lib/rails/app_env.rb
+++ b/lib/rails/app_env.rb
@@ -1,13 +1,18 @@
 require_relative "app_env/version"
+
+require_relative "app_env/error"
+
+require_relative "app_env/console"
+require_relative "app_env/credentials"
+require_relative "app_env/environment_inquirer"
+
+require_relative "app_env/extensions/rails/app_env_aware"
+require_relative "app_env/extensions/credentials_command/original_aware"
+require_relative "app_env/extensions/application/app_configurable"
+
 require_relative "app_env/railtie"
 
 module Rails
   module AppEnv
-    autoload :ApplicationHelpers, "rails/app_env/application_helpers"
-    autoload :Console, "rails/app_env/console"
-    autoload :Credentials, "rails/app_env/credentials"
-    autoload :EnvironmentInquirer, "rails/app_env/environment_inquirer"
-    autoload :Error, "rails/app_env/error"
-    autoload :RailsHelpers, "rails/app_env/rails_helpers"
   end
 end
diff --git a/lib/rails/app_env/application_helpers.rb b/lib/rails/app_env/application_helpers.rb
deleted file mode 100644
index 791e2fd..0000000
--- a/lib/rails/app_env/application_helpers.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-module Rails
-  module AppEnv
-    module ApplicationHelpers
-      def app_config_for(name)
-        config_for(name, env: Rails.app_env)
-      end
-    end
-  end
-end
diff --git a/lib/rails/app_env/credentials.rb b/lib/rails/app_env/credentials.rb
index c8aa659..37aee64 100644
--- a/lib/rails/app_env/credentials.rb
+++ b/lib/rails/app_env/credentials.rb
@@ -38,7 +38,8 @@ def key_path
         end
 
         def monkey_patch_rails_credentials_command!
-          require_relative "../rails_ext/credentials_command"
+          return unless defined?(Rails::Command::CredentialsCommand)
+          Rails::Command::CredentialsCommand.extend(Extensions::OriginalAware)
         end
       end
     end
diff --git a/lib/rails/app_env/extensions/application/app_configurable.rb b/lib/rails/app_env/extensions/application/app_configurable.rb
new file mode 100644
index 0000000..0ef2cfb
--- /dev/null
+++ b/lib/rails/app_env/extensions/application/app_configurable.rb
@@ -0,0 +1,9 @@
+module Rails::AppEnv::Extensions
+  module AppConfigurable
+    extend self
+
+    def app_config_for(name)
+      Rails.application.config_for(name, env: Rails.app_env)
+    end
+  end
+end
diff --git a/lib/rails/app_env/extensions/credentials_command/original_aware.rb b/lib/rails/app_env/extensions/credentials_command/original_aware.rb
new file mode 100644
index 0000000..b3024e7
--- /dev/null
+++ b/lib/rails/app_env/extensions/credentials_command/original_aware.rb
@@ -0,0 +1,9 @@
+module Rails::AppEnv::Extensions
+  module OriginalAware
+    private
+
+    def config
+      Rails::AppEnv::Credentials.original
+    end
+  end
+end
diff --git a/lib/rails/app_env/extensions/rails/app_env_aware.rb b/lib/rails/app_env/extensions/rails/app_env_aware.rb
new file mode 100644
index 0000000..7914ebd
--- /dev/null
+++ b/lib/rails/app_env/extensions/rails/app_env_aware.rb
@@ -0,0 +1,13 @@
+module Rails
+  module AppEnv
+    module Extensions
+      module AppEnvAware
+        extend self
+
+        def app_env
+          @_app_env ||= EnvironmentInquirer.new(ENV["APP_ENV"] || Rails.env)
+        end
+      end
+    end
+  end
+end
diff --git a/lib/rails/app_env/rails_helpers.rb b/lib/rails/app_env/rails_helpers.rb
deleted file mode 100644
index 216357c..0000000
--- a/lib/rails/app_env/rails_helpers.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-module Rails
-  module AppEnv
-    module RailsHelpers
-      def app_env
-        @_app_env ||= EnvironmentInquirer.new(ENV["APP_ENV"] || Rails.env)
-      end
-    end
-  end
-end
diff --git a/lib/rails/app_env/railtie.rb b/lib/rails/app_env/railtie.rb
index c7431c0..9282f8a 100644
--- a/lib/rails/app_env/railtie.rb
+++ b/lib/rails/app_env/railtie.rb
@@ -2,8 +2,8 @@ module Rails
   module AppEnv
     class Railtie < Rails::Railtie
       config.before_configuration do
-        Rails.extend(RailsHelpers)
-        Rails.application.extend(ApplicationHelpers)
+        Rails.extend(Extensions::AppEnvAware)
+        Rails.application.extend(Extensions::AppConfigurable)
       end
 
       config.before_configuration do
diff --git a/lib/rails/app_env/version.rb b/lib/rails/app_env/version.rb
index 789ca48..763029a 100644
--- a/lib/rails/app_env/version.rb
+++ b/lib/rails/app_env/version.rb
@@ -1,5 +1,5 @@
 module Rails
   module AppEnv
-    VERSION = "0.2.0"
+    VERSION = "0.3.0"
   end
 end
diff --git a/lib/rails/rails_ext/credentials_command.rb b/lib/rails/rails_ext/credentials_command.rb
deleted file mode 100644
index b48b3b0..0000000
--- a/lib/rails/rails_ext/credentials_command.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-module Rails
-  module Command
-    class CredentialsCommand
-      private
-
-      def config
-        Rails::AppEnv::Credentials.original
-      end
-    end
-  end
-end
diff --git a/test/units/app_env/console_test.rb b/test/units/app_env/console_test.rb
index 34662de..a9d3e1e 100644
--- a/test/units/app_env/console_test.rb
+++ b/test/units/app_env/console_test.rb
@@ -2,50 +2,52 @@
 require_relative "../../test_helper"
 require "rails/commands/console/irb_console"
 
-class Rails::AppEnv::ConsoleTest < ActiveSupport::TestCase
-  test "Rails::AppEnv::Console is a kind of Rails::Console::IRBConsole" do
-    assert_kind_of Rails::Console::IRBConsole, Rails::AppEnv::Console.new(nil)
-  end
+module Rails::AppEnv
+  class ConsoleTest < ActiveSupport::TestCase
+    test "Rails::AppEnv::Console is a kind of Rails::Console::IRBConsole" do
+      assert_kind_of Rails::Console::IRBConsole, Rails::AppEnv::Console.new(nil)
+    end
 
-  test "Console#colorized_env prints Rails.env only when Rails.app_env is same as Rails.env" do
-    Rails.stub :app_env, "foo" do
-      Rails.stub :env, "foo" do
-        console = Rails::AppEnv::Console.new(nil)
-        assert_equal_without_color "foo", console.colorized_env
+    test "#colorized_env prints Rails.env only when Rails.app_env is same as Rails.env" do
+      Rails.stub :app_env, "foo" do
+        Rails.stub :env, "foo" do
+          console = Console.new(nil)
+          assert_equal_without_color "foo", console.colorized_env
+        end
       end
     end
-  end
 
-  test "Console#colorized_env prints {Rails.env:Rails.app_env} when Rails.app_env is diff from Rails.env" do
-    Rails.stub :app_env, "foo" do
-      Rails.stub :env, "bar" do
-        console = Rails::AppEnv::Console.new(nil)
-        assert_equal_without_color "bar:foo", console.colorized_env
+    test "#colorized_env prints {Rails.env:Rails.app_env} when Rails.app_env is diff from Rails.env" do
+      Rails.stub :app_env, "foo" do
+        Rails.stub :env, "bar" do
+          console = Console.new(nil)
+          assert_equal_without_color "bar:foo", console.colorized_env
+        end
       end
     end
-  end
 
-  test "Console#colorized_env shorten Rails.app_env to dev when Rails.app_env is production" do
-    Rails.stub :app_env, "production" do
-      Rails.stub :env, "bar" do
-        console = Rails::AppEnv::Console.new(nil)
-        assert_equal_without_color "bar:prod", console.colorized_env
+    test "#colorized_env shorten Rails.app_env to prod when Rails.app_env is production" do
+      Rails.stub :app_env, "production" do
+        Rails.stub :env, "bar" do
+          console = Console.new(nil)
+          assert_equal_without_color "bar:prod", console.colorized_env
+        end
       end
     end
-  end
 
-  test "Console#colorized_env shorten Rails.app_env to dev when Rails.app_env is development" do
-    Rails.stub :app_env, "development" do
-      Rails.stub :env, "bar" do
-        console = Rails::AppEnv::Console.new(nil)
-        assert_equal_without_color "bar:dev", console.colorized_env
+    test "#colorized_env shorten Rails.app_env to dev when Rails.app_env is development" do
+      Rails.stub :app_env, "development" do
+        Rails.stub :env, "bar" do
+          console = Console.new(nil)
+          assert_equal_without_color "bar:dev", console.colorized_env
+        end
       end
     end
-  end
 
-  private
+    private
 
-  def assert_equal_without_color(expected, actual)
-    assert_equal expected, actual.gsub(/\e\[(\d+)(;\d+)*m/, "")
+    def assert_equal_without_color(expected, actual)
+      assert_equal expected, actual.gsub(/\e\[(\d+)(;\d+)*m/, "")
+    end
   end
 end
diff --git a/test/units/app_env/credentials_test.rb b/test/units/app_env/credentials_test.rb
index 5e1b971..76158c2 100644
--- a/test/units/app_env/credentials_test.rb
+++ b/test/units/app_env/credentials_test.rb
@@ -1,95 +1,97 @@
 require "minitest/mock"
 require_relative "../../test_helper"
 
-class Rails::AppEnv::CredentialsTest < ActiveSupport::TestCase
-  test "Rails::AppEnv::Credentials::AlreadyInitializedError is a kind of Rails::AppEnv::Error" do
-    assert_kind_of Rails::AppEnv::Error, Rails::AppEnv::Credentials::AlreadyInitializedError.new
-  end
+module Rails::AppEnv
+  class CredentialsTest < ActiveSupport::TestCase
+    test "Rails::AppEnv::Credentials::AlreadyInitializedError is a kind of Rails::AppEnv::Error" do
+      assert_kind_of Rails::AppEnv::Error, Rails::AppEnv::Credentials::AlreadyInitializedError.new
+    end
 
-  test "#initialize! can only be invoked once" do
-    reset_credentials
+    test ".initialize! can only be invoked once" do
+      reset_credentials
 
-    Rails::AppEnv::Credentials.initialize!
+      Credentials.initialize!
 
-    assert_raises Rails::AppEnv::Credentials::AlreadyInitializedError do
-      Rails::AppEnv::Credentials.initialize!
+      assert_raises Rails::AppEnv::Credentials::AlreadyInitializedError do
+        Credentials.initialize!
+      end
     end
-  end
 
-  test "#initialize! backup original Rails.application.config.credentials" do
-    reset_credentials
+    test ".initialize! backup original Rails.application.config.credentials" do
+      reset_credentials
 
-    expected = Object.new
+      expected = Object.new
 
-    Rails.application.config.stub :credentials, expected do
-      Rails::AppEnv::Credentials.initialize!
-    end
+      Rails.application.config.stub :credentials, expected do
+        Credentials.initialize!
+      end
 
-    assert_same expected, Rails::AppEnv::Credentials.original
-  end
+      assert_same expected, Credentials.original
+    end
 
-  test "#configuration is a kind of ActiveSupport::Credentials" do
-    assert_kind_of ActiveSupport::InheritableOptions, Rails::AppEnv::Credentials.configuration
-  end
+    test ".configuration is a kind of ActiveSupport::Credentials" do
+      assert_kind_of ActiveSupport::InheritableOptions, Credentials.configuration
+    end
 
-  test "#configuration.content_path is config/credentials/{Rails.app_env}.yml.enc" do
-    Dir.mktmpdir do |tmp_dir|
-      Rails.stub :root, Pathname(tmp_dir) do
-        Rails.stub :app_env, Rails::AppEnv::EnvironmentInquirer.new("foo") do
-          path = Rails.root.join("config/credentials/foo.yml.enc")
+    test ".configuration.content_path is config/credentials/{Rails.app_env}.yml.enc" do
+      Dir.mktmpdir do |tmp_dir|
+        Rails.stub :root, Pathname(tmp_dir) do
+          Rails.stub :app_env, EnvironmentInquirer.new("foo") do
+            path = Rails.root.join("config/credentials/foo.yml.enc")
 
-          FileUtils.mkdir_p File.dirname(path)
-          FileUtils.touch path
+            FileUtils.mkdir_p File.dirname(path)
+            FileUtils.touch path
 
-          assert_equal path, Rails::AppEnv::Credentials.configuration.content_path
+            assert_equal path, Credentials.configuration.content_path
+          end
         end
       end
     end
-  end
 
-  test "#configuration.content_path falls back to config/credentials.yml.enc when config/credentials/{Rails.app_env}.yml.enc not exist" do
-    Dir.mktmpdir do |tmp_dir|
-      Rails.stub :root, Pathname(tmp_dir) do
-        Rails.stub :app_env, Rails::AppEnv::EnvironmentInquirer.new("foo") do
-          path = Rails.root.join("config/credentials.yml.enc")
+    test ".configuration.content_path falls back to config/credentials.yml.enc when config/credentials/{Rails.app_env}.yml.enc not exist" do
+      Dir.mktmpdir do |tmp_dir|
+        Rails.stub :root, Pathname(tmp_dir) do
+          Rails.stub :app_env, EnvironmentInquirer.new("foo") do
+            path = Rails.root.join("config/credentials.yml.enc")
 
-          assert_equal path, Rails::AppEnv::Credentials.configuration.content_path
+            assert_equal path, Credentials.configuration.content_path
+          end
         end
       end
     end
-  end
 
-  test "#configuration.key_path is config/credentials/{APP_ENV}.key" do
-    Dir.mktmpdir do |tmp_dir|
-      Rails.stub :root, Pathname(tmp_dir) do
-        Rails.stub :app_env, Rails::AppEnv::EnvironmentInquirer.new("foo") do
-          path = Rails.root.join("config/credentials/foo.key")
+    test ".configuration.key_path is config/credentials/{APP_ENV}.key" do
+      Dir.mktmpdir do |tmp_dir|
+        Rails.stub :root, Pathname(tmp_dir) do
+          Rails.stub :app_env, EnvironmentInquirer.new("foo") do
+            path = Rails.root.join("config/credentials/foo.key")
 
-          FileUtils.mkdir_p File.dirname(path)
-          FileUtils.touch path
+            FileUtils.mkdir_p File.dirname(path)
+            FileUtils.touch path
 
-          assert_equal path, Rails::AppEnv::Credentials.configuration.key_path
+            assert_equal path, Credentials.configuration.key_path
+          end
         end
       end
     end
-  end
 
-  test "#configuration.key_path falls back to config/master.key when config/credentials/{APP_ENV}.key not exist" do
-    Dir.mktmpdir do |tmp_dir|
-      Rails.stub :root, Pathname(tmp_dir) do
-        Rails.stub :app_env, Rails::AppEnv::EnvironmentInquirer.new("foo") do
-          path = Rails.root.join("config/master.key")
+    test ".configuration.key_path falls back to config/master.key when config/credentials/{APP_ENV}.key not exist" do
+      Dir.mktmpdir do |tmp_dir|
+        Rails.stub :root, Pathname(tmp_dir) do
+          Rails.stub :app_env, EnvironmentInquirer.new("foo") do
+            path = Rails.root.join("config/master.key")
 
-          assert_equal path, Rails::AppEnv::Credentials.configuration.key_path
+            assert_equal path, Credentials.configuration.key_path
+          end
         end
       end
     end
-  end
 
-  private
+    private
 
-  def reset_credentials
-    Rails::AppEnv::Credentials.instance_variable_set :@initialized, nil
-    Rails::AppEnv::Credentials.instance_variable_set :@original, nil
+    def reset_credentials
+      Credentials.instance_variable_set :@initialized, nil
+      Credentials.instance_variable_set :@original, nil
+    end
   end
 end
diff --git a/test/units/app_env/environment_inquirer_test.rb b/test/units/app_env/environment_inquirer_test.rb
index 81f0326..ab12c23 100644
--- a/test/units/app_env/environment_inquirer_test.rb
+++ b/test/units/app_env/environment_inquirer_test.rb
@@ -1,31 +1,33 @@
 require_relative "../../test_helper"
 
-class Rails::AppEnv::EnvironmentInquirerTest < ActiveSupport::TestCase
-  test "EnvironmentInquirer is a kind of ActiveSupport::EnvironmentInquirer" do
-    assert_kind_of ActiveSupport::EnvironmentInquirer, Rails::AppEnv::EnvironmentInquirer.new("foo")
-  end
+module Rails::AppEnv
+  class EnvironmentInquirerTest < ActiveSupport::TestCase
+    test "EnvironmentInquirer is a kind of ActiveSupport::EnvironmentInquirer" do
+      assert_kind_of ActiveSupport::EnvironmentInquirer, Rails::AppEnv::EnvironmentInquirer.new("foo")
+    end
 
-  test "EnvironmentInquirer#production? is inherited" do
-    assert_includes Rails::AppEnv::EnvironmentInquirer.instance_methods, :production?
-  end
+    test "#production? is inherited" do
+      assert_includes EnvironmentInquirer.instance_methods, :production?
+    end
 
-  test "EnvironmentInquirer#staging? is defined" do
-    assert_includes Rails::AppEnv::EnvironmentInquirer.instance_methods, :staging?
-  end
+    test "#staging? is defined" do
+      assert_includes EnvironmentInquirer.instance_methods, :staging?
+    end
 
-  test "EnvironmentInquirer#review? is defined" do
-    assert_includes Rails::AppEnv::EnvironmentInquirer.instance_methods, :review?
-  end
+    test "#review? is defined" do
+      assert_includes EnvironmentInquirer.instance_methods, :review?
+    end
 
-  test "EnvironmentInquirer#staging?" do
-    assert_predicate Rails::AppEnv::EnvironmentInquirer.new("staging"), :staging?
-    refute_predicate Rails::AppEnv::EnvironmentInquirer.new("review"), :staging?
-    refute_predicate Rails::AppEnv::EnvironmentInquirer.new("production"), :staging?
-  end
+    test "#staging?" do
+      assert_predicate EnvironmentInquirer.new("staging"), :staging?
+      refute_predicate EnvironmentInquirer.new("review"), :staging?
+      refute_predicate EnvironmentInquirer.new("production"), :staging?
+    end
 
-  test "EnvironmentInquirer#review?" do
-    refute_predicate Rails::AppEnv::EnvironmentInquirer.new("staging"), :review?
-    assert_predicate Rails::AppEnv::EnvironmentInquirer.new("review"), :review?
-    refute_predicate Rails::AppEnv::EnvironmentInquirer.new("production"), :review?
+    test "#review?" do
+      refute_predicate EnvironmentInquirer.new("staging"), :review?
+      assert_predicate EnvironmentInquirer.new("review"), :review?
+      refute_predicate EnvironmentInquirer.new("production"), :review?
+    end
   end
 end
diff --git a/test/units/app_env/extensions/application/app_configurable_test.rb b/test/units/app_env/extensions/application/app_configurable_test.rb
new file mode 100644
index 0000000..88c3b42
--- /dev/null
+++ b/test/units/app_env/extensions/application/app_configurable_test.rb
@@ -0,0 +1,22 @@
+require "minitest/mock"
+require_relative "../../../../test_helper"
+
+module Rails::AppEnv::Extensions
+  class AppConfigurableTest < ActiveSupport::TestCase
+    test ".app_config_for delegates to Rails.application.config_for" do
+      app_env = "foo"
+      expected = Object.new
+
+      mock = Minitest::Mock.new
+      mock.expect(:call, expected, [:bar], env: app_env)
+
+      Rails.stub(:app_env, app_env) do
+        Rails.application.stub(:config_for, mock) do
+          assert_same expected, AppConfigurable.app_config_for(:bar)
+        end
+      end
+
+      mock.verify
+    end
+  end
+end
diff --git a/test/units/app_env/extensions/rails/app_env_aware_test.rb b/test/units/app_env/extensions/rails/app_env_aware_test.rb
new file mode 100644
index 0000000..a83e9ad
--- /dev/null
+++ b/test/units/app_env/extensions/rails/app_env_aware_test.rb
@@ -0,0 +1,47 @@
+require "minitest/mock"
+require_relative "../../../../test_helper"
+
+module Rails::AppEnv::Extensions
+  class AppEnvAwareTest < ActiveSupport::TestCase
+    def setup
+      AppEnvAware.instance_variable_set :@_app_env, nil
+    end
+
+    test ".app_env reads from APP_ENV" do
+      switch_env("APP_ENV", "foo") do
+        Rails.stub(:env, "bar") do
+          actual = AppEnvAware.app_env
+
+          assert_equal "foo", actual
+          assert_predicate actual, :foo?
+
+          refute_predicate actual, :bar?
+          refute_predicate actual, :test?
+        end
+      end
+    end
+
+    test ".app_env falls back to read from Rails.env" do
+      switch_env("APP_ENV", nil) do
+        Rails.stub(:env, "bar") do
+          actual = AppEnvAware.app_env
+
+          assert_equal "bar", actual
+          assert_predicate actual, :bar?
+
+          refute_predicate actual, :foo?
+          refute_predicate actual, :test?
+        end
+      end
+    end
+
+    private
+
+    def switch_env(key, value)
+      old, ENV[key] = ENV[key], value
+      yield
+    ensure
+      ENV[key] = old
+    end
+  end
+end