diff --git a/lib/tapioca/dsl/compilers/active_support_environment_inquirer.rb b/lib/tapioca/dsl/compilers/active_support_environment_inquirer.rb
new file mode 100644
index 000000000..d184e7006
--- /dev/null
+++ b/lib/tapioca/dsl/compilers/active_support_environment_inquirer.rb
@@ -0,0 +1,64 @@
+# typed: strict
+# frozen_string_literal: true
+
+return unless defined?(ActiveSupport::EnvironmentInquirer)
+
+module Tapioca
+  module Dsl
+    module Compilers
+      # `Tapioca::Dsl::Compilers::ActiveSupportEnvironmentInquirer` decorates an RBI file for non-default environment
+      # files in the `config/environments` directory.
+      #
+      # For example, in a Rails application with the following files:
+      #
+      # - config/environments/development.rb
+      # - config/environments/demo.rb
+      # - config/environments/production.rb
+      # - config/environments/staging.rb
+      # - config/environments/test.rb
+      #
+      # this compiler will produce an RBI file with the following content:
+      # ~~~rbi
+      # # typed: true
+      #
+      # class ActiveSupport::EnvironmentInquirer
+      #   sig { returns(T::Boolean) }
+      #   def demo?; end
+      #
+      #   sig { returns(T::Boolean) }
+      #   def staging?; end
+      # end
+      # ~~~
+      #: [ConstantType = singleton(::ActiveSupport::EnvironmentInquirer)]
+      class ActiveSupportEnvironmentInquirer < Compiler
+        extend T::Sig
+
+        # @override
+        #: -> void
+        def decorate
+          envs = Rails.root.glob("config/environments/*.rb").map { |f| f.basename(".rb").to_s }.sort
+          envs -= ::ActiveSupport::EnvironmentInquirer::DEFAULT_ENVIRONMENTS
+          return if envs.none?
+
+          root.create_path(::ActiveSupport::EnvironmentInquirer) do |mod|
+            envs.each do |env|
+              mod.create_method("#{env}?", return_type: "T::Boolean")
+            end
+          end
+        end
+
+        class << self
+          extend T::Sig
+
+          # @override
+          #: -> T::Enumerable[T::Module[top]]
+          def gather_constants
+            return [] unless defined?(Rails.application) && Rails.application
+
+            [::ActiveSupport::EnvironmentInquirer]
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/manual/compiler_activesupportenvironmentinquirer.md b/manual/compiler_activesupportenvironmentinquirer.md
new file mode 100644
index 000000000..ab1382a36
--- /dev/null
+++ b/manual/compiler_activesupportenvironmentinquirer.md
@@ -0,0 +1,25 @@
+## ActiveSupportEnvironmentInquirer
+
+`Tapioca::Dsl::Compilers::ActiveSupportEnvironmentInquirer` decorates an RBI file for non-default environment
+files in the `config/environments` directory.
+
+For example, in a Rails application with the following files:
+
+- config/environments/development.rb
+- config/environments/demo.rb
+- config/environments/production.rb
+- config/environments/staging.rb
+- config/environments/test.rb
+
+this compiler will produce an RBI file with the following content:
+~~~rbi
+# typed: true
+
+class ActiveSupport::EnvironmentInquirer
+  sig { returns(T::Boolean) }
+  def demo?; end
+
+  sig { returns(T::Boolean) }
+  def staging?; end
+end
+~~~
diff --git a/manual/compilers.md b/manual/compilers.md
index 2f2960b1b..74f68c0c5 100644
--- a/manual/compilers.md
+++ b/manual/compilers.md
@@ -25,6 +25,7 @@ In the following section you will find all available DSL compilers:
 * [ActiveStorage](compiler_activestorage.md)
 * [ActiveSupportConcern](compiler_activesupportconcern.md)
 * [ActiveSupportCurrentAttributes](compiler_activesupportcurrentattributes.md)
+* [ActiveSupportEnvironmentInquirer](compiler_activesupportenvironmentinquirer.md)
 * [ActiveSupportTimeExt](compiler_activesupporttimeext.md)
 * [Config](compiler_config.md)
 * [FrozenRecord](compiler_frozenrecord.md)
diff --git a/spec/rails_spec_helper.rb b/spec/rails_spec_helper.rb
index 82bdb0fa4..992b2d329 100644
--- a/spec/rails_spec_helper.rb
+++ b/spec/rails_spec_helper.rb
@@ -6,6 +6,15 @@ module RailsSpecHelper
     extend Tapioca::Helpers::Test::Content
 
     class << self
+      #: (String path) -> void
+      def define_fake_rails_app(path)
+        base_folder = Pathname.new(path)
+        config_class = Struct.new(:root)
+        config = config_class.new(base_folder)
+        app_class = Struct.new(:config)
+        Rails.application = app_class.new(config)
+      end
+
       def load_active_storage
         add_ruby_file("application.rb", <<~RUBY)
           ENV["DATABASE_URL"] = "sqlite3::memory:"
diff --git a/spec/tapioca/cli/dsl_spec.rb b/spec/tapioca/cli/dsl_spec.rb
index a019ec30f..909a437a1 100644
--- a/spec/tapioca/cli/dsl_spec.rb
+++ b/spec/tapioca/cli/dsl_spec.rb
@@ -2858,6 +2858,7 @@ class PostCompiler < Tapioca::Dsl::Compiler
               Tapioca::Dsl::Compilers::ActiveRecordStore                   enabled
               Tapioca::Dsl::Compilers::ActiveSupportConcern                enabled
               Tapioca::Dsl::Compilers::ActiveSupportCurrentAttributes      enabled
+              Tapioca::Dsl::Compilers::ActiveSupportEnvironmentInquirer    enabled
               Tapioca::Dsl::Compilers::MixedInClassAttributes              enabled
               Tapioca::Dsl::Compilers::SidekiqWorker                       enabled
               Tapioca::Dsl::Compilers::SmartProperties                     enabled
@@ -2893,6 +2894,7 @@ class PostCompiler < Tapioca::Dsl::Compiler
               Tapioca::Dsl::Compilers::ActiveRecordStore                   enabled
               Tapioca::Dsl::Compilers::ActiveSupportConcern                enabled
               Tapioca::Dsl::Compilers::ActiveSupportCurrentAttributes      enabled
+              Tapioca::Dsl::Compilers::ActiveSupportEnvironmentInquirer    enabled
               Tapioca::Dsl::Compilers::MixedInClassAttributes              enabled
               Tapioca::Dsl::Compilers::SidekiqWorker                       enabled
               Tapioca::Dsl::Compilers::SmartProperties                     disabled
@@ -2928,6 +2930,7 @@ class PostCompiler < Tapioca::Dsl::Compiler
               Tapioca::Dsl::Compilers::ActiveRecordStore                   disabled
               Tapioca::Dsl::Compilers::ActiveSupportConcern                disabled
               Tapioca::Dsl::Compilers::ActiveSupportCurrentAttributes      disabled
+              Tapioca::Dsl::Compilers::ActiveSupportEnvironmentInquirer    disabled
               Tapioca::Dsl::Compilers::MixedInClassAttributes              disabled
               Tapioca::Dsl::Compilers::SidekiqWorker                       disabled
               Tapioca::Dsl::Compilers::SmartProperties                     enabled
diff --git a/spec/tapioca/dsl/compilers/active_record_fixtures_spec.rb b/spec/tapioca/dsl/compilers/active_record_fixtures_spec.rb
index 1fff0fea6..af311d073 100644
--- a/spec/tapioca/dsl/compilers/active_record_fixtures_spec.rb
+++ b/spec/tapioca/dsl/compilers/active_record_fixtures_spec.rb
@@ -32,7 +32,7 @@ class User
             before do
               require "rails"
 
-              define_fake_rails_app
+              Tapioca::RailsSpecHelper.define_fake_rails_app(tmp_path("lib"))
             end
 
             it "gathers only the ActiveSupport::TestCase base class" do
@@ -231,18 +231,6 @@ def posts(fixture_name = nil, *other_fixtures); end
             end
           end
         end
-
-        private
-
-        #: -> void
-        def define_fake_rails_app
-          base_folder = Pathname.new(tmp_path("lib"))
-
-          config_class = Struct.new(:root)
-          config = config_class.new(base_folder)
-          app_class = Struct.new(:config)
-          Rails.application = app_class.new(config)
-        end
       end
     end
   end
diff --git a/spec/tapioca/dsl/compilers/active_support_environment_inquirer_spec.rb b/spec/tapioca/dsl/compilers/active_support_environment_inquirer_spec.rb
new file mode 100644
index 000000000..73521ab4f
--- /dev/null
+++ b/spec/tapioca/dsl/compilers/active_support_environment_inquirer_spec.rb
@@ -0,0 +1,74 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "spec_helper"
+
+module Tapioca
+  module Dsl
+    module Compilers
+      class ActiveSupportEnvironmentInquirerSpec < ::DslSpec
+        describe "Tapioca::Dsl::Compilers::ActiveSupportEnvironmentInquirer" do
+          describe "without a Rails app" do
+            it "gathers nothing if not in a Rails application" do
+              add_default_environment_files
+
+              assert_empty(gathered_constants)
+            end
+          end
+
+          describe "with a Rails app" do
+            before do
+              require "rails"
+              Tapioca::RailsSpecHelper.define_fake_rails_app(tmp_path("lib"))
+              add_default_environment_files
+            end
+
+            describe "gather_constants" do
+              it "gathers only `ActiveSupport::EnvironmentInquirer` as a constant" do
+                assert_equal(["ActiveSupport::EnvironmentInquirer"], gathered_constants)
+              end
+            end
+
+            describe "decorate" do
+              it "generates nothing if there are only default environments" do
+                expected = <<~RBI
+                  # typed: strong
+                RBI
+
+                assert_equal(expected, rbi_for("ActiveSupport::EnvironmentInquirer"))
+              end
+
+              it "generates boolean predicate methods for non-default environments" do
+                add_content_file("config/environments/staging.rb", "")
+                add_content_file("config/environments/demo.rb", "")
+
+                expected = <<~RBI
+                  # typed: strong
+
+                  class ActiveSupport::EnvironmentInquirer
+                    sig { returns(T::Boolean) }
+                    def demo?; end
+
+                    sig { returns(T::Boolean) }
+                    def staging?; end
+                  end
+                RBI
+
+                assert_equal(expected, rbi_for("ActiveSupport::EnvironmentInquirer"))
+              end
+            end
+          end
+        end
+
+        private
+
+        #: -> void
+        def add_default_environment_files
+          add_content_file("config/environments/development.rb", "")
+          add_content_file("config/environments/test.rb", "")
+          add_content_file("config/environments/production.rb", "")
+        end
+      end
+    end
+  end
+end