diff --git a/lib/tapioca/dsl/compiler.rb b/lib/tapioca/dsl/compiler.rb
index fbe33fcea..5cac1d9a6 100644
--- a/lib/tapioca/dsl/compiler.rb
+++ b/lib/tapioca/dsl/compiler.rb
@@ -74,9 +74,21 @@ def all_modules
           @all_modules ||= if @@requested_constants.any?
             @@requested_constants.grep(Module)
           else
-            ObjectSpace.each_object(Module).to_a
+            ObjectSpace.each_object(Module).reject { |mod| deprecated_constant_proxy?(mod) }.to_a
           end.freeze #: Enumerable[Module[top]]?
         end
+
+        # Rails 8.1+ wraps deprecated constants in DeprecatedConstantProxy, which
+        # undefines most instance methods and warns from method_missing. Inspecting
+        # those modules during DSL discovery (is_a?, singleton_class, etc.) emits
+        # deprecation warnings even though Tapioca is only enumerating ObjectSpace.
+        # class_of uses Kernel#class so we can recognize the proxy without warning.
+        #: (Module[top] mod) -> bool
+        def deprecated_constant_proxy?(mod)
+          proxy_class_name = name_of(class_of(mod))
+          proxy_class_name == "ActiveSupport::Deprecation::DeprecatedConstantProxy" ||
+            proxy_class_name == "ActiveSupport::DeprecatedConstantProxy"
+        end
       end
 
       #: (
diff --git a/spec/tapioca/dsl/compilers/active_support_concern_spec.rb b/spec/tapioca/dsl/compilers/active_support_concern_spec.rb
index 2b46844e5..3e1c3b3dc 100644
--- a/spec/tapioca/dsl/compilers/active_support_concern_spec.rb
+++ b/spec/tapioca/dsl/compilers/active_support_concern_spec.rb
@@ -14,6 +14,29 @@ def before_setup
           end
 
           describe "gather_constants" do
+            it "does not gather ActiveSupport deprecation proxies and does not warn" do
+              warnings = []
+              previous_behavior = ActiveSupport.deprecator.behavior
+              ActiveSupport.deprecator.behavior = ->(message, *) { warnings << message.to_s }
+
+              begin
+                proxy = ActiveSupport::Deprecation::DeprecatedConstantProxy.new(
+                  "FakeDeprecatedConstant",
+                  "Module",
+                  ActiveSupport.deprecator,
+                )
+                # Name the proxy so discovery can trigger its warning.
+                ActiveSupportConcernSpec.const_set(:FakeDeprecatedConstant, proxy)
+                gathered_constants
+                all_modules = Tapioca::Dsl::Compilers::ActiveSupportConcern.send(:all_modules)
+              ensure
+                ActiveSupport.deprecator.behavior = previous_behavior
+              end
+
+              refute(all_modules.any? { |mod| Tapioca::Runtime::Reflection.are_equal?(mod, proxy) })
+              assert_empty(warnings.grep(/FakeDeprecatedConstant/))
+            end
+
             it "does not gather anonymous constants" do
               add_ruby_file("test_case.rb", <<~RUBY)
                 module TestCase