Compute authenticatable_name once per strategy class

CHANGELOG.md

@@ -1,3 +1,8 @@
+### Unreleased
+
+* enhancements
+  * Compute each strategy's `authenticatable_name` once per strategy class instead of on every request: Warden builds new strategy instances per request, so the per-instance memo never hit.
+
 ### 5.0.4 - 2026-05-08
 
 * security fixes

lib/devise/strategies/authenticatable.rb

@@ -169,8 +169,14 @@ def parse_authentication_key_values(hash, keys)
       # Holds the authenticatable name for this class. Devise::Strategies::DatabaseAuthenticatable
       # becomes simply :database.
       def authenticatable_name
+        @authenticatable_name ||= self.class.authenticatable_name
+      end
+
+      # Computed once per strategy class: Warden builds new strategy
+      # instances on every request.
+      def self.authenticatable_name
         @authenticatable_name ||=
-          ActiveSupport::Inflector.underscore(self.class.name.split("::").last).
+          ActiveSupport::Inflector.underscore(name.split("::").last).
             sub("_authenticatable", "").to_sym
       end
     end

test/strategies/authenticatable_test.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+require 'devise/strategies/database_authenticatable'
+require 'devise/strategies/rememberable'
+
+class AuthenticatableStrategyTest < ActiveSupport::TestCase
+  test 'authenticatable_name comes from the strategy class name' do
+    assert_equal :database, Devise::Strategies::DatabaseAuthenticatable.authenticatable_name
+    assert_equal :rememberable, Devise::Strategies::Rememberable.authenticatable_name
+    assert_equal :database, Devise::Strategies::DatabaseAuthenticatable.new({}).send(:authenticatable_name)
+  end
+
+  test 'authenticatable_name is computed once per strategy class, not per instance' do
+    Devise::Strategies::DatabaseAuthenticatable.authenticatable_name
+    ActiveSupport::Inflector.expects(:underscore).never
+    2.times { Devise::Strategies::DatabaseAuthenticatable.new({}).send(:authenticatable_name) }
+  end
+end