fix error with login_credentials when config is enabled

gems/aws-sdk-core/CHANGELOG.md

@@ -1,6 +1,8 @@
 Unreleased Changes
 ------------------
 
+* Issue - Fix `login_credentials` in credentials chain when config is enabled.
+
 3.239.1 (2025-11-21)
 ------------------
 

gems/aws-sdk-core/lib/aws-sdk-core/credential_provider_chain.rb

@@ -173,7 +173,8 @@ def login_credentials(options)
       return unless Aws.shared_config.config_enabled?
 
       profile_name = determine_profile_name(options)
-      Aws.shared_config.login_credentials_from_config(profile: profile_name, region: options[:config].region)
+      region = options[:config].region if options[:config]
+      Aws.shared_config.login_credentials_from_config(profile: profile_name, region: region)
     rescue Errors::NoSuchProfileError
       nil
     end

gems/aws-sdk-core/spec/aws/credential_provider_chain_spec.rb

@@ -169,6 +169,11 @@ def validate_metrics(*expected_metrics)
       it 'defaults to nil' do
         expect(credentials).to be(nil)
       end
+
+      it 'defaults to nil when config is enabled' do
+        Aws.shared_config.fresh(config_enabled: true)
+        expect(credentials).to be(nil)
+      end
     end
 
     describe 'with shared credentials' do