diff --git a/build_tools/services.rb b/build_tools/services.rb
index 8bf91b2eb42..a78ed7ce825 100644
--- a/build_tools/services.rb
+++ b/build_tools/services.rb
@@ -9,10 +9,10 @@ class ServiceEnumerator
     MANIFEST_PATH = File.expand_path('../../services.json', __FILE__)
 
     # Minimum `aws-sdk-core` version for new gem builds
-    MINIMUM_CORE_VERSION = "3.244.0"
+    MINIMUM_CORE_VERSION = "3.247.0"
 
     # Minimum `aws-sdk-core` version for new S3 gem builds
-    MINIMUM_CORE_VERSION_S3 = "3.244.0"
+    MINIMUM_CORE_VERSION_S3 = "3.247.0"
 
     EVENTSTREAM_PLUGIN = "Aws::Plugins::EventStreamConfiguration"
 
diff --git a/gems/aws-sdk-core/CHANGELOG.md b/gems/aws-sdk-core/CHANGELOG.md
index 161ec602f37..a1259ea6a31 100644
--- a/gems/aws-sdk-core/CHANGELOG.md
+++ b/gems/aws-sdk-core/CHANGELOG.md
@@ -1,5 +1,6 @@
 Unreleased Changes
 ------------------
+* Feature - Add YJIT & ZJIT tracking to user agent.
 
 3.246.0 (2026-04-23)
 ------------------
diff --git a/gems/aws-sdk-core/lib/aws-sdk-core/plugins/user_agent.rb b/gems/aws-sdk-core/lib/aws-sdk-core/plugins/user_agent.rb
index c5792f666ce..7bd7546338f 100644
--- a/gems/aws-sdk-core/lib/aws-sdk-core/plugins/user_agent.rb
+++ b/gems/aws-sdk-core/lib/aws-sdk-core/plugins/user_agent.rb
@@ -171,7 +171,16 @@ def os_metadata
 
           # Used to be RUBY_ENGINE/RUBY_VERSION
           def language_metadata
-            "lang/#{RUBY_ENGINE}##{RUBY_ENGINE_VERSION} md/#{RUBY_VERSION}"
+            metadata = "lang/#{RUBY_ENGINE}##{RUBY_ENGINE_VERSION} md/#{RUBY_VERSION}"
+            return metadata unless RUBY_ENGINE == 'ruby'
+
+            %i[YJIT ZJIT].each do |jit|
+              next unless RubyVM.const_defined?(jit)
+
+              mode = RubyVM.const_get(jit)
+              metadata += " md/#{jit.to_s.downcase}" if mode.respond_to?(:enabled?) && mode.enabled?
+            end
+            metadata
           end
 
           def env_metadata
diff --git a/gems/aws-sdk-core/spec/aws/plugins/user_agent_spec.rb b/gems/aws-sdk-core/spec/aws/plugins/user_agent_spec.rb
index 18063f600fb..ab7fc1fc6ec 100644
--- a/gems/aws-sdk-core/spec/aws/plugins/user_agent_spec.rb
+++ b/gems/aws-sdk-core/spec/aws/plugins/user_agent_spec.rb
@@ -89,6 +89,66 @@ def assert_header(expected, actual)
         end
       end
 
+      def stub_jit(name, enabled:)
+        if enabled
+          jit_module = double(enabled?: true)
+          stub_const("RubyVM::#{name}", jit_module)
+        else
+          hide_const("RubyVM::#{name}")
+        end
+      end
+
+      # Added tests manually instead of modifying cross-SDK test JSON since JIT info is specific to Ruby.
+      context 'JIT metadata' do
+        before do
+          allow(RbConfig::CONFIG).to receive(:[]).with('host_os').and_return('linux')
+          allow(RbConfig::CONFIG).to receive(:[]).with('host_cpu').and_return('x86_64')
+          allow(Gem::Platform).to receive(:local).and_return(double(version: '1.0'))
+        end
+
+        def user_agent_for(client)
+          resp = client.example_operation
+          resp.context.http_request.headers['User-Agent']
+        end
+
+        it 'includes md/yjit when YJIT is enabled', skip: (RUBY_ENGINE != 'ruby') do
+          stub_jit(:YJIT, enabled: true)
+          stub_jit(:ZJIT, enabled: false)
+
+          expect(user_agent_for(client)).to include('md/yjit')
+          expect(user_agent_for(client)).not_to include('md/zjit')
+        end
+
+        it 'includes md/zjit when ZJIT is enabled', skip: (RUBY_ENGINE != 'ruby') do
+          stub_jit(:YJIT, enabled: false)
+          stub_jit(:ZJIT, enabled: true)
+
+          expect(user_agent_for(client)).to include('md/zjit')
+          expect(user_agent_for(client)).not_to include('md/yjit')
+        end
+
+        it 'includes neither when both are disabled' do
+          stub_jit(:YJIT, enabled: false)
+          stub_jit(:ZJIT, enabled: false)
+
+          ua = user_agent_for(client)
+          expect(ua).not_to include('md/yjit')
+          expect(ua).not_to include('md/zjit')
+        end
+
+        it 'includes neither on non-CRuby engines' do
+          stub_const('RUBY_ENGINE', 'jruby')
+          stub_const('RUBY_ENGINE_VERSION', '9.4.0.0')
+          stub_jit(:YJIT, enabled: false)
+          stub_jit(:ZJIT, enabled: false)
+
+          ua = user_agent_for(client)
+          expect(ua).to include('lang/jruby#9.4.0.0')
+          expect(ua).not_to include('md/yjit')
+          expect(ua).not_to include('md/zjit')
+        end
+      end
+
       context 'test runner' do
         tests = JSON.load_file(
           File.join(File.dirname(__FILE__), 'user_agent_tests.json')