diff --git a/packages/react-native/Libraries/AppDelegate/RCTRootViewFactory.mm b/packages/react-native/Libraries/AppDelegate/RCTRootViewFactory.mm
index 377e5efeae8..e365cf76aba 100644
--- a/packages/react-native/Libraries/AppDelegate/RCTRootViewFactory.mm
+++ b/packages/react-native/Libraries/AppDelegate/RCTRootViewFactory.mm
@@ -283,7 +283,8 @@ static NSDictionary *updateInitialProps(NSDictionary *initialProps, BOOL isFabri
 - (std::shared_ptr<facebook::react::JSRuntimeFactory>)createJSRuntimeFactory
 {
 #if USE_HERMES
-  return std::make_shared<facebook::react::RCTHermesInstance>(_reactNativeConfig, nullptr);
+  return std::make_shared<facebook::react::RCTHermesInstance>(
+      _reactNativeConfig, nullptr, /* allocInOldGenBeforeTTI */ false);
 #else
   return std::make_shared<facebook::react::RCTJscInstance>();
 #endif
diff --git a/packages/react-native/ReactAndroid/api/ReactAndroid.api b/packages/react-native/ReactAndroid/api/ReactAndroid.api
index 7513accbd5f..9589c155177 100644
--- a/packages/react-native/ReactAndroid/api/ReactAndroid.api
+++ b/packages/react-native/ReactAndroid/api/ReactAndroid.api
@@ -3971,7 +3971,7 @@ public final class com/facebook/react/runtime/ReactSurfaceView : com/facebook/re
 public final class com/facebook/react/runtime/hermes/HermesInstance : com/facebook/react/runtime/JSRuntimeFactory {
 	public static final field Companion Lcom/facebook/react/runtime/hermes/HermesInstance$Companion;
 	public fun <init> ()V
-	public fun <init> (Lcom/facebook/react/fabric/ReactNativeConfig;)V
+	public fun <init> (Lcom/facebook/react/fabric/ReactNativeConfig;Z)V
 }
 
 public final class com/facebook/react/runtime/hermes/HermesInstance$Companion {
diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/runtime/hermes/HermesInstance.kt b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/runtime/hermes/HermesInstance.kt
index 47efb3f2a79..7eb8544f82d 100644
--- a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/runtime/hermes/HermesInstance.kt
+++ b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/runtime/hermes/HermesInstance.kt
@@ -13,13 +13,20 @@ import com.facebook.react.fabric.ReactNativeConfig
 import com.facebook.react.runtime.JSRuntimeFactory
 import com.facebook.soloader.SoLoader
 
-public class HermesInstance(reactNativeConfig: ReactNativeConfig?) :
-    JSRuntimeFactory(initHybrid(reactNativeConfig as Any?)) {
+public class HermesInstance(
+    reactNativeConfig: ReactNativeConfig?,
+    allocInOldGenBeforeTTI: Boolean
+) : JSRuntimeFactory(initHybrid(reactNativeConfig as Any?, allocInOldGenBeforeTTI)) {
 
-  public constructor() : this(null)
+  public constructor() : this(null, false)
 
   public companion object {
-    @JvmStatic @DoNotStrip protected external fun initHybrid(reactNativeConfig: Any?): HybridData
+    @JvmStatic
+    @DoNotStrip
+    protected external fun initHybrid(
+        reactNativeConfig: Any?,
+        allocInOldGenBeforeTTI: Boolean
+    ): HybridData
 
     init {
       SoLoader.loadLibrary("hermesinstancejni")
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/runtime/hermes/jni/JHermesInstance.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/runtime/hermes/jni/JHermesInstance.cpp
index deabc529969..b09f3b5a198 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/runtime/hermes/jni/JHermesInstance.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/runtime/hermes/jni/JHermesInstance.cpp
@@ -14,12 +14,13 @@ namespace facebook::react {
 
 jni::local_ref<JHermesInstance::jhybriddata> JHermesInstance::initHybrid(
     jni::alias_ref<jclass> /* unused */,
-    jni::alias_ref<jobject> reactNativeConfig) {
+    jni::alias_ref<jobject> reactNativeConfig,
+    bool allocInOldGenBeforeTTI) {
   std::shared_ptr<const ReactNativeConfig> config = reactNativeConfig != nullptr
       ? std::make_shared<const ReactNativeConfigHolder>(reactNativeConfig)
       : nullptr;
 
-  return makeCxxInstance(config);
+  return makeCxxInstance(config, allocInOldGenBeforeTTI);
 }
 
 void JHermesInstance::registerNatives() {
@@ -31,7 +32,7 @@ void JHermesInstance::registerNatives() {
 std::unique_ptr<JSRuntime> JHermesInstance::createJSRuntime(
     std::shared_ptr<MessageQueueThread> msgQueueThread) noexcept {
   return HermesInstance::createJSRuntime(
-      reactNativeConfig_, nullptr, msgQueueThread);
+      reactNativeConfig_, nullptr, msgQueueThread, allocInOldGenBeforeTTI_);
 }
 
 } // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/runtime/hermes/jni/JHermesInstance.h b/packages/react-native/ReactAndroid/src/main/jni/react/runtime/hermes/jni/JHermesInstance.h
index 5ee3450442d..4d5c44ff9bf 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/runtime/hermes/jni/JHermesInstance.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/runtime/hermes/jni/JHermesInstance.h
@@ -28,12 +28,16 @@ class JHermesInstance
 
   static jni::local_ref<jhybriddata> initHybrid(
       jni::alias_ref<jclass> /* unused */,
-      jni::alias_ref<jobject> reactNativeConfig);
+      jni::alias_ref<jobject> reactNativeConfig,
+      bool allocInOldGenBeforeTTI);
 
   static void registerNatives();
 
-  JHermesInstance(std::shared_ptr<const ReactNativeConfig> reactNativeConfig)
-      : reactNativeConfig_(reactNativeConfig){};
+  JHermesInstance(
+      std::shared_ptr<const ReactNativeConfig> reactNativeConfig,
+      bool allocInOldGenBeforeTTI)
+      : reactNativeConfig_(std::move(reactNativeConfig)),
+        allocInOldGenBeforeTTI_(allocInOldGenBeforeTTI){};
 
   std::unique_ptr<JSRuntime> createJSRuntime(
       std::shared_ptr<MessageQueueThread> msgQueueThread) noexcept;
@@ -44,6 +48,7 @@ class JHermesInstance
   friend HybridBase;
 
   std::shared_ptr<const ReactNativeConfig> reactNativeConfig_;
+  bool allocInOldGenBeforeTTI_;
 };
 
 } // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/jsinspector-modern/tests/ReactInstanceIntegrationTest.cpp b/packages/react-native/ReactCommon/jsinspector-modern/tests/ReactInstanceIntegrationTest.cpp
index 0173466df99..1f48befd367 100644
--- a/packages/react-native/ReactCommon/jsinspector-modern/tests/ReactInstanceIntegrationTest.cpp
+++ b/packages/react-native/ReactCommon/jsinspector-modern/tests/ReactInstanceIntegrationTest.cpp
@@ -51,7 +51,8 @@ void ReactInstanceIntegrationTest::SetUp() {
 
   auto jsRuntimeFactory = std::make_unique<react::HermesInstance>();
   std::unique_ptr<react::JSRuntime> runtime_ =
-      jsRuntimeFactory->createJSRuntime(nullptr, nullptr, messageQueueThread);
+      jsRuntimeFactory->createJSRuntime(
+          nullptr, nullptr, messageQueueThread, false);
   jsi::Runtime* jsiRuntime = &runtime_->getRuntime();
 
   // Error handler:
diff --git a/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.cpp b/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.cpp
index 0a42996a11e..8e2e193a53c 100644
--- a/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.cpp
+++ b/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.cpp
@@ -121,32 +121,37 @@ class HermesJSRuntime : public JSRuntime {
 
 std::unique_ptr<JSRuntime> HermesInstance::createJSRuntime(
     std::shared_ptr<const ReactNativeConfig> reactNativeConfig,
-    std::shared_ptr<::hermes::vm::CrashManager> cm,
-    std::shared_ptr<MessageQueueThread> msgQueueThread) noexcept {
+    std::shared_ptr<::hermes::vm::CrashManager> crashManager,
+    std::shared_ptr<MessageQueueThread> msgQueueThread,
+    bool allocInOldGenBeforeTTI) noexcept {
   assert(msgQueueThread != nullptr);
+
+  auto gcConfig = ::hermes::vm::GCConfig::Builder()
+                      // Default to 3GB
+                      .withMaxHeapSize(3072 << 20)
+                      .withName("RNBridgeless");
+
+  if (allocInOldGenBeforeTTI) {
+    // For the next two arguments: avoid GC before TTI
+    // by initializing the runtime to allocate directly
+    // in the old generation, but revert to normal
+    // operation when we reach the (first) TTI point.
+    gcConfig.withAllocInYoung(false).withRevertToYGAtTTI(true);
+  }
+
   int64_t vmExperimentFlags = reactNativeConfig
       ? reactNativeConfig->getInt64("ios_hermes:vm_experiment_flags")
       : 0;
 
   ::hermes::vm::RuntimeConfig::Builder runtimeConfigBuilder =
       ::hermes::vm::RuntimeConfig::Builder()
-          .withGCConfig(::hermes::vm::GCConfig::Builder()
-                            // Default to 3GB
-                            .withMaxHeapSize(3072 << 20)
-                            .withName("RNBridgeless")
-                            // For the next two arguments: avoid GC before TTI
-                            // by initializing the runtime to allocate directly
-                            // in the old generation, but revert to normal
-                            // operation when we reach the (first) TTI point.
-                            .withAllocInYoung(false)
-                            .withRevertToYGAtTTI(true)
-                            .build())
+          .withGCConfig(gcConfig.build())
           .withEnableSampleProfiling(true)
           .withMicrotaskQueue(ReactNativeFeatureFlags::enableMicrotasks())
           .withVMExperimentFlags(vmExperimentFlags);
 
-  if (cm) {
-    runtimeConfigBuilder.withCrashMgr(cm);
+  if (crashManager) {
+    runtimeConfigBuilder.withCrashMgr(crashManager);
   }
 
   std::unique_ptr<HermesRuntime> hermesRuntime =
diff --git a/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.h b/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.h
index 71b08d2fd5b..5a97875d1da 100644
--- a/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.h
+++ b/packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.h
@@ -19,8 +19,9 @@ class HermesInstance {
  public:
   static std::unique_ptr<JSRuntime> createJSRuntime(
       std::shared_ptr<const ReactNativeConfig> reactNativeConfig,
-      std::shared_ptr<::hermes::vm::CrashManager> cm,
-      std::shared_ptr<MessageQueueThread> msgQueueThread) noexcept;
+      std::shared_ptr<::hermes::vm::CrashManager> crashManager,
+      std::shared_ptr<MessageQueueThread> msgQueueThread,
+      bool allocInOldGenBeforeTTI) noexcept;
 };
 
 } // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTHermesInstance.h b/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTHermesInstance.h
index 533aa82b924..ea2565b3543 100644
--- a/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTHermesInstance.h
+++ b/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTHermesInstance.h
@@ -13,8 +13,8 @@
 #import <react/runtime/JSRuntimeFactory.h>
 #import <react/runtime/hermes/HermesInstance.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
+
 using CrashManagerProvider =
     std::function<std::shared_ptr<::hermes::vm::CrashManager>()>;
 
@@ -24,7 +24,8 @@ class RCTHermesInstance : public JSRuntimeFactory {
   RCTHermesInstance();
   RCTHermesInstance(
       std::shared_ptr<const ReactNativeConfig> reactNativeConfig,
-      CrashManagerProvider crashManagerProvider);
+      CrashManagerProvider crashManagerProvider,
+      bool allocInOldGenBeforeTTI);
 
   std::unique_ptr<JSRuntime> createJSRuntime(
       std::shared_ptr<MessageQueueThread> msgQueueThread) noexcept override;
@@ -35,6 +36,7 @@ class RCTHermesInstance : public JSRuntimeFactory {
   std::shared_ptr<const ReactNativeConfig> _reactNativeConfig;
   CrashManagerProvider _crashManagerProvider;
   std::unique_ptr<HermesInstance> _hermesInstance;
+  bool _allocInOldGenBeforeTTI;
 };
-} // namespace react
-} // namespace facebook
+
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTHermesInstance.mm b/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTHermesInstance.mm
index c3e4951ded6..bd3ea5c7a97 100644
--- a/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTHermesInstance.mm
+++ b/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTHermesInstance.mm
@@ -7,16 +7,18 @@
 
 #import "RCTHermesInstance.h"
 
-namespace facebook {
-namespace react {
-RCTHermesInstance::RCTHermesInstance() : RCTHermesInstance(nullptr, nullptr) {}
+namespace facebook::react {
+
+RCTHermesInstance::RCTHermesInstance() : RCTHermesInstance(nullptr, nullptr, false) {}
 
 RCTHermesInstance::RCTHermesInstance(
     std::shared_ptr<const ReactNativeConfig> reactNativeConfig,
-    CrashManagerProvider crashManagerProvider)
+    CrashManagerProvider crashManagerProvider,
+    bool allocInOldGenBeforeTTI)
     : _reactNativeConfig(std::move(reactNativeConfig)),
       _crashManagerProvider(std::move(crashManagerProvider)),
-      _hermesInstance(std::make_unique<HermesInstance>())
+      _hermesInstance(std::make_unique<HermesInstance>()),
+      _allocInOldGenBeforeTTI(allocInOldGenBeforeTTI)
 {
 }
 
@@ -24,8 +26,10 @@ std::unique_ptr<JSRuntime> RCTHermesInstance::createJSRuntime(
     std::shared_ptr<MessageQueueThread> msgQueueThread) noexcept
 {
   return _hermesInstance->createJSRuntime(
-      _reactNativeConfig, _crashManagerProvider ? _crashManagerProvider() : nullptr, msgQueueThread);
+      _reactNativeConfig,
+      _crashManagerProvider ? _crashManagerProvider() : nullptr,
+      std::move(msgQueueThread),
+      _allocInOldGenBeforeTTI);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react