diff --git a/ReactAndroid/src/androidTest/java/com/facebook/react/testing/BUCK b/ReactAndroid/src/androidTest/java/com/facebook/react/testing/BUCK
index ce91a2147..a88b8ccb4 100644
--- a/ReactAndroid/src/androidTest/java/com/facebook/react/testing/BUCK
+++ b/ReactAndroid/src/androidTest/java/com/facebook/react/testing/BUCK
@@ -28,6 +28,7 @@ rn_android_library(
         react_native_target("java/com/facebook/react/common:common"),
         react_native_target("java/com/facebook/react/devsupport:interfaces"),
         react_native_target("java/com/facebook/react/fabric:fabric"),
+        react_native_target("java/com/facebook/react/jscexecutor:jscexecutor"),
         react_native_target("java/com/facebook/react/module/annotations:annotations"),
         react_native_target("java/com/facebook/react/module/model:model"),
         react_native_target("java/com/facebook/react/modules/core:core"),
diff --git a/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/BUCK b/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/BUCK
new file mode 100644
index 000000000..788857470
--- /dev/null
+++ b/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/BUCK
@@ -0,0 +1,35 @@
+load("//tools/build_defs/oss:rn_defs.bzl", "ANDROID", "FBJNI_TARGET", "rn_xplat_cxx_library", "react_native_xplat_target", "react_native_target", "react_native_dep", "rn_android_library")
+
+rn_android_library(
+    name = "jscexecutor",
+    srcs = glob(["*.java"]),
+    visibility = [
+        "PUBLIC",
+    ],
+    deps = [
+        ":jni",
+        react_native_dep("libraries/soloader/java/com/facebook/soloader:soloader"),
+        react_native_target("java/com/facebook/react/bridge:bridge"),
+    ],
+)
+
+rn_xplat_cxx_library(
+    name = "jni",
+    srcs = glob(["*.cpp"]),
+    headers = glob(["*.h"]),
+    header_namespace = "",
+    compiler_flags = ["-fexceptions"],
+    platforms = ANDROID,
+    fbandroid_allow_jni_merging = True,
+    soname = "libjscexecutor.$(ext)",
+    visibility = [
+        react_native_target("java/com/facebook/react/jscexecutor:jscexecutor"),
+    ],
+    deps = [
+        "xplat//folly:molly",
+        FBJNI_TARGET,
+        react_native_target("jni/react/jni:jni"),
+        react_native_xplat_target("jsi:JSCRuntime"),
+        react_native_xplat_target("jsiexecutor:jsiexecutor"),
+    ],
+)
diff --git a/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/JSCExecutor.java b/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/JSCExecutor.java
new file mode 100644
index 000000000..7455dffb4
--- /dev/null
+++ b/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/JSCExecutor.java
@@ -0,0 +1,32 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * <p>This source code is licensed under the MIT license found in the LICENSE file in the root
+ * directory of this source tree.
+ */
+
+package com.facebook.react.jscexecutor;
+
+import com.facebook.jni.HybridData;
+import com.facebook.proguard.annotations.DoNotStrip;
+import com.facebook.react.bridge.JavaScriptExecutor;
+import com.facebook.react.bridge.ReadableNativeMap;
+import com.facebook.soloader.SoLoader;
+
+@DoNotStrip
+/* package */ class JSCExecutor extends JavaScriptExecutor {
+  static {
+    SoLoader.loadLibrary("jscexecutor");
+  }
+
+  /* package */ JSCExecutor(ReadableNativeMap jscConfig) {
+    super(initHybrid(jscConfig));
+  }
+
+  @Override
+  public String getName() {
+    return "JSCExecutor";
+  }
+
+  private static native HybridData initHybrid(ReadableNativeMap jscConfig);
+}
diff --git a/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/JSCExecutorFactory.java b/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/JSCExecutorFactory.java
new file mode 100644
index 000000000..a71b9bcc8
--- /dev/null
+++ b/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/JSCExecutorFactory.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.jscexecutor;
+
+import com.facebook.react.bridge.JavaScriptExecutor;
+import com.facebook.react.bridge.JavaScriptExecutorFactory;
+import com.facebook.react.bridge.WritableNativeMap;
+
+public class JSCExecutorFactory implements JavaScriptExecutorFactory {
+  private final String mAppName;
+  private final String mDeviceName;
+
+  public JSCExecutorFactory(String appName, String deviceName) {
+    this.mAppName = appName;
+    this.mDeviceName = deviceName;
+  }
+
+  @Override
+  public JavaScriptExecutor create() throws Exception {
+    WritableNativeMap jscConfig = new WritableNativeMap();
+    jscConfig.putString("OwnerIdentity", "ReactNative");
+    jscConfig.putString("AppIdentity", mAppName);
+    jscConfig.putString("DeviceIdentity", mDeviceName);
+    return new JSCExecutor(jscConfig);
+  }
+
+  @Override
+  public String toString() {
+    return "JSIExecutor+JSCRuntime";
+  }
+}
diff --git a/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/OnLoad.cpp b/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/OnLoad.cpp
new file mode 100644
index 000000000..c6f185aac
--- /dev/null
+++ b/ReactAndroid/src/main/java/com/facebook/react/jscexecutor/OnLoad.cpp
@@ -0,0 +1,70 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#include <fb/fbjni.h>
+#include <folly/Memory.h>
+#include <jsi/JSCRuntime.h>
+#include <jsireact/JSIExecutor.h>
+#include <react/jni/JavaScriptExecutorHolder.h>
+#include <react/jni/JReactMarker.h>
+#include <react/jni/JSLogging.h>
+#include <react/jni/ReadableNativeMap.h>
+
+namespace facebook {
+namespace react {
+
+namespace {
+
+class JSCExecutorFactory : public JSExecutorFactory {
+public:
+  std::unique_ptr<JSExecutor> createJSExecutor(
+      std::shared_ptr<ExecutorDelegate> delegate,
+      std::shared_ptr<MessageQueueThread> jsQueue) override {
+    return folly::make_unique<JSIExecutor>(
+      jsc::makeJSCRuntime(),
+      delegate,
+      [](const std::string& message, unsigned int logLevel) {
+        reactAndroidLoggingHook(message, logLevel);
+      },
+      JSIExecutor::defaultTimeoutInvoker,
+      nullptr);
+  }
+};
+
+}
+
+// This is not like JSCJavaScriptExecutor, which calls JSC directly.  This uses
+// JSIExecutor with JSCRuntime.
+class JSCExecutorHolder
+    : public jni::HybridClass<JSCExecutorHolder, JavaScriptExecutorHolder> {
+ public:
+  static constexpr auto kJavaDescriptor = "Lcom/facebook/react/jscexecutor/JSCExecutor;";
+
+  static jni::local_ref<jhybriddata> initHybrid(
+      jni::alias_ref<jclass>, ReadableNativeMap*) {
+    // This is kind of a weird place for stuff, but there's no other
+    // good place for initialization which is specific to JSC on
+    // Android.
+    JReactMarker::setLogPerfMarkerIfNeeded();
+    // TODO mhorowitz T28461666 fill in some missing nice to have glue
+    return makeCxxInstance(folly::make_unique<JSCExecutorFactory>());
+  }
+
+  static void registerNatives() {
+    registerHybrid({
+      makeNativeMethod("initHybrid", JSCExecutorHolder::initHybrid),
+    });
+  }
+
+ private:
+  friend HybridBase;
+  using HybridBase::HybridBase;
+};
+
+} // namespace react
+} // namespace facebook
+
+JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved) {
+  return facebook::jni::initialize(vm, [] {
+      facebook::react::JSCExecutorHolder::registerNatives();
+  });
+}
diff --git a/ReactCommon/jsiexecutor/BUCK b/ReactCommon/jsiexecutor/BUCK
new file mode 100644
index 000000000..e6e6334be
--- /dev/null
+++ b/ReactCommon/jsiexecutor/BUCK
@@ -0,0 +1,39 @@
+load("//tools/build_defs/oss:rn_defs.bzl", "cxx_library", "react_native_xplat_dep", "react_native_xplat_target")
+
+cxx_library(
+    name = "jsiexecutor",
+    srcs = [
+        "jsireact/JSIExecutor.cpp",
+        "jsireact/JSINativeModules.cpp",
+    ],
+    header_namespace = "",
+    exported_headers = {
+        "jsireact/JSIExecutor.h": "jsireact/JSIExecutor.h",
+        "jsireact/JSINativeModules.h": "jsireact/JSINativeModules.h",
+    },
+    compiler_flags = [
+        "-fexceptions",
+        "-frtti",
+    ],
+    fbandroid_deps = [
+        "xplat//folly:molly",
+        "xplat//third-party/glog:glog",
+        "xplat//third-party/linker_lib:atomic",
+    ],
+    fbobjc_force_static = True,
+    fbobjc_header_path_prefix = "",
+    platforms = (ANDROID, APPLE),
+    preprocessor_flags = [
+        "-DLOG_TAG=\"ReactNative\"",
+        "-DWITH_FBSYSTRACE=1",
+    ],
+    visibility = [
+        "PUBLIC",
+    ],
+    xcode_public_headers_symlinks = True,
+    deps = [
+        react_native_xplat_dep("jsi:jsi"),
+        react_native_xplat_dep("jsi:JSIDynamic"),
+        react_native_xplat_target("cxxreact:bridge"),
+    ],
+)
diff --git a/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp b/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp
new file mode 100644
index 000000000..f243d8d7e
--- /dev/null
+++ b/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp
@@ -0,0 +1,405 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#include "jsireact/JSIExecutor.h"
+
+#include <cxxreact/JSBigString.h>
+#include <cxxreact/ModuleRegistry.h>
+#include <cxxreact/ReactMarker.h>
+#include <cxxreact/SystraceSection.h>
+#include <folly/Conv.h>
+#include <folly/json.h>
+#include <glog/logging.h>
+#include <jsi/JSIDynamic.h>
+
+#include <stdexcept>
+
+using namespace facebook::jsi;
+
+namespace facebook {
+namespace react {
+
+JSIExecutorFactory::JSIExecutorFactory(
+    std::shared_ptr<jsi::Runtime> runtime,
+    JSIExecutor::Logger logger,
+    JSIExecutor::RuntimeInstaller runtimeInstaller)
+    : runtime_(runtime),
+      logger_(logger),
+      runtimeInstaller_(runtimeInstaller) {}
+
+std::unique_ptr<JSExecutor> JSIExecutorFactory::createJSExecutor(
+    std::shared_ptr<ExecutorDelegate> delegate,
+    std::shared_ptr<MessageQueueThread>) {
+  return std::make_unique<JSIExecutor>(
+      runtime_,
+      delegate,
+      logger_,
+      JSIExecutor::defaultTimeoutInvoker,
+      runtimeInstaller_);
+}
+
+class JSIExecutor::NativeModuleProxy : public jsi::HostObject {
+ public:
+  NativeModuleProxy(JSIExecutor& executor) : executor_(executor) {}
+
+  Value get(Runtime& rt, const PropNameID& name) override {
+    if (name.utf8(rt) == "name") {
+      return jsi::String::createFromAscii(rt, "NativeModules");
+    }
+
+    return executor_.nativeModules_.getModule(rt, name);
+  }
+
+  void set(Runtime&, const PropNameID&, const Value&) override {
+    throw std::runtime_error(
+        "Unable to put on NativeModules: Operation unsupported");
+  }
+
+ private:
+  JSIExecutor& executor_;
+};
+
+namespace {
+
+// basename_r isn't in all iOS SDKs, so use this simple version instead.
+std::string simpleBasename(const std::string& path) {
+  size_t pos = path.rfind("/");
+  return (pos != std::string::npos) ? path.substr(pos) : path;
+}
+
+} // namespace
+
+JSIExecutor::JSIExecutor(
+    std::shared_ptr<jsi::Runtime> runtime,
+    std::shared_ptr<ExecutorDelegate> delegate,
+    Logger logger,
+    const JSIScopedTimeoutInvoker& scopedTimeoutInvoker,
+    RuntimeInstaller runtimeInstaller)
+    : runtime_(runtime),
+      delegate_(delegate),
+      nativeModules_(delegate ? delegate->getModuleRegistry() : nullptr),
+      logger_(logger),
+      scopedTimeoutInvoker_(scopedTimeoutInvoker),
+      runtimeInstaller_(runtimeInstaller) {
+  runtime_->global().setProperty(
+      *runtime, "__jsiExecutorDescription", runtime->description());
+}
+
+void JSIExecutor::loadApplicationScript(
+    std::unique_ptr<const JSBigString> script,
+    std::string sourceURL) {
+  SystraceSection s("JSIExecutor::loadApplicationScript");
+
+  // TODO: check for and use precompiled HBC
+
+  runtime_->global().setProperty(
+      *runtime_,
+      "nativeModuleProxy",
+      Object::createFromHostObject(
+          *runtime_, std::make_shared<NativeModuleProxy>(*this)));
+
+  runtime_->global().setProperty(
+      *runtime_,
+      "nativeFlushQueueImmediate",
+      Function::createFromHostFunction(
+          *runtime_,
+          PropNameID::forAscii(*runtime_, "nativeFlushQueueImmediate"),
+          1,
+          [this](
+              jsi::Runtime&,
+              const jsi::Value&,
+              const jsi::Value* args,
+              size_t count) {
+            if (count != 1) {
+              throw std::invalid_argument(
+                  "nativeFlushQueueImmediate arg count must be 1");
+            }
+            callNativeModules(args[0], false);
+            return Value::undefined();
+          }));
+
+  runtime_->global().setProperty(
+      *runtime_,
+      "nativeCallSyncHook",
+      Function::createFromHostFunction(
+          *runtime_,
+          PropNameID::forAscii(*runtime_, "nativeCallSyncHook"),
+          1,
+          [this](
+              jsi::Runtime&,
+              const jsi::Value&,
+              const jsi::Value* args,
+              size_t count) { return nativeCallSyncHook(args, count); }));
+
+  if (logger_) {
+    // Only inject the logging function if it was supplied by the caller.
+    runtime_->global().setProperty(
+        *runtime_,
+        "nativeLoggingHook",
+        Function::createFromHostFunction(
+            *runtime_,
+            PropNameID::forAscii(*runtime_, "nativeLoggingHook"),
+            2,
+            [this](
+                jsi::Runtime&,
+                const jsi::Value&,
+                const jsi::Value* args,
+                size_t count) {
+              if (count != 2) {
+                throw std::invalid_argument(
+                    "nativeLoggingHook takes 2 arguments");
+              }
+              logger_(
+                  args[0].asString(*runtime_).utf8(*runtime_),
+                  folly::to<unsigned int>(args[1].asNumber()));
+              return Value::undefined();
+            }));
+  }
+
+  if (runtimeInstaller_) {
+    runtimeInstaller_(*runtime_);
+  }
+
+  bool hasLogger(ReactMarker::logTaggedMarker);
+  std::string scriptName = simpleBasename(sourceURL);
+  if (hasLogger) {
+    ReactMarker::logTaggedMarker(
+        ReactMarker::RUN_JS_BUNDLE_START, scriptName.c_str());
+  }
+  runtime_->evaluateJavaScript(
+      std::make_unique<BigStringBuffer>(std::move(script)), sourceURL);
+  flush();
+  if (hasLogger) {
+    ReactMarker::logMarker(ReactMarker::CREATE_REACT_CONTEXT_STOP);
+    ReactMarker::logTaggedMarker(
+        ReactMarker::RUN_JS_BUNDLE_STOP, scriptName.c_str());
+  }
+}
+
+void JSIExecutor::setBundleRegistry(std::unique_ptr<RAMBundleRegistry> r) {
+  if (!bundleRegistry_) {
+    runtime_->global().setProperty(
+        *runtime_,
+        "nativeRequire",
+        Function::createFromHostFunction(
+            *runtime_,
+            PropNameID::forAscii(*runtime_, "nativeRequire"),
+            2,
+            [this](
+                Runtime& rt,
+                const facebook::jsi::Value&,
+                const facebook::jsi::Value* args,
+                size_t count) { return nativeRequire(args, count); }));
+  }
+  bundleRegistry_ = std::move(r);
+}
+
+void JSIExecutor::registerBundle(
+    uint32_t bundleId,
+    const std::string& bundlePath) {
+  const auto tag = folly::to<std::string>(bundleId);
+  ReactMarker::logTaggedMarker(
+      ReactMarker::REGISTER_JS_SEGMENT_START, tag.c_str());
+  if (bundleRegistry_) {
+    bundleRegistry_->registerBundle(bundleId, bundlePath);
+  } else {
+    auto script = JSBigFileString::fromPath(bundlePath);
+    runtime_->evaluateJavaScript(
+        std::make_unique<BigStringBuffer>(std::move(script)),
+        JSExecutor::getSyntheticBundlePath(bundleId, bundlePath));
+  }
+  ReactMarker::logTaggedMarker(
+      ReactMarker::REGISTER_JS_SEGMENT_STOP, tag.c_str());
+}
+
+void JSIExecutor::callFunction(
+    const std::string& moduleId,
+    const std::string& methodId,
+    const folly::dynamic& arguments) {
+  SystraceSection s(
+      "JSIExecutor::callFunction", "moduleId", moduleId, "methodId", methodId);
+  if (!callFunctionReturnFlushedQueue_) {
+    bindBridge();
+  }
+
+  // Construct the error message producer in case this times out.
+  // This is executed on a background thread, so it must capture its parameters
+  // by value.
+  auto errorProducer = [=] {
+    std::stringstream ss;
+    ss << "moduleID: " << moduleId << " methodID: " << methodId
+       << " arguments: " << folly::toJson(arguments);
+    return ss.str();
+  };
+
+  Value ret = Value::undefined();
+  try {
+    scopedTimeoutInvoker_(
+        [&] {
+          ret = callFunctionReturnFlushedQueue_->call(
+              *runtime_,
+              moduleId,
+              methodId,
+              valueFromDynamic(*runtime_, arguments));
+        },
+        std::move(errorProducer));
+  } catch (...) {
+    std::throw_with_nested(
+        std::runtime_error("Error calling " + moduleId + "." + methodId));
+  }
+
+  callNativeModules(ret, true);
+}
+
+void JSIExecutor::invokeCallback(
+    const double callbackId,
+    const folly::dynamic& arguments) {
+  SystraceSection s("JSIExecutor::invokeCallback", "callbackId", callbackId);
+  if (!invokeCallbackAndReturnFlushedQueue_) {
+    bindBridge();
+  }
+  Value ret;
+  try {
+    ret = invokeCallbackAndReturnFlushedQueue_->call(
+        *runtime_, callbackId, valueFromDynamic(*runtime_, arguments));
+  } catch (...) {
+    std::throw_with_nested(std::runtime_error(
+        folly::to<std::string>("Error invoking callback ", callbackId)));
+  }
+
+  callNativeModules(ret, true);
+}
+
+void JSIExecutor::setGlobalVariable(
+    std::string propName,
+    std::unique_ptr<const JSBigString> jsonValue) {
+  SystraceSection s("JSIExecutor::setGlobalVariable", "propName", propName);
+  runtime_->global().setProperty(
+      *runtime_,
+      propName.c_str(),
+      Value::createFromJsonUtf8(
+          *runtime_,
+          reinterpret_cast<const uint8_t*>(jsonValue->c_str()),
+          jsonValue->size()));
+}
+
+std::string JSIExecutor::getDescription() {
+  return "JSI " + runtime_->description();
+}
+
+void* JSIExecutor::getJavaScriptContext() {
+  return runtime_.get();
+}
+
+bool JSIExecutor::isInspectable() {
+  return runtime_->isInspectable();
+}
+
+void JSIExecutor::bindBridge() {
+  std::call_once(bindFlag_, [this] {
+    SystraceSection s("JSIExecutor::bindBridge (once)");
+    Value batchedBridgeValue =
+        runtime_->global().getProperty(*runtime_, "__fbBatchedBridge");
+    if (batchedBridgeValue.isUndefined()) {
+      Function requireBatchedBridge = runtime_->global().getPropertyAsFunction(
+          *runtime_, "__fbRequireBatchedBridge");
+      batchedBridgeValue = requireBatchedBridge.call(*runtime_);
+      if (batchedBridgeValue.isUndefined()) {
+        throw JSINativeException(
+            "Could not get BatchedBridge, make sure your bundle is packaged correctly");
+      }
+    }
+
+    Object batchedBridge = batchedBridgeValue.asObject(*runtime_);
+    callFunctionReturnFlushedQueue_ = batchedBridge.getPropertyAsFunction(
+        *runtime_, "callFunctionReturnFlushedQueue");
+    invokeCallbackAndReturnFlushedQueue_ = batchedBridge.getPropertyAsFunction(
+        *runtime_, "invokeCallbackAndReturnFlushedQueue");
+    flushedQueue_ =
+        batchedBridge.getPropertyAsFunction(*runtime_, "flushedQueue");
+    callFunctionReturnResultAndFlushedQueue_ =
+        batchedBridge.getPropertyAsFunction(
+            *runtime_, "callFunctionReturnResultAndFlushedQueue");
+  });
+}
+
+void JSIExecutor::callNativeModules(const Value& queue, bool isEndOfBatch) {
+  SystraceSection s("JSIExecutor::callNativeModules");
+  // If this fails, you need to pass a fully functional delegate with a
+  // module registry to the factory/ctor.
+  CHECK(delegate_) << "Attempting to use native modules without a delegate";
+#if 0 // maybe useful for debugging
+  std::string json = runtime_->global().getPropertyAsObject(*runtime_, "JSON")
+    .getPropertyAsFunction(*runtime_, "stringify").call(*runtime_, queue)
+    .getString(*runtime_).utf8(*runtime_);
+#endif
+  delegate_->callNativeModules(
+      *this, dynamicFromValue(*runtime_, queue), isEndOfBatch);
+}
+
+void JSIExecutor::flush() {
+  SystraceSection s("JSIExecutor::flush");
+  if (flushedQueue_) {
+    callNativeModules(flushedQueue_->call(*runtime_), true);
+    return;
+  }
+
+  // When a native module is called from JS, BatchedBridge.enqueueNativeCall()
+  // is invoked.  For that to work, require('BatchedBridge') has to be called,
+  // and when that happens, __fbBatchedBridge is set as a side effect.
+  Value batchedBridge =
+      runtime_->global().getProperty(*runtime_, "__fbBatchedBridge");
+  // So here, if __fbBatchedBridge doesn't exist, then we know no native calls
+  // have happened, and we were able to determine this without forcing
+  // BatchedBridge to be loaded as a side effect.
+  if (!batchedBridge.isUndefined()) {
+    // If calls were made, we bind to the JS bridge methods, and use them to
+    // get the pending queue of native calls.
+    bindBridge();
+    callNativeModules(flushedQueue_->call(*runtime_), true);
+  } else if (delegate_) {
+    // If we have a delegate, we need to call it; we pass a null list to
+    // callNativeModules, since we know there are no native calls, without
+    // calling into JS again.  If no calls were made and there's no delegate,
+    // nothing happens, which is correct.
+    callNativeModules(nullptr, true);
+  }
+}
+
+Value JSIExecutor::nativeRequire(const Value* args, size_t count) {
+  if (count > 2 || count == 0) {
+    throw std::invalid_argument("Got wrong number of args");
+  }
+
+  uint32_t moduleId = folly::to<uint32_t>(args[0].getNumber());
+  uint32_t bundleId = count == 2 ? folly::to<uint32_t>(args[1].getNumber()) : 0;
+  auto module = bundleRegistry_->getModule(bundleId, moduleId);
+
+  runtime_->evaluateJavaScript(
+      std::make_unique<StringBuffer>(module.code), module.name);
+  return facebook::jsi::Value();
+}
+
+Value JSIExecutor::nativeCallSyncHook(const Value* args, size_t count) {
+  if (count != 3) {
+    throw std::invalid_argument("nativeCallSyncHook arg count must be 3");
+  }
+
+  if (!args[2].asObject(*runtime_).isArray(*runtime_)) {
+    throw std::invalid_argument(
+        folly::to<std::string>("method parameters should be array"));
+  }
+
+  MethodCallResult result = delegate_->callSerializableNativeHook(
+      *this,
+      static_cast<unsigned int>(args[0].getNumber()), // moduleId
+      static_cast<unsigned int>(args[1].getNumber()), // methodId
+      dynamicFromValue(*runtime_, args[2])); // args
+
+  if (!result.hasValue()) {
+    return Value::undefined();
+  }
+  return valueFromDynamic(*runtime_, result.value());
+}
+
+} // namespace react
+} // namespace facebook
diff --git a/ReactCommon/jsiexecutor/jsireact/JSIExecutor.h b/ReactCommon/jsiexecutor/jsireact/JSIExecutor.h
new file mode 100644
index 000000000..51c1d86b8
--- /dev/null
+++ b/ReactCommon/jsiexecutor/jsireact/JSIExecutor.h
@@ -0,0 +1,149 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#pragma once
+
+#include "JSINativeModules.h"
+
+#include <cxxreact/JSBigString.h>
+#include <cxxreact/JSExecutor.h>
+#include <cxxreact/RAMBundleRegistry.h>
+#include <jsi/jsi.h>
+#include <functional>
+#include <mutex>
+
+namespace facebook {
+namespace react {
+
+// A JSIScopedTimeoutInvoker is a trampoline-type function for introducing
+// timeouts. Call the TimeoutInvoker with a function to execute, the invokee.
+// The TimeoutInvoker will immediately invoke it, synchronously on the same
+// thread. If the invokee fails to return after some timeout (private to the
+// TimeoutInvoker), a soft error may be reported.
+//
+// If a soft error is reported, the second parameter errorMessageProducer will
+// be invoked to produce an error message, which will be included in the soft
+// error report. Note that the errorMessageProducer will be invoked
+// asynchronously on a different thread.
+//
+// The timeout behavior does NOT caues the invokee to aborted. If the invokee
+// blocks forever, so will the ScopedTimeoutInvoker (but the soft error may
+// still be reported).
+//
+// The invokee is passed by const ref because it is executed synchronously, but
+// the errorMessageProducer is passed by value because it must be copied or
+// moved for async execution.
+//
+// Example usage:
+//
+//   int param = ...;
+//   timeoutInvoker(
+//       [&]{ someBigWork(param); },
+//       [=] -> std::string {
+//           return "someBigWork, param " + std::to_string(param);
+//       })
+//
+using JSIScopedTimeoutInvoker = std::function<void(
+    const std::function<void()>& invokee,
+    std::function<std::string()> errorMessageProducer)>;
+
+class BigStringBuffer : public jsi::Buffer {
+ public:
+  BigStringBuffer(std::unique_ptr<const JSBigString> script)
+      : script_(std::move(script)) {}
+
+  size_t size() const override {
+    return script_->size();
+  }
+
+  const uint8_t* data() const override {
+    return reinterpret_cast<const uint8_t*>(script_->c_str());
+  }
+
+ private:
+  std::unique_ptr<const JSBigString> script_;
+};
+
+class JSIExecutor : public JSExecutor {
+ public:
+  using Logger =
+      std::function<void(const std::string& message, unsigned int logLevel)>;
+
+  using RuntimeInstaller = std::function<void(jsi::Runtime& runtime)>;
+
+  JSIExecutor(
+      std::shared_ptr<jsi::Runtime> runtime,
+      std::shared_ptr<ExecutorDelegate> delegate,
+      Logger logger,
+      const JSIScopedTimeoutInvoker& timeoutInvoker,
+      RuntimeInstaller runtimeInstaller);
+  void loadApplicationScript(
+      std::unique_ptr<const JSBigString> script,
+      std::string sourceURL) override;
+  void setBundleRegistry(std::unique_ptr<RAMBundleRegistry>) override;
+  void registerBundle(uint32_t bundleId, const std::string& bundlePath)
+      override;
+  void callFunction(
+      const std::string& moduleId,
+      const std::string& methodId,
+      const folly::dynamic& arguments) override;
+  void invokeCallback(const double callbackId, const folly::dynamic& arguments)
+      override;
+  void setGlobalVariable(
+      std::string propName,
+      std::unique_ptr<const JSBigString> jsonValue) override;
+  std::string getDescription() override;
+  void* getJavaScriptContext() override;
+  bool isInspectable() override;
+
+  // An implementation of JSIScopedTimeoutInvoker that simply runs the
+  // invokee, with no timeout.
+  static void defaultTimeoutInvoker(
+      const std::function<void()>& invokee,
+      std::function<std::string()> errorMessageProducer) {
+    (void)errorMessageProducer;
+    invokee();
+  }
+
+ private:
+  class NativeModuleProxy;
+
+  void flush();
+  void bindBridge();
+  void callNativeModules(const jsi::Value& queue, bool isEndOfBatch);
+  jsi::Value nativeCallSyncHook(const jsi::Value* args, size_t count);
+  jsi::Value nativeRequire(const jsi::Value* args, size_t count);
+
+  std::shared_ptr<jsi::Runtime> runtime_;
+  std::shared_ptr<ExecutorDelegate> delegate_;
+  JSINativeModules nativeModules_;
+  std::once_flag bindFlag_;
+  std::unique_ptr<RAMBundleRegistry> bundleRegistry_;
+  Logger logger_;
+  JSIScopedTimeoutInvoker scopedTimeoutInvoker_;
+  RuntimeInstaller runtimeInstaller_;
+
+  folly::Optional<jsi::Function> callFunctionReturnFlushedQueue_;
+  folly::Optional<jsi::Function> invokeCallbackAndReturnFlushedQueue_;
+  folly::Optional<jsi::Function> flushedQueue_;
+  folly::Optional<jsi::Function> callFunctionReturnResultAndFlushedQueue_;
+};
+
+class JSIExecutorFactory : public JSExecutorFactory {
+ public:
+  explicit JSIExecutorFactory(
+      std::shared_ptr<jsi::Runtime> runtime,
+      JSIExecutor::Logger logger,
+      JSIExecutor::RuntimeInstaller);
+
+  std::unique_ptr<JSExecutor> createJSExecutor(
+      std::shared_ptr<ExecutorDelegate> delegate,
+      std::shared_ptr<MessageQueueThread> jsQueue) override;
+
+ private:
+  std::shared_ptr<jsi::Runtime> runtime_;
+  JSIExecutor::Logger logger_;
+  JSIExecutor::RuntimeInstaller runtimeInstaller_;
+};
+
+} // namespace react
+} // namespace facebook
diff --git a/ReactCommon/jsiexecutor/jsireact/JSINativeModules.cpp b/ReactCommon/jsiexecutor/jsireact/JSINativeModules.cpp
new file mode 100644
index 000000000..7a5e0673c
--- /dev/null
+++ b/ReactCommon/jsiexecutor/jsireact/JSINativeModules.cpp
@@ -0,0 +1,86 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#include "jsireact/JSINativeModules.h"
+
+#include <cxxreact/ReactMarker.h>
+
+#include <jsi/JSIDynamic.h>
+
+#include <string>
+
+using namespace facebook::jsi;
+
+namespace facebook {
+namespace react {
+
+JSINativeModules::JSINativeModules(
+    std::shared_ptr<ModuleRegistry> moduleRegistry)
+    : m_moduleRegistry(std::move(moduleRegistry)) {}
+
+Value JSINativeModules::getModule(Runtime& rt, const PropNameID& name) {
+  if (!m_moduleRegistry) {
+    return nullptr;
+  }
+
+  std::string moduleName = name.utf8(rt);
+
+  const auto it = m_objects.find(moduleName);
+  if (it != m_objects.end()) {
+    return Value(rt, it->second);
+  }
+
+  auto module = createModule(rt, moduleName);
+  if (!module.hasValue()) {
+    // Allow lookup to continue in the objects own properties, which allows for
+    // overrides of NativeModules
+    return nullptr;
+  }
+
+  auto result =
+      m_objects.emplace(std::move(moduleName), std::move(*module)).first;
+  return Value(rt, result->second);
+}
+
+void JSINativeModules::reset() {
+  m_genNativeModuleJS = nullptr;
+  m_objects.clear();
+}
+
+folly::Optional<Object> JSINativeModules::createModule(
+    Runtime& rt,
+    const std::string& name) {
+  bool hasLogger(ReactMarker::logTaggedMarker);
+  if (hasLogger) {
+    ReactMarker::logTaggedMarker(
+        ReactMarker::NATIVE_MODULE_SETUP_START, name.c_str());
+  }
+
+  if (!m_genNativeModuleJS) {
+    m_genNativeModuleJS =
+        rt.global().getPropertyAsFunction(rt, "__fbGenNativeModule");
+  }
+
+  auto result = m_moduleRegistry->getConfig(name);
+  if (!result.hasValue()) {
+    return nullptr;
+  }
+
+  Value moduleInfo = m_genNativeModuleJS->call(
+      rt,
+      valueFromDynamic(rt, result->config),
+      static_cast<double>(result->index));
+  CHECK(!moduleInfo.isNull()) << "Module returned from genNativeModule is null";
+
+  folly::Optional<Object> module(
+      moduleInfo.asObject(rt).getPropertyAsObject(rt, "module"));
+
+  if (hasLogger) {
+    ReactMarker::logTaggedMarker(
+        ReactMarker::NATIVE_MODULE_SETUP_STOP, name.c_str());
+  }
+
+  return module;
+}
+
+} // namespace react
+} // namespace facebook
diff --git a/ReactCommon/jsiexecutor/jsireact/JSINativeModules.h b/ReactCommon/jsiexecutor/jsireact/JSINativeModules.h
new file mode 100644
index 000000000..6b7ff731a
--- /dev/null
+++ b/ReactCommon/jsiexecutor/jsireact/JSINativeModules.h
@@ -0,0 +1,35 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#pragma once
+
+#include <memory>
+#include <string>
+
+#include <cxxreact/ModuleRegistry.h>
+#include <folly/Optional.h>
+#include <jsi/jsi.h>
+
+namespace facebook {
+namespace react {
+
+/**
+ * Holds and creates JS representations of the modules in ModuleRegistry
+ */
+class JSINativeModules {
+ public:
+  explicit JSINativeModules(std::shared_ptr<ModuleRegistry> moduleRegistry);
+  jsi::Value getModule(jsi::Runtime& rt, const jsi::PropNameID& name);
+  void reset();
+
+ private:
+  folly::Optional<jsi::Function> m_genNativeModuleJS;
+  std::shared_ptr<ModuleRegistry> m_moduleRegistry;
+  std::unordered_map<std::string, jsi::Object> m_objects;
+
+  folly::Optional<jsi::Object> createModule(
+      jsi::Runtime& rt,
+      const std::string& name);
+};
+
+} // namespace react
+} // namespace facebook