diff --git a/engine/CMakeLists.txt b/engine/CMakeLists.txt
index 65c8debd..741f8a2c 100644
--- a/engine/CMakeLists.txt
+++ b/engine/CMakeLists.txt
@@ -241,12 +241,17 @@ add_library(XCEngine STATIC
     ${CMAKE_CURRENT_SOURCE_DIR}/src/Resources/AudioClip/AudioLoader.cpp
 
     # Scripting
+    ${CMAKE_CURRENT_SOURCE_DIR}/include/XCEngine/Scripting/IScriptRuntime.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/include/XCEngine/Scripting/NullScriptRuntime.h
     ${CMAKE_CURRENT_SOURCE_DIR}/include/XCEngine/Scripting/ScriptField.h
     ${CMAKE_CURRENT_SOURCE_DIR}/include/XCEngine/Scripting/ScriptFieldStorage.h
     ${CMAKE_CURRENT_SOURCE_DIR}/include/XCEngine/Scripting/ScriptComponent.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/include/XCEngine/Scripting/ScriptEngine.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/src/Scripting/NullScriptRuntime.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/src/Scripting/ScriptField.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/src/Scripting/ScriptFieldStorage.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/src/Scripting/ScriptComponent.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/src/Scripting/ScriptEngine.cpp
 
     # Components
     ${CMAKE_CURRENT_SOURCE_DIR}/include/XCEngine/Components/Component.h
diff --git a/engine/include/XCEngine/Scripting/IScriptRuntime.h b/engine/include/XCEngine/Scripting/IScriptRuntime.h
new file mode 100644
index 00000000..e27462dc
--- /dev/null
+++ b/engine/include/XCEngine/Scripting/IScriptRuntime.h
@@ -0,0 +1,52 @@
+#pragma once
+
+#include <cstdint>
+
+namespace XCEngine {
+
+namespace Components {
+class GameObject;
+class Scene;
+}
+
+namespace Scripting {
+
+class ScriptComponent;
+
+enum class ScriptLifecycleMethod {
+    Awake = 0,
+    OnEnable,
+    Start,
+    FixedUpdate,
+    Update,
+    LateUpdate,
+    OnDisable,
+    OnDestroy
+};
+
+struct ScriptRuntimeContext {
+    Components::Scene* scene = nullptr;
+    Components::GameObject* gameObject = nullptr;
+    ScriptComponent* component = nullptr;
+    uint64_t gameObjectUUID = 0;
+    uint64_t scriptComponentUUID = 0;
+};
+
+class IScriptRuntime {
+public:
+    virtual ~IScriptRuntime() = default;
+
+    virtual void OnRuntimeStart(Components::Scene* scene) = 0;
+    virtual void OnRuntimeStop(Components::Scene* scene) = 0;
+
+    virtual bool CreateScriptInstance(const ScriptRuntimeContext& context) = 0;
+    virtual void DestroyScriptInstance(const ScriptRuntimeContext& context) = 0;
+
+    virtual void InvokeMethod(
+        const ScriptRuntimeContext& context,
+        ScriptLifecycleMethod method,
+        float deltaTime) = 0;
+};
+
+} // namespace Scripting
+} // namespace XCEngine
diff --git a/engine/include/XCEngine/Scripting/NullScriptRuntime.h b/engine/include/XCEngine/Scripting/NullScriptRuntime.h
new file mode 100644
index 00000000..07c47ad0
--- /dev/null
+++ b/engine/include/XCEngine/Scripting/NullScriptRuntime.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <XCEngine/Scripting/IScriptRuntime.h>
+
+namespace XCEngine {
+namespace Scripting {
+
+class NullScriptRuntime : public IScriptRuntime {
+public:
+    void OnRuntimeStart(Components::Scene* scene) override;
+    void OnRuntimeStop(Components::Scene* scene) override;
+
+    bool CreateScriptInstance(const ScriptRuntimeContext& context) override;
+    void DestroyScriptInstance(const ScriptRuntimeContext& context) override;
+
+    void InvokeMethod(
+        const ScriptRuntimeContext& context,
+        ScriptLifecycleMethod method,
+        float deltaTime) override;
+};
+
+} // namespace Scripting
+} // namespace XCEngine
diff --git a/engine/include/XCEngine/Scripting/ScriptComponent.h b/engine/include/XCEngine/Scripting/ScriptComponent.h
index 9b5e3c5d..d1ec2f0e 100644
--- a/engine/include/XCEngine/Scripting/ScriptComponent.h
+++ b/engine/include/XCEngine/Scripting/ScriptComponent.h
@@ -36,6 +36,10 @@ public:
     const ScriptFieldStorage& GetFieldStorage() const { return m_fieldStorage; }
     void SetFieldStorage(const ScriptFieldStorage& fieldStorage) { m_fieldStorage = fieldStorage; }
 
+    void OnEnable() override;
+    void OnDisable() override;
+    void OnDestroy() override;
+
     void Serialize(std::ostream& os) const override;
     void Deserialize(std::istream& is) override;
 
diff --git a/engine/include/XCEngine/Scripting/ScriptEngine.h b/engine/include/XCEngine/Scripting/ScriptEngine.h
new file mode 100644
index 00000000..5143e014
--- /dev/null
+++ b/engine/include/XCEngine/Scripting/ScriptEngine.h
@@ -0,0 +1,88 @@
+#pragma once
+
+#include <XCEngine/Scripting/IScriptRuntime.h>
+#include <XCEngine/Scripting/NullScriptRuntime.h>
+
+#include <cstddef>
+#include <cstdint>
+#include <unordered_map>
+#include <vector>
+
+namespace XCEngine {
+namespace Scripting {
+
+class ScriptComponent;
+
+class ScriptEngine {
+public:
+    static ScriptEngine& Get();
+
+    void SetRuntime(IScriptRuntime* runtime);
+    IScriptRuntime* GetRuntime() const { return m_runtime; }
+
+    void OnRuntimeStart(Components::Scene* scene);
+    void OnRuntimeStop();
+
+    void OnFixedUpdate(float fixedDeltaTime);
+    void OnUpdate(float deltaTime);
+    void OnLateUpdate(float deltaTime);
+
+    void OnScriptComponentEnabled(ScriptComponent* component);
+    void OnScriptComponentDisabled(ScriptComponent* component);
+    void OnScriptComponentDestroyed(ScriptComponent* component);
+
+    bool IsRuntimeRunning() const { return m_runtimeRunning; }
+    Components::Scene* GetRuntimeScene() const { return m_runtimeScene; }
+
+    bool HasTrackedScriptComponent(const ScriptComponent* component) const;
+    bool HasRuntimeInstance(const ScriptComponent* component) const;
+    size_t GetTrackedScriptCount() const { return m_scriptOrder.size(); }
+
+private:
+    struct ScriptInstanceKey {
+        uint64_t gameObjectUUID = 0;
+        uint64_t scriptComponentUUID = 0;
+
+        bool operator==(const ScriptInstanceKey& other) const {
+            return gameObjectUUID == other.gameObjectUUID
+                && scriptComponentUUID == other.scriptComponentUUID;
+        }
+    };
+
+    struct ScriptInstanceKeyHasher {
+        size_t operator()(const ScriptInstanceKey& key) const;
+    };
+
+    struct ScriptInstanceState {
+        ScriptRuntimeContext context;
+        bool instanceCreated = false;
+        bool awakeCalled = false;
+        bool enabled = false;
+        bool startCalled = false;
+        bool startPending = false;
+    };
+
+    ScriptEngine() = default;
+
+    void CollectScriptComponents(Components::GameObject* gameObject);
+    ScriptInstanceState* TrackScriptComponent(ScriptComponent* component);
+    ScriptInstanceState* FindState(const ScriptComponent* component);
+    const ScriptInstanceState* FindState(const ScriptComponent* component) const;
+    void RemoveTrackedScriptComponent(const ScriptComponent* component);
+
+    bool ShouldScriptRun(const ScriptInstanceState& state) const;
+    bool EnsureScriptReady(ScriptInstanceState& state, bool invokeEnableIfNeeded);
+    void InvokeLifecycleMethod(ScriptInstanceState& state, ScriptLifecycleMethod method, float deltaTime = 0.0f);
+    void StopTrackingScript(ScriptInstanceState& state, bool runtimeStopping);
+
+    NullScriptRuntime m_nullRuntime;
+    IScriptRuntime* m_runtime = &m_nullRuntime;
+    Components::Scene* m_runtimeScene = nullptr;
+    bool m_runtimeRunning = false;
+
+    std::unordered_map<ScriptInstanceKey, ScriptInstanceState, ScriptInstanceKeyHasher> m_scriptStates;
+    std::vector<ScriptInstanceKey> m_scriptOrder;
+};
+
+} // namespace Scripting
+} // namespace XCEngine
diff --git a/engine/src/Scripting/NullScriptRuntime.cpp b/engine/src/Scripting/NullScriptRuntime.cpp
new file mode 100644
index 00000000..f946eed5
--- /dev/null
+++ b/engine/src/Scripting/NullScriptRuntime.cpp
@@ -0,0 +1,32 @@
+#include "Scripting/NullScriptRuntime.h"
+
+namespace XCEngine {
+namespace Scripting {
+
+void NullScriptRuntime::OnRuntimeStart(Components::Scene* scene) {
+    (void)scene;
+}
+
+void NullScriptRuntime::OnRuntimeStop(Components::Scene* scene) {
+    (void)scene;
+}
+
+bool NullScriptRuntime::CreateScriptInstance(const ScriptRuntimeContext& context) {
+    return context.component != nullptr;
+}
+
+void NullScriptRuntime::DestroyScriptInstance(const ScriptRuntimeContext& context) {
+    (void)context;
+}
+
+void NullScriptRuntime::InvokeMethod(
+    const ScriptRuntimeContext& context,
+    ScriptLifecycleMethod method,
+    float deltaTime) {
+    (void)context;
+    (void)method;
+    (void)deltaTime;
+}
+
+} // namespace Scripting
+} // namespace XCEngine
diff --git a/engine/src/Scripting/ScriptComponent.cpp b/engine/src/Scripting/ScriptComponent.cpp
index 8c76f9ce..24c2cd2e 100644
--- a/engine/src/Scripting/ScriptComponent.cpp
+++ b/engine/src/Scripting/ScriptComponent.cpp
@@ -1,5 +1,7 @@
 #include "Scripting/ScriptComponent.h"
 
+#include "Scripting/ScriptEngine.h"
+
 #include <random>
 #include <sstream>
 
@@ -44,6 +46,18 @@ std::string ScriptComponent::GetFullClassName() const {
     return m_namespaceName + "." + m_className;
 }
 
+void ScriptComponent::OnEnable() {
+    ScriptEngine::Get().OnScriptComponentEnabled(this);
+}
+
+void ScriptComponent::OnDisable() {
+    ScriptEngine::Get().OnScriptComponentDisabled(this);
+}
+
+void ScriptComponent::OnDestroy() {
+    ScriptEngine::Get().OnScriptComponentDestroyed(this);
+}
+
 void ScriptComponent::Serialize(std::ostream& os) const {
     os << "scriptComponentUUID=" << m_scriptComponentUUID << ";";
     os << "assembly=" << EscapeScriptString(m_assemblyName) << ";";
diff --git a/engine/src/Scripting/ScriptEngine.cpp b/engine/src/Scripting/ScriptEngine.cpp
new file mode 100644
index 00000000..7173e069
--- /dev/null
+++ b/engine/src/Scripting/ScriptEngine.cpp
@@ -0,0 +1,355 @@
+#include "Scripting/ScriptEngine.h"
+
+#include "Components/GameObject.h"
+#include "Scene/Scene.h"
+#include "Scripting/ScriptComponent.h"
+
+#include <algorithm>
+
+namespace XCEngine {
+namespace Scripting {
+
+ScriptEngine& ScriptEngine::Get() {
+    static ScriptEngine instance;
+    return instance;
+}
+
+void ScriptEngine::SetRuntime(IScriptRuntime* runtime) {
+    m_runtime = runtime ? runtime : &m_nullRuntime;
+}
+
+void ScriptEngine::OnRuntimeStart(Components::Scene* scene) {
+    OnRuntimeStop();
+
+    if (!scene) {
+        return;
+    }
+
+    m_runtimeScene = scene;
+    m_runtimeRunning = true;
+    m_runtime->OnRuntimeStart(scene);
+
+    for (Components::GameObject* root : scene->GetRootGameObjects()) {
+        CollectScriptComponents(root);
+    }
+
+    for (const ScriptInstanceKey& key : m_scriptOrder) {
+        auto it = m_scriptStates.find(key);
+        if (it == m_scriptStates.end()) {
+            continue;
+        }
+
+        ScriptInstanceState& state = it->second;
+        if (!ShouldScriptRun(state)) {
+            continue;
+        }
+
+        EnsureScriptReady(state, true);
+    }
+}
+
+void ScriptEngine::OnRuntimeStop() {
+    if (!m_runtimeRunning) {
+        m_runtimeScene = nullptr;
+        m_scriptStates.clear();
+        m_scriptOrder.clear();
+        return;
+    }
+
+    std::vector<ScriptInstanceKey> keys = m_scriptOrder;
+    for (const ScriptInstanceKey& key : keys) {
+        auto it = m_scriptStates.find(key);
+        if (it != m_scriptStates.end()) {
+            StopTrackingScript(it->second, true);
+        }
+    }
+
+    Components::Scene* stoppedScene = m_runtimeScene;
+    m_scriptStates.clear();
+    m_scriptOrder.clear();
+    m_runtimeRunning = false;
+    m_runtimeScene = nullptr;
+    m_runtime->OnRuntimeStop(stoppedScene);
+}
+
+void ScriptEngine::OnFixedUpdate(float fixedDeltaTime) {
+    if (!m_runtimeRunning) {
+        return;
+    }
+
+    for (const ScriptInstanceKey& key : m_scriptOrder) {
+        auto it = m_scriptStates.find(key);
+        if (it == m_scriptStates.end()) {
+            continue;
+        }
+
+        ScriptInstanceState& state = it->second;
+        if (!ShouldScriptRun(state) || !EnsureScriptReady(state, true) || !state.enabled) {
+            continue;
+        }
+
+        InvokeLifecycleMethod(state, ScriptLifecycleMethod::FixedUpdate, fixedDeltaTime);
+    }
+}
+
+void ScriptEngine::OnUpdate(float deltaTime) {
+    if (!m_runtimeRunning) {
+        return;
+    }
+
+    for (const ScriptInstanceKey& key : m_scriptOrder) {
+        auto it = m_scriptStates.find(key);
+        if (it == m_scriptStates.end()) {
+            continue;
+        }
+
+        ScriptInstanceState& state = it->second;
+        if (!ShouldScriptRun(state) || !EnsureScriptReady(state, true) || !state.enabled) {
+            continue;
+        }
+
+        if (state.startPending && !state.startCalled) {
+            InvokeLifecycleMethod(state, ScriptLifecycleMethod::Start);
+            state.startCalled = true;
+            state.startPending = false;
+        }
+
+        InvokeLifecycleMethod(state, ScriptLifecycleMethod::Update, deltaTime);
+    }
+}
+
+void ScriptEngine::OnLateUpdate(float deltaTime) {
+    if (!m_runtimeRunning) {
+        return;
+    }
+
+    for (const ScriptInstanceKey& key : m_scriptOrder) {
+        auto it = m_scriptStates.find(key);
+        if (it == m_scriptStates.end()) {
+            continue;
+        }
+
+        ScriptInstanceState& state = it->second;
+        if (!ShouldScriptRun(state) || !EnsureScriptReady(state, true) || !state.enabled) {
+            continue;
+        }
+
+        InvokeLifecycleMethod(state, ScriptLifecycleMethod::LateUpdate, deltaTime);
+    }
+}
+
+void ScriptEngine::OnScriptComponentEnabled(ScriptComponent* component) {
+    if (!m_runtimeRunning || !component) {
+        return;
+    }
+
+    ScriptInstanceState* state = TrackScriptComponent(component);
+    if (!state) {
+        return;
+    }
+
+    if (ShouldScriptRun(*state)) {
+        EnsureScriptReady(*state, true);
+    }
+}
+
+void ScriptEngine::OnScriptComponentDisabled(ScriptComponent* component) {
+    if (!m_runtimeRunning || !component) {
+        return;
+    }
+
+    ScriptInstanceState* state = FindState(component);
+    if (!state || !state->enabled) {
+        return;
+    }
+
+    InvokeLifecycleMethod(*state, ScriptLifecycleMethod::OnDisable);
+    state->enabled = false;
+}
+
+void ScriptEngine::OnScriptComponentDestroyed(ScriptComponent* component) {
+    if (!m_runtimeRunning || !component) {
+        return;
+    }
+
+    ScriptInstanceState* state = FindState(component);
+    if (!state) {
+        return;
+    }
+
+    StopTrackingScript(*state, false);
+}
+
+bool ScriptEngine::HasTrackedScriptComponent(const ScriptComponent* component) const {
+    return FindState(component) != nullptr;
+}
+
+bool ScriptEngine::HasRuntimeInstance(const ScriptComponent* component) const {
+    const ScriptInstanceState* state = FindState(component);
+    return state && state->instanceCreated;
+}
+
+size_t ScriptEngine::ScriptInstanceKeyHasher::operator()(const ScriptInstanceKey& key) const {
+    const size_t h1 = std::hash<uint64_t>{}(key.gameObjectUUID);
+    const size_t h2 = std::hash<uint64_t>{}(key.scriptComponentUUID);
+    return h1 ^ (h2 + 0x9e3779b97f4a7c15ULL + (h1 << 6) + (h1 >> 2));
+}
+
+void ScriptEngine::CollectScriptComponents(Components::GameObject* gameObject) {
+    if (!gameObject) {
+        return;
+    }
+
+    for (ScriptComponent* component : gameObject->GetComponents<ScriptComponent>()) {
+        TrackScriptComponent(component);
+    }
+
+    for (Components::GameObject* child : gameObject->GetChildren()) {
+        CollectScriptComponents(child);
+    }
+}
+
+ScriptEngine::ScriptInstanceState* ScriptEngine::TrackScriptComponent(ScriptComponent* component) {
+    if (!component || !component->GetGameObject()) {
+        return nullptr;
+    }
+
+    const ScriptInstanceKey key{
+        component->GetGameObject()->GetUUID(),
+        component->GetScriptComponentUUID()
+    };
+
+    auto it = m_scriptStates.find(key);
+    if (it != m_scriptStates.end()) {
+        it->second.context.scene = component->GetScene();
+        it->second.context.gameObject = component->GetGameObject();
+        it->second.context.component = component;
+        it->second.context.gameObjectUUID = component->GetGameObject()->GetUUID();
+        it->second.context.scriptComponentUUID = component->GetScriptComponentUUID();
+        return &it->second;
+    }
+
+    ScriptInstanceState state;
+    state.context.scene = component->GetScene();
+    state.context.gameObject = component->GetGameObject();
+    state.context.component = component;
+    state.context.gameObjectUUID = component->GetGameObject()->GetUUID();
+    state.context.scriptComponentUUID = component->GetScriptComponentUUID();
+
+    auto [insertedIt, inserted] = m_scriptStates.emplace(key, std::move(state));
+    if (inserted) {
+        m_scriptOrder.push_back(key);
+    }
+
+    return &insertedIt->second;
+}
+
+ScriptEngine::ScriptInstanceState* ScriptEngine::FindState(const ScriptComponent* component) {
+    if (!component || !component->GetGameObject()) {
+        return nullptr;
+    }
+
+    const ScriptInstanceKey key{
+        component->GetGameObject()->GetUUID(),
+        component->GetScriptComponentUUID()
+    };
+
+    auto it = m_scriptStates.find(key);
+    return it != m_scriptStates.end() ? &it->second : nullptr;
+}
+
+const ScriptEngine::ScriptInstanceState* ScriptEngine::FindState(const ScriptComponent* component) const {
+    if (!component || !component->GetGameObject()) {
+        return nullptr;
+    }
+
+    const ScriptInstanceKey key{
+        component->GetGameObject()->GetUUID(),
+        component->GetScriptComponentUUID()
+    };
+
+    auto it = m_scriptStates.find(key);
+    return it != m_scriptStates.end() ? &it->second : nullptr;
+}
+
+void ScriptEngine::RemoveTrackedScriptComponent(const ScriptComponent* component) {
+    if (!component || !component->GetGameObject()) {
+        return;
+    }
+
+    const ScriptInstanceKey key{
+        component->GetGameObject()->GetUUID(),
+        component->GetScriptComponentUUID()
+    };
+
+    m_scriptStates.erase(key);
+    m_scriptOrder.erase(
+        std::remove(m_scriptOrder.begin(), m_scriptOrder.end(), key),
+        m_scriptOrder.end());
+}
+
+bool ScriptEngine::ShouldScriptRun(const ScriptInstanceState& state) const {
+    return m_runtimeRunning
+        && state.context.scene == m_runtimeScene
+        && state.context.scene != nullptr
+        && state.context.scene->IsActive()
+        && state.context.gameObject != nullptr
+        && state.context.gameObject->IsActiveInHierarchy()
+        && state.context.component != nullptr
+        && state.context.component->IsEnabled()
+        && state.context.component->HasScriptClass();
+}
+
+bool ScriptEngine::EnsureScriptReady(ScriptInstanceState& state, bool invokeEnableIfNeeded) {
+    if (!state.context.component || !state.context.gameObject || !state.context.scene || !state.context.component->HasScriptClass()) {
+        return false;
+    }
+
+    if (!state.instanceCreated) {
+        if (!m_runtime->CreateScriptInstance(state.context)) {
+            return false;
+        }
+        state.instanceCreated = true;
+    }
+
+    if (!state.awakeCalled) {
+        InvokeLifecycleMethod(state, ScriptLifecycleMethod::Awake);
+        state.awakeCalled = true;
+    }
+
+    if (invokeEnableIfNeeded && !state.enabled && ShouldScriptRun(state)) {
+        InvokeLifecycleMethod(state, ScriptLifecycleMethod::OnEnable);
+        state.enabled = true;
+        if (!state.startCalled) {
+            state.startPending = true;
+        }
+    }
+
+    return true;
+}
+
+void ScriptEngine::InvokeLifecycleMethod(ScriptInstanceState& state, ScriptLifecycleMethod method, float deltaTime) {
+    m_runtime->InvokeMethod(state.context, method, deltaTime);
+}
+
+void ScriptEngine::StopTrackingScript(ScriptInstanceState& state, bool runtimeStopping) {
+    if (state.enabled) {
+        InvokeLifecycleMethod(state, ScriptLifecycleMethod::OnDisable);
+        state.enabled = false;
+    }
+
+    if (state.instanceCreated) {
+        InvokeLifecycleMethod(state, ScriptLifecycleMethod::OnDestroy);
+        m_runtime->DestroyScriptInstance(state.context);
+        state.instanceCreated = false;
+    }
+
+    state.startPending = false;
+
+    if (!runtimeStopping) {
+        RemoveTrackedScriptComponent(state.context.component);
+    }
+}
+
+} // namespace Scripting
+} // namespace XCEngine
diff --git a/tests/scripting/CMakeLists.txt b/tests/scripting/CMakeLists.txt
index 966d559e..c3d9ba6a 100644
--- a/tests/scripting/CMakeLists.txt
+++ b/tests/scripting/CMakeLists.txt
@@ -5,6 +5,7 @@ project(XCEngine_ScriptingTests)
 set(SCRIPTING_TEST_SOURCES
     test_script_field_storage.cpp
     test_script_component.cpp
+    test_script_engine.cpp
 )
 
 add_executable(scripting_tests ${SCRIPTING_TEST_SOURCES})
diff --git a/tests/scripting/test_script_engine.cpp b/tests/scripting/test_script_engine.cpp
new file mode 100644
index 00000000..797a452b
--- /dev/null
+++ b/tests/scripting/test_script_engine.cpp
@@ -0,0 +1,239 @@
+#include <gtest/gtest.h>
+
+#include <XCEngine/Scene/Scene.h>
+#include <XCEngine/Scripting/IScriptRuntime.h>
+#include <XCEngine/Scripting/ScriptComponent.h>
+#include <XCEngine/Scripting/ScriptEngine.h>
+
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+using namespace XCEngine::Components;
+using namespace XCEngine::Scripting;
+
+namespace {
+
+std::string LifecycleMethodToString(ScriptLifecycleMethod method) {
+    switch (method) {
+        case ScriptLifecycleMethod::Awake: return "Awake";
+        case ScriptLifecycleMethod::OnEnable: return "OnEnable";
+        case ScriptLifecycleMethod::Start: return "Start";
+        case ScriptLifecycleMethod::FixedUpdate: return "FixedUpdate";
+        case ScriptLifecycleMethod::Update: return "Update";
+        case ScriptLifecycleMethod::LateUpdate: return "LateUpdate";
+        case ScriptLifecycleMethod::OnDisable: return "OnDisable";
+        case ScriptLifecycleMethod::OnDestroy: return "OnDestroy";
+    }
+
+    return "Unknown";
+}
+
+class FakeScriptRuntime : public IScriptRuntime {
+public:
+    void OnRuntimeStart(Scene* scene) override {
+        events.push_back("RuntimeStart:" + (scene ? scene->GetName() : std::string("null")));
+    }
+
+    void OnRuntimeStop(Scene* scene) override {
+        events.push_back("RuntimeStop:" + (scene ? scene->GetName() : std::string("null")));
+    }
+
+    bool CreateScriptInstance(const ScriptRuntimeContext& context) override {
+        events.push_back("Create:" + Describe(context));
+        return context.component != nullptr;
+    }
+
+    void DestroyScriptInstance(const ScriptRuntimeContext& context) override {
+        events.push_back("Destroy:" + Describe(context));
+    }
+
+    void InvokeMethod(
+        const ScriptRuntimeContext& context,
+        ScriptLifecycleMethod method,
+        float deltaTime) override {
+        (void)deltaTime;
+        events.push_back(LifecycleMethodToString(method) + ":" + Describe(context));
+    }
+
+    void Clear() {
+        events.clear();
+    }
+
+    std::vector<std::string> events;
+
+private:
+    static std::string Describe(const ScriptRuntimeContext& context) {
+        const std::string gameObjectName = context.gameObject ? context.gameObject->GetName() : "null";
+        const std::string className = context.component ? context.component->GetFullClassName() : "null";
+        return gameObjectName + ":" + className;
+    }
+};
+
+class ScriptEngineTest : public ::testing::Test {
+protected:
+    void SetUp() override {
+        engine = &ScriptEngine::Get();
+        engine->OnRuntimeStop();
+        engine->SetRuntime(&runtime);
+    }
+
+    void TearDown() override {
+        engine->OnRuntimeStop();
+        engine->SetRuntime(nullptr);
+        scene.reset();
+    }
+
+    ScriptComponent* AddScriptComponent(GameObject* gameObject, const std::string& namespaceName, const std::string& className) {
+        ScriptComponent* component = gameObject->AddComponent<ScriptComponent>();
+        component->SetScriptClass("GameScripts", namespaceName, className);
+        return component;
+    }
+
+    Scene* CreateScene(const std::string& sceneName) {
+        scene = std::make_unique<Scene>(sceneName);
+        return scene.get();
+    }
+
+    ScriptEngine* engine = nullptr;
+    FakeScriptRuntime runtime;
+    std::unique_ptr<Scene> scene;
+};
+
+TEST_F(ScriptEngineTest, RuntimeStartTracksActiveScriptsAndInvokesAwakeThenOnEnable) {
+    Scene* runtimeScene = CreateScene("RuntimeScene");
+    GameObject* host = runtimeScene->CreateGameObject("Host");
+    ScriptComponent* component = AddScriptComponent(host, "Gameplay", "PlayerController");
+
+    engine->OnRuntimeStart(runtimeScene);
+
+    EXPECT_TRUE(engine->IsRuntimeRunning());
+    EXPECT_EQ(engine->GetRuntimeScene(), runtimeScene);
+    EXPECT_EQ(engine->GetTrackedScriptCount(), 1u);
+    EXPECT_TRUE(engine->HasTrackedScriptComponent(component));
+    EXPECT_TRUE(engine->HasRuntimeInstance(component));
+
+    const std::vector<std::string> expected = {
+        "RuntimeStart:RuntimeScene",
+        "Create:Host:Gameplay.PlayerController",
+        "Awake:Host:Gameplay.PlayerController",
+        "OnEnable:Host:Gameplay.PlayerController"
+    };
+    EXPECT_EQ(runtime.events, expected);
+}
+
+TEST_F(ScriptEngineTest, UpdateInvokesStartOnlyOnceAndRunsPerFrameMethods) {
+    Scene* runtimeScene = CreateScene("RuntimeScene");
+    GameObject* host = runtimeScene->CreateGameObject("Host");
+    AddScriptComponent(host, "Gameplay", "Mover");
+
+    engine->OnRuntimeStart(runtimeScene);
+    runtime.Clear();
+
+    engine->OnUpdate(0.016f);
+    engine->OnFixedUpdate(0.02f);
+    engine->OnUpdate(0.016f);
+    engine->OnLateUpdate(0.016f);
+
+    const std::vector<std::string> expected = {
+        "Start:Host:Gameplay.Mover",
+        "Update:Host:Gameplay.Mover",
+        "FixedUpdate:Host:Gameplay.Mover",
+        "Update:Host:Gameplay.Mover",
+        "LateUpdate:Host:Gameplay.Mover"
+    };
+    EXPECT_EQ(runtime.events, expected);
+}
+
+TEST_F(ScriptEngineTest, InactiveObjectDefersCreationUntilActivated) {
+    Scene* runtimeScene = CreateScene("RuntimeScene");
+    GameObject* host = runtimeScene->CreateGameObject("Host");
+    ScriptComponent* component = AddScriptComponent(host, "Gameplay", "SpawnedLater");
+    host->SetActive(false);
+
+    engine->OnRuntimeStart(runtimeScene);
+
+    ASSERT_EQ(engine->GetTrackedScriptCount(), 1u);
+    EXPECT_TRUE(engine->HasTrackedScriptComponent(component));
+    EXPECT_FALSE(engine->HasRuntimeInstance(component));
+    ASSERT_EQ(runtime.events.size(), 1u);
+    EXPECT_EQ(runtime.events[0], "RuntimeStart:RuntimeScene");
+
+    runtime.Clear();
+    host->SetActive(true);
+    engine->OnUpdate(0.016f);
+
+    const std::vector<std::string> expected = {
+        "Create:Host:Gameplay.SpawnedLater",
+        "Awake:Host:Gameplay.SpawnedLater",
+        "OnEnable:Host:Gameplay.SpawnedLater",
+        "Start:Host:Gameplay.SpawnedLater",
+        "Update:Host:Gameplay.SpawnedLater"
+    };
+    EXPECT_EQ(runtime.events, expected);
+}
+
+TEST_F(ScriptEngineTest, RuntimeStopInvokesDisableDestroyAndRuntimeStop) {
+    Scene* runtimeScene = CreateScene("RuntimeScene");
+    GameObject* host = runtimeScene->CreateGameObject("Host");
+    AddScriptComponent(host, "Gameplay", "ShutdownWatcher");
+
+    engine->OnRuntimeStart(runtimeScene);
+    runtime.Clear();
+
+    engine->OnRuntimeStop();
+
+    const std::vector<std::string> expected = {
+        "OnDisable:Host:Gameplay.ShutdownWatcher",
+        "OnDestroy:Host:Gameplay.ShutdownWatcher",
+        "Destroy:Host:Gameplay.ShutdownWatcher",
+        "RuntimeStop:RuntimeScene"
+    };
+    EXPECT_EQ(runtime.events, expected);
+    EXPECT_FALSE(engine->IsRuntimeRunning());
+    EXPECT_EQ(engine->GetRuntimeScene(), nullptr);
+    EXPECT_EQ(engine->GetTrackedScriptCount(), 0u);
+}
+
+TEST_F(ScriptEngineTest, ReEnablingScriptDoesNotInvokeStartTwice) {
+    Scene* runtimeScene = CreateScene("RuntimeScene");
+    GameObject* host = runtimeScene->CreateGameObject("Host");
+    ScriptComponent* component = AddScriptComponent(host, "Gameplay", "ToggleWatcher");
+
+    engine->OnRuntimeStart(runtimeScene);
+    engine->OnUpdate(0.016f);
+    runtime.Clear();
+
+    component->SetEnabled(false);
+    component->SetEnabled(true);
+    engine->OnUpdate(0.016f);
+
+    const std::vector<std::string> expected = {
+        "OnDisable:Host:Gameplay.ToggleWatcher",
+        "OnEnable:Host:Gameplay.ToggleWatcher",
+        "Update:Host:Gameplay.ToggleWatcher"
+    };
+    EXPECT_EQ(runtime.events, expected);
+}
+
+TEST_F(ScriptEngineTest, DestroyingGameObjectWhileRuntimeRunningDestroysTrackedScript) {
+    Scene* runtimeScene = CreateScene("RuntimeScene");
+    GameObject* host = runtimeScene->CreateGameObject("Host");
+    AddScriptComponent(host, "Gameplay", "DestroyWatcher");
+
+    engine->OnRuntimeStart(runtimeScene);
+    runtime.Clear();
+
+    runtimeScene->DestroyGameObject(host);
+
+    const std::vector<std::string> expected = {
+        "OnDisable:Host:Gameplay.DestroyWatcher",
+        "OnDestroy:Host:Gameplay.DestroyWatcher",
+        "Destroy:Host:Gameplay.DestroyWatcher"
+    };
+    EXPECT_EQ(runtime.events, expected);
+    EXPECT_EQ(engine->GetTrackedScriptCount(), 0u);
+}
+
+} // namespace