diff --git a/OptiScaler/hooks/D3D12_Hooks.cpp b/OptiScaler/hooks/D3D12_Hooks.cpp
index 3b757be..05fc194 100644
--- a/OptiScaler/hooks/D3D12_Hooks.cpp
+++ b/OptiScaler/hooks/D3D12_Hooks.cpp
@@ -2217,11 +2217,20 @@ static HRESULT hkD3D12GetInterface(REFCLSID rclsid, REFIID riid, void** ppvDebug
     return result;
 }
 
+// Device discovery and NGX initialization can overlap. Installing d4r's
+// command hooks can also create a device and re-enter this function. Never
+// overwrite live Detours trampolines from a second installation attempt.
+static std::recursive_mutex deviceHookMutex;
+static bool deviceHookInstalling = false;
 static void HookToDevice(ID3D12Device* InDevice)
 {
-    if (o_CreateSampler != nullptr || InDevice == nullptr)
+    std::lock_guard<std::recursive_mutex> lock(deviceHookMutex);
+    if (o_CreateSampler != nullptr || InDevice == nullptr || deviceHookInstalling)
         return;
 
+    deviceHookInstalling = true;
+    struct InstallationGuard { ~InstallationGuard() { deviceHookInstalling = false; } } installationGuard;
+
     LOG_DEBUG("Dx12");
 
     // Get the vtable pointer
@@ -2334,6 +2343,7 @@ static void HookToDevice(ID3D12Device* InDevice)
 
 static void UnhookDevice()
 {
+    std::lock_guard<std::recursive_mutex> lock(deviceHookMutex);
     LOG_FUNC();
 
     DetourTransactionBegin();