diff --git a/studio/backend/main.py b/studio/backend/main.py
index de468c183a..e957c668e3 100644
--- a/studio/backend/main.py
+++ b/studio/backend/main.py
@@ -16,6 +16,7 @@ from datetime import datetime
 from routes import training_router, models_router, inference_router, datasets_router, auth_router
 from auth import storage
 from utils.hardware import detect_hardware
+import utils.hardware.hardware as _hw_module
 
 UNSLOTH_CACHE_DIR = Path(__file__).parent / "unsloth_compiled_cache"
 
@@ -36,7 +37,8 @@ async def lifespan(app: FastAPI):
         print("This token can only be used once.")
         print("=" * 60 + "\n")
     yield
-    # Cleanup: remove Unsloth compiled cache on shutdown
+    # Cleanup
+    _hw_module.DEVICE = None
     shutil.rmtree(UNSLOTH_CACHE_DIR, ignore_errors=True)
 
 
diff --git a/studio/backend/tests/test_utils.py b/studio/backend/tests/test_utils.py
index ffc3599474..1c2a80b8bd 100644
--- a/studio/backend/tests/test_utils.py
+++ b/studio/backend/tests/test_utils.py
@@ -29,12 +29,14 @@ needs_torch = pytest.mark.skipif(not HAS_TORCH, reason="PyTorch not installed")
 
 from utils.hardware import (
     get_device,
+    detect_hardware,
     is_apple_silicon,
     clear_gpu_cache,
     get_gpu_memory_info,
     log_gpu_memory,
     DeviceType,
 )
+import utils.hardware.hardware as _hw_module
 from utils.utils import format_error_message
 
 
@@ -50,11 +52,25 @@ def _actual_device() -> str:
     return "cpu"
 
 
+def _reset_and_detect():
+    """Reset the cached DEVICE global and re-run detection."""
+    _hw_module.DEVICE = None
+    return detect_hardware()
+
+
 # ========== get_device() ==========
 
 class TestGetDevice:
     """Tests for get_device() — should agree with the real hardware."""
 
+    def setup_method(self):
+        """Save DEVICE before each test."""
+        self._saved_device = _hw_module.DEVICE
+
+    def teardown_method(self):
+        """Restore DEVICE after each test so mocked tests don't poison later ones."""
+        _hw_module.DEVICE = self._saved_device
+
     def test_returns_valid_device_type(self):
         result = get_device()
         assert result in (DeviceType.CUDA, DeviceType.MPS, DeviceType.CPU)
@@ -67,7 +83,7 @@ class TestGetDevice:
     @needs_torch
     def test_returns_cuda_when_cuda_available(self):
         with patch("torch.cuda.is_available", return_value=True):
-            assert get_device() == DeviceType.CUDA
+            assert _reset_and_detect() == DeviceType.CUDA
 
     @needs_torch
     def test_returns_mps_when_only_mps_available(self):
@@ -75,13 +91,13 @@ class TestGetDevice:
         mock_mps.is_available.return_value = True
         with patch("torch.cuda.is_available", return_value=False), \
              patch.object(torch.backends, "mps", mock_mps, create=True):
-            assert get_device() == DeviceType.MPS
+            assert _reset_and_detect() == DeviceType.MPS
 
     @needs_torch
     def test_returns_cpu_when_nothing_available(self):
         with patch("torch.cuda.is_available", return_value=False), \
              patch("builtins.hasattr", side_effect=lambda obj, name: False if name == "mps" else hasattr(obj, name)):
-            assert get_device() == DeviceType.CPU
+            assert _reset_and_detect() == DeviceType.CPU
 
 
 # ========== is_apple_silicon() ==========