diff --git a/dsv4/kernels/cuda/loader.py b/dsv4/kernels/cuda/loader.py
index f5c380bb..6d0295e3 100644
--- a/dsv4/kernels/cuda/loader.py
+++ b/dsv4/kernels/cuda/loader.py
@@ -10,6 +10,7 @@ Usage:
     result = mod.quantize_nvfp4_from_buffer(x, divisor)
 """
 import os
+import time
 import hashlib
 import torch
 from torch.utils.cpp_extension import load
@@ -18,6 +19,34 @@ _KERNEL_DIR = os.path.dirname(os.path.abspath(__file__))
 _CACHE_DIR = os.path.join(_KERNEL_DIR, "_build_cache")
 _LOADED_MODULES = {}
 
+# Maximum age of a stale lock file before we remove it (seconds).
+# torch.utils.cpp_extension.load creates a lock file during compilation.
+# If the process is killed during compilation, the lock remains and the
+# next process spins forever polling it. This timeout prevents that.
+_STALE_LOCK_TIMEOUT_S = 600  # 10 minutes
+
+
+def _cleanup_stale_lock():
+    """Remove stale lock files from the build cache directory.
+    
+    torch.utils.cpp_extension.load creates a 'lock' file in the build
+    directory during compilation. If the compiling process is killed
+    (OOM, timeout, user interrupt), the lock file is never removed and
+    subsequent processes spin forever waiting for it.
+    
+    This function checks if a lock file exists and is older than
+    _STALE_LOCK_TIMEOUT_S. If so, it removes it.
+    """
+    lock_path = os.path.join(_CACHE_DIR, "lock")
+    if os.path.exists(lock_path):
+        try:
+            lock_age = time.time() - os.path.getmtime(lock_path)
+            if lock_age > _STALE_LOCK_TIMEOUT_S:
+                os.remove(lock_path)
+                print(f"[loader] Removed stale lock file (age={lock_age:.0f}s)", flush=True)
+        except OSError:
+            pass  # Lock was removed between exists() and remove()
+
 
 def get_cuda_module(name, sources, extra_cuda_cflags=None):
     """Load a CUDA kernel module, compiling once and caching forever.
@@ -33,6 +62,9 @@ def get_cuda_module(name, sources, extra_cuda_cflags=None):
     if name in _LOADED_MODULES:
         return _LOADED_MODULES[name]
     
+    # Clean up stale lock files from crashed previous compilations
+    _cleanup_stale_lock()
+    
     source_paths = [os.path.join(_KERNEL_DIR, s) for s in sources]
     
     # Build a cache key from source file contents + compile flags