--- a/ccimport/buildtools/writer.py	2026-06-17 09:38:31.525445108 +0200
+++ b/ccimport/buildtools/writer.py	2026-06-17 09:38:31.566120489 +0200
@@ -7,7 +7,16 @@
 from pathlib import Path
 from typing import Any, Dict, List, Optional, Tuple, Type, Union
 
-from ninja.ninja_syntax import Writer
+try:
+    from ninja.ninja_syntax import Writer
+except ImportError:  # ninja_syntax only drives JIT builds, not prebuilt-op
+    # imports (e.g. spconv-cuXXX). Stub the base so BaseWritter still defines;
+    # actually building without python 'ninja' then fails clearly.
+    class Writer:  # type: ignore
+        def __init__(self, *args, **kwargs):
+            raise RuntimeError(
+                "ccimport JIT build needs the python 'ninja' package "
+                "(ninja_syntax), which is not installed")
 from ccimport import compat
 from ccimport.constants import get_compiler_map, CXX, CUDACXX, HIPCXX
 from ccimport.buildmeta import BuildMeta