diff --git a/.github/workflows/build-test-package-python-cuda.yml b/.github/workflows/build-test-package-python-cuda.yml
index d31a410..5468a1e 100644
--- a/.github/workflows/build-test-package-python-cuda.yml
+++ b/.github/workflows/build-test-package-python-cuda.yml
@@ -233,4 +233,14 @@ jobs:
         pip install cupy-cuda12x torch
 
         pip install pytest
-        pytest $GITHUB_WORKSPACE/test/*.py
+
+        # Run tests with warning detection.
+        # SWIG < 4.4 triggers the Py_LIMITED_API "builtin type swig…" warning when
+        # Python runs with -Walways; pytest enables that behavior, so we ignore it.
+        stderr_log=$(mktemp)
+        pytest $GITHUB_WORKSPACE/test/*.py -vv -s -W "ignore:builtin type swig" 2> "$stderr_log"
+        if grep -q "Warning" "$stderr_log"; then
+          echo "Warnings found in stderr, failing the build"
+          cat "$stderr_log"
+          exit 1
+        fi