diff --git a/.ci/docker/requirements-ci.txt b/.ci/docker/requirements-ci.txt
index c82882d56e6..a29232c6386 100644
--- a/.ci/docker/requirements-ci.txt
+++ b/.ci/docker/requirements-ci.txt
@@ -11,6 +11,7 @@ zstd==1.5.5.1
 pandas>=2.2.2; python_version >= '3.10'
 pytest==7.2.0
 pytest-cov==4.1.0
+pytest-timeout==2.2.0
 expecttest==0.1.6
 hypothesis==6.84.2
 parameterized==0.9.0
diff --git a/.ci/scripts/unittest-macos-cmake.sh b/.ci/scripts/unittest-macos-cmake.sh
index 43eb1f21c3c..8c1d5df0879 100755
--- a/.ci/scripts/unittest-macos-cmake.sh
+++ b/.ci/scripts/unittest-macos-cmake.sh
@@ -12,8 +12,15 @@ set -eux
 export TORCHINDUCTOR_CACHE_DIR="$(mktemp -d "${RUNNER_TEMP:-/tmp}/torchinductor_cache_XXXXXX")"
 trap 'rm -rf "${TORCHINDUCTOR_CACHE_DIR}"' EXIT
 
-# Run pytest with coverage
-${CONDA_RUN} pytest -n auto --cov=./ --cov-report=xml
+# EXPERIMENT: drop xdist (`-n 1`) on macOS to test whether AOTI hangs are
+# caused by parallel-worker contention (clang/ld, dlopen lock, libomp
+# oversubscription) rather than a true deadlock. AOTI skips removed so we
+# can observe whether the previously-hung tests now pass serially.
+# --timeout surfaces hung tests with a thread dump and faulthandler_timeout
+# periodically dumps every worker's threads while tests are still running.
+${CONDA_RUN} pytest -n 1 --cov=./ --cov-report=xml \
+  --timeout=1500 --timeout-method=thread \
+  -o faulthandler_timeout=180
 # Run gtest
 LLVM_PROFDATA="xcrun llvm-profdata" LLVM_COV="xcrun llvm-cov" \
 ${CONDA_RUN} test/run_oss_cpp_tests.sh
diff --git a/.github/workflows/_unittest.yml b/.github/workflows/_unittest.yml
index 15c87bd79e4..e63a6bc518c 100644
--- a/.github/workflows/_unittest.yml
+++ b/.github/workflows/_unittest.yml
@@ -49,6 +49,7 @@ jobs:
       python-version: '3.11'
       submodules: 'recursive'
       ref: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.sha }}
+      timeout: 90
       script: |
         set -eux
         # This is needed to get the prebuilt PyTorch wheel from S3