diff --git a/.github/workflows/tier1-benchmark.yml b/.github/workflows/tier1-benchmark.yml
index ddf449e..b04460d 100644
--- a/.github/workflows/tier1-benchmark.yml
+++ b/.github/workflows/tier1-benchmark.yml
@@ -223,7 +223,7 @@ jobs:
             --memory=4Gi \
             --cpu=2 \
             --service-account="$SERVICE_ACCOUNT" \
-            --set-env-vars="INTERACTION_DB_REPO=${INTERACTION_DB_REPO},INTERACTION_DB_TAG=${INTERACTION_DB_TAG},INTERACTION_DB_SHA256=${INTERACTION_DB_SHA256}" \
+            --set-env-vars="INTERACTION_DB_REPO=${INTERACTION_DB_REPO},INTERACTION_DB_TAG=${INTERACTION_DB_TAG},INTERACTION_DB_SHA256=${INTERACTION_DB_SHA256},BENCHMARK_FORCE_OS_EXIT=1" \
             --set-secrets="HF_TOKEN=HF_TOKEN:latest" \
             --args="$ARGS"
 
diff --git a/eval/run_benchmark.py b/eval/run_benchmark.py
index f2085a9..df6e075 100644
--- a/eval/run_benchmark.py
+++ b/eval/run_benchmark.py
@@ -580,5 +580,14 @@ def main() -> int:
     return asyncio.run(_main_async(args))
 
 
+def exit_process(exit_code: int) -> None:
+    """Exit normally, or force-exit in Cloud Run if upload libraries keep threads alive."""
+    if os.environ.get("BENCHMARK_FORCE_OS_EXIT") == "1":
+        sys.stdout.flush()
+        sys.stderr.flush()
+        os._exit(exit_code)
+    raise SystemExit(exit_code)
+
+
 if __name__ == "__main__":
-    raise SystemExit(main())
+    exit_process(main())
diff --git a/tests/eval/test_run_benchmark.py b/tests/eval/test_run_benchmark.py
index f9efbc2..ed5d702 100644
--- a/tests/eval/test_run_benchmark.py
+++ b/tests/eval/test_run_benchmark.py
@@ -7,6 +7,31 @@
 from eval import run_benchmark
 
 
+def test_exit_process_uses_system_exit_by_default(monkeypatch):
+    monkeypatch.delenv("BENCHMARK_FORCE_OS_EXIT", raising=False)
+
+    with pytest.raises(SystemExit) as exc:
+        run_benchmark.exit_process(3)
+
+    assert exc.value.code == 3
+
+
+def test_exit_process_can_force_os_exit_for_cloud(monkeypatch):
+    calls = []
+
+    def fake_os_exit(code):
+        calls.append(code)
+        raise RuntimeError("forced exit")
+
+    monkeypatch.setenv("BENCHMARK_FORCE_OS_EXIT", "1")
+    monkeypatch.setattr(run_benchmark.os, "_exit", fake_os_exit)
+
+    with pytest.raises(RuntimeError, match="forced exit"):
+        run_benchmark.exit_process(0)
+
+    assert calls == [0]
+
+
 @pytest.mark.asyncio
 async def test_run_benchmark_captures_trace_metrics_and_artifacts(monkeypatch, tmp_path: Path):
     records = [
diff --git a/tests/test_tier1_benchmark_workflow.py b/tests/test_tier1_benchmark_workflow.py
index a2c31a9..dfd1552 100644
--- a/tests/test_tier1_benchmark_workflow.py
+++ b/tests/test_tier1_benchmark_workflow.py
@@ -28,6 +28,7 @@ def test_tier1_benchmark_workflow_contract():
     assert "INTERACTION_DB_REPO" in workflow
     assert "INTERACTION_DB_TAG" in workflow
     assert "INTERACTION_DB_SHA256" in workflow
+    assert "BENCHMARK_FORCE_OS_EXIT=1" in workflow
     assert 'tr -d "\\r\\n"' in workflow
     assert 'INTERACTION_DB_REPO="$(printf' in workflow
     assert 'INTERACTION_DB_TAG="$(printf' in workflow