diff --git a/simpleaudit/_event_loop.py b/simpleaudit/_event_loop.py
new file mode 100644
index 0000000..cfb2109
--- /dev/null
+++ b/simpleaudit/_event_loop.py
@@ -0,0 +1,40 @@
+"""Running SimpleAudit's coroutines from synchronous code."""
+
+import asyncio
+from typing import Any, Coroutine, Dict
+
+
+def _is_stale_client_close(context: Dict[str, Any]) -> bool:
+    """Is this an HTTP client from an earlier run, closed on a loop that is gone?
+
+    Each sync ``run()`` gets its own event loop. The OpenAI SDK's async client sits
+    in a reference cycle, so one from an earlier run can be garbage-collected while
+    a later run's loop is running. Its ``__del__`` then schedules ``aclose()`` on
+    that loop, for connections that were opened on the earlier, closed one, and the
+    task fails with "Event loop is closed". Nothing is lost: those connections ended
+    with their loop. But asyncio prints the traceback as "Task exception was never
+    retrieved", which reads like a failed audit.
+
+    any-llm has no public way to close a provider's client, so the client cannot be
+    closed before its loop ends; until it does, the message is dropped here.
+    """
+    exception = context.get("exception")
+    if not isinstance(exception, RuntimeError) or str(exception) != "Event loop is closed":
+        return False
+    task = context.get("future") or context.get("task")
+    get_coro = getattr(task, "get_coro", None)
+    coro = get_coro() if get_coro is not None else None
+    return getattr(coro, "__qualname__", "").endswith("AsyncClient.aclose")
+
+
+def _exception_handler(loop: asyncio.AbstractEventLoop, context: Dict[str, Any]) -> None:
+    if _is_stale_client_close(context):
+        return
+    loop.default_exception_handler(context)
+
+
+def run_sync(coro: Coroutine[Any, Any, Any]) -> Any:
+    """``asyncio.run(coro)``, minus the stale-client message described above."""
+    with asyncio.Runner() as runner:
+        runner.get_loop().set_exception_handler(_exception_handler)
+        return runner.run(coro)
diff --git a/simpleaudit/cross_judge.py b/simpleaudit/cross_judge.py
index 700f3a1..f050dc9 100644
--- a/simpleaudit/cross_judge.py
+++ b/simpleaudit/cross_judge.py
@@ -20,6 +20,7 @@
 from pathlib import Path
 from typing import Any, Dict, List, Optional, Union
 
+from simpleaudit._event_loop import run_sync
 from simpleaudit.experiment import AuditExperiment
 from simpleaudit.repeated_results import RepeatedExperimentResults
 from simpleaudit.utils import SEVERITY_ORDER, severity_direction
@@ -354,7 +355,7 @@ def run(
         try:
             asyncio.get_running_loop()
         except RuntimeError:
-            return asyncio.run(
+            return run_sync(
                 self.run_async(
                     scenarios=scenarios,
                     max_turns=max_turns,
diff --git a/simpleaudit/experiment.py b/simpleaudit/experiment.py
index 8addeb7..6ee87dd 100644
--- a/simpleaudit/experiment.py
+++ b/simpleaudit/experiment.py
@@ -8,6 +8,7 @@
 from collections import Counter
 
 from tqdm.auto import tqdm
+from simpleaudit._event_loop import run_sync
 from simpleaudit.results import AuditResult, AuditResults
 from simpleaudit.model_auditor import ModelAuditor
 from simpleaudit.repeated_results import RepeatedExperimentResults
@@ -689,7 +690,7 @@ def run(
         try:
             asyncio.get_running_loop()
         except RuntimeError:
-            return asyncio.run(
+            return run_sync(
                 self.run_async(
                     scenarios,
                     max_turns=max_turns,
diff --git a/simpleaudit/model_auditor.py b/simpleaudit/model_auditor.py
index 4218ec9..041eb81 100644
--- a/simpleaudit/model_auditor.py
+++ b/simpleaudit/model_auditor.py
@@ -25,6 +25,7 @@
 from any_llm import AnyLLM
 from tqdm.auto import tqdm
 
+from ._event_loop import run_sync
 from .context_marks import render_documents
 from .judges import get_judge
 from .judges.compose import SEVERITY_RESPONSE_SCHEMA
@@ -1222,7 +1223,7 @@ def run(
         try:
             asyncio.get_running_loop()
         except RuntimeError:
-            return asyncio.run(
+            return run_sync(
                 self.run_async(
                     scenarios,
                     max_turns=max_turns,
diff --git a/simpleaudit/reframing.py b/simpleaudit/reframing.py
index 62bf703..92f8799 100644
--- a/simpleaudit/reframing.py
+++ b/simpleaudit/reframing.py
@@ -75,6 +75,7 @@
 from pathlib import Path
 from typing import Any, Callable, Dict, List, Mapping, Optional, Sequence, Union
 
+from simpleaudit._event_loop import run_sync
 from simpleaudit.judges import get_judge
 from simpleaudit.model_auditor import ModelAuditor
 from simpleaudit.repeated_results import (
@@ -1005,7 +1006,7 @@ def _run_sync(coro_factory: Callable[[], Any], name: str) -> Any:
     try:
         asyncio.get_running_loop()
     except RuntimeError:
-        return asyncio.run(coro_factory())
+        return run_sync(coro_factory())
     raise RuntimeError(
         f"{name}() cannot be called from an active event loop. "
         f"Use await {name}_async() instead."
diff --git a/tests/test_event_loop.py b/tests/test_event_loop.py
new file mode 100644
index 0000000..71a1c9a
--- /dev/null
+++ b/tests/test_event_loop.py
@@ -0,0 +1,136 @@
+"""run_sync: one event loop per sync run, without the stale-client close message."""
+
+import asyncio
+import gc
+import json
+import logging
+import threading
+from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
+
+import pytest
+
+from simpleaudit._event_loop import _exception_handler, _is_stale_client_close, run_sync
+
+NEVER_RETRIEVED = "Task exception was never retrieved"
+
+
+class AsyncClient:
+    """Stands in for httpx's client: only the coroutine's qualified name is checked."""
+
+    async def aclose(self):
+        raise RuntimeError("Event loop is closed")
+
+
+class Other:
+    async def aclose(self):
+        raise RuntimeError("Event loop is closed")
+
+
+def _context(coro, exception):
+    loop = asyncio.new_event_loop()
+    try:
+        task = loop.create_task(coro)
+        loop.run_until_complete(asyncio.wait([task]))
+        return {"message": NEVER_RETRIEVED, "exception": exception, "future": task}
+    finally:
+        loop.close()
+
+
+class TestFilter:
+    def test_a_client_close_on_a_closed_loop_is_dropped(self):
+        ctx = _context(AsyncClient().aclose(), RuntimeError("Event loop is closed"))
+        assert _is_stale_client_close(ctx)
+
+    def test_another_coroutine_failing_the_same_way_is_kept(self):
+        ctx = _context(Other().aclose(), RuntimeError("Event loop is closed"))
+        assert not _is_stale_client_close(ctx)
+
+    def test_a_client_close_failing_differently_is_kept(self):
+        ctx = _context(AsyncClient().aclose(), RuntimeError("connection reset"))
+        assert not _is_stale_client_close(ctx)
+
+    def test_kept_contexts_reach_the_default_handler(self):
+        seen = []
+
+        class Loop:
+            def default_exception_handler(self, context):
+                seen.append(context)
+
+        kept = {"message": "something else", "exception": ValueError("x")}
+        _exception_handler(Loop(), kept)
+        _exception_handler(Loop(), _context(AsyncClient().aclose(), RuntimeError("Event loop is closed")))
+        assert seen == [kept]
+
+
+def test_run_sync_returns_the_result_and_raises_the_error():
+    async def ok():
+        return 42
+
+    async def bad():
+        raise ValueError("boom")
+
+    assert run_sync(ok()) == 42
+    with pytest.raises(ValueError, match="boom"):
+        run_sync(bad())
+
+
+class _Completions(BaseHTTPRequestHandler):
+    protocol_version = "HTTP/1.1"  # keep-alive, so the connection stays pooled
+
+    def do_POST(self):
+        self.rfile.read(int(self.headers.get("Content-Length", 0)))
+        body = json.dumps({
+            "id": "x", "object": "chat.completion", "created": 0, "model": "m",
+            "choices": [{"index": 0, "finish_reason": "stop",
+                         "message": {"role": "assistant", "content": "hi"}}],
+            "usage": {"prompt_tokens": 1, "completion_tokens": 1, "total_tokens": 2},
+        }).encode()
+        self.send_response(200)
+        self.send_header("Content-Type", "application/json")
+        self.send_header("Content-Length", str(len(body)))
+        self.end_headers()
+        self.wfile.write(body)
+
+    def log_message(self, *args):
+        pass
+
+
+@pytest.fixture
+def base_url():
+    server = ThreadingHTTPServer(("127.0.0.1", 0), _Completions)
+    thread = threading.Thread(target=server.serve_forever, daemon=True)
+    thread.start()
+    yield f"http://127.0.0.1:{server.server_address[1]}/v1"
+    server.shutdown()
+    server.server_close()
+
+
+def _two_runs(runner, base_url):
+    """A client used in one run and garbage-collected during the next."""
+    openai = pytest.importorskip("openai")
+    holder = {}
+
+    async def first():
+        client = openai.AsyncOpenAI(base_url=base_url, api_key="x", max_retries=0)
+        await client.chat.completions.create(model="m", messages=[{"role": "user", "content": "hi"}])
+        holder["client"] = client
+
+    async def second():
+        holder.clear()
+        gc.collect()  # the client sits in a reference cycle; its __del__ runs here
+        await asyncio.sleep(0.05)  # the aclose() task it scheduled runs and fails
+        gc.collect()
+
+    runner(first())
+    runner(second())
+
+
+def test_a_client_from_an_earlier_run_closes_quietly(base_url, caplog):
+    caplog.set_level(logging.ERROR, logger="asyncio")
+    _two_runs(asyncio.run, base_url)
+    if NEVER_RETRIEVED not in caplog.text:
+        pytest.skip("this openai version no longer schedules aclose() from __del__")
+    caplog.clear()
+
+    _two_runs(run_sync, base_url)
+    assert NEVER_RETRIEVED not in caplog.text