diff --git a/tests/conftest.py b/tests/conftest.py
index 3c02d8d18..d3be0ce86 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,4 +1,5 @@
 import asyncio
+import gc
 import multiprocessing.context
 import os
 import sys
@@ -58,6 +59,12 @@ def pytest_runtest_setup(item):  # type: ignore[reportMissingParameterType]
         print()
 
 
+def pytest_collection_finish() -> None:
+    # Freeze the import-time heap once so full GC passes only cover test allocations
+    gc.collect()
+    gc.freeze()
+
+
 def pytest_addoption(parser):  # type: ignore[reportMissingParameterType]
     parser.addoption(
         "-E",
diff --git a/tests/contrib/langgraph/test_replay.py b/tests/contrib/langgraph/test_replay.py
index f5d1a8e92..3c8880093 100644
--- a/tests/contrib/langgraph/test_replay.py
+++ b/tests/contrib/langgraph/test_replay.py
@@ -1,4 +1,5 @@
 import sys
+import warnings
 from datetime import timedelta
 from uuid import uuid4
 
@@ -52,10 +53,21 @@ async def test_replay(client: Client):
         )
         await handle.result()
 
-    await Replayer(
-        workflows=[TwoNodesWorkflow],
-        plugins=[plugin],
-    ).replay_workflow(await handle.fetch_history())
+    with warnings.catch_warnings(record=True) as recorder:
+        warnings.filterwarnings(
+            "always", message=r"Module .* was imported after initial workflow load"
+        )
+        await Replayer(
+            workflows=[TwoNodesWorkflow],
+            plugins=[plugin],
+        ).replay_workflow(await handle.fetch_history())
+
+    # Sandbox imports during an activation count toward the deadlock timeout
+    assert not [
+        str(w.message)
+        for w in recorder
+        if "was imported after initial workflow load" in str(w.message)
+    ]
 
 
 @pytest.mark.skipif(