diff --git a/tests/conftest.py b/tests/conftest.py
index 5c647e59d7..a90b7d4475 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -663,8 +663,18 @@ def _close_leaked_session_dbs():
     on those ``close()`` releases a refcount rather than closing, so a sweep
     would silently retire a shared generation that a wider-scoped fixture
     still holds. The registry owns that lifecycle (``close_all()``).
+
+    Before the sweep, the auto-title upgrade threads a turn spawned are joined
+    (bounded): they hold the turn's SessionDB and write to it (and print to
+    ``sys.stdout``) after the turn returns, so left running they race this
+    close (``_reopen_after_close_locked`` on a daemon thread), the next test's
+    capture, and interpreter finalization — the ``Fatal Python error`` /
+    SIGSEGV shape of #113186, seen from ``tests/gateway/test_timestamp_sidecar_replay.py``.
     """
     yield
+    title_generator = sys.modules.get("agent.title_generator")  # never imported = nothing spawned
+    if title_generator is not None:
+        title_generator.wait_for_title_upgrades()
     try:
         from hermes_state_guard import _test_instance_registry as registry
     except Exception:
diff --git a/tests/gateway/test_timestamp_sidecar_replay.py b/tests/gateway/test_timestamp_sidecar_replay.py
index cd4e134642..0e73cc4a00 100644
--- a/tests/gateway/test_timestamp_sidecar_replay.py
+++ b/tests/gateway/test_timestamp_sidecar_replay.py
@@ -57,6 +57,9 @@ def responses_agent(tmp_path, monkeypatch):
         "hermes_cli.plugins.invoke_hook",
         lambda hook, **kw: [{"context": POLICY}] if hook == "pre_llm_call" else [],
     )
+    # Titling is not under test; its daemon thread would outlive the turn holding ``db`` and race
+    # the close below (a cross-thread sqlite reopen at interpreter shutdown crashed CI: #113186).
+    monkeypatch.setattr("agent.title_generator.maybe_auto_title", lambda *args, **kwargs: None)
 
     def respond(kwargs, **unused):
         captured.append(deepcopy(kwargs))
diff --git a/tests/hermes_state/test_session_db_leak_sweep.py b/tests/hermes_state/test_session_db_leak_sweep.py
index c6b2024183..335a78a809 100644
--- a/tests/hermes_state/test_session_db_leak_sweep.py
+++ b/tests/hermes_state/test_session_db_leak_sweep.py
@@ -20,6 +20,9 @@ test is actually closed by the suite-level sweep.
 
 from __future__ import annotations
 
+import threading
+import time
+
 import hermes_state_guard
 from hermes_state import SessionDB
 
@@ -58,3 +61,24 @@ def test_previously_leaked_instance_was_closed_by_the_sweep():
     # must have closed the leaked instance (writer conn released), which is
     # what bounds fd/RSS growth in single-process runs.
     assert db._conn is None
+
+
+# Same handoff shape for the auto-title upgrade thread a turn leaves behind: it holds the
+# turn's SessionDB, so the sweep must join it before closing stores (else the daemon thread
+# reopens the closed store and races interpreter finalization — the SIGSEGV shape of #113186).
+_upgrade_thread: list[threading.Thread] = []
+
+
+def test_slow_title_upgrade_thread_is_left_running_within_the_test():
+    from agent.title_generator import _UPGRADE_THREADS
+
+    thread = threading.Thread(target=time.sleep, args=(1.5,), name="auto-title", daemon=True)
+    _UPGRADE_THREADS.add(thread)
+    thread.start()
+    assert thread.is_alive()
+    _upgrade_thread.append(thread)
+
+
+def test_title_upgrade_thread_was_joined_before_the_sweep_closed_stores():
+    assert _upgrade_thread, "expected the previous test to have started an upgrade thread"
+    assert not _upgrade_thread.pop().is_alive()