diff --git a/src/audit.py b/src/audit.py
index 67daeed..10d48f0 100644
--- a/src/audit.py
+++ b/src/audit.py
@@ -121,13 +121,18 @@ def audit_log_path() -> Path:
     """
     global _LOG_PATH
     if _LOG_PATH is None:
+        # Resolve the session id BEFORE acquiring _LOCK. ``_session_id``
+        # also takes ``_LOCK`` to write its first value, and the lock
+        # is non-reentrant — nesting them deadlocks the first caller
+        # in a clean module state. (Hit in ``log_session_start`` since
+        # it's the first GUI call and both globals are unset.)
+        sid = _session_id()[:8]
         with _LOCK:
             if _LOG_PATH is None:
                 try:
                     ts = datetime.now(tz=timezone.utc).strftime("%Y%m%dT%H%M%SZ")
                 except Exception:
                     ts = "unknown"
-                sid = _session_id()[:8]
                 _LOG_PATH = audit_log_dir() / f"datatools-{ts}-{sid}.jsonl"
     return _LOG_PATH
 
diff --git a/tests/test_audit.py b/tests/test_audit.py
index 7e06559..2ee2f30 100644
--- a/tests/test_audit.py
+++ b/tests/test_audit.py
@@ -26,9 +26,14 @@ import pytest
 @pytest.fixture
 def isolated_audit(monkeypatch, tmp_path):
     """Redirect audit writes into ``tmp_path`` and reset module state
-    so each test starts fresh."""
+    so each test starts fresh.
+
+    The kill switch is bypassed for the duration of the test by
+    patching the module-level constant directly — these tests need
+    the real producer path to run."""
     monkeypatch.setenv("DATATOOLS_AUDIT_DIR", str(tmp_path))
     from src import audit
+    monkeypatch.setattr(audit, "_DISABLED", False)
     audit.reset_for_tests()
     yield audit
     # Best-effort cleanup so a runaway writer thread doesn't keep
@@ -115,6 +120,7 @@ class TestUnwritableTargetDoesntCrash:
         not_a_dir.write_text("hi")
         monkeypatch.setenv("DATATOOLS_AUDIT_DIR", str(not_a_dir))
         from src import audit
+        monkeypatch.setattr(audit, "_DISABLED", False)
         audit.reset_for_tests()
         try:
             start = time.perf_counter()