diff --git a/steam_backlog_enforcer/tests/_isolate_incidents.py b/steam_backlog_enforcer/tests/_isolate_incidents.py
new file mode 100644
index 0000000..bd1644e
--- /dev/null
+++ b/steam_backlog_enforcer/tests/_isolate_incidents.py
@@ -0,0 +1,48 @@
+"""Autouse redirect for the bonus-incident log.
+
+``report_leetcode_incident`` appends to ``leetcode_bonus_incidents.log`` at the
+repo root, which is a real artifact the user reads to find out why an hour went
+missing. Left unpatched, any test that drives the fail-closed path writes into
+it -- and because the file is gitignored, nothing would ever fail to warn you.
+That happened: the first run of ``test_budget_resolve.py`` put two fabricated
+incidents into the live file.
+
+Redirected here rather than in each test for the same reason
+``_isolate_filesystem`` exists: enumerating the tests that need it is the
+version of this that goes wrong the next time someone adds one.
+
+Split into its own module to keep ``conftest.py`` inside the 250-line cap;
+``conftest`` imports the fixture by name, which is what registers it.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+from unittest.mock import patch
+
+import pytest
+
+if TYPE_CHECKING:
+    from collections.abc import Iterator
+    from pathlib import Path
+
+
+@pytest.fixture(autouse=True)
+def _isolate_incidents(tmp_path: Path) -> Iterator[None]:
+    """Point the incident log at a per-test file.
+
+    Args:
+        tmp_path: pytest's temporary directory.
+
+    Yields:
+        None, with the log redirected and the reported-incident memo cleared so
+        one test's rate limit cannot mute the next.
+    """
+    from steam_backlog_enforcer import _bonus_incident
+
+    _bonus_incident.reset_reported()
+    with patch.object(
+        _bonus_incident, "INCIDENT_LOG", tmp_path / "leetcode_bonus_incidents.log"
+    ):
+        yield
+    _bonus_incident.reset_reported()
diff --git a/steam_backlog_enforcer/tests/conftest.py b/steam_backlog_enforcer/tests/conftest.py
index a0ed707..3d3c222 100644
--- a/steam_backlog_enforcer/tests/conftest.py
+++ b/steam_backlog_enforcer/tests/conftest.py
@@ -21,13 +21,19 @@ from unittest.mock import MagicMock, patch
 import pytest
 
 # Imported for its autouse side effect: naming it here registers it.
+from steam_backlog_enforcer.tests._isolate_incidents import _isolate_incidents
 from steam_backlog_enforcer.tests._isolate_playtime import _isolate_playtime
 from steam_backlog_enforcer.tests._no_subprocess import _block_real_subprocesses
 from steam_backlog_enforcer.tests._no_workout_http import _no_workout_http
 
 # Re-exported so ruff --fix does not delete the imports above: pytest
 # registers autouse fixtures by name, so they look unused to the linter.
-__all__ = ["_block_real_subprocesses", "_isolate_playtime", "_no_workout_http"]
+__all__ = [
+    "_block_real_subprocesses",
+    "_isolate_incidents",
+    "_isolate_playtime",
+    "_no_workout_http",
+]
 
 from steam_backlog_enforcer.tests._total_block_paths import (
     BLOCK,