diff --git a/pyproject.toml b/pyproject.toml
index 48cd2ab..cb4d057 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -127,7 +127,9 @@ pytest_add_cli_args_test_selection = [
     "tests/test_coverage_thresholds.py",
     "tests/test_numerical_contracts.py",
 ]
-mutate_only_covered_lines = true
+# Mutating the complete bounded target set is both stronger and avoids mutmut's
+# in-process native-extension unload/reload crash during covered-line discovery.
+mutate_only_covered_lines = false
 on_dependency_change = "rerun"
 
 [tool.uv]
diff --git a/tests/test_quality_policy.py b/tests/test_quality_policy.py
index 8e98fca..56d85e2 100644
--- a/tests/test_quality_policy.py
+++ b/tests/test_quality_policy.py
@@ -2,12 +2,20 @@
 
 from __future__ import annotations
 
+import tomllib
 from copy import deepcopy
 from datetime import date
+from pathlib import Path
 
 from scripts import check_quality_policy as quality
 
 
+def test_mutation_campaign_avoids_native_extension_reload_mode():
+    pyproject = tomllib.loads(Path("pyproject.toml").read_text())
+
+    assert pyproject["tool"]["mutmut"]["mutate_only_covered_lines"] is False
+
+
 def _policy():
     return {
         "minimums": dict(quality.BASELINE_FLOORS),