diff --git a/pyproject.toml b/pyproject.toml
index 8ac43ad..ef765dd 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -20,6 +20,9 @@ pythonpath = ["src"]
 [tool.ruff]
 line-length = 140
 target-version = "py311"
+# Benchmark fixtures are intentionally vulnerable, unformatted sample corpora;
+# linting/formatting them would flag the planted bugs and shift ground-truth lines.
+extend-exclude = ["benchmarks/fixtures"]
 
 [tool.ruff.lint]
 select = ["B", "E", "F", "I", "SIM", "UP"]