diff --git a/.prettierignore b/.prettierignore
index 18f5b1c2..72e8f751 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -22,3 +22,7 @@ ops/steward/
 # Generated by scripts/generate-third-party-licenses.mjs. Prettier reflows the tables and the
 # --check gate then compares its own output against a reformatted file and always fails.
 THIRD_PARTY_LICENSES.md
+
+# Owned by mono and kept byte-identical to mono ops/schedulers/pr-review/chip-pr-review.yml.
+# Reformatting it here would make it drift, so the format check leaves it alone.
+.github/workflows/chip-pr-review.yml