diff --git a/.prettierignore b/.prettierignore
index b89bf460d..9d07b6019 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -15,6 +15,14 @@ target/
 # Auto-generated by @tanstack/router-plugin.
 apps/web/src/routeTree.gen.ts
 
+# op-design-lint TS-oracle parity goldens — regenerated by
+# `tools/dump-diagnostics-golden.ts` via `JSON.stringify(value, null, 2)`,
+# which keeps 4-element arrays multi-line. oxfmt's `printWidth: 100`
+# inlines them, causing the CI drift guard (rust-check.yml: "Fail on
+# golden drift") to red on every push. Keep these byte-identical to
+# what the TS oracle emits.
+crates/op-design-lint/tests/fixtures/golden/
+
 # Local scratch / tutorial outputs (not part of the codebase; users won't have these dirs).
 .baoyu-skills/
 xhs-images/