diff --git a/docs/problems/code-review.md b/docs/problems/code-review.md
index 113bb16bfe..befb687d08 100644
--- a/docs/problems/code-review.md
+++ b/docs/problems/code-review.md
@@ -64,6 +64,10 @@ Evaluates whether the code does what it claims to do.
 - If test files covering the changed code were recently modified, did those modifications weaken the test's ability to catch regressions?
 - Split-payload attacks: a production change paired with a test modification that masks the real behavior. (See [security-threat-model.md](security-threat-model.md#cross-cutting-attack-pattern-temporal-split-payload-test-poisoning) for why this matters.)
 - Coverage reduction: does the change remove or weaken existing test coverage?
+- Library-utility reimplementation: manual string parsing or format manipulation that reimplements a utility available in the project's declared dependencies.
+  - Look for patterns like `indexOf`, `split`, `substring`, or `startsWith` chains on structured strings where a dedicated parsing utility exists (e.g., `parseLocationRef`, `semver.parse`, `URL` constructor).
+  - Flag as medium-severity with a concrete suggestion when the manual reimplementation misses edge cases the utility handles.
+  - Skip if no utility exists or the manual implementation is intentional (e.g., performance-critical hot path).
 
 **Context needed:** The diff, relevant surrounding code, test files, git history of relevant test files, existing patterns in the repo.