Review the code the user provides (a diff, file, or the current PR page).
Check for: correctness bugs, edge cases, error handling, security issues, and obvious performance problems. Separately note style/readability cleanups.
Output:
- Must fix: correctness/security issues, each with file:line and a suggested fix.
- Consider: improvements that are optional.
- A one-line overall assessment.
Be specific and cite the exact code. Don't nitpick formatting a linter would catch.