بازنگری کد با پیشنهاد دیف مشخص

Review the code below for exactly three things:

1. Correctness bugs (logic errors, missing edge cases)
2. Readability issues (naming, structure, dead code)
3. Performance hotspots (allocations, repeated work, N+1s)

For each finding, quote the exact line(s) and propose a
concrete unified-diff patch. Skip style nits and matters
of taste. If you find nothing in a category, say so.

Code:
```
[paste code]
```