# Urlsession Code Review

> Reviews URLSession networking code for iOS/macOS. Covers async/await patterns, request building, error handling, caching, and background sessions. Use when this capability is needed.

- Skill: `tomevault-io/urlsession-code-review` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/urlsession-code-review`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/urlsession-code-review/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/urlsession-code-review

---


# URLSession Code Review

## Quick Reference

| Topic | Reference |
|-------|-----------|
| Async/Await | [async-networking.md](references/async-networking.md) |
| Requests | [request-building.md](references/request-building.md) |
| Errors | [error-handling.md](references/error-handling.md) |
| Caching | [caching.md](references/caching.md) |

## Review Checklist

### Response Validation
- [ ] HTTP status codes validated - URLSession does NOT throw on 404/500
- [ ] Response cast to HTTPURLResponse before checking status
- [ ] Both transport errors (URLError) and HTTP errors handled

### Memory & Resources
- [ ] Downloaded files moved/deleted (async API doesn't auto-delete)
- [ ] Sessions with delegates call `finishTasksAndInvalidate()`
- [ ] Long-running tasks use `[weak self]`
- [ ] Stored Task references cancelled when appropriate

### Configuration
- [ ] `timeoutIntervalForResource` set (default is 7 days!)
- [ ] URLCache sized adequately (default 512KB too small)
- [ ] Sessions reused for connection pooling

### Background Sessions
- [ ] Unique identifier (especially with app extensions)
- [ ] File-based uploads (not data-based)
- [ ] Delegate methods used (not completion handlers)

### Security
- [ ] No hardcoded secrets (use Keychain)
- [ ] Header values sanitized for CRLF injection
- [ ] Query params via URLComponents (not string concat)

## Output Format

```markdown
### Critical
1. [FILE:LINE] Missing HTTP status validation
   - Issue: 404/500 responses not treated as errors
   - Fix: Check `httpResponse.statusCode` is 200-299
```

---
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<!-- tomevault:4.0:skill_md:2026-04-11 -->