impl-standards

# Implementation Standards

Apply these standards during implementation to ensure consistent, maintainable code.

## When to Use This Skill

- During `/itp:go` Phase 1
- When writing new production code
- User mentions "error handling", "constants", "magic numbers", "progress logging"
- Before release to verify code quality

## Quick Reference

| Standard         | Rule                                                                     |
| ---------------- | ------------------------------------------------------------------------ |
| **Errors**       | Raise + propagate; no fallback/default/retry/silent                      |
| **Constants**    | Abstract magic numbers into semantic, version-agnostic dynamic constants |
| **Dependencies** | Prefer OSS libs over custom code; no backward-compatibility needed       |
| **Progress**     | Operations >1min: log status every 15-60s                                |
| **Logs**         | `logs/{adr-id}-YYYYMMDD_HHMMSS.log` (nohup)                              |
| **Metadata**     | Optional: `catalog-info.yaml` for service discovery                      |

---

## Error Handling

**Core Rule**: Raise + propagate; no fallback/default/retry/silent

```python
# ✅ Correct - raise with context
def fetch_data(url: str) -> dict:
    response = requests.get(url)
    if response.status_code != 200:
        raise APIError(f"Failed to fetch {url}: {response.status_code}")
    return response.json()

# ❌ Wrong - silent catch
try:
    result = fetch_data()
except Exception:
    pass  # Error hidden
```

See [Error Handling Reference](./references/error-handling.md) for detailed patterns.

---

## Constants Management

**Core Rule**: Abstract magic numbers into semantic constants

```python
# ✅ Correct - named constant
DEFAULT_API_TIMEOUT_SECONDS = 30
response = requests.get(url, timeout=DEFAULT_API_TIMEOUT_SECONDS)

# ❌ Wrong - magic number
response = requests.get(url, timeout=30)
```

See [Constants Management Reference](./references/c