Canary Watch

---
name: canary-watch
description: Use this skill to monitor and verify a deployed URL after releases — checks HTTP endpoints, SSE streams, static assets, console errors, and performance regressions after deploys, merges, or dependency upgrades. Smoke / canary / post-deploy verification.
metadata:
  origin: ECC
---

# Canary Watch — Post-Deploy Monitoring

## When to Use

- After deploying to production or staging
- After merging a risky PR
- When you want to verify a fix actually fixed it
- Continuous monitoring during a launch window
- After dependency upgrades

## How It Works

Monitors a deployed URL for regressions. Runs in a loop until stopped or until the watch window expires.

### What It Watches

```
1. HTTP Status — is the page returning 200?
2. Console Errors — new errors that weren't there before?
3. Network Failures — failed API calls, 5xx responses?
4. Performance — LCP/CLS/INP regression vs baseline?
5. Content — did key elements disappear? (h1, nav, footer, CTA)
6. API Health — are critical endpoints responding within SLA?
7. Static Assets — are JS, CSS, image, and font requests returning 2xx/3xx with expected content types?
8. SSE Streams — do event-stream endpoints connect and receive an initial event or heartbeat?
```

### Watch Modes

**Quick check** (default): single pass, report results
```
/canary-watch https://myapp.com
```

**Sustained watch**: check every N minutes for M hours
```
/canary-watch https://myapp.com --interval 5m --duration 2h
```

**Diff mode**: compare staging vs production
```
/canary-watch --compare https://staging.myapp.com https://myapp.com
```

### Alert Thresholds

```yaml
critical:  # immediate alert
  - HTTP status != 200
  - Console error count > 5 (new errors only)
  - LCP > 4s
  - API endpoint returns 5xx
  - Static asset returns 4xx/5xx
  - SSE endpoint cannot connect or drops before first heartbeat

warning:   # flag in report
  - LCP increased > 500ms from baseline
  - CLS > 0.1
  - New console warnings
  - Response time > 2x baseline
  - Static asset content type changed unexpectedly
  - SSE heartbeat latency > 2x baseline

info:      # log only
  - Minor performance variance
  - New network requests (third-party scripts added?)
```

### Notifications

When a critical threshold is crossed:
- Desktop notification (macOS/Linux)
- Optional: Slack/Discord webhook
- Log to `~/.claude/canary-watch.log`

## Output

```markdown
## Canary Report — myapp.com — 2026-03-23 03:15 PST

### Status: HEALTHY ✓

| Check | Result | Baseline | Delta |
|-------|--------|----------|-------|
| HTTP | 200 ✓ | 200 | — |
| Console errors | 0 ✓ | 0 | — |
| LCP | 1.8s ✓ | 1.6s | +200ms |
| CLS | 0.01 ✓ | 0.01 | — |
| API /health | 145ms ✓ | 120ms | +25ms |
| Static assets | 42/42 ✓ | 42/42 | — |
| SSE /events | connected ✓ | connected | +80ms heartbeat |

### No regressions detected. Deploy is clean.
```

## Integration

Pair with:
- `/browser-qa` for pre-deploy verification
- Hooks: add as a PostToolUse hook on `git push` to auto-check after deploys
- CI: run in GitHub Actions after deploy step