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
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
## 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-qafor pre-deploy verification- Hooks: add as a PostToolUse hook on
git pushto auto-check after deploys - CI: run in GitHub Actions after deploy step