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Canary Watch

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.

affaan-m on GitHub

Curated by PromptsEdge from a public repo · MIT license. All credit goes to the author.

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

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