long-range-sensors

name	long-range-sensors
description	Post-deploy canary: baseline capture, regression detection, relative comparison. Use when verifying a deploy, checking for regressions, or user says 'long range sensors', 'canary', or 'check deploy'.

/long-range-sensors -- Post-Deploy Canary

Capture baseline metrics from a deployed application, then detect regressions on subsequent runs. Relative comparison (before vs after), not absolute thresholds.

Arguments

• /long-range-sensors baseline <url> -- capture baseline metrics
• /long-range-sensors scan <url> -- scan and compare against baseline
• /long-range-sensors compare <url> -- alias for scan
• /long-range-sensors history <url> -- show scan history for a domain

Prerequisites

• Target URL must be reachable
• curl available for HTTP checks
• Playwright MCP for browser-based metrics (optional; degrades gracefully)

Metrics Captured

Metric	Method	Unit
Response time	curl -w '%{time_total}'	seconds
HTTP status	curl -o /dev/null -s -w '%{http_code}'	status code
Response size	curl -s -o /dev/null -w '%{size_download}'	bytes
Page load time	Playwright performance.timing	ms
Console errors	Playwright console listener	count
Broken links	Crawl internal links, check status	count
DOM element count	document.querySelectorAll('*').length	count
Image count	document.images.length	count

When Playwright is unavailable, browser-based metrics are skipped and the scan runs HTTP-only.

Workflow

flowchart TD
    Start([long-range-sensors]) --> Mode{Mode?}
    Mode -- baseline --> Capture["Capture all metrics\nfor target URL"]
    Capture --> Save["Save to .canary/{domain}/baseline.json"]
    Save --> Report["Report: baseline captured"]
    Mode -- scan --> HasBaseline{Baseline exists?}
    HasBaseline -- No --> AutoBase["Auto-capture baseline first"]
    AutoBase --> Scan
    HasBaseline -- Yes --> Scan["Capture current metrics"]
    Scan --> Compare["Compare current vs baseline"]
    Compare --> Deltas["Calculate deltas:\n% change per metric"]
    Deltas --> Classify{Any regression?}
    Classify -- No --> Green["GREEN: No regressions detected"]
    Classify -- Yes --> Severity["Classify severity:\nMinor (<10%) / Major (10-50%) / Critical (>50%)"]
    Severity --> SaveScan["Save scan to .canary/{domain}/scans/{timestamp}.json"]
    SaveScan --> Report2["Report with delta table"]
    Green --> SaveScan
    Mode -- history --> List["List all scans for domain\nwith trend summary"]
    List --> Done([Done])
    Report --> Done
    Report2 --> Done

Regression Detection

Deltas are calculated as percentage change from baseline:

delta = ((current - baseline) / baseline) * 100

Regression classification:

Delta	Response Time	Response Size	Console Errors	Broken Links
Minor	+10-25%	+/- 10-25%	+1-2	+1
Major	+25-50%	+/- 25-50%	+3-5	+2-3
Critical	+50%+	+/- 50%+	+5+	+4+

Direction matters: Response time increase = bad. Response size decrease (>25%) = suspicious (missing content?). Console errors increase = always bad.

Report Format

## Canary Report -- {url}

**Date**: {YYYY-MM-DD HH:mm}
**Baseline**: {baseline date}
**Overall**: {GREEN|AMBER|RED}

### Metric Comparison

| Metric | Baseline | Current | Delta | Status |
|--------|----------|---------|-------|--------|
| Response time | 0.42s | 0.51s | +21% | MINOR |
| HTTP status | 200 | 200 | -- | OK |
| Response size | 45.2KB | 44.8KB | -1% | OK |
| Page load | 1.2s | 1.4s | +17% | MINOR |
| Console errors | 0 | 3 | +3 | MAJOR |
| Broken links | 0 | 0 | -- | OK |

### Regressions Detected

- **MAJOR**: Console errors increased from 0 to 3
  - `TypeError: Cannot read property 'map' of undefined` (3x on /dashboard)
- **MINOR**: Response time increased 21% (0.42s -> 0.51s)

### Recommendation

{Actionable guidance based on findings}

Persistence

.canary/
  {domain}/
    baseline.json       # Latest baseline
    scans/
      {timestamp}.json  # Each scan result

JSON format for both baseline and scans:

{
  "url": "https://example.com",
  "timestamp": "2026-03-23T14:00:00Z",
  "metrics": {
    "response_time": 0.42,
    "http_status": 200,
    "response_size": 46284,
    "page_load_ms": 1200,
    "console_errors": 0,
    "broken_links": 0,
    "dom_elements": 847,
    "image_count": 12
  }
}

Multi-Page Scan

When scanning a URL:

1. Scan the provided URL (homepage/entry point)
2. Discover up to 10 internal links from that page
3. Scan each discovered page
4. Report per-page metrics + aggregate

Baseline captures the same page set. Subsequent scans match against the same pages.

Worked Example

User: /long-range-sensors baseline https://staging.myapp.com

1. Captures metrics for homepage + 8 discovered internal pages
2. Saves to .canary/staging.myapp.com/baseline.json
3. Reports: "Baseline captured: 9 pages, avg response 0.38s, 0 console errors, 0 broken links."

Later, after deploying a change:

User: /long-range-sensors scan https://staging.myapp.com

1. Re-captures same 9 pages
2. Compares against baseline
3. Finds: +3 console errors on /dashboard, +15% response time on /api/data
4. Reports: AMBER (1 MAJOR, 1 MINOR regression)

Troubleshooting

Symptom	Cause	Fix
"No baseline found"	First scan for this domain	Run baseline mode first, or scan will auto-capture
All metrics show 0% delta	Baseline and scan are identical	Expected if nothing changed
Browser metrics all skipped	Playwright not available	Install Playwright MCP for full metrics; HTTP-only still useful
Response time varies wildly	Network/server variability	Run baseline and scan under similar conditions; consider averaging 3 runs
"Domain mismatch"	URL differs from baseline URL	Use same URL for baseline and scan (including protocol and path)