Windows Core Web Vitals lab report

repair-core-web-vitals/lab-report.md
# Windows Core Web Vitals lane: lab evidence repair

Target: `https://flatfeehousecleanerssarasota.com/`

Method: local Chrome plus Lighthouse 13.4.1 mobile navigation. Read-only public run. Client site unchanged.

## Verdict

`PASS`

The Lighthouse JSON exists, parses, names the homepage as the final URL, and contains extractable laboratory metrics. Output was not absent and was not invalid.

## Lab metrics versus field CWV

These numbers are laboratory Lighthouse synthetic metrics. They are not field Core Web Vitals. Field CWV are CrUX or Search Console 75th-percentile LCP, INP, and CLS from real users. This run did not collect field CWV.

| Class | What this run produced | What this run did not produce |
|:---|:---|:---|
| Laboratory metrics | Lighthouse mobile FCP, LCP, Speed Index, TBT, CLS, TTI, TTFB | A ranking claim |
| Field Core Web Vitals | Nothing | CrUX, Search Console, INP, 75th-percentile real-user LCP/INP/CLS |

## Exact laboratory results

| Metric | Numeric value | Display | Lab rating against skill thresholds |
|:---|---:|:---|:---|
| Performance score | 0.70 | 70 / 100 | Lab score only, not a CWV pass/fail |
| First Contentful Paint | 1522.4674999999997 ms | 1.5 s | Laboratory only |
| Largest Contentful Paint | 6260.800314712525 ms | 6.3 s | Poor versus the skill good threshold of 2.5 s or less |
| Speed Index | 1536.2335055427334 ms | 1.5 s | Laboratory only |
| Total Blocking Time | 74 ms | 70 ms | Laboratory proxy, not INP |
| Cumulative Layout Shift | 0.1628278133669162 | 0.163 | Needs work versus the skill good threshold of 0.1 or less |
| Time to Interactive | 6342.159296183778 ms | 6.3 s | Laboratory only |
| Server response / TTFB | 198 ms | Root document took 200 ms | Within the skill reference of under 800 ms |
| Interaction to Next Paint | null | not present | Requires field data or a controlled interaction trace |
| Max potential FID | 93 ms | 90 ms | Deprecated lab diagnostic, not a Core Web Vital |

## Command

```text
npx --no-install lighthouse "https://flatfeehousecleanerssarasota.com/" --only-categories=performance --form-factor=mobile --screenEmulation.mobile --chrome-path="C:\Program Files\Google\Chrome\Application\chrome.exe" --chrome-flags="--headless=new --disable-gpu --no-first-run --no-default-browser-check --disable-extensions --user-data-dir=F:\Projects\mdai\audits\skill-finalization\current-execution\flat-fee-execution\repair-core-web-vitals\chrome-profile-20260812-142346" --output=json --output-path="F:\Projects\mdai\audits\skill-finalization\current-execution\flat-fee-execution\repair-core-web-vitals\lighthouse-mobile.json" --quiet
```

Chrome path: `C:\Program Files\Google\Chrome\Application\chrome.exe`

Lighthouse exit code: `0`

Fetch time: `2026-08-12T18:24:03.408Z`

## SHA-256

`380a3e85a2aebf8a4b18a2a2be78e07e09f7c04effc26d7ffd79e4af01c80b8b` for `lighthouse-mobile.json` (862481 bytes)

## Chrome profile cleanup

A dedicated campaign profile was used. After the JSON was written, that profile directory was removed successfully. No EPERM remained. A Windows profile-cleanup error would not have invalidated a written valid JSON.

## Runtime note

Stderr printed `LanternError: missing metric scores for specified navigation` during insights computation. `runtimeError` in the JSON is null. Core laboratory metrics are present and numeric. That stderr line is not treated as a missing or invalid artifact.

## Boundaries

No WordPress, Search Console, GBP, credentials, or paid APIs were used. The client site was not changed.