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Get Started Free →Use when auditing slow page loads, heavy assets, or rendering delays related to Minimize cumulative layout shift. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.
.claude/skills/thedaviddias-cumulative-layout-shift/SKILL.md| Test case | Without → With | Effect | Δ tokens | Δ turns |
|---|---|---|---|---|
| case-02 | ✓→✓ | ＝ Same ✓ | -12% | 0% |
| case-03 | ✓→✓ | ＝ Same ✓ | -8% | 0% |
| case-04 | ✓→✓ | ＝ Same ✓ | -13% | 0% |
| case-05 | ✓→✓ | ＝ Same ✓ | -7% | 0% |
| case-06 | ✓→✓ | ＝ Same ✓ | -13% | 0% |
Layout shifts cause accidental clicks, reading disruption, and user frustration—a good CLS score ensures content stays where users expect it.
Measure CLS using Lighthouse or PageSpeed Insights. Verify score is below 0.1 for good visual stability.
Reserve space for images/embeds with dimensions, use font-display strategies, and avoid injecting content above existing content.
Explain how CLS measures visual stability and why unexpected layout shifts frustrate users and cause accidental clicks.
Review the routes, assets, and loading behavior that affect Minimize cumulative layout shift. Flag exact files, requests, or rendering steps that add unnecessary network, CPU, or layout cost, and describe the measurement method used to confirm the issue.
For full implementation details, code examples, and framework-specific guidance, see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/performance/cumulative-layout-shift
| Case | Status | Duration (ms) | Turns | Tokens | Tool calls | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Without | With | Δ | Without | With | Δ | Without | With | Δ | Without | With | Δ | ||
case-01 | fail→fail | 16,265 | 13,979 | -14% | 1 | 1 | 0% | 3,000 | 2,902 | -3% | 0 | 0 | — |
case-02 | pass→pass | 7,698 | 5,647 | -27% | 1 | 1 | 0% | 1,512 | 1,328 | -12% | 0 | 0 | — |
case-03 | pass→pass | 9,043 | 6,964 | -23% | 1 | 1 | 0% | 1,781 | 1,635 | -8% | 0 | 0 | — |
case-04 | pass→pass | 11,186 | 9,782 | -13% | 1 | 1 | 0% | 2,408 | 2,100 | -13% | 0 | 0 | — |
case-05 | pass→pass | 10,689 | 6,861 | -36% | 1 | 1 | 0% | 1,764 | 1,636 | -7% | 0 | 0 | — |
case-06 | pass→pass | 11,834 | 9,253 | -22% | 1 | 1 | 0% | 2,381 | 2,078 | -13% | 0 | 0 | — |
case-07 | pass→pass | 11,964 | 7,455 | -38% | 1 | 1 | 0% | 2,325 | 1,622 | -30% | 0 | 0 | — |
case-08 | pass→pass | 5,525 | 6,496 | +18% | 1 | 1 | 0% | 1,019 | 1,454 | +43% | 0 | 0 | — |
case-09 | pass→pass | 7,160 | 4,691 | -34% | 1 | 1 | 0% | 1,363 | 1,273 | -7% | 0 | 0 | — |
case-10 | pass→pass | 9,733 | 6,360 | -35% | 1 | 1 | 0% | 1,919 | 1,666 | -13% | 0 | 0 | — |
case-11 | pass→pass | 5,894 | 5,709 | -3% | 1 | 1 | 0% | 991 | 1,204 | +21% | 0 | 0 | — |
case-12 | pass→pass | 12,576 | 7,749 | -38% | 1 | 1 | 0% | 2,109 | 1,462 | -31% | 0 | 0 | — |
case-13 | pass→pass | 18,662 | 14,481 | -22% | 1 | 1 | 0% | 3,043 | 3,084 | +1% | 0 | 0 | — |
case-14 | pass→pass | 12,298 | 6,333 | -49% | 1 | 1 | 0% | 2,072 | 1,399 | -32% | 0 | 0 | — |
case-15 | pass→pass | 1,976 | 2,299 | +16% | 1 | 1 | 0% | 383 | 693 | +81% | 0 | 0 | — |
case-16 | pass→pass | 11,158 | 11,633 | +4% | 1 | 1 | 0% | 2,355 | 2,565 | +9% | 0 | 0 | — |
case-17 | pass→pass | 7,983 | 8,193 | +3% | 1 | 1 | 0% | 1,872 | 1,850 | -1% | 0 | 0 | — |
case-18 | pass→pass | 3,888 | 3,662 | -6% | 1 | 1 | 0% | 704 | 827 | +17% | 0 | 0 | — |
case-19 | pass→pass | 11,811 | 10,376 | -12% | 1 | 1 | 0% | 2,252 | 1,834 | -19% | 0 | 0 | — |
case-20 | pass→pass | 9,528 | 6,868 | -28% | 1 | 1 | 0% | 1,971 | 1,844 | -6% | 0 | 0 | — |
case-21 | pass→pass | 17,207 | 13,917 | -19% | 1 | 1 | 0% | 3,432 | 3,219 | -6% | 0 | 0 | — |
case-22 | pass→pass | 14,379 | 14,213 | -1% | 1 | 1 | 0% | 2,665 | 3,148 | +18% | 0 | 0 | — |
DecimalAI ran this skill against gemini-3.6-flash twice over the same eval suite — once with the skill loaded and once without — and compared the two runs case by case. 22 cases were attempted. The headline lift of 0 percentage points is the difference between those two pass rates over the 22 comparable cases.
Other measured skills in the registry, with their headline benchmark lift.