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SKILL verified MIT Self-run

Qa Perf

skill-christopherlouet-claude-base-qa-perf · by christopherlouet

Application performance optimization. Trigger when the user wants to improve speed, reduce latency, or optimize resources.

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Install

$ agentstack add skill-christopherlouet-claude-base-qa-perf

✓ scanned · ✓ verified, works with Claude Code, Cursor, and more.

Security review

✓ Passed

No issues found. Passed automated security review. · v0.1.0 How review works →

  • ✓ Prompt-injection patterns
  • ✓ Secret / credential exfiltration
  • ✓ Dangerous shell & filesystem operations
  • ✓ Untrusted network calls
  • ✓ Known-malicious package signatures

What it can access

  • ✓ Network access No
  • ✓ Filesystem access No
  • ✓ Shell / process execution No
  • ✓ Environment & secrets No
  • ✓ Dynamic code execution No

From automated source analysis of v0.1.0. “Used” means the capability is present in the source — more access means more to trust, not that it’s unsafe.

View the full security report →

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Reliability & compatibility

✓ Security review passed
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Declared compatibility

Claude CodeClaude Desktop

Compatibility is declared by the source manifest. End-to-end runtime verification is coming, see below.

Preview Execution monitoring

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About

Performance Optimization (pointer)

Canonical thresholds, current Web Vitals (LCP/INP/CLS — note INP replaced FID in 2024), and Chrome perf-team remediation patterns are at:

  • addyosmani/web-quality-skills — github.com/addyosmani/web-quality-skills (MIT, 1.8k★, maintained by Addy Osmani — Chrome DevTools / Lighthouse engineering lead). Covers Core Web Vitals, perf, a11y, SEO.
  • web.dev/vitals — web.dev/vitals (Google's canonical Web Vitals reference)
  • Vercel React best practices — see vercel-react-best-practices skill (foundation-installed) for React-specific patterns

Foundation workflow (when to invoke this skill)

qa-perf is dispatched by qa-loop during the AUDIT phase, in parallel with qa-security / wcag-audit / qa-claudemd. It's a measurement workflow, not an optimisation cookbook:

  1. Measure first: run Lighthouse / WebPageTest / DevTools Performance against a known scope (the URL, page, or endpoint from argument-hint).
  2. Compare to canonical thresholds (see table below).
  3. Identify the bottleneck axis: render-blocking JS? N+1 DB query? Image weight? Bundle size? Each axis has a dedicated vendor remediation guide.
  4. Recommend with quantified impact (e.g. "lazy-loading hero image saves ~400ms LCP per Lighthouse run #3").
  5. Re-measure after the fix — a perf change without before/after numbers is theatre.

Canonical Web Vitals thresholds (2024-2026)

| Metric | Good | Needs improvement | Poor | Tool | |---|---|---|---|---| | LCP (Largest Contentful Paint) | 4s | Lighthouse, web-vitals | | INP (Interaction to Next Paint, replaces FID) | 500ms | web-vitals | | CLS (Cumulative Layout Shift) | 0.25 | Lighthouse, web-vitals | | TTFB | 600ms | DevTools Network |

Foundation discipline (keep across releases)

  • No optimisation without measurement: profile before changing code. Guessed bottlenecks are wrong ~70% of the time.
  • Before/after numbers mandatory: every perf PR must include the Lighthouse delta or equivalent. Without numbers, the work is unprovable.
  • Cache invalidation > caching: adding a cache is easy; correctly invalidating it is the bug surface. Surface cache TTLs in code review.
  • N+1 is the #1 backend perf bug: when an endpoint feels slow, instrument query count before optimising anything else.

See also

  • qa-chrome skill — DevTools manual review (paired layer)
  • dev-react-perf skill — React-specific re-render audit + memoization patterns
  • ops-monitoring — production perf instrumentation (OTEL, RUM)
  • vercel-react-best-practices skill (foundation-installed)
  • Audit pilot trace: specs/marketplace-audit/qa-skills-pilot-2026-05-06.md

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

Install and usage instructions live in the source repository linked above.

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Versions

  • v0.1.0 Imported from the upstream source.

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