Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
git clone --depth 1 https://github.com/kensaurus/cursor-kenjiWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/rules/kensaurus/cursor-kenji/web-performance)<a href="https://agentmods.dev/rules/kensaurus/cursor-kenji/web-performance"><img src="https://agentmods.dev/badge/rules/kensaurus/cursor-kenji/web-performance/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/rules/kensaurus/cursor-kenji/web-performance"><img src="https://agentmods.dev/badge/rules/kensaurus/cursor-kenji/web-performance.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00000 | $0.00491 |
| Opus 5.5 | $0.00000 | $0.00196 |
| Sonnet 5.5 | $0.00000 | $0.00098 |
| Haiku 4.5 | $0.00000 | $0.00049 |
Grade A, and why
web-performance scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 22d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
Web performance guardrails
Budgets (fail the PR, not the build)
- Field p75: LCP ≤ 2.5 s · INP ≤ 200 ms · CLS ≤ 0.1 · TTFB ≤ 800 ms
- Initial JS per route ≤ 170 KB gz (marketing) / ≤ 300 KB gz (app)
- ≤ 3 third-party scripts on any route; none synchronous in
<head>
LCP rules
- The LCP image is never
loading="lazy"; it getspriority(next/image) orfetchpriority="high"+ preload - LCP content is server-rendered and in the HTML — not a CSS background, not client-fetched
- Every
<img>/<video>/<iframe>has dimensions oraspect-ratio
Rendering
- Server Components by default;
'use client'only at interactive leaves - Slow data goes behind
<Suspense>with a sized skeleton; never block the shell - React Compiler is on (
reactCompiler: true); do not hand-writememo/useMemo/useCallbackwithout Profiler evidence
Responsiveness (INP)
- No task > 50 ms in an input handler; yield with
scheduler.yield()/startTransition - No synchronous layout reads in handlers
- Third-party scripts:
<Script strategy="lazyOnload">or consent-gated; embeds use facades
Navigation
- No
unloadlisteners (bfcache); usepagehide - Speculation Rules
prefetch(moderate) for in-site links; prerender only high-probability pages; never speculate side-effect URLs - Fonts via
next/font(fallback metrics + subsetting);font-display: swap
Measure before and after
web-vitals/attributionin prod; Lighthouse CI budget in CI; field p75 is the source of truth- First-load diagnosis →
audit-performance; implement instant nav →enhance-web-instant-nav
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 22d ago Changed · -495 tokens per session b96cbd27ccd8
- 1mo ago First seen · 43 lines · 495 tokens per session scan A de339de4a3a2
web-performance is a cursor rule published in the GitHub repository kensaurus/cursor-kenji (9 stars, last pushed 17d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 491 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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