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.
npx skills add JunMystery/Agent-Guidance-Python --skill react-performancegit clone --depth 1 https://github.com/JunMystery/Agent-Guidance-PythonWrote 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/skills/junmystery/agent-guidance-python/react-performance)<a href="https://agentmods.dev/skills/junmystery/agent-guidance-python/react-performance"><img src="https://agentmods.dev/badge/skills/junmystery/agent-guidance-python/react-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/skills/junmystery/agent-guidance-python/react-performance"><img src="https://agentmods.dev/badge/skills/junmystery/agent-guidance-python/react-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 | $0.00086 | $0.04471 |
| Opus 5.5 | $0.00034 | $0.01788 |
| Sonnet 5.5 | $0.00017 | $0.00894 |
| Haiku 4.5 | $0.00009 | $0.00447 |
Grade A, and why
react-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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 576 lines — stays where its author put it; the contents beside it link to each section on GitHub.
React Performance
Performance optimization patterns for React 18/19 and Next.js, adapted from Vercel Labs react-best-practices (MIT, v1.0.0). This skill organizes rules by priority and provides decision-tree guidance for active code review and refactoring.
When to Activate
- Writing or reviewing React/Next.js code for performance
- Diagnosing slow page loads, slow interactions, or high CPU on the client
- Auditing bundle size or Lighthouse Core Web Vitals regressions
- Removing waterfalls in Server Components / API routes
- Reducing client-side re-renders
- Optimizing long lists, animations, or hydration
- Auditing optimization choices in PRs touching
app/,pages/,components/, or data layers
Priority Index
| Priority | Category | Prefix | When it matters |
|---|---|---|---|
| 1 — CRITICAL | Eliminating Waterfalls | async- |
Anytime await is followed by independent await |
| 2 — CRITICAL | Bundle Size Optimization | bundle- |
First-load JS, route-level imports, third-party libs |
| 3 — HIGH | Server-Side Performance | server- |
RSC, Server Actions, API routes, SSR |
| 4 — MEDIUM-HIGH | Client-Side Data Fetching | client- |
SWR / TanStack Query / raw fetch in hooks |
| 5 — MEDIUM | Re-render Optimization | rerender- |
High-frequency state updates, parent-child fan-out |
| 6 — MEDIUM | Rendering Performance | rendering- |
Long lists, animations, hydration |
| 7 — LOW-MEDIUM | JavaScript Performance | js- |
Hot loops, frequent allocations |
| 8 — LOW | Advanced Patterns | advanced- |
Effect-event integration, stable refs |
1. Eliminating Waterfalls (CRITICAL)
"Waterfalls are the #1 performance killer" — every sequential
awaitadds full network latency.
Cheap conditions before await
Check sync conditions (props, env, hardcoded flags) before awaiting remote data.
// INCORRECT
async function Page({ id }: { id: string }) {
const flag = await getFlag("show-page");
if (!flag || !id) return null;
const data = await getData(id);
// ...
}
// CORRECT — short-circuit on cheap sync condition first
async function Page({ id }: { id: string }) {
if (!id) return null;
const flag = await getFlag("show-page");
if (!flag) return null;
const data = await getData(id);
}
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.
- 1mo ago First seen · 576 lines · 86 tokens per session scan A ac76e8694d4f
react-performance is a skill published in the GitHub repository JunMystery/Agent-Guidance-Python (2 stars, last pushed 3mo ago), licensed MIT. It adds 86 tokens to every session and 4,471 once invoked, about $0.0003 per session on Opus 5.5. 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.
Other skills, from other repositories
dev-fix
Unified developer workflow for fixing bugs. Analyzes issue-tracker context, cross-checks docs/code, proposes a solution, implements the fix, verifies locally, and delivers a PR/MR.
verify-bug
Post-merge UAT verification workflow. Walks JIRA reproduce steps, performs comparative audits (Before/After), attaches evidence to JIRA, and transitions status on PASS.
incident-hotfix
Mitigate a production incident or urgent regression first, then route to root-cause remediation and a postmortem.
cyber-triage
Evidence-led blue incident triage with authorization and runtime gates.
sanity-form-component-suspense
Fix a Sanity Studio custom form component (components.input, components.field, components.item, or a plugin's form.components) that suspends without its own Suspense boundary, so it loads without layout shift and never blocks new documents. Use when the console warns "The custom input/field/item component ...…
common-performance-engineering
Enforce universal standards for high-performance development. Use when profiling bottlenecks, reducing latency, fixing memory leaks, improving throughput, or optimizing algorithm complexity in any language.