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 agentmods add rules/alonsarias/agent-rules/react-performance-criticalgit clone --depth 1 https://github.com/alonsarias/agent-rulesWhat 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 | $0.00000 | $0.01888 |
| Opus 5 | $0.00000 | $0.00944 |
| Sonnet 5 | $0.00000 | $0.00378 |
| Haiku 4.5 | $0.00000 | $0.00189 |
Grade A, and why
react-performance-critical 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 yesterday.
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 — 310 lines — stays where its author put it; the contents beside it link to each section on GitHub.
React Performance Critical Patterns
Performance optimization guide for React applications. Contains critical rules for eliminating async waterfalls and optimizing bundle size.
1. Eliminating Waterfalls (CRITICAL)
Waterfalls are the #1 performance killer. Each sequential await adds full network latency.
1.1 Defer Await Until Needed
Impact: HIGH - Avoids blocking unused code paths
Move await operations into the branches where they're actually used.
Incorrect: blocks both branches
async function handleRequest(userId: string, skipProcessing: boolean) {
const userData = await fetchUserData(userId)
if (skipProcessing) {
return { skipped: true }
}
return processUserData(userData)
}
Correct: only blocks when needed
async function handleRequest(userId: string, skipProcessing: boolean) {
if (skipProcessing) {
return { skipped: true }
}
const userData = await fetchUserData(userId)
return processUserData(userData)
}
Early return optimization:
// Incorrect: always fetches permissions
async function updateResource(resourceId: string, userId: string) {
const permissions = await fetchPermissions(userId)
const resource = await getResource(resourceId)
if (!resource) {
return { error: 'Not found' }
}
if (!permissions.canEdit) {
return { error: 'Forbidden' }
}
return await updateResourceData(resource, permissions)
}
// Correct: fetches only when needed
async function updateResource(resourceId: string, userId: string) {
const resource = await getResource(resourceId)
if (!resource) {
return { error: 'Not found' }
}
const permissions = await fetchPermissions(userId)
if (!permissions.canEdit) {
return { error: 'Forbidden' }
}
return await updateResourceData(resource, permissions)
}
1.2 Promise.all() for Independent Operations
Impact: CRITICAL - 2-10x improvement
When async operations have no interdependencies, execute them concurrently.
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.
- yesterday First seen · 310 lines · 0 tokens per session scan A 926b14866a31
react-performance-critical is a cursor rule published in the GitHub repository alonsarias/agent-rules (4 stars, last pushed 6mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,888 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 2026-08-31.
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