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/adobecom/express-milo/css-render-blocking-diagnosisgit clone --depth 1 https://github.com/adobecom/express-miloWhat 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 | $0.01102 | $0.01102 |
| Opus 5 | $0.00551 | $0.00551 |
| Sonnet 5 | $0.00220 | $0.00220 |
| Haiku 4.5 | $0.00110 | $0.00110 |
Grade A, and why
css-render-blocking-diagnosis 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 2d 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.
This is a copy
100% identical to css-render-blocking-diagnosis — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 139 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CSS Render-Blocking Diagnosis & Resolution
APPLY: EVERY PERFORMANCE QUERY - PRIMARY DIAGNOSTIC RULE
Critical Learning from 98 PageSpeed Achievement
This rule documents the breakthrough that achieved 98-91 PageSpeed scores by solving CSS render-blocking bottlenecks.
Primary Diagnostic Protocol
Step 1: CSS Blocking Symptom Recognition
IMMEDIATE RED FLAGS requiring CSS investigation:
- LCP > 3 seconds with white screen pattern
- Body/content delayed despite JavaScript optimizations
- Performance scores stuck at 80-85 despite component work
- Render delay >70% in LCP performance breakdown
- "Body doesn't show until late" user complaints
Step 2: CSS Loading Sequence Audit
Check these patterns in loading order:
# 1. Confirm body hiding pattern (correct)
grep -r "body.*display.*none" head.html
# 2. Find CSS loading mechanism (potential issue)
grep -r "createElement.*link" scripts.js
grep -r "stylesheet" scripts.js
# 3. Check CSS file sizes (>20KB = likely blocking)
ls -la */styles/styles.css
Step 3: Root Cause Confirmation
Render-blocking CSS anti-pattern:
// ❌ PROBLEM: Large CSS via JavaScript = render blocking
(function loadStyles() {
const paths = [`${miloLibs}/styles/styles.css`]; // 27KB file
paths.forEach((path) => {
const link = document.createElement('link');
link.setAttribute('rel', 'stylesheet');
link.setAttribute('href', path); // BLOCKS body visibility
document.head.appendChild(link);
});
}());
The Solution Implementation
Phase E: Optimize Block Loading Speed
// ✅ SOLUTION: Focus on LCP element structure creation speed
// Following AEM Three-Phase Loading principles
export default async function init(el) {
// Phase 1: Create LCP structure synchronously (REQUIRED for performance)
const lcpContent = createBasicStructure(el);
el.append(lcpContent);
// Phase 2: CSS loading optimized for AEM transformation phases
// body { display: none; } stays until data-block-status="loaded"
return lcpContent; // Return immediately for LCP measurement
}
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.
- 2d ago First seen · 139 lines · 1,102 tokens per session scan A d768ad20abec
css-render-blocking-diagnosis is a cursor rule published in the GitHub repository adobecom/express-milo (6 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 1,102 tokens to every session, about $0.0055 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to css-render-blocking-diagnosis, differing in 0 lines, and is treated as a copy.
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