aem-three-phase-performance

A performance rule for Adobe Experience Manager sites that divides page loading into eager, lazy, and delayed phases. It defines what should load before the largest visible element and what can wait until later.

In plain words
What is it for?
Use it when implementing or reviewing AEM performance work, including first-section rendering, lazy loading, delayed third-party scripts, and the 100 KB early-loading budget.
Why use it?
It helps keep the first screen fast by limiting early resources, loading below-the-fold content later, and postponing third-party code.

Cursor rule for Cursor

Install

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.

agentmods
npx agentmods add rules/adobecom/express-milo/aem-three-phase-performance
Clone the repo
git clone --depth 1 https://github.com/adobecom/express-milo

Made for: Cursor.

Per session 220 This file is loaded in full into every session.
When invoked 220 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00220 $0.00220
Opus 5 $0.00110 $0.00110
Sonnet 5 $0.00044 $0.00044
Haiku 4.5 $0.00022 $0.00022

Measured 2d ago against content hash 8ba855f75079, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

aem-three-phase-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 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.

Origin

This is a copy

100% identical to aem-three-phase-performance — 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.

.cursor/rules/aem-three-phase-performance.mdc · 32 lines

What it actually says

AEM Three-Phase Loading (E-L-D)

APPLY: EVERY PERFORMANCE QUERY

Phase Assignment

Phase E (Eager): LCP elements, <100KB, single origin Phase L (Lazy): Below-fold, same-origin enhancement
Phase D (Delayed): Third-party, 3+ seconds after LCP

Phase E Budget Rules

  • 100KB total before LCP
  • Single origin only (no CDNs, fonts, APIs)
  • Essential AEM CSS (required for transformations)
  • First section only

Implementation Pattern

// ✅ Phase E: LCP structure immediately
export default async function init(el) {
  const isFirstSection = el.closest('.section') === document.querySelector('.section');
  
  if (isFirstSection) {
    // Phase E: Create LCP DOM immediately
    createLCPStructure(el);
  } else {
    // Phase L: Lazy load with intersection observer
    setupLazyLoading(el);
  }
}
Changes

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.

  1. 2d ago First seen · 32 lines · 220 tokens per session scan A 8ba855f75079

Subscribe to this mod's changes

aem-three-phase-performance is a cursor rule published in the GitHub repository adobecom/express-milo (6 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 220 tokens to every session, about $0.0011 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to aem-three-phase-performance, differing in 0 lines, and is treated as a copy.