What is performance-optimizer?

A set of instructions for finding and improving real software performance problems, such as slow loading, large bundles, rendering delays, or memory leaks.

Use it for profiling, Core Web Vitals, bundle-size reduction, rendering improvements, and runtime performance analysis.

It keeps optimization focused on measured bottlenecks instead of speculative changes.

performance-optimizer — Skill for Codex by lsantosweb

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.

Any agent

npx skills add lsantosweb/codex-agents-skills-kit --skill performance-optimizer

Clone the repo

git clone --depth 1 https://github.com/lsantosweb/codex-agents-skills-kit

Made for: Codex.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/lsantosweb/codex-agents-skills-kit/performance-optimizer/github.svg)](https://agentmods.dev/skills/lsantosweb/codex-agents-skills-kit/performance-optimizer)

Your own site

<a href="https://agentmods.dev/skills/lsantosweb/codex-agents-skills-kit/performance-optimizer"><img src="https://agentmods.dev/badge/skills/lsantosweb/codex-agents-skills-kit/performance-optimizer/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/lsantosweb/codex-agents-skills-kit/performance-optimizer"><img src="https://agentmods.dev/badge/skills/lsantosweb/codex-agents-skills-kit/performance-optimizer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 27 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 214 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found 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.

Model	Per session	Once invoked
Fable 5.1	$0.00027	$0.00214
Opus 5.5	$0.00011	$0.00086
Sonnet 5.5	$0.00005	$0.00043
Haiku 4.5	$0.00003	$0.00021

Measured 2mo ago against content hash 67fbfacbae9d, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

performance-optimizer 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 2mo 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.

.codex/skills/performance-optimizer/SKILL.md · 42 lines

What it actually says

When to use

Use this skill for:

Lighthouse issues
LCP, INP, CLS work
bundle size review
runtime slowdowns
memory leaks
rendering bottlenecks

Core operating rules

Measure first.
Optimize the largest real bottleneck first.
Re-measure after each significant change.
Favor user-perceived performance improvements.

Workflow

Define the performance symptom.
Choose the right measurement source.
Identify the biggest bottleneck.
Apply the smallest high-impact change.
Validate the gain.

Targets

LCP < 2.5s
INP < 200ms
CLS < 0.1

Mandatory checks

explicit before/after reasoning
bundle, image, rendering, and network dimensions considered when relevant
no speculative optimization without evidence

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.

2mo ago First seen · 42 lines · 27 tokens per session scan A 67fbfacbae9d

Subscribe to this mod's changes

performance-optimizer is a skill published in the GitHub repository lsantosweb/codex-agents-skills-kit (2 stars, last pushed 7mo ago), licensed MIT. It adds 27 tokens to every session and 214 once invoked, about $0.0001 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 2026-08-31.

Debugging

performance-optimizer next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
performance-optimizerlsantosweb/codex-agents-skills-kit	Skill	2	7mo ago	MIT	A	27	Codex
systematic-debuggingopen-metadata/OpenMetadata	Skill	16k	yesterday	Apache-2.0	A	37	Claude Code
log-error-digestzebbern/claude-code-guide	Skill	4.7k	3d ago	MIT	A	71	Claude Code, Codex
cwv-optimizeradobe/skills	Skill	319	yesterday	Apache-2.0	A	112	Claude Code
ci-fixersipyourdrink-ltd/bernstein	Skill	1.2k	yesterday	Apache-2.0	A	15	Claude Code, Codex
incident-response-incident-responsermyndharis/antigravity-skills	Skill	1.9k	23d ago	MIT	A	36	Claude Code
triaging-web-analytics-supportPostHog/posthog	Skill	41k	yesterday	none	A	151	Claude Code, Codex