performance-testing

performance-testing is a skill for Claude Code, Codex from petrkindlmann/qa-skills. It costs 165 tokens per session (4,427 once invoked), scanned A, original, MIT.

A guide for checking how an application behaves under traffic and how quickly its web pages feel to users. It covers k6 load tests, Lighthouse CI, and Core Web Vitals such as loading, responsiveness, and layout stability.

In plain words
What is it for?
Use it to test throughput, latency, load, stress, spikes, and long-running traffic; measure page performance; enforce performance budgets; and investigate bottlenecks.
Why use it?
An application may work correctly for one user but slow down under load or miss page-speed expectations. This helps separate server-capacity problems from browser performance and catch budget violations in CI.

Skill for Claude CodeCodex

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 skills/petrkindlmann/qa-skills/performance-testing
Any agent
npx skills add petrkindlmann/qa-skills --skill performance-testing
Clone the repo
git clone --depth 1 https://github.com/petrkindlmann/qa-skills

Made for: Claude Code, 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.

agentmods badge for performance-testing

README.md
[![agentmods](https://agentmods.dev/badge/skills/petrkindlmann/qa-skills/performance-testing.svg)](https://agentmods.dev/skills/petrkindlmann/qa-skills/performance-testing)
Your own site
<a href="https://agentmods.dev/skills/petrkindlmann/qa-skills/performance-testing"><img src="https://agentmods.dev/badge/skills/petrkindlmann/qa-skills/performance-testing.svg" alt="Measured on agentmods" height="20"></a>
Per session 165 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,427 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00165 $0.04427
Opus 5 $0.00082 $0.02214
Sonnet 5 $0.00033 $0.00885
Haiku 4.5 $0.00016 $0.00443

Measured 5d ago against content hash 0237a4494852, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

performance-testing 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 5d 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.

skills/performance-testing/SKILL.md · 285 lines

How it starts

The opening of the file, as written. The whole thing — 285 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Quick Route

You need to... Go to
Test backend capacity / throughput / latency under traffic k6 Load Testingreferences/recipes.md
Pick a load shape (constant / ramp / spike / soak) Load Profiles table
Measure frontend speed for real users (LCP, INP, CLS) Web Performance + Core Web Vitals
Gate page perf in CI Lighthouse CI (gate TBT, not INP — see below)
A budget is breached and you must find why Bottleneck Identification
Migrate an existing suite from k6 v1 → v2 k6 v2 Migration callout

Discovery Questions

Check .agents/qa-project-context.md first — if it exists, use it and skip questions already answered there.

What to Measure

  • Web performance or load testing? Web performance measures user-perceived speed (Core Web Vitals, page load). Load testing measures server capacity (RPS, latency under load). Most products need both.
  • Which user journeys are performance-critical? Not every endpoint needs load testing. Focus on high-traffic, revenue-critical, or latency-sensitive flows.
  • Existing performance budgets? If yes, what are the targets? If no, this skill helps establish them — measure baseline first.

Current State

  • What is the current baseline? You need numbers before you can set targets. Measure first, then define budgets.
  • What broke due to performance before? Slow pages that lost users, endpoints that timed out under load, queries that locked up — these point at where to focus.
  • Existing monitoring? APM (Datadog, New Relic), RUM, or synthetic probes give you field data to model realistic load.

Read the full file on GitHub · 285 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 5d ago First seen · 285 lines · 165 tokens per session scan A 0237a4494852

Subscribe to this mod's changes

performance-testing is a skill published in the GitHub repository petrkindlmann/qa-skills (108 stars, last pushed 2mo ago), licensed MIT. It adds 165 tokens to every session and 4,427 once invoked, about $0.0008 per session on Opus 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 2026-08-30.

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