browser-testing

browser-testing is a skill for Claude Code, Codex from benchflow-ai/skillsbench. It costs 49 tokens per session (1,578 once invoked), scanned A, original, Apache-2.0.

A browser-testing guide for checking whether web changes affect loading speed, layout stability, or page flickering. It uses Playwright, a tool that controls and measures browsers.

In plain words
What is it for?
Use it before and after frontend changes to measure page or API performance, inspect network timing, and check for layout shifts or flicker.
Why use it?
It helps find visual shifts, theme flashes, slow requests, and other problems that may not be obvious from reading the code.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it before and after frontend changes to measure page or API performance, inspect network timing, and check for layout shifts or flicker.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/benchflow-ai/skillsbench/browser-testing
About the project

SkillsBench is a benchmark for measuring how effectively AI agents use modular skills—folders containing instructions, scripts, and resources—to complete specialized tasks. It helps researchers and developers evaluate both skill quality and agent behavior, including tasks that require combining multiple skills. The catalogue’s skills and instructions are evaluated as part of this workflow.

benchflow-ai/skillsbench · 1,757 stars · on GitHub · skillsbench.ai

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 benchflow-ai/skillsbench --skill browser-testing
Clone the repo
git clone --depth 1 https://github.com/benchflow-ai/skillsbench

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 browser-testing

README.md
[![agentmods](https://agentmods.dev/badge/skills/benchflow-ai/skillsbench/browser-testing/github.svg)](https://agentmods.dev/skills/benchflow-ai/skillsbench/browser-testing)
Your own site
<a href="https://agentmods.dev/skills/benchflow-ai/skillsbench/browser-testing"><img src="https://agentmods.dev/badge/skills/benchflow-ai/skillsbench/browser-testing/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.

agentmods 80×15 button for browser-testing

Your own site · 80×15
<a href="https://agentmods.dev/skills/benchflow-ai/skillsbench/browser-testing"><img src="https://agentmods.dev/badge/skills/benchflow-ai/skillsbench/browser-testing.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 49 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,578 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 5.1 $0.00049 $0.01578
Opus 5 $0.00024 $0.00789
Sonnet 5 $0.00010 $0.00316
Haiku 4.5 $0.00005 $0.00158

Measured 6d ago against content hash cb1a9611c3d0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

browser-testing scanned grade A with 1 finding 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 6d ago.

The scan reads SKILL.md. This mod also ships 3 executable files (detect-flicker.ts, measure-cls.ts, measure.ts), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

const response = await fetch(url);
Origin

Copies of this mod

1 near-identical copy found in the catalogue:

tasks/fix-visual-stability/environment/skills/browser-testing/SKILL.md · 200 lines

How it starts

The opening of the file, as written. The whole thing — 200 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Performance Measurement with Playwright CDP

Diagnose performance issues by measuring actual load times and network activity.

Playwright is pre-installed. Just use the measurement script.

Quick Start

A measure.ts script is included in this skill's directory. Find it and run:

# Measure a page (outputs JSON with waterfall data)
npx ts-node <path-to-this-skill>/measure.ts http://localhost:3000

# Measure an API endpoint
npx ts-node <path-to-this-skill>/measure.ts http://localhost:3000/api/products

The script is in the same directory as this SKILL.md file.

Understanding the Output

The script outputs JSON with:

{
  "url": "http://localhost:3000",
  "totalMs": 1523,
  "requests": [
    { "url": "http://localhost:3000/", "ms": 45.2 },
    { "url": "http://localhost:3000/api/products", "ms": 512.3 },
    { "url": "http://localhost:3000/api/featured", "ms": 301.1 }
  ],
  "metrics": {
    "JSHeapUsedSize": 4521984,
    "LayoutCount": 12,
    "ScriptDuration": 0.234
  }
}

Reading the Waterfall

The requests array shows network timing. Look for sequential patterns:

BAD (sequential - each waits for previous):
  /api/products    |████████|                        512ms
  /api/featured             |██████|                 301ms  (starts AFTER products)
  /api/categories                  |████|            201ms  (starts AFTER featured)
  Total: 1014ms

GOOD (parallel - all start together):
  /api/products    |████████|                        512ms
  /api/featured    |██████|                          301ms  (starts SAME TIME)
  /api/categories  |████|                            201ms  (starts SAME TIME)
  Total: 512ms (just the slowest one)

Key Metrics

Metric What it means Red flag
totalMs Total page load time > 1000ms
JSHeapUsedSize Memory used by JS Growing over time
LayoutCount Layout recalculations > 50 per page
ScriptDuration Time in JS execution > 0.5s

Read the full file on GitHub · 200 lines

Files

What ships with it

3 files 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. 6d ago First seen · 200 lines · 49 tokens per session scan A cb1a9611c3d0

Subscribe to this mod's changes

browser-testing is a skill published in the GitHub repository benchflow-ai/skillsbench (1,757 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 49 tokens to every session and 1,578 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.