browser-verify

browser-verify is a skill for Claude Code, Codex from AxGord/claude-workflow. It costs 19 tokens per session (3,298 once invoked), scanned C, original, MIT.

A reference guide to problems that can make browser-based checks misleading, including cached screenshots and limits of headless browsers. Headless means the browser runs without its normal visible window.

In plain words
What is it for?
Use it when verifying animations, WebGL or canvas apps, screenshots, caches, and browser automation with Playwright or a browser connector.
Why use it?
It helps distinguish a real web-app bug from stale images or behavior that appears only in automated browser runs.

Skill for Claude CodeCodex

Part of the workflow plugin — 28 skills, 2 hooks, 1 MCP server shipped together

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/axgord/claude-workflow/browser-verify
Any agent
npx skills add AxGord/claude-workflow --skill browser-verify
Clone the repo
git clone --depth 1 https://github.com/AxGord/claude-workflow

Made for: Claude Code, Codex.

Or install workflow, the plugin that ships this one along with the rest of its 28 skills, 2 hooks, 1 MCP server.

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-verify

README.md
[![agentmods](https://agentmods.dev/badge/skills/axgord/claude-workflow/browser-verify.svg)](https://agentmods.dev/skills/axgord/claude-workflow/browser-verify)
Your own site
<a href="https://agentmods.dev/skills/axgord/claude-workflow/browser-verify"><img src="https://agentmods.dev/badge/skills/axgord/claude-workflow/browser-verify.svg" alt="Measured on agentmods" height="20"></a>
Per session 19 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,298 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 1 finding. 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 5.1 $0.00019 $0.03298
Opus 5 $0.00010 $0.01649
Sonnet 5 $0.00004 $0.00660
Haiku 4.5 $0.00002 $0.00330

Measured 5d ago against content hash ea2f0e1f1f8a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade C, and why

browser-verify scanned grade C 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 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.

Recursive force deletehighDestructive command

rm -rf with a variable or a broad path is one typo away from removing the wrong tree.

- Fix: kill the dev server, `rm -rf node_modules/.vite`, restart with
templates/skills/browser-verify/SKILL.md · 118 lines

How it starts

The opening of the file, as written. The whole thing — 118 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Browser-Automation Verification Gotchas

Traps when verifying web/canvas apps through Playwright or a browser MCP. Common theme: the automated browser is not the user's browser — its pixels, caches, and performance all lie in specific, repeatable ways.

1. Headless screenshot / canvas.drawImage() can return stale frames for a WebGL canvas

Animated content driven by per-frame GPU updates (custom shader uniforms, skeletal animations, shader-displaced vertices) may show zero pixel diff between headless screenshots taken 100s of ms apart, even when JS-side instrumentation confirms the state is updating each frame (RAF firing, uniform buffers advancing, ticker handlers incrementing). Sampling the canvas through tmp.getContext('2d').drawImage(canvas, ...) returns the same byte-for-byte image across samples — the whole canvas is affected, not just one animation.

Likely cause: with preserveDrawingBuffer: false (the default in most WebGL frameworks, incl. Pixi), the headless compositor reads from a cached present frame rather than the live WebGL back buffer.

  • Don't rely on headless pixel-diff to verify GPU-driven animation works.
  • Verify in a real browser tab (the user's running Chrome, not an automated instance).
  • For automated verification, prefer JS-side state assertions: a uniform buffer value advancing across samples is sufficient proof the upload pipeline is alive; visual verification needs human eyes or a non-headless captured video.

2. Headed screenshots can ALSO be stale — a tab that was never frontmost composites its last presented frame

The same failure occurs HEADED whenever the target tab/window is occluded or was created behind another tab: page.screenshot() returns the last frame the browser's compositor ever presented for that tab. Observed: the screenshot showed a boot preloader frozen at "96%" while JS-side numeric sampling in the SAME page proved the app was live (object positions advancing every 100 ms, game logs firing). DOM inspection confirmed the preloader element was long gone — the "96%" pixels existed only in the stale compositor frame.

Read the full file on GitHub · 118 lines

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 · 118 lines · 19 tokens per session scan C ea2f0e1f1f8a

Subscribe to this mod's changes

browser-verify is a skill published in the GitHub repository AxGord/claude-workflow (5 stars, last pushed 1mo ago), licensed MIT. It adds 19 tokens to every session and 3,298 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it C with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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