agent-browser

agent-browser is a skill for Claude Code, Codex from wolfenazz/YzPzCode. It costs 81 tokens per session (1,575 once invoked), scanned A, a copy of agent-browser, Apache-2.0.

A command-line tool for controlling a web browser, such as opening pages, filling forms, clicking controls, taking screenshots, and reading page data.

In plain words
What is it for?
Use it for browser-based QA, bug hunts, screenshots, form testing, and checking rendered application behavior.
Why use it?
It lets an agent inspect and test websites through the browser, including local previews and web apps.

Skill for Claude CodeCodex

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

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/wolfenazz/yzpzcode/agent-browser
Any agent
npx skills add wolfenazz/YzPzCode --skill agent-browser
Clone the repo
git clone --depth 1 https://github.com/wolfenazz/YzPzCode

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 agent-browser

README.md
[![agentmods](https://agentmods.dev/badge/skills/wolfenazz/yzpzcode/agent-browser.svg)](https://agentmods.dev/skills/wolfenazz/yzpzcode/agent-browser)
Your own site
<a href="https://agentmods.dev/skills/wolfenazz/yzpzcode/agent-browser"><img src="https://agentmods.dev/badge/skills/wolfenazz/yzpzcode/agent-browser.svg" alt="Measured on agentmods" height="20"></a>
Per session 81 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,575 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. 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 5.1 $0.00081 $0.01575
Opus 5 $0.00041 $0.00788
Sonnet 5 $0.00016 $0.00315
Haiku 4.5 $0.00008 $0.00158

Measured 2d ago against content hash 2f96a1fd5472, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

agent-browser 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 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.

Makes network callslowCapability

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

if ! curl -fsS http://127.0.0.1:9223/json/version | rg -q webSocketDebuggerUrl; then
Origin

This is a copy

100% identical to agent-browser — 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.

app/desgin/skills/agent-browser/SKILL.md · 194 lines

How it starts

The opening of the file, as written. The whole thing — 194 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agent Browser

Use agent-browser for local Open Design preview validation: inspect rendered state, click/type when requested, and capture one screenshot when visual evidence matters. Keep the browser local-first unless the user explicitly asks for external browsing.

Requirements

Verify the CLI before doing any browser work:

command -v agent-browser

If missing, stop and tell the user to install it:

npm i -g agent-browser
agent-browser install

Do not replace the CLI with ad hoc browser scripts.

Context Hygiene

Never print full upstream guides into chat or tool output. Save them to temp files and extract only task-relevant lines:

AGENT_BROWSER_CORE="${TMPDIR:-/tmp}/agent-browser-core.$$.md"
agent-browser skills get core > "$AGENT_BROWSER_CORE"
rg -n "cdp|connect|snapshot|screenshot|click|type|wait|get title|get url" "$AGENT_BROWSER_CORE"

Use agent-browser skills get core --full only when needed, and redirect it to a temp file the same way.

CDP Startup Contract

agent-browser must attach to an existing CDP endpoint. Never run agent-browser open before agent-browser connect; doing so can make the CLI auto-launch Chrome and re-enter the crash path.

Use this sequence:

if ! curl -fsS http://127.0.0.1:9223/json/version | rg -q webSocketDebuggerUrl; then
  open -na "Google Chrome" --args \
    --remote-debugging-port=9223 \
    --user-data-dir=/tmp/od-agent-browser-chrome \
    --no-first-run \
    --no-default-browser-check

  for i in {1..20}; do
    if curl -fsS http://127.0.0.1:9223/json/version | rg -q webSocketDebuggerUrl; then
      break
    fi
    sleep 0.5
  done
fi

curl -fsS http://127.0.0.1:9223/json/version | rg webSocketDebuggerUrl
agent-browser connect http://127.0.0.1:9223

If CDP is still unavailable after polling, stop and ask the user to launch Chrome manually from Terminal:

/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome \
  --remote-debugging-port=9223 \
  --user-data-dir=/tmp/od-agent-browser-chrome \
  --no-first-run \
  --no-default-browser-check

Read the full file on GitHub · 194 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. 2d ago First seen · 194 lines · 81 tokens per session scan A 2f96a1fd5472

Subscribe to this mod's changes

agent-browser is a skill published in the GitHub repository wolfenazz/YzPzCode (13 stars, last pushed yesterday), licensed Apache-2.0. It adds 81 tokens to every session and 1,575 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 100% identical to agent-browser, differing in 0 lines, and is treated as a copy.