agent-browser

A browser-automation skill for testing web pages and web applications. It can inspect page structure, interact with controls, and capture screenshots.

In plain words
What is it for?
Use it to open a site, inspect its accessibility structure, click or fill interactive elements, test user journeys, investigate browser problems, and save screenshots.
Why use it?
It helps verify what users see and do in a browser, including whether visual changes and form flows work as expected.

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

Made for: Claude Code, Codex.

Per session 32 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,018 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 $0.00032 $0.01018
Opus 5 $0.00016 $0.00509
Sonnet 5 $0.00006 $0.00204
Haiku 4.5 $0.00003 $0.00102

Measured 2d ago against content hash 6c6f82937179, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

agent-browser 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 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.

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/agent-browser/SKILL.md · 140 lines

How it starts

The opening of the file, as written. The whole thing — 140 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agent Browser Skill

Fast browser automation CLI for AI agents. Use this to verify web UI changes, test interactions, and capture screenshots.

When to Use

  • Verify visual changes after modifying frontend code
  • Test form interactions and user flows
  • Capture screenshots for documentation or debugging
  • Inspect rendered HTML/accessibility tree
  • Debug why something isn't working in the browser

Core Workflow

1. Open a URL

agent-browser open http://localhost:4321/

2. Take a Snapshot

The snapshot command returns an accessibility tree with refs (@e1, @e2, etc.) that you can use for interactions:

agent-browser snapshot -i    # -i = interactive elements only (recommended)
agent-browser snapshot -c    # -c = compact (removes empty structural elements)
agent-browser snapshot -i -c # Both flags work together

3. Interact Using Refs

Use the @ref values from the snapshot to interact with elements:

agent-browser click @e5           # Click element
agent-browser fill @e3 "hello"    # Clear and type
agent-browser type @e3 "world"    # Type without clearing
agent-browser select @e7 "option" # Select dropdown
agent-browser check @e9           # Check checkbox

4. Screenshot

agent-browser screenshot              # Viewport only
agent-browser screenshot --full       # Full page
agent-browser screenshot output.png   # Save to file

ALWAYS check the image size before attempting to load. If it is larger than 2MB, process it using a tool such as sips or ImageMagick to reduce the size. Large files cannot be loaded by your tools.

Common Patterns

Form Verification

agent-browser open http://localhost:4321/_emdash/api/setup/dev-bypass?redirect=/_emdash/admin/content/posts/new
agent-browser snapshot -i   # Check what fields are visible
agent-browser fill @e3 "Test Title"
agent-browser fill @e5 "Test content here"
agent-browser click @e7     # Save button

Get Element Info

agent-browser get text @e1      # Get text content
agent-browser get html @e1      # Get inner HTML
agent-browser get value @e2     # Get input value
agent-browser get url           # Current URL
agent-browser get title         # Page title
agent-browser get count "button" # Count matching elements

Read the full file on GitHub · 140 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 · 140 lines · 32 tokens per session scan A 6c6f82937179

Subscribe to this mod's changes

agent-browser is a skill published in the GitHub repository emdash-cms/emdash (12,159 stars, last pushed today), licensed MIT. It adds 32 tokens to every session and 1,018 once invoked, about $0.0002 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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