Cat Burglar

Name: Cat Burglar
Author: DrMkdaddy

by DrMkdaddyversion 0.3.3i★ –iRuns on your computer

Registry nameio.github.DrMkdaddy/cat-burglar

Install

Overview

Description from the maker (original English)

Stealth browser MCP with three engines, diff observations, site memory, and benchmarks.

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

User voiceiNo reviews yetReviews open together with accounts in a later step
Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
UsageiVery new★ –

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Connection: Runs on your computer
Transport: stdio
Category: Web & browsers

Install

Pick the AI app you use, then copy the settings.

Before you install

Basic checks: 1 of 1 passed
Runs on your computer with your user’s permissions (files, network, apps).
You fill in yourself: BROWSER_MCP_ALLOW_PRIVATE_NETWORK, BROWSER_MCP_OBSCURA_PATH, BROWSER_MCP_PROFILE

You need

DockerDocker installed

Which app do you use?

ClaudeClaude CodeCursorVS CodeChatGPT

Pick your app above. We remember it, so next time the button says “Install in …”.

Open Claude Desktop → Settings → Developer → Edit Config, and paste this into claude_desktop_config.json

{
  "mcpServers": {
    "cat-burglar": {
      "command": "docker",
      "args": [
        "run",
        "-i",
        "--rm",
        "-e",
        "BROWSER_MCP_ALLOW_PRIVATE_NETWORK",
        "-e",
        "BROWSER_MCP_OBSCURA_PATH",
        "-e",
        "BROWSER_MCP_PROFILE",
        "ghcr.io/drmkdaddy/cat-burglar:v0.3.3"
      ],
      "env": {
        "BROWSER_MCP_ALLOW_PRIVATE_NETWORK": "your-value",
        "BROWSER_MCP_OBSCURA_PATH": "your-value",
        "BROWSER_MCP_PROFILE": "your-value"
      }
    }
  }
}

Run this in your terminal

claude mcp add cat-burglar --env BROWSER_MCP_ALLOW_PRIVATE_NETWORK=your-value --env BROWSER_MCP_OBSCURA_PATH=your-value --env BROWSER_MCP_PROFILE=your-value -- docker run -i --rm -e BROWSER_MCP_ALLOW_PRIVATE_NETWORK -e BROWSER_MCP_OBSCURA_PATH -e BROWSER_MCP_PROFILE ghcr.io/drmkdaddy/cat-burglar:v0.3.3

Fill in the empty values before running it.

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "cat-burglar": {
      "command": "docker",
      "args": [
        "run",
        "-i",
        "--rm",
        "-e",
        "BROWSER_MCP_ALLOW_PRIVATE_NETWORK",
        "-e",
        "BROWSER_MCP_OBSCURA_PATH",
        "-e",
        "BROWSER_MCP_PROFILE",
        "ghcr.io/drmkdaddy/cat-burglar:v0.3.3"
      ],
      "env": {
        "BROWSER_MCP_ALLOW_PRIVATE_NETWORK": "your-value",
        "BROWSER_MCP_OBSCURA_PATH": "your-value",
        "BROWSER_MCP_PROFILE": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "cat-burglar": {
      "type": "stdio",
      "command": "docker",
      "args": [
        "run",
        "-i",
        "--rm",
        "-e",
        "BROWSER_MCP_ALLOW_PRIVATE_NETWORK",
        "-e",
        "BROWSER_MCP_OBSCURA_PATH",
        "-e",
        "BROWSER_MCP_PROFILE",
        "ghcr.io/drmkdaddy/cat-burglar:v0.3.3"
      ],
      "env": {
        "BROWSER_MCP_ALLOW_PRIVATE_NETWORK": "your-value",
        "BROWSER_MCP_OBSCURA_PATH": "your-value",
        "BROWSER_MCP_PROFILE": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

This one runs on your computer, and ChatGPT can only connect to servers on the internet. Pick another app.

Your choice stays on this device in a cookie; no account needed.

Values you fill in

BROWSER_MCP_ALLOW_PRIVATE_NETWORK env
Set to 1 to allow localhost and private-network pages.
BROWSER_MCP_OBSCURA_PATH env
Path to the Obscura binary when it is not on PATH.
BROWSER_MCP_PROFILE env
Observation profile: local, flash, frontier, or auto.

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

Runs on your computer; the tool list appears in your AI app after you install it.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 10, 2026

✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account DrMkdaddy, which owns the repo
… Not checked yet
Still maintained
We have not read this repo from GitHub yet
… Not checked yet
Has a licence
We have not read this repo from GitHub yet
– Not applicable
Endpoint responds
This one runs on your computer; there is no internet endpoint
– Not applicable
Sign-in with OAuth
Runs on your computer and uses local settings instead
… Not checked yet
No hidden instructions in tool descriptions
Runs on your computer; we can only read tool lists from internet endpoints

Compared with others in Web & browsersi

More stars than 0% of the other 1422 servers in this category
Published to the registry more recently than 99% of the other 1422 servers in this category
Basic checks equal to or better than 100% of the other 1422 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is Cat Burglar safe?

It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

The registry does not list a required key, though some servers ask you to sign in on first use.

Does it run on my computer or in the cloud?

It runs on your computer. Your AI app starts it when needed, and data does not pass through the maker’s servers (unless it calls an online service itself).

Is it still maintained?

The GitHub repo last changed –, and the latest version (0.3.3) reached the registry today.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. You also need Docker on your computer.

What can I use instead?

In the same category: Browser Use, Chrome DevTools MCP, MCP Server Browser

Alternatives

Servers in the same category from other makers, sorted by stars.

Reading a card:↓ Downloads per weeki★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

Browser Use

Lets AI do web tasks for you, such as filling forms, searching and extracting data, in the maker’s cloud browsers or on your computer.

by browser-useWidely used↓ 1.6M/wk★ 120.1KUpdated 20 days ago

Computer or cloud✓ browser-use.com

Install

Chrome DevTools MCP

Lets AI use Chrome’s developer tools to inspect pages, find what makes them slow and spot errors. Made by the Chrome DevTools team.

by ChromeDevToolsWidely used↓ 1.9M/wk★ 54.8KUpdated 19 days ago

Runs on your computer

Install

MCP Server Browser

MCP server for browser use access

by bytedanceWidely used↓ 792/wk★ 39.6KUpdated 14 months ago

Runs on your computer

Install

README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

Cat Burglar

Three browsers. One MCP. Only the changes.

Cat Burglar plugs a real browser into your agent. It can run patched stealth Chromium, stock Chromium for devtools, or Obscura's 43 MB Rust engine behind one session. It sends diffs instead of full DOM dumps, remembers per-site workflows, and gates high-impact actions.

What you get

Feature	Why it matters
Three engines, one server	Pick stealth, devtools fidelity, or a 43 MB footprint for the task. Switch without changing clients.
Diffs, not dumps	Stable refs, diff snapshots, and bounded change observations after every action. Less context, fewer round trips.
Site memory	Per-origin hints and workflows learned after a successful run. Repeated tasks get shorter.
Guardrails on by default	SSRF protection, origin lists, untrusted-content markers, tracker blocking, and a confirmation gate for destructive actions.
Works with your agent	Claude Desktop, Claude Code, Cursor, Codex, Gemini CLI, VS Code, Windsurf, Cline, OpenCode, Docker, and any stdio client.
Measured	A 12-task local suite with state verification. Adaptive observation cuts text by 29.9% and calls by 15% at the same success rate.

Install

One line:

curl -fsSL https://raw.githubusercontent.com/DrMkdaddy/cat-burglar/main/scripts/install.sh | bash

From the official MCP Registry: io.github.DrMkdaddy/cat-burglar (OCI image). From GHCR: docker run -i --rm ghcr.io/drmkdaddy/cat-burglar:latest.

The installer adds a cat-burglar binary to your PATH. Install globally with pnpm if you prefer:

pnpm add -g https://github.com/DrMkdaddy/cat-burglar/releases/download/v0.3.3/cat-burglar-mcp-0.3.3.tgz

cat-burglar doctor

The install command prints a ready config for: claude-code, claude-desktop, cursor, codex, gemini, vscode, windsurf, cline, opencode, or generic.

Works with

Client	Setup
Claude Code	`claude mcp add catburglar -- cat-burglar`
Claude Desktop, Cursor, Windsurf, Cline	Paste the `mcpServers` JSON from `docs/install.md`
Codex	`codex mcp add catburglar -- cat-burglar`
Gemini CLI	Add the `mcpServers` entry to `~/.gemini/settings.json`
VS Code	Add the `servers` entry to `.vscode/mcp.json`
OpenCode	Add `catburglar` under `mcp.servers`
Docker	`docker run -i --rm ghcr.io/drmkdaddy/cat-burglar:latest`

Do not name the server browser. OpenCode has a built-in browser toolset with that name, and Code Mode hides overlapping tools.

Copy this prompt into your agent

Quick version:

Install Cat Burglar from https://github.com/DrMkdaddy/cat-burglar as a local MCP server named catburglar.

Run: curl -fsSL https://raw.githubusercontent.com/DrMkdaddy/cat-burglar/main/scripts/install.sh | bash

Then run cat-burglar doctor.

Add the server with command cat-burglar (add --slim if the client loads every tool schema), restart or reconnect the client, and verify by navigating to https://example.com and taking a snapshot. Report the tool count, engine, and page title.

Full base prompt with client-specific steps, verification, and security rules: docs/agent-prompt.md.

<system_context>

You are installing Cat Burglar, a local browser MCP server, for this project.

Add Cat Burglar to the current MCP client and verify that it can drive a browser.

Run: curl -fsSL https://raw.githubusercontent.com/DrMkdaddy/cat-burglar/main/scripts/install.sh | bash Then run cat-burglar doctor and report the output.
Add a local stdio MCP server named catburglar that runs cat-burglar. If the client loads every tool schema into context, add --slim.
Do not use the name browser. It collides with OpenCode's built-in browser tools.
Enable BROWSER_MCP_ALLOW_PRIVATE_NETWORK=1 only if the user needs localhost.
Restart or reconnect the MCP client.
Verify with navigate to https://example.com, then snapshot, then close.

Report the server name, the tool count, the engine, and the title returned by the test page.

Do not commit secrets. Do not enable private-network access without asking. Use the measured 12-task local numbers if numbers are needed. Do not invent a head-to-head result.

Install and verify Cat Burglar for my agent.

Example prompts

Research:

Use catburglar. Open https://news.ycombinator.com, take a snapshot, read the top five stories with markdown, and give me the titles and links.

Forms and workflows:

Use catburglar. Open the staging signup page, fill the form with test data, submit it, and tell me exactly what changed on the page.

Local app testing:

Use catburglar with engine chromium. Open http://localhost:3000, log in with the seeded test user, open the billing page, capture a screenshot, and report console errors.

Performance:

Use catburglar with engine chromium. Open the product page, start a performance trace, reload, stop the trace, and summarize the long tasks and the three slowest scripts.

Three browsers

Engine	Best for	Footprint
`patchright`	Protected sites, logins, anti-bot work	Full Chromium
`chromium`	Devtools, console, traces, PDF, local app testing	Full Chromium
`obscura`	High-volume reads and low-memory work	About 43 MB

{ "engine": "obscura", "restart": true }

A running browser cannot change engines in place. Call open with restart: true.

The loop

navigate to a page.
snapshot to get URL, title, controls, and stable refs.
click, fill, or select by ref.
Read the change observation returned by the action.
Use markdown to read, extract for structured data, and perf for traces.
Run memory learn after a successful repeatable workflow.

Refs stay valid while the element remains in the DOM. If an element leaves the page, the action fails with a stale-ref error instead of clicking a clone.

Benchmark

Mode	Success	Tool calls	Observation chars	Wall time
Full snapshots	12/12	80	30,029	15.37 s
Diff + change observation	12/12	68	21,057	13.86 s

Measured on a 12-task local suite with server-side state checks. Profile flash, engine chromium, Node 26. Raw JSON: bench/results/2026-11-09-flash.json.

pnpm bench

pnpm bench:compare

Tools

30 tools by default. 14 in --slim mode.

Group	Tools
Lifecycle	`open`, `close`, `navigate`, `back`, `forward`, `reload`, `status`, `tabs`
Reading	`snapshot`, `markdown`, `extract`, `evaluate`, `screenshot`, `pdf`
Interaction	`click`, `fill`, `type`, `press`, `select`, `hover`, `scroll`, `upload`, `wait`
State	`cookies`, `storage`, `stealth`, `memory`
Diagnostics	`network`, `console`, `perf`

extract covers links, tables, JSON-LD, meta tags, text, and CSS field maps. perf covers web vitals, CDP metrics, slow resources, and full Chrome traces.

Safety

SSRF protection on navigation and every request, with DNS checks and redirect coverage.
Private, loopback, link-local, CGNAT, multicast, and reserved ranges are blocked unless explicitly allowed.
Cloud metadata endpoints stay blocked even with private-network access on.
Origin allow and block lists with wildcard hosts.
Page-derived output carries an untrusted-content marker.
High-impact targets such as delete, pay, transfer, send, publish, and deactivate are flagged. Set BROWSER_MCP_RISKY_ACTION_POLICY=ask to require explicit confirmation.
Site memory is agent-authored only. Page text is never ingested, refs are dropped, and typed values become placeholders.
Tracker blocking uses Obscura's 3,520-domain PGL list plus common analytics hosts.

Use these as layers in a defense-in-depth setup. For sensitive accounts, run with the ask policy and review the confirmation before approving.

Research

The design follows a review of 2023 to 2026 web-agent work: evaluation error, observation alignment, change observation, memory, planning, and prompt injection. Full review with 40 sources: docs/research/2026-11-browser-agent-research.md.

The LLM harness can run the same 12 tasks against ours, playwright, chrome-devtools, or obscura:

pnpm bench:llm -- --server ours

Develop

pnpm install

pnpm build pnpm test pnpm smoke pnpm bench pnpm bench:compare node dist/index.js doctor node dist/index.js install --client claude-desktop

Config file: ~/.config/browser-mcp/config.json. Example: cat-burglar.config.example.json. Environment variables override it.

Credits

Source	License	What we used
Obscura	Apache-2.0	Ref-token snapshot ideas, markdown and extract semantics, SSRF posture, tracker list data
Playwright MCP	Apache-2.0	Accessibility-first snapshots, persistent profiles, origin and file policy
Chrome DevTools MCP	Apache-2.0	Performance metrics and traces, network and console inspection
Patchright	Apache-2.0	Stealth Playwright driver
browser-use	MIT	Agent action vocabulary and humanized interaction ideas

The tracker list is the only copied data asset. See NOTICE.

Status

Version 0.3.3. Benchmarked on a 12-task local suite with raw JSON in the repo. The LLM harness can run the same tasks across four servers. Issues and counterexamples are welcome.

License

MIT. See LICENSE.

Cat Burglar

Overview

PopNx MCP’s three pillars

What you can do with it

Install

Before you install

Values you fill in

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Compared with others in Web & browsersi

Common questions

Alternatives

Browser Use

Chrome DevTools MCP

MCP Server Browser

README from the maker

Cat Burglar

Three browsers. One MCP. Only the changes.

What you get

Install

Works with

Copy this prompt into your agent

Example prompts

Three browsers

The loop

Benchmark

Tools

Safety

Research

Develop

Credits

Status

License