browser-use-rules

A set of development rules for Browser-Use, an AI agent that navigates websites in a browser to complete user-defined tasks.

In plain words
What is it for?
It is for developing and contributing to Browser-Use, including browser automation, validated action data, documentation, and pre-commit checks.
Why use it?
It gives contributors shared instructions for setting up the project, using the required models and data types, and checking code before submitting changes.

Cursor rule for Cursor

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 rules/therealtimex/browser-use/browser-use-rules
Clone the repo
git clone --depth 1 https://github.com/therealtimex/browser-use

Made for: Cursor.

Per session 442 This file is loaded in full into every session.
When invoked 442 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin fork From a forked repository.
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 $0.00442 $0.00442
Opus 5 $0.00221 $0.00221
Sonnet 5 $0.00088 $0.00088
Haiku 4.5 $0.00044 $0.00044

Measured yesterday against content hash 66833f70b61b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

browser-use-rules 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 yesterday.

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.

.cursor/rules/browser-use-rules.mdc · 62 lines

What it actually says

🧠 General Guidelines for Contributing to browser-use

Browser-Use is an AI agent that autonomously interacts with the web. It takes a user-defined task, navigates web pages using Chromium via CDP, processes HTML, and repeatedly queries a language model (like gpt-4.1-mini) to decide the next action—until the task is completed.


🧰 Development Rules

  • Always use uv instead of pip For deterministic and fast dependency installs.
uv venv --python 3.11
source .venv/bin/activate
uv sync
  • Use real model names Do not replace gpt-4o with gpt-4. The model gpt-4o is a distinct release and supported.

  • Type-safe coding Use Pydantic v2 models for all internal action schemas, task inputs/outputs, and tools I/O. This ensures robust validation and LLM-call integrity.

  • Pre-commit formatting ALWAYS make sure to run pre-commit before making PRs.


Notes:

  • Use descriptive names and docstrings for each action.
  • Prefer returning ActionResult with structured content to help the agent reason better.

🧠 Creating and Running an Agent

To define a task and run a browser-use agent:

from browser_use import Agent, ChatOpenAI

task = "Find the CEO of OpenAI and return their name"
model = ChatOpenAI(model="gpt-4.1-mini")

agent = Agent(task=task, llm=model, tools=tools)

history = await agent.run()

Never create random examples

When I ask you to implement a feature never create new files that show off that feature -> the code just gets messy. If you do anything to test it out, just do the inline code inside the terminal (if you want).

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. yesterday First seen · 62 lines · 442 tokens per session scan A 66833f70b61b

Subscribe to this mod's changes

browser-use-rules is a cursor rule published in the GitHub repository therealtimex/browser-use (0 stars, last pushed 11mo ago), licensed MIT. It adds 442 tokens to every session, about $0.0022 per session on Opus 5. A static security scan graded it A with 0 findings. It comes from a forked repository.