co-browser

co-browser is a skill for Claude Code, Codex from openonion/connectonion. It costs 63 tokens per session (3,160 once invoked), scanned A, original, Apache-2.0.

A shell-controlled browser that stays open between commands, keeping its tabs, cookies, and logged-in sessions. It lets multiple agents share the same browser while identifying which caller is controlling it.

In plain words
What is it for?
Use it to open pages, sign in, read or scrape content, fill out forms, upload files, take screenshots, and automate browser tasks.
Why use it?
It removes repeated logins and makes multi-step browser work persistent. It also helps avoid agents silently taking control of the same page at the same time.

Skill for Claude CodeCodex

About the project

ConnectOnion is an open-source, template-first toolkit for building, debugging, deploying, and operating AI agents. Developers use its command-line tools and Python runtime to create agents, add tools, connect services, deploy them, and make them callable by other agents, while the catalogue entries are related agents, skills, and instructions.

openonion/connectonion · 1,481 stars · on GitHub · docs.connectonion.com

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

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 co-browser

README.md
[![agentmods](https://agentmods.dev/badge/skills/openonion/connectonion/co-browser.svg)](https://agentmods.dev/skills/openonion/connectonion/co-browser)
Your own site
<a href="https://agentmods.dev/skills/openonion/connectonion/co-browser"><img src="https://agentmods.dev/badge/skills/openonion/connectonion/co-browser.svg" alt="Measured on agentmods" height="20"></a>
Per session 63 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,160 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 5.1 $0.00063 $0.03160
Opus 5 $0.00032 $0.01580
Sonnet 5 $0.00013 $0.00632
Haiku 4.5 $0.00006 $0.00316

Measured 6d ago against content hash 9a2d9346253e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

co-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 6d 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.

connectonion/useful_skills/co-browser/SKILL.md · 275 lines

How it starts

The opening of the file, as written. The whole thing — 275 lines — stays where its author put it; the contents beside it link to each section on GitHub.

co browser Skill

Drive one real browser from the shell. The browser stays open between commands — cookies and logins persist until co browser close. Every terminal on the machine talks to the same daemon: one browser, one board, no matter where you type.

Always read the output, not just the exit code. A failed action (selector not found, browser not open) often returns exit 0 with the error text on stdout — never chain co browser ... && next_step as your only success check.

Step 1: Identity — who are you?

The daemon attributes every tab to a caller and uses that identity to stop two agents from silently driving the same page. Set CO_WHO explicitly — shell state does not survive between your tool calls, so a lone export is lost. Either prefix every command:

CO_WHO=alice co browser go_to example.com

or keep the export and the commands in the SAME shell invocation:

export CO_WHO=alice && co browser go_to example.com && co browser get_text

(Some environments — e.g. Claude Code background jobs — are auto-identified, but setting CO_WHO is always safe and never worse.) An anonymous caller still works but gets no contention protection.

Step 2: Check the board, then claim a tab

One task = one tab. Before touching the browser, see what's already happening:

co browser status      # browser state, headless flag, last command, the board
co browser tab ls      # every tab: who owns it, purpose, last command (--json for scripting)

Solo (nobody else on the board) — bare commands run on the shared main tab, no ceremony:

co browser go_to example.com     # runs on 'main'
co browser get_text              # still 'main'

Concurrent (another agent or a second parallel task exists) — open your own tab and add -t <name> to EVERY command, including do. Pick an explicit literal tab name — a NAME=$(...) capture is lost between tool calls:

CO_WHO=alice co browser tab open scrape --for "scrape pricing" --needs 10m
CO_WHO=alice co browser -t scrape go_to example.com/pricing
CO_WHO=alice co browser -t scrape do "extract every plan and its monthly price"
CO_WHO=alice co browser tab close scrape       # release when done

Read the full file on GitHub · 275 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. 6d ago First seen · 275 lines · 63 tokens per session scan A 9a2d9346253e

Subscribe to this mod's changes

co-browser is a skill published in the GitHub repository openonion/connectonion (1,481 stars, last pushed today), licensed Apache-2.0. It adds 63 tokens to every session and 3,160 once invoked, about $0.0003 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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