agentcookie-install

agentcookie-install is a skill for Claude Code, Codex from mvanhorn/agentcookie. It costs 63 tokens per session (2,259 once invoked), scanned B, original, MIT.

An installation workflow that keeps Chrome cookies synchronised between a Mac where you log in and a second Mac or Linux machine where an AI agent works. Cookies are small browser files that preserve sign-ins and session settings.

In plain words
What is it for?
Use it to set up the source and sink machines, pair them, and keep Chrome sessions updated automatically, including injecting cookies into a running Linux Chrome session.
Why use it?
It removes the need to log in again on the agent machine whenever a Chrome session changes. The two machines must be connected through Tailscale, a private network service.

Skill for Claude CodeCodex

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

Good fit Use it to set up the source and sink machines, pair them, and keep Chrome sessions updated automatically, including injecting cookies into a running Linux Chrome session.

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Install with agentmods
npx agentmods add skills/mvanhorn/agentcookie/skill
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.

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

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 agentcookie-install

README.md
[![agentmods](https://agentmods.dev/badge/skills/mvanhorn/agentcookie/skill/github.svg)](https://agentmods.dev/skills/mvanhorn/agentcookie/skill)
Your own site
<a href="https://agentmods.dev/skills/mvanhorn/agentcookie/skill"><img src="https://agentmods.dev/badge/skills/mvanhorn/agentcookie/skill/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for agentcookie-install

Your own site · 80×15
<a href="https://agentmods.dev/skills/mvanhorn/agentcookie/skill"><img src="https://agentmods.dev/badge/skills/mvanhorn/agentcookie/skill.svg" alt="Reviewed on agentmods" width="80" 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 2,259 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 6 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high YARA Match · line 3
    YARA rule matched a known malware signature (reverse shell, backdoor, ransomware, C2 framework, or info stealer).
    Fix: Remove the malware payload or compromised file entirely. Investigate how it entered the skill and audit all other artifacts for additional indicators of compromise.
  • medium Privilege Escalation · line 51
    Commands invoke sudo or root privileges. Verify this elevated access is necessary and justified.
    Fix: Avoid sudo/root unless strictly required. Prefer least-privilege patterns. If elevation is needed, document the justification and scope.
  • medium Rogue Agent · line 82
    Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.
    Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
  • medium Privilege Escalation · line 90
    Commands invoke sudo or root privileges. Verify this elevated access is necessary and justified.
    Fix: Avoid sudo/root unless strictly required. Prefer least-privilege patterns. If elevation is needed, document the justification and scope.
  • medium Rogue Agent · line 159
    Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.
    Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
  • medium Rogue Agent · line 178
    Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.
    Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
How audits are shown
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 $0.02259
Opus 5.5 $0.00025 $0.00904
Sonnet 5.5 $0.00013 $0.00452
Haiku 4.5 $0.00006 $0.00226

Measured 27d ago against content hash 1af38daca23a, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade B, and why

agentcookie-install scanned grade B with 2 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 27d 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.

Asks for rootmediumPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

sudo mv agentcookie /usr/local/bin/

Makes network callslowCapability

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

curl -LO https://github.com/mvanhorn/agentcookie/releases/download/v1.0.0/agentcookie_1.0.0_darwin_arm64.tar.gz
skill/SKILL.md · 242 lines

How it starts

The opening of the file, as written. The whole thing — 242 lines — stays where its author put it; the contents beside it link to each section on GitHub.

agentcookie install

You are helping the user install agentcookie on two machines that are both on the same Tailscale tailnet, then pair them, so that the sink's Chrome stays continuously in sync with the source's Chrome.

After install, the user does not touch agentcookie again. The source watches Chrome via fsnotify and pushes every cookie change to the sink within seconds. On Linux, the sink injects cookies via CDP into an already-running Chrome. On macOS, a LaunchAgent keeps the daemon running across reboots.

Inputs you need

  1. Which machine is the source (the Mac the user logs into Chrome on, usually their laptop).
  2. Which machine is the sink (where AI agents act - a Linux VM like Grok Bot, or a second Mac).
  3. Tailscale is up on both.
  4. On Linux: Chrome is running with --remote-debugging-port=9223 (or another port).

If any of these are missing, stop and ask.

Step 0: detect the lay of the land

Run on the current machine:

uname -s  # Darwin = macOS, Linux = Linux
tailscale status 2>&1 | head -20

From the Tailscale status output, identify which host is the Mac and which is the Linux box.

Step 1: confirm source vs sink with the user

Use the platform's blocking question primitive. Phrase it concretely:

I see you're on <current-hostname>. Looks like <other-hostname> (Tailscale IP 100.x.y.z) is your other machine. Should I install agentcookie with <current-hostname> as the source (your logged-in Chrome) and <other-hostname> as the sink (where your agents run)?

Confirm before proceeding. If wrong, ask which is which.

Step 2: install on the Mac source

Install the binary if missing:

# Download from GitHub Releases
curl -LO https://github.com/mvanhorn/agentcookie/releases/download/v1.0.0/agentcookie_1.0.0_darwin_arm64.tar.gz
tar -xzf agentcookie_1.0.0_darwin_arm64.tar.gz
sudo mv agentcookie /usr/local/bin/

Or build from source:

go install github.com/mvanhorn/agentcookie/cmd/[email protected]

Read the full file on GitHub · 242 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 27d ago Changed · +2 lines 1af38daca23a
  2. 1mo ago First seen · 240 lines · 63 tokens per session scan B bad7392e5498

Subscribe to this mod's changes

agentcookie-install is a skill published in the GitHub repository mvanhorn/agentcookie (854 stars, last pushed 4d ago), licensed MIT. It adds 63 tokens to every session and 2,259 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it B with 2 findings (asks for root, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.