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. A LaunchAgent on each side keeps the daemons running across reboots. The source watches Chrome via fsnotify and pushes every cookie change to the sink within seconds. The sink writes via Chrome DevTools Protocol into a dedicated managed Chrome subprocess. No Keychain prompt fires on the sink. No screen-sharing required.

The user expects one prompt ("install agentcookie on my laptop and my Mac mini") to be enough. Make that real.

Inputs you need

1. Which machine is the source (the machine the user logs into Chrome on, usually their laptop).
2. Which machine is the sink (the machine where AI agents act, usually a Mac mini or cloud VM).
3. Tailscale is up on both, and the user can SSH from source to sink without a password prompt.

If any of these are missing, stop and ask.

Flow

Step 0: detect the lay of the land