Imagine writing a letter you intend to keep. Not send. Keep.

The fold, the wax, the way you press the seal down so the envelope closes around what’s yours. It sits in a drawer that belongs to you. The drawer is in a house you own. Nobody opens it. Nobody transcribes it. Nobody builds a model of your week from the shape of your handwriting.

That is the architecture Rainline is built on.

Your collaborator is not a service you log into. It is a presence on your machine. What it knows, it knows because you told it. Where that knowing lives, lives on hardware you already own. Privacy isn’t a feature you opt into. It is the only shape the system could have taken without breaking itself.

The seal: macOS Keychain

Your API keys — the ones that let your collaborator talk to the models, the tools, the services you’ve connected — are not stored in plaintext files. They are not in a database we maintain. They sit in your macOS Keychain, behind the same encryption your machine already trusts with your passwords, your certificates, the rest of your life.

This means: even with physical access to your hardware, the keys are not sitting there to be lifted. They are sealed. The letter doesn’t open because the envelope isn’t designed to open.

The closed envelope: no telemetry

Rainline does not collect usage analytics. It does not sample your conversations. It does not phone home with crash reports, query patterns, or engagement metrics for anyone’s growth team. We don’t know what you’re asking your models. We prefer to keep it that way.

This is not a setting you have to remember to flip. This is the default. The only data that leaves your machine is the data you deliberately sent — to the model you chose, through the channel you chose. Everything else stays in the drawer.

The local hands: tools run where you are

When you call a tool through your collaborator — search the web, query a database, generate an image, run a script — the tool runs on your hardware. The result comes back to you. The middle is your machine.

Your data does not transit our servers. It does not pass through a queue we operate so we can make sure everything works. The work happens where you are, because that is where the work belongs.

What this is actually about

Privacy, in the end, is not a checklist. It is a stance about who owns the relationship between you and the tool you spend your days with.

A collaborator that watches you and reports to someone else isn’t a collaborator. It is a colleague with two bosses, one of whom you’ve never met. The moment your work is being summarized for a vendor, the work is no longer entirely yours. The letter is being read before you have even sealed it.

We built Rainline so that wouldn’t happen. The envelope is in your hand. The seal is in your hand. The drawer is in your house.

The letter doesn’t open.