Privacy and data

The short version

• Your chats are stored encrypted on this computer. There are no Corner servers.
• To find and follow your deals, message text goes to Anthropic's API under your own key. Nothing else leaves, and without a key nothing leaves at all.
• Corner never sends a message unless you press Send.
• You can exclude a chat, forget it, or delete everything, any time.

What Corner reads

Your Telegram chats, signed in as a linked device. The first sync reads up to 300 chats active in the last 90 days. It skips bots, channels, your Saved Messages and groups of more than 25 people. After that it keeps up with new messages as they arrive.

It reads message text, because that's how it tells which chats are deals and whether you owe someone an answer. Photos, voice notes and files show up as placeholders like [photo] or [file: proposal.pdf]; Corner doesn't download them.

Where it's stored

On this computer only, in one encrypted database (SQLCipher) with a random 256-bit key. That key, your Telegram session and your Anthropic key are each encrypted by your operating system's keystore: the Keychain on a Mac, DPAPI on Windows. If the keystore isn't available, Corner refuses to run rather than store anything unprotected.

On Windows, DPAPI protects your data from other users of the computer and from someone reading the disk. It doesn't protect against malware already running as you. Nothing on a computer does.

The data folder:

• Mac: ~/Library/Application Support/Corner
• Windows: %APPDATA%\Corner

What leaves this computer

Only message text, only to Anthropic's API, only with your API key, and only for these jobs:

Finding deals

The last 30 messages of each synced chat go to Anthropic once, to decide whether it's a deal. That's up to 300 chats from the last 90 days, groups of up to 25 people.

Following a deal

After that, only chats you track are analyzed again: their recent messages, to keep the stage, summary, open questions and promises current.

Drafts, when you ask

When you press Ctrl+J / ⌘J, the chat's last 30 messages go along, plus up to 10 of your own recent messages from your tracked deals (300 characters each), so the draft sounds like you.

Excluded and forgotten chats are never sent, and neither are Telegram's ids for your chats and messages. Anthropic's commercial terms don't allow training on your data, and it keeps API data only as its data-retention policy for commercial customers allows.

Nothing else leaves: no analytics, no usage tracking, and crash reports stay on your computer. Corner talks to Telegram (as your linked device) and to Anthropic, and to nothing else.

Coming An opt-in, off by default, to share a daily count of what Corner did (nudges shown, follow-ups done) to help us improve it. Never chat content, names or numbers, and you'll be able to preview the exact report before anything is sent.

What never happens

• Corner never sends a message for you. A message goes out when you press Send, and an AI draft only fills the box.
• Nobody at Corner sees your chats. There's no Corner server to see them on.
• Corner never changes anything in your Telegram: no read marks, no deletes.

Exclude a chat

Settings > Privacy > Excluded chats lists every synced chat. Switch on Excluded and Corner ignores it: nothing from it is analyzed, and its deal stops producing nudges. Switch it off to bring it back.

Forget a chat

The bin icon next to a chat in the same list forgets it: Corner permanently deletes its messages, the deal and the nudges built from it, and excludes the chat so it isn't synced again. You can re-include it under Excluded chats later. Your chat in Telegram is not touched.

Delete all data

Settings > Privacy > Delete all data, then type DELETE to confirm. It permanently deletes every chat, message, deal, nudge and setting Corner stored, removes your Anthropic key and signs out of Telegram. There's no undo.

Deletes are real deletes: SQLite's secure delete overwrites the removed data, and the write-ahead log is flushed so no copy is left behind there. Coming After every forget or delete, the database is re-encrypted under a fresh key and the old key destroyed, so even an old backup of the file can't be read.

Uninstalling Corner doesn't delete your data. Use Delete all data first, or remove the data folder above.

Your keys

• Anthropic key. Settings > AI > Replace swaps it for a new one; Remove deletes it from this computer. To rotate it, create a new key in the Anthropic Console, paste it with Replace, then revoke the old one in the Console. The full key never leaves Corner's background process; the window only ever shows a masked version.
• Database key. Made at random when you install, kept in your keystore, never shown and never sent anywhere. Corner won't silently make a new one if the old one can't be read. See the Keychain prompt.
• Telegram session. Encrypted the same way. Disconnecting signs it out. You can also end it from your phone under Telegram's Settings > Devices.

Logs

Corner keeps a log on your computer for when something breaks. Logs never contain message text, keys, sessions or phone numbers, and files older than 7 days are deleted. They're never uploaded: you decide whether to send one. See sending logs.

The demo

The demo runs on made-up data in its own profile with a key that only lives in memory. It never touches your accounts and is wiped when you exit it.