## The problem
Sending to Slack via `@trycourier/courier` 6.0.6 with `courier.send({ message: { to: { slack: { access_token, channel } }, data: { message } } })` fails TypeScript compilation: `error TS2353: Object literal may only specify known properties, and 'slack' does not exist in type 'MessageRecipient'`, even though the Courier docs show exactly this shape. Reinstalling, upgrading to 6.0.6, and resetting lockfiles did not change anything. The docs example and the shipped typings disagreed.
## The fix
The `Recipient` type was missing the `slack` property (it existed in `UserProfile` but was not carried over to `MessageRecipient`), so the documented send shape failed type checks. The maintainer confirmed the miss and shipped the corrected typings in `@trycourier/courier@6.0.7`. Upgrade to 6.0.7 or later.