Claude in Slack: option to post without the "Sent using @Claude" attribution stamp

What

When Claude (Claude Code in Slack) posts a message on my behalf, Slack renders the message under my name and avatar but appends a "Sent using @Claude" attribution line beneath it.

Why this is a problem

For routine posts that appear under a person's own identity (PR notifications, standups, status updates), some users and workspaces don't want the app attribution surfaced. There is currently no way to remove it:

• It is not part of the message text, so it can't be stripped by changing what Claude writes.
• There is no chat.postMessage parameter exposed to suppress it (the legacy as_user lever is classic-app only and doesn't remove the stamp).
• There is no workspace admin setting to hide "Sent using" attributions.

The stamp is added by Slack at render time because the integration posts via the app using a user token.

Request

Provide an option to post without the "Sent using @Claude" attribution where Slack's platform policy allows it — for example a per-user/per-workspace setting in the Claude in Slack integration, or guidance if a different posting mode (e.g. a true user-identity send) avoids the stamp.

Environment

• Feature: Claude Code in Slack (https://code.claude.com/docs/en/slack)
• Surface: messages posted by Claude on a user's behalf into channels