Does the 👀 reaction or manual assignment remove existing assignees?
Only the primary assignee is replaced. When someone reacts with 👀 on a Slack message, or is assigned from the thread header, they become the primary assignee and the previous primary is removed. Co-assignees are not affected and stay on the thread.
What happens in each case
- Thread has a primary assignee and no co-assignees: the previous primary is removed and only the new person remains.
- Thread has a primary and co-assignees: the primary is replaced. Co-assignees stay unchanged.
- Thread has no assignee: the new person becomes primary. No one is removed.
Why 👀 replaces the primary
The 👀 reaction is an "I'll take this" signal. It makes the reacting user the lead responsible for the thread, the same as clicking Assign to me in the thread header. It is meant to make ownership clear, not to build a list of watchers.
Add someone without replacing the primary
To bring a second person into a thread without removing the current primary, use Add co-assignee in the thread assignee panel instead of the 👀 reaction. Co-assignees get notifications and appear on the thread, and the primary stays the same.
The Investigating status
The 👀 reaction does two things at once: it sets the thread status to Investigating, also shown as In Progress, and assigns the reacting user as primary. The status change has no effect on assignees. It is the assignment that replaces the primary.