<!--- Please read this! Before opening a new issue, make sure to search for keywords in the issues filtered by the "regression" or "bug" label: - https://gitlab.com/gitlab-org/gitlab/issues?label_name%5B%5D=regression - https://gitlab.com/gitlab-org/gitlab/issues?label_name%5B%5D=bug and verify the issue you're about to submit isn't a duplicate. ---> ### Summary When you are assigned as a reviewer in a merge request, the `X-GitLab-NotificationReason` header in the notification email for the assignment event is set to `review_requested`, making it possible to filter for these notifications. This header is not set for Merge Request creation notifications when the reviewer list is configured on creation. In contrast, when a Merge Request is created with a preconfigured assignee, the notification email correctly contains the header `X-GitLab-NotificationReason: assigned`. ### Steps to reproduce 1. Create a merge request with another account as a merge request reviewer 2. Observe that the notification email the other account gets does not contain `X-GitLab-NotificationReason: review_requested` 3. Remove the other account from the reviewer list 4. Add the other account to the reviewer list 5. Observe that the notification email the other account gets now does contain `X-GitLab-NotificationReason: review_requested` Note: It seems impossible to reproduce this with a single account because then gitlab either sends no emails at all or overrides `X-GitLab-NotificationReason` with `own_activity`, depending on your notification settings. ### What is the current *bug* behavior? New merge requests with a preconfigured list of reviewers trigger notification emails without `X-GitLab-NotificationReason` set to `review_requested`. ### What is the expected *correct* behavior? New merge requests with a preconfigured list of reviewers should set the `X-GitLab-NotificationReason` correctly to `review_requested`, similar to how it works with merge request assignees ### Possible fixes [This line in app/services/notification_recipients/builder/default.rb](https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/services/notification_recipients/builder/default.rb#L53) is the only difference I can find between the behaviour of notifications regarding assignees and reviewers, so this might be the problem.