Azure DevOps @mentions fail when the mention User ID starts with an alphabetic character

Question

We are experiencing a new issue with Azure DevOps work item Discussion @mentions and the notification emails generated from those comments.

When a user is @mentioned in a work item Discussion, the mention is correctly saved and displayed in the work item. However, for certain users, the mention is not included correctly in the notification email.

We have identified a very specific pattern:

Users whose underlying Azure DevOps mention User ID begins with a numeric character appear to work correctly.

We currently have 5 users whose mention User IDs begin with an alphabetic hexadecimal character (A–F), and all 5 are experiencing the issue.

The affected users previously received these @mention emails successfully.

The affected users have valid Azure DevOps access and their email addresses are correct.

The issue occurs on new work items, so it is not isolated to a particular work item or discussion history.

The issue is not dependent on who creates the comment.

For a failing user, the underlying mention appears as:

@<c1111111-cccc-1111-1111-11111ccccc11>

In the generated email, the < and > characters are not HTML-encoded, and the user's name/identity is not resolved in the email. Instead, the email effectively contains:

@<c1111111-cccc-1111-1111-11111ccccc11>

For a working user, the generated email contains the encoded form:

@<00000002-1111-1111-9999-DDDDDDDDDD11>

The working and failing users therefore appear to be processed differently during notification generation.

The most significant pattern we have found is that all five affected users have mention User IDs beginning with A–F, while the users we have tested successfully have IDs beginning with numeric characters.

We would like to determine whether there is a known issue or recent change in Azure DevOps related to @mention identity resolution, GUID parsing, HTML encoding, or notification email rendering.

This behavior appears to be occurring in the Azure DevOps notification/mention processing pipeline rather than with the users' email accounts.

Can Microsoft confirm whether this is a known issue, recent regression, or change in the way Azure DevOps processes @mention User IDs? If not, what diagnostic logs or additional information would be most useful for troubleshooting this?

Answer 1

We experience the exact same thing !

Answer 2

We have the same problem in DevOps. Is this fixed yet?