Sudden change in clientPeoplePickerSearchUser results

[JLRishe]

What type of issue is this?

Question

What SharePoint development model, framework, SDK or API is this about?

SharePoint CSOM

Target SharePoint environment

SharePoint Online

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

No response

Issue description

I have an in-house developed People Picker that uses the clientPeoplePickerSearchUser() API to query users.

For several years, I have had a test process that runs daily to test this People Picker by searching for certain search terms and verifying the results.

About 5 days ago, those tests started failing. Upon further inspection, I found that the API is returning an empty result set when I search for certain users by first name. To the best of my knowledge, none of these users have had any recent change to their profile data, they have a First Name value and a Display Name (which includes the first name) in their profile data, and I am able to search for them by last name or username.

I am also able to find other users by first name.

I have also observed that I get the expected results if I change the search to use UseSubstrateSearch: true and use the same search terms that are currently returning empty results without that option.

What could be the cause of this sudden change in behavior? What can I do to troubleshoot it?