People search API returning "Unknown error"

[mbice]

Target SharePoint environment

SharePoint Online

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

SharePoint REST API

Developer environment

Windows

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

Describe the bug / error

We noticed the other day that the people search REST API has started to throw errors. Initially reproduced it on our internal test tenant, but now seeing it on several production tenants. Seems like it is broken everywhere, now. Whenever we use the /_api/search/query endpoint using the people result source ID, it returns "Unknown error".

We are also seeing that the issue doesn't reproduce for all users. Seems to be more consistently reproduced with admin/owners.

Steps to reproduce

Navigate to the following URL (if it doesn't reproduce try as an administrator or owner):

https://[tenant].sharepoint.com/_api/search/query?querytext='MOD'&sourceid='b09a7990-05ea-4af9-81ef-edfab16c4e31'

And you'll get 500 error response with message "An unknown error occurred".

NOTE: We are seeing the same error in some other search queries that are not people specific, but can't identify a clear pattern, yet. Still investigating, but seems that this also affects querying against local sharepoint results source as well, but only in some scenarios.

Expected behavior

Expect to see people search results returned as they have been up until a couple of days ago.

[Ashlesha-MSFT]

Hi @mbice,
Thank you for bringing this issue to our attention. We will look into it and get back to you shortly.

[Ashlesha-MSFT]

@mbice,
Thanks for the report. We validated the same People search API call in our test tenant and it is returning successful results, so we could not reproduce globally yet. To investigate your tenant-specific failure, please share failing request URL, UTC timestamp, correlation ID, impacted user role, and HAR trace. Once we receive these, we will raise a bug immediately with backend traces

[mbice]

Hi @Ashlesha-MSFT,

URL: https://[tenant].sharepoint.com/_api/search/query?querytext='MOD'&sourceid='b09a7990-05ea-4af9-81ef-edfab16c4e31'
Timestamp: 2026-06-24T16:11:48.630Z
Correlation ID: 3cc920a2-500c-6000-1e46-34d8b1518e59
Error message: "An unknown error occurred."
User roles impacted: I have reproduced with global admin, owner, and visitor users

Is that enough to isolate it on your side? If you need tenant details, is there another way I can send those over without posting here publicly? I've reproduced this on about 5 tenants so far (both internal and various client are reporting it, too).

Thanks!

[Ashlesha-MSFT]

Thank you, this is very helpful and enough for initial trace correlation.
For tenant-specific details, please don’t post publicly on GitHub. Please share them privately v-ashlpawar@microsoft.com
Please include: affected tenant URLs, one failing user UPN per tenant, UTC timestamps, correlation IDs, and (if available) HAR files.

[mbice]

@Ashlesha-MSFT ok I've sent those details via email. Thanks!

[mbice]

@Ashlesha-MSFT the issue now seems to be resolved on all affected tenants we had it logged against. Closing this issue. Thanks!