Power Platform Community Forum Thread Details

Description
We have a production Power Automate cloud flow that posts a message to a Microsoft Teams channel and mentions a Teams tag (AAA). This flow has been working normally for a long time without any changes. However, starting on 11 Jun 2026 01:53:22 GMT, the same flow began failing consistently.

Steps to reproduce
1.Use Microsoft Teams connector action: Get an @mention token for a tag for tag AAA in Team [Team name].
2.Use action: Post message in a chat or channel to Channel [Channel name].
3.In message body, insert:
@{outputs('Get_an_@mention_token_for_a_tag')?['body/atMention']} + other HTML text.
4.Run the flow.

Expected result
A message is posted successfully and the Teams tag is mentioned.

Actual result
The flow fails with BadRequest:
“Neither Body nor adaptive card content contains marker for mention with Id '0'. Add '<at id="0">AAA</at>' to the body or an adaptive card.”

Evidence from run history
Output of “Get an @mention token for a tag” (failed run) returns:
{"atMention":"<atTag><tagId>[...]</tagId><groupId>[...]</groupId></atTag>"}
This token does not contain the <at id="0">...</at> marker required by the posting action error message.

Question

Can you confirm whether there is an intermittent service-side issue/regression affecting tag mentions posted via Power Automate Teams connector / TeamsGraph, causing this validation error?
Is there any known advisory/incident around Jun 11, 2026 for TeamsGraph / Teams connector mentions?