Since Aug 22nd we can't save any Side Panel tabs

Hello!

Yesterday (Aug 22nd 2025) we got an update in our Teams Links that we normally share to start meetings. They were modified from this format:

https://teams.microsoft.com/l/meetup-join/19%3ameeting_XXXXXXXXXXXXXXX%40thread.v2/0?context=%7b%22Tid%22%3a%22xxxxxxxxxxxx%22%2c%22Oid%22%3a%22xxxxxxxxxxxxxx%22%7d

to 

https://teams.microsoft.com/meet/00000000000?p=XXXXXXXXX

Sensitive values and ids have been redacted above and inside all the snippets in this post.

This looks like a planned rollout, as specified here: https://mc.merill.net/message/MC772556 

After this change, none of our apps are able to save a side panel into any of the meetings with the new link format.

We had a couple of older, still available meetings whose link had the previous format, and we are able to save the side panel there, but no matter what we tried, nothing allowed us to solve this situation on our end. My final resort is this post in hopes of a solution to what we see.

Each save operation yields a 500 on this call

https://teams.microsoft.com/api/chatsvc/amer/v1/threads/19%3Ameeting_XXXXXXXXXXXXXXXXXX%40thread.v2/properties?name=tab%3A%3Axxxxxxxxxxxxxxxx

{
    "errorCode": 500,
    "message": "{\"subCode\":\"TabOperationFailed\",\"details\":\"Initiator 8:orgid:xxxxxxxxxxxxxx failed perform tab operation\",\"errorCode\":1500,\"errorSubCode\":null}",
    "standardizedError": {
        "errorCode": 1500,
        "errorSubCode": 1,
        "errorDescription": "TabOperationFailed-Initiator 8:orgid:xxxxxxxxxxxxxx failed perform tab operation"
    }
}

I ended up trying to manually install it with graph api calls, which didn't work either and gave me a 502

curl -s -X POST "https://graph.microsoft.com/v1.0/chats/$CHAT_ID/tabs" \
  -H "Authorization: Bearer $ACCESS_TOKEN" -H "Content-Type: application/json" \
  -d '{
    "displayName": "DisplayName",
    "email address removed for privacy reasons": "https://graph.microsoft.com/v1.0/appCatalogs/teamsApps/'"$TEAMS_APP_ID"'",
    "configuration": {
      "entityId": "entity-random",
      "contentUrl": "https://<domain>/?theme={theme}&locale={locale}",
      "websiteUrl": "https://<domain>/"
    }
  }' | jq .

{
  "error": {
    "code": "BadGateway",
    "message": "Failed to execute backend request.",
    "innerError": {
      "date": "2025-08-22T03:36:08",
      "request-id": "b4bbade7-1ea2-46df-a1d9-92cdda9e360b",
      "client-request-id": "b4bbade7-1ea2-46df-a1d9-92cdda9e360b"
    }
  }
}

Then, thinking there was something wrong with my app, I used a MS app, same result

curl -s -X POST "https://graph.microsoft.com/v1.0/chats/$CHAT_ID/tabs" \
  -H "Authorization: Bearer $ACCESS_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "displayName": "Website - test",
    "email address removed for privacy reasons": "https://graph.microsoft.com/v1.0/appCatalogs/teamsApps/com.microsoft.teamspace.tab.web",
    "configuration": {
      "entityId": null,
      "contentUrl": "https://www.microsoft.com",
      "websiteUrl": "https://www.microsoft.com"
    }
  }' | jq .
{
  "error": {
    "code": "BadGateway",
    "message": "Failed to execute backend request.",
    "innerError": {
      "date": "2025-08-22T04:02:36",
      "request-id": "ece5590e-f23f-4780-a4a6-20c1b2f0d0f3",
      "client-request-id": "ece5590e-f23f-4780-a4a6-20c1b2f0d0f3"
    }
  }
}

I then tested it against chats that do not belong to a meeting. Both apps succeeded

curl -s -X POST "https://graph.microsoft.com/v1.0/chats/$REGULAR_CHAT_ID/tabs" \
  -H "Authorization: Bearer $ACCESS_TOKEN" -H "Content-Type: application/json" \
  -d '{
    "displayName": "Website - test",
    "email address removed for privacy reasons": "https://graph.microsoft.com/v1.0/appCatalogs/teamsApps/com.microsoft.teamspace.tab.web",
    "configuration": { "entityId": null, "contentUrl": "https://www.microsoft.com", "websiteUrl": "https://www.microsoft.com" }
  }' | jq .
{
  "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#chats('19%3xxxxxx_xxxxxxxxxxxx%40unq.gbl.spaces')/tabs/$entity",
  "id": "a0cca657-12d0-4df0-84d8-cc1f8fa7d3e6",
  "displayName": "Website - test",
  "webUrl": "https://teams.microsoft.com/l/chat/19%xxxxxxxxx_XXXXXXXXX%40unq.gbl.spaces/tab%3a%3xxxxxxxxxxxxxxxxxxxxxx?webUrl=https%3a%2f%2fwww.microsoft.com&label=Website+-+test&tenantId=xxxxxxxxxxxxxxxxxxx,
  "configuration": {
    "entityId": null,
    "contentUrl": "https://www.microsoft.com",
    "removeUrl": null,
    "websiteUrl": "https://www.microsoft.com"
  }
}

curl -s -X POST "https://graph.microsoft.com/v1.0/chats/$REGULAR_CHAT_ID/tabs" \
  -H "Authorization: Bearer $ACCESS_TOKEN" -H "Content-Type: application/json" \
  -d '{
    "displayName": "redacted",
    "email address removed for privacy reasons": "https://graph.microsoft.com/v1.0/appCatalogs/teamsApps/'"$TEAMS_APP_ID"'",
    "configuration": {
      "entityId": "redacted",
      "contentUrl": "https://<domain>/?theme={theme}&locale={locale}",
      "websiteUrl": "https://<domain>/"
    }
  }' | jq .
{
  "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#chats('19%3xxxxxxxxxxxxx_xxxxxxxxxxxxx%40unq.gbl.spaces')/tabs/$entity",
  "id": "xxxxxxxxxxxxxxxxxxxxxx",
  "displayName": "redacted",
  "webUrl": "https://teams.microsoft.com/l/entity/<redacted>/_djb2_msteams_prefix_000000000?webUrl=https%3a%2f%2f<domain>%2f&label=redacted+label&context=%7b%0d%0a++%22context%22%3a+%22chat%22%2c%0d%0a++%22chatId%22%3a+%2219%3axxxxxxx_xxxxxxxxx%40unq.gbl.spaces%22%2c%0d%0a++%22subEntityId%22%3a+null%0d%0a%7d&tenantId=xxxxxxxxxxxxxxxx",
  "configuration": {
    "entityId": "redacted",
    "contentUrl": "https://<domain>/?theme={theme}&locale={locale}",
    "removeUrl": null,
    "websiteUrl": "https://<domain>/"
  }
}

At this point we don't know what else to do, seems like a meeting specific issue that we are unable to solve. It's affecting our tenants in all environments, since our primary business flow relies on this panel. All the snippets contain real dates and request-ids, here's hoping it helps somehow.

Help, and thanks in advance.

~A. del Yerro