User impact: Some users may have seen an error when sending messages from BizChat and the BizChat side pane in Microsoft 365 apps.

More info: More info: Affected Microsoft 365 apps included:
Outlook on the web
Outlook desktop
Microsoft Teams
Affected users may have seen an error stating “something went wrong.”

This issue affected users that had selected the Opus 4.8 model.

Final status: We’ve determined that a recent update intended to enable an updated AI model used to process chat requests and generate responses, Opus 4.8, caused an unexpected influx of service requests that led to the impact. We’ve reverted the offending update and confirmed from service telemetry that this issue is resolved.

Scope of impact: Some users located in the Asia Pacific or South America regions sending messages from BizChat and the BizChat side pane from an affected M365 app may have been impacted.

Start time: Thursday, July 23, 2026, at 1:23 AM UTC

End time: Thursday, July 23, 2026, at 4:38 AM UTC

Root cause: A recent update intended to enable an updated AI model used to process chat requests and generate responses, Opus 4.8, caused an unexpected influx of service requests that led to the impact.

Next steps: We’re reviewing our validation and updating procedures to better detect and prevent issues like this prior to deployment in the future.

This is the final update for the event.