On April 9, 2026, between 16:05 UTC and 20:36 UTC, the Copilot cloud agent service was degraded, causing new agent sessions to be delayed or fail to start. Users who attempted to start Copilot cloud agent sessions during this period experienced jobs getting stuck in the queue, with wait times peaking at 54 minutes compared to the normal 15–40 seconds. On average, approximately 84% of requests to start agent sessions failed, peaking at 97.5% during the worst period.
This was due to an internal service exceeding API rate limits, compounded by a caching bug that persisted the rate-limited state beyond the actual rate limit window, causing recurring outage waves rather than a single recovery.
We mitigated the incident by deploying a configuration change to bypass the affected cache and shifting API traffic to an alternative authentication path that reduced rate limit exposure. We have since added automated monitoring and alerting for this failure mode, deployed per-endpoint rate limit controls, and added caching for high-traffic API calls to reduce overall load. We are also working on longer-term improvements to rate limit isolation and traffic management to prevent similar issues in the future.
