Deleting a large Pulumi stack failed with post-step event returned an error: failed to save snapshot: [403] The provided update token has expired. The deletion left the stack with pending_operations that then had to be cleaned up manually. It happened on CI runners and locally, and reporters with big stacks hit it repeatedly. Maintainers traced it to the client machine being under heavy network load from Pulumi itself making many large network calls during the update.