Windows 365 team shares how they scaled .NET Aspire adoption across 50+ microservice repositories in two phases. Phase 2 focused on building a reliable baseline: standardizing Azure Functions SDK configs, creating a shared AppHostFixture with readiness-gated startup, implementing proper Cosmos DB emulator health checks, and enforcing cloud test gates on every PR. Phase 3 introduced MARS (Multi-repo Agentic Rollout System), built on the GitHub Copilot SDK and Microsoft Agent Framework, which automates onboarding by running a check→plan→fix→validate→learn loop per repo. Aspire serves as the control plane, with custom resource types for agent sessions, built-in eventing as the agent bus, and Aspire.Hosting.Testing enabling 700+ E2E tests of the orchestration system itself. The agentic rollout eliminated 4–8 hours of manual setup per repo and enabled near-tripling of adoption in the final quarter.
