Microsoft released its Copilot harness for building multi-model agents. It powers Copilot Code, Copilot Studio, GitHub Copilot, CLI, and VS Code. The harness is now available via Microsoft Foundry. It supports 20+ frontier models and custom keys. The runtime was ported to Rust for better performance. It reduces session overhead and time-to-first-token. Agents built in Foundry run on the same harness Microsoft uses. The SDK is available for download. The harness is open and interoperable with other frameworks. Microsoft runs the agent loop, sandbox, governance, and optimization.
What changed
Developers built and maintained their own multi-model harnesses.
What it unlocks
Building agents that reason, use tools, and complete long-running tasks without switching harnesses.
- 20+ frontier models supported
- millions of users at scale
What you need to act on it
- access to Microsoft Foundry
- use of the provided SDK or cloud runtime
Sources