Microsoft makes its multi-model Copilot harness available through Foundry

Microsoft has made its GitHub-built Copilot harness available through Microsoft Foundry as a managed cloud service in public preview, alongside a downloadable software development kit. Outside developers can now use the orchestration layer that Microsoft says it is standardizing across its own Copilot products.

With the managed option, Microsoft runs the agent loop and sandbox through Foundry Agent Service. Customers supply the agent’s instructions or procedures, skills, tools, knowledge and a supported model. Microsoft takes responsibility for the runtime and execution environment; customers configure the agent’s behavior and connections.

An agent harness is the software layer around a language model. It prepares instructions and context, manages the sequence of model responses and tool calls, applies permission and approval rules, tracks session state and connects the work to an execution environment. Microsoft says the shared harness, originally built at GitHub, now underpins products including Copilot Code, Copilot Studio, the GitHub Copilot app, Copilot CLI and Visual Studio Code. Microsoft describes the shared runtime as a way to make core behavior more consistent across Copilot surfaces.

The Foundry public preview combines reusable skills; Foundry and Model Context Protocol tools with configured authentication and approvals; file and code execution; bounded subagent delegation; and source-controlled agent definitions. Developers select the Microsoft Copilot harness when creating a new agent. Existing Foundry agents are unchanged, and Microsoft says users cannot yet switch an existing agent to a different harness.

Microsoft says developers can choose from more than 20 supported frontier models, or use their own model API key, without rewriting the surrounding orchestration. The opened product materials do not list every model or independently validate that count. The Microsoft Copilot SDK repository is available under the MIT license, with packages for TypeScript, Python, Go, .NET, Java and Rust. The repository describes the SDK as the programmable interface to the same harness used across Microsoft and GitHub products.

GitHub says it has also made the harness the default for new sessions in the VS Code editor and Agents window. The change shows how Microsoft is moving separate Copilot interfaces onto a shared execution layer while opening that layer to Foundry customers.

Microsoft says consumption-based billing for the Foundry harness runtime begins December 1, 2026. The runtime is free until then, although model inference, tools and connected services can still generate charges. Microsoft lists starting sandbox rates of $0.0994 per vCPU-hour and $0.0118 per GiB-hour, with prices varying by region and customer agreement.