GitHub Copilot Now Supports Custom Agents With Versioned Instructions and Tool Control

GitHub Copilot allows developers to build custom agents — named personas with defined instructions, tools, and domain knowledge — stored as Markdown files within a repository's version control. Unlike one-off prompts, these agents encode repeatable workflows that any team member can select directly from the Copilot Chat dropdown. Agents are configured using YAML frontmatter and can be paired with modular 'skills' files that load focused knowledge only when needed, keeping the core agent lean and reviewable. The system distinguishes between four primitives — agents, skills, instructions, and prompts — each serving a different purpose in the Copilot customization hierarchy. A LoadRunner-based example is used to illustrate how the design applies broadly to use cases such as test automation, incident response, and code review.