GitHub Copilot in Visual Studio September update: PR exploration, BYOM changes, NuGet fixes

GitHub's September roundup for Copilot in Visual Studio 2026 lists three changes. It applies to all Copilot plans, including Free, Student, Pro, Pro+, Max, Business and Enterprise.

• Pull requests in chat: the Git agent can explore a pull request. Select it in Copilot Chat and attach a pull request from the Git Repository window to get a summary with links to the underlying comments and files. It needs your Git provider's MCP servers connected; GitHub and Azure DevOps are supported.
• Bring Your Own Model (BYOM), in preview: lets you use models through GitHub Copilot or your own deployments, whether or not you are signed in to GitHub. It is on by default in the Community, Professional and Enterprise editions. GitHub flags a breaking change: BYOM now requires the new Agent (Preview), built on the GitHub Copilot SDK-powered harness. The earlier Ask and Agent modes no longer support BYOM.
• NuGet vulnerability fixes: NuGet Audit warnings in the Error List now have a fixer action that opens Copilot Chat in agent mode and asks Copilot to fix the vulnerable packages through the NuGet MCP server. It requires signing in to Copilot and enabling the NuGet MCP server in the Chat tools menu.