What happened
Microsoft’s Visual Studio Blog announced on November 10, 2026, that Copilot Chat in Visual Studio 2026 version 18.12 now runs on the Microsoft Copilot SDK, developed by GitHub. The new experience is on by default. Microsoft describes the SDK as the same technology powering GitHub Copilot CLI, the GitHub Copilot app and VS Code. The company says the change keeps the models the same but changes the harness around them: the tools available to the model, the context it receives, its memory and the actions it is allowed to take.
The .NET team built a benchmark from issues in real C# projects spanning .NET Framework and .NET Core, Azure and Aspire, WinForms and desktop apps. It ran both Copilot Chat experiences on 157 tasks. A task counted as resolved only if the tests that had been failing passed and no tests that had already passed were broken. Microsoft says the new experience came out ahead with every model tested, across capability levels and providers, resolving up to 21 more tasks. The blog also says the engine was tested on C++, Python and other languages, but gives no corresponding task count or results for those languages.
The new chat lets a developer send another instruction while Copilot is working; that instruction remains marked Pending until picked up and can be withdrawn. Each step displays what came back, with options to expand results, open them in the editor or copy the exact command. When Copilot delegates work to a subagent, a separate card shows its model and steps live. Developers can direct chat to any folder on their machine or attach entire folders as context. With Agent selected, slash commands include /security-review for a security-focused review and /rubber-duck, which asks a different model to critique Copilot’s plan before it acts. Specialized Visual Studio agents and existing MCP servers remain part of the experience.
The transition is not complete. Microsoft says plan mode and chat exports have not yet been brought over from the previous experience. Users who rely on those features, or want to switch back for any reason, can turn off “Use new Copilot chat experience” under Tools > Options > GitHub > Copilot > Copilot Chat and restart Visual Studio. The company asks users to report issues through Help > Send Feedback > Report a Problem or its Developer Community.
What the archive adds
New Runtime’s earlier coverage on the GitHub Copilot SDK’s transition to Microsoft Copilot SDK noted Microsoft’s move toward a shared agent foundation and a phased migration. The Visual Studio change is a new event in that transition: the SDK is now the default Copilot Chat engine in a specific IDE release, with user-visible capabilities and a vendor-reported task comparison.
Trend signal
This supports harness architecture outlives model choice: Microsoft says it held models constant while changing the harness, and reports better task resolution alongside changes to tools, context and agent interaction. The benchmark is company-reported, so it is a concrete example of the thesis rather than independent confirmation of the magnitude of the improvement.
Why now
Visual Studio 2026 version 18.12 is the point at which Microsoft has made the SDK-powered chat the default rather than merely describing a planned migration. The release also shows the shared Copilot foundation appearing in a concrete developer workflow, while Microsoft acknowledges that some features are still being ported.
Why it matters
For teams using Visual Studio, this is not just a model change: Microsoft says the same models can resolve more benchmark tasks when surrounded by a different harness. Visible command results and subagent activity may also make it easier to inspect what an agent actually did, while mid-task steering gives developers a way to correct direction without waiting for a run to finish. Folder-level context can broaden work beyond the open solution, which is useful for repositories or tasks spanning multiple directories.
The practical trade-off is migration completeness. Developers who use plan mode or chat exports may lose those workflows in the new experience for now, though Microsoft provides a switch back. Teams should test the default on representative tasks and verify both output quality and the interaction features they depend on before changing internal guidance or standardizing workflows.
Limits and uncertainty
The benchmark is Microsoft’s own evaluation, and the blog does not publish the task set, per-model results, exact comparison methodology beyond its pass/fail rule, or independent replication. “Up to 21 more tasks” is a maximum difference, not an average or a guarantee for an individual project. The source says the engine was also tested on other languages but does not provide comparable figures for them. It does not quantify the cost visibility feature, describe its billing scope, or say when plan mode and chat exports will return. The announcement does not establish how results vary by repository, task type or developer intervention.
Skill to build now
Choose a representative task from your backlog and run it in Visual Studio 2026 18.12. Inspect the step results and commands, try a mid-task correction, and check whether folder-level context or subagents help. Before adopting the new experience for a team, inventory reliance on plan mode and chat exports; use the documented switch-back path if either is a blocker.
Reader takeaway
Visual Studio’s Copilot Chat has adopted Microsoft’s shared Copilot harness by default, and Microsoft reports better results on its C# task set with the same models. Treat that as a reason to test the new workflow—not as a promise of equivalent gains on your codebase—and account for features still missing during the transition.