Copilot Coding Agent Default Environment Update Feature Request

[DavidDavids]

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Feature Request: Update Default .NET SDK in Copilot Coding Agent to .NET 9

Summary
Currently, the Copilot coding agent (Copilot Workspace, Copilot PRs, and related automation) appears to default to .NET 8 as the installed SDK environment. For projects that have already fully migrated to .NET 9, this creates significant inefficiency: every automated coding session, build, or test initiated by Copilot has to first remove .NET 8 and install .NET 9 before actual work can begin.

Impact

• Wastes time and compute resources on every Copilot session and PR.
• Introduces friction for teams/projects that have adopted .NET 9 as their baseline.
• Makes it more likely that Copilot-generated code/tests will not match the intended target framework if the agent reverts to .NET 8 defaults.
• Discourages early adoption of new .NET releases.

Request
Please update the base image/environment for the Copilot coding agent to:

• Use .NET 9 as the default installed SDK (or at least provide .NET 9 alongside .NET 8).
• Optionally, provide a way for users to pin or select a default .NET version (e.g., via a global.json or project-level config).

Motivation

• .NET 9 is now the latest stable release, and many modern projects have migrated to it.
• This change will save time, resources, and reduce friction for Copilot users working with the latest .NET ecosystem.

Thank you for considering this update!

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[DavidDavids]

Here is a great example of exactly what I am referring to... My Repo has very explicit instructions not only that this must be in .net 9, but there are workflows to guarantee this regression that we see here doesn't pass validation... what a massive waste of compute and IO happening here... at this point I had to terminate the process and provide explicit instructions in the PR so it doesn't abide by repo rules.

[DavidDavids]

I see there is a solution for this already... closed discussion.

[BlahTommy]

could you share the solution? instead of closing without reference?

[det-peralta]

Please what is the solution? thx

[oWretch]

The solution is to create a copilot-setup-steps.yml workflow to configure your environment as you need. This can include installing specific framework versions, or other build and test tooling. Make sure to use the cache (with the actions/cache action) to speed up the initialisation.

Documentation
Example