dotnet CLI/SDK and .NET runtime: Enable major roll-forward after a failed SDK upgrade?

When a .NET SDK upgrade fails, the CLI may still resolve to a newer SDK version if one is present, while applications continue to run on the existing runtime due to side‑by‑side installation. The roll‑forward policy allows an app targeting a specific runtime version to start on a newer patch or minor version, but major roll‑forward requires explicit opt‑in and can alter behavior after a failed upgrade. Administrators must decide whether to enable major roll‑forward globally to maintain availability, weighing the risk of unintended behavioral changes against downtime.

Verification can be performed by checking the CLI's list of runtimes and SDKs and by running a framework‑dependent test app with a pinned runtimeconfig to confirm which version is used after the failure.

• Should major roll‑forward be enabled by default after a failed SDK upgrade?
• What compatibility testing is required to ensure that a newer major runtime does not break existing apps?
• How can administrators verify that the CLI continues to use the intended SDK when roll‑forward is active?