When you cancel command-line MSBuild, we send the cancellation signal through the API and also writes status to stdout. But it does so directly: https://github.com/dotnet/msbuild/blob/39e20dce0c00a572f1fbd20a0a520d4e941bbc33/src/MSBuild/XMake.cs#L1007 And terminallogger tends to immediately overwrite that message with status updates, so it's not obvious whether cancellation is in progress.
When you cancel command-line MSBuild, we send the cancellation signal through the API and also writes status to stdout. But it does so directly:
msbuild/src/MSBuild/XMake.cs
Line 1007 in 39e20dc
And terminallogger tends to immediately overwrite that message with status updates, so it's not obvious whether cancellation is in progress.