Thanks Ben, this context helps, and I confirmed IgnorePattern.txt is not used for UE5, sorry about this confusion. We need to better surface this as even I wondered whether it was still being used for logs we don’t control.
I am going to be OOO this next week, though I will dive into this when return, agree that we need a simpler way to suppress these than needing to generate a custom event matcher.
In the meantime, if you look in Engine\Source\Programs\UnrealBuildTool\Matchers\CompileEventMatcher.cs, can see an example of the matcher used for compile events, which are multiline, and may help with some ideas, since you have started down that path with some success.