related to issue C4-PlantUML Issue #385
@startuml
!include https://raw.githubusercontent.com/plantuml-stdlib/C4-PlantUML/master/C4_Container.puml
AddBoundaryTag("v1", $bgColor="lightgreen", $fontColor="green", $borderColor="green")
System_Boundary(c1, "Internet Banking", $tags="v1") {
}
@enduml
with v.1.2025.0 (or the online server) following rectangle is not green anymore (with v 1.2024.7 it was green)

based on my analysis (Windows) I assume the problem are the "wrong line breaks" in the preproc file, which are generated by the new v1.2025.0 (it produces a "special character" instead of a line break) and the it cannot correct converted anymore:
1a) create a "2024.7" preproc file with plantuml-mit-1.2024.7.jar
1b) create a "2025.0" preproc file with plantuml-mit-1.2025.0.jar
--> different line breaks for the generated skinparam statements
2) compiled both preproc files with plantuml-mit-1.2025.0.jar and only the old version is working