Versions

• Java 21.0.3
• Scala 3.3.7
• sbt: 1.11.7

Steps
Create hello world project and use pipelining.

package first

@main
def main(): Unit = println("Hello World")

in build.sbt

scalaVersion := "3.3.7"
ThisBuild / usePipelining := true

and compile within sbt, result:

[warn] bad option '-Ypickle-java' was ignored
[warn] bad option '-Ypickle-write' was ignored
[warn] two warnings found

Expectations
No warnings or a warning that pipelining is not supported.

Problems
Pipelining was introduced in Scala 3.5 and afaik not back ported to Scala 3.3.x LTS. So it is not supported in this version, but the options '-Ypickle-java' and '-Ypickle-write' are still applied.

Discussion
The current warnings cause confusion, although it might not qualify as a bug. See the discussion on the Scala Users Forum for the background.