環境 OS: Windows 11 Java: OpenJDK 17.0.7 Scala : 3.3.0 Scala.js : 1.13.0 ScalaHTML: 0.1.1 ScalaCSS : 0.8.0-RC1 Akka: 2.7.0 Akka-HTTP: 10.5.2 諸々の設定は下記のようです。 val scala3Version = "3.3.0" val AkkaVersion = "2.7.0" val AkkaHttpVersion = "10.5.2" ThisBuild / organization := "$organization$" ThisBuild / scalaVersion := scala3Version ThisBuild / version := "0.1.0-SNAPSHOT" lazy val root = (project in file("