diff --git a/.scala-steward.conf b/.scala-steward.conf
index 0c8bf58e..b6b6f7d3 100644
--- a/.scala-steward.conf
+++ b/.scala-steward.conf
@@ -4,6 +4,6 @@ updates.ignore = [
   {groupId = "org.scala-lang", artifactId = "scala-compiler", version = "3."}
 ]
 updates.pin = [
-  {groupId = "org.scala-lang", artifactId = "scala3-library", version = "3.3."},
-  {groupId = "org.scala-lang", artifactId = "scala3-library_sjs1", version = "3.3."}
+  {groupId = "org.scala-lang", artifactId = "scala3-library", version = "3.9."},
+  {groupId = "org.scala-lang", artifactId = "scala3-library_sjs1", version = "3.9."}
 ]
diff --git a/build.sbt b/build.sbt
index 9de63718..0877ee37 100644
--- a/build.sbt
+++ b/build.sbt
@@ -2,7 +2,7 @@ import com.softwaremill.UpdateVersionInDocs
 import com.softwaremill.SbtSoftwareMillCommon.commonSmlBuildSettings
 import com.softwaremill.Publish.{updateDocs, ossPublishSettings}
 
-val scala3 = "3.3.6"
+val scala3 = "3.9.0"
 
 ThisBuild / dynverTagPrefix := "scala3-v" // a custom prefix is needed to differentiate tags between scala2 & scala3 versions
 
diff --git a/core/src/main/scala/magnolia1/impl.scala b/core/src/main/scala/magnolia1/impl.scala
index c87c641e..b25f4299 100644
--- a/core/src/main/scala/magnolia1/impl.scala
+++ b/core/src/main/scala/magnolia1/impl.scala
@@ -260,7 +260,7 @@ trait SealedTraitDerivation:
   protected inline def subtypesFromMirrorStep[A, s](
       m: Mirror.SumOf[A],
       idx: Int
-  ): List[SealedTrait.Subtype[Typeclass, A, _]] =
+  ): List[SealedTrait.Subtype[Typeclass, A, ?]] =
     summonFrom {
       case mm: Mirror.SumOf[`s`] =>
         subtypesFromMirror[A, mm.MirroredElemTypes](
@@ -300,8 +300,8 @@ trait SealedTraitDerivation:
   protected transparent inline def subtypesFromMirror[A, SubtypeTuple <: Tuple](
       m: Mirror.SumOf[A],
       idx: Int = 0, // no longer used, kept for bincompat
-      result: List[SealedTrait.Subtype[Typeclass, A, _]] = Nil
-  ): List[SealedTrait.Subtype[Typeclass, A, _]] =
+      result: List[SealedTrait.Subtype[Typeclass, A, ?]] = Nil
+  ): List[SealedTrait.Subtype[Typeclass, A, ?]] =
     inline erasedValue[SubtypeTuple] match
       case _: EmptyTuple =>
         result.distinctBy(_.typeInfo).sortBy(_.typeInfo.full)
diff --git a/core/src/main/scala/magnolia1/interface.scala b/core/src/main/scala/magnolia1/interface.scala
index 929e87af..8412010c 100644
--- a/core/src/main/scala/magnolia1/interface.scala
+++ b/core/src/main/scala/magnolia1/interface.scala
@@ -212,7 +212,7 @@ end CaseClass
   */
 case class SealedTrait[Typeclass[_], Type](
     typeInfo: TypeInfo,
-    subtypes: IArray[SealedTrait.Subtype[Typeclass, Type, _]],
+    subtypes: IArray[SealedTrait.Subtype[Typeclass, Type, ?]],
     annotations: IArray[Any],
     typeAnnotations: IArray[Any],
     isEnum: Boolean,
@@ -222,7 +222,7 @@ case class SealedTrait[Typeclass[_], Type](
   // for backward compatibility with v1.0.0
   def this(
       typeInfo: TypeInfo,
-      subtypes: IArray[SealedTrait.Subtype[Typeclass, Type, _]],
+      subtypes: IArray[SealedTrait.Subtype[Typeclass, Type, ?]],
       annotations: IArray[Any],
       typeAnnotations: IArray[Any],
       isEnum: Boolean
@@ -238,7 +238,7 @@ case class SealedTrait[Typeclass[_], Type](
   // for backward compatibility with v1.0.0
   def copy(
       typeInfo: TypeInfo,
-      subtypes: IArray[SealedTrait.Subtype[Typeclass, Type, _]],
+      subtypes: IArray[SealedTrait.Subtype[Typeclass, Type, ?]],
       annotations: IArray[Any],
       typeAnnotations: IArray[Any],
       isEnum: Boolean
@@ -269,7 +269,7 @@ case class SealedTrait[Typeclass[_], Type](
     * @return
     *   whatever the 'handle' function returned!
     */
-  def choose[Return](value: Type)(handle: Subtype[_] => Return): Return =
+  def choose[Return](value: Type)(handle: Subtype[?] => Return): Return =
     @tailrec def rec(ix: Int): Return =
       if ix < subtypes.length then
         val sub = subtypes(ix)
@@ -289,7 +289,7 @@ object SealedTrait:
   // for backward compatibility with v1.0.0
   def apply[Typeclass[_], Type](
       typeInfo: TypeInfo,
-      subtypes: IArray[SealedTrait.Subtype[Typeclass, Type, _]],
+      subtypes: IArray[SealedTrait.Subtype[Typeclass, Type, ?]],
       annotations: IArray[Any],
       typeAnnotations: IArray[Any],
       isEnum: Boolean
@@ -389,7 +389,7 @@ end CallByNeed
 
 // Both params are later nullified to reduce overhead and increase performance.
 // The supportDynamicValueEvaluation is passed as a function so that it can be nullified. Otherwise, there is no need for the function value.
-final class CallByNeed[+A] private (private[this] var eval: () => A, private var supportDynamicValueEvaluation: () => Boolean)
+final class CallByNeed[+A] private (private var eval: () => A, private var supportDynamicValueEvaluation: () => Boolean)
     extends Serializable {
 
   // This second constructor is necessary to support backwards compatibility for v1.3.6 and earlier
diff --git a/core/src/main/scala/magnolia1/macro.scala b/core/src/main/scala/magnolia1/macro.scala
index 936abd12..34aad81b 100644
--- a/core/src/main/scala/magnolia1/macro.scala
+++ b/core/src/main/scala/magnolia1/macro.scala
@@ -147,10 +147,10 @@ object Macro:
     def normalizedName(s: Symbol): String =
       if s.flags.is(Flags.Module) then s.name.stripSuffix("$") else s.name
     def name(tpe: TypeRepr): Expr[String] = tpe.dealias match
-      case matchedTpe @ TermRef(typeRepr, name) if matchedTpe.typeSymbol.flags.is(Flags.Module) =>
+      case matchedTpe @ TermRef(_, name) if matchedTpe.typeSymbol.flags.is(Flags.Module) =>
         Expr(name.stripSuffix("$"))
-      case TermRef(typeRepr, name) => Expr(name)
-      case matchedTpe              => Expr(normalizedName(matchedTpe.typeSymbol))
+      case TermRef(_, name) => Expr(name)
+      case matchedTpe       => Expr(normalizedName(matchedTpe.typeSymbol))
 
     def ownerNameChain(sym: Symbol): List[String] =
       if sym.isNoSymbol then List.empty
diff --git a/core/src/main/scala/magnolia1/magnolia.scala b/core/src/main/scala/magnolia1/magnolia.scala
index 0cc048af..8ce3142b 100644
--- a/core/src/main/scala/magnolia1/magnolia.scala
+++ b/core/src/main/scala/magnolia1/magnolia.scala
@@ -1,6 +1,7 @@
 package magnolia1
 
 import scala.deriving.Mirror
+import scala.annotation.unused
 
 trait CommonDerivation[TypeClass[_]]:
   type Typeclass[T] = TypeClass[T]
@@ -26,7 +27,7 @@ trait CommonDerivation[TypeClass[_]]:
       typeAnnotations: Map[String, List[Any]],
       repeated: Map[String, Boolean],
       defaults: Map[String, Option[() => Any]],
-      idx: Int = 0
+      @unused idx: Int = 0
   ): List[CaseClass.Param[Typeclass, T]] = CaseClassDerivation.paramsFromMaps(
     annotations,
     inheritedAnnotations,
@@ -38,7 +39,7 @@ trait CommonDerivation[TypeClass[_]]:
   // for backward compatibility with v1.1.1
   inline def getParams_[T, Labels <: Tuple, Params <: Tuple](
       annotations: Map[String, List[Any]],
-      inheritedAnnotations: Map[String, List[Any]],
+      @unused inheritedAnnotations: Map[String, List[Any]],
       typeAnnotations: Map[String, List[Any]],
       repeated: Map[String, Boolean],
       idx: Int = 0
@@ -81,7 +82,7 @@ trait Derivation[TypeClass[_]] extends CommonDerivation[TypeClass] with SealedTr
   transparent inline def subtypes[T, SubtypeTuple <: Tuple](
       m: Mirror.SumOf[T],
       idx: Int = 0 // no longer used, kept for bincompat
-  ): List[SealedTrait.Subtype[Typeclass, T, _]] =
+  ): List[SealedTrait.Subtype[Typeclass, T, ?]] =
     subtypesFromMirror[T, SubtypeTuple](m, idx)
 
   inline def derivedMirrorSum[A](sum: Mirror.SumOf[A]): Typeclass[A] =
diff --git a/examples/src/main/scala/magnolia1/examples/nocombine.scala b/examples/src/main/scala/magnolia1/examples/nocombine.scala
index b0fc9f49..36d86a21 100644
--- a/examples/src/main/scala/magnolia1/examples/nocombine.scala
+++ b/examples/src/main/scala/magnolia1/examples/nocombine.scala
@@ -9,7 +9,7 @@ object NoCombine extends AutoDerivation[NoCombine]:
   type Typeclass[T] = NoCombine[T]
 
   def join[T](ctx: CaseClass[magnolia1.examples.NoCombine, T]): NoCombine[T] =
-    instance { value =>
+    instance { _ =>
       ctx.typeInfo.short
     }
 
diff --git a/examples/src/main/scala/magnolia1/examples/passthrough.scala b/examples/src/main/scala/magnolia1/examples/passthrough.scala
index 1e457812..c5cb1f4d 100644
--- a/examples/src/main/scala/magnolia1/examples/passthrough.scala
+++ b/examples/src/main/scala/magnolia1/examples/passthrough.scala
@@ -3,7 +3,7 @@ package magnolia1.examples
 import magnolia1._
 
 case class Passthrough[T](
-    ctx: Option[Either[CaseClass[_, T], SealedTrait[_, T]]]
+    ctx: Option[Either[CaseClass[?, T], SealedTrait[?, T]]]
 )
 object Passthrough extends Derivation[Passthrough]:
   def join[T](ctx: CaseClass[Passthrough, T]) = Passthrough(Some(Left(ctx)))
diff --git a/examples/src/main/scala/magnolia1/examples/patch.scala b/examples/src/main/scala/magnolia1/examples/patch.scala
index 6fad5791..5199054c 100644
--- a/examples/src/main/scala/magnolia1/examples/patch.scala
+++ b/examples/src/main/scala/magnolia1/examples/patch.scala
@@ -33,7 +33,7 @@ object Patcher extends LowerPriorityPatcher with AutoDerivation[Patcher]:
       ctx.choose(value)(sub => sub.typeclass.patch(sub.value, fieldValues))
 
 sealed abstract class LowerPriorityPatcher:
-  private[this] val _forSingleValue =
+  private val _forSingleValue =
     new Patcher[Any]:
       def patch(value: Any, fieldValues: Seq[Any]): Any = {
         if (fieldValues.lengthCompare(1) != 0)
diff --git a/examples/src/main/scala/magnolia1/examples/printRepeated.scala b/examples/src/main/scala/magnolia1/examples/printRepeated.scala
index fd43a7c7..2537e5a4 100644
--- a/examples/src/main/scala/magnolia1/examples/printRepeated.scala
+++ b/examples/src/main/scala/magnolia1/examples/printRepeated.scala
@@ -1,6 +1,7 @@
 package magnolia1.examples
 
 import magnolia1.*
+import scala.annotation.unused
 
 trait PrintRepeated[T]:
   def print(t: T): String
@@ -12,4 +13,4 @@ object PrintRepeated extends AutoDerivation[PrintRepeated]:
     ctx.choose(_) { sub => sub.typeclass.print(sub.value) }
 
   given PrintRepeated[String] = _ => ""
-  given seq[T](using printT: PrintRepeated[T]): PrintRepeated[Seq[T]] = _ => ""
+  given seq[T](using @unused printT: PrintRepeated[T]): PrintRepeated[Seq[T]] = _ => ""
diff --git a/test/src/test/scala/magnolia1/tests/OtherTests.scala b/test/src/test/scala/magnolia1/tests/OtherTests.scala
index 0ee4008c..e3d2c111 100644
--- a/test/src/test/scala/magnolia1/tests/OtherTests.scala
+++ b/test/src/test/scala/magnolia1/tests/OtherTests.scala
@@ -15,7 +15,7 @@ class OtherTests extends munit.FunSuite:
       Show.derived[Beta]
     """)
     assert(
-      clue(error) contains "No given instance of type magnolia1.examples.Show[String, Alpha] was found."
+      clue(error).contains("No given instance of type magnolia1.examples.Show[String, Alpha] was found.")
     )
   }
 
@@ -25,7 +25,7 @@ class OtherTests extends munit.FunSuite:
       Show.derived[Gamma]
     """)
     assert(
-      clue(error) contains "No given instance of type magnolia1.examples.Show[String, Unit] was found."
+      clue(error).contains("No given instance of type magnolia1.examples.Show[String, Unit] was found.")
     )
   }
 
@@ -34,7 +34,7 @@ class OtherTests extends munit.FunSuite:
     assert(
       clue(
         error
-      ) contains "No given instance of type magnolia1.examples.Show[String, Long & magnolia1.tests.OtherTests.Character.Tag] was found."
+      ).contains("No given instance of type magnolia1.examples.Show[String, Long & magnolia1.tests.OtherTests.Character.Tag] was found.")
     )
   }
 
@@ -94,12 +94,12 @@ object OtherTests:
   case class Character(id: Character.Id)
   object Character:
     trait Tag extends Any
-    type Id = Long with Tag
+    type Id = Long & Tag
 
   case class AnotherCharacter(id: AnotherCharacter.Id)
   object AnotherCharacter:
     trait Tag extends Any
-    type Id = Long with Tag
+    type Id = Long & Tag
     given Show[String, Id] = _.toString
 
   sealed trait Entity
diff --git a/test/src/test/scala/magnolia1/tests/ProductsTests.scala b/test/src/test/scala/magnolia1/tests/ProductsTests.scala
index 83de4c56..75402605 100644
--- a/test/src/test/scala/magnolia1/tests/ProductsTests.scala
+++ b/test/src/test/scala/magnolia1/tests/ProductsTests.scala
@@ -201,14 +201,14 @@ class ProductsTests extends munit.FunSuite:
   test("show chained error stack when leaf instance is missing") {
     val error = compileErrors("Show.derived[Schedule]")
     assert(
-      clue(error) contains "No given instance of type magnolia1.examples.Show[String, Seq[magnolia1.tests.ProductsTests.Event]] was found."
+      clue(error).contains("No given instance of type magnolia1.examples.Show[String, Seq[magnolia1.tests.ProductsTests.Event]] was found.")
     )
   }
 
   test("show chained error stack") {
     val error = compileErrors("Show.derived[(Int, Seq[(Double, String)])]")
     assert(
-      clue(error) contains "No given instance of type magnolia1.examples.Show[String, Seq[(Double, String)]] was found."
+      clue(error).contains("No given instance of type magnolia1.examples.Show[String, Seq[(Double, String)]] was found.")
     )
   }
 
diff --git a/test/src/test/scala/magnolia1/tests/RecursiveTypesTests.scala b/test/src/test/scala/magnolia1/tests/RecursiveTypesTests.scala
index aa0b12f8..42ac15f0 100644
--- a/test/src/test/scala/magnolia1/tests/RecursiveTypesTests.scala
+++ b/test/src/test/scala/magnolia1/tests/RecursiveTypesTests.scala
@@ -95,7 +95,7 @@ class RecursiveTypesTests extends munit.FunSuite:
     val error = compileErrors("ExportedTypeclass.derived[Recursive]")
     val expectedError =
       """Seq[magnolia1.tests.RecursiveTypesTests.Recursive]] was found."""
-    assert(clue(error) contains expectedError)
+    assert(clue(error).contains(expectedError))
   }
 
   test("serialize a CeList") {
diff --git a/test/src/test/scala/magnolia1/tests/SumsTests.scala b/test/src/test/scala/magnolia1/tests/SumsTests.scala
index bb37f818..54e13a14 100644
--- a/test/src/test/scala/magnolia1/tests/SumsTests.scala
+++ b/test/src/test/scala/magnolia1/tests/SumsTests.scala
@@ -206,12 +206,16 @@ class SumsTests extends munit.FunSuite:
     assert(
       clue(
         error
-      ) contains "No given instance of type scala.deriving.Mirror.Of[magnolia1.tests.SumsTests.Parent] was found for parameter x$1 of method derived in trait Derivation."
+      ).contains(
+        "No given instance of type scala.deriving.Mirror.Of[magnolia1.tests.SumsTests.Parent] was found for parameter x$1 of method derived in trait Derivation."
+      )
     )
     assert(
       clue(
         error
-      ) contains "trait Parent is not a generic sum because its child trait BadChild is not a generic product because it is not a case class"
+      ).contains(
+        "trait Parent is not a generic sum because its child trait BadChild is not a generic product because it is not a case class"
+      )
     )
   }
 
@@ -222,7 +226,9 @@ class SumsTests extends munit.FunSuite:
     assert(
       clue(
         error
-      ) contains "trait GoodChild is not a generic sum because its child class Dewey is not a generic product because it is not a case class"
+      ).contains(
+        "trait GoodChild is not a generic sum because its child class Dewey is not a generic product because it is not a case class"
+      )
     )
   }