diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0735f6fc5..a3909041d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,8 @@ Thank you!
 
 # 0.18.25
 
+* Add A flag to allow for numerics to be decoded from JSON strings (in smithy4s-json).
+* Fixes issues in which applications of some Smithy traits would be incorrectly rendered in Scala code (see [#1602](https://github.com/disneystreaming/smithy4s/pull/1602)).
 * Fixes an issue in which refinements wouldn't work on custom simple shapes (newtypes) (see [#1595](https://github.com/disneystreaming/smithy4s/pull/1595))
 * Fixes a regression from 0.18.4 which incorrectly rendered default values for certain types (see [#1593](https://github.com/disneystreaming/smithy4s/pull/1593))
 * Fixes an issue in which union members targetting Unit would fail to compile when used as traits (see [#1600](https://github.com/disneystreaming/smithy4s/pull/1600)).
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/DeprecatedUnion.scala b/modules/bootstrapped/src/generated/smithy4s/example/DeprecatedUnion.scala
index 4e8080a68..aa3006fd3 100644
--- a/modules/bootstrapped/src/generated/smithy4s/example/DeprecatedUnion.scala
+++ b/modules/bootstrapped/src/generated/smithy4s/example/DeprecatedUnion.scala
@@ -51,7 +51,7 @@ object DeprecatedUnion extends ShapeTag.Companion[DeprecatedUnion] {
     def $ordinal: Int = 2
   }
 
-  object DeprecatedUnionProductCase extends ShapeTag.Companion[DeprecatedUnionProductCase] {
+  object DeprecatedUnionProductCase {
     val id: ShapeId = ShapeId("smithy4s.example", "DeprecatedUnionProductCase")
 
     val hints: Hints = Hints(
@@ -59,7 +59,7 @@ object DeprecatedUnion extends ShapeTag.Companion[DeprecatedUnion] {
     ).lazily
 
 
-    implicit val schema: Schema[DeprecatedUnionProductCase] = constant(DeprecatedUnionProductCase()).withId(id).addHints(hints)
+    val schema: Schema[DeprecatedUnionProductCase] = constant(DeprecatedUnionProductCase()).withId(id).addHints(hints)
 
     val alt = schema.oneOf[DeprecatedUnion]("p")
   }
@@ -68,7 +68,7 @@ object DeprecatedUnion extends ShapeTag.Companion[DeprecatedUnion] {
     def $ordinal: Int = 3
   }
 
-  object UnionProductCaseDeprecatedAtCallSite extends ShapeTag.Companion[UnionProductCaseDeprecatedAtCallSite] {
+  object UnionProductCaseDeprecatedAtCallSite {
     val id: ShapeId = ShapeId("smithy4s.example", "UnionProductCaseDeprecatedAtCallSite")
 
     val hints: Hints = Hints(
@@ -76,7 +76,7 @@ object DeprecatedUnion extends ShapeTag.Companion[DeprecatedUnion] {
     ).lazily
 
 
-    implicit val schema: Schema[UnionProductCaseDeprecatedAtCallSite] = constant(UnionProductCaseDeprecatedAtCallSite()).withId(id).addHints(hints)
+    val schema: Schema[UnionProductCaseDeprecatedAtCallSite] = constant(UnionProductCaseDeprecatedAtCallSite()).withId(id).addHints(hints)
 
     val alt = schema.oneOf[DeprecatedUnion]("p2")
   }
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/OrderType.scala b/modules/bootstrapped/src/generated/smithy4s/example/OrderType.scala
index 5a2dcdd22..ec7071bbf 100644
--- a/modules/bootstrapped/src/generated/smithy4s/example/OrderType.scala
+++ b/modules/bootstrapped/src/generated/smithy4s/example/OrderType.scala
@@ -48,7 +48,7 @@ object OrderType extends ShapeTag.Companion[OrderType] {
     def $ordinal: Int = 1
   }
 
-  object InStoreOrder extends ShapeTag.Companion[InStoreOrder] {
+  object InStoreOrder {
     val id: ShapeId = ShapeId("smithy4s.example", "InStoreOrder")
 
     val hints: Hints = Hints(
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/PersonUnion.scala b/modules/bootstrapped/src/generated/smithy4s/example/PersonUnion.scala
index 830ce2d56..5e3e3b402 100644
--- a/modules/bootstrapped/src/generated/smithy4s/example/PersonUnion.scala
+++ b/modules/bootstrapped/src/generated/smithy4s/example/PersonUnion.scala
@@ -32,7 +32,7 @@ object PersonUnion extends ShapeTag.Companion[PersonUnion] {
     def $ordinal: Int = 0
   }
 
-  object OtherPerson extends ShapeTag.Companion[OtherPerson] {
+  object OtherPerson {
     val id: ShapeId = ShapeId("smithy4s.example", "OtherPerson")
 
     val hints: Hints = Hints.empty
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/Podcast.scala b/modules/bootstrapped/src/generated/smithy4s/example/Podcast.scala
index f5a10d5a3..08baea638 100644
--- a/modules/bootstrapped/src/generated/smithy4s/example/Podcast.scala
+++ b/modules/bootstrapped/src/generated/smithy4s/example/Podcast.scala
@@ -43,7 +43,7 @@ object Podcast extends ShapeTag.Companion[Podcast] {
     def $ordinal: Int = 0
   }
 
-  object Video extends ShapeTag.Companion[Video] {
+  object Video {
     val id: ShapeId = ShapeId("smithy4s.example", "Video")
 
     val hints: Hints = Hints.empty
@@ -69,7 +69,7 @@ object Podcast extends ShapeTag.Companion[Podcast] {
     def $ordinal: Int = 1
   }
 
-  object Audio extends ShapeTag.Companion[Audio] {
+  object Audio {
     val id: ShapeId = ShapeId("smithy4s.example", "Audio")
 
     val hints: Hints = Hints.empty
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/TestAdt.scala b/modules/bootstrapped/src/generated/smithy4s/example/TestAdt.scala
index 42b173c7a..d6287ac67 100644
--- a/modules/bootstrapped/src/generated/smithy4s/example/TestAdt.scala
+++ b/modules/bootstrapped/src/generated/smithy4s/example/TestAdt.scala
@@ -40,7 +40,7 @@ object TestAdt extends ShapeTag.Companion[TestAdt] {
     def $ordinal: Int = 0
   }
 
-  object AdtOne extends ShapeTag.Companion[AdtOne] {
+  object AdtOne {
     val id: ShapeId = ShapeId("smithy4s.example", "AdtOne")
 
     val hints: Hints = Hints.empty
@@ -61,7 +61,7 @@ object TestAdt extends ShapeTag.Companion[TestAdt] {
     def $ordinal: Int = 1
   }
 
-  object AdtTwo extends ShapeTag.Companion[AdtTwo] {
+  object AdtTwo {
     val id: ShapeId = ShapeId("smithy4s.example", "AdtTwo")
 
     val hints: Hints = Hints.empty
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/TestMixinAdt.scala b/modules/bootstrapped/src/generated/smithy4s/example/TestMixinAdt.scala
index 3bcbf9854..aab179c86 100644
--- a/modules/bootstrapped/src/generated/smithy4s/example/TestMixinAdt.scala
+++ b/modules/bootstrapped/src/generated/smithy4s/example/TestMixinAdt.scala
@@ -33,7 +33,7 @@ object TestMixinAdt extends ShapeTag.Companion[TestMixinAdt] {
     def $ordinal: Int = 0
   }
 
-  object TestAdtMemberWithMixin extends ShapeTag.Companion[TestAdtMemberWithMixin] {
+  object TestAdtMemberWithMixin {
     val id: ShapeId = ShapeId("smithy4s.example", "TestAdtMemberWithMixin")
 
     val hints: Hints = Hints.empty
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/TestString.scala b/modules/bootstrapped/src/generated/smithy4s/example/TestString.scala
index 152c04113..b9c3a417b 100644
--- a/modules/bootstrapped/src/generated/smithy4s/example/TestString.scala
+++ b/modules/bootstrapped/src/generated/smithy4s/example/TestString.scala
@@ -10,7 +10,7 @@ import smithy4s.schema.Schema.string
 object TestString extends Newtype[String] {
   val id: ShapeId = ShapeId("smithy4s.example", "TestString")
   val hints: Hints = Hints(
-    smithy4s.example.TestTrait(orderType = Some(smithy4s.example.OrderType.InStoreOrder(id = smithy4s.example.OrderNumber(100), locationId = Some("someLocation")))),
+    smithy4s.example.TestTrait(orderType = Some(smithy4s.example.OrderType.InStoreOrder(id = smithy4s.example.OrderNumber(100), locationId = Some("someLocation")).widen)),
   ).lazily
   val underlyingSchema: Schema[String] = string.withId(id).addHints(hints)
   implicit val schema: Schema[TestString] = bijection(underlyingSchema, asBijection)
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/_package/MyPackageStringTrait.scala b/modules/bootstrapped/src/generated/smithy4s/example/_package/MyPackageStringTrait.scala
new file mode 100644
index 000000000..b715f4b33
--- /dev/null
+++ b/modules/bootstrapped/src/generated/smithy4s/example/_package/MyPackageStringTrait.scala
@@ -0,0 +1,18 @@
+package smithy4s.example._package
+
+import smithy4s.Hints
+import smithy4s.Newtype
+import smithy4s.Schema
+import smithy4s.ShapeId
+import smithy4s.schema.Schema.bijection
+import smithy4s.schema.Schema.recursive
+import smithy4s.schema.Schema.string
+
+object MyPackageStringTrait extends Newtype[String] {
+  val id: ShapeId = ShapeId("smithy4s.example.package", "MyPackageStringTrait")
+  val hints: Hints = Hints(
+    smithy.api.Trait(selector = None, structurallyExclusive = None, conflicts = None, breakingChanges = None),
+  ).lazily
+  val underlyingSchema: Schema[String] = string.withId(id).addHints(hints)
+  implicit val schema: Schema[MyPackageStringTrait] = recursive(bijection(underlyingSchema, asBijection))
+}
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/_package/package.scala b/modules/bootstrapped/src/generated/smithy4s/example/_package/package.scala
index 28a781875..fffb0cbb9 100644
--- a/modules/bootstrapped/src/generated/smithy4s/example/_package/package.scala
+++ b/modules/bootstrapped/src/generated/smithy4s/example/_package/package.scala
@@ -3,5 +3,6 @@ package smithy4s.example
 package object _package {
 
   type MyPackageString = smithy4s.example._package.MyPackageString.Type
+  type MyPackageStringTrait = smithy4s.example._package.MyPackageStringTrait.Type
 
 }
\ No newline at end of file
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/collision/Class.scala b/modules/bootstrapped/src/generated/smithy4s/example/collision/Class.scala
new file mode 100644
index 000000000..8064d82cb
--- /dev/null
+++ b/modules/bootstrapped/src/generated/smithy4s/example/collision/Class.scala
@@ -0,0 +1,65 @@
+package smithy4s.example.collision
+
+import smithy4s.Hints
+import smithy4s.Schema
+import smithy4s.ShapeId
+import smithy4s.ShapeTag
+import smithy4s.schema.Schema.constant
+import smithy4s.schema.Schema.recursive
+import smithy4s.schema.Schema.union
+
+sealed trait Class extends scala.Product with scala.Serializable { self =>
+  @inline final def widen: Class = this
+  def $ordinal: Int
+
+  object project {
+    def _package: Option[Class.AdtStruct] = Class.AdtStruct.alt.project.lift(self)
+  }
+
+  def accept[A](visitor: Class.Visitor[A]): A = this match {
+    case value: Class.AdtStruct => visitor._package(value)
+  }
+}
+object Class extends ShapeTag.Companion[Class] {
+
+  def adtStruct():AdtStruct = AdtStruct()
+
+  val id: ShapeId = ShapeId("smithy4s.example.collision", "class")
+
+  val hints: Hints = Hints(
+    smithy.api.Trait(selector = None, structurallyExclusive = None, conflicts = None, breakingChanges = None),
+  ).lazily
+
+  final case class AdtStruct() extends Class {
+    def $ordinal: Int = 0
+  }
+
+  object AdtStruct {
+    val id: ShapeId = ShapeId("smithy4s.example.collision", "AdtStruct")
+
+    val hints: Hints = Hints.empty
+
+
+    val schema: Schema[AdtStruct] = constant(AdtStruct()).withId(id).addHints(hints)
+
+    val alt = schema.oneOf[Class]("package")
+  }
+
+
+  trait Visitor[A] {
+    def _package(value: Class.AdtStruct): A
+  }
+
+  object Visitor {
+    trait Default[A] extends Visitor[A] {
+      def default: A
+      def _package(value: Class.AdtStruct): A = default
+    }
+  }
+
+  implicit val schema: Schema[Class] = recursive(union(
+    Class.AdtStruct.alt,
+  ){
+    _.$ordinal
+  }.withId(id).addHints(hints))
+}
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/collision/ReservedNameUnionTrait.scala b/modules/bootstrapped/src/generated/smithy4s/example/collision/ReservedNameUnionTrait.scala
new file mode 100644
index 000000000..d1d388b4d
--- /dev/null
+++ b/modules/bootstrapped/src/generated/smithy4s/example/collision/ReservedNameUnionTrait.scala
@@ -0,0 +1,17 @@
+package smithy4s.example.collision
+
+import smithy4s.Hints
+import smithy4s.Newtype
+import smithy4s.Schema
+import smithy4s.ShapeId
+import smithy4s.schema.Schema.bijection
+import smithy4s.schema.Schema.string
+
+object ReservedNameUnionTrait extends Newtype[java.lang.String] {
+  val id: ShapeId = ShapeId("smithy4s.example.collision", "ReservedNameUnionTrait")
+  val hints: Hints = Hints(
+    smithy4s.example.collision.Class.AdtStruct().widen,
+  ).lazily
+  val underlyingSchema: Schema[java.lang.String] = string.withId(id).addHints(hints)
+  implicit val schema: Schema[ReservedNameUnionTrait] = bijection(underlyingSchema, asBijection)
+}
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/collision/TestReservedNamespaceTrait.scala b/modules/bootstrapped/src/generated/smithy4s/example/collision/TestReservedNamespaceTrait.scala
new file mode 100644
index 000000000..58cbc0b3f
--- /dev/null
+++ b/modules/bootstrapped/src/generated/smithy4s/example/collision/TestReservedNamespaceTrait.scala
@@ -0,0 +1,17 @@
+package smithy4s.example.collision
+
+import smithy4s.Hints
+import smithy4s.Newtype
+import smithy4s.Schema
+import smithy4s.ShapeId
+import smithy4s.schema.Schema.bijection
+import smithy4s.schema.Schema.string
+
+object TestReservedNamespaceTrait extends Newtype[java.lang.String] {
+  val id: ShapeId = ShapeId("smithy4s.example.collision", "TestReservedNamespaceTrait")
+  val hints: Hints = Hints(
+    smithy4s.example._package.MyPackageStringTrait("test"),
+  ).lazily
+  val underlyingSchema: Schema[java.lang.String] = string.withId(id).addHints(hints)
+  implicit val schema: Schema[TestReservedNamespaceTrait] = bijection(underlyingSchema, asBijection)
+}
diff --git a/modules/bootstrapped/src/generated/smithy4s/example/collision/package.scala b/modules/bootstrapped/src/generated/smithy4s/example/collision/package.scala
index f7f33c849..bde7a66bd 100644
--- a/modules/bootstrapped/src/generated/smithy4s/example/collision/package.scala
+++ b/modules/bootstrapped/src/generated/smithy4s/example/collision/package.scala
@@ -9,6 +9,8 @@ package object collision {
   type MySet = smithy4s.example.collision.MySet.Type
   type ReservedKeywordTraitExampleCollection = smithy4s.example.collision.ReservedKeywordTraitExampleCollection.Type
   type ReservedKeywordTraitExamplePrimitive = smithy4s.example.collision.ReservedKeywordTraitExamplePrimitive.Type
+  type ReservedNameUnionTrait = smithy4s.example.collision.ReservedNameUnionTrait.Type
   type String = smithy4s.example.collision.String.Type
+  type TestReservedNamespaceTrait = smithy4s.example.collision.TestReservedNamespaceTrait.Type
 
 }
\ No newline at end of file
diff --git a/modules/bootstrapped/test/src-js/smithy4s/TimestampSpec.scala b/modules/bootstrapped/test/src-js/smithy4s/TimestampSpec.scala
index 0ee6c9cf9..010041363 100644
--- a/modules/bootstrapped/test/src-js/smithy4s/TimestampSpec.scala
+++ b/modules/bootstrapped/test/src-js/smithy4s/TimestampSpec.scala
@@ -216,4 +216,30 @@ class TimestampSpec() extends munit.FunSuite with munit.ScalaCheckSuite {
       expect.same(tsFromEpochMilli, ts)
     }
   }
+
+  property("Truncate to milliseconds precision") {
+    forAll { (d: Date) =>
+      val epochMilli = d.valueOf().toLong
+      val ts = Timestamp.fromDate(d).truncateToMillis
+
+      val strippedDate = new Date(0)
+      strippedDate.setUTCMilliseconds(epochMilli)
+      val tsFromStrippedDate = Timestamp.fromDate(strippedDate)
+
+      expect.same(ts, tsFromStrippedDate)
+    }
+  }
+
+  property("Truncate to seconds precision") {
+    forAll { (d: Date) =>
+      val epochSecond = (d.valueOf() / 1000).toLong
+      val ts = Timestamp.fromDate(d).truncateToMillis
+
+      val strippedDate = new Date(0)
+      strippedDate.setUTCSeconds(epochSecond)
+      val tsFromStrippedDate = Timestamp.fromDate(strippedDate)
+
+      expect.same(ts, tsFromStrippedDate)
+    }
+  }
 }
diff --git a/modules/bootstrapped/test/src-jvm/smithy4s/TimestampSpec.scala b/modules/bootstrapped/test/src-jvm/smithy4s/TimestampSpec.scala
index f2b8e40bc..f0b928627 100644
--- a/modules/bootstrapped/test/src-jvm/smithy4s/TimestampSpec.scala
+++ b/modules/bootstrapped/test/src-jvm/smithy4s/TimestampSpec.scala
@@ -224,4 +224,23 @@ class TimestampSpec() extends munit.FunSuite with munit.ScalaCheckSuite {
       expect.same(tsFromEpochMilli, tsFromStrippedInstant)
     }
   }
+
+  property("Truncate to milliseconds precision") {
+    forAll { (i: Instant) =>
+      val ts = Timestamp.fromInstant(i).truncateToMillis
+      val strippedInstant = Instant.ofEpochMilli(i.toEpochMilli)
+      val tsFromStrippedInstant = Timestamp.fromInstant(strippedInstant)
+
+      expect.same(ts, tsFromStrippedInstant)
+    }
+  }
+
+  property("Truncate to seconds precision") {
+    forAll { (i: Instant) =>
+      val ts = Timestamp.fromInstant(i).truncateToSeconds
+      val tsFromStrippedInstant = Timestamp.fromEpochSecond(i.getEpochSecond)
+
+      expect.same(ts, tsFromStrippedInstant)
+    }
+  }
 }
diff --git a/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/build.sbt b/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/build.sbt
new file mode 100644
index 000000000..5b4e4ab9d
--- /dev/null
+++ b/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/build.sbt
@@ -0,0 +1,8 @@
+lazy val root = (project in file("."))
+  .enablePlugins(Smithy4sCodegenPlugin)
+  .settings(
+    crossScalaVersions := Seq("2.13.15", "3.3.3"),
+    libraryDependencies ++= Seq(
+      "com.disneystreaming.smithy4s" %% "smithy4s-core" % smithy4sVersion.value
+    )
+  )
diff --git a/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/project/build.properties b/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/project/build.properties
new file mode 100644
index 000000000..8b9a0b0ab
--- /dev/null
+++ b/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/project/build.properties
@@ -0,0 +1 @@
+sbt.version=1.8.0
diff --git a/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/project/plugins.sbt b/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/project/plugins.sbt
new file mode 100644
index 000000000..b8589b92c
--- /dev/null
+++ b/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/project/plugins.sbt
@@ -0,0 +1,9 @@
+sys.props.get("plugin.version") match {
+  case Some(x) =>
+    addSbtPlugin("com.disneystreaming.smithy4s" % "smithy4s-sbt-codegen" % x)
+  case _ =>
+    sys.error(
+      """|The system property 'plugin.version' is not defined.
+         |Specify this property using the scriptedLaunchOpts -D.""".stripMargin
+    )
+}
diff --git a/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/src/main/smithy/simple.smithy b/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/src/main/smithy/simple.smithy
new file mode 100644
index 000000000..522b18cff
--- /dev/null
+++ b/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/src/main/smithy/simple.smithy
@@ -0,0 +1,3 @@
+namespace smithy4s.example
+
+structure Simple {}
diff --git a/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/test b/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/test
new file mode 100644
index 000000000..977249eef
--- /dev/null
+++ b/modules/codegen-plugin/src/sbt-test/codegen-plugin/cross-builds/test
@@ -0,0 +1,19 @@
+# generate for Scala 2.13
+> ++ 2.13
+> compile
+
+$ exists target/scala-2.13/src_managed/main/smithy/generated-metadata.smithy
+$ exists target/scala-2.13/src_managed/main/smithy4s/smithy4s/example/Simple.scala
+
+> ++ 3
+> compile
+
+$ exists target/scala-3.3.3/src_managed/main/smithy/generated-metadata.smithy
+$ exists target/scala-3.3.3/src_managed/main/smithy4s/smithy4s/example/Simple.scala
+
+# switch back to Scala 2.13 and compile again; codegen should not happen a second time
+> ++ 2.13
+> compile
+
+$ newer target/scala-3.3.3/src_managed/main/smithy/generated-metadata.smithy target/scala-2.13/src_managed/main/smithy/generated-metadata.smithy
+$ newer target/scala-3.3.3/src_managed/main/smithy4s/smithy4s/example/Simple.scala target/scala-2.13/src_managed/main/smithy4s/smithy4s/example/Simple.scala
diff --git a/modules/codegen-plugin/src/smithy4s/codegen/Smithy4sCodegenPlugin.scala b/modules/codegen-plugin/src/smithy4s/codegen/Smithy4sCodegenPlugin.scala
index d0d15baae..a97ac8a3c 100644
--- a/modules/codegen-plugin/src/smithy4s/codegen/Smithy4sCodegenPlugin.scala
+++ b/modules/codegen-plugin/src/smithy4s/codegen/Smithy4sCodegenPlugin.scala
@@ -264,7 +264,8 @@ object Smithy4sCodegenPlugin extends AutoPlugin {
       (config / sourceManaged).value / "smithy" / "generated-metadata.smithy"
     },
     config / smithy4sGeneratedSmithyFiles := {
-      val cacheFactory = (config / streams).value.cacheStoreFactory
+      val cacheFactory =
+        (config / streams).value.cacheStoreFactory.sub(scalaVersion.value)
       val cached = Tracked.inputChanged[(String, Boolean), Seq[File]](
         cacheFactory.make("smithy4sGeneratedSmithyFilesInput")
       ) { case (changed, (wildcardArg, shouldGenerateOptics)) =>
@@ -454,14 +455,15 @@ object Smithy4sCodegenPlugin extends AutoPlugin {
       smithyBuild = smithyBuildValue
     )
 
+    val cacheStoreFactory = s.cacheStoreFactory.sub(scalaVersion.value)
     val cached =
       CachedTask.inputChanged[CodegenArgs, Seq[File]](
-        s.cacheStoreFactory.make("input"),
+        cacheStoreFactory.make("input"),
         s.log
       ) {
         Function.untupled {
           Tracked.lastOutput[(Boolean, CodegenArgs), Seq[File]](
-            s.cacheStoreFactory.make("output")
+            cacheStoreFactory.make("output")
           ) { case ((inputChanged, args), outputs) =>
             if (inputChanged || outputs.isEmpty) {
               s.log.debug(s"[smithy4s] Input changed: $inputChanged")
diff --git a/modules/codegen/src/smithy4s/codegen/internals/CollisionAvoidance.scala b/modules/codegen/src/smithy4s/codegen/internals/CollisionAvoidance.scala
index f6b6e2f87..b72e2cdce 100644
--- a/modules/codegen/src/smithy4s/codegen/internals/CollisionAvoidance.scala
+++ b/modules/codegen/src/smithy4s/codegen/internals/CollisionAvoidance.scala
@@ -243,6 +243,11 @@ private[internals] object CollisionAvoidance {
         case ValidatedNewTypeTN(ref, target) =>
           ValidatedNewTypeTN(modRef(ref), target)
         case AltTN(ref, altName, alt) =>
+          // note: technically we should probably escape altName here
+          // but it'd only really break if it matched a capitalized keyword,
+          // and Scala has none of those, so it's impossible to write a failing test.
+          // Alt names in this context are always capitalized before being printed
+          // (Renderer.scala:1614 at the time of writing).
           AltTN(modRef(ref), altName, alt)
         case MapTN(values) =>
           MapTN(values)
diff --git a/modules/codegen/src/smithy4s/codegen/internals/IR.scala b/modules/codegen/src/smithy4s/codegen/internals/IR.scala
index 3519c1d3a..9a74a1db6 100644
--- a/modules/codegen/src/smithy4s/codegen/internals/IR.scala
+++ b/modules/codegen/src/smithy4s/codegen/internals/IR.scala
@@ -305,7 +305,10 @@ private[internals] object Type {
       valueHints: List[Hint]
   ) extends Type
   case class Ref(namespace: String, name: String) extends Type {
-    def show = namespace + "." + name
+    def show: String = NameRef
+      .splitPath(namespace)
+      .map(CollisionAvoidance.protectKeyword)
+      .mkString(".") + "." + name
   }
   case class Alias(
       namespace: String,
diff --git a/modules/codegen/src/smithy4s/codegen/internals/LineSegment.scala b/modules/codegen/src/smithy4s/codegen/internals/LineSegment.scala
index 1e69019e0..bdcfb1375 100644
--- a/modules/codegen/src/smithy4s/codegen/internals/LineSegment.scala
+++ b/modules/codegen/src/smithy4s/codegen/internals/LineSegment.scala
@@ -95,13 +95,17 @@ private[codegen] object LineSegment {
     )
     implicit val nameRefShow: Show[NameRef] = Show.show[NameRef](_.asImport)
     def apply(pkg: String, name: String): NameRef =
-      NameRef(pkg.split("\\.").toList, name, List.empty)
+      NameRef(splitPath(pkg), name, List.empty)
     def apply(fqn: String): NameRef = {
-      val parts = fqn.split("\\.").toList.toNel.get
+      val parts =
+        splitPath(fqn).toNel.getOrElse(sys.error(s"Invalid FQN: $fqn"))
       NameRef(parts.toList.dropRight(1), parts.last, List.empty)
     }
     def apply(fqn: String, typeParams: List[NameRef]): NameRef =
       apply(fqn).copy(typeParams = typeParams)
+
+    private[internals] def splitPath(pkg: String): List[String] =
+      pkg.split("\\.").toList
   }
 
   implicit val lineSegmentShow: Show[LineSegment] = Show.show {
diff --git a/modules/codegen/src/smithy4s/codegen/internals/Renderer.scala b/modules/codegen/src/smithy4s/codegen/internals/Renderer.scala
index ae4de8862..0fd3b734b 100644
--- a/modules/codegen/src/smithy4s/codegen/internals/Renderer.scala
+++ b/modules/codegen/src/smithy4s/codegen/internals/Renderer.scala
@@ -711,7 +711,7 @@ private[internals] class Renderer(compilationUnit: CompilationUnit) { self =>
           }
       },
       newline,
-      obj(product.nameRef, shapeTag(product.nameRef))(
+      obj(product.nameRef, if (adtParent.isEmpty) shapeTag(product.nameRef) else Line.empty)(
         renderId(shapeId),
         newline,
         renderHintsVal(hints),
@@ -776,7 +776,7 @@ private[internals] class Renderer(compilationUnit: CompilationUnit) { self =>
               .appendToLast(if (recursive) ")" else "")
           }
         } else {
-          line"implicit val schema: $Schema_[${product.nameRef}] = $constant_(${product.nameRef}()).withId(id).addHints(hints)"
+          line"${schemaImplicit}val schema: $Schema_[${product.nameRef}] = $constant_(${product.nameRef}()).withId(id).addHints(hints)"
         },
         renderTypeclasses(product.hints, product.nameRef),
         additionalLines
@@ -1583,7 +1583,7 @@ private[internals] class Renderer(compilationUnit: CompilationUnit) { self =>
 
   private def renderTypedNode(tn: TypedNode[CString]): CString = tn match {
     case EnumerationTN(ref, _, _, name) =>
-      line"${ref.show + "." + name + ".widen"}".write
+      line"${ref.show}.$name.widen".write
     case StructureTN(ref, fields) =>
       val fieldStrings = fields.map {
         case (name, FieldTN.RequiredTN(value)) =>
@@ -1617,7 +1617,9 @@ private[internals] class Renderer(compilationUnit: CompilationUnit) { self =>
       line"${ref.show}.${altName.capitalize}Case.widen".write
 
     case AltTN(_, _, AltValueTN.ProductAltTN(alt)) =>
-      alt.runDefault.write
+      // The `widen` is necessary in Scala 2.
+      // Without it, there is no ShapeTag to use for the conversion to Hints.Binding.
+      line"${alt.runDefault}.widen".write
 
     case CollectionTN(collectionType, values) =>
       val col = collectionType.tpe
diff --git a/modules/codegen/src/smithy4s/codegen/internals/SmithyToIR.scala b/modules/codegen/src/smithy4s/codegen/internals/SmithyToIR.scala
index 0ccc14bd2..bcdd5c27d 100644
--- a/modules/codegen/src/smithy4s/codegen/internals/SmithyToIR.scala
+++ b/modules/codegen/src/smithy4s/codegen/internals/SmithyToIR.scala
@@ -1237,7 +1237,7 @@ private[codegen] class SmithyToIR(
             case Some(parent) =>
               val cId = shape.getId
               val newNs =
-                cId.getNamespace + "." + parent.getName
+                cId.getNamespace + "." + parent.getName.capitalize
               val error = new Exception(
                 s"Shapes annotated with the adtMemberTrait must be structures. $cId is not a structure."
               )
diff --git a/modules/core/src-js/smithy4s/Timestamp.scala b/modules/core/src-js/smithy4s/Timestamp.scala
index e8e695c02..d20e83d36 100644
--- a/modules/core/src-js/smithy4s/Timestamp.scala
+++ b/modules/core/src-js/smithy4s/Timestamp.scala
@@ -47,6 +47,16 @@ case class Timestamp private (epochSecond: Long, nano: Int) {
     date
   }
 
+  /**
+    * @return a copy of this timestamp truncated to a miliseconds precision
+    */
+  def truncateToMillis: Timestamp = copy(nano = (nano / 1000000) * 1000000)
+
+  /**
+    * @return a copy of this timestamp truncated to a seconds resolution
+    */
+  def truncateToSeconds: Timestamp = copy(nano = 0)
+
   override def toString: String = format(TimestampFormat.DATE_TIME)
 
   private[this] def formatToString(internalFormat: Int): String = {
diff --git a/modules/core/src-jvm-native/smithy4s/Timestamp.scala b/modules/core/src-jvm-native/smithy4s/Timestamp.scala
index ce3664e5c..0e71dac44 100644
--- a/modules/core/src-jvm-native/smithy4s/Timestamp.scala
+++ b/modules/core/src-jvm-native/smithy4s/Timestamp.scala
@@ -39,6 +39,16 @@ case class Timestamp private (epochSecond: Long, nano: Int)
 
   def conciseDate: String = formatToString(2)
 
+  /**
+    * @return a copy of this timestamp truncated to a miliseconds precision
+    */
+  def truncateToMillis: Timestamp = copy(nano = (nano / 1000000) * 1000000)
+
+  /**
+    * @return a copy of this timestamp truncated to a seconds resolution
+    */
+  def truncateToSeconds: Timestamp = copy(nano = 0)
+
   override def toString: String = format(TimestampFormat.DATE_TIME)
 
   private[this] def formatToString(internalFormat: Int): String = {
diff --git a/modules/docs/markdown/03-protocols/04-simple-rest-json/01-overview.md b/modules/docs/markdown/03-protocols/04-simple-rest-json/01-overview.md
index 1726a52f4..f57de12c0 100644
--- a/modules/docs/markdown/03-protocols/04-simple-rest-json/01-overview.md
+++ b/modules/docs/markdown/03-protocols/04-simple-rest-json/01-overview.md
@@ -90,6 +90,14 @@ See the section about [unions](../../04-codegen/02-unions.md) for a detailed des
 
 By default, optional properties (headers, query parameters, structure fields) that are set to `None` and optional properties that are set to default value will be excluded during encoding process. If you wish to change this so that instead they are included and set to `null` explicitly, you can do so by calling `.withExplicitDefaultsEncoding(true)`.
 
+## Other customisations of JSON codec behaviour
+
+The underlying JSON codecs can be configured with a number of options to cater to niche usecases, via the `.transformJsonCodecs` method, which takes a function that takes in and returns a
+`JsonPayloadCodecCompiler`. For instance, by default, the `NaN` and `Infinity` values are not considered valid during parsing `Float` or `Double` values. This can be amended via
+`.transformJsonCodecs(_.configureJsoniterCodecCompiler(_.withInfinitySupport(true)))`.
+
+The customisations are bound to evolve as we uncover new niche cases that warrant adding new pieces of opt-in behaviour. The default behaviour is kept rather strict as it helps keep competitive performance and safety.
+
 ## Supported traits
 
 Here is the list of traits supported by `SimpleRestJson`
diff --git a/modules/http4s/src/smithy4s/http4s/SimpleRestJsonBuilder.scala b/modules/http4s/src/smithy4s/http4s/SimpleRestJsonBuilder.scala
index f4c76f516..6d3e96226 100644
--- a/modules/http4s/src/smithy4s/http4s/SimpleRestJsonBuilder.scala
+++ b/modules/http4s/src/smithy4s/http4s/SimpleRestJsonBuilder.scala
@@ -17,7 +17,17 @@
 package smithy4s
 package http4s
 
-object SimpleRestJsonBuilder extends SimpleRestJsonBuilder(1024, false, true)
+import smithy4s.json.Json
+import smithy4s.json.JsonPayloadCodecCompiler
+
+object SimpleRestJsonBuilder
+    extends SimpleRestJsonBuilder(
+      new internals.SimpleRestJsonCodecs(
+        jsonCodecs = Json.payloadCodecs,
+        explicitDefaultsEncoding = false,
+        hostPrefixInjection = true
+      )
+    )
 
 class SimpleRestJsonBuilder private (
     simpleRestJsonCodecs: internals.SimpleRestJsonCodecs
@@ -25,6 +35,7 @@ class SimpleRestJsonBuilder private (
       simpleRestJsonCodecs
     ) {
 
+  @deprecated(message = "Use .withXXX methods instead", since = "0.18.25")
   def this(
       maxArity: Int,
       explicitDefaultsEncoding: Boolean,
@@ -32,7 +43,12 @@ class SimpleRestJsonBuilder private (
   ) =
     this(
       new internals.SimpleRestJsonCodecs(
-        maxArity,
+        Json.payloadCodecs
+          .withJsoniterCodecCompiler(
+            Json.jsoniter
+              .withMaxArity(maxArity)
+              .withExplicitDefaultsEncoding(explicitDefaultsEncoding)
+          ),
         explicitDefaultsEncoding,
         hostPrefixInjection
       )
@@ -40,24 +56,28 @@ class SimpleRestJsonBuilder private (
 
   def withMaxArity(maxArity: Int): SimpleRestJsonBuilder =
     new SimpleRestJsonBuilder(
-      maxArity,
-      simpleRestJsonCodecs.explicitDefaultsEncoding,
-      simpleRestJsonCodecs.hostPrefixInjection
+      simpleRestJsonCodecs.transformJsonCodecs(
+        _.configureJsoniterCodecCompiler(_.withMaxArity(maxArity))
+      )
     )
 
   def withExplicitDefaultsEncoding(
       explicitDefaultsEncoding: Boolean
   ): SimpleRestJsonBuilder =
     new SimpleRestJsonBuilder(
-      simpleRestJsonCodecs.maxArity,
-      explicitDefaultsEncoding,
-      simpleRestJsonCodecs.hostPrefixInjection
+      simpleRestJsonCodecs.withExplicitDefaultEncoding(explicitDefaultsEncoding)
     )
 
   def disableHostPrefixInjection(): SimpleRestJsonBuilder =
     new SimpleRestJsonBuilder(
-      simpleRestJsonCodecs.maxArity,
-      simpleRestJsonCodecs.explicitDefaultsEncoding,
-      false
+      simpleRestJsonCodecs.withHostPrefixInjection(false)
     )
+
+  /**
+    * Transforms the underlying JSON codec compiler to change its behaviour.
+    */
+  def transformJsonCodecs(
+      f: JsonPayloadCodecCompiler => JsonPayloadCodecCompiler
+  ): SimpleRestJsonBuilder =
+    new SimpleRestJsonBuilder(simpleRestJsonCodecs.transformJsonCodecs(f))
 }
diff --git a/modules/http4s/src/smithy4s/http4s/internals/SimpleRestJsonCodecs.scala b/modules/http4s/src/smithy4s/http4s/internals/SimpleRestJsonCodecs.scala
index b7f7648fa..da153c842 100644
--- a/modules/http4s/src/smithy4s/http4s/internals/SimpleRestJsonCodecs.scala
+++ b/modules/http4s/src/smithy4s/http4s/internals/SimpleRestJsonCodecs.scala
@@ -24,7 +24,6 @@ import smithy4s.http.HttpDiscriminator
 import smithy4s.http.Metadata
 import smithy4s.http._
 import smithy4s.http4s.kernel._
-import smithy4s.json.Json
 import smithy4s.client._
 import smithy4s.codecs.BlobEncoder
 import cats.syntax.all._
@@ -32,30 +31,36 @@ import org.http4s.Response
 import org.http4s.Request
 import org.http4s.Uri
 import smithy4s.http.HttpMethod
+import smithy4s.json.JsonPayloadCodecCompiler
 
 // scalafmt: {maxColumn = 120}
 private[http4s] class SimpleRestJsonCodecs(
-    val maxArity: Int,
+    val jsonCodecs: JsonPayloadCodecCompiler,
     val explicitDefaultsEncoding: Boolean,
     val hostPrefixInjection: Boolean
 ) extends SimpleProtocolCodecs {
   private val hintMask =
     alloy.SimpleRestJson.protocol.hintMask
 
-  private val jsonCodecs = Json.payloadCodecs
-    .withJsoniterCodecCompiler(
-      Json.jsoniter
-        .withHintMask(hintMask)
-        .withMaxArity(maxArity)
-        .withExplicitDefaultsEncoding(explicitDefaultsEncoding)
+  def transformJsonCodecs(f: JsonPayloadCodecCompiler => JsonPayloadCodecCompiler): SimpleRestJsonCodecs =
+    new SimpleRestJsonCodecs(f(jsonCodecs), explicitDefaultsEncoding, hostPrefixInjection)
+
+  def withExplicitDefaultEncoding(newExplicitDefaultsEncoding: Boolean): SimpleRestJsonCodecs =
+    new SimpleRestJsonCodecs(
+      jsonCodecs.configureJsoniterCodecCompiler(_.withExplicitDefaultsEncoding(newExplicitDefaultsEncoding)),
+      newExplicitDefaultsEncoding,
+      hostPrefixInjection
     )
 
+  def withHostPrefixInjection(newHostPrefixInjection: Boolean): SimpleRestJsonCodecs =
+    new SimpleRestJsonCodecs(jsonCodecs, explicitDefaultsEncoding, newHostPrefixInjection)
+
   // val mediaType = HttpMediaType("application/json")
   private val payloadEncoders: BlobEncoder.Compiler =
-    jsonCodecs.encoders
+    jsonCodecs.configureJsoniterCodecCompiler(_.withHintMask(hintMask)).encoders
 
   private val payloadDecoders =
-    jsonCodecs.decoders
+    jsonCodecs.configureJsoniterCodecCompiler(_.withHintMask(hintMask)).decoders
 
   // Adding X-Amzn-Errortype as well to facilitate interop with Amazon-issued code-generators.
   private val errorHeaders = List(
diff --git a/modules/json/src/smithy4s/json/JsoniterCodecCompiler.scala b/modules/json/src/smithy4s/json/JsoniterCodecCompiler.scala
index a8a8ee8a7..fd032f266 100644
--- a/modules/json/src/smithy4s/json/JsoniterCodecCompiler.scala
+++ b/modules/json/src/smithy4s/json/JsoniterCodecCompiler.scala
@@ -78,6 +78,12 @@ trait JsoniterCodecCompiler extends CachedSchemaCompiler[JsonCodec] {
     */
   def withLenientTaggedUnionDecoding: JsoniterCodecCompiler
 
+  /**
+    * Enables lenient decoding of numeric values, where numbers may be carried by JSON strings
+    * as well as JSON numbers.
+    */
+  def withLenientNumericDecoding: JsoniterCodecCompiler
+
 }
 
 object JsoniterCodecCompiler {
diff --git a/modules/json/src/smithy4s/json/internals/JsoniterCodecCompilerImpl.scala b/modules/json/src/smithy4s/json/internals/JsoniterCodecCompilerImpl.scala
index 09fbc9bc3..92d3afd50 100644
--- a/modules/json/src/smithy4s/json/internals/JsoniterCodecCompilerImpl.scala
+++ b/modules/json/src/smithy4s/json/internals/JsoniterCodecCompilerImpl.scala
@@ -27,7 +27,8 @@ private[smithy4s] case class JsoniterCodecCompilerImpl(
     infinitySupport: Boolean,
     preserveMapOrder: Boolean,
     hintMask: Option[HintMask],
-    lenientTaggedUnionDecoding: Boolean
+    lenientTaggedUnionDecoding: Boolean,
+    lenientNumericDecoding: Boolean
 ) extends CachedSchemaCompiler.Impl[JCodec]
     with JsoniterCodecCompiler {
 
@@ -59,6 +60,9 @@ private[smithy4s] case class JsoniterCodecCompilerImpl(
   def withLenientTaggedUnionDecoding: JsoniterCodecCompiler =
     copy(lenientTaggedUnionDecoding = true)
 
+  def withLenientNumericDecoding: JsoniterCodecCompiler =
+    copy(lenientNumericDecoding = true)
+
   def fromSchema[A](schema: Schema[A], cache: Cache): JCodec[A] = {
     val visitor = new SchemaVisitorJCodec(
       maxArity,
@@ -67,6 +71,7 @@ private[smithy4s] case class JsoniterCodecCompilerImpl(
       flexibleCollectionsSupport,
       preserveMapOrder,
       lenientTaggedUnionDecoding,
+      lenientNumericDecoding,
       cache
     )
     val amendedSchema =
@@ -88,6 +93,7 @@ private[smithy4s] object JsoniterCodecCompilerImpl {
       flexibleCollectionsSupport = false,
       preserveMapOrder = false,
       lenientTaggedUnionDecoding = false,
+      lenientNumericDecoding = false,
       hintMask = Some(JsoniterCodecCompiler.defaultHintMask)
     )
 
diff --git a/modules/json/src/smithy4s/json/internals/SchemaVisitorJCodec.scala b/modules/json/src/smithy4s/json/internals/SchemaVisitorJCodec.scala
index f4df6330c..354b72e81 100644
--- a/modules/json/src/smithy4s/json/internals/SchemaVisitorJCodec.scala
+++ b/modules/json/src/smithy4s/json/internals/SchemaVisitorJCodec.scala
@@ -47,10 +47,14 @@ private[smithy4s] class SchemaVisitorJCodec(
     flexibleCollectionsSupport: Boolean,
     preserveMapOrder: Boolean,
     lenientTaggedUnionDecoding: Boolean,
+    lenientNumericDecoding: Boolean,
     val cache: CompilationCache[JCodec]
 ) extends SchemaVisitor.Cached[JCodec] { self =>
   private val emptyMetadata: MMap[String, Any] = MMap.empty
 
+  private val allowJsonStringNumerics =
+    lenientNumericDecoding || infinitySupport
+
   object PrimitiveJCodecs {
     val boolean: JCodec[Boolean] =
       new JCodec[Boolean] {
@@ -80,153 +84,194 @@ private[smithy4s] class SchemaVisitorJCodec(
         def encodeKey(x: String, out: JsonWriter): Unit = out.writeKey(x)
       }
 
-    val int: JCodec[Int] =
-      new JCodec[Int] {
-        def expecting: String = "int"
+    private abstract class NumericJCodec[A] extends JCodec[A] {
+      def decodeJsonNumber(cursor: Cursor, in: JsonReader): A
+      // Allows numerics to be received as JSON Strings
+      def decodeJsonString(cursor: Cursor, in: JsonReader): A
 
-        def decodeValue(cursor: Cursor, in: JsonReader): Int = in.readInt()
+      final def decodeValue(cursor: Cursor, in: JsonReader): A =
+        if (allowJsonStringNumerics) {
+          if (in.isNextToken('"')) {
+            in.rollbackToken()
+            decodeJsonString(cursor, in)
+          } else {
+            in.rollbackToken()
+            decodeJsonNumber(cursor, in)
+          }
+        } else {
+          decodeJsonNumber(cursor, in)
+        }
+    }
 
-        def encodeValue(x: Int, out: JsonWriter): Unit = out.writeVal(x)
+    val int: JCodec[Int] = new NumericJCodec[Int] {
+      def expecting: String = "int"
 
-        def decodeKey(in: JsonReader): Int = in.readKeyAsInt()
+      def decodeJsonNumber(cursor: Cursor, in: JsonReader): Int =
+        in.readInt()
 
-        def encodeKey(x: Int, out: JsonWriter): Unit = out.writeKey(x)
-      }
+      def decodeJsonString(cursor: Cursor, in: JsonReader): Int =
+        in.readStringAsInt()
 
-    val long: JCodec[Long] =
-      new JCodec[Long] {
-        def expecting: String = "long"
+      def encodeValue(x: Int, out: JsonWriter): Unit = out.writeVal(x)
 
-        def decodeValue(cursor: Cursor, in: JsonReader): Long = in.readLong()
+      def decodeKey(in: JsonReader): Int = in.readKeyAsInt()
 
-        def encodeValue(x: Long, out: JsonWriter): Unit = out.writeVal(x)
+      def encodeKey(x: Int, out: JsonWriter): Unit = out.writeKey(x)
+    }
 
-        def decodeKey(in: JsonReader): Long = in.readKeyAsLong()
+    val long: JCodec[Long] = new NumericJCodec[Long] {
+      def expecting: String = "long"
 
-        def encodeKey(x: Long, out: JsonWriter): Unit = out.writeKey(x)
-      }
+      def decodeJsonNumber(cursor: Cursor, in: JsonReader): Long =
+        in.readLong()
 
-    private val efficientFloat: JCodec[Float] =
-      new JCodec[Float] {
-        def expecting: String = "float"
+      def decodeJsonString(cursor: Cursor, in: JsonReader): Long =
+        in.readStringAsLong()
 
-        def decodeValue(cursor: Cursor, in: JsonReader): Float = in.readFloat()
+      def encodeValue(x: Long, out: JsonWriter): Unit = out.writeVal(x)
 
-        def encodeValue(x: Float, out: JsonWriter): Unit = out.writeVal(x)
+      def decodeKey(in: JsonReader): Long = in.readKeyAsLong()
 
-        def decodeKey(in: JsonReader): Float = in.readKeyAsFloat()
+      def encodeKey(x: Long, out: JsonWriter): Unit = out.writeKey(x)
+    }
 
-        def encodeKey(x: Float, out: JsonWriter): Unit = out.writeKey(x)
-      }
+    private val efficientFloat: JCodec[Float] = new NumericJCodec[Float] {
+      def expecting: String = "float"
 
-    private val infinityAllowingFloat: JCodec[Float] = new JCodec[Float] {
-      val expecting: String = "JSON number for numeric values"
+      def decodeJsonNumber(cursor: Cursor, in: JsonReader): Float =
+        in.readFloat()
 
-      def decodeValue(cursor: Cursor, in: JsonReader): Float =
-        if (in.isNextToken('"')) {
-          in.rollbackToken()
+      def decodeJsonString(cursor: Cursor, in: JsonReader): Float =
+        in.readStringAsFloat()
+
+      def encodeValue(x: Float, out: JsonWriter): Unit = out.writeVal(x)
+
+      def decodeKey(in: JsonReader): Float = in.readKeyAsFloat()
+
+      def encodeKey(x: Float, out: JsonWriter): Unit = out.writeKey(x)
+    }
+
+    private val infinityAllowingFloat: JCodec[Float] =
+      new NumericJCodec[Float] {
+        val expecting: String = "JSON number for numeric values"
+
+        def decodeJsonString(cursor: Cursor, in: JsonReader): Float = {
+          in.setMark()
           val len = in.readStringAsCharBuf()
           if (in.isCharBufEqualsTo(len, "NaN")) Float.NaN
           else if (in.isCharBufEqualsTo(len, "Infinity")) Float.PositiveInfinity
           else if (in.isCharBufEqualsTo(len, "-Infinity"))
             Float.NegativeInfinity
-          else in.decodeError("illegal float")
-        } else {
-          in.rollbackToken()
+          else {
+            in.rollbackToMark()
+            in.readStringAsFloat()
+          }
+        }
+
+        def decodeJsonNumber(cursor: Cursor, in: JsonReader): Float = {
           in.readFloat()
         }
 
-      def encodeValue(f: Float, out: JsonWriter): Unit =
-        if (java.lang.Float.isFinite(f)) out.writeVal(f)
-        else
-          out.writeNonEscapedAsciiVal {
-            if (f != f) "NaN"
-            else if (f >= 0) "Infinity"
-            else "-Infinity"
-          }
+        def encodeValue(f: Float, out: JsonWriter): Unit =
+          if (java.lang.Float.isFinite(f)) out.writeVal(f)
+          else
+            out.writeNonEscapedAsciiVal {
+              if (f != f) "NaN"
+              else if (f >= 0) "Infinity"
+              else "-Infinity"
+            }
 
-      def decodeKey(in: JsonReader): Float = ???
+        def decodeKey(in: JsonReader): Float = ???
 
-      def encodeKey(x: Float, out: JsonWriter): Unit = ???
-    }
+        def encodeKey(x: Float, out: JsonWriter): Unit = ???
+      }
 
     val float: JCodec[Float] =
       if (infinitySupport) infinityAllowingFloat else efficientFloat
 
-    private val efficientDouble: JCodec[Double] =
-      new JCodec[Double] {
-        def expecting: String = "double"
+    private val efficientDouble: JCodec[Double] = new NumericJCodec[Double] {
+      def expecting: String = "double"
 
-        def decodeValue(cursor: Cursor, in: JsonReader): Double =
-          in.readDouble()
+      def decodeJsonNumber(cursor: Cursor, in: JsonReader): Double =
+        in.readDouble()
 
-        def encodeValue(x: Double, out: JsonWriter): Unit = out.writeVal(x)
+      def decodeJsonString(cursor: Cursor, in: JsonReader): Double =
+        in.readStringAsDouble()
 
-        def decodeKey(in: JsonReader): Double = in.readKeyAsDouble()
+      def encodeValue(x: Double, out: JsonWriter): Unit = out.writeVal(x)
 
-        def encodeKey(x: Double, out: JsonWriter): Unit = out.writeKey(x)
-      }
+      def decodeKey(in: JsonReader): Double = in.readKeyAsDouble()
+
+      def encodeKey(x: Double, out: JsonWriter): Unit = out.writeKey(x)
+    }
 
-    private val infinityAllowingDouble: JCodec[Double] = new JCodec[Double] {
-      val expecting: String = "JSON number for numeric values"
+    private val infinityAllowingDouble: JCodec[Double] =
+      new NumericJCodec[Double] {
+        val expecting: String = "JSON number for numeric values"
 
-      def decodeValue(cursor: Cursor, in: JsonReader): Double =
-        if (in.isNextToken('"')) {
-          in.rollbackToken()
+        def decodeJsonString(cursor: Cursor, in: JsonReader): Double = {
+          in.setMark()
           val len = in.readStringAsCharBuf()
           if (in.isCharBufEqualsTo(len, "NaN")) Double.NaN
           else if (in.isCharBufEqualsTo(len, "Infinity"))
             Double.PositiveInfinity
           else if (in.isCharBufEqualsTo(len, "-Infinity"))
             Double.NegativeInfinity
-          else in.decodeError("illegal double")
-        } else {
-          in.rollbackToken()
-          in.readDouble()
+          else {
+            in.rollbackToMark()
+            in.readStringAsDouble()
+          }
         }
 
-      def encodeValue(d: Double, out: JsonWriter): Unit =
-        if (java.lang.Double.isFinite(d)) out.writeVal(d)
-        else
-          out.writeNonEscapedAsciiVal {
-            if (d != d) "NaN"
-            else if (d >= 0) "Infinity"
-            else "-Infinity"
-          }
+        def decodeJsonNumber(cursor: Cursor, in: JsonReader): Double =
+          in.readDouble()
 
-      def decodeKey(in: JsonReader): Double = ???
+        def encodeValue(d: Double, out: JsonWriter): Unit =
+          if (java.lang.Double.isFinite(d)) out.writeVal(d)
+          else
+            out.writeNonEscapedAsciiVal {
+              if (d != d) "NaN"
+              else if (d >= 0) "Infinity"
+              else "-Infinity"
+            }
 
-      def encodeKey(x: Double, out: JsonWriter): Unit = ???
-    }
+        def decodeKey(in: JsonReader): Double = ???
+
+        def encodeKey(x: Double, out: JsonWriter): Unit = ???
+      }
 
     val double: JCodec[Double] =
       if (infinitySupport) infinityAllowingDouble else efficientDouble
 
-    val short: JCodec[Short] =
-      new JCodec[Short] {
-        def expecting: String = "short"
+    val short: JCodec[Short] = new NumericJCodec[Short] {
+      def expecting: String = "short"
 
-        def decodeValue(cursor: Cursor, in: JsonReader): Short = in.readShort()
+      def decodeJsonNumber(cursor: Cursor, in: JsonReader): Short =
+        in.readShort()
 
-        def encodeValue(x: Short, out: JsonWriter): Unit = out.writeVal(x)
+      def decodeJsonString(cursor: Cursor, in: JsonReader): Short =
+        in.readStringAsShort()
 
-        def decodeKey(in: JsonReader): Short = in.readKeyAsShort()
+      def encodeValue(x: Short, out: JsonWriter): Unit = out.writeVal(x)
 
-        def encodeKey(x: Short, out: JsonWriter): Unit = out.writeKey(x)
-      }
+      def decodeKey(in: JsonReader): Short = in.readKeyAsShort()
 
-    val byte: JCodec[Byte] =
-      new JCodec[Byte] {
-        def expecting: String = "byte"
+      def encodeKey(x: Short, out: JsonWriter): Unit = out.writeKey(x)
+    }
 
-        def decodeValue(cursor: Cursor, in: JsonReader): Byte = in.readByte()
+    val byte: JCodec[Byte] = new NumericJCodec[Byte] {
+      def expecting: String = "byte"
 
-        def encodeValue(x: Byte, out: JsonWriter): Unit = out.writeVal(x)
+      def decodeJsonNumber(cursor: Cursor, in: JsonReader): Byte = in.readByte()
 
-        def decodeKey(in: JsonReader): Byte = in.readKeyAsByte()
+      def decodeJsonString(cursor: Cursor, in: JsonReader): Byte = in.readByte()
 
-        def encodeKey(x: Byte, out: JsonWriter): Unit = out.writeKey(x)
-      }
+      def encodeValue(x: Byte, out: JsonWriter): Unit = out.writeVal(x)
+
+      def decodeKey(in: JsonReader): Byte = in.readKeyAsByte()
+
+      def encodeKey(x: Byte, out: JsonWriter): Unit = out.writeKey(x)
+    }
 
     val bytes: JCodec[Blob] =
       new JCodec[Blob] {
diff --git a/modules/json/test/src/smithy4s/json/SchemaVisitorJCodecCustomisationTests.scala b/modules/json/test/src/smithy4s/json/SchemaVisitorJCodecCustomisationTests.scala
index 398615baf..c0d9ac9f0 100644
--- a/modules/json/test/src/smithy4s/json/SchemaVisitorJCodecCustomisationTests.scala
+++ b/modules/json/test/src/smithy4s/json/SchemaVisitorJCodecCustomisationTests.scala
@@ -24,6 +24,30 @@ import munit._
 
 class SchemaVisitorJCodecCustomisationTests extends FunSuite {
 
+  case class FooInt(i: Int)
+  object FooInt {
+    implicit val schema: Schema[FooInt] = {
+      val i = int.required[FooInt]("i", _.i)
+      struct(i)(FooInt.apply)
+    }
+  }
+
+  case class FooShort(s: Short)
+  object FooShort {
+    implicit val schema: Schema[FooShort] = {
+      val s = short.required[FooShort]("s", _.s)
+      struct(s)(FooShort.apply)
+    }
+  }
+
+  case class FooLong(l: Long)
+  object FooLong {
+    implicit val schema: Schema[FooLong] = {
+      val s = long.required[FooLong]("l", _.l)
+      struct(s)(FooLong.apply)
+    }
+  }
+
   case class FooDouble(d: Double)
   object FooDouble {
     implicit val schema: Schema[FooDouble] = {
@@ -178,4 +202,39 @@ class SchemaVisitorJCodecCustomisationTests extends FunSuite {
 
     expect(result.f.isNegInfinity)
   }
+
+  test("decoding JSON string as a Float") {
+    val input = """{"f" : "1.1" }"""
+    val result = readFromString[FooFloat](input)
+
+    expect.eql(result.f, 1.1f)
+  }
+
+  test("decoding JSON string as a Double") {
+    val input = """{"d" : "1.1" }"""
+    val result = readFromString[FooDouble](input)
+
+    expect.eql(result.d, 1.1d)
+  }
+
+  test("decoding JSON string as an Int") {
+    val input = """{"i" : "1" }"""
+    val result = readFromString[FooInt](input)
+
+    expect.eql(result.i, 1)
+  }
+
+  test("decoding JSON string as a Long") {
+    val input = """{"l" : "1" }"""
+    val result = readFromString[FooLong](input)
+
+    expect.eql(result.l, 1L)
+  }
+
+  test("decoding JSON string as a Short") {
+    val input = """{"s" : "1" }"""
+    val result = readFromString[FooShort](input)
+
+    expect.eql(result.s, 1.toShort)
+  }
 }
diff --git a/sampleSpecs/reservedNamespace.smithy b/sampleSpecs/reservedNamespace.smithy
index af20e2088..d263b1488 100644
--- a/sampleSpecs/reservedNamespace.smithy
+++ b/sampleSpecs/reservedNamespace.smithy
@@ -3,3 +3,6 @@ $version: "2.0"
 namespace smithy4s.example.package
 
 string MyPackageString
+
+@trait
+string MyPackageStringTrait
diff --git a/sampleSpecs/reservednames.smithy b/sampleSpecs/reservednames.smithy
index 9991f479d..ec39da06c 100644
--- a/sampleSpecs/reservednames.smithy
+++ b/sampleSpecs/reservednames.smithy
@@ -4,6 +4,7 @@ namespace smithy4s.example.collision
 
 use alloy#simpleRestJson
 use smithy4s.example.package#MyPackageString
+use smithy4s.example.package#MyPackageStringTrait
 
 @simpleRestJson
 service ReservedNameService {
@@ -67,6 +68,10 @@ structure TestReservedNamespaceImport {
     package: MyPackageString
 }
 
+// Regression test for https://github.com/disneystreaming/smithy4s/issues/1601
+@MyPackageStringTrait("test")
+string TestReservedNamespaceTrait
+
 // trait def
 @trait
 structure reservedKeywordStructTrait {
@@ -146,3 +151,17 @@ structure Scala3ReservedKeywords {
     export: String
     enum: String
 }
+
+@smithy4s.meta#adt
+@trait
+union class {
+    package: AdtStruct
+}
+
+structure AdtStruct {}
+
+// Regression test for https://github.com/disneystreaming/smithy4s/issues/1601
+@class(package: {
+
+})
+string ReservedNameUnionTrait