diff --git a/build.sc b/build.sc
index b9567485..6116206b 100644
--- a/build.sc
+++ b/build.sc
@@ -84,33 +84,18 @@ object core extends Module {
       annotations.jvm(),
       util.jvm()
     )
-
-    object test extends Tests with TestCrossSources {
-      def ivyDeps       = Agg(Deps.utest)
-      def testFramework = "utest.runner.Framework"
-    }
   }
   trait CoreJs extends Core with CaseAppScalaJsModule with MimaChecks {
     def moduleDeps = Seq(
       annotations.js(),
       util.js()
     )
-
-    object test extends SbtModuleTests with ScalaJSTests with TestCrossSources {
-      def ivyDeps       = Agg(Deps.utest)
-      def testFramework = "utest.runner.Framework"
-    }
   }
   trait CoreNative extends Core with CaseAppScalaNativeModule {
     def moduleDeps = Seq(
       annotations.native(),
       util.native()
     )
-
-    object test extends SbtModuleTests with ScalaNativeTests with TestCrossSources {
-      def ivyDeps       = Agg(Deps.utest)
-      def testFramework = "utest.runner.Framework"
-    }
   }
 
   trait Core extends CrossSbtModule with CrossSources with CaseAppPublishModule {
@@ -171,7 +156,7 @@ object cats2 extends Module {
 
   trait Cats2Jvm extends Cats2 with MimaChecks {
     def moduleDeps = Seq(core.jvm())
-    def sources    = cats.jvm().sources()
+    def sources    = T.sources(cats.jvm().sources())
 
     object test extends Tests with TestCrossSources {
       def ivyDeps       = Agg(Deps.utest)
@@ -180,7 +165,7 @@ object cats2 extends Module {
   }
   trait Cats2Js extends Cats2 with CaseAppScalaJsModule with MimaChecks {
     def moduleDeps = Seq(core.js())
-    def sources    = cats.js().sources()
+    def sources    = T.sources(cats.js().sources())
 
     object test extends SbtModuleTests with ScalaJSTests with TestCrossSources {
       def ivyDeps       = Agg(Deps.utest)
diff --git a/cats/shared/src/main/scala/caseapp/cats/IOCaseApp.scala b/cats/shared/src/main/scala/caseapp/catseffect/IOCaseApp.scala
similarity index 99%
rename from cats/shared/src/main/scala/caseapp/cats/IOCaseApp.scala
rename to cats/shared/src/main/scala/caseapp/catseffect/IOCaseApp.scala
index 0916e145..91e265f3 100644
--- a/cats/shared/src/main/scala/caseapp/cats/IOCaseApp.scala
+++ b/cats/shared/src/main/scala/caseapp/catseffect/IOCaseApp.scala
@@ -1,4 +1,4 @@
-package caseapp.cats
+package caseapp.catseffect
 
 import caseapp.core.Error
 import caseapp.core.help.{Help, WithHelp}
diff --git a/cats/shared/src/main/scala/caseapp/cats/CatsArgParser.scala b/cats/shared/src/main/scala/caseapp/catseffect/package.scala
similarity index 91%
rename from cats/shared/src/main/scala/caseapp/cats/CatsArgParser.scala
rename to cats/shared/src/main/scala/caseapp/catseffect/package.scala
index 25aa6c86..8292cec3 100644
--- a/cats/shared/src/main/scala/caseapp/cats/CatsArgParser.scala
+++ b/cats/shared/src/main/scala/caseapp/catseffect/package.scala
@@ -1,9 +1,9 @@
-package caseapp.cats
+package caseapp
 
 import caseapp.core.argparser.{AccumulatorArgParser, ArgParser}
 import cats.data.NonEmptyList
 
-object CatsArgParser {
+package object catseffect {
   implicit def nonEmptyListArgParser[T](
     implicit parser: ArgParser[T]
   ): AccumulatorArgParser[NonEmptyList[T]] =
diff --git a/cats/shared/src/test/scala/caseapp/cats/CatsTests.scala b/cats/shared/src/test/scala/caseapp/catseffect/CatsTests.scala
similarity index 93%
rename from cats/shared/src/test/scala/caseapp/cats/CatsTests.scala
rename to cats/shared/src/test/scala/caseapp/catseffect/CatsTests.scala
index b28af382..aef5cbff 100644
--- a/cats/shared/src/test/scala/caseapp/cats/CatsTests.scala
+++ b/cats/shared/src/test/scala/caseapp/catseffect/CatsTests.scala
@@ -1,15 +1,13 @@
-package caseapp.cats
+package caseapp.catseffect
 
-import _root_.cats.effect._
-import _root_.cats.effect.unsafe.implicits.global
-import _root_.cats.data.NonEmptyList
+import cats.effect._
+import cats.effect.unsafe.implicits.global
+import cats.data.NonEmptyList
 import caseapp._
 import caseapp.core.help.Help
 import caseapp.core.Error
 import utest._
 
-import caseapp.cats.CatsArgParser._
-
 sealed trait RecordedApp {
 
   val stdoutBuff: Ref[IO, List[String]] = Ref.unsafe(List.empty)
diff --git a/cats2/shared/src/test/scala/caseapp/cats/Definitions.scala b/cats/shared/src/test/scala/caseapp/catseffect/Definitions.scala
similarity index 90%
rename from cats2/shared/src/test/scala/caseapp/cats/Definitions.scala
rename to cats/shared/src/test/scala/caseapp/catseffect/Definitions.scala
index 76d66487..3fa1e175 100644
--- a/cats2/shared/src/test/scala/caseapp/cats/Definitions.scala
+++ b/cats/shared/src/test/scala/caseapp/catseffect/Definitions.scala
@@ -1,7 +1,7 @@
 package caseapp
-package cats
+package catseffect
 
-import _root_.cats.data.NonEmptyList
+import cats.data.NonEmptyList
 
 object Definitions {
 
diff --git a/cats2/shared/src/test/scala/caseapp/cats/CatsTests.scala b/cats2/shared/src/test/scala/caseapp/catseffect/CatsTests.scala
similarity index 92%
rename from cats2/shared/src/test/scala/caseapp/cats/CatsTests.scala
rename to cats2/shared/src/test/scala/caseapp/catseffect/CatsTests.scala
index d6a654c0..bb05316b 100644
--- a/cats2/shared/src/test/scala/caseapp/cats/CatsTests.scala
+++ b/cats2/shared/src/test/scala/caseapp/catseffect/CatsTests.scala
@@ -1,16 +1,14 @@
-package caseapp.cats
+package caseapp.catseffect
 
-import _root_.cats.effect._
-import _root_.cats.effect.concurrent.Ref
-import _root_.cats.implicits._
-import _root_.cats.data.NonEmptyList
+import cats.effect._
+import cats.effect.concurrent.Ref
+import cats.implicits._
+import cats.data.NonEmptyList
 import caseapp._
 import caseapp.core.help.Help
 import caseapp.core.Error
 import utest._
 
-import caseapp.cats.CatsArgParser._
-
 sealed trait RecordedApp {
 
   val stdoutBuff: Ref[IO, List[String]] = Ref.unsafe(List.empty)
diff --git a/cats/shared/src/test/scala/caseapp/cats/Definitions.scala b/cats2/shared/src/test/scala/caseapp/catseffect/Definitions.scala
similarity index 90%
rename from cats/shared/src/test/scala/caseapp/cats/Definitions.scala
rename to cats2/shared/src/test/scala/caseapp/catseffect/Definitions.scala
index 76d66487..3fa1e175 100644
--- a/cats/shared/src/test/scala/caseapp/cats/Definitions.scala
+++ b/cats2/shared/src/test/scala/caseapp/catseffect/Definitions.scala
@@ -1,7 +1,7 @@
 package caseapp
-package cats
+package catseffect
 
-import _root_.cats.data.NonEmptyList
+import cats.data.NonEmptyList
 
 object Definitions {
 
diff --git a/core/jvm/src/main/scala/caseapp/core/app/PlatformCommandsMethods.scala b/core/jvm/src/main/scala/caseapp/core/app/PlatformCommandsMethods.scala
index a49662c5..06dbda63 100644
--- a/core/jvm/src/main/scala/caseapp/core/app/PlatformCommandsMethods.scala
+++ b/core/jvm/src/main/scala/caseapp/core/app/PlatformCommandsMethods.scala
@@ -1,6 +1,12 @@
 package caseapp.core.app
 
-import caseapp.core.complete.{Bash, Fish, Zsh}
+import caseapp.core.complete.{
+  Bash,
+  CompletionsInstallOptions,
+  CompletionsUninstallOptions,
+  Fish,
+  Zsh
+}
 
 import java.io.File
 import java.nio.charset.{Charset, StandardCharsets}
@@ -21,7 +27,7 @@ trait PlatformCommandsMethods { self: CommandsEntryPoint =>
 
   // Adapted from https://github.com/VirtusLab/scala-cli/blob/eced0b35c769eca58ae6f1b1a3be0f29a8700859/modules/cli/src/main/scala/scala/cli/commands/installcompletions/InstallCompletions.scala
   def completionsInstall(completionsWorkingDirectory: String, args: Seq[String]): Unit = {
-    val (options, rem) = CaseApp.process[PlatformCommandsMethods.CompletionsInstallOptions](args)
+    val (options, rem) = CaseApp.process[CompletionsInstallOptions](args)
 
     lazy val completionsDir = Paths.get(options.output.getOrElse(completionsWorkingDirectory))
 
@@ -128,7 +134,7 @@ trait PlatformCommandsMethods { self: CommandsEntryPoint =>
   }
 
   def completionsUninstall(completionsWorkingDirectory: String, args: Seq[String]): Unit = {
-    val (options, rem) = CaseApp.process[PlatformCommandsMethods.CompletionsUninstallOptions](args)
+    val (options, rem) = CaseApp.process[CompletionsUninstallOptions](args)
 
     val name = options.name.getOrElse(Paths.get(progName).getFileName.toString)
 
@@ -164,55 +170,6 @@ trait PlatformCommandsMethods { self: CommandsEntryPoint =>
 }
 
 object PlatformCommandsMethods {
-  import caseapp.{HelpMessage, Name}
-  import caseapp.core.help.Help
-  import caseapp.core.parser.Parser
-
-  // from https://github.com/VirtusLab/scala-cli/blob/eced0b35c769eca58ae6f1b1a3be0f29a8700859/modules/cli/src/main/scala/scala/cli/commands/installcompletions/InstallCompletionsOptions.scala
-  // format: off
-  final case class CompletionsInstallOptions(
-    @HelpMessage("Print completions to stdout")
-      env: Boolean = false,
-    @HelpMessage("Custom completions name")
-      name: Option[String] = None,
-    @HelpMessage("Name of the shell, either zsh, fish or bash")
-    @Name("shell")
-      format: Option[String] = None,
-    @HelpMessage("Completions output directory (defaults to $XDG_CONFIG_HOME/fish/completions on fish)")
-    @Name("o")
-      output: Option[String] = None,
-    @HelpMessage("Custom banner in comment placed in rc file (bash or zsh only)")
-      banner: String = "{NAME} completions",
-    @HelpMessage("Path to `*rc` file, defaults to `.bashrc` or `.zshrc` depending on shell (bash or zsh only)")
-      rcFile: Option[String] = None
-  )
-  // format: on
-
-  object CompletionsInstallOptions {
-    implicit lazy val parser: Parser[CompletionsInstallOptions] = Parser.derive
-    implicit lazy val help: Help[CompletionsInstallOptions]     = Help.derive
-  }
-
-  // from https://github.com/VirtusLab/scala-cli/blob/eced0b35c769eca58ae6f1b1a3be0f29a8700859/modules/cli/src/main/scala/scala/cli/commands/uninstallcompletions/SharedUninstallCompletionsOptions.scala
-  // format: off
-  final case class CompletionsUninstallOptions(
-    @HelpMessage("Path to `*rc` file, defaults to `.bashrc` or `.zshrc` depending on shell (bash or zsh only)")
-      rcFile: Option[String] = None,
-    @HelpMessage("Custom banner in comment placed in rc file")
-      banner: String = "{NAME} completions",
-    @HelpMessage("Custom completions name")
-      name: Option[String] = None,
-    @HelpMessage("Completions output directory (defaults to $XDG_CONFIG_HOME/fish/completions on fish)")
-    @Name("o")
-      output: Option[String] = None,
-  )
-  // format: on
-
-  object CompletionsUninstallOptions {
-    implicit lazy val parser: Parser[CompletionsUninstallOptions] = Parser.derive
-    implicit lazy val help: Help[CompletionsUninstallOptions]     = Help.derive
-  }
-
   def getFormat(format: Option[String]): Option[String] =
     format.map(_.trim).filter(_.nonEmpty)
       .orElse {
diff --git a/core/shared/src/main/scala-2/caseapp/core/help/HelpCompanion.scala b/core/shared/src/main/scala-2/caseapp/core/help/HelpCompanion.scala
index b2b0a229..dce43678 100644
--- a/core/shared/src/main/scala-2/caseapp/core/help/HelpCompanion.scala
+++ b/core/shared/src/main/scala-2/caseapp/core/help/HelpCompanion.scala
@@ -41,7 +41,13 @@ abstract class HelpCompanion {
     helpMessage: AnnotationOption[HelpMessage, T]
   ): Help[T] = {
 
-    val appName0 = appName().fold(typeable.describe.stripSuffix("Options"))(_.appName)
+    val appName0 = appName() match {
+      case None =>
+        if (typeable.describe == "Options") typeable.describe
+        else typeable.describe.stripSuffix("Options")
+      case Some(name) =>
+        name.appName
+    }
 
     Help(
       parser.args,
diff --git a/core/shared/src/main/scala/caseapp/core/Arg.scala b/core/shared/src/main/scala/caseapp/core/Arg.scala
index 0c99ef7b..28da64d7 100644
--- a/core/shared/src/main/scala/caseapp/core/Arg.scala
+++ b/core/shared/src/main/scala/caseapp/core/Arg.scala
@@ -36,6 +36,7 @@ import dataclass._
   def withDefaultOrigin(defaultOrigin: String): Arg =
     if (origin.isEmpty) this.withOrigin(Some(defaultOrigin))
     else this
+  lazy val names = name +: extraNames
 }
 
 object Arg {
diff --git a/core/shared/src/main/scala/caseapp/core/RemainingArgs.scala b/core/shared/src/main/scala/caseapp/core/RemainingArgs.scala
index d0a65e18..199d5dae 100644
--- a/core/shared/src/main/scala/caseapp/core/RemainingArgs.scala
+++ b/core/shared/src/main/scala/caseapp/core/RemainingArgs.scala
@@ -14,13 +14,16 @@ import dataclass.data
   indexedUnparsed: Seq[Indexed[String]]
 ) {
 
-  def remaining: Seq[String] = indexedRemaining.map(_.value)
-  def unparsed: Seq[String]  = indexedUnparsed.map(_.value)
+  lazy val remaining: Seq[String] = indexedRemaining.map(_.value)
+  lazy val unparsed: Seq[String]  = indexedUnparsed.map(_.value)
 
   /** Arguments both before and after a `--`.
     *
     * The first `--`, if any, is not included in this list.
     */
-  def all: Seq[String] =
+  lazy val all: Seq[String] =
     remaining ++ unparsed
+
+  lazy val indexed: Seq[Indexed[String]] =
+    indexedRemaining ++ indexedUnparsed
 }
diff --git a/core/shared/src/main/scala/caseapp/core/app/CaseApp.scala b/core/shared/src/main/scala/caseapp/core/app/CaseApp.scala
index 1ddbcc6e..9c17cc55 100644
--- a/core/shared/src/main/scala/caseapp/core/app/CaseApp.scala
+++ b/core/shared/src/main/scala/caseapp/core/app/CaseApp.scala
@@ -10,9 +10,14 @@ import caseapp.core.util.Formatter
 
 abstract class CaseApp[T](implicit val parser0: Parser[T], val messages: Help[T]) {
 
+  def name: String =
+    help.progName
+
   def hasHelp: Boolean     = true
   def hasFullHelp: Boolean = false
 
+  def help: Help[T] = messages
+
   def parser: Parser[T] = {
     val p = parser0.nameFormatter(nameFormatter)
     if (ignoreUnrecognized)
@@ -69,10 +74,14 @@ abstract class CaseApp[T](implicit val parser0: Parser[T], val messages: Help[T]
     exit(1)
   }
 
-  lazy val finalHelp: Help[_] =
-    if (hasFullHelp) messages.withFullHelp
-    else if (hasHelp) messages.withHelp
-    else messages
+  lazy val finalHelp: Help[_] = {
+    val h =
+      if (hasFullHelp) messages.withFullHelp
+      else if (hasHelp) messages.withHelp
+      else messages
+    if (name == h.progName) h
+    else h.withProgName(name)
+  }
 
   def fullHelpAsked(progName: String): Nothing = {
     val help = if (progName.isEmpty) finalHelp else finalHelp.withProgName(progName)
diff --git a/core/shared/src/main/scala/caseapp/core/app/Command.scala b/core/shared/src/main/scala/caseapp/core/app/Command.scala
index e3766ce7..e85844f4 100644
--- a/core/shared/src/main/scala/caseapp/core/app/Command.scala
+++ b/core/shared/src/main/scala/caseapp/core/app/Command.scala
@@ -7,8 +7,6 @@ abstract class Command[T](implicit parser: Parser[T], help: Help[T])
     extends CaseApp()(parser, help) {
   def names: List[List[String]] =
     List(List(name))
-  def name: String =
-    help.progName
   def group: String   = ""
   def hidden: Boolean = false
 }
diff --git a/core/shared/src/main/scala/caseapp/core/app/CommandsEntryPoint.scala b/core/shared/src/main/scala/caseapp/core/app/CommandsEntryPoint.scala
index 41c9df8e..d3336ef2 100644
--- a/core/shared/src/main/scala/caseapp/core/app/CommandsEntryPoint.scala
+++ b/core/shared/src/main/scala/caseapp/core/app/CommandsEntryPoint.scala
@@ -48,6 +48,28 @@ abstract class CommandsEntryPoint extends PlatformCommandsMethods {
     printLine("", toStderr = true)
   }
 
+  def completePrintInstructions(toStderr: Boolean): Unit = {
+    val formats = Seq(Bash.id, Zsh.id, Fish.id)
+    printLine("To manually get completions, run", toStderr = toStderr)
+    printLine("", toStderr = toStderr)
+    printLine(
+      s"  $progName ${completeCommandName.mkString(" ")} ${formats.mkString("|")} index command...",
+      toStderr = toStderr
+    )
+    printLine("", toStderr = toStderr)
+    printLine(
+      "where index starts from one, and command... includes the command name, like",
+      toStderr = toStderr
+    )
+    printLine("", toStderr = toStderr)
+    printLine(
+      s"  $progName ${completeCommandName.mkString(" ")} ${Zsh.id} 2 $progName --",
+      toStderr = toStderr
+    )
+    printLine("", toStderr = toStderr)
+    printLine("to get completions for '--'", toStderr = toStderr)
+  }
+
   def completionsPrintUsage(): Nothing = {
     completionsPrintInstructions()
     exit(1)
@@ -58,11 +80,6 @@ abstract class CommandsEntryPoint extends PlatformCommandsMethods {
     exit(1)
   }
 
-  def completePrintUsage(): Nothing = {
-    completionsPrintInstructions()
-    exit(1)
-  }
-
   def completionsWorkingDirectory: Option[String] = None
 
   def completionsMain(args: Array[String]): Unit = {
@@ -122,8 +139,11 @@ abstract class CommandsEntryPoint extends PlatformCommandsMethods {
           case _ =>
             completeUnrecognizedFormat(format)
         }
+      case Array("--help" | "--usage" | "-h") =>
+        completePrintInstructions(toStderr = false)
       case _ =>
-        completePrintUsage()
+        completePrintInstructions(toStderr = true)
+        exit(1)
     }
   }
 
diff --git a/core/shared/src/main/scala/caseapp/core/argparser/ArgParser.scala b/core/shared/src/main/scala/caseapp/core/argparser/ArgParser.scala
index efd6bf4d..e7515df1 100644
--- a/core/shared/src/main/scala/caseapp/core/argparser/ArgParser.scala
+++ b/core/shared/src/main/scala/caseapp/core/argparser/ArgParser.scala
@@ -86,6 +86,12 @@ object ArgParser extends PlatformArgParsers {
   /** Look for an implicit `ArgParser[T]` */
   def apply[T](implicit parser: ArgParser[T]): ArgParser[T] = parser
 
+  implicit def byte: ArgParser[Byte] =
+    SimpleArgParser.byte
+
+  implicit def short: ArgParser[Short] =
+    SimpleArgParser.short
+
   implicit def int: ArgParser[Int] =
     SimpleArgParser.int
 
diff --git a/core/shared/src/main/scala/caseapp/core/argparser/SimpleArgParser.scala b/core/shared/src/main/scala/caseapp/core/argparser/SimpleArgParser.scala
index 071af8a3..6f48d1f8 100644
--- a/core/shared/src/main/scala/caseapp/core/argparser/SimpleArgParser.scala
+++ b/core/shared/src/main/scala/caseapp/core/argparser/SimpleArgParser.scala
@@ -23,6 +23,24 @@ object SimpleArgParser {
   def from[T](description: String)(parse: String => Either[Error, T]): SimpleArgParser[T] =
     SimpleArgParser(description, (value, _, _) => parse(value))
 
+  val byte: SimpleArgParser[Byte] =
+    from("byte") { s =>
+      try Right(s.toByte)
+      catch {
+        case _: NumberFormatException =>
+          Left(Error.MalformedValue("byte-sized integer", s))
+      }
+    }
+
+  val short: SimpleArgParser[Short] =
+    from("short") { s =>
+      try Right(s.toShort)
+      catch {
+        case _: NumberFormatException =>
+          Left(Error.MalformedValue("short integer", s))
+      }
+    }
+
   val int: SimpleArgParser[Int] =
     from("int") { s =>
       try Right(s.toInt)
diff --git a/core/shared/src/main/scala/caseapp/core/commandparser/RuntimeCommandParser.scala b/core/shared/src/main/scala/caseapp/core/commandparser/RuntimeCommandParser.scala
index 0178f4c5..f258ab8a 100644
--- a/core/shared/src/main/scala/caseapp/core/commandparser/RuntimeCommandParser.scala
+++ b/core/shared/src/main/scala/caseapp/core/commandparser/RuntimeCommandParser.scala
@@ -8,19 +8,19 @@ import caseapp.core.complete.CompletionItem
 
 object RuntimeCommandParser {
 
-  def parse(
-    apps: Map[List[String], CaseApp[_]],
+  def parse[T](
+    apps: Map[List[String], T],
     args: List[String]
-  ): Option[(List[String], CaseApp[_], List[String])] = {
+  ): Option[(List[String], T, List[String])] = {
     val tree = CommandTree.fromCommandMap(apps)
     tree.command(args)
   }
 
-  def parse(
-    defaultApp: CaseApp[_],
-    apps: Map[List[String], CaseApp[_]],
+  def parse[T](
+    defaultApp: T,
+    apps: Map[List[String], T],
     args: List[String]
-  ): (List[String], CaseApp[_], List[String]) = {
+  ): (List[String], T, List[String]) = {
     val tree = CommandTree.fromCommandMap(apps)
     tree.command(args).getOrElse((Nil, defaultApp, args))
   }
diff --git a/core/shared/src/main/scala/caseapp/core/complete/Completer.scala b/core/shared/src/main/scala/caseapp/core/complete/Completer.scala
index 709e30f9..200a1b8b 100644
--- a/core/shared/src/main/scala/caseapp/core/complete/Completer.scala
+++ b/core/shared/src/main/scala/caseapp/core/complete/Completer.scala
@@ -16,25 +16,83 @@ trait Completer[-T] { self =>
   def postDoubleDash(state: Option[T], args: RemainingArgs): Option[Completer[T]] =
     None
 
-  def contramapOpt[U](f: U => Option[T]): Completer[U] =
-    new Completer[U] {
-      def optionName(prefix: String, state: Option[U], args: RemainingArgs): List[CompletionItem] =
-        self.optionName(prefix, state.flatMap(f), args)
-      def optionValue(
-        arg: Arg,
-        prefix: String,
-        state: Option[U],
-        args: RemainingArgs
-      ): List[CompletionItem] =
-        self.optionValue(arg, prefix, state.flatMap(f), args)
-      def argument(prefix: String, state: Option[U], args: RemainingArgs): List[CompletionItem] =
-        self.argument(prefix, state.flatMap(f), args)
-
-      override def postDoubleDash(state: Option[U], args: RemainingArgs): Option[Completer[U]] =
-        self.postDoubleDash(state.flatMap(f), args).map(_.contramapOpt(f))
-    }
-  def withHelp: Completer[WithHelp[T]] =
+  final def contramapOpt[U](f: U => Option[T]): Completer[U] =
+    Completer.Mapped(this, f)
+  final def withHelp: Completer[WithHelp[T]] =
     contramapOpt(_.baseOrError.toOption)
-  def withFullHelp: Completer[WithFullHelp[T]] =
+  final def withFullHelp: Completer[WithFullHelp[T]] =
     contramapOpt(_.withHelp.baseOrError.toOption)
 }
+
+object Completer {
+
+  implicit class CompleterOps[T](private val completer: Completer[T]) extends AnyVal {
+    def completeOptionValue(f: (
+      Arg,
+      String,
+      Option[T],
+      RemainingArgs
+    ) => Option[List[CompletionItem]]): Completer[T] =
+      WithOptionValue(completer, f)
+  }
+
+  class DefaultTo[-T](default: Completer[T]) extends Completer[T] {
+    override def optionName(
+      prefix: String,
+      state: Option[T],
+      args: RemainingArgs
+    ): List[CompletionItem] =
+      default.optionName(prefix, state, args)
+    override def optionValue(
+      arg: Arg,
+      prefix: String,
+      state: Option[T],
+      args: RemainingArgs
+    ): List[CompletionItem] =
+      default.optionValue(arg, prefix, state, args)
+    override def argument(
+      prefix: String,
+      state: Option[T],
+      args: RemainingArgs
+    ): List[CompletionItem] =
+      default.argument(prefix, state, args)
+    override def postDoubleDash(state: Option[T], args: RemainingArgs): Option[Completer[T]] =
+      default.postDoubleDash(state, args)
+
+    override def toString(): String =
+      s"Completer.DefaultTo($default)"
+  }
+
+  private final case class WithOptionValue[T](
+    self: Completer[T],
+    f: (Arg, String, Option[T], RemainingArgs) => Option[List[CompletionItem]]
+  ) extends DefaultTo[T](self) {
+    override def optionValue(
+      arg: Arg,
+      prefix: String,
+      state: Option[T],
+      args: RemainingArgs
+    ): List[CompletionItem] =
+      f(arg, prefix, state, args).getOrElse {
+        super.optionValue(arg, prefix, state, args)
+      }
+  }
+
+  private final case class Mapped[T, U](self: Completer[T], f: U => Option[T])
+      extends Completer[U] {
+    def optionName(prefix: String, state: Option[U], args: RemainingArgs): List[CompletionItem] =
+      self.optionName(prefix, state.flatMap(f), args)
+    def optionValue(
+      arg: Arg,
+      prefix: String,
+      state: Option[U],
+      args: RemainingArgs
+    ): List[CompletionItem] =
+      self.optionValue(arg, prefix, state.flatMap(f), args)
+    def argument(prefix: String, state: Option[U], args: RemainingArgs): List[CompletionItem] =
+      self.argument(prefix, state.flatMap(f), args)
+
+    override def postDoubleDash(state: Option[U], args: RemainingArgs): Option[Completer[U]] =
+      self.postDoubleDash(state.flatMap(f), args).map(_.contramapOpt(f))
+  }
+}
diff --git a/core/shared/src/main/scala/caseapp/core/complete/CompletionsInstallOptions.scala b/core/shared/src/main/scala/caseapp/core/complete/CompletionsInstallOptions.scala
new file mode 100644
index 00000000..d3227fa7
--- /dev/null
+++ b/core/shared/src/main/scala/caseapp/core/complete/CompletionsInstallOptions.scala
@@ -0,0 +1,30 @@
+package caseapp.core.complete
+
+import caseapp.{HelpMessage, Name}
+import caseapp.core.help.Help
+import caseapp.core.parser.Parser
+
+// from https://github.com/VirtusLab/scala-cli/blob/eced0b35c769eca58ae6f1b1a3be0f29a8700859/modules/cli/src/main/scala/scala/cli/commands/installcompletions/InstallCompletionsOptions.scala
+// format: off
+final case class CompletionsInstallOptions(
+  @HelpMessage("Print completions to stdout")
+    env: Boolean = false,
+  @HelpMessage("Custom completions name")
+    name: Option[String] = None,
+  @HelpMessage("Name of the shell, either zsh, fish or bash")
+  @Name("shell")
+    format: Option[String] = None,
+  @HelpMessage("Completions output directory (defaults to $XDG_CONFIG_HOME/fish/completions on fish)")
+  @Name("o")
+    output: Option[String] = None,
+  @HelpMessage("Custom banner in comment placed in rc file (bash or zsh only)")
+    banner: String = "{NAME} completions",
+  @HelpMessage("Path to `*rc` file, defaults to `.bashrc` or `.zshrc` depending on shell (bash or zsh only)")
+    rcFile: Option[String] = None
+)
+// format: on
+
+object CompletionsInstallOptions {
+  implicit lazy val parser: Parser[CompletionsInstallOptions] = Parser.derive
+  implicit lazy val help: Help[CompletionsInstallOptions]     = Help.derive
+}
diff --git a/core/shared/src/main/scala/caseapp/core/complete/CompletionsUninstallOptions.scala b/core/shared/src/main/scala/caseapp/core/complete/CompletionsUninstallOptions.scala
new file mode 100644
index 00000000..6d12237b
--- /dev/null
+++ b/core/shared/src/main/scala/caseapp/core/complete/CompletionsUninstallOptions.scala
@@ -0,0 +1,25 @@
+package caseapp.core.complete
+
+import caseapp.{HelpMessage, Name}
+import caseapp.core.help.Help
+import caseapp.core.parser.Parser
+
+// from https://github.com/VirtusLab/scala-cli/blob/eced0b35c769eca58ae6f1b1a3be0f29a8700859/modules/cli/src/main/scala/scala/cli/commands/uninstallcompletions/SharedUninstallCompletionsOptions.scala
+// format: off
+final case class CompletionsUninstallOptions(
+  @HelpMessage("Path to `*rc` file, defaults to `.bashrc` or `.zshrc` depending on shell (bash or zsh only)")
+    rcFile: Option[String] = None,
+  @HelpMessage("Custom banner in comment placed in rc file")
+    banner: String = "{NAME} completions",
+  @HelpMessage("Custom completions name")
+    name: Option[String] = None,
+  @HelpMessage("Completions output directory (defaults to $XDG_CONFIG_HOME/fish/completions on fish)")
+  @Name("o")
+    output: Option[String] = None,
+)
+// format: on
+
+object CompletionsUninstallOptions {
+  implicit lazy val parser: Parser[CompletionsUninstallOptions] = Parser.derive
+  implicit lazy val help: Help[CompletionsUninstallOptions]     = Help.derive
+}
diff --git a/core/shared/src/main/scala/caseapp/core/complete/Fish.scala b/core/shared/src/main/scala/caseapp/core/complete/Fish.scala
index 36f970ce..dd773f14 100644
--- a/core/shared/src/main/scala/caseapp/core/complete/Fish.scala
+++ b/core/shared/src/main/scala/caseapp/core/complete/Fish.scala
@@ -8,8 +8,7 @@ object Fish {
     s"$shellName-v1"
 
   def script(progName: String): String =
-    s"""
-    complete $progName -a '($progName complete $id (math 1 + (count (__fish_print_cmd_args))) (__fish_print_cmd_args))'
+    s"""complete $progName -a '($progName complete $id (math 1 + (count (__fish_print_cmd_args))) (__fish_print_cmd_args))'
        |""".stripMargin
 
   private def escape(s: String): String =
diff --git a/core/shared/src/main/scala/caseapp/core/complete/HelpCompleter.scala b/core/shared/src/main/scala/caseapp/core/complete/HelpCompleter.scala
index ec453072..1e09b031 100644
--- a/core/shared/src/main/scala/caseapp/core/complete/HelpCompleter.scala
+++ b/core/shared/src/main/scala/caseapp/core/complete/HelpCompleter.scala
@@ -9,7 +9,7 @@ class HelpCompleter[T](help: Help[T]) extends Completer[T] {
       .args
       .iterator
       .flatMap { arg =>
-        val names = (arg.name +: arg.extraNames)
+        val names = arg.names
           .map(help.nameFormatter.format)
           .map(n => (if (n.length == 1) "-" else "--") + n)
           .filter(_.startsWith(prefix))
diff --git a/core/shared/src/main/scala/caseapp/core/help/Help.scala b/core/shared/src/main/scala/caseapp/core/help/Help.scala
index 779bab2f..afff4071 100644
--- a/core/shared/src/main/scala/caseapp/core/help/Help.scala
+++ b/core/shared/src/main/scala/caseapp/core/help/Help.scala
@@ -68,8 +68,7 @@ import caseapp.HelpMessage
   }
 
   def duplicates: Map[String, Seq[Arg]] = {
-    val pairs = args.map(a => a.name.option(nameFormatter) -> a) ++
-      args.flatMap(a => a.extraNames.map(n => n.option(nameFormatter) -> a))
+    val pairs = args.flatMap(a => a.names.map(n => n.option(nameFormatter) -> a))
     pairs
       .groupBy(_._1)
       .mapValues(_.map(_._2))
@@ -199,7 +198,7 @@ object Help extends HelpCompanion {
     args
       .collect {
         case arg if showHidden || !arg.noHelp =>
-          val names = (arg.name +: arg.extraNames).distinct
+          val names = arg.names.distinct
 
           // FIXME Flags that accept no value are not given the right help message here
           val valueDescription = arg
@@ -229,8 +228,9 @@ object Help extends HelpCompanion {
     for (arg <- args if showHidden || !arg.noHelp) yield {
       val namesToShow = format.namesLimit match {
         case Some(limit) if !showHidden && limit >= 0 =>
-          (arg.name +: arg.extraNames).take(limit)
-        case _ => arg.name +: arg.extraNames
+          arg.names.take(limit)
+        case _ =>
+          arg.names
       }
 
       val sortedNames = namesToShow
diff --git a/core/shared/src/main/scala/caseapp/core/parser/StandardArgument.scala b/core/shared/src/main/scala/caseapp/core/parser/StandardArgument.scala
index fcf1a139..df90cc50 100644
--- a/core/shared/src/main/scala/caseapp/core/parser/StandardArgument.scala
+++ b/core/shared/src/main/scala/caseapp/core/parser/StandardArgument.scala
@@ -32,7 +32,8 @@ import caseapp.Name
         Right(None)
 
       case firstArg :: rem =>
-        val matchedOpt = (Iterator(arg.name) ++ arg.extraNames.iterator)
+        val matchedOpt = arg.names
+          .iterator
           .map(n => n -> n(firstArg, nameFormatter))
           .collectFirst {
             case (n, Right(valueOpt)) => n -> valueOpt
diff --git a/core/shared/src/main/scala/caseapp/core/util/Formatter.scala b/core/shared/src/main/scala/caseapp/core/util/Formatter.scala
index 91d5236b..3fd20599 100644
--- a/core/shared/src/main/scala/caseapp/core/util/Formatter.scala
+++ b/core/shared/src/main/scala/caseapp/core/util/Formatter.scala
@@ -12,8 +12,10 @@ object Formatter {
     *
     * Default formatter will format option arguments as `foo-bar`.
     */
-  val DefaultNameFormatter: Formatter[Name] = new Formatter[Name] {
-    override def format(name: Name): String =
+  val DefaultNameFormatter: Formatter[Name] = Default
+
+  case object Default extends Formatter[Name] {
+    def format(name: Name): String =
       CaseUtil
         .pascalCaseSplit(name.name.toList)
         .map(_.toLowerCase)
diff --git a/core/shared/src/main/scala/caseapp/package.scala b/core/shared/src/main/scala/caseapp/package.scala
index 754edf65..486bdc00 100644
--- a/core/shared/src/main/scala/caseapp/package.scala
+++ b/core/shared/src/main/scala/caseapp/package.scala
@@ -17,7 +17,8 @@ package object caseapp {
   type CaseApp[T] = core.app.CaseApp[T]
   val CaseApp = core.app.CaseApp
 
-  type Command[T] = core.app.Command[T]
+  type Command[T]         = core.app.Command[T]
+  type CommandsEntryPoint = core.app.CommandsEntryPoint
 
   type RemainingArgs = core.RemainingArgs
   val RemainingArgs = core.RemainingArgs