diff --git a/.git-blame-ignore-revs b/.git-blame-ignore-revs
index 79123394a7..df54f9b3ba 100644
--- a/.git-blame-ignore-revs
+++ b/.git-blame-ignore-revs
@@ -18,3 +18,6 @@ fadb726e4d1855de746b61ed1bd3bb229f7e3f95
 
 # Scala Steward: Reformat with scalafmt 3.8.3
 6a75de98b210cf0cc9cd4bf8693ac80bf3ab32ab
+
+# Scala Steward: Reformat with scalafmt 3.8.4
+c94b1327f346ed0dddc374c7844aaa55080dc84f
diff --git a/.scalafmt.conf b/.scalafmt.conf
index e2602612a1..68a19db899 100644
--- a/.scalafmt.conf
+++ b/.scalafmt.conf
@@ -1,4 +1,4 @@
-version = 3.8.3
+version = 3.8.4
 project.layout = StandardConvention
 runner.dialect = scala3
 maxColumn = 120
diff --git a/airframe-core/.js/src/main/scala-3/wvlet/airframe/log/JSConsoleLogHandler.scala b/airframe-core/.js/src/main/scala-3/wvlet/airframe/log/JSConsoleLogHandler.scala
index c909e0f9c4..58606150b3 100644
--- a/airframe-core/.js/src/main/scala-3/wvlet/airframe/log/JSConsoleLogHandler.scala
+++ b/airframe-core/.js/src/main/scala-3/wvlet/airframe/log/JSConsoleLogHandler.scala
@@ -1,6 +1,6 @@
 package wvlet.airframe.log
 
-import java.util.{logging as jl}
+import java.util.logging as jl
 
 import wvlet.airframe.log.JSConsoleLogHandler.JSLogColorPalette
 
diff --git a/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/io/IOUtil.scala b/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/io/IOUtil.scala
index 370c5d8f75..6dd2e7d2da 100644
--- a/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/io/IOUtil.scala
+++ b/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/io/IOUtil.scala
@@ -43,11 +43,10 @@ object IOUtil:
 
   def findPath(path: File): Option[File] =
     if path.exists() then Some(path)
-    else {
+    else
       val defaultPath = new File(new File(System.getProperty("prog.home", "")), path.getPath)
       if defaultPath.exists() then Some(defaultPath)
       else None
-    }
 
   def readAsString(f: File): String =
     readAsString(f.toURI.toURL)
diff --git a/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/log/AsyncHandler.scala b/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/log/AsyncHandler.scala
index 7da2cc5a6a..5df6a3525b 100644
--- a/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/log/AsyncHandler.scala
+++ b/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/log/AsyncHandler.scala
@@ -4,7 +4,7 @@ import java.io.Flushable
 import java.util
 import java.util.concurrent.atomic.AtomicBoolean
 import java.util.concurrent.{Executors, ThreadFactory, TimeUnit}
-import java.util.{logging as jl}
+import java.util.logging as jl
 
 /**
   * Logging using a background thread
diff --git a/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/log/LogRotationHandler.scala b/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/log/LogRotationHandler.scala
index b35193e37d..27750050c2 100644
--- a/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/log/LogRotationHandler.scala
+++ b/airframe-core/.jvm/src/main/scala-3/wvlet/airframe/log/LogRotationHandler.scala
@@ -16,7 +16,7 @@ package wvlet.airframe.log
 import java.io.{File, Flushable}
 import java.nio.charset.StandardCharsets
 import java.util.logging.ErrorManager
-import java.util.{logging as jl}
+import java.util.logging as jl
 import ch.qos.logback.core.ContextBase
 import ch.qos.logback.core.encoder.EncoderBase
 import ch.qos.logback.core.rolling.{
diff --git a/airframe-core/src/main/scala-3/wvlet/airframe/log/Handler.scala b/airframe-core/src/main/scala-3/wvlet/airframe/log/Handler.scala
index d50b288365..021f761c96 100644
--- a/airframe-core/src/main/scala-3/wvlet/airframe/log/Handler.scala
+++ b/airframe-core/src/main/scala-3/wvlet/airframe/log/Handler.scala
@@ -1,7 +1,7 @@
 package wvlet.airframe.log
 
 import java.io.{PrintStream, PrintWriter}
-import java.util.{logging as jl}
+import java.util.logging as jl
 
 /**
   * Output log to stderr
diff --git a/airframe-core/src/main/scala-3/wvlet/airframe/log/LogFormat.scala b/airframe-core/src/main/scala-3/wvlet/airframe/log/LogFormat.scala
index e3bbce6a16..acf99009f2 100644
--- a/airframe-core/src/main/scala-3/wvlet/airframe/log/LogFormat.scala
+++ b/airframe-core/src/main/scala-3/wvlet/airframe/log/LogFormat.scala
@@ -18,7 +18,7 @@ import wvlet.airframe.log.AnsiColorPalette
 import java.io.{PrintWriter, StringWriter}
 import java.util.logging.Formatter
 import java.util.regex.Pattern
-import java.util.{logging as jl}
+import java.util.logging as jl
 import wvlet.airframe.log.LogLevel.{DEBUG, ERROR, INFO, TRACE, WARN}
 
 /**
diff --git a/airframe-core/src/main/scala-3/wvlet/airframe/log/LogRecord.scala b/airframe-core/src/main/scala-3/wvlet/airframe/log/LogRecord.scala
index c48c1601ad..acf6866a23 100644
--- a/airframe-core/src/main/scala-3/wvlet/airframe/log/LogRecord.scala
+++ b/airframe-core/src/main/scala-3/wvlet/airframe/log/LogRecord.scala
@@ -13,7 +13,7 @@
  */
 package wvlet.airframe.log
 
-import java.util.{logging as jl}
+import java.util.logging as jl
 
 object LogRecord:
   def apply(record: jl.LogRecord): LogRecord =
diff --git a/airframe-http/.jvm/src/main/scala/wvlet/airframe/http/Router.scala b/airframe-http/.jvm/src/main/scala/wvlet/airframe/http/Router.scala
index 67874a538f..e1ac4e3da6 100644
--- a/airframe-http/.jvm/src/main/scala/wvlet/airframe/http/Router.scala
+++ b/airframe-http/.jvm/src/main/scala/wvlet/airframe/http/Router.scala
@@ -220,8 +220,7 @@ object Router extends router.RouterObjectBase with LogSupport {
 
   private[http] def isFuture(s: Surface): Boolean = {
     s match {
-      case h: HigherKindedTypeSurface
-          if h.typeArgs.size == 1 && h.name == "F" => // Only support 'F' for tagless-final pattern
+      case h: HigherKindedTypeSurface if h.typeArgs.size == 1 && h.name == "F" => // Only support 'F' for tagless-final pattern
         true
       case s: Surface
           if s.rawType == classOf[scala.concurrent.Future[_]] || s.rawType.getName == "com.twitter.util.Future" =>
@@ -233,8 +232,7 @@ object Router extends router.RouterObjectBase with LogSupport {
 
   private[http] def unwrapFuture(s: Surface): Surface = {
     s match {
-      case h: HigherKindedTypeSurface
-          if h.typeArgs.size == 1 && h.name == "F" => // Only support 'F' for tagless-final pattern
+      case h: HigherKindedTypeSurface if h.typeArgs.size == 1 && h.name == "F" => // Only support 'F' for tagless-final pattern
         h.typeArgs.head
       case s: Surface
           if s.rawType == classOf[scala.concurrent.Future[_]] || s.rawType.getName == "com.twitter.util.Future" =>
diff --git a/airframe-rx-html/src/main/scala/wvlet/airframe/rx/html/HtmlAttrs.scala b/airframe-rx-html/src/main/scala/wvlet/airframe/rx/html/HtmlAttrs.scala
index 12f137c342..77bbddfab1 100644
--- a/airframe-rx-html/src/main/scala/wvlet/airframe/rx/html/HtmlAttrs.scala
+++ b/airframe-rx-html/src/main/scala/wvlet/airframe/rx/html/HtmlAttrs.scala
@@ -77,9 +77,7 @@ trait GlobalAttrs {
     * Specifies the text direction for the content in an element. The valid values are:
     *
     *   - `ltr` Default. Left-to-right text direction
-    *
     *   - `rtl` Right-to-left text direction
-    *
     *   - `auto` Let the browser figure out the text direction, based on the content, (only recommended if the text
     *     direction is unknown)
     */
@@ -759,7 +757,6 @@ trait InputAttrs extends GlobalAttrs {
     *
     *   - post: Corresponds to the HTTP POST method ; form data are included in the body of the form and sent to the
     *     server.
-    *
     *   - get: Corresponds to the HTTP GET method; form data are appended to the action attribute URI with a '?' as a
     *     separator, and the resulting URI is sent to the server. Use this method when the form has no side-effects and
     *     contains only ASCII characters.
diff --git a/airframe-surface/src/main/scala-3/wvlet/airframe/surface/CompileTimeSurfaceFactory.scala b/airframe-surface/src/main/scala-3/wvlet/airframe/surface/CompileTimeSurfaceFactory.scala
index 73200ad56f..d20ee6e810 100644
--- a/airframe-surface/src/main/scala-3/wvlet/airframe/surface/CompileTimeSurfaceFactory.scala
+++ b/airframe-surface/src/main/scala-3/wvlet/airframe/surface/CompileTimeSurfaceFactory.scala
@@ -380,8 +380,7 @@ private[surface] class CompileTimeSurfaceFactory[Q <: Quotes](using quotes: Q):
   private def isPathDependentType(t: TypeRepr): Boolean =
     !t.typeSymbol.flags.is(Flags.JavaStatic) && (t match
       case t: TypeBounds => true
-      case _             => false
-    )
+      case _             => false)
 
   private def genericTypeFactory: Factory = {
     case t if t =:= TypeRepr.of[Any] =>
diff --git a/airframe-surface/src/main/scala/wvlet/airframe/surface/tag/package.scala b/airframe-surface/src/main/scala/wvlet/airframe/surface/tag/package.scala
index a2a2ad9579..a1ac6aa360 100644
--- a/airframe-surface/src/main/scala/wvlet/airframe/surface/tag/package.scala
+++ b/airframe-surface/src/main/scala/wvlet/airframe/surface/tag/package.scala
@@ -19,7 +19,7 @@ import scala.language.implicitConversions
 /**
   * This code is from com.softwaremill.tagging
   *
-  * Tag instances with arbitrary types. The tags are usually empty `trait`s. Tags have no runtime overhead and are only
+  * Tag instances with arbitrary types. The tags are usually empty `trait` s. Tags have no runtime overhead and are only
   * used at compile-time for additional type safety.
   *
   * For example:
diff --git a/airspec/build.sbt b/airspec/build.sbt
index 5342627eec..7fb1d8f1d2 100644
--- a/airspec/build.sbt
+++ b/airspec/build.sbt
@@ -130,7 +130,8 @@ def excludePomDependency(excludes: Seq[String]) = { node: XmlNode =>
   }).transform(node).head
 }
 
-/** AirSpec build definitions.
+/**
+  * AirSpec build definitions.
   *
   * To make AirSpec a standalone library without any cyclic project references, AirSpec embeds the source code of
   * airframe-log, di, surface, etc.
diff --git a/airspec/project/plugin.sbt b/airspec/project/plugin.sbt
index 75d20b2ff8..ed6087e958 100755
--- a/airspec/project/plugin.sbt
+++ b/airspec/project/plugin.sbt
@@ -10,7 +10,7 @@ addSbtPlugin("com.eed3si9n"       % "sbt-buildinfo"            % "0.13.1")
 addDependencyTreePlugin
 
 // For Scala.js
-val SCALAJS_VERSION = sys.env.getOrElse("SCALAJS_VERSION", "1.18.1")
+val SCALAJS_VERSION          = sys.env.getOrElse("SCALAJS_VERSION", "1.18.1")
 addSbtPlugin("org.scala-js"  % "sbt-scalajs"         % SCALAJS_VERSION)
 addSbtPlugin("ch.epfl.scala" % "sbt-scalajs-bundler" % "0.21.1")
 libraryDependencies ++= (
diff --git a/build.sbt b/build.sbt
index 606380119f..ec793414c8 100644
--- a/build.sbt
+++ b/build.sbt
@@ -974,7 +974,7 @@ lazy val fluentd =
         "org.komamitsu" % "fluency-fluentd"      % FLUENCY_VERSION,
         "org.komamitsu" % "fluency-treasuredata" % FLUENCY_VERSION
         // td-client-java -> json-simple happened to include junit 4.10 [CVE-2020-15250]
-          exclude ("junit", "junit"),
+        exclude ("junit", "junit"),
         // Necessary for td-client-java, which is used in fluency-treasuredata
         "com.fasterxml.jackson.datatype" % "jackson-datatype-json-org" % "2.18.2" % Provided,
         "com.fasterxml.jackson.datatype" % "jackson-datatype-jdk8"     % "2.18.2" % Provided,
diff --git a/project/plugin.sbt b/project/plugin.sbt
index a63162e019..cb6b6f7806 100755
--- a/project/plugin.sbt
+++ b/project/plugin.sbt
@@ -20,7 +20,7 @@ addSbtPlugin("org.wvlet.airframe" % "sbt-airframe" % SBT_AIRFRAME_VERSION)
 addDependencyTreePlugin
 
 // For Scala.js
-val SCALAJS_VERSION = sys.env.getOrElse("SCALAJS_VERSION", "1.18.1")
+val SCALAJS_VERSION          = sys.env.getOrElse("SCALAJS_VERSION", "1.18.1")
 addSbtPlugin("org.scala-js"  % "sbt-scalajs"         % SCALAJS_VERSION)
 addSbtPlugin("ch.epfl.scala" % "sbt-scalajs-bundler" % "0.21.1")
 libraryDependencies ++= (
diff --git a/sbt-airframe/src/sbt-test/sbt-airframe/js-client/project/plugins.sbt b/sbt-airframe/src/sbt-test/sbt-airframe/js-client/project/plugins.sbt
index 7783b653ed..99bfcc8254 100644
--- a/sbt-airframe/src/sbt-test/sbt-airframe/js-client/project/plugins.sbt
+++ b/sbt-airframe/src/sbt-test/sbt-airframe/js-client/project/plugins.sbt
@@ -8,4 +8,4 @@ sys.props.get("plugin.version") match {
 // For Scala.js
 addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "1.3.2")
 val SCALAJS_VERSION = sys.env.getOrElse("SCALAJS_VERSION", "1.18.1")
-addSbtPlugin("org.scala-js" % "sbt-scalajs" % SCALAJS_VERSION)
+addSbtPlugin("org.scala-js"       % "sbt-scalajs"              % SCALAJS_VERSION)