diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 03682df3..8b55ef37 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -35,7 +35,7 @@ jobs:
     timeout-minutes: 60
     steps:
       - name: Checkout current branch (full)
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 
@@ -91,7 +91,7 @@ jobs:
 
       - name: Upload target directories
         if: github.event_name != 'pull_request' && (startsWith(github.ref, 'refs/tags/v') || github.ref == 'refs/heads/main')
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: target-${{ matrix.os }}-${{ matrix.java }}-${{ matrix.scala }}
           path: targets.tar
@@ -107,7 +107,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout current branch (full)
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 
@@ -128,7 +128,7 @@ jobs:
         run: sbt +update
 
       - name: Download target directories (2.13)
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: target-${{ matrix.os }}-${{ matrix.java }}-2.13
 
@@ -138,7 +138,7 @@ jobs:
           rm targets.tar
 
       - name: Download target directories (2.12)
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: target-${{ matrix.os }}-${{ matrix.java }}-2.12
 
@@ -148,7 +148,7 @@ jobs:
           rm targets.tar
 
       - name: Download target directories (3)
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: target-${{ matrix.os }}-${{ matrix.java }}-3
 
@@ -191,7 +191,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout current branch (full)
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 
@@ -226,7 +226,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout current branch (full)
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 
diff --git a/build.sbt b/build.sbt
index 02caa2f2..2613b726 100644
--- a/build.sbt
+++ b/build.sbt
@@ -12,8 +12,8 @@ ThisBuild / startYear := Some(2014)
 // publish website from this branch
 ThisBuild / tlSitePublishBranch := Some("main")
 
-val Scala213 = "2.13.16"
-ThisBuild / crossScalaVersions := Seq(Scala213, "2.12.20", "3.3.7")
+val Scala213 = "2.13.18"
+ThisBuild / crossScalaVersions := Seq(Scala213, "2.12.21", "3.3.7")
 ThisBuild / scalaVersion := Scala213 // the default Scala
 ThisBuild / tlJdkRelease := Some(17)
 ThisBuild / githubWorkflowJavaVersions ~= {
diff --git a/project/plugins.sbt b/project/plugins.sbt
index e3f8dc6d..b4f77209 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -1 +1 @@
-addSbtPlugin("org.http4s" % "sbt-http4s-org" % "2.0.2")
+addSbtPlugin("org.http4s" % "sbt-http4s-org" % "2.0.5")