diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a7e9b3d..2bafcf2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,7 +38,7 @@ jobs:
         # produce green tests on every PR.
         jdk: ["21", "25"]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 1
 
@@ -115,7 +115,7 @@ jobs:
     permissions:
       contents: read
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-java@v4
         with:
           distribution: temurin
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index e02ec2f..017b695 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -27,7 +27,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Initialize CodeQL
         uses: github/codeql-action/init@v4
diff --git a/.github/workflows/diagrams.yml b/.github/workflows/diagrams.yml
index d7579e6..674a914 100644
--- a/.github/workflows/diagrams.yml
+++ b/.github/workflows/diagrams.yml
@@ -15,7 +15,7 @@ jobs:
     name: re-render and diff
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install Graphviz
         run: sudo apt-get update && sudo apt-get install -y graphviz
diff --git a/.github/workflows/pitest-nightly.yml b/.github/workflows/pitest-nightly.yml
index a6c7c6f..dda7372 100644
--- a/.github/workflows/pitest-nightly.yml
+++ b/.github/workflows/pitest-nightly.yml
@@ -15,7 +15,7 @@ jobs:
       matrix:
         module: [arcp-core, arcp-runtime]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: actions/setup-java@v4
         with:
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 9c73a5e..92c22ab 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -22,7 +22,7 @@ jobs:
     permissions:
       contents: write  # for tagging
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0