diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 86a4433..745b77e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -14,7 +14,7 @@ jobs:
     name: Python (ruff + pytest)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Install uv
         uses: astral-sh/setup-uv@v5
       - name: Lint (ruff)
@@ -26,7 +26,7 @@ jobs:
     name: Notebook (reproducibility)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Install uv
         uses: astral-sh/setup-uv@v5
       - name: Execute the case-study notebook on a copy (reproducibility check)
@@ -42,7 +42,7 @@ jobs:
     name: Terraform (fmt + validate)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: hashicorp/setup-terraform@v3
         with:
           terraform_version: "1.7.5"
@@ -57,7 +57,7 @@ jobs:
     name: Markdown lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: markdownlint
         uses: DavidAnson/markdownlint-cli2-action@v19
         with:
@@ -67,7 +67,7 @@ jobs:
     name: Secret scan (gitleaks)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Install gitleaks (CLI)