diff --git a/.github/workflows/benchmark.yml b/.github/workflows/benchmark.yml
index c6af728..75598a1 100644
--- a/.github/workflows/benchmark.yml
+++ b/.github/workflows/benchmark.yml
@@ -9,7 +9,7 @@ jobs:
   benchmark:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: astral-sh/setup-uv@v4
 
diff --git a/.github/workflows/contributor-dry-run-monthly.yml b/.github/workflows/contributor-dry-run-monthly.yml
index 98ef3cc..3fb6c9c 100644
--- a/.github/workflows/contributor-dry-run-monthly.yml
+++ b/.github/workflows/contributor-dry-run-monthly.yml
@@ -9,7 +9,7 @@ jobs:
   dry-run:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: astral-sh/setup-uv@v4
       - uses: actions/setup-node@v4
         with:
diff --git a/.github/workflows/corpus-validation.yml b/.github/workflows/corpus-validation.yml
index 794cc7e..a72a772 100644
--- a/.github/workflows/corpus-validation.yml
+++ b/.github/workflows/corpus-validation.yml
@@ -9,7 +9,7 @@ jobs:
   validate-corpus:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: astral-sh/setup-uv@v4
 
diff --git a/.github/workflows/docs-blueprint.yml b/.github/workflows/docs-blueprint.yml
index 9b75cb7..eae2556 100644
--- a/.github/workflows/docs-blueprint.yml
+++ b/.github/workflows/docs-blueprint.yml
@@ -9,7 +9,7 @@ jobs:
   check-docs:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: actions/setup-python@v5
         with:
diff --git a/.github/workflows/lean-ci.yml b/.github/workflows/lean-ci.yml
index 5674d8f..8eb93b6 100644
--- a/.github/workflows/lean-ci.yml
+++ b/.github/workflows/lean-ci.yml
@@ -9,7 +9,7 @@ jobs:
   build-lean:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install elan
         run: |
diff --git a/.github/workflows/mcp-contract.yml b/.github/workflows/mcp-contract.yml
index 1971c82..b064a66 100644
--- a/.github/workflows/mcp-contract.yml
+++ b/.github/workflows/mcp-contract.yml
@@ -10,7 +10,7 @@ jobs:
   mcp-tests:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: astral-sh/setup-uv@v4
       - name: Install deps (including MCP extras)
         run: uv sync --all-packages --extra mcp
diff --git a/.github/workflows/portal-ci.yml b/.github/workflows/portal-ci.yml
index 42f5b8d..a07c8df 100644
--- a/.github/workflows/portal-ci.yml
+++ b/.github/workflows/portal-ci.yml
@@ -9,7 +9,7 @@ jobs:
   build-portal:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: pnpm/action-setup@v4
         with:
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 180dd5a..851cc92 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -13,7 +13,7 @@ jobs:
   release:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: astral-sh/setup-uv@v4
       - uses: pnpm/action-setup@v4
diff --git a/.github/workflows/security-sarif.yml b/.github/workflows/security-sarif.yml
index acd7b3f..c8132ee 100644
--- a/.github/workflows/security-sarif.yml
+++ b/.github/workflows/security-sarif.yml
@@ -14,7 +14,7 @@ jobs:
   ruff-sarif:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: astral-sh/setup-uv@v4
       - name: Install Python deps
         run: uv sync --all-packages