diff --git a/.github/workflows/build-bluebuild.yml b/.github/workflows/build-bluebuild.yml
index e0e49dc..951ba35 100644
--- a/.github/workflows/build-bluebuild.yml
+++ b/.github/workflows/build-bluebuild.yml
@@ -57,12 +57,12 @@ jobs:
           df -h
 
       # BlueBuild action wraps: image build, cosign sign (keyless via
-      # Sigstore), GHCR push. To pin to a commit SHA in a follow-up
-      # once the workflow shape stabilises (CI hardening agent 8,
-      # 2026-05-05 wave).
+      # Sigstore), GHCR push. Pinned to a commit SHA per CI hardening
+      # agent 8 (2026-05-05 wave). The trailing comment records the
+      # tag the SHA resolved from, so future bumps stay legible.
       - name: Build + push veilor-os OCI
         id: bluebuild
-        uses: blue-build/github-action@v1
+        uses: blue-build/github-action@24d146df25adc2cf579e918efe2d9bff6adea408 # v1
         with:
           recipe: bluebuild/recipe.yml
           registry_token: ${{ secrets.GITHUB_TOKEN }}