diff --git a/.github/workflows/concretize-lxplus.yaml b/.github/workflows/concretize-lxplus.yaml
deleted file mode 100644
index b714ff9e..00000000
--- a/.github/workflows/concretize-lxplus.yaml
+++ /dev/null
@@ -1,33 +0,0 @@
-name: concretize-lxplus
-on: [push, pull_request]
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v2
-    - uses: cvmfs-contrib/github-action-cvmfs@v2
-      with:
-        cvmfs_repositories: 'sw.hsf.org,sw-nightlies.hsf.org,sft-nightlies.cern.ch,sft.cern.ch,geant4.cern.ch'
-    - name: Start container
-      run: |
-        docker run -it --name CI_container -e GITHUB_ENV=${GITHUB_ENV}  -v ${GITHUB_WORKSPACE}:/Package -v /cvmfs:/cvmfs:shared -d ghcr.io/aidasoft/centos7:latest /bin/bash
-    - name: Setup Spack
-      run: |
-        docker exec CI_container /bin/bash -c 'cd ./Package
-        git clone --depth 1 https://github.com/key4hep/spack
-        git clone --depth 1 https://github.com/key4hep/key4hep-spack
-        '
-    - name: Concretize
-      run: |
-        docker exec CI_container /bin/bash -c 'cd ./Package
-        source spack/share/spack/setup-env.sh
-        spack env activate environments/key4hep-release-user
-        spack repo add key4hep-spack
-        source environments/key4hep-release-user/setup_clingo_centos7.sh
-        spack add key4hep-stack
-        spack concretize -f --reuse | tee -a key4hep-stack-concretization.log;'
-    - uses: actions/upload-artifact@v2
-      with:
-        name: concretization-log-artifact
-        path: key4hep-stack-concretization.log
-        retention-days: 5
diff --git a/.github/workflows/concretize-ubuntu.yaml b/.github/workflows/concretize-ubuntu.yaml
deleted file mode 100644
index 2df0dbb1..00000000
--- a/.github/workflows/concretize-ubuntu.yaml
+++ /dev/null
@@ -1,21 +0,0 @@
-name: concretize-ubuntu
-
-on: [push, pull_request]
-
-jobs:
-  test:
-    runs-on: ubuntu-latest
-    strategy:
-      fail-fast: false
-    steps:
-    - uses: actions/checkout@v2
-    - name: Concretize key4hep-stack
-      run: |
-        git clone --depth 1 https://github.com/key4hep/spack
-        source spack/share/spack/setup-env.sh
-        spack env create testenv
-        spack env activate testenv
-        spack repo add .
-        spack compiler find
-        spack add key4hep-stack
-        spack concretize  | tee -a ${GITHUB_WORKSPACE}/key4hep-stack-concretization.log
diff --git a/.github/workflows/concretize.yaml b/.github/workflows/concretize.yaml
new file mode 100644
index 00000000..64f88286
--- /dev/null
+++ b/.github/workflows/concretize.yaml
@@ -0,0 +1,69 @@
+on:
+  push:
+    branches:
+    - main
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  concretize:
+    concurrency:
+      group: ${{ github.workflow }}-${{ github.ref }}-${{ matrix.image }}-${{ matrix.build_type }}
+      cancel-in-progress: true
+    strategy:
+      matrix:
+        image: [alma9, ubuntu22]
+        build_type: [release, nightly]
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Start container
+        run: |
+            name=$(echo "${{ github.event.repository.name }}" | tr '[:upper:]' '[:lower:]')
+            if [ "${{ matrix.image }}" = "alma9" ]; then
+              docker run --name container --privileged -v ${GITHUB_WORKSPACE}:/key4hep-spack -v ~/.cache/ccache:/root/.cache/ccache -d ghcr.io/key4hep/key4hep-images/alma9-cvmfs tail -f /dev/null
+            elif [ "${{ matrix.image }}" = "ubuntu22" ]; then
+              docker run --name container --privileged -v ${GITHUB_WORKSPACE}:/key4hep-spack -v ~/.cache/ccache:/root/.cache/ccache -d ghcr.io/key4hep/key4hep-images/ubuntu22-cvmfs tail -f /dev/null
+            else
+              echo "Unknown image"
+              exit 1
+            fi
+
+      - name: Setup environment and concretize
+        run: |
+
+            cat <<'EOF' > ${GITHUB_WORKSPACE}/script_container.sh
+            set -e
+
+            cd /
+            ls -lah /
+            ls -lah /key4hep-spack
+
+            git clone https://github.com/spack/spack -q
+            source spack/share/spack/setup-env.sh
+
+            cd /spack
+            git checkout $(cat /key4hep-spack/.latest-commit)
+            source /key4hep-spack/.cherry-pick
+
+            if [ "${{ matrix.build_type }}" = "release" ]; then
+                env=key4hep-release
+            elif [ "${{ matrix.build_type }}" = "nightly" ]; then
+                env=key4hep-nightly-opt
+                pip3 install pyyaml
+                python3 /key4hep-spack/scripts/fetch_nightly_versions.py --path /key4hep-spack/environments/key4hep-common/packages.yaml --extra-path /key4hep-spack/environments/key4hep-nightly-opt/packages.yaml ""
+            else
+                echo "Unknown build type"
+                exit 1
+            fi
+            cd /key4hep-spack/environments/${env}
+            spack env activate .
+            spack concretize
+
+            EOF
+
+            chmod +x ${GITHUB_WORKSPACE}/script_container.sh
+
+            # cat ${GITHUB_WORKSPACE}/script_container.sh
+
+            docker exec container /bin/bash -c "/mount.sh && /key4hep-spack/script_container.sh"