diff --git a/.github/workflows/macos-ci.yml b/.github/workflows/macos-ci.yml
new file mode 100644
index 000000000..77e6d6dd7
--- /dev/null
+++ b/.github/workflows/macos-ci.yml
@@ -0,0 +1,185 @@
+name: macOS CI Build
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: false
+
+permissions:
+  contents: read
+  packages: write
+
+jobs:
+  build:
+    runs-on: macos-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        ENV: [ci, xl, tf]
+
+    env:
+      GITHUB_REGISTRY_USER: ${{ secrets.GHCR_REGISTRY_USER }}
+      GITHUB_REGISTRY_TOKEN: ${{ secrets.GHCR_REGISTRY_TOKEN }}
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v7
+
+      - name: Set Deployment Target to match runner SDK
+        run: |
+          # Fetch the active SDK version (e.g., 14.5)
+          CURRENT_SDK=$(xcrun --show-sdk-version)
+
+          # Export it to the GitHub environment so all future steps use it
+          echo "MACOSX_DEPLOYMENT_TARGET=$CURRENT_SDK" >> $GITHUB_ENV
+
+      - name: Extract Spack configuration
+        id: spack-config
+        run: |
+          # Source spack.sh to get SPACK_VERSION and SPACK_CHERRYPICKS
+          source spack.sh
+          echo "spack-version=${SPACK_VERSION}" >> $GITHUB_OUTPUT
+          echo "spack-cherrypicks<<EOF" >> $GITHUB_OUTPUT
+          echo "${SPACK_CHERRYPICKS}" >> $GITHUB_OUTPUT
+          echo "EOF" >> $GITHUB_OUTPUT
+
+          # Source spack-packages.sh to get SPACKPACKAGES_VERSION and SPACKPACKAGES_CHERRYPICKS
+          source spack-packages.sh
+          echo "spackpackages-version=${SPACKPACKAGES_VERSION}" >> $GITHUB_OUTPUT
+          echo "spackpackages-cherrypicks<<EOF" >> $GITHUB_OUTPUT
+          echo "${SPACKPACKAGES_CHERRYPICKS}" >> $GITHUB_OUTPUT
+          echo "EOF" >> $GITHUB_OUTPUT
+
+          # Source key4hep-spack.sh to get KEY4HEPSPACK_VERSION
+          source key4hep-spack.sh
+          echo "key4hepspack-version=${KEY4HEPSPACK_VERSION}" >> $GITHUB_OUTPUT
+
+          # Source eic-spack.sh to get EICSPACK_VERSION
+          source eic-spack.sh
+          echo "eicspack-version=${EICSPACK_VERSION}" >> $GITHUB_OUTPUT
+
+          # Extract buildcache URL from mirrors.yaml.in (simplified - get the version)
+          echo "buildcache-version=${SPACKPACKAGES_VERSION}" >> $GITHUB_OUTPUT
+
+      - name: Checkout Spack repository
+        uses: actions/checkout@v7
+        with:
+          repository: spack/spack
+          path: spack
+          ref: ${{ steps.spack-config.outputs.spack-version }}
+          fetch-depth: 0
+
+      - name: Configure spack
+        run: |
+          cd ${{ github.workspace }}/spack
+          echo "${{ github.workspace }}/spack/bin" >> $GITHUB_PATH
+          git config user.name "GitHub Actions"
+          git config user.email "actions@github.com"
+
+          # Fetch branches from which we cherry-pick
+          git fetch origin refs/heads/develop:refs/heads/develop
+          git fetch origin pull/51584/head:pr-51584
+          git fetch origin pull/52207/head:pr-52207
+
+          # Apply cherry-picks from spack.sh (match only valid git commit hashes)
+          while read -r commit; do
+            if git merge-base --is-ancestor "${commit}" HEAD; then
+              echo "Skipping already applied ${commit}"
+              continue
+            fi
+            echo "Cherry-picking ${commit}"
+            git cherry-pick "${commit}"
+          done < <(echo "${{ steps.spack-config.outputs.spack-cherrypicks }}" | grep -E '^[a-f0-9]{40}$' || true)
+
+      - name: Checkout spack-packages repository
+        uses: actions/checkout@v7
+        with:
+          repository: spack/spack-packages
+          path: spack/var/spack/repos/spack-packages
+          ref: ${{ steps.spack-config.outputs.spackpackages-version }}
+
+      - name: Configure spack-packages
+        run: |
+          cd ${{ github.workspace }}/spack/var/spack/repos/spack-packages
+          git config user.name "GitHub Actions"
+          git config user.email "actions@github.com"
+
+          # Fetch branches from which we cherry-pick
+          git fetch origin refs/heads/develop:refs/heads/develop
+          git fetch origin pull/3698/head:pr-3698
+          git fetch origin pull/4871/head:pr-4871
+          git fetch origin pull/5856/head:pr-5856
+
+          # Apply cherry-picks from spack-packages.sh (match only valid git commit hashes)
+          while read -r commit; do
+            if git merge-base --is-ancestor "${commit}" HEAD; then
+              echo "Skipping already applied ${commit}"
+              continue
+            fi
+            echo "Cherry-picking ${commit}"
+            git cherry-pick "${commit}"
+          done < <(echo "${{ steps.spack-config.outputs.spackpackages-cherrypicks }}" | grep -E '^[a-f0-9]{40}$' || true)
+
+          cd ${{ github.workspace }}/spack
+          spack repo add var/spack/repos/spack-packages/repos/spack_repo/builtin
+
+      - name: Checkout key4hep-spack repository
+        uses: actions/checkout@v7
+        with:
+          repository: key4hep/key4hep-spack
+          path: spack/var/spack/repos/key4hep-spack
+          ref: ${{ steps.spack-config.outputs.key4hepspack-version }}
+
+      - name: Configure key4hep-spack
+        run: |
+          cd ${{ github.workspace }}/spack
+          spack repo add var/spack/repos/key4hep-spack
+
+      - name: Checkout eic-spack repository
+        uses: actions/checkout@v7
+        with:
+          repository: eic/eic-spack
+          path: spack/var/spack/repos/eic-spack
+          ref: ${{ steps.spack-config.outputs.eicspack-version }}
+
+      - name: Configure eic-spack
+        run: |
+          cd ${{ github.workspace }}/spack
+          spack repo add var/spack/repos/eic-spack/spack_repo/eic
+
+      - name: Add Spack environment
+        run: |
+          spack compiler find --scope site
+          spack external find --scope site llvm
+
+      - name: Configure buildcache
+        run: |
+          spack mirror add --scope site eic \
+            --autopush --unsigned \
+            --oci-username-variable GITHUB_REGISTRY_USER \
+            --oci-password-variable GITHUB_REGISTRY_TOKEN \
+            oci://ghcr.io/eic/spack-${{ steps.spack-config.outputs.buildcache-version }}
+
+      - name: Concretize base environment
+        run: |
+          spack -e spack-environment/${{matrix.ENV}} -c view:false concretize --force
+
+      - name: Install base environment
+        run: |
+          spack -e spack-environment/${{matrix.ENV}} -c view:false install --no-check-signature --show-log-on-error
+
+      - name: Concretize epic environment
+        run: |
+          spack -e spack-environment/${{matrix.ENV}}/epic -c view:false concretize --force
+
+      - name: Install epic environment
+        run: |
+          spack -e spack-environment/${{matrix.ENV}}/epic -c view:false install --no-check-signature --show-log-on-error
diff --git a/spack-environment/ci/spack.yaml b/spack-environment/ci/spack.yaml
index 00873132e..9893f6c7b 100644
--- a/spack-environment/ci/spack.yaml
+++ b/spack-environment/ci/spack.yaml
@@ -5,6 +5,18 @@ spack:
   - ../packages.yaml
   - ../packages_root_without_opengl.yaml
   - ../view.yaml
+  definitions:
+  # Note that in definitions 'when' takes a python expression as argument
+  # https://spack.readthedocs.io/en/latest/environments.html#spec-list-references
+  - when: arch.satisfies("platform=linux")
+    linux_packages: 
+    - imagemagick
+    - nopayloadclient
+    - ollama
+    - py-numpy
+    - py-scipy
+  - when: arch.satisfies("platform=darwin")
+    linux_packages: []
   specs:
   - acts
   - actsvg
@@ -24,15 +36,12 @@ spack:
   - hepmc3
   - hepmcmerger
   - heppdt
-  - imagemagick
   - irt
   - irt2
   - iwyu
   - jana2
   - just
-  - nopayloadclient
   - npsim -geocad
-  - ollama
   - onnx
   - osg-ca-certs
   - pelican
@@ -58,14 +67,12 @@ spack:
   - py-matplotlib
   - py-mplhep
   - py-htgettoken
-  - py-numpy
   - py-onnx
   - py-onnxruntime
   - py-pandas
   - py-particle
   - py-pip
   - py-rucio-clients
-  - py-scipy
   - py-seaborn
   - py-snakemake-storage-plugin-fs
   - py-snakemake-storage-plugin-pelican
diff --git a/spack-environment/packages.yaml b/spack-environment/packages.yaml
index 49b402160..03d50ddab 100644
--- a/spack-environment/packages.yaml
+++ b/spack-environment/packages.yaml
@@ -60,7 +60,7 @@ packages:
     - +brotli +bz2 +dataset +filesystem +glog +ipc +jemalloc +lz4 +parquet +snappy +zlib +zstd
   binutils:
     require:
-    - ~gold
+    - '@2.44:'
   blas:
     require:
     - openblas
@@ -73,14 +73,26 @@ packages:
     - cxxstd=20
   c:
     prefer:
-    - gcc
-    require:
-    - gcc
+    - spec: gcc
+      when: platform=linux
+    - spec: apple-clang
+      when: platform=darwin
+    require:
+    - spec: gcc
+      when: platform=linux
+    - spec: apple-clang
+      when: platform=darwin
   cxx:
     prefer:
-    - gcc
-    require:
-    - gcc
+    - spec: gcc
+      when: platform=linux
+    - spec: apple-clang
+      when: platform=darwin
+    require:
+    - spec: gcc
+      when: platform=linux
+    - spec: apple-clang
+      when: platform=darwin
   cairo:
     require:
     - '@1.18.2:'
@@ -202,9 +214,15 @@ packages:
     - +shared cxxstd=20
   fortran:
     prefer:
-    - gcc
-    require:
-    - gcc
+    - spec: gcc
+      when: platform=linux
+    - spec: gcc
+      when: platform=darwin
+    require:
+    - spec: gcc
+      when: platform=linux
+    - spec: gcc
+      when: platform=darwin
   freetype:
     require:
     - build_system=autotools
@@ -248,7 +266,13 @@ packages:
     require:
     - '@11.4.1.east'
     - cxxstd=20 -vecgeom +threads -vtk
-    - any_of: [+opengl +qt +x11, -opengl -qt -x11]
+    - any_of: [+opengl +qt, -opengl -qt]
+    - spec: ~x11
+      when: ~opengl platform=linux
+    - spec: +x11
+      when: +opengl platform=linux
+    - spec: ~x11
+      when: platform=darwin
   geant4-data:
     require:
     - +nudexlib +tendl +urrpt
@@ -263,10 +287,16 @@ packages:
     - ~gtk
   gl:
     require:
-    - glx
+    - spec: glx
+      when: platform=linux
+    - spec: apple-gl
+      when: platform=darwin
   glu:
     require:
-    - openglu
+    - spec: openglu
+      when: platform=linux
+    - spec: apple-glu
+      when: platform=darwin
   gloo:
     require:
     - '@2023-12-03'
@@ -642,8 +672,12 @@ packages:
   root:
     require:
     - '@6.40.02'
-    - cxxstd=20 +fftw +fortran +gdml +http -ipo +mlp +python +root7 +tmva +tmva-sofie +x +xrootd +ssl
+    - cxxstd=20 +fftw +fortran +gdml +http -ipo +mlp +python +root7 +tmva +tmva-sofie +xrootd +ssl
     - any_of: [+opengl +webgui, -opengl -webgui]
+    - spec: +x
+      when: platform=linux
+    - spec: ~x
+      when: platform=darwin
   sherpa:
     require:
     - '@3.0.1'
diff --git a/spack-environment/tf/spack.yaml b/spack-environment/tf/spack.yaml
index 5813947b8..6c24037a2 100644
--- a/spack-environment/tf/spack.yaml
+++ b/spack-environment/tf/spack.yaml
@@ -4,7 +4,13 @@ spack:
   - ../config.yaml
   - ../packages.yaml
   - ../view.yaml
+  definitions:
+  - when: arch.satisfies("platform=linux")
+    tensorflow: [py-tensorflow +cuda]
+  - when: arch.satisfies("platform=darwin")
+    tensorflow: [py-tensorflow ~cuda]
   specs:
+  - $tensorflow
   - edm4hep
   - onnx
   - osg-ca-certs
@@ -42,7 +48,6 @@ spack:
   - py-rucio-clients
   - py-scipy
   - py-seaborn
-  - py-tensorflow +cuda
   - py-tf2onnx
   - py-toml
   - py-uproot
diff --git a/spack-environment/xl/spack.yaml b/spack-environment/xl/spack.yaml
index 8b6cf2a60..48258b496 100644
--- a/spack-environment/xl/spack.yaml
+++ b/spack-environment/xl/spack.yaml
@@ -5,7 +5,15 @@ spack:
   - ../packages.yaml
   - ../packages_root_with_opengl.yaml
   - ../view.yaml
+  definitions:
+  # Note that in definitions 'when' takes a python expression as argument
+  # https://spack.readthedocs.io/en/latest/environments.html#spec-list-references
+  - when: arch.satisfies("platform=linux")
+    linux_packages: [strace, valgrind]
+  - when: arch.satisfies("platform=darwin")
+    linux_packages: []
   specs:
+  - $linux_packages
   - acts
   - actsvg
   - afterburner
@@ -133,8 +141,6 @@ spack:
   - snakemake
   - spdlog
   - stow
-  - strace
-  - valgrind
   - xeyes
   - xrootd
   - xrootd-mcp-server
diff --git a/spack-packages.sh b/spack-packages.sh
index 49b5b3f5e..0f5051fc0 100644
--- a/spack-packages.sh
+++ b/spack-packages.sh
@@ -12,21 +12,22 @@ SPACKPACKAGES_VERSION="v2026.06.0"
 ## Space-separated list of spack-packages cherry-picks
 read -r -d '' SPACKPACKAGES_CHERRYPICKS <<- \
 --- || true
-a115a811bdfce4db5298a9ba9b7903ccfb0de101
-20444b8e9382e659360a1446688d10a8c2d2ad31
-f5742718da7bd1d078ddc8423011a82ef2e3c759
+384fd54caf18c6393607bff018853747d02c6e0f
+bd9b4838fbf9e4ca01ad7b6c6df633ddcc750d71
 deb4f17d93dbe012403614245334f7c73fcc086f
 82a6d07a37d13c247e84417055f9cb5b4802ac4f
 47780b2c59a8356c1f13cd7c8d250e3250c15ba8
 28bd1a044251fca35e14ba55d7ddb567deadcdaa
-a7c32f24cd5b69b237dc974804a71326306f4e58
-de97f131df3dbc940151f406afd5c2c1158a660c
-caf013be0ee1594fdbba8feb07ffecc88474a2b0
+72269859719d77f986be7cc752946650d020ac3f
+125ca0c4f3b8bb2c5312c571e27006d9ddc06085
+7a6fa1c4f62f27531c93ecfeedad30181e9616f9
+c72830c64ceda0390b12e0b7ddda6418fa3806be
 75395349957ad785cca50002dffb18bbcb48af27
 acac89d6bb7079412e711a50a3f06681132a2723
 438abd1e09f0cea9cb0ccc7e0326adcd0408196b
 d4fb37cedfb7552a753bdc9c0c4792082f4b46e8
 4dc856a13e9066ca3249a593d351af8cda521fa3
+3dcad5bb860184c91c17b97a9f3b13252d26d309
 ---
 ## Optional hash table with comma-separated file list
 ## For these commits, the cherry-pick will be restricted to the listed files only.
@@ -36,18 +37,19 @@ read -r -d '' SPACKPACKAGES_CHERRYPICKS_FILES <<- \
 ---
 ## Ref: https://github.com/spack/spack-packages/commit/[hash]
 ## [hash]: [description]
-## a115a811bdfce4db5298a9ba9b7903ccfb0de101: github-copilot: new package
-## 20444b8e9382e659360a1446688d10a8c2d2ad31: github-copilot: add v1.0.8
-## f5742718da7bd1d078ddc8423011a82ef2e3c759: gaudi: workaround test-dependency bug with a when
+## 384fd54caf18c6393607bff018853747d02c6e0f: github-copilot: new package
+## bd9b4838fbf9e4ca01ad7b6c6df633ddcc750d71: gaudi: workaround test-dependency bug with a when
 ## deb4f17d93dbe012403614245334f7c73fcc086f: fix: add latest osg-ca-cert
 ## 82a6d07a37d13c247e84417055f9cb5b4802ac4f: osg-ca-certs: depends on gmake and perl, type build
 ## 47780b2c59a8356c1f13cd7c8d250e3250c15ba8: py-pynacl: depends on gmake, type build
 ## 28bd1a044251fca35e14ba55d7ddb567deadcdaa: py-throttler: add v1.2.3
-## a7c32f24cd5b69b237dc974804a71326306f4e58: py-tensorboard: add v2.21.0
-## de97f131df3dbc940151f406afd5c2c1158a660c: TensorFlow: add v2.21.0
-## caf013be0ee1594fdbba8feb07ffecc88474a2b0: Add missing xxd dep
+## 72269859719d77f986be7cc752946650d020ac3f: py-tensorboard: add v2.21.0
+## 125ca0c4f3b8bb2c5312c571e27006d9ddc06085: TensorFlow: add v2.21.0
+## 7a6fa1c4f62f27531c93ecfeedad30181e9616f9: Add missing xxd dep
+## c72830c64ceda0390b12e0b7ddda6418fa3806be: Workaround for macOS arm64 compile bug
 ## 75395349957ad785cca50002dffb18bbcb48af27: py-torch: ensure setuptools is not unnecessarily constrained for 2.10:
 ## acac89d6bb7079412e711a50a3f06681132a2723: cuda: append --allow-unsupported-compiler to CUDAFLAGS for dependent_spec
 ## 438abd1e09f0cea9cb0ccc7e0326adcd0408196b: herwig3: add CT14(?n)lo pdfsets as build-time resources
 ## d4fb37cedfb7552a753bdc9c0c4792082f4b46e8: py-tensorflow: add libclang variant
 ## 4dc856a13e9066ca3249a593d351af8cda521fa3: root: add v6.40.00, v6.40.02
+## 3dcad5bb860184c91c17b97a9f3b13252d26d309: readline: switch url for patch download
diff --git a/spack.sh b/spack.sh
index f3509ca49..842764525 100644
--- a/spack.sh
+++ b/spack.sh
@@ -11,7 +11,7 @@ SPACK_VERSION="v1.2.2"
 read -r -d '' SPACK_CHERRYPICKS <<- \
 --- || true
 292b0dcaba3b2a5e3f9668d205d39fee2c715721
-678e506a95b319c573ba7e84703b06d7275ab80e
+473d1459fba532de0d3d7edc34d27b1432bc90cd
 ---
 ## Optional hash table with comma-separated file list
 read -r -d '' SPACK_CHERRYPICKS_FILES <<- \
@@ -20,4 +20,4 @@ read -r -d '' SPACK_CHERRYPICKS_FILES <<- \
 ## Ref: https://github.com/spack/spack/commit/[hash]
 ## [hash]: [description]
 ## 292b0dcaba3b2a5e3f9668d205d39fee2c715721: fix: write created time field with OCI buildcache config
-## 678e506a95b319c573ba7e84703b06d7275ab80e: fix: don't map prefix to view root for pkgs excluded from view
+## 473d1459fba532de0d3d7edc34d27b1432bc90cd: fix: don't map prefix to view root for pkgs excluded from view