diff --git a/.github/ci/spack-envs/clangtidy_nopy_ompi_h5_ad2/spack.yaml b/.github/ci/spack-envs/clangtidy_nopy_ompi_h5_ad2/spack.yaml
index 899d626e26..cffff52ef4 100644
--- a/.github/ci/spack-envs/clangtidy_nopy_ompi_h5_ad2/spack.yaml
+++ b/.github/ci/spack-envs/clangtidy_nopy_ompi_h5_ad2/spack.yaml
@@ -13,6 +13,10 @@ spack:
   packages:
     adios2:
       variants: ~zfp ~sz ~png ~dataman ~python ~fortran ~ssc ~shared ~bzip2 ~mgard
+    c-blosc2:
+      # snappy broken on CMake 4.0
+      # fixed snappy not yet deployed to a Spack release
+      variants: ~snappy
     cmake:
       externals:
       - spec: cmake@3.31.5
diff --git a/.github/ci/spack-envs/gcc12_py36_ompi_h5_ad2/spack.yaml b/.github/ci/spack-envs/gcc12_py36_ompi_h5_ad2/spack.yaml
index cb21fb2fbd..2e51e80968 100644
--- a/.github/ci/spack-envs/gcc12_py36_ompi_h5_ad2/spack.yaml
+++ b/.github/ci/spack-envs/gcc12_py36_ompi_h5_ad2/spack.yaml
@@ -12,7 +12,14 @@ spack:
 
   packages:
     adios2:
-      variants: ~zfp ~sz ~png ~dataman ~python ~fortran ~ssc ~shared ~bzip2
+      # mgard not supported on CMake 4.0 due to unresolved compatibility
+      # issue in dependency yaml-cpp
+      # https://github.com/jbeder/yaml-cpp/issues/1352
+      variants: ~zfp ~sz ~png ~dataman ~python ~fortran ~ssc ~shared ~bzip2 ~mgard
+    c-blosc2:
+      # snappy broken on CMake 4.0
+      # fixed snappy not yet deployed to a Spack release
+      variants: ~snappy
     cmake:
       externals:
       - spec: cmake@3.31.5