diff --git a/environments/key4hep-common/packages.yaml b/environments/key4hep-common/packages.yaml
index 69587c5d..e2ffc74b 100644
--- a/environments/key4hep-common/packages.yaml
+++ b/environments/key4hep-common/packages.yaml
@@ -53,6 +53,8 @@ packages:
   xrootd:
     require: +krb5 cxxstd=20
 
+  fmt:
+    require: "@:10"
   # Use the system OpenGL as recommended by spack
   # See https://github.com/key4hep/key4hep-spack/issues/318 and
   # https://github.com/key4hep/key4hep-spack/issues/516
diff --git a/environments/key4hep-dev-external/spack.yaml b/environments/key4hep-dev-external/spack.yaml
new file mode 100644
index 00000000..510d7e0f
--- /dev/null
+++ b/environments/key4hep-dev-external/spack.yaml
@@ -0,0 +1,18 @@
+spack:
+  packages:
+    all:
+      variants:
+        - build_type=RelWithDebInfo
+        - 'cxxstd=20'
+      target: []
+      compiler: []
+
+    boost:
+      require: +atomic+chrono+context+date_time+exception+fiber+filesystem+graph+iostreams+locale+log+math+multithreaded+program_options+python+random+regex+serialization+shared+signals+system+test+thread+timer+wave
+
+  view: false
+  include:
+  - ../key4hep-common/packages.yaml
+
+  specs:
+  - key4hep-external-stack
diff --git a/packages/key4hep-external-stack/package.py b/packages/key4hep-external-stack/package.py
new file mode 100644
index 00000000..e1f9f4f2
--- /dev/null
+++ b/packages/key4hep-external-stack/package.py
@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+
+from datetime import datetime
+
+from spack.pkg.k4.key4hep_stack import Key4hepPackage, install_setup_script
+
+from common import *
+
+
+class Key4hepExternalStack(BundlePackage, Key4hepPackage):
+    """Bundle package that contains a basic external software stack upon which
+    Key4hep can be built
+
+    The packages in this base stack are mainly
+    """
+
+    homepage = "https://cern.ch/key4hep"
+
+    version(datetime.today().strftime("%Y-%m-%d"))
+
+    # this bundle package installs a custom setup script, so
+    # need to add the install phase (which normally does not
+    # exist for a bundle package)
+    phases = ["install"]
+
+    # Some generally useful development tools
+    depends_on("cmake")
+    depends_on("ninja")
+    depends_on("python")
+    depends_on("gdb")
+    depends_on("catch2@3:")
+    depends_on("boost")
+    depends_on("py-pytest")
+
+    # general hep packages
+    depends_on("root")
+    depends_on("geant4")
+    depends_on("pythia8")
+    depends_on("hepmc3")
+    depends_on("evtgen +photos+tauola+pythia8+hepmc3")
+    depends_on("heppdt")
+    depends_on("fastjet")
+
+    # podio dependencies
+    depends_on("py-pyyaml")
+    depends_on("py-tabulate")
+    depends_on("py-jinja2")
+    depends_on("py-graphviz")
+
+    # other general deps
+    depends_on("py-numpy")
+    depends_on("py-scipy")
+
+    # gaudi dependencies
+    depends_on("py-nose")
+    depends_on("cppgsl")
+    depends_on("fmt")
+    depends_on("cppunit")
+    depends_on("gperftools")
+    depends_on("py-networkx")
+    depends_on("py-six")
+    depends_on("range-v3")
+    depends_on("py-pytest-cov")
+    depends_on("jemalloc")
+    depends_on("aida")
+
+    def install(self, spec, prefix):
+        return install_setup_script(self, spec, prefix, "K4_BASE_STACK")