diff --git a/.github/workflows/build-push.yml b/.github/workflows/build-push.yml
index 0c25c17f..679c3e82 100644
--- a/.github/workflows/build-push.yml
+++ b/.github/workflows/build-push.yml
@@ -406,7 +406,7 @@ jobs:
           arch: amd64
           runner: ubuntu-latest
           PLATFORM: linux/amd64
-          target: builder_concretization_default
+          target: builder_concretization_custom
       fail-fast: false
     steps:
       - name: Free Disk Space (Ubuntu)
diff --git a/containers/eic/Dockerfile b/containers/eic/Dockerfile
index 5be9e16a..ff3aa4e0 100644
--- a/containers/eic/Dockerfile
+++ b/containers/eic/Dockerfile
@@ -6,9 +6,9 @@ ARG RUNTIME_IMAGE="debian_stable_base"
 ARG INTERNAL_TAG="master"
 
 ##
-## This docker build follows two tracks, in order to ensure that we build all packages
+## This docker build follows three tracks, in order to ensure that we build all packages
 ## in a builder image, but install them in a runtime image, while at the same time
-## avoiding a expensive filesystem copy operation at the end that breaks layering.
+## avoiding an expensive filesystem copy operation at the end that breaks layering.
 ##
 ## The build is split in an infrequently-changing default environment, upon which
 ## an environment with custom versions (e.g. individual commits) is layered. The
@@ -18,15 +18,20 @@ ARG INTERNAL_TAG="master"
 ## The separation in a builder and runtime image is particularly relevant to end up with
 ## lightweight images for expensive build dependencies, such as for example CUDA.
 ##
-## builder track                         runtime track
-## ----------------------------------------------------------------------
+## builder track:                        runtime track:
+## concretization:     installation:     concretization/installation:
+## ---------------------------------------------------------------------------------------
 ## builder_image                         runtime_image
 ## builder_concretization_default   
-## builder_installation_default     ->   runtime_concretization_default  (copy spack.lock)
-##                                 \->   runtime_installation_default    (from buildcache)
-## builder_concretization_custom
-## builder_installation_custom      ->   runtime_concretization_custom   (copy spack.lock)
-##                                 \->   runtime_installation_custom     (from buildcache)
+##                \->  builder_installation_default
+##                                       runtime_default
+##                                       (copy spack.lock from builder_installation_default)
+##                                       (install via buildcache)
+## \->  builder_concretization_custom
+##                     \->  builder_installation_custom
+##                                       \->   runtime_custom
+##                                             (copy spack.lock from builder_installation_custom)
+##                                             (install via buildcache)
 ##
 
 
@@ -105,14 +110,14 @@ EOF
 
 
 ## ========================================================================================
-## runtime_concretization_default
-## - runtime base with concretization of default versions (taken from equivalent builder)
+## runtime_default
+## - runtime base with installation of default versions (buildcache populated by builder)
 ## ========================================================================================
-FROM ${DOCKER_REGISTRY}${RUNTIME_IMAGE}:${INTERNAL_TAG} AS runtime_concretization_default
+FROM ${DOCKER_REGISTRY}${RUNTIME_IMAGE}:${INTERNAL_TAG} AS runtime_default
 ARG TARGETPLATFORM
 
 # Open Container Initiative labels
-LABEL org.opencontainers.image.title="Electron-Ion Collider runtime concretization image (default configuration, $TARGETPLATFORM)"
+LABEL org.opencontainers.image.title="Electron-Ion Collider runtime image (default configuration, $TARGETPLATFORM)"
 
 ## Copy our default environment
 COPY --from=spack-environment . /opt/spack-environment/
@@ -126,17 +131,6 @@ COPY --from=builder_installation_default \
   /opt/spack-environment/${ENV}/spack.* \
   /opt/spack-environment/${ENV}/
 
-
-## ========================================================================================
-## runtime_installation_default
-## - runtime base with installation of default versions (buildcache populated by builder)
-## ========================================================================================
-FROM runtime_concretization_default AS runtime_installation_default
-ARG TARGETPLATFORM
-
-# Open Container Initiative labels
-LABEL org.opencontainers.image.title="Electron-Ion Collider runtime installation image (default configuration, $TARGETPLATFORM)"
-
 # Installation (default environment, from buildcache)
 RUN --mount=type=cache,target=/var/cache/spack                          \
     --mount=type=secret,id=mirrors,target=/opt/spack/etc/spack/mirrors.yaml \
@@ -155,7 +149,7 @@ EOF
 ## builder_concretization_custom
 ## - builder base with concretization of custom versions
 ## ========================================================================================
-FROM builder_installation_default AS builder_concretization_custom
+FROM builder_concretization_default AS builder_concretization_custom
 ARG TARGETPLATFORM
 
 # Open Container Initiative labels
@@ -241,14 +235,14 @@ EOF
 
 
 ## ========================================================================================
-## runtime_concretization_custom
-## - runtime base with concretization of custom versions (taken from equivalent builder)
+## runtime_custom
+## - runtime base with installation of custom versions (buildcache populated by builder)
 ## ========================================================================================
-FROM runtime_installation_default AS runtime_concretization_custom
+FROM runtime_default AS runtime_custom
 ARG TARGETPLATFORM
 
 # Open Container Initiative labels
-LABEL org.opencontainers.image.title="Electron-Ion Collider runtime concretization image (custom configuration, $TARGETPLATFORM)"
+LABEL org.opencontainers.image.title="Electron-Ion Collider runtime image (custom configuration, $TARGETPLATFORM)"
 
 # Set spack environment directory
 ENV SPACK_ENV=/opt/spack-environment/${ENV}/epic
@@ -263,18 +257,7 @@ COPY --from=builder_installation_custom \
   /opt/spack-environment/packages.yaml \
   /opt/spack-environment/
 
-
-## ========================================================================================
-## runtime_installation_custom
-## - runtime base with installation of custom versions (buildcache populated by builder)
-## ========================================================================================
-FROM runtime_concretization_custom AS runtime_installation_custom
-ARG TARGETPLATFORM
-
-# Open Container Initiative labels
-LABEL org.opencontainers.image.title="Electron-Ion Collider runtime installation image (custom configuration, $TARGETPLATFORM)"
-
-# Installation (default environment, from buildcache)
+# Installation (custom environment, from buildcache)
 RUN --mount=type=cache,target=/var/cache/spack                          \
     --mount=type=secret,id=mirrors,target=/opt/spack/etc/spack/mirrors.yaml \
     <<EOF
@@ -286,13 +269,13 @@ EOF
 
 
 ## ========================================================================================
-## final image, based on runtime_installation_custom
+## final image, based on runtime_custom
 ## ========================================================================================
-FROM runtime_installation_custom AS final
+FROM runtime_custom AS final
 ARG TARGETPLATFORM
 
 # Open Container Initiative labels
-LABEL org.opencontainers.image.title="Electron-Ion Collider runtime installation image (custom configuration, $TARGETPLATFORM)"
+LABEL org.opencontainers.image.title="Electron-Ion Collider runtime image (custom configuration, $TARGETPLATFORM)"
 
 ## Ensure views directories, not symlinks
 RUN <<EOF
diff --git a/docs/architecture.md b/docs/architecture.md
index c74281cb..487f308c 100644
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -4,29 +4,30 @@ The EIC container infrastructure uses a multi-stage build approach with separate
 
 ## Build Strategy
 
-The container build follows a two-track approach:
+The container build follows a three-track approach:
 
 ```mermaid
 flowchart TB
-    subgraph "Builder Track"
+    subgraph "Builder Concretization Track"
         A[builder_image<br/>debian_stable_base] --> B[builder_concretization_default<br/>Concretize spack environment]
-        B --> C[builder_installation_default<br/>Build packages]
-        C --> D[builder_concretization_custom<br/>Concretize custom versions]
-        D --> E[builder_installation_custom<br/>Build custom packages]
+        B --> C[builder_concretization_custom<br/>Concretize custom versions]
+    end
+    
+    subgraph "Builder Installation Track"
+        B --> D[builder_installation_default<br/>Build packages]
+        C --> E[builder_installation_custom<br/>Build custom packages]
     end
     
     subgraph "Runtime Track"
-        F[runtime_image<br/>debian_stable_base] --> G[runtime_concretization_default<br/>Copy spack.lock from builder]
-        G --> H[runtime_installation_default<br/>Install from buildcache]
-        H --> I[runtime_concretization_custom<br/>Copy custom spack.lock]
-        I --> J[runtime_installation_custom<br/>Install custom from buildcache]
-        J --> K[Final Image<br/>eic_ci / eic_xl]
+        F[runtime_image<br/>debian_stable_base] --> G[runtime_default<br/>Copy spack.lock, install from buildcache]
+        G --> H[runtime_custom<br/>Copy custom spack.lock, install from buildcache]
+        H --> K[Final Image<br/>eic_ci / eic_xl]
     end
     
-    C -.->|spack.lock| G
-    C -.->|buildcache| H
-    E -.->|spack.lock| I
-    E -.->|buildcache| J
+    D -.->|spack.lock| G
+    D -.->|buildcache| G
+    E -.->|spack.lock| H
+    E -.->|buildcache| H
 ```
 
 ## Multi-Architecture Support