diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4700cfd1f..bb8d5daca 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -185,6 +185,9 @@ include(cmake/Geometry.cmake)
 # Fluid
 include(cmake/Fluid.cmake)
 
+# Transport
+include(cmake/Transport.cmake)
+
 # Phoebus src
 message("\nConfiguring src")
 add_subdirectory(src)
diff --git a/cmake/Transport.cmake b/cmake/Transport.cmake
new file mode 100644
index 000000000..6e97fb6e5
--- /dev/null
+++ b/cmake/Transport.cmake
@@ -0,0 +1,13 @@
+# © 2021-2025. Triad National Security, LLC. All rights reserved.  This
+# program was produced under U.S. Government contract 89233218CNA000001
+# for Los Alamos National Laboratory (LANL), which is operated by Triad
+# National Security, LLC for the U.S.  Department of Energy/National
+# Nuclear Security Administration. All rights in the program are
+# reserved by Triad National Security, LLC, and the U.S. Department of
+# Energy/National Nuclear Security Administration. The Government is
+# granted for itself and others acting on its behalf a nonexclusive,
+# paid-up, irrevocable worldwide license in this material to reproduce,
+# prepare derivative works, distribute copies to the public, perform
+# publicly and display publicly, and to permit others to do so.
+
+set(MOCMC_NUM_SPECIES 3 CACHE INTEGER "Number of radiation species for MOCMC.")
diff --git a/src/compile_constants.hpp.in b/src/compile_constants.hpp.in
index 4fdf0db20..44c69c8a7 100644
--- a/src/compile_constants.hpp.in
+++ b/src/compile_constants.hpp.in
@@ -16,6 +16,8 @@
 
 #define NCONS_MAX (@MAX_NUMBER_CONSERVED_VARS@)
 
+#define MOCMC_NUM_SPECIES (@MOCMC_NUM_SPECIES@)
+
 #define PHOEBUS_GEOMETRY Geometry::@PHOEBUS_GEOMETRY@
 #define GEOMETRY_MESH @GEOMETRY_MESH@
 #define GEOMETRY_MESH_BLOCK @GEOMETRY_MESH_BLOCK@
diff --git a/src/radiation/radiation.cpp b/src/radiation/radiation.cpp
index cb0cb633e..0ca6f58cb 100644
--- a/src/radiation/radiation.cpp
+++ b/src/radiation/radiation.cpp
@@ -144,20 +144,26 @@ std::shared_ptr<StateDescriptor> Initialize(ParameterInput *pin) {
   }
 
   if (method == "mocmc") {
-    std::string swarm_name = "mocmc";
+    static constexpr auto swarm_name = "mocmc";
     Metadata swarm_metadata({Metadata::Provides});
     physics->AddSwarm(swarm_name, swarm_metadata);
     Metadata real_swarmvalue_metadata({Metadata::Real});
-    physics->AddSwarmValue("t", swarm_name, real_swarmvalue_metadata);
-    physics->AddSwarmValue("mu_lo", swarm_name, real_swarmvalue_metadata);
-    physics->AddSwarmValue("mu_hi", swarm_name, real_swarmvalue_metadata);
-    physics->AddSwarmValue("phi_lo", swarm_name, real_swarmvalue_metadata);
-    physics->AddSwarmValue("phi_hi", swarm_name, real_swarmvalue_metadata);
+    physics->AddSwarmValue(mocmc_core::t::name(), swarm_name, real_swarmvalue_metadata);
+    physics->AddSwarmValue(mocmc_core::mu_lo::name(), swarm_name,
+                           real_swarmvalue_metadata);
+    physics->AddSwarmValue(mocmc_core::mu_hi::name(), swarm_name,
+                           real_swarmvalue_metadata);
+    physics->AddSwarmValue(mocmc_core::phi_lo::name(), swarm_name,
+                           real_swarmvalue_metadata);
+    physics->AddSwarmValue(mocmc_core::phi_hi::name(), swarm_name,
+                           real_swarmvalue_metadata);
     Metadata fourv_swarmvalue_metadata({Metadata::Real}, std::vector<int>{4});
-    physics->AddSwarmValue("ncov", swarm_name, fourv_swarmvalue_metadata);
+    physics->AddSwarmValue(mocmc_core::ncov::name(), swarm_name,
+                           fourv_swarmvalue_metadata);
     Metadata Inu_swarmvalue_metadata({Metadata::Real},
-                                     std::vector<int>{num_species, nu_bins});
-    physics->AddSwarmValue("Inuinv", swarm_name, Inu_swarmvalue_metadata);
+                                     std::vector<int>{MOCMC_NUM_SPECIES, nu_bins});
+    physics->AddSwarmValue(mocmc_core::Inuinv::name(), swarm_name,
+                           Inu_swarmvalue_metadata);
 
     // Boundary temperatures for outflow sample boundary conditions
     const std::string ix1_bc = pin->GetOrAddString("phoebus", "ix1_bc", "None");