From 3307191f2df60d1e60b411516447ed3d61087985 Mon Sep 17 00:00:00 2001
From: Emily Boudreaux <thomas@boudreauxmail.com>
Date: Thu, 17 Sep 2026 10:17:19 -0400
Subject: [PATCH] Keep unrecognized physical runtimes on gravity fallback

---
 .../interface/solver/gravity_subsystem.cppm   | 21 +++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/libmeanfield/interface/solver/gravity_subsystem.cppm b/libmeanfield/interface/solver/gravity_subsystem.cppm
index b6fd8c8..84a7865 100644
--- a/libmeanfield/interface/solver/gravity_subsystem.cppm
+++ b/libmeanfield/interface/solver/gravity_subsystem.cppm
@@ -291,6 +291,16 @@ namespace mean_field::solver::detail {
                 !std::same_as<typename Couplings::Residual, utils::blocks::gravity::poisson::residual>) &&
                ...)> { };
 
+    template <typename Candidate> struct BuiltinStellarGravityProblem : std::false_type { };
+    template <typename Model, typename Discretization>
+    struct BuiltinStellarGravityProblem<equilibrium::StellarEquilibriumProblem<Model, Discretization>>
+        : std::true_type { };
+
+    template <typename Candidate> struct BuiltinPreparedGravityInverse : std::false_type { };
+    template <typename MassBackend, typename Mode, typename Policy>
+    struct BuiltinPreparedGravityInverse<preconditioning::PreparedGravityFieldBlock<MassBackend, Mode, Policy>>
+        : std::true_type { };
+
     [[nodiscard]] inline bool CollectiveGravityApplicationChoice(
         const bool local,
         const MPI_Comm communicator
@@ -306,7 +316,8 @@ namespace mean_field::solver::detail {
 
 export namespace mean_field::solver {
     template <typename Problem>
-        requires std::same_as<typename Problem::PhysicalCoreType, operators::PreparedStellarEquilibriumOperator> &&
+        requires detail::BuiltinStellarGravityProblem<Problem>::value &&
+                 std::same_as<typename Problem::PhysicalCoreType, operators::PreparedStellarEquilibriumOperator> &&
                  detail::SpecificationsLeaveGravityRows<typename operators::CompiledStellarEquilibriumSystem<
                      typename Problem::ModelType>::ContributionJacobianCouplings>::value
     struct GravityCompactOperatorAccess<normalization::NormalizedStellarEquilibriumOperator<Problem>> {
@@ -360,7 +371,13 @@ export namespace mean_field::solver {
                      typename Block::StructureComponent::GravityComponent::ResidualBlocks,
                      utils::blocks::type_list<
                          utils::blocks::gravity::gradient::residual,
-                         utils::blocks::gravity::poisson::residual>>
+                         utils::blocks::gravity::poisson::residual>> &&
+                 requires(const preconditioning::PreparedStellarPreconditioner<Problem, Block> &inverse) {
+                     requires detail::BuiltinPreparedGravityInverse<
+                         std::remove_cvref_t<decltype(inverse.GetGroupedPreconditioner()
+                                                          .GetStructurePreconditioner()
+                                                          .GetGravityPreconditioner())>>::value;
+                 }
     struct GravityCompactInverseAccess<
         normalization::NormalizedStellarEquilibriumOperator<Problem>,
         normalization::