From 594c388a6afc701f0dc1ef1bb84b427a54e37c0d Mon Sep 17 00:00:00 2001
From: EvertBunschoten <evertbun@xs4all.nl>
Date: Wed, 15 Apr 2026 16:57:44 +0200
Subject: [PATCH 1/2] Change nested classes to friend classes

---
 .../drivers/CDiscAdjMultizoneDriver.hpp       | 52 ++++++++++---------
 1 file changed, 28 insertions(+), 24 deletions(-)

diff --git a/SU2_CFD/include/drivers/CDiscAdjMultizoneDriver.hpp b/SU2_CFD/include/drivers/CDiscAdjMultizoneDriver.hpp
index 784fae55a85d..544adaae61cd 100644
--- a/SU2_CFD/include/drivers/CDiscAdjMultizoneDriver.hpp
+++ b/SU2_CFD/include/drivers/CDiscAdjMultizoneDriver.hpp
@@ -36,38 +36,19 @@
  * \brief Block Gauss-Seidel driver for multizone / multiphysics discrete adjoint problems.
  * \ingroup DiscAdj
  */
-class CDiscAdjMultizoneDriver : public CMultizoneDriver {
-
-protected:
 #ifdef CODI_FORWARD_TYPE
   using Scalar = su2double;
 #else
   using Scalar = passivedouble;
 #endif
 
-  class AdjointProduct : public CMatrixVectorProduct<Scalar> {
-  public:
-    CDiscAdjMultizoneDriver* const driver;
-    const unsigned short iZone = 0;
-    mutable unsigned long iInnerIter = 0;
-
-    AdjointProduct(CDiscAdjMultizoneDriver* d, unsigned short i) : driver(d), iZone(i) {}
-
-    inline void operator()(const CSysVector<Scalar> & u, CSysVector<Scalar> & v) const override {
-      driver->SetAllSolutions(iZone, true, u);
-      driver->Iterate(iZone, iInnerIter, true);
-      driver->GetAllSolutions(iZone, true, v);
-      v -= u;
-      ++iInnerIter;
-    }
-  };
+class CDiscAdjMultizoneDriver : public CMultizoneDriver {
 
-  class Identity : public CPreconditioner<Scalar> {
-  public:
-    inline bool IsIdentity() const override { return true; }
-    inline void operator()(const CSysVector<Scalar> & u, CSysVector<Scalar> & v) const override { v = u; }
-  };
+protected:
 
+  friend class AdjointProduct;
+  friend class Identity;
+  
   /*!
    * \brief Kinds of recordings.
    */
@@ -304,3 +285,26 @@ class CDiscAdjMultizoneDriver : public CMultizoneDriver {
   }
 
 };
+
+class AdjointProduct : public CMatrixVectorProduct<Scalar> {
+public:
+  CDiscAdjMultizoneDriver* const driver;
+  const unsigned short iZone = 0;
+  mutable unsigned long iInnerIter = 0;
+
+  AdjointProduct(CDiscAdjMultizoneDriver* d, unsigned short i) : driver(d), iZone(i) {}
+
+  inline void operator()(const CSysVector<Scalar> & u, CSysVector<Scalar> & v) const override {
+    driver->SetAllSolutions(iZone, true, u);
+    driver->Iterate(iZone, iInnerIter, true);
+    driver->GetAllSolutions(iZone, true, v);
+    v -= u;
+    ++iInnerIter;
+  }
+};
+
+class Identity : public CPreconditioner<Scalar> {
+public:
+  inline bool IsIdentity() const override { return true; }
+  inline void operator()(const CSysVector<Scalar> & u, CSysVector<Scalar> & v) const override { v = u; }
+};
\ No newline at end of file

From 2821ba1325e34c748b61e1564d52068bdf53e22a Mon Sep 17 00:00:00 2001
From: EvertBunschoten <evertbun@xs4all.nl>
Date: Wed, 15 Apr 2026 16:58:13 +0200
Subject: [PATCH 2/2] Include discrete adjoint multizone driver in python
 wrapper

---
 SU2_PY/pySU2/pySU2ad.i | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/SU2_PY/pySU2/pySU2ad.i b/SU2_PY/pySU2/pySU2ad.i
index 65ddbfe30369..d0b15fe5cee7 100644
--- a/SU2_PY/pySU2/pySU2ad.i
+++ b/SU2_PY/pySU2/pySU2ad.i
@@ -39,6 +39,7 @@ threads="1"
 %{
 #include "../../Common/include/containers/CPyWrapperMatrixView.hpp"
 #include "../../SU2_CFD/include/drivers/CDiscAdjSinglezoneDriver.hpp"
+#include "../../SU2_CFD/include/drivers/CDiscAdjMultizoneDriver.hpp"
 #include "../../SU2_CFD/include/drivers/CDriver.hpp"
 #include "../../SU2_CFD/include/drivers/CDriverBase.hpp"
 #include "../../SU2_CFD/include/drivers/CMultizoneDriver.hpp"
@@ -98,4 +99,5 @@ const unsigned int ZONE_1 = 1; /*!< \brief Definition of the first grid domain.
 %include "../../SU2_CFD/include/drivers/CSinglezoneDriver.hpp"
 %include "../../SU2_CFD/include/drivers/CMultizoneDriver.hpp"
 %include "../../SU2_CFD/include/drivers/CDiscAdjSinglezoneDriver.hpp"
+%include "../../SU2_CFD/include/drivers/CDiscAdjMultizoneDriver.hpp"
 %include "../../SU2_DEF/include/drivers/CDiscAdjDeformationDriver.hpp"