diff --git a/src/OpenFOAM/primitives/DiagTensor/DiagTensor.H b/src/OpenFOAM/primitives/DiagTensor/DiagTensor.H
index c4d141d667..efd21592fb 100644
--- a/src/OpenFOAM/primitives/DiagTensor/DiagTensor.H
+++ b/src/OpenFOAM/primitives/DiagTensor/DiagTensor.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019-2023 OpenCFD Ltd.
+    Copyright (C) 2019-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -92,7 +92,7 @@ public:
     // Constructors
 
         //- Construct initialized to zero
-        inline DiagTensor(const Foam::zero);
+        inline DiagTensor(Foam::zero);
 
         //- Construct given VectorSpace
         template<class Cmpt2>
@@ -123,6 +123,9 @@ public:
 
     // Diagonal access and manipulation
 
+        //- Extract the diagonal as a vector
+        inline Vector<Cmpt> diag() const;
+
         //- The L2-norm squared of the diagonal
         inline scalar diagSqr() const;
 };
diff --git a/src/OpenFOAM/primitives/DiagTensor/DiagTensorI.H b/src/OpenFOAM/primitives/DiagTensor/DiagTensorI.H
index e898e8181d..0590463031 100644
--- a/src/OpenFOAM/primitives/DiagTensor/DiagTensorI.H
+++ b/src/OpenFOAM/primitives/DiagTensor/DiagTensorI.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2020-2023 OpenCFD Ltd.
+    Copyright (C) 2020-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -32,9 +32,9 @@ License
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
 template<class Cmpt>
-inline Foam::DiagTensor<Cmpt>::DiagTensor(const Foam::zero)
+inline Foam::DiagTensor<Cmpt>::DiagTensor(Foam::zero)
 :
-    VectorSpace<DiagTensor<Cmpt>, Cmpt, 3>(Zero)
+    VectorSpace<DiagTensor<Cmpt>, Cmpt, 3>(Foam::zero{})
 {}
 
 
@@ -81,6 +81,13 @@ inline Foam::DiagTensor<Cmpt>::DiagTensor(Istream& is)
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
+template<class Cmpt>
+inline Foam::Vector<Cmpt> Foam::DiagTensor<Cmpt>::diag() const
+{
+    return Vector<Cmpt>(this->xx(), this->yy(), this->zz());
+}
+
+
 template<class Cmpt>
 inline Foam::scalar Foam::DiagTensor<Cmpt>::diagSqr() const
 {
diff --git a/src/OpenFOAM/primitives/SymmTensor/SymmTensor.H b/src/OpenFOAM/primitives/SymmTensor/SymmTensor.H
index 2f38d3e481..acc667eb43 100644
--- a/src/OpenFOAM/primitives/SymmTensor/SymmTensor.H
+++ b/src/OpenFOAM/primitives/SymmTensor/SymmTensor.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019-2023 OpenCFD Ltd.
+    Copyright (C) 2019-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -94,7 +94,7 @@ public:
     // Constructors
 
         //- Construct initialized to zero
-        inline SymmTensor(const Foam::zero);
+        inline SymmTensor(Foam::zero);
 
         //- Construct given VectorSpace of the same rank
         template<class Cmpt2>
@@ -234,6 +234,12 @@ public:
         inline scalar diagSqr() const;
 
 
+    // Characteristics
+
+        //- Is identity tensor?
+        inline bool is_identity(const scalar tol = ROOTVSMALL) const;
+
+
     // Tensor Operations
 
         //- Return non-Hermitian transpose
diff --git a/src/OpenFOAM/primitives/SymmTensor/SymmTensorI.H b/src/OpenFOAM/primitives/SymmTensor/SymmTensorI.H
index 3b654f175f..53ed33fdb1 100644
--- a/src/OpenFOAM/primitives/SymmTensor/SymmTensorI.H
+++ b/src/OpenFOAM/primitives/SymmTensor/SymmTensorI.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019-2023 OpenCFD Ltd.
+    Copyright (C) 2019-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -31,9 +31,9 @@ License
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
 template<class Cmpt>
-inline Foam::SymmTensor<Cmpt>::SymmTensor(const Foam::zero)
+inline Foam::SymmTensor<Cmpt>::SymmTensor(Foam::zero)
 :
-    SymmTensor::vsType(Zero)
+    SymmTensor::vsType(Foam::zero{})
 {}
 
 
@@ -238,6 +238,21 @@ inline Foam::scalar Foam::SymmTensor<Cmpt>::diagSqr() const
 }
 
 
+template<class Cmpt>
+inline bool Foam::SymmTensor<Cmpt>::is_identity(const scalar tol) const
+{
+    return
+    (
+        Foam::mag(xx() - pTraits<Cmpt>::one) < tol
+     && Foam::mag(yy() - pTraits<Cmpt>::one) < tol
+     && Foam::mag(zz() - pTraits<Cmpt>::one) < tol
+     && Foam::mag(xy()) < tol
+     && Foam::mag(xz()) < tol
+     && Foam::mag(yz()) < tol
+    );
+}
+
+
 template<class Cmpt>
 inline Cmpt Foam::SymmTensor<Cmpt>::det() const
 {
diff --git a/src/OpenFOAM/primitives/Tensor/TensorI.H b/src/OpenFOAM/primitives/Tensor/TensorI.H
index 89352d73b2..7c46f93639 100644
--- a/src/OpenFOAM/primitives/Tensor/TensorI.H
+++ b/src/OpenFOAM/primitives/Tensor/TensorI.H
@@ -410,12 +410,12 @@ inline bool Foam::Tensor<Cmpt>::is_identity(const scalar tol) const
 {
     return
     (
-        mag(xx() - pTraits<Cmpt>::one) < tol
-     && mag(yy() - pTraits<Cmpt>::one) < tol
-     && mag(zz() - pTraits<Cmpt>::one) < tol
-     && mag(xy()) < tol && mag(xz()) < tol
-     && mag(yx()) < tol && mag(yz()) < tol
-     && mag(zx()) < tol && mag(zy()) < tol
+        Foam::mag(xx() - pTraits<Cmpt>::one) < tol
+     && Foam::mag(yy() - pTraits<Cmpt>::one) < tol
+     && Foam::mag(zz() - pTraits<Cmpt>::one) < tol
+     && Foam::mag(xy()) < tol && Foam::mag(xz()) < tol
+     && Foam::mag(yx()) < tol && Foam::mag(yz()) < tol
+     && Foam::mag(zx()) < tol && Foam::mag(zy()) < tol
     );
 }
 
diff --git a/src/finiteArea/fields/faPatchFields/constraint/wedge/wedgeFaPatchField.C b/src/finiteArea/fields/faPatchFields/constraint/wedge/wedgeFaPatchField.C
index d3e5c31d78..deded81e75 100644
--- a/src/finiteArea/fields/faPatchFields/constraint/wedge/wedgeFaPatchField.C
+++ b/src/finiteArea/fields/faPatchFields/constraint/wedge/wedgeFaPatchField.C
@@ -29,7 +29,6 @@ License
 #include "wedgeFaPatchField.H"
 #include "transformField.H"
 #include "symmTransform.H"
-#include "diagTensor.H"
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
@@ -138,10 +137,9 @@ template<class Type>
 Foam::tmp<Foam::Field<Type>>
 Foam::wedgeFaPatchField<Type>::snGradTransformDiag() const
 {
-    const diagTensor diagT =
-        0.5*diag(I - refCast<const wedgeFaPatch>(this->patch()).faceT());
+    const auto& rot = refCast<const wedgeFaPatch>(this->patch()).faceT();
 
-    const vector diagV(diagT.xx(), diagT.yy(), diagT.zz());
+    const vector diagV = 0.5*(I - rot).diag();
 
     return tmp<Field<Type>>::New
     (
diff --git a/src/finiteVolume/fields/fvPatchFields/constraint/symmetryPlane/symmetryPlaneFvPatchField.C b/src/finiteVolume/fields/fvPatchFields/constraint/symmetryPlane/symmetryPlaneFvPatchField.C
index b83f6c80a9..4a9705bada 100644
--- a/src/finiteVolume/fields/fvPatchFields/constraint/symmetryPlane/symmetryPlaneFvPatchField.C
+++ b/src/finiteVolume/fields/fvPatchFields/constraint/symmetryPlane/symmetryPlaneFvPatchField.C
@@ -155,9 +155,7 @@ template<class Type>
 Foam::tmp<Foam::Field<Type>>
 Foam::symmetryPlaneFvPatchField<Type>::snGradTransformDiag() const
 {
-    vector nHat(symmetryPlanePatch_.n());
-
-    const vector diag(mag(nHat.x()), mag(nHat.y()), mag(nHat.z()));
+    const vector diag(cmptMag(symmetryPlanePatch_.n()));
 
     return tmp<Field<Type>>::New
     (
diff --git a/src/finiteVolume/fields/fvPatchFields/constraint/wedge/wedgeFvPatchField.C b/src/finiteVolume/fields/fvPatchFields/constraint/wedge/wedgeFvPatchField.C
index 8c2b3eb61c..c8094daa0c 100644
--- a/src/finiteVolume/fields/fvPatchFields/constraint/wedge/wedgeFvPatchField.C
+++ b/src/finiteVolume/fields/fvPatchFields/constraint/wedge/wedgeFvPatchField.C
@@ -30,7 +30,6 @@ License
 #include "wedgeFvPatchField.H"
 #include "transformField.H"
 #include "symmTransform.H"
-#include "diagTensor.H"
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
@@ -152,10 +151,9 @@ template<class Type>
 Foam::tmp<Foam::Field<Type>>
 Foam::wedgeFvPatchField<Type>::snGradTransformDiag() const
 {
-    const diagTensor diagT =
-        0.5*diag(I - refCast<const wedgeFvPatch>(this->patch()).cellT());
+    const auto& rot = refCast<const wedgeFvPatch>(this->patch()).cellT();
 
-    const vector diagV(diagT.xx(), diagT.yy(), diagT.zz());
+    const vector diagV = 0.5*(I - rot).diag();
 
     return tmp<Field<Type>>::New
     (