diff --git a/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C b/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C
index cf15e2f1a5..d1fb66a605 100644
--- a/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C
+++ b/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C
@@ -661,8 +661,8 @@ void countExtrudePatches
     }
     // Synchronise decision. Actual numbers are not important, just make
     // sure that they're > 0 on all processors.
-    Pstream::listCombineReduce(zoneSidePatch, plusEqOp<label>());
-    Pstream::listCombineReduce(zoneZonePatch, plusEqOp<label>());
+    Pstream::listReduce(zoneSidePatch, sumOp<label>());
+    Pstream::listReduce(zoneZonePatch, sumOp<label>());
 }
 
 
diff --git a/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C b/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C
index 64c0b0ef34..ae9d91f0b1 100644
--- a/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C
+++ b/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C
@@ -1081,7 +1081,7 @@ label findCorrespondingRegion
         }
     }
 
-    Pstream::listCombineReduce(cellsInZone, plusEqOp<label>());
+    Pstream::listReduce(cellsInZone, sumOp<label>());
 
     // Pick region with largest overlap of zoneI
     label regionI = findMax(cellsInZone);
diff --git a/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracks.C b/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracks.C
index 754109e162..2202574ad8 100644
--- a/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracks.C
+++ b/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracks.C
@@ -186,7 +186,7 @@ int main(int argc, char *argv[])
         const label maxNProcs = returnReduce(maxIds.size(), maxOp<label>());
         maxIds.resize(maxNProcs, -1);
 
-        Pstream::listCombineReduce(maxIds, maxEqOp<label>());
+        Pstream::listReduce(maxIds, maxOp<label>());
 
         // From ids to count
         const labelList numIds = maxIds + 1;
diff --git a/applications/utilities/postProcessing/miscellaneous/postChannel/channelIndexTemplates.C b/applications/utilities/postProcessing/miscellaneous/postChannel/channelIndexTemplates.C
index e0ca2042b6..5668bcc3cb 100644
--- a/applications/utilities/postProcessing/miscellaneous/postChannel/channelIndexTemplates.C
+++ b/applications/utilities/postProcessing/miscellaneous/postChannel/channelIndexTemplates.C
@@ -40,7 +40,7 @@ Foam::Field<T> Foam::channelIndex::regionSum(const Field<T>& cellField) const
     }
 
     // Global sum
-    Pstream::listCombineReduce(regionField, plusEqOp<T>());
+    Pstream::listReduce(regionField, sumOp<T>());
 
     return regionField;
 }
diff --git a/applications/utilities/preProcessing/createViewFactors/viewFactorModels/raySearchEngine/raySearchEngine/raySearchEngine.C b/applications/utilities/preProcessing/createViewFactors/viewFactorModels/raySearchEngine/raySearchEngine/raySearchEngine.C
index f1a37bbc5f..4f2699517d 100644
--- a/applications/utilities/preProcessing/createViewFactors/viewFactorModels/raySearchEngine/raySearchEngine/raySearchEngine.C
+++ b/applications/utilities/preProcessing/createViewFactors/viewFactorModels/raySearchEngine/raySearchEngine/raySearchEngine.C
@@ -229,7 +229,7 @@ void Foam::VF::raySearchEngine::createAgglomeration(const IOobject& io)
     Pstream::allGatherList(allSf_);
     Pstream::allGatherList(allAgg_);
 
-    Pstream::listCombineGather(patchAreas_, plusEqOp<scalar>());
+    Pstream::listGather(patchAreas_, sumOp<scalar>());
     Pstream::broadcast(patchAreas_);
 
     globalNumbering_ = globalIndex(nCoarseFace_);
@@ -262,8 +262,11 @@ void Foam::VF::raySearchEngine::createGeometry()
     Pstream::allGatherList(allCf_);
     Pstream::allGatherList(allSf_);
 
-    Pstream::listCombineGather(patchAreas_, plusEqOp<scalar>());
-    Pstream::broadcast(patchAreas_);
+    // Pstream::listCombineGather(patchAreas_, plusEqOp<scalar>());
+    // Pstream::broadcast(patchAreas_);
+
+    // Basic type and op_sum, so can use listReduce (ie, mpiAllReduce)
+    Pstream::listReduce(patchAreas_, sumOp<scalar>());
 
     globalNumbering_ = globalIndex(nFace_);
 }
diff --git a/applications/utilities/preProcessing/setFields/setFields.C b/applications/utilities/preProcessing/setFields/setFields.C
index 276b36c2f3..44778b680a 100644
--- a/applications/utilities/preProcessing/setFields/setFields.C
+++ b/applications/utilities/preProcessing/setFields/setFields.C
@@ -407,7 +407,7 @@ bool setFaceFieldType
             }
         }
 
-        Pstream::listCombineReduce(nChanged, plusEqOp<label>());
+        Pstream::listReduce(nChanged, sumOp<label>());
 
         auto& fieldBf = field.boundaryFieldRef();
 
diff --git a/src/dynamicMesh/motionSolvers/displacement/pointSmoothing/hexMeshSmootherMotionSolver.C b/src/dynamicMesh/motionSolvers/displacement/pointSmoothing/hexMeshSmootherMotionSolver.C
index d8964afef6..2b28c6e06d 100644
--- a/src/dynamicMesh/motionSolvers/displacement/pointSmoothing/hexMeshSmootherMotionSolver.C
+++ b/src/dynamicMesh/motionSolvers/displacement/pointSmoothing/hexMeshSmootherMotionSolver.C
@@ -464,7 +464,7 @@ Foam::labelList Foam::hexMeshSmootherMotionSolver::countZeroOrPos
         }
     }
 
-    Pstream::listCombineReduce(n, plusEqOp<label>());
+    Pstream::listReduce(n, sumOp<label>());
     return n;
 }
 
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
index 73501db8cf..380bc50803 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
@@ -440,7 +440,7 @@ Foam::scalar Foam::hexRef8::getLevel0EdgeLength() const
 
     // Get the minimum per level over all processors. Note minimum so if
     // cells are not cubic we use the smallest edge side.
-    Pstream::listCombineReduce(typEdgeLenSqr, minEqOp<scalar>());
+    Pstream::listReduce(typEdgeLenSqr, minOp<scalar>());
 
     if (debug)
     {
@@ -474,7 +474,7 @@ Foam::scalar Foam::hexRef8::getLevel0EdgeLength() const
         }
     }
 
-    Pstream::listCombineReduce(maxEdgeLenSqr, maxEqOp<scalar>());
+    Pstream::listReduce(maxEdgeLenSqr, maxOp<scalar>());
 
     if (debug)
     {
diff --git a/src/finiteVolume/fvMesh/fvMeshSubset/fvMeshSubset.C b/src/finiteVolume/fvMesh/fvMeshSubset/fvMeshSubset.C
index 839d102a17..2c5e8ec419 100644
--- a/src/finiteVolume/fvMesh/fvMeshSubset/fvMeshSubset.C
+++ b/src/finiteVolume/fvMesh/fvMeshSubset/fvMeshSubset.C
@@ -1108,7 +1108,7 @@ void Foam::fvMeshSubset::reset
         // Get patch sizes (up to nextPatchID).
         // Note that up to nextPatchID the globalPatchMap is an identity so
         // no need to index through that.
-        Pstream::listCombineReduce(globalPatchSizes, plusEqOp<label>());
+        Pstream::listReduce(globalPatchSizes, sumOp<label>());
 
         // Now all processors have all the patchnames.
         // Decide: if all processors have the same patch names and size is zero
diff --git a/src/functionObjects/field/Curle/Curle.C b/src/functionObjects/field/Curle/Curle.C
index 6b53be0723..0ee78d9200 100644
--- a/src/functionObjects/field/Curle/Curle.C
+++ b/src/functionObjects/field/Curle/Curle.C
@@ -222,7 +222,7 @@ bool Foam::functionObjects::Curle::execute()
 
     pDash /= 4*mathematical::pi;
 
-    Pstream::listCombineReduce(pDash, plusEqOp<scalar>());
+    Pstream::listReduce(pDash, sumOp<scalar>());
 
     if (surfaceWriterPtr_)
     {
diff --git a/src/functionObjects/field/columnAverage/columnAverageTemplates.C b/src/functionObjects/field/columnAverage/columnAverageTemplates.C
index 2bba02a3dc..aa7cc893e9 100644
--- a/src/functionObjects/field/columnAverage/columnAverageTemplates.C
+++ b/src/functionObjects/field/columnAverage/columnAverageTemplates.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018-2024 OpenCFD Ltd.
+    Copyright (C) 2018-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -88,8 +88,8 @@ bool Foam::functionObjects::columnAverage::columnAverageField
         }
 
         // Global sum
-        Pstream::listCombineReduce(regionField, plusEqOp<Type>());
-        Pstream::listCombineReduce(regionCount, plusEqOp<label>());
+        Pstream::listReduce(regionField, sumOp<Type>());
+        Pstream::listReduce(regionCount, sumOp<label>());
 
         forAll(regionField, regioni)
         {
diff --git a/src/functionObjects/field/extractEulerianParticles/extractEulerianParticles/extractEulerianParticles.C b/src/functionObjects/field/extractEulerianParticles/extractEulerianParticles/extractEulerianParticles.C
index c8e2c76cb5..bba3209e63 100644
--- a/src/functionObjects/field/extractEulerianParticles/extractEulerianParticles/extractEulerianParticles.C
+++ b/src/functionObjects/field/extractEulerianParticles/extractEulerianParticles/extractEulerianParticles.C
@@ -329,7 +329,7 @@ void Foam::functionObjects::extractEulerianParticles::calculateAddressing
 
     // Create map from new regions to slots in particles list
     // - filter through new-to-new addressing to identify new particles
-    Pstream::listCombineReduce(newToNewRegion, maxEqOp<label>());
+    Pstream::listReduce(newToNewRegion, maxOp<label>());
 
     label nParticle = -1;
     labelHashSet newRegions;
@@ -348,7 +348,7 @@ void Foam::functionObjects::extractEulerianParticles::calculateAddressing
 
     // Accumulate old region data or create a new particle if there is no
     // mapping from the old-to-new region
-    Pstream::listCombineReduce(oldToNewRegion, maxEqOp<label>());
+    Pstream::listReduce(oldToNewRegion, maxOp<label>());
 
     List<eulerianParticle> newParticles(newRegionToParticleMap.size());
     forAll(oldToNewRegion, oldRegioni)
diff --git a/src/functionObjects/field/histogram/histogramModels/equalBinWidth/equalBinWidth.C b/src/functionObjects/field/histogram/histogramModels/equalBinWidth/equalBinWidth.C
index 790e6213c5..e8d40cb54e 100644
--- a/src/functionObjects/field/histogram/histogramModels/equalBinWidth/equalBinWidth.C
+++ b/src/functionObjects/field/histogram/histogramModels/equalBinWidth/equalBinWidth.C
@@ -155,8 +155,8 @@ bool Foam::histogramModels::equalBinWidth::write(const bool log)
             dataCount[bini]++;
         }
     }
-    Pstream::listCombineGather(dataNormalised, plusEqOp<scalar>());
-    Pstream::listCombineGather(dataCount, plusEqOp<label>());
+    Pstream::listGather(dataNormalised, sumOp<scalar>());
+    Pstream::listGather(dataCount, sumOp<label>());
 
 
     // Write histogram data
diff --git a/src/functionObjects/field/histogram/histogramModels/unequalBinWidth/unequalBinWidth.C b/src/functionObjects/field/histogram/histogramModels/unequalBinWidth/unequalBinWidth.C
index 658c54bd13..aec3f84f0b 100644
--- a/src/functionObjects/field/histogram/histogramModels/unequalBinWidth/unequalBinWidth.C
+++ b/src/functionObjects/field/histogram/histogramModels/unequalBinWidth/unequalBinWidth.C
@@ -129,8 +129,8 @@ bool Foam::histogramModels::unequalBinWidth::write(const bool log)
             }
         }
     }
-    Pstream::listCombineGather(dataNormalised, plusEqOp<scalar>());
-    Pstream::listCombineGather(dataCount, plusEqOp<label>());
+    Pstream::listGather(dataNormalised, sumOp<scalar>());
+    Pstream::listGather(dataCount, sumOp<label>());
 
 
     // Write histogram data
diff --git a/src/functionObjects/forces/propellerInfo/propellerInfo.C b/src/functionObjects/forces/propellerInfo/propellerInfo.C
index b080d929a3..18a47b728a 100644
--- a/src/functionObjects/forces/propellerInfo/propellerInfo.C
+++ b/src/functionObjects/forces/propellerInfo/propellerInfo.C
@@ -791,7 +791,7 @@ Foam::tmp<Foam::Field<Type>> Foam::functionObjects::propellerInfo::interpolate
         }
     }
 
-    Pstream::listCombineReduce(field, maxEqOp<Type>());
+    Pstream::listReduce(field, maxOp<Type>());
 
     return tfield;
 }
diff --git a/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleZoneInfo/ParticleZoneInfo.C b/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleZoneInfo/ParticleZoneInfo.C
index 522e94c35b..dcd6e8effe 100644
--- a/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleZoneInfo/ParticleZoneInfo.C
+++ b/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleZoneInfo/ParticleZoneInfo.C
@@ -365,7 +365,7 @@ void Foam::ParticleZoneInfo<CloudType>::write()
     {
         // Find number of particles per proc
         labelList allMaxIDs(maxIDs_);
-        Pstream::listCombineReduce(allMaxIDs, maxEqOp<label>());
+        Pstream::listReduce(allMaxIDs, maxOp<label>());
 
         // Combine into single list
         label n = returnReduce(data_.size(), sumOp<label>());
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/CellZoneInjection/CellZoneInjection.C b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/CellZoneInjection/CellZoneInjection.C
index 5ee1a9e6ff..5e2ed632cc 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/CellZoneInjection/CellZoneInjection.C
+++ b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/CellZoneInjection/CellZoneInjection.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2015-2023 OpenCFD Ltd.
+    Copyright (C) 2015-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -121,7 +121,7 @@ void Foam::CellZoneInjection<CloudType>::setPositions
         globalPositions.range(myProci)
     ) = positions;
 
-    Pstream::listCombineReduce(allPositions, minEqOp<point>());
+    Pstream::listReduce(allPositions, minOp<point>());
 
     // Gather local cell tet and tet-point Ids, but leave non-local ids set -1
     SubList<label>
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/LocalInteraction/LocalInteraction.C b/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/LocalInteraction/LocalInteraction.C
index 440103171a..5a52be2cb1 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/LocalInteraction/LocalInteraction.C
+++ b/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/LocalInteraction/LocalInteraction.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2015-2020 OpenCFD Ltd.
+    Copyright (C) 2015-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -372,28 +372,28 @@ void Foam::LocalInteraction<CloudType>::info()
     labelListList npe(nEscape_);
     forAll(npe, i)
     {
-        Pstream::listCombineGather(npe[i], plusEqOp<label>());
+        Pstream::listGather(npe[i], sumOp<label>());
         npe[i] = npe[i] + npe0[i];
     }
 
     scalarListList mpe(massEscape_);
     forAll(mpe, i)
     {
-        Pstream::listCombineGather(mpe[i], plusEqOp<scalar>());
+        Pstream::listGather(mpe[i], sumOp<scalar>());
         mpe[i] = mpe[i] + mpe0[i];
     }
 
     labelListList nps(nStick_);
     forAll(nps, i)
     {
-        Pstream::listCombineGather(nps[i], plusEqOp<label>());
+        Pstream::listGather(nps[i], sumOp<label>());
         nps[i] = nps[i] + nps0[i];
     }
 
     scalarListList mps(massStick_);
     forAll(nps, i)
     {
-        Pstream::listCombineGather(mps[i], plusEqOp<scalar>());
+        Pstream::listGather(mps[i], sumOp<scalar>());
         mps[i] = mps[i] + mps0[i];
     }
 
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/RecycleInteraction/RecycleInteraction.C b/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/RecycleInteraction/RecycleInteraction.C
index 78501a00a2..e185e16034 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/RecycleInteraction/RecycleInteraction.C
+++ b/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/RecycleInteraction/RecycleInteraction.C
@@ -379,28 +379,28 @@ void Foam::RecycleInteraction<CloudType>::info()
 
     forAll(npr, i)
     {
-        Pstream::listCombineGather(npr[i], plusEqOp<label>());
+        Pstream::listGather(npr[i], sumOp<label>());
         npr[i] = npr[i] + npr0[i];
     }
 
     scalarListList mpr(massRemoved_);
     forAll(mpr, i)
     {
-        Pstream::listCombineGather(mpr[i], plusEqOp<scalar>());
+        Pstream::listGather(mpr[i], sumOp<scalar>());
         mpr[i] = mpr[i] + mpr0[i];
     }
 
     labelListList npi(nInjected_);
     forAll(npi, i)
     {
-        Pstream::listCombineGather(npi[i], plusEqOp<label>());
+        Pstream::listGather(npi[i], sumOp<label>());
         npi[i] = npi[i] + npi0[i];
     }
 
     scalarListList mpi(massInjected_);
     forAll(mpi, i)
     {
-        Pstream::listCombineGather(mpi[i], plusEqOp<scalar>());
+        Pstream::listGather(mpi[i], sumOp<scalar>());
         mpi[i] = mpi[i] + mpi0[i];
     }
 
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/StandardWallInteraction/StandardWallInteraction.C b/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/StandardWallInteraction/StandardWallInteraction.C
index 5f9f1033a7..00ca30c613 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/StandardWallInteraction/StandardWallInteraction.C
+++ b/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/StandardWallInteraction/StandardWallInteraction.C
@@ -285,28 +285,28 @@ void Foam::StandardWallInteraction<CloudType>::info()
 
     forAll(npe, i)
     {
-        Pstream::listCombineGather(npe[i], plusEqOp<label>());
+        Pstream::listGather(npe[i], sumOp<label>());
         npe[i] = npe[i] + npe0[i];
     }
 
     scalarListList mpe(massEscape_);
     forAll(mpe, i)
     {
-        Pstream::listCombineGather(mpe[i], plusEqOp<scalar>());
+        Pstream::listGather(mpe[i], sumOp<scalar>());
         mpe[i] = mpe[i] + mpe0[i];
     }
 
     labelListList nps(nStick_);
     forAll(nps, i)
     {
-        Pstream::listCombineGather(nps[i], plusEqOp<label>());
+        Pstream::listGather(nps[i], sumOp<label>());
         nps[i] = nps[i] + nps0[i];
     }
 
     scalarListList mps(massStick_);
     forAll(nps, i)
     {
-        Pstream::listCombineGather(mps[i], plusEqOp<scalar>());
+        Pstream::listGather(mps[i], sumOp<scalar>());
         mps[i] = mps[i] + mps0[i];
     }
 
diff --git a/src/lumpedPointMotion/movement/lumpedPointMovement.C b/src/lumpedPointMotion/movement/lumpedPointMovement.C
index 524e2be769..f31f4dc907 100644
--- a/src/lumpedPointMotion/movement/lumpedPointMovement.C
+++ b/src/lumpedPointMotion/movement/lumpedPointMovement.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016-2024 OpenCFD Ltd.
+    Copyright (C) 2016-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -878,7 +878,7 @@ Foam::List<Foam::scalar> Foam::lumpedPointMovement::areas
         }
     }
 
-    Pstream::listCombineReduce(zoneAreas, plusEqOp<scalar>());
+    Pstream::listReduce(zoneAreas, sumOp<scalar>());
 
     return zoneAreas;
 }
@@ -1006,8 +1006,8 @@ bool Foam::lumpedPointMovement::forcesAndMoments
         Info<<"No pressure field" << endl;
     }
 
-    Pstream::listCombineReduce(forces, plusEqOp<vector>());
-    Pstream::listCombineReduce(moments, plusEqOp<vector>());
+    Pstream::listReduce(forces, sumOp<vector>());
+    Pstream::listReduce(moments, sumOp<vector>());
 
     return true;
 }
diff --git a/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C b/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C
index ed4e8cc967..5e3bafccad 100644
--- a/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C
+++ b/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C
@@ -2050,7 +2050,7 @@ Foam::autoPtr<Foam::mapDistributePolyMesh> Foam::meshRefinement::balance
             labelList nProcCells(distributor.countCells(distribution));
             Pout<< "Wanted distribution:" << nProcCells << endl;
 
-            Pstream::listCombineReduce(nProcCells, plusEqOp<label>());
+            Pstream::listReduce(nProcCells, sumOp<label>());
 
             Pout<< "Wanted resulting decomposition:" << endl;
             forAll(nProcCells, proci)
@@ -3611,7 +3611,7 @@ const
             nCells[cellLevel[celli]]++;
         }
 
-        Pstream::listCombineGather(nCells, plusEqOp<label>());
+        Pstream::listGather(nCells, sumOp<label>());
 
         /// Pstream::broadcast(nCells);
         if (Pstream::master())
diff --git a/src/mesh/snappyHexMesh/meshRefinement/meshRefinementBaffles.C b/src/mesh/snappyHexMesh/meshRefinement/meshRefinementBaffles.C
index 3afa51b1e3..2c92d2f059 100644
--- a/src/mesh/snappyHexMesh/meshRefinement/meshRefinementBaffles.C
+++ b/src/mesh/snappyHexMesh/meshRefinement/meshRefinementBaffles.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2014 OpenFOAM Foundation
-    Copyright (C) 2015-2024 OpenCFD Ltd.
+    Copyright (C) 2015-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -867,7 +867,7 @@ Foam::autoPtr<Foam::mapPolyMesh> Foam::meshRefinement::createZoneBaffles
 
         if (nTotalBaffles > 0)
         {
-            Pstream::listCombineReduce(nBaffles, plusEqOp<label>());
+            Pstream::listReduce(nBaffles, sumOp<label>());
 
             Info<< nl
                 << setf(ios_base::left)
@@ -2001,7 +2001,7 @@ void Foam::meshRefinement::findCellZoneTopo
     // - region numbers are identical on all processors
     // - keepRegion is identical ,,
     // - cellZones are identical ,,
-    Pstream::listCombineReduce(regionToCellZone, maxEqOp<label>());
+    Pstream::listReduce(regionToCellZone, maxOp<label>());
 
 
     // Find the region containing the keepPoint
@@ -2051,7 +2051,7 @@ void Foam::meshRefinement::findCellZoneTopo
         // - cellZones are identical ,,
         // This done at top of loop to account for geometric matching
         // not being synchronised.
-        Pstream::listCombineReduce(regionToCellZone, maxEqOp<label>());
+        Pstream::listReduce(regionToCellZone, maxOp<label>());
 
 
         bool changed = false;
diff --git a/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyRefineDriver.C b/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyRefineDriver.C
index bdb55c6faf..6381b3733c 100644
--- a/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyRefineDriver.C
+++ b/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyRefineDriver.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
-    Copyright (C) 2015-2024 OpenCFD Ltd.
+    Copyright (C) 2015-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -3403,9 +3403,9 @@ void Foam::snappyRefineDriver::deleteSmallRegions
         nCellsPerRegion[regioni]++;
         nCellsPerZone[zonei]++;
     }
-    Pstream::listCombineReduce(nCellsPerRegion, plusEqOp<label>());
-    Pstream::listCombineReduce(regionToZone, maxEqOp<label>());
-    Pstream::listCombineReduce(nCellsPerZone, plusEqOp<label>());
+    Pstream::listReduce(nCellsPerRegion, sumOp<label>());
+    Pstream::listReduce(regionToZone, maxOp<label>());
+    Pstream::listReduce(nCellsPerZone, sumOp<label>());
 
 
     // Mark small regions. Note that all processors have the same information
diff --git a/src/meshTools/topoSet/faceZoneSources/planeToFaceZone/planeToFaceZone.C b/src/meshTools/topoSet/faceZoneSources/planeToFaceZone/planeToFaceZone.C
index 273cbfd8ac..e9132b3e5a 100644
--- a/src/meshTools/topoSet/faceZoneSources/planeToFaceZone/planeToFaceZone.C
+++ b/src/meshTools/topoSet/faceZoneSources/planeToFaceZone/planeToFaceZone.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2020 OpenFOAM Foundation
-    Copyright (C) 2020-2022 OpenCFD Ltd.
+    Copyright (C) 2020-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -258,7 +258,7 @@ void Foam::planeToFaceZone::combine(faceZoneSet& fzSet, const bool add) const
             {
                 ++ regionNFaces[regioni];
             }
-            Pstream::listCombineReduce(regionNFaces, plusEqOp<label>());
+            Pstream::listReduce(regionNFaces, sumOp<label>());
 
             Info<< "    Found " << nRegions << " contiguous regions with "
                 << regionNFaces << " faces" << endl;
@@ -281,8 +281,8 @@ void Foam::planeToFaceZone::combine(faceZoneSet& fzSet, const bool add) const
                 regionWeights[regioni] += w;
                 regionCentres[regioni] += w*c;
             }
-            Pstream::listCombineGather(regionWeights, plusEqOp<scalar>());
-            Pstream::listCombineGather(regionCentres, plusEqOp<point>());
+            Pstream::listGather(regionWeights, sumOp<scalar>());
+            Pstream::listGather(regionCentres, sumOp<point>());
 
             if (Pstream::master())
             {
diff --git a/src/optimisation/adjointOptimisation/adjoint/optimisation/updateMethod/MMA/MMA.C b/src/optimisation/adjointOptimisation/adjoint/optimisation/updateMethod/MMA/MMA.C
index 4c29943d2d..2777f8d425 100644
--- a/src/optimisation/adjointOptimisation/adjoint/optimisation/updateMethod/MMA/MMA.C
+++ b/src/optimisation/adjointOptimisation/adjoint/optimisation/updateMethod/MMA/MMA.C
@@ -597,7 +597,7 @@ void Foam::MMA::computeNewtonDirection()
     if (globalSum_)
     {
         reduce(lhs, sumOp<scalarSquareMatrix>());
-        Pstream::listCombineAllGather(rhs, plusEqOp<scalar>());
+        Pstream::listReduce(rhs, sumOp<scalar>());
     }
 
     // Add remaining parts from deltaLamdaYTilda and the deltaZ eqn
diff --git a/src/optimisation/adjointOptimisation/adjoint/parameterization/NURBS/NURBS3DVolume/NURBS3DVolume/NURBS3DVolume.C b/src/optimisation/adjointOptimisation/adjoint/parameterization/NURBS/NURBS3DVolume/NURBS3DVolume/NURBS3DVolume.C
index e467948c4a..052396e975 100644
--- a/src/optimisation/adjointOptimisation/adjoint/parameterization/NURBS/NURBS3DVolume/NURBS3DVolume/NURBS3DVolume.C
+++ b/src/optimisation/adjointOptimisation/adjoint/parameterization/NURBS/NURBS3DVolume/NURBS3DVolume/NURBS3DVolume.C
@@ -1181,7 +1181,7 @@ Foam::vectorField Foam::NURBS3DVolume::computeControlPointSensitivities
     }
 
     // Sum contributions from all processors
-    Pstream::listCombineReduce(controlPointDerivs, plusEqOp<vector>());
+    Pstream::listReduce(controlPointDerivs, sumOp<vector>());
 
     return controlPointDerivs;
 }
@@ -1266,7 +1266,7 @@ Foam::vectorField Foam::NURBS3DVolume::computeControlPointSensitivities
         }
     }
     // Sum contributions from all processors
-    Pstream::listCombineReduce(controlPointDerivs, plusEqOp<vector>());
+    Pstream::listReduce(controlPointDerivs, sumOp<vector>());
 
     return controlPointDerivs;
 }
diff --git a/src/overset/cellCellStencil/cellVolumeWeight/cellVolumeWeightCellCellStencil.C b/src/overset/cellCellStencil/cellVolumeWeight/cellVolumeWeightCellCellStencil.C
index fd04966eff..602d31b075 100644
--- a/src/overset/cellCellStencil/cellVolumeWeight/cellVolumeWeightCellCellStencil.C
+++ b/src/overset/cellCellStencil/cellVolumeWeight/cellVolumeWeightCellCellStencil.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2014-2023 OpenCFD Ltd.
+    Copyright (C) 2014-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -227,7 +227,7 @@ void Foam::cellCellStencils::cellVolumeWeight::findHoles
     {
         // Synchronise region status on processors
         // (could instead swap status through processor patches)
-        Pstream::listCombineReduce(regionType, maxEqOp<label>());
+        Pstream::listReduce(regionType, maxOp<label>());
 
         // Communicate region status through interpolative cells
         labelList cellRegionType(labelUIndList(regionType, cellRegion));
@@ -602,7 +602,7 @@ bool Foam::cellCellStencils::cellVolumeWeight::update()
     {
         nCellsPerZone[zoneID[cellI]]++;
     }
-    Pstream::listCombineReduce(nCellsPerZone, plusEqOp<label>());
+    Pstream::listReduce(nCellsPerZone, sumOp<label>());
 
     Info<< typeName << " : detected " << nZones
         << " mesh regions" << nl << endl;
diff --git a/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C b/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C
index f606f5bdd4..c09703ec54 100644
--- a/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C
+++ b/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2023 OpenCFD Ltd.
+    Copyright (C) 2017-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -1107,7 +1107,7 @@ void Foam::cellCellStencils::inverseDistance::findHoles
     {
         // Synchronise region status on processors
         // (could instead swap status through processor patches)
-        Pstream::listCombineReduce(regionType, maxEqOp<label>());
+        Pstream::listReduce(regionType, maxOp<label>());
 
         DebugInfo<< FUNCTION_NAME << " : Gathered region type" << endl;
 
@@ -1801,7 +1801,7 @@ bool Foam::cellCellStencils::inverseDistance::update()
     {
         nCellsPerZone[zoneID[cellI]]++;
     }
-    Pstream::listCombineReduce(nCellsPerZone, plusEqOp<label>());
+    Pstream::listReduce(nCellsPerZone, sumOp<label>());
 
     const boundBox& allBb = mesh_.bounds();
 
diff --git a/src/overset/cellCellStencil/trackingInverseDistance/trackingInverseDistanceCellCellStencil.C b/src/overset/cellCellStencil/trackingInverseDistance/trackingInverseDistanceCellCellStencil.C
index 73d421c58f..07f3c25436 100644
--- a/src/overset/cellCellStencil/trackingInverseDistance/trackingInverseDistanceCellCellStencil.C
+++ b/src/overset/cellCellStencil/trackingInverseDistance/trackingInverseDistanceCellCellStencil.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2023 OpenCFD Ltd.
+    Copyright (C) 2017-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -519,7 +519,7 @@ Foam::cellCellStencils::trackingInverseDistance::trackingInverseDistance
     {
         nCellsPerZone[zoneID[celli]]++;
     }
-    Pstream::listCombineReduce(nCellsPerZone, plusEqOp<label>());
+    Pstream::listReduce(nCellsPerZone, sumOp<label>());
 
     meshParts_.setSize(nZones);
     forAll(meshParts_, zonei)
diff --git a/src/overset/regionsToCell/findRefCells.C b/src/overset/regionsToCell/findRefCells.C
index 0704f355ba..fc5f942847 100644
--- a/src/overset/regionsToCell/findRefCells.C
+++ b/src/overset/regionsToCell/findRefCells.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2016 OpenCFD Ltd.
+    Copyright (C) 2016,2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -188,7 +188,7 @@ void Foam::setRefCells
             }
         }
 
-        Pstream::listCombineReduce(hasRef, plusEqOp<label>());
+        Pstream::listReduce(hasRef, sumOp<label>());
 
         forAll(hasRef, regionI)
         {
diff --git a/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C b/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C
index b91df7c6d6..f1fa4f415c 100644
--- a/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C
+++ b/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2017-2024 OpenCFD Ltd.
+    Copyright (C) 2017-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -420,8 +420,8 @@ void Foam::multiLevelDecomp::decompose
             );
 
             label nPoints = returnReduce(domainPoints.size(), sumOp<label>());
+            Pstream::listReduce(nOutsideConnections, sumOp<label>());
 
-            Pstream::listCombineReduce(nOutsideConnections, plusEqOp<label>());
             label nPatches = 0;
             label nFaces = 0;
             for (const label nConnect : nOutsideConnections)
@@ -528,11 +528,7 @@ void Foam::multiLevelDecomp::decompose
                 }
 
                 reduce(nPoints, sumOp<label>());
-                Pstream::listCombineReduce
-                (
-                    nOutsideConnections,
-                    plusEqOp<label>()
-                );
+                Pstream::listReduce(nOutsideConnections, sumOp<label>());
 
                 label nPatches = 0;
                 label nFaces = 0;
diff --git a/src/regionModels/regionModel/singleLayerRegion/singleLayerRegion.C b/src/regionModels/regionModel/singleLayerRegion/singleLayerRegion.C
index 94f6598400..207d1c0a48 100644
--- a/src/regionModels/regionModel/singleLayerRegion/singleLayerRegion.C
+++ b/src/regionModels/regionModel/singleLayerRegion/singleLayerRegion.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -144,7 +144,7 @@ void Foam::regionModels::singleLayerRegion::initialise()
         }
     }
 
-    Pstream::listCombineReduce(passivePatchIDs_, maxEqOp<label>());
+    Pstream::listReduce(passivePatchIDs_, maxOp<label>());
 
     magSf.field() = 0.5*(magSf + passiveMagSf);
     magSf.correctBoundaryConditions();
diff --git a/src/sampling/sampledSet/cloud/cloudSet.C b/src/sampling/sampledSet/cloud/cloudSet.C
index 42045d473c..3447facc9b 100644
--- a/src/sampling/sampledSet/cloud/cloudSet.C
+++ b/src/sampling/sampledSet/cloud/cloudSet.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2016 OpenCFD Ltd.
+    Copyright (C) 2016-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -84,8 +84,8 @@ void Foam::cloudSet::calcSamples
             minFoundProc[i] = foundProc[i];
         }
     }
-    Pstream::listCombineReduce(minFoundProc, minEqOp<label>());
-    Pstream::listCombineReduce(maxFoundProc, maxEqOp<label>());
+    Pstream::listReduce(minFoundProc, minOp<label>());
+    Pstream::listReduce(maxFoundProc, maxOp<label>());
 
 
     DynamicField<point> missingPoints(sampleCoords_.size());
diff --git a/src/sampling/surface/distanceSurface/distanceSurfaceFilter.C b/src/sampling/surface/distanceSurface/distanceSurfaceFilter.C
index 58d3892748..739a802f4e 100644
--- a/src/sampling/surface/distanceSurface/distanceSurfaceFilter.C
+++ b/src/sampling/surface/distanceSurface/distanceSurfaceFilter.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2020-2022 OpenCFD Ltd.
+    Copyright (C) 2020-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -142,8 +142,8 @@ void Foam::distanceSurface::filterKeepLargestRegion
         }
     }
 
-    // Sum totals from all processors
-    Pstream::listCombineGather(nCutsPerRegion, plusEqOp<label>());
+    // Sum totals from all processors (onto the master)
+    Pstream::listGather(nCutsPerRegion, sumOp<label>());
 
 
     // Define which regions to keep
@@ -242,8 +242,8 @@ void Foam::distanceSurface::filterKeepNearestRegions
         }
     }
 
-    // Sum totals from all processors
-    Pstream::listCombineGather(nCutsPerRegion, plusEqOp<label>());
+    // Sum totals from all processors (onto the master)
+    Pstream::listGather(nCutsPerRegion, sumOp<label>());
 
     // Get nearest
     Pstream::listCombineGather(nearest, minFirstEqOp<scalar>());
@@ -355,8 +355,8 @@ void Foam::distanceSurface::filterRegionProximity
         areaRegion[regioni] += (faceArea);
     }
 
-    Pstream::listCombineGather(distRegion, plusEqOp<scalar>());
-    Pstream::listCombineGather(areaRegion, plusEqOp<scalar>());
+    Pstream::listGather(distRegion, sumOp<scalar>());
+    Pstream::listGather(areaRegion, sumOp<scalar>());
 
     if (Pstream::master())
     {
diff --git a/src/sampling/surface/isoSurface/isoSurfacePoint.C b/src/sampling/surface/isoSurface/isoSurfacePoint.C
index 020a0465a2..b450c9b0f5 100644
--- a/src/sampling/surface/isoSurface/isoSurfacePoint.C
+++ b/src/sampling/surface/isoSurface/isoSurfacePoint.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2015-2024 OpenCFD Ltd.
+    Copyright (C) 2015-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -256,7 +256,7 @@ void Foam::isoSurfacePoint::syncUnseparatedPoints
         }
 
         // Globally consistent
-        Pstream::listCombineReduce(sharedPts, minEqOp<point>());
+        Pstream::listReduce(sharedPts, minOp<point>());
 
         // Now we will all have the same information. Merge it back with
         // my local information.
diff --git a/src/thermophysicalModels/radiation/radiationModels/solarLoad/faceReflecting/faceReflecting.C b/src/thermophysicalModels/radiation/radiationModels/solarLoad/faceReflecting/faceReflecting.C
index 32fa503e54..53236148ec 100644
--- a/src/thermophysicalModels/radiation/radiationModels/solarLoad/faceReflecting/faceReflecting.C
+++ b/src/thermophysicalModels/radiation/radiationModels/solarLoad/faceReflecting/faceReflecting.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018-2022 OpenCFD Ltd.
+    Copyright (C) 2018-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -327,7 +327,7 @@ void Foam::faceReflecting::calculate()
     // Distribute ray indexes to all proc's
     // Make sure all the processors have the same information
 
-    Pstream::listCombineReduce(refDisDirsIndex, maxEqOp<label>());
+    Pstream::listReduce(refDisDirsIndex, maxOp<label>());
     Pstream::mapCombineReduce(refFacesDirIndex, minEqOp<label>());
 
     const scalar maxBounding =
diff --git a/src/thermophysicalModels/radiation/radiationModels/viewFactor/viewFactor.C b/src/thermophysicalModels/radiation/radiationModels/viewFactor/viewFactor.C
index d434b37a90..79267e4c80 100644
--- a/src/thermophysicalModels/radiation/radiationModels/viewFactor/viewFactor.C
+++ b/src/thermophysicalModels/radiation/radiationModels/viewFactor/viewFactor.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2016-2022 OpenCFD Ltd.
+    Copyright (C) 2016-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -969,9 +969,9 @@ void Foam::radiation::viewFactor::calculate()
                 qrExt[compactGlobalIds[i]] = compactCoarseHo[i];
             }
 
-            Pstream::listCombineReduce(T4, maxEqOp<scalar>());
-            Pstream::listCombineReduce(E, maxEqOp<scalar>());
-            Pstream::listCombineReduce(qrExt, maxEqOp<scalar>());
+            Pstream::listReduce(T4, maxOp<scalar>());
+            Pstream::listReduce(E, maxOp<scalar>());
+            Pstream::listReduce(qrExt, maxOp<scalar>());
 
             if (Pstream::master())
             {