diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -152,7 +152,6 @@ CCLINKER    = $(CXX)
 #CXX         = $(PREFIX)g++-8.1
 #CCLINKER    = $(CXX)
 
-# macOS: use Homebrew GCC (supports std::execution::par via TBB backend)
 ifeq ($(UNAME_S),Darwin)
 CC       = gcc-15
 CXX      = g++-15
diff --git a/src/app_components.cpp b/src/app_components.cpp
--- a/src/app_components.cpp
+++ b/src/app_components.cpp
@@ -6,7 +6,6 @@
  */
 
 #include <thread>
-#include <execution>
 #include <iostream>
 #include <fstream>
 #include <filesystem>
@@ -162,7 +161,6 @@ void connectedComponentsOfSlices(PostComplex<mvtyp>& pc, bool saveNoncomets, boo
   */
   if (potentialsOutputAndStop) {
     std::for_each(
-		  std::execution::seq, 
 		  potentials.begin(),
 		  potentials.end(),
 		  [](Rational p)
@@ -180,7 +178,6 @@ void connectedComponentsOfSlices(PostComplex<mvtyp>& pc, bool saveNoncomets, boo
 		  });
   } else {
     std::for_each(
-		  std::execution::par,//fails to trigger parallelism
 		  potentials.begin(),
 		  potentials.end(),
 		  [pc,minConePotential,maxConePotential,saveNoncomets](Rational p)
diff --git a/src/app_halfopenconecomponents.cpp b/src/app_halfopenconecomponents.cpp
--- a/src/app_halfopenconecomponents.cpp
+++ b/src/app_halfopenconecomponents.cpp
@@ -13,6 +13,7 @@
 
 #include <mutex>
 #include <thread>
+#include <tbb/parallel_for_each.h>
 
 #include "gfanlib_tableau.h"
 #include "gfanapplication.h"
@@ -90,7 +91,7 @@ public:
 		  atomic_int64_t numberOfNonEmptyCones=0;
 		  ThreadSafeSequenceStreamIterator i(inputFileOption.getFreshStreamReference());
 		  vector<int> dummy(100);
-		  std::for_each(std::execution::par, dummy.begin(),dummy.end(),[&i,&numberOfNonEmptyCones,&allowedVertices,&mtx,&connectivityThroughEdges](size_t t)
+		  tbb::parallel_for_each(dummy.begin(),dummy.end(),[&i,&numberOfNonEmptyCones,&allowedVertices,&mtx,&connectivityThroughEdges](size_t t)
 				  {
 			  std::cerr<<t<<"\n";
 			  while(auto s1=i.getNextString())
@@ -136,7 +137,7 @@ public:
 			  ThreadSafeSequenceStreamIterator i(inputFileOption.getFreshStreamReference());
 			  std::mutex mtx;
 			  vector<int> dummy(100);
-			  std::for_each(std::execution::par, dummy.begin(),dummy.end(),[&i,&allowedVertices,&classes,&mtx,&connectivityThroughEdges](size_t t)
+			  tbb::parallel_for_each(dummy.begin(),dummy.end(),[&i,&allowedVertices,&classes,&mtx,&connectivityThroughEdges](size_t t)
 					  {
 				  std::cerr<<t<<"\n";
 				  while(auto s1=i.getNextString())
@@ -185,7 +186,7 @@ public:
 		  ThreadSafeSequenceStreamIterator i(inputFileOption.getFreshStreamReference());
 		  std::mutex mtx;
 		  vector<int> dummy(100);
-		  std::for_each(std::execution::par, dummy.begin(),dummy.end(),[&i,&I,&classToIndex,&allowedVertices,&classes,&mtx](size_t t)
+		  tbb::parallel_for_each(dummy.begin(),dummy.end(),[&i,&I,&classToIndex,&allowedVertices,&classes,&mtx](size_t t)
 				  {
 			  std::cerr<<t<<"\n";
 			  while(auto s1=i.getNextString())
diff --git a/src/app_processcomplex.cpp b/src/app_processcomplex.cpp
--- a/src/app_processcomplex.cpp
+++ b/src/app_processcomplex.cpp
@@ -14,7 +14,7 @@
 #include <sstream>
 #include <mutex>
 #include <thread>
-#include <execution>
+#include <tbb/parallel_for_each.h>
 #include "parser.h"
 #include "printer.h"
 #include "polynomial.h"
@@ -225,7 +225,7 @@ if(0)	  {
 			ThreadSafeSequenceStreamIterator i(inputFileOption.getFreshStreamReference(),true);
 			  std::mutex mtx;
 			  vector<int> dummy(100);
-			  std::for_each(std::execution::par, dummy.begin(),dummy.end(),[&](size_t t)
+			  tbb::parallel_for_each(dummy.begin(),dummy.end(),[&](size_t t)
 					  {
 			while(auto s1=i.getNextString())
 			{
diff --git a/src/app_tropicalprevariety.cpp b/src/app_tropicalprevariety.cpp
--- a/src/app_tropicalprevariety.cpp
+++ b/src/app_tropicalprevariety.cpp
@@ -11,6 +11,7 @@
 #include <iostream>
 #include <fstream>
 #include <stdlib.h>
+#include <tbb/parallel_for_each.h>
 #include "parser.h"
 #include "printer.h"
 #include "polynomial.h"
@@ -219,7 +220,7 @@ if(optionRestrictToHalfOpenCones.getValue())
 	  std::mutex mtx;
 	  vector<int> dummy(100);
 	  std::atomic<int> c2=count;
-	  std::for_each(std::execution::par, dummy.begin(),dummy.end(),[this,&useValuation,&n,&ret,&c2,&mtx](size_t t)
+	  tbb::parallel_for_each(dummy.begin(),dummy.end(),[this,&useValuation,&n,&ret,&c2,&mtx](size_t t)
 			  {
 		  	  while(c2>0 && !ssi->eof())
 		  		  {
diff --git a/src/gfanlib_hypersurfaceintersection.cpp b/src/gfanlib_hypersurfaceintersection.cpp
--- a/src/gfanlib_hypersurfaceintersection.cpp
+++ b/src/gfanlib_hypersurfaceintersection.cpp
@@ -7,7 +7,7 @@
 
 #include <mutex>
 #include <thread>
-#include <execution>
+#include <tbb/parallel_for_each.h>
 #include "gfanlib_hypersurfaceintersection.h"
 #include "gfanlib_paralleltraverser.h"
 #include "gfanlib_memoryresource.h"
@@ -435,7 +435,7 @@ namespace gfan{
 
 		vector<int> dummy(100);
 		mutex mtx;
-		std::for_each(std::execution::par, dummy.begin(),dummy.end(),[&](size_t t)
+		tbb::parallel_for_each(dummy.begin(),dummy.end(),[&](size_t t)
 			{
 			StackResource localStackResource1(20160000);
 			StackResource localStackResource2(20160000);