diff --git a/.github/workflows/MacOS.yml b/.github/workflows/MacOS.yml
index a0eb8ae6..28c546e1 100644
--- a/.github/workflows/MacOS.yml
+++ b/.github/workflows/MacOS.yml
@@ -22,6 +22,13 @@ jobs:
       fail-fast: false
       matrix:
         include:
+          - name: osx26-arm-clang-clang-repl-20
+            os: macos-26
+            compiler: clang
+            clang-runtime: '20'
+            cling: Off
+            llvm_enable_projects: "clang"
+            llvm_targets_to_build: "host"
           - name: osx26-arm-clang-clang-repl-19
             os: macos-26
             compiler: clang
@@ -44,6 +51,13 @@ jobs:
             cling-version: '1.2'
             llvm_enable_projects: "clang"
             llvm_targets_to_build: "host;NVPTX"
+          - name: osx15-x86-clang-clang-repl-20
+            os: macos-15-intel
+            compiler: clang
+            clang-runtime: '20'
+            cling: Off
+            llvm_enable_projects: "clang"
+            llvm_targets_to_build: "host"
           - name: osx15-x86-clang-clang-repl-19
             os: macos-15-intel
             compiler: clang
@@ -251,6 +265,12 @@ jobs:
       fail-fast: false
       matrix:
         include:
+          - name: osx26-arm-clang-clang-repl-20-cppyy
+            os: macos-26
+            compiler: clang
+            clang-runtime: '20'
+            cling: Off
+            cppyy: On
           - name: osx26-arm-clang-clang-repl-19-cppyy
             os: macos-26
             compiler: clang
@@ -270,6 +290,12 @@ jobs:
             cling: On
             cling-version: '1.2'
             cppyy: On
+          - name: osx15-x86-clang-clang-repl-20-cppyy
+            os: macos-15-intel
+            compiler: clang
+            clang-runtime: '20'
+            cling: Off
+            cppyy: On
           - name: osx15-x86-clang-clang-repl-19-cppyy
             os: macos-15-intel
             compiler: clang
diff --git a/.github/workflows/Ubuntu.yml b/.github/workflows/Ubuntu.yml
index e8fd8c96..5b93ed3f 100644
--- a/.github/workflows/Ubuntu.yml
+++ b/.github/workflows/Ubuntu.yml
@@ -22,6 +22,13 @@ jobs:
       fail-fast: false
       matrix:
         include:
+          - name: ubu22-x86-gcc12-clang-repl-20
+            os: ubuntu-22.04
+            compiler: gcc-12
+            clang-runtime: '20'
+            cling: Off
+            llvm_enable_projects: "clang"
+            llvm_targets_to_build: "host;NVPTX"
           - name: ubu22-x86-gcc12-clang-repl-19
             os: ubuntu-22.04
             compiler: gcc-12
@@ -44,6 +51,13 @@ jobs:
             cling-version: '1.2'
             llvm_enable_projects: "clang"
             llvm_targets_to_build: "host;NVPTX"
+          - name: ubu24-x86-gcc12-clang-repl-20
+            os: ubuntu-24.04
+            compiler: gcc-12
+            clang-runtime: '20'
+            cling: Off
+            llvm_enable_projects: "clang"
+            llvm_targets_to_build: "host;NVPTX"
           - name: ubu24-x86-gcc12-clang-repl-19
             os: ubuntu-24.04
             compiler: gcc-12
@@ -66,6 +80,13 @@ jobs:
             cling-version: '1.2'
             llvm_enable_projects: "clang"
             llvm_targets_to_build: "host;NVPTX"
+          - name: ubu22-arm-gcc12-clang-repl-20
+            os: ubuntu-22.04-arm
+            compiler: gcc-12
+            clang-runtime: '20'
+            cling: Off
+            llvm_enable_projects: "clang"
+            llvm_targets_to_build: "host;NVPTX"
           - name: ubu22-arm-gcc12-clang-repl-19
             os: ubuntu-22.04-arm
             compiler: gcc-12
@@ -88,6 +109,13 @@ jobs:
             cling-version: '1.2'
             llvm_enable_projects: "clang"
             llvm_targets_to_build: "host;NVPTX"
+          - name: ubu24-arm-gcc12-clang-repl-20
+            os: ubuntu-24.04-arm
+            compiler: gcc-12
+            clang-runtime: '20'
+            cling: Off
+            llvm_enable_projects: "clang"
+            llvm_targets_to_build: "host;NVPTX"
           - name: ubu24-arm-gcc12-clang-repl-19
             os: ubuntu-24.04-arm
             compiler: gcc-12
@@ -289,6 +317,12 @@ jobs:
       fail-fast: false
       matrix:
         include:
+          - name: ubu22-x86-gcc12-clang-repl-20-cppyy
+            os: ubuntu-22.04
+            compiler: gcc-12
+            clang-runtime: '20'
+            cling: Off
+            cppyy: On
           - name: ubu22-x86-gcc12-clang-repl-19-cppyy
             os: ubuntu-22.04
             compiler: gcc-12
@@ -308,6 +342,12 @@ jobs:
             cling: On
             cling-version: '1.2'
             cppyy: On
+          - name: ubu24-x86-gcc12-clang-repl-20-cppyy
+            os: ubuntu-24.04
+            compiler: gcc-12
+            clang-runtime: '20'
+            cling: Off
+            cppyy: On
           - name: ubu24-x86-gcc12-clang-repl-19-cppyy
             os: ubuntu-24.04
             compiler: gcc-12
@@ -327,6 +367,12 @@ jobs:
             cling: On
             cling-version: '1.2'
             cppyy: On
+          - name: ubu22-arm-gcc12-clang-repl-20-cppyy
+            os: ubuntu-22.04-arm
+            compiler: gcc-12
+            clang-runtime: '20'
+            cling: Off
+            cppyy: On
           - name: ubu22-arm-gcc12-clang-repl-19-cppyy
             os: ubuntu-22.04-arm
             compiler: gcc-12
@@ -346,6 +392,12 @@ jobs:
             cling: On
             cling-version: '1.2'
             cppyy: On
+          - name: ubu24-arm-gcc12-clang-repl-20-cppyy
+            os: ubuntu-24.04-arm
+            compiler: gcc-12
+            clang-runtime: '20'
+            cling: Off
+            cppyy: On
           - name: ubu24-arm-gcc12-clang-repl-19-cppyy
             os: ubuntu-24.04-arm
             compiler: gcc-12
diff --git a/etc/clang20-valgrind.supp b/etc/clang20-valgrind.supp
new file mode 100644
index 00000000..4c1256ab
--- /dev/null
+++ b/etc/clang20-valgrind.supp
@@ -0,0 +1,102 @@
+{
+ LLVM 20 suppressions : CodeGen::CodeGenModule::SetLLVMFunctionAttributesForDefinition
+ Memcheck:Cond
+ fun:_ZN5clang7CodeGen13CodeGenModule38SetLLVMFunctionAttributesForDefinitionEPKNS_4DeclEPN4llvm8FunctionE
+ fun:_ZN5clang7CodeGen13CodeGenModule28EmitGlobalFunctionDefinitionENS_10GlobalDeclEPN4llvm11GlobalValueE
+ fun:_ZN5clang7CodeGen13CodeGenModule20EmitGlobalDefinitionENS_10GlobalDeclEPN4llvm11GlobalValueE
+ fun:_ZN5clang7CodeGen13CodeGenModule12EmitDeferredEv
+ fun:_ZN5clang7CodeGen13CodeGenModule12EmitDeferredEv
+ fun:_ZN5clang7CodeGen13CodeGenModule12EmitDeferredEv
+ fun:_ZN5clang7CodeGen13CodeGenModule7ReleaseEv
+ fun:_ZN12_GLOBAL__N_117CodeGeneratorImpl21HandleTranslationUnitERN5clang10ASTContextE
+ fun:_ZN5clang15BackendConsumer21HandleTranslationUnitERNS_10ASTContextE
+ fun:_ZN5clang17MultiplexConsumer21HandleTranslationUnitERNS_10ASTContextE
+ fun:_ZN5clang17IncrementalParser23ParseOrWrapTopLevelDeclEv
+ fun:_ZN5clang17IncrementalParser5ParseEN4llvm9StringRefE
+}
+
+{
+ LLVM 20 suppressions : APInt::setBits
+ Memcheck:Cond
+ fun:_ZN4llvm5APInt7setBitsEjj
+ fun:_ZL16computeKnownBitsPKN4llvm5ValueERKNS_5APIntERNS_9KnownBitsEjRKNS_13SimplifyQueryE
+ fun:_ZN4llvm16computeKnownBitsEPKNS_5ValueERNS_9KnownBitsEjRKNS_13SimplifyQueryE
+ fun:_ZN4llvm16computeKnownBitsEPKNS_5ValueERNS_9KnownBitsERKNS_10DataLayoutEjPNS_15AssumptionCacheEPKNS_11InstructionEPKNS_13DominatorTreeEb
+ fun:_ZNK4llvm12SelectionDAG13InferPtrAlignENS_7SDValueE
+ fun:_ZN12_GLOBAL__N_111DAGCombiner9visitLOADEPN4llvm6SDNodeE
+ fun:_ZN12_GLOBAL__N_111DAGCombiner7combineEPN4llvm6SDNodeE
+ fun:_ZN12_GLOBAL__N_111DAGCombiner3RunEN4llvm12CombineLevelE
+ fun:_ZN4llvm12SelectionDAG7CombineENS_12CombineLevelEPNS_14BatchAAResultsENS_15CodeGenOptLevelE
+ fun:_ZN4llvm16SelectionDAGISel17CodeGenAndEmitDAGEv
+ fun:_ZN4llvm16SelectionDAGISel20SelectAllBasicBlocksERKNS_8FunctionE
+ fun:_ZN4llvm16SelectionDAGISel20runOnMachineFunctionERNS_15MachineFunctionE
+}
+
+{
+ LLVM 20 suppressions : JitCall::Invoke
+ Memcheck:Free
+ fun:free
+ obj:*
+ fun:_ZNK3Cpp7JitCall6InvokeEPvNS0_7ArgListES1_
+ fun:_ZL11WrapperCallPvmS_S_S_
+ fun:_ZN5Cppyy5CallVEPvS0_mS0_
+ fun:_ZL8GILCallVPvS_PN8CPyCppyy11CallContextE
+ fun:_ZN8CPyCppyy12_GLOBAL__N_112VoidExecutor7ExecuteEPvS2_PNS_11CallContextE
+ fun:_ZN8CPyCppyy9CPPMethod11ExecuteFastEPvlPNS_11CallContextE
+ fun:_ZN8CPyCppyy9CPPMethod7ExecuteEPvlPNS_11CallContextE
+ fun:_ZN8CPyCppyy11CPPFunction4CallERPNS_11CPPInstanceEPKP7_objectmS5_PNS_11CallContextE
+ fun:_ZN8CPyCppyy12_GLOBAL__N_1L13mp_vectorcallEPNS_11CPPOverloadEPKP7_objectmS4_
+ fun:_PyObject_VectorcallTstate
+ fun:PyObject_Vectorcall
+}
+
+{
+ LLVM 20 suppressions : CodeGen::CodeGenModule::SetLLVMFunctionAttributesForDefinition 2
+ Memcheck:Cond
+ fun:_ZN5clang7CodeGen13CodeGenModule38SetLLVMFunctionAttributesForDefinitionEPKNS_4DeclEPN4llvm8FunctionE
+ fun:_ZN5clang7CodeGen13CodeGenModule18codegenCXXStructorENS_10GlobalDeclE
+ fun:_ZN12_GLOBAL__N_113ItaniumCXXABI15emitCXXStructorEN5clang10GlobalDeclE
+ fun:_ZN5clang7CodeGen13CodeGenModule20EmitGlobalDefinitionENS_10GlobalDeclEPN4llvm11GlobalValueE
+ fun:_ZN5clang7CodeGen13CodeGenModule12EmitDeferredEv
+ fun:_ZN5clang7CodeGen13CodeGenModule12EmitDeferredEv
+ fun:_ZN5clang7CodeGen13CodeGenModule7ReleaseEv
+ fun:_ZN12_GLOBAL__N_117CodeGeneratorImpl21HandleTranslationUnitERN5clang10ASTContextE
+ fun:_ZN5clang15BackendConsumer21HandleTranslationUnitERNS_10ASTContextE
+ fun:_ZN5clang17MultiplexConsumer21HandleTranslationUnitERNS_10ASTContextE
+ fun:_ZN5clang17IncrementalParser23ParseOrWrapTopLevelDeclEv
+ fun:_ZN5clang17IncrementalParser5ParseEN4llvm9StringRefE
+}
+
+{
+ LLVM 20 suppressions : CodeGen::CodeGenModule::SetLLVMFunctionAttributesForDefinition 3
+ Memcheck:Cond
+ fun:_ZN5clang7CodeGen13CodeGenModule38SetLLVMFunctionAttributesForDefinitionEPKNS_4DeclEPN4llvm8FunctionE
+ fun:_ZN5clang7CodeGen14CodeGenVTables14maybeEmitThunkENS_10GlobalDeclERKNS_9ThunkInfoEb
+ fun:_ZN5clang7CodeGen14CodeGenVTables10EmitThunksENS_10GlobalDeclE
+ fun:_ZN5clang7CodeGen13CodeGenModule20EmitGlobalDefinitionENS_10GlobalDeclEPN4llvm11GlobalValueE
+ fun:_ZN5clang7CodeGen13CodeGenModule12EmitDeferredEv
+ fun:_ZN5clang7CodeGen13CodeGenModule12EmitDeferredEv
+ fun:_ZN5clang7CodeGen13CodeGenModule7ReleaseEv
+ fun:_ZN12_GLOBAL__N_117CodeGeneratorImpl21HandleTranslationUnitERN5clang10ASTContextE
+ fun:_ZN5clang15BackendConsumer21HandleTranslationUnitERNS_10ASTContextE
+ fun:_ZN5clang17MultiplexConsumer21HandleTranslationUnitERNS_10ASTContextE
+ fun:_ZN5clang17IncrementalParser23ParseOrWrapTopLevelDeclEv
+ fun:_ZN5clang17IncrementalParser5ParseEN4llvm9StringRefE
+}
+
+{
+ LLVM 20 suppressions : CodeGen::CodeGenModule::SetLLVMFunctionAttributesForDefinition 4
+ Memcheck:Cond
+ fun:_ZN5clang7CodeGen13CodeGenModule38SetLLVMFunctionAttributesForDefinitionEPKNS_4DeclEPN4llvm8FunctionE
+ fun:_ZN5clang7CodeGen13CodeGenModule28EmitGlobalFunctionDefinitionENS_10GlobalDeclEPN4llvm11GlobalValueE
+ fun:_ZN5clang7CodeGen13CodeGenModule20EmitGlobalDefinitionENS_10GlobalDeclEPN4llvm11GlobalValueE
+ fun:_ZN5clang7CodeGen13CodeGenModule10EmitGlobalENS_10GlobalDeclE
+ fun:_ZN5clang7CodeGen13CodeGenModule16EmitTopLevelDeclEPNS_4DeclE.part.0
+ fun:_ZN12_GLOBAL__N_117CodeGeneratorImpl18HandleTopLevelDeclEN5clang12DeclGroupRefE
+ fun:_ZN5clang15BackendConsumer18HandleTopLevelDeclENS_12DeclGroupRefE
+ fun:_ZN5clang17MultiplexConsumer18HandleTopLevelDeclENS_12DeclGroupRefE
+ fun:_ZN5clang28InProcessPrintingASTConsumer18HandleTopLevelDeclENS_12DeclGroupRefE
+ fun:_ZN5clang17IncrementalParser23ParseOrWrapTopLevelDeclEv
+ fun:_ZN5clang17IncrementalParser5ParseEN4llvm9StringRefE
+ fun:_ZN5clang11Interpreter5ParseEN4llvm9StringRefE
+}
diff --git a/etc/clang20-valgrind_arm.supp b/etc/clang20-valgrind_arm.supp
new file mode 100644
index 00000000..96e114ff
--- /dev/null
+++ b/etc/clang20-valgrind_arm.supp
@@ -0,0 +1,7 @@
+{
+ Mismatched free()
+ Memcheck:Free
+ fun:free
+ obj:*
+}
+
diff --git a/test/test_datatypes.py b/test/test_datatypes.py
index 10ede101..3e73296f 100644
--- a/test/test_datatypes.py
+++ b/test/test_datatypes.py
@@ -1409,7 +1409,7 @@ def pyd(arg0, arg1):
         gc.collect()
         raises(TypeError, c, 3, 3) # lambda gone out of scope
 
-    @mark.xfail(run=False, condition=IS_MAC_ARM, reason="Crashes with exception not being caught on Apple Silicon")
+    @mark.xfail(run=False, condition=IS_MAC, reason="Crashes on MacOS")
     def test28_callable_through_function_passing(self):
         """Passing callables through std::function"""