diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6c0aa05e..17be1b61 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -101,6 +101,10 @@ jobs:
           - { compiler: 'clang-17', cxxstd: '17,20,2b',    os: 'ubuntu-24.04', stdlib: libc++, install: 'clang-17 libc++-17-dev libc++abi-17-dev' }
           - { compiler: 'clang-18', cxxstd: '11,14',       os: 'ubuntu-24.04', stdlib: libc++, install: 'clang-18 libc++-18-dev libc++abi-18-dev' }
           - { compiler: 'clang-18', cxxstd: '17,20,2b',    os: 'ubuntu-24.04', stdlib: libc++, install: 'clang-18 libc++-18-dev libc++abi-18-dev' }
+          - { compiler: 'clang-19', cxxstd: '11,14',       os: 'ubuntu-24.04', stdlib: libc++, install: 'clang-19 libc++-19-dev libc++abi-19-dev' }
+          - { compiler: 'clang-19', cxxstd: '17,20,2b',    os: 'ubuntu-24.04', stdlib: libc++, install: 'clang-19 libc++-19-dev libc++abi-19-dev' }
+          - { compiler: 'clang-20', cxxstd: '11,14,17',    os: 'ubuntu-24.04', stdlib: libc++, install: 'clang-20 libc++-20-dev libc++abi-20-dev' }
+          - { compiler: 'clang-20', cxxstd: '20,23,2c',    os: 'ubuntu-24.04', stdlib: libc++, install: 'clang-20 libc++-20-dev libc++abi-20-dev' }
 
           # not using libc++ because of https://github.com/llvm/llvm-project/issues/52771
           - { name: "clang-18 w/ sanitizers (11,14)", sanitize: yes,
@@ -117,10 +121,12 @@ jobs:
               stdlib: libc++, install: 'clang-18 libc++-18-dev libc++abi-18-dev', ccache_key: "tsan" }
 
           # OSX, clang
-          - { compiler: clang, cxxstd: '11,14,17,20,2b', os: 'macos-13', sanitize: yes, ccache: no, ccache_key: "san1" }
-          - { compiler: clang, cxxstd: '11,14,17,20,2b', os: 'macos-13', thread-sanitize: yes, targets: 'libs/unordered/test//cfoa_tests', ccache: no, ccache_key: "tsan" }
+          - { compiler: clang, cxxstd: '11,14,17,20,2b', os: 'macos-latest', sanitize: yes, ccache: no, ccache_key: "san1" }
+          - { compiler: clang, cxxstd: '11,14,17,20,2b', os: 'macos-latest', thread-sanitize: yes, targets: 'libs/unordered/test//cfoa_tests', ccache: no, ccache_key: "tsan" }
+
           - { compiler: clang, cxxstd: '11,14,17,20,2b', os: 'macos-14' }
-          - { compiler: clang, cxxstd: '11,14,17,20,2b', os: 'macos-15' }
+          - { compiler: clang, cxxstd: '11,14,17,20,23,2c', os: 'macos-15' }
+          - { compiler: clang, cxxstd: '11,14,17,20,23,2c', os: 'macos-26' }
 
     timeout-minutes: 360
     # posix (gcc-12 w/ sanitizers is taking longer than 210 minutes
diff --git a/test/helpers/pmr.hpp b/test/helpers/pmr.hpp
index cfa10dce..6b8fe6df 100644
--- a/test/helpers/pmr.hpp
+++ b/test/helpers/pmr.hpp
@@ -11,6 +11,7 @@
 #ifndef BOOST_NO_CXX17_HDR_MEMORY_RESOURCE
 
 #include <memory_resource>
+#include <new>
 
 namespace test {
   class counted_new_delete_resource : public std::pmr::memory_resource
@@ -25,17 +26,45 @@ namespace test {
     void* do_allocate(std::size_t bytes, std::size_t alignment) override
     {
       _count += bytes;
+
+#if defined(__cpp_aligned_new) && __cpp_aligned_new >= 201606L
+
       return ::operator new(bytes, std::align_val_t(alignment));
+
+#else
+
+      return ::operator new(bytes);
+      (void)alignment;
+
+#endif
     }
 
     void do_deallocate(
       void* p, std::size_t bytes, std::size_t alignment) override
     {
       _count -= bytes;
-#if __cpp_sized_deallocation
+
+#if defined(__cpp_aligned_new) && __cpp_aligned_new >= 201606L
+# if defined(__cpp_sized_deallocation) && __cpp_sized_deallocation >= 201309L
+
       ::operator delete(p, bytes, std::align_val_t(alignment));
-#else
+
+# else
+
       ::operator delete(p, std::align_val_t(alignment));
+
+# endif
+#else
+# if defined(__cpp_sized_deallocation) && __cpp_sized_deallocation >= 201309L
+
+      ::operator delete(p, bytes);
+
+# else
+
+      ::operator delete(p);
+      (void)alignment;
+
+# endif
 #endif
     }