diff --git a/.github/workflows/package_and_upload_all.yml b/.github/workflows/package_and_upload_all.yml
index 1d28332..754d9be 100644
--- a/.github/workflows/package_and_upload_all.yml
+++ b/.github/workflows/package_and_upload_all.yml
@@ -110,9 +110,9 @@ jobs:
     with:
       name: 🐉 LLVM 🍎 Mac ARM64
       # Target specific
-      # macOS 26: on 14/15 the LLVM 22+ toolchain bundles its own libc++,
-      # which conflicts with the ASan runtime's system libc++.
-      runner_os: macos-26
+      # LLVM 20's ASan runtime deadlocks before main() on macOS 26+, so LLVM 20
+      # (hal/tc/llvm is LLVM 20) runs on macOS 15. Newer LLVM runs on macOS 26.
+      runner_os: ${{ contains(fromJSON('["hal/tc/llvm", "hal/tc/llvm-20"]'), inputs.llvm_profile) && 'macos-15' || 'macos-26' }}
       arch: armv8
       os: Macos
       compiler_profile: ${{ inputs.llvm_profile }}
diff --git a/.github/workflows/self_check.yml b/.github/workflows/self_check.yml
index 174eedc..e42fb01 100644
--- a/.github/workflows/self_check.yml
+++ b/.github/workflows/self_check.yml
@@ -184,6 +184,21 @@ jobs:
       ci_ref: ${{ github.head_ref || github.ref_name }}
     secrets: inherit
 
+  # LLVM 23: the Mac job runs on macOS 26 (LLVM 20 runs on macOS 15).
+  package-libhal_v5:
+    needs: changes
+    if: ${{ needs.changes.outputs.package_and_upload_all == 'true' }}
+    uses: ./.github/workflows/package_and_upload_all.yml
+    with:
+      library: libhal
+      repo: libhal/libhal
+      dir: v5
+      modules_support_needed: true
+      llvm_profile: hal/tc/llvm-23
+      conan_version: 2.33.0
+      ci_ref: ${{ github.head_ref || github.ref_name }}
+    secrets: inherit
+
   package-libhal-util:
     needs: changes
     if: ${{ needs.changes.outputs.package_and_upload_all == 'true' }}