diff --git a/.github/workflows/build-check-freebsd.yml b/.github/workflows/build-check-freebsd.yml
index 44b4ccc7..e50d7ce2 100644
--- a/.github/workflows/build-check-freebsd.yml
+++ b/.github/workflows/build-check-freebsd.yml
@@ -21,6 +21,6 @@ jobs:
           sudo pkg install -y autoconf automake libtool
           ./automake.sh
           ./configure
-          make
+          make -j"$(nproc)"
           make check
           make distcheck
\ No newline at end of file
diff --git a/.github/workflows/build-check-linux.yml b/.github/workflows/build-check-linux.yml
index 75f53b3c..6aec8d09 100644
--- a/.github/workflows/build-check-linux.yml
+++ b/.github/workflows/build-check-linux.yml
@@ -15,6 +15,6 @@ jobs:
       run: |
         ./automake.sh
         ./configure
-        make
+        make -j"$(nproc)"
         make check
         make distcheck
diff --git a/.github/workflows/build-check-macos.yml b/.github/workflows/build-check-macos.yml
index 4046fcf6..c9e5c305 100644
--- a/.github/workflows/build-check-macos.yml
+++ b/.github/workflows/build-check-macos.yml
@@ -18,6 +18,6 @@ jobs:
       run: |
         ./automake.sh
         ./configure
-        make
+        make -j"$(sysctl -n hw.ncpu)"
         make check
         make distcheck
diff --git a/.github/workflows/build-release.yml b/.github/workflows/build-release.yml
index 02d4a0b6..dc6436ac 100644
--- a/.github/workflows/build-release.yml
+++ b/.github/workflows/build-release.yml
@@ -63,7 +63,7 @@ jobs:
       run: |
         ./automake.sh
         ./configure ${{ matrix.configure_host }}
-        make
+        make -j"$(nproc)"
 
     - name: Upload binary artifact
       uses: actions/upload-artifact@v7
@@ -117,11 +117,8 @@ jobs:
         include:
         - arch: amd64
           xcxxflags: -arch x86_64 -mmacosx-version-min=10.13
-          configure_host: --host=x86_64-apple-darwin
         - arch: arm64
-          xcxxflags: -mmacosx-version-min=11.0
-        - arch: universal
-          xcxxflags: -arch x86_64 -arch arm64 -mmacosx-version-min=10.13
+          xcxxflags: -arch arm64 -mmacosx-version-min=11.0
 
     runs-on: macos-latest
 
@@ -131,13 +128,16 @@ jobs:
     - name: prepare
       run: brew install automake
 
+    # NOTE: setting CFLAGS/CXXFLAGS suppresses autoconf's default "-g -O2",
+    # so -O2 must be passed explicitly or the build ends up unoptimised.
     - name: Build
       env:
-        CXXFLAGS: ${{ matrix.xcxxflags }}
+        CFLAGS: -O3 ${{ matrix.xcxxflags }}
+        CXXFLAGS: -O3 ${{ matrix.xcxxflags }}
       run: |
         ./automake.sh
-        ./configure ${{ matrix.configure_host }}
-        make
+        ./configure
+        make -j"$(sysctl -n hw.ncpu)"
         strip par2
 
     - name: Upload binary artifact
@@ -148,6 +148,34 @@ jobs:
           par2
         retention-days: 5
 
+  build-macos-universal:
+    needs:
+    - build-macos
+
+    runs-on: macos-latest
+
+    steps:
+    - name: Download slices
+      uses: actions/download-artifact@v7
+      with:
+        pattern: par2cmdline-macos-*
+
+    - name: Create universal binary
+      run: |
+        lipo -create \
+          par2cmdline-macos-amd64/par2 \
+          par2cmdline-macos-arm64/par2 \
+          -output par2
+        lipo -info par2
+
+    - name: Upload binary artifact
+      uses: actions/upload-artifact@v7
+      with:
+        name: par2cmdline-macos-universal
+        path: |
+          par2
+        retention-days: 5
+
   build-freebsd:
     needs:
     - build-check-freebsd
@@ -181,7 +209,7 @@ jobs:
           sudo pkg install -y autoconf automake libtool
           ./automake.sh
           ./configure
-          make
+          make -j"$(nproc)"
           strip par2
 
     - name: Upload binary artifact
diff --git a/libpar2.vcxproj b/libpar2.vcxproj
index 5e201779..3ee84908 100644
--- a/libpar2.vcxproj
+++ b/libpar2.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>StaticLibrary</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/par2cmdline.vcxproj b/par2cmdline.vcxproj
index 77795e32..85e0247f 100644
--- a/par2cmdline.vcxproj
+++ b/par2cmdline.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/tests/commandline_test.vcxproj b/tests/commandline_test.vcxproj
index 16b2642c..43b34c09 100644
--- a/tests/commandline_test.vcxproj
+++ b/tests/commandline_test.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/tests/crc_test.vcxproj b/tests/crc_test.vcxproj
index a32dcac5..475f2012 100644
--- a/tests/crc_test.vcxproj
+++ b/tests/crc_test.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/tests/criticalpacket_test.vcxproj b/tests/criticalpacket_test.vcxproj
index 285beb50..59f80729 100644
--- a/tests/criticalpacket_test.vcxproj
+++ b/tests/criticalpacket_test.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/tests/descriptionpacket_test.vcxproj b/tests/descriptionpacket_test.vcxproj
index bdc6df70..ae3e4f53 100644
--- a/tests/descriptionpacket_test.vcxproj
+++ b/tests/descriptionpacket_test.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/tests/diskfile_test.vcxproj b/tests/diskfile_test.vcxproj
index 4ad53f2b..aa487ce4 100644
--- a/tests/diskfile_test.vcxproj
+++ b/tests/diskfile_test.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/tests/galois_test.vcxproj b/tests/galois_test.vcxproj
index 8238f95f..18bbae7b 100644
--- a/tests/galois_test.vcxproj
+++ b/tests/galois_test.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/tests/letype_test.vcxproj b/tests/letype_test.vcxproj
index ba9f1c99..90bd5306 100644
--- a/tests/letype_test.vcxproj
+++ b/tests/letype_test.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/tests/libpar2_test.vcxproj b/tests/libpar2_test.vcxproj
index 00dd4f76..db3c26bd 100644
--- a/tests/libpar2_test.vcxproj
+++ b/tests/libpar2_test.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/tests/md5_test.vcxproj b/tests/md5_test.vcxproj
index 5ef80c28..1eb48d05 100644
--- a/tests/md5_test.vcxproj
+++ b/tests/md5_test.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/tests/reedsolomon_test.vcxproj b/tests/reedsolomon_test.vcxproj
index 6aa5194e..ebd8e1f7 100644
--- a/tests/reedsolomon_test.vcxproj
+++ b/tests/reedsolomon_test.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">
diff --git a/tests/utf8_test.vcxproj b/tests/utf8_test.vcxproj
index 2364fab1..66ad72a4 100644
--- a/tests/utf8_test.vcxproj
+++ b/tests/utf8_test.vcxproj
@@ -35,7 +35,7 @@
   <PropertyGroup Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <CharacterSet>Unicode</CharacterSet>
-    <PlatformToolset>v143</PlatformToolset>
+    <PlatformToolset>v145</PlatformToolset>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
   <ImportGroup Label="ExtensionSettings">