diff --git a/.bazelrc b/.bazelrc
index 81ee5fa9..3d3dbba4 100644
--- a/.bazelrc
+++ b/.bazelrc
@@ -6,6 +6,10 @@
 common --enable_bzlmod
 common --noenable_workspace
 
+# Auto-select build:linux / build:macos / build:windows based on the host OS,
+# so platform-specific flags don't need manual --config= activation.
+common --enable_platform_specific_config
+
 # In Bazel 9, native C++ rules are no longer injected into the global namespace
 # by default.  Two files in grpc 1.76.0 still use native.cc_*:
 #   bazel/cython_library.bzl      (native.cc_binary)
@@ -15,3 +19,8 @@ build --incompatible_autoload_externally=+cc_library,+cc_binary
 
 build --conlyopt='-std=gnu11' --cxxopt='-std=c++17'
 build --host_cxxopt='-std=c++17'
+
+# Deployment target 10.13 is the minimum for C++17 aligned_alloc in libc++.
+# host_macos_minimum_os covers host tool builds (e.g. protoc).
+build:macos --macos_minimum_os=10.13
+build:macos --host_macos_minimum_os=10.13
diff --git a/.github/workflows/bazel.yml b/.github/workflows/bazel.yml
index 2caeb893..624b2f87 100644
--- a/.github/workflows/bazel.yml
+++ b/.github/workflows/bazel.yml
@@ -12,31 +12,47 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
-    env:
-      BAZEL: bazelisk-linux-amd64
-      BUILDIFIER: buildifier-linux-amd64
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+    runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v7
         with:
           submodules: recursive
 
+      - name: Set platform environment variables
+        run: |
+          case "$(uname -s)" in
+            Linux*)  OS=linux ;;
+            Darwin*) OS=darwin ;;
+          esac
+          case "$(uname -m)" in
+            x86_64)        ARCH=amd64 ;;
+            arm64|aarch64) ARCH=arm64 ;;
+          esac
+          echo "OS=${OS}" >> $GITHUB_ENV
+          echo "ARCH=${ARCH}" >> $GITHUB_ENV
+
       - name: Mount bazel cache
         uses: actions/cache@v6
         with:
+          # Bazel's output root differs by OS: ~/.cache/bazel on Linux, ~/Library/Caches/bazel on macOS.
           # See https://docs.bazel.build/versions/master/output_directories.html
-          path: "~/.cache/bazel"
+          path: ${{ runner.os == 'macOS' && '~/Library/Caches/bazel' || '~/.cache/bazel' }}
           # Create a new cache entry whenever Bazel files change.
           # See https://docs.github.com/en/actions/guides/caching-dependencies-to-speed-up-workflows
-          key: bazel-${{ runner.os }}-build-${{ hashFiles('**/*.bzl', '**/*.bazel') }}
+          key: bazel-${{ runner.os }}-${{ runner.arch }}-build-${{ hashFiles('**/*.bzl', '**/*.bazel') }}
           restore-keys: |
-            bazel-${{ runner.os }}-build-
+            bazel-${{ runner.os }}-${{ runner.arch }}-build-
 
       - name: Install Buildifier
         run: |
-          curl -LO "https://github.com/bazelbuild/buildtools/releases/download/v8.5.1/$BUILDIFIER"
-          chmod +x $BUILDIFIER
-          sudo mv $BUILDIFIER /usr/local/bin/buildifier
+          BUILDIFIER="buildifier-${OS}-${ARCH}"
+          curl -LO "https://github.com/bazelbuild/buildtools/releases/download/v8.5.1/${BUILDIFIER}"
+          chmod +x "${BUILDIFIER}"
+          sudo mv "${BUILDIFIER}" /usr/local/bin/buildifier
 
       - name: Run Buildifier
         run: |
@@ -53,9 +69,10 @@ jobs:
 
       - name: Install bazelisk
         run: |
-          curl -LO "https://github.com/bazelbuild/bazelisk/releases/download/v1.29.0/$BAZEL"
-          chmod +x $BAZEL
-          sudo mv $BAZEL /usr/local/bin/bazel
+          BAZEL="bazelisk-${OS}-${ARCH}"
+          curl -LO "https://github.com/bazelbuild/bazelisk/releases/download/v1.29.0/${BAZEL}"
+          chmod +x "${BAZEL}"
+          sudo mv "${BAZEL}" /usr/local/bin/bazel
 
       - name: Build
         run: bazel build //targets/simple_switch_grpc:simple_switch_grpc
diff --git a/BUILD.bazel b/BUILD.bazel
index de00349a..9f01abe5 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -28,8 +28,8 @@ expand_template(
     substitutions = {
         # disabled
         "#cmakedefine BM_DEBUG_ON @BM_DEBUG_ON@": "/* #undef BM_DEBUG_ON */",
-        "#cmakedefine BM_ELOG_ON @BM_ELOG_ON@": "/* #undef BM_ELOG_ON */",
         # enabled
+        "#cmakedefine BM_ELOG_ON @BM_ELOG_ON@": "#define BM_ELOG_ON 1",
         "#cmakedefine BM_ENABLE_MODULES @BM_ENABLE_MODULES@": "#define BM_ENABLE_MODULES 1",
         "#cmakedefine BM_HAVE_ALGORITHM @BM_HAVE_ALGORITHM@": "#define BM_HAVE_ALGORITHM 1",
         "#cmakedefine BM_HAVE_ARRAY @BM_HAVE_ARRAY@": "#define BM_HAVE_ARRAY 1",