diff --git a/.github/actions/install-boost/action.yml b/.github/actions/install-boost/action.yml
index 6f918936d..39b3a0af4 100644
--- a/.github/actions/install-boost/action.yml
+++ b/.github/actions/install-boost/action.yml
@@ -43,8 +43,8 @@ runs:
       if: runner.os == 'macOS'
       shell: bash
       run: |
-        brew install boost
-        echo "BOOST_ROOT=$(brew --prefix boost)" >> $GITHUB_OUTPUT
+        brew install boost@1.85
+        echo "BOOST_ROOT=$(brew --prefix boost@1.85)" >> $GITHUB_OUTPUT
 
     - name: Determine root
       id: determine-root
diff --git a/.github/actions/install-openssl/action.yml b/.github/actions/install-openssl/action.yml
index 6d10d813f..3674a8b0d 100644
--- a/.github/actions/install-openssl/action.yml
+++ b/.github/actions/install-openssl/action.yml
@@ -32,7 +32,7 @@ runs:
       if: runner.os == 'Windows'
       shell: bash
       run: |
-        choco install openssl --version 3.5.4 -y --no-progress
+        choco install openssl --version 3.6.1 -y --no-progress
         if [ -d "C:\Program Files\OpenSSL-Win64" ]; then
           echo "OPENSSL_ROOT_DIR=C:\Program Files\OpenSSL-Win64" >> $GITHUB_OUTPUT
         else
diff --git a/.github/actions/sdk-release/action.yml b/.github/actions/sdk-release/action.yml
index 7ade5eb96..c4dd29aa3 100644
--- a/.github/actions/sdk-release/action.yml
+++ b/.github/actions/sdk-release/action.yml
@@ -18,6 +18,10 @@ inputs:
     required: true
   sdk_cmake_target:
     description: 'CMake target of the sdk, e.g. launchdarkly-cpp-client.'
+  mac_artifact_arch:
+    description: 'Architecture label for macOS artifacts (x64 or arm64).'
+    required: false
+    default: 'x64'
 outputs:
   hashes-linux:
     description: "base64-encoded sha256 hash of linux build artifacts"
@@ -272,21 +276,21 @@ runs:
         OPENSSL_ROOT_DIR: ${{ steps.install-openssl.outputs.OPENSSL_ROOT_DIR }}
         CURL_ROOT: ${{ steps.install-curl.outputs.CURL_ROOT }}
 
-    - name: Archive Release Mac - AppleClang/x64/Static
+    - name: Archive Release Mac - AppleClang/${{ inputs.mac_artifact_arch }}/Static
       if: runner.os == 'macOS'
       uses: thedoctor0/zip-release@0.7.1
       with:
         path: 'build-static/release'
         type: 'zip'
-        filename: 'mac-clang-x64-static.zip'
+        filename: 'mac-clang-${{ inputs.mac_artifact_arch }}-static.zip'
 
-    - name: Archive Release Mac - AppleClang/x64/Dynamic
+    - name: Archive Release Mac - AppleClang/${{ inputs.mac_artifact_arch }}/Dynamic
       if: runner.os == 'macOS'
       uses: thedoctor0/zip-release@0.7.1
       with:
         path: 'build-dynamic/release'
         type: 'zip'
-        filename: 'mac-clang-x64-dynamic.zip'
+        filename: 'mac-clang-${{ inputs.mac_artifact_arch }}-dynamic.zip'
 
     - name: Determine CURL artifact suffix for server SDK
       if: runner.os == 'macOS'
@@ -299,21 +303,21 @@ runs:
           echo "suffix=" >> $GITHUB_OUTPUT
         fi
 
-    - name: Archive Release Mac - AppleClang/x64/Static/CURL
+    - name: Archive Release Mac - AppleClang/${{ inputs.mac_artifact_arch }}/Static/CURL
       if: runner.os == 'macOS'
       uses: thedoctor0/zip-release@0.7.1
       with:
         path: 'build-static-curl/release'
         type: 'zip'
-        filename: 'mac-clang-x64-static-curl${{ steps.curl-suffix-macos.outputs.suffix }}.zip'
+        filename: 'mac-clang-${{ inputs.mac_artifact_arch }}-static-curl${{ steps.curl-suffix-macos.outputs.suffix }}.zip'
 
-    - name: Archive Release Mac - AppleClang/x64/Dynamic/CURL
+    - name: Archive Release Mac - AppleClang/${{ inputs.mac_artifact_arch }}/Dynamic/CURL
       if: runner.os == 'macOS'
       uses: thedoctor0/zip-release@0.7.1
       with:
         path: 'build-dynamic-curl/release'
         type: 'zip'
-        filename: 'mac-clang-x64-dynamic-curl${{ steps.curl-suffix-macos.outputs.suffix }}.zip'
+        filename: 'mac-clang-${{ inputs.mac_artifact_arch }}-dynamic-curl${{ steps.curl-suffix-macos.outputs.suffix }}.zip'
 
     - name: Hash Mac Build Artifacts for provenance
       if: runner.os == 'macOS'
@@ -321,7 +325,8 @@ runs:
       id: hash-macos
       run: |
         CURL_SUFFIX="${{ steps.curl-suffix-macos.outputs.suffix }}"
-        echo "hashes-macos=$(shasum -a 256 mac-clang-x64-static.zip mac-clang-x64-dynamic.zip mac-clang-x64-static-curl${CURL_SUFFIX}.zip mac-clang-x64-dynamic-curl${CURL_SUFFIX}.zip | base64 -b 0)" >> "$GITHUB_OUTPUT"
+        ARCH="${{ inputs.mac_artifact_arch }}"
+        echo "hashes-macos=$(shasum -a 256 mac-clang-${ARCH}-static.zip mac-clang-${ARCH}-dynamic.zip mac-clang-${ARCH}-static-curl${CURL_SUFFIX}.zip mac-clang-${ARCH}-dynamic-curl${CURL_SUFFIX}.zip | base64 -b 0)" >> "$GITHUB_OUTPUT"
 
     - name: Upload Mac Build Artifacts
       if: runner.os == 'macOS'
@@ -329,6 +334,7 @@ runs:
       run: |
         ls
         CURL_SUFFIX="${{ steps.curl-suffix-macos.outputs.suffix }}"
-        gh release upload ${{ inputs.tag_name }} mac-clang-x64-static.zip mac-clang-x64-dynamic.zip mac-clang-x64-static-curl${CURL_SUFFIX}.zip mac-clang-x64-dynamic-curl${CURL_SUFFIX}.zip --clobber
+        ARCH="${{ inputs.mac_artifact_arch }}"
+        gh release upload ${{ inputs.tag_name }} mac-clang-${ARCH}-static.zip mac-clang-${ARCH}-dynamic.zip mac-clang-${ARCH}-static-curl${CURL_SUFFIX}.zip mac-clang-${ARCH}-dynamic-curl${CURL_SUFFIX}.zip --clobber
       env:
         GH_TOKEN: ${{ inputs.github_token }}
diff --git a/.github/workflows/client.yml b/.github/workflows/client.yml
index a40f4ddb0..beffa64d4 100644
--- a/.github/workflows/client.yml
+++ b/.github/workflows/client.yml
@@ -80,7 +80,7 @@ jobs:
           simulate_release: true
 
   build-test-client-mac:
-    runs-on: macos-13
+    runs-on: macos-15
     steps:
       # https://github.com/actions/checkout/releases/tag/v4.3.0
       - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955
@@ -91,7 +91,7 @@ jobs:
           simulate_release: true
 
   build-test-client-mac-curl:
-    runs-on: macos-13
+    runs-on: macos-15
     steps:
       # https://github.com/actions/checkout/releases/tag/v4.3.0
       - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955
diff --git a/.github/workflows/cmake.yml b/.github/workflows/cmake.yml
index 29761f85d..35d80683d 100644
--- a/.github/workflows/cmake.yml
+++ b/.github/workflows/cmake.yml
@@ -40,7 +40,7 @@ jobs:
           cmake_extra_args: '-DLD_CURL_NETWORKING=ON'
 
   test-macos:
-    runs-on: macos-13
+    runs-on: macos-15
     steps:
       # https://github.com/actions/checkout/releases/tag/v4.3.0
       - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955
@@ -49,7 +49,7 @@ jobs:
           platform_version: '12'
 
   test-macos-curl:
-    runs-on: macos-13
+    runs-on: macos-15
     steps:
       # https://github.com/actions/checkout/releases/tag/v4.3.0
       - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955
diff --git a/.github/workflows/hello-apps.yml b/.github/workflows/hello-apps.yml
index c8bfab497..aba5ab616 100644
--- a/.github/workflows/hello-apps.yml
+++ b/.github/workflows/hello-apps.yml
@@ -15,7 +15,7 @@ jobs:
   smoketest:
     strategy:
       matrix:
-        os: [ "ubuntu-22.04", "macos-13", "windows-2022" ]
+        os: [ "ubuntu-22.04", "macos-15", "windows-2022" ]
       fail-fast: false
     runs-on: ${{ matrix.os }}
     steps:
diff --git a/.github/workflows/manual-sdk-release-artifacts.yml b/.github/workflows/manual-sdk-release-artifacts.yml
index 947ca0a75..a265bf2d5 100644
--- a/.github/workflows/manual-sdk-release-artifacts.yml
+++ b/.github/workflows/manual-sdk-release-artifacts.yml
@@ -38,7 +38,7 @@ jobs:
     strategy:
       matrix:
         # Each of the platforms for which release-artifacts need generated.
-        os: [ ubuntu-22.04, windows-2022, macos-13 ]
+        os: [ ubuntu-22.04, windows-2022, macos-15-large ]
     runs-on: ${{ matrix.os }}
     outputs:
       hashes-linux: ${{ steps.release-sdk.outputs.hashes-linux }}
@@ -58,6 +58,27 @@ jobs:
           github_token: ${{secrets.GITHUB_TOKEN}}
           sdk_path: ${{ needs.split-input.outputs.sdk_path}}
           sdk_cmake_target: ${{ needs.split-input.outputs.sdk_cmake_target}}
+
+  release-sdk-mac-arm64:
+    needs: split-input
+    runs-on: macos-15
+    outputs:
+      hashes-macos-arm64: ${{ steps.release-sdk.outputs.hashes-macos }}
+    steps:
+      # https://github.com/actions/checkout/releases/tag/v4.3.0
+      - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955
+        with:
+          ref: ${{ inputs.tag }}
+      - id: release-sdk
+        name: Full release of ${{ needs.split-input.outputs.sdk_path }} (macOS arm64)
+        uses: ./.github/actions/sdk-release
+        with:
+          tag_name: ${{ inputs.tag }}
+          github_token: ${{secrets.GITHUB_TOKEN}}
+          sdk_path: ${{ needs.split-input.outputs.sdk_path}}
+          sdk_cmake_target: ${{ needs.split-input.outputs.sdk_cmake_target}}
+          mac_artifact_arch: 'arm64'
+
   release-sdk-provenance:
     needs: [ 'release-sdk' ]
     strategy:
@@ -74,3 +95,16 @@ jobs:
       upload-assets: true
       upload-tag-name: ${{ inputs.tag }}
       provenance-name: ${{ format('{0}-multiple-provenance.intoto.jsonl', matrix.os) }}
+
+  release-sdk-mac-arm64-provenance:
+    needs: [ 'release-sdk-mac-arm64' ]
+    permissions:
+      actions: read
+      id-token: write
+      contents: write
+    uses: slsa-framework/slsa-github-generator/.github/workflows/generator_generic_slsa3.yml@v2.1.0
+    with:
+      base64-subjects: "${{ needs.release-sdk-mac-arm64.outputs.hashes-macos-arm64 }}"
+      upload-assets: true
+      upload-tag-name: ${{ inputs.tag }}
+      provenance-name: 'macos-arm64-multiple-provenance.intoto.jsonl'
diff --git a/.github/workflows/release-please.yml b/.github/workflows/release-please.yml
index b8fa2f254..7401422a0 100644
--- a/.github/workflows/release-please.yml
+++ b/.github/workflows/release-please.yml
@@ -27,7 +27,7 @@ jobs:
     strategy:
       matrix:
         # Each of the platforms for which release-artifacts need generated.
-        os: [ ubuntu-22.04, windows-2022, macos-13 ]
+        os: [ ubuntu-22.04, windows-2022, macos-15-large ]
     runs-on: ${{ matrix.os }}
     needs: [ 'release-please' ]
     if: ${{ needs.release-please.outputs.package-client-released == 'true'}}
@@ -48,11 +48,30 @@ jobs:
           sdk_path: 'libs/client-sdk'
           sdk_cmake_target: 'launchdarkly-cpp-client'
 
+  release-client-mac-arm64:
+    runs-on: macos-15
+    needs: [ 'release-please' ]
+    if: ${{ needs.release-please.outputs.package-client-released == 'true'}}
+    outputs:
+      hashes-macos-arm64: ${{ steps.release-client.outputs.hashes-macos }}
+    steps:
+      # https://github.com/actions/checkout/releases/tag/v4.3.0
+      - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955
+      - id: release-client
+        name: Full release of libs/client-sdk (macOS arm64)
+        uses: ./.github/actions/sdk-release
+        with:
+          tag_name: ${{ needs.release-please.outputs.package-client-tag }}
+          github_token: ${{secrets.GITHUB_TOKEN}}
+          sdk_path: 'libs/client-sdk'
+          sdk_cmake_target: 'launchdarkly-cpp-client'
+          mac_artifact_arch: 'arm64'
+
   release-server:
     strategy:
       matrix:
         # Each of the platforms for which release-artifacts need generated.
-        os: [ ubuntu-22.04, windows-2022, macos-13 ]
+        os: [ ubuntu-22.04, windows-2022, macos-15-large ]
     runs-on: ${{ matrix.os }}
     needs: [ 'release-please' ]
     if: ${{ needs.release-please.outputs.package-server-released == 'true'}}
@@ -73,11 +92,30 @@ jobs:
           sdk_path: 'libs/server-sdk'
           sdk_cmake_target: 'launchdarkly-cpp-server'
 
+  release-server-mac-arm64:
+    runs-on: macos-15
+    needs: [ 'release-please' ]
+    if: ${{ needs.release-please.outputs.package-server-released == 'true'}}
+    outputs:
+      hashes-macos-arm64: ${{ steps.release-server.outputs.hashes-macos }}
+    steps:
+      # https://github.com/actions/checkout/releases/tag/v4.3.0
+      - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955
+      - id: release-server
+        name: Full release of libs/server-sdk (macOS arm64)
+        uses: ./.github/actions/sdk-release
+        with:
+          tag_name: ${{ needs.release-please.outputs.package-server-tag }}
+          github_token: ${{secrets.GITHUB_TOKEN}}
+          sdk_path: 'libs/server-sdk'
+          sdk_cmake_target: 'launchdarkly-cpp-server'
+          mac_artifact_arch: 'arm64'
+
   release-server-redis:
     strategy:
       matrix:
         # Each of the platforms for which release-artifacts need generated.
-        os: [ ubuntu-22.04, windows-2022, macos-13 ]
+        os: [ ubuntu-22.04, windows-2022, macos-15-large ]
     runs-on: ${{ matrix.os }}
     needs: [ 'release-please' ]
     if: ${{ needs.release-please.outputs.package-server-redis-released  == 'true'}}
@@ -98,6 +136,25 @@ jobs:
           sdk_path: 'libs/server-sdk-redis-source'
           sdk_cmake_target: 'launchdarkly-cpp-server-redis-source'
 
+  release-server-redis-mac-arm64:
+    runs-on: macos-15
+    needs: [ 'release-please' ]
+    if: ${{ needs.release-please.outputs.package-server-redis-released  == 'true'}}
+    outputs:
+      hashes-macos-arm64: ${{ steps.release-server-redis.outputs.hashes-macos }}
+    steps:
+      # https://github.com/actions/checkout/releases/tag/v4.3.0
+      - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955
+      - id: release-server-redis
+        name: Full release of libs/server-sdk-redis-source (macOS arm64)
+        uses: ./.github/actions/sdk-release
+        with:
+          tag_name: ${{ needs.release-please.outputs.package-server-redis-tag }}
+          github_token: ${{secrets.GITHUB_TOKEN}}
+          sdk_path: 'libs/server-sdk-redis-source'
+          sdk_cmake_target: 'launchdarkly-cpp-server-redis-source'
+          mac_artifact_arch: 'arm64'
+
   release-client-provenance:
     needs: [ 'release-please', 'release-client' ]
     strategy:
@@ -115,6 +172,19 @@ jobs:
       upload-tag-name: ${{ needs.release-please.outputs.package-client-tag }}
       provenance-name: ${{ format('{0}-client-multiple-provenance.intoto.jsonl', matrix.os) }}
 
+  release-client-mac-arm64-provenance:
+    needs: [ 'release-please', 'release-client-mac-arm64' ]
+    permissions:
+      actions: read
+      id-token: write
+      contents: write
+    uses: slsa-framework/slsa-github-generator/.github/workflows/generator_generic_slsa3.yml@v2.1.0
+    with:
+      base64-subjects: "${{ needs.release-client-mac-arm64.outputs.hashes-macos-arm64 }}"
+      upload-assets: true
+      upload-tag-name: ${{ needs.release-please.outputs.package-client-tag }}
+      provenance-name: 'macos-arm64-client-multiple-provenance.intoto.jsonl'
+
   release-server-provenance:
     needs: [ 'release-please', 'release-server' ]
     strategy:
@@ -132,6 +202,19 @@ jobs:
       upload-tag-name: ${{ needs.release-please.outputs.package-server-tag }}
       provenance-name: ${{ format('{0}-server-multiple-provenance.intoto.jsonl', matrix.os) }}
 
+  release-server-mac-arm64-provenance:
+    needs: [ 'release-please', 'release-server-mac-arm64' ]
+    permissions:
+      actions: read
+      id-token: write
+      contents: write
+    uses: slsa-framework/slsa-github-generator/.github/workflows/generator_generic_slsa3.yml@v2.1.0
+    with:
+      base64-subjects: "${{ needs.release-server-mac-arm64.outputs.hashes-macos-arm64 }}"
+      upload-assets: true
+      upload-tag-name: ${{ needs.release-please.outputs.package-server-tag }}
+      provenance-name: 'macos-arm64-server-multiple-provenance.intoto.jsonl'
+
   release-server-redis-provenance:
     needs: [ 'release-please', 'release-server-redis' ]
     strategy:
@@ -149,3 +232,15 @@ jobs:
       upload-tag-name: ${{ needs.release-please.outputs.package-server-redis-tag }}
       provenance-name: ${{ format('{0}-server-redis-multiple-provenance.intoto.jsonl', matrix.os) }}
 
+  release-server-redis-mac-arm64-provenance:
+    needs: [ 'release-please', 'release-server-redis-mac-arm64' ]
+    permissions:
+      actions: read
+      id-token: write
+      contents: write
+    uses: slsa-framework/slsa-github-generator/.github/workflows/generator_generic_slsa3.yml@v2.1.0
+    with:
+      base64-subjects: "${{ needs.release-server-redis-mac-arm64.outputs.hashes-macos-arm64 }}"
+      upload-assets: true
+      upload-tag-name: ${{ needs.release-please.outputs.package-server-redis-tag }}
+      provenance-name: 'macos-arm64-server-redis-multiple-provenance.intoto.jsonl'
diff --git a/.github/workflows/server-otel.yml b/.github/workflows/server-otel.yml
index a284a25d9..0ad3825a7 100644
--- a/.github/workflows/server-otel.yml
+++ b/.github/workflows/server-otel.yml
@@ -26,7 +26,7 @@ jobs:
           # We don't produce release artifacts.
           simulate_release: false
   build-otel-mac:
-    runs-on: macos-13
+    runs-on: macos-15
     steps:
       # https://github.com/actions/checkout/releases/tag/v4.3.0
       - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955
diff --git a/.github/workflows/server-redis.yml b/.github/workflows/server-redis.yml
index 82f31ca4b..0a73c4786 100644
--- a/.github/workflows/server-redis.yml
+++ b/.github/workflows/server-redis.yml
@@ -29,7 +29,7 @@ jobs:
           cmake_target: launchdarkly-cpp-server-redis-source
           simulate_release: true
   build-redis-mac:
-    runs-on: macos-13
+    runs-on: macos-15
     steps:
       # https://github.com/actions/checkout/releases/tag/v4.3.0
       - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955
diff --git a/.github/workflows/server.yml b/.github/workflows/server.yml
index 8d5f9abe0..f1b996dda 100644
--- a/.github/workflows/server.yml
+++ b/.github/workflows/server.yml
@@ -81,7 +81,7 @@ jobs:
           simulate_release: true
 
   build-test-server-mac:
-    runs-on: macos-13
+    runs-on: macos-15
     steps:
       # https://github.com/actions/checkout/releases/tag/v4.3.0
       - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955
@@ -92,7 +92,7 @@ jobs:
           simulate_release: true
 
   build-test-server-mac-curl:
-    runs-on: macos-13
+    runs-on: macos-15
     steps:
       # https://github.com/actions/checkout/releases/tag/v4.3.0
       - uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955