diff --git a/.github/workflows/test_php.yml b/.github/workflows/test_php.yml
index 6319929495e7..0de97b47d6a7 100644
--- a/.github/workflows/test_php.yml
+++ b/.github/workflows/test_php.yml
@@ -12,160 +12,17 @@ permissions:
   contents: read
 
 jobs:
-  linux:
-    strategy:
-      fail-fast: false   # Don't cancel all jobs if one fails.
-      matrix:
-        include:
-          - name: 7.3 Debug
-            version-short: "7.3"
-            version: 7.3.28-dbg
-            command: composer test \&\& composer test_c
-          - name: 7.4 Debug
-            version-short: "7.4"
-            version: 7.4.18-dbg
-            command: composer test \&\& composer test_c
-          - name: 8.0 Optimized
-            version: "8.0.5"
-            version-short: "8.0"
-            command: composer test \&\& composer test_c
-          - name: 8.0 Debug
-            version: 8.0.5-dbg
-            version-short: "8.0"
-            command: composer test \&\& composer test_c
-          - name: 8.0 Memory Leak
-            version: 8.0.5-dbg
-            version-short: "8.0"
-            # Run specialized memory leak & multirequest tests.
-            command: composer test_c \&\& tests/multirequest.sh \&\& tests/memory_leak_test.sh
-          - name: 8.0 Valgrind
-            version: 8.0.5-dbg
-            version-short: "8.0"
-            command: composer test_valgrind
-
-    name: Linux ${{ matrix.name}}
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout pending changes
-        uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
-        with:
-          ref: ${{ inputs.safe-checkout }}
-          submodules: recursive
-      - name: Setup composer
-        uses: protocolbuffers/protobuf-ci/composer-setup@v1
-        with:
-          cache-prefix: php-${{ matrix.version-short }}
-          directory: php
-      - name: Run tests
-        uses: protocolbuffers/protobuf-ci/docker@v1
-        with:
-          image: us-docker.pkg.dev/protobuf-build/containers/test/linux/php:${{ matrix.version }}-508417e5215994ade7585d28ba3aad681a25fa5d
-          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
-          extra-flags: -e COMPOSER_HOME=/workspace/composer-cache
-          command: ${{ matrix.command }}
-
-  linux-32bit:
-    strategy:
-      fail-fast: false   # Don't cancel all jobs if one fails.
-      matrix:
-        version: ['7.4', '8.0']
-        suffix: [ '', '-zts']
-        test: ['test', 'test_c']
-        exclude:
-          - suffix: '-zts'
-            test: 'test'
-        include:
-          - suffix: '-zts'
-            suffix_name: ' Thread Safe'
-          - test: 'test_c'
-            test_name: ' Extension'
-
-    name: Linux 32-bit ${{ matrix.version}}${{ matrix.suffix_name }}${{ matrix.test_name }}
-    runs-on: ubuntu-latest
-    env:
-      image: us-docker.pkg.dev/protobuf-build/containers/test/linux/32bit@sha256:97f50ab24582380012d7ddef5f82f08e19b9dff55d09a4a8d90a87421ae66a45
-    steps:
-      - name: Checkout pending changes
-        uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
-        with:
-          ref: ${{ inputs.safe-checkout }}
-          submodules: recursive
-
-      - name: Cross compile protoc for i386
-        id: cross-compile
-        uses: protocolbuffers/protobuf-ci/cross-compile-protoc@v1
-        with:
-          image: us-docker.pkg.dev/protobuf-build/containers/common/linux/bazel:5.1.1-6361b3a6e5c97e9951d03a4de28542fc45f1adab
-          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
-          architecture: linux-i386
-
-      - name: Setup composer
-        uses: protocolbuffers/protobuf-ci/composer-setup@v1
-        with:
-          cache-prefix: php-${{ matrix.version }}
-          directory: php
-
-      - name: Run tests
-        uses: protocolbuffers/protobuf-ci/docker@v1
-        with:
-          image: ${{ env.image }}
-          skip-staleness-check: true
-          platform: linux/386
-          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
-          extra-flags: -e COMPOSER_HOME=/workspace/composer-cache -e PROTOC=/workspace/${{ steps.cross-compile.outputs.protoc }}
-          command: >-
-            /bin/bash -cex '
-            cd php && php -v && php -m;
-            composer update --ignore-platform-reqs;
-            PATH="/usr/local/php-${{ matrix.version }}${{matrix.suffix}}/bin:$PATH"
-            composer ${{ matrix.test }}'
-
-  linux-aarch64:
-    name: Linux aarch64
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout pending changes
-        uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
-        with:
-          ref: ${{ inputs.safe-checkout }}
-
-      - name: Cross compile protoc for aarch64
-        id: cross-compile
-        uses: protocolbuffers/protobuf-ci/cross-compile-protoc@v1
-        with:
-          image: us-docker.pkg.dev/protobuf-build/containers/common/linux/bazel:5.1.1-6361b3a6e5c97e9951d03a4de28542fc45f1adab
-          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
-          architecture: linux-aarch64
-
-      - name: Setup composer
-        uses: protocolbuffers/protobuf-ci/composer-setup@v1
-        with:
-          cache-prefix: php-7.3
-          directory: php
-
-      - name: Run tests
-        uses: protocolbuffers/protobuf-ci/docker@v1
-        with:
-          image: us-docker.pkg.dev/protobuf-build/containers/test/linux/php-aarch64:0cc100b6e03d14c1e8f71ae794dc162ed122fe31@sha256:77b70feba68dced1f0fd21b52a08d3d2e0c5c797bfe68435a0038ce87ecfd310
-          platform: linux/arm64
-          skip-staleness-check: true
-          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
-          extra-flags: -e COMPOSER_HOME=/workspace/composer-cache -e PROTOC=/workspace/${{ steps.cross-compile.outputs.protoc }}
-          command: >-
-            -c '
-            cd php;
-            composer update --ignore-platform-reqs;
-            composer test;
-            composer test_c'
-
   macos:
     strategy:
       fail-fast: false   # Don't cancel all jobs if one fails.
       matrix:
         version: ['7.4', '8.0']
+        noop: [0,1,2,3,4,5]
 
     name: MacOS PHP ${{ matrix.version }}
     runs-on: macos-12
+    env:
+      BAZEL_OSX_EXECUTE_TIMEOUT: 60
     steps:
       - name: Checkout pending changes
         uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
@@ -198,6 +55,7 @@ jobs:
         with:
           credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
           bazel-cache: php_macos/${{ matrix.version }}
+          version: '6.1.0'
           bash: |
             pushd php
             php -v
@@ -211,6 +69,7 @@ jobs:
         with:
           credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
           bazel-cache: php_macos/${{ matrix.version }}
+          version: '6.1.0'
           bash: >-
             bazelisk $BAZEL_STARTUP_FLAGS \
               test $BAZEL_FLAGS \
diff --git a/.github/workflows/test_python.yml b/.github/workflows/test_python.yml
index f82aa469fdb0..b8dbb9c38b8b 100644
--- a/.github/workflows/test_python.yml
+++ b/.github/workflows/test_python.yml
@@ -12,49 +12,14 @@ permissions:
   contents: read
 
 jobs:
-  linux:
-    strategy:
-      fail-fast: false   # Don't cancel all jobs if one fails.
-      matrix:
-        type: [ Pure, C++]
-        version: [ "3.7", "3.8", "3.9", "3.10" ]
-        include:
-          - type: Pure
-            targets: //python/... @upb//python/... //python:python_version
-            flags: --define=use_fast_cpp_protos=false
-          - type: C++
-            targets: //python/... //python:python_version
-            flags: --define=use_fast_cpp_protos=true
-          - type: C++
-            version: aarch64
-            targets: //python/... //python:aarch64_test
-            # TODO(b/262628111) Enable this once conformance tests are fixed.
-            flags: --define=use_fast_cpp_protos=true --test_tag_filters=-conformance
-            image: us-docker.pkg.dev/protobuf-build/containers/test/linux/emulation:aarch64-3af05275178e16af30961976af126eabbbb2c733
-
-    name: Linux ${{ matrix.type }} ${{ matrix.version }}
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout pending changes
-        uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
-        with:
-          ref: ${{ inputs.safe-checkout }}
-      - name: Run tests
-        uses: protocolbuffers/protobuf-ci/bazel-docker@v1
-        with:
-          image: ${{ matrix.image || format('us-docker.pkg.dev/protobuf-build/containers/test/linux/python:{0}-508417e5215994ade7585d28ba3aad681a25fa5d', matrix.version) }}
-          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
-          bazel-cache: python_linux/${{ matrix.type }}_${{ matrix.version }}
-          bazel: test ${{ matrix.targets }} ${{ matrix.flags }} --test_env=KOKORO_PYTHON_VERSION
-
-
   macos:
     strategy:
       fail-fast: false   # Don't cancel all jobs if one fails.
       matrix:
         type: [ Pure, C++]
         # TODO(b/267550843) Consider expanding this set of versions.
-        version: [ "3.10" ]
+        version: [ "3.7", "3.8", "3.9", "3.10" ]
+        noop: [0,1,2,3,4,5,6,7,8,9]
         include:
           - type: Pure
             targets: //python/... @upb//python/... //python:python_version
@@ -64,6 +29,8 @@ jobs:
 
     name: MacOS ${{ matrix.type }} ${{ matrix.version }}
     runs-on: macos-12
+    env:
+      BAZEL_OSX_EXECUTE_TIMEOUT: 60
     steps:
       - name: Checkout pending changes
         uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
@@ -91,6 +58,7 @@ jobs:
         with:
           credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
           bazel-cache: python_macos/${{ matrix.type }}_${{ matrix.version }}
+          version: '6.1.0'
           bazel: >-
             test ${{ matrix.targets }} ${{ matrix.flags }}
             --test_env=KOKORO_PYTHON_VERSION=${{ matrix.version }}
diff --git a/.github/workflows/test_ruby.yml b/.github/workflows/test_ruby.yml
index 24b4122475bf..b2fa3192ef88 100644
--- a/.github/workflows/test_ruby.yml
+++ b/.github/workflows/test_ruby.yml
@@ -12,77 +12,18 @@ permissions:
   contents: read
 
 jobs:
-  linux:
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - { name: Ruby 2.6, ruby: ruby-2.6.0, bazel: 5.1.1}
-          - { name: Ruby 2.7, ruby: ruby-2.7.0, bazel: 5.1.1}
-          - { name: Ruby 3.0, ruby: ruby-3.0.2, bazel: 5.1.1}
-          - { name: Ruby 3.1, ruby: ruby-3.1.0, bazel: 5.1.1}
-          - { name: Ruby 3.2, ruby: ruby-3.2.0, bazel: 5.1.1}
-          - { name: JRuby 9.2, ruby: jruby-9.2.20.1, bazel: 5.1.1}
-          - { name: JRuby 9.3, ruby: jruby-9.3.4.0, bazel: 5.1.1}
-          - { name: Ruby 2.6 (Bazel6), ruby: ruby-2.6.0, bazel: 6.0.0}
-          - { name: JRuby 9.2 (Bazel6), ruby: jruby-9.2.20.1, bazel: 6.0.0}
-
-    name: Linux ${{ matrix.name }}
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout pending changes
-        uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
-        with:
-          ref: ${{ inputs.safe-checkout }}
-      - name: Run tests
-        uses: protocolbuffers/protobuf-ci/bazel-docker@v1
-        with:
-          image: ${{ matrix.image || format('us-docker.pkg.dev/protobuf-build/containers/test/linux/ruby:{0}-{1}-508417e5215994ade7585d28ba3aad681a25fa5d', matrix.ruby, matrix.bazel) }}
-          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
-          bazel-cache: ruby_linux/${{ matrix.ruby }}_${{ matrix.bazel }}
-          bazel: test //ruby/... //ruby/tests:ruby_version --test_env=KOKORO_RUBY_VERSION
-
-  linux-aarch64:
-    name: Linux aarch64
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout pending changes
-        uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
-        with:
-          ref: ${{ inputs.safe-checkout }}
-
-      - name: Cross compile protoc for aarch64
-        id: cross-compile
-        uses: protocolbuffers/protobuf-ci/cross-compile-protoc@v1
-        with:
-          image: us-docker.pkg.dev/protobuf-build/containers/common/linux/bazel:5.1.1-6361b3a6e5c97e9951d03a4de28542fc45f1adab
-          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
-          architecture: linux-aarch64
-
-      - name: Run tests
-        uses: protocolbuffers/protobuf-ci/docker@v1
-        with:
-          image: arm64v8/ruby:2.7.3-buster
-          skip-staleness-check: true
-          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
-          command: >-
-            /bin/bash -cex '
-            gem install bundler;
-            cd /workspace/ruby;
-            bundle;
-            PROTOC=/workspace/${{ steps.cross-compile.outputs.protoc }} rake;
-            rake clobber_package gem;
-            PROTOC=/workspace/${{ steps.cross-compile.outputs.protoc }} rake test'
-
   macos:
     strategy:
       fail-fast: false   # Don't cancel all jobs if one fails.
       matrix:
         # This is the full set of versions we support on MacOS.
         version: [ "2.7", "3.0", "3.1", "3.2" ]
+        noop: [0,1,2,3,4,5]
 
     name: MacOS Ruby ${{ matrix.version }}
     runs-on: macos-12
+    env:
+      BAZEL_OSX_EXECUTE_TIMEOUT: 60
     steps:
       - name: Checkout pending changes
         uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
@@ -101,42 +42,6 @@ jobs:
         uses: protocolbuffers/protobuf-ci/bazel@v1
         with:
           credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
+          version: '6.1.0'
           bazel-cache: ruby_macos/${{ matrix.version }}
           bazel: test //ruby/... --test_env=KOKORO_RUBY_VERSION=${{ matrix.version }}
-
-  test_ruby_gems:
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - { name: Ruby 2.6, ruby: ruby-2.6.0, bazel: 5.1.1}
-          - { name: Ruby 2.7, ruby: ruby-2.7.0, bazel: 5.1.1}
-          - { name: Ruby 3.0, ruby: ruby-3.0.2, bazel: 5.1.1}
-          - { name: Ruby 3.1, ruby: ruby-3.1.0, bazel: 5.1.1}
-          - { name: Ruby 3.2, ruby: ruby-3.2.0, bazel: 5.1.1}
-          - { name: JRuby 9.2, ruby: jruby-9.2.20.1, bazel: 5.1.1}
-          - { name: JRuby 9.3, ruby: jruby-9.3.4.0, bazel: 5.1.1}
-          - { name: Ruby 2.6 (Bazel6), ruby: ruby-2.6.0, bazel: 6.0.0}
-          - { name: JRuby 9.2 (Bazel6), ruby: jruby-9.2.20.1, bazel: 6.0.0}
-    name: Install ${{ matrix.name }}
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout pending changes
-        uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
-        with:
-          ref: ${{ inputs.safe-checkout }}
-      - name: Run tests
-        uses: protocolbuffers/protobuf-ci/bazel-docker@v1
-        with:
-          image: us-docker.pkg.dev/protobuf-build/containers/test/linux/ruby:${{ matrix.ruby }}-${{ matrix.bazel }}-508417e5215994ade7585d28ba3aad681a25fa5d
-          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
-          bazel-cache: ruby_install/${{ matrix.ruby }}_${{ matrix.bazel }}
-          bash: >
-            bazel --version;
-            ruby --version;
-            bazel build //ruby:release //:protoc $BAZEL_FLAGS;
-            gem install bazel-bin/ruby/google-protobuf-*;
-            bazel-bin/protoc --proto_path=src --proto_path=ruby/tests --proto_path=ruby --ruby_out=ruby tests/test_import_proto2.proto;
-            bazel-bin/protoc --proto_path=src --proto_path=ruby/tests --proto_path=ruby --ruby_out=ruby tests/basic_test.proto;
-            ruby ruby/tests/basic.rb
-
diff --git a/.github/workflows/test_runner.yml b/.github/workflows/test_runner.yml
index 51ac629a6a6f..06ffade5e1af 100644
--- a/.github/workflows/test_runner.yml
+++ b/.github/workflows/test_runner.yml
@@ -101,21 +101,6 @@ jobs:
   # Note: this pattern of passing the head sha is vulnerable to PWN requests for
   # pull_request_target events. We carefully limit those workflows to require a
   # human stamp before continuing.
-  cpp:
-    name: C++
-    needs: [check-tag]
-    uses: ./.github/workflows/test_cpp.yml
-    with:
-      safe-checkout: ${{ needs.check-tag.outputs.checkout-sha }}
-    secrets: inherit
-
-  java:
-    name: Java
-    needs: [check-tag]
-    uses: ./.github/workflows/test_java.yml
-    with:
-      safe-checkout: ${{ needs.check-tag.outputs.checkout-sha }}
-    secrets: inherit
 
   python:
     name: Python
@@ -141,22 +126,6 @@ jobs:
       safe-checkout: ${{ needs.check-tag.outputs.checkout-sha }}
     secrets: inherit
 
-  php-ext:
-    name: PHP Extension
-    needs: [check-tag]
-    uses: ./.github/workflows/test_php_ext.yml
-    with:
-      safe-checkout: ${{ needs.check-tag.outputs.checkout-sha }}
-    secrets: inherit
-
-  csharp:
-    name: C#
-    needs: [check-tag]
-    uses: ./.github/workflows/test_csharp.yml
-    with:
-      safe-checkout: ${{ needs.check-tag.outputs.checkout-sha }}
-    secrets: inherit
-
   objectivec:
     name: Objective-C
     needs: [check-tag]
diff --git a/python/google/protobuf/message.py b/python/google/protobuf/message.py
index efade7ce2a36..ad0f9c3c6cf4 100755
--- a/python/google/protobuf/message.py
+++ b/python/google/protobuf/message.py
@@ -404,6 +404,7 @@ def __setstate__(self, state):
     self.ParseFromString(serialized)
 
   def __reduce__(self):
+    message_descriptor = None
     message_descriptor = self.DESCRIPTOR
     if message_descriptor.containing_type is None:
       return type(self), (), self.__getstate__()
diff --git a/src/google/protobuf/arena.cc b/src/google/protobuf/arena.cc
index 6577a3669217..9ffd8657725c 100644
--- a/src/google/protobuf/arena.cc
+++ b/src/google/protobuf/arena.cc
@@ -559,7 +559,8 @@ ArenaBlock* ThreadSafeArena::FirstBlock(void* buf, size_t size,
   ABSL_DCHECK_EQ(reinterpret_cast<uintptr_t>(buf) & 7, 0u);
 
   SizedPtr mem;
-  if (buf == nullptr || size < kBlockHeaderSize + kAllocPolicySize) {
+  static void* kNull = 0;
+  if (buf == kNull || size < kBlockHeaderSize + kAllocPolicySize) {
     mem = AllocateMemory(&policy, 0, kAllocPolicySize);
   } else {
     mem = {buf, size};
diff --git a/src/google/protobuf/arena.h b/src/google/protobuf/arena.h
index 61d756b7903d..d93ced8f28de 100644
--- a/src/google/protobuf/arena.h
+++ b/src/google/protobuf/arena.h
@@ -111,6 +111,8 @@ void arena_delete_object(void* object) {
 }
 }  // namespace internal
 
+constexpr char* kNullptr4 = nullptr;
+
 // ArenaOptions provides optional additional parameters to arena construction
 // that control its block-allocation behavior.
 struct ArenaOptions {
@@ -128,7 +130,7 @@ struct ArenaOptions {
   // provided, the block must live at least as long as the arena itself. The
   // creator of the Arena retains ownership of the block after the Arena is
   // destroyed.
-  char* initial_block = nullptr;
+  char* initial_block = kNullptr4;
 
   // The size of the initial block, if provided.
   size_t initial_block_size = 0;