diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9b4851951..d77071aba 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -68,7 +68,18 @@ jobs:
           # Extra ubuntu latest job
           - runs-on: ubuntu-latest
             python: '3.11'
-
+          - runs-on: ubuntu-latest
+            python: '3.12'
+            args: >
+              -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
+          - runs-on: macos-13
+            python: '3.12'
+            args: >
+              -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
+          - runs-on: windows-2022
+            python: '3.12'
+            args: >
+              -DCMAKE_CXX_FLAGS="/DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT /GR /EHsc"
 
     name: "🐍 ${{ matrix.python }} • ${{ matrix.runs-on }} • x64 ${{ matrix.args }}"
     runs-on: ${{ matrix.runs-on }}
diff --git a/.github/workflows/ci_sh_def.yml b/.github/workflows/ci_sh_def.yml
deleted file mode 100644
index 68a739850..000000000
--- a/.github/workflows/ci_sh_def.yml
+++ /dev/null
@@ -1,1262 +0,0 @@
-# PLEASE KEEP THIS GROUP OF FILES IN SYNC AT ALL TIMES:
-#     ci.yml
-#     ci_sh_def.yml
-#     ci_sh_def.yml.patch
-# To import changes made to ci.yml *** ESPECIALLY AFTER `git merge master` ***:
-#     patch -i ci_sh_def.yml.patch -o ci_sh_def.yml
-# To update the patch file after making changes to ci_sh.yml:
-#     diff -u ci.yml ci_sh_def.yml > ci_sh_def.yml.patch
-#     git commit -a -m 'Tracking ci.yml changes from master.'
-#
-# Thanks a lot to @rhaschke for PR #2930!
-
-name: "CI-SH-DEF"
-
-on:
-  workflow_dispatch:
-  pull_request:
-  push:
-    branches:
-      - master
-      - stable
-      - smart_holder
-      - v*
-
-permissions: read-all
-
-concurrency:
-  group: test-sh-def-${{ github.ref }}
-  cancel-in-progress: true
-
-env:
-  PIP_BREAK_SYSTEM_PACKAGES: 1
-  PIP_ONLY_BINARY: numpy
-  FORCE_COLOR: 3
-  PYTEST_TIMEOUT: 300
-  # For cmake:
-  VERBOSE: 1
-
-jobs:
-  # This is the "main" test suite, which tests a large number of different
-  # versions of default compilers and Python versions in GitHub Actions.
-  standard:
-    strategy:
-      fail-fast: false
-      matrix:
-        runs-on: [ubuntu-20.04, windows-2022, macos-13]
-        python:
-        - '3.8'
-        - '3.9'
-        - '3.12'
-        - '3.13'
-        - 'pypy-3.8'
-        - 'pypy-3.9'
-        - 'pypy-3.10'
-
-        # Items in here will either be added to the build matrix (if not
-        # present), or add new keys to an existing matrix element if all the
-        # existing keys match.
-        #
-        # We support an optional key: args, for cmake args
-        include:
-          # Just add a key
-          - runs-on: ubuntu-20.04
-            python: '3.8'
-            args: >
-              -DPYBIND11_FINDPYTHON=ON
-              -DCMAKE_CXX_FLAGS="-D_=1"
-            exercise_D_: 1
-          - runs-on: ubuntu-20.04
-            python: 'pypy-3.8'
-            args: >
-              -DPYBIND11_FINDPYTHON=ON
-          - runs-on: windows-2019
-            python: '3.8'
-            args: >
-              -DPYBIND11_FINDPYTHON=ON
-          # Inject a couple Windows 2019 runs
-          - runs-on: windows-2019
-            python: '3.9'
-          # Extra ubuntu latest job
-          - runs-on: ubuntu-latest
-            python: '3.11'
-
-
-    name: "🐍 ${{ matrix.python }} • ${{ matrix.runs-on }} • x64 ${{ matrix.args }}"
-    runs-on: ${{ matrix.runs-on }}
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v5
-      with:
-        python-version: ${{ matrix.python }}
-        allow-prereleases: true
-
-    - name: Setup Boost (Linux)
-      # Can't use boost + define _
-      if: runner.os == 'Linux' && matrix.exercise_D_ != 1
-      run: sudo apt-get install libboost-dev
-
-    - name: Setup Boost (macOS)
-      if: runner.os == 'macOS'
-      run: brew install boost
-
-    - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v2.0
-
-    - name: Cache wheels
-      if: runner.os == 'macOS'
-      uses: actions/cache@v4
-      with:
-        # This path is specific to macOS - we really only need it for PyPy NumPy wheels
-        # See https://github.com/actions/cache/blob/master/examples.md#python---pip
-        # for ways to do this more generally
-        path: ~/Library/Caches/pip
-        # Look to see if there is a cache hit for the corresponding requirements file
-        key: ${{ runner.os }}-pip-${{ matrix.python }}-x64-${{ hashFiles('tests/requirements.txt') }}
-
-    - name: Prepare env
-      run: |
-        python -m pip install -r tests/requirements.txt
-
-    - name: Setup annotations on Linux
-      if: runner.os == 'Linux'
-      run: python -m pip install pytest-github-actions-annotate-failures
-
-    # First build - C++11 mode and inplace
-    # More-or-less randomly adding -DPYBIND11_SIMPLE_GIL_MANAGEMENT=ON here
-    # (same for PYBIND11_NUMPY_1_ONLY, but requires a NumPy 1.x at runtime).
-    - name: Configure C++11 ${{ matrix.args }}
-      run: >
-        cmake -S . -B .
-        -DPYBIND11_WERROR=ON
-        -DPYBIND11_DISABLE_HANDLE_TYPE_NAME_DEFAULT_IMPLEMENTATION=ON
-        -DPYBIND11_SIMPLE_GIL_MANAGEMENT=ON
-        -DPYBIND11_NUMPY_1_ONLY=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=11
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT ${{runner.os == 'Windows' && '/GR /EHsc' || ''}}"
-        ${{ matrix.args }}
-
-    - name: Build C++11
-      run: cmake --build . -j 2
-
-    - name: Python tests C++11
-      run: cmake --build . --target pytest -j 2
-
-    - name: C++11 tests
-      run: cmake --build . --target cpptest -j 2
-
-    - name: Interface test C++11
-      run: cmake --build . --target test_cmake_build
-
-    - name: Clean directory
-      run: git clean -fdx
-
-    # Second build - C++17 mode and in a build directory
-    # More-or-less randomly adding -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF here.
-    # (same for PYBIND11_NUMPY_1_ONLY, but requires a NumPy 1.x at runtime).
-    - name: Configure C++17
-      run: >
-        cmake -S . -B build2
-        -DPYBIND11_WERROR=ON
-        -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
-        -DPYBIND11_NUMPY_1_ONLY=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=17
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT ${{runner.os == 'Windows' && '/GR /EHsc' || ''}}"
-        ${{ matrix.args }}
-
-    - name: Build
-      run: cmake --build build2 -j 2
-
-    - name: Python tests
-      run: cmake --build build2 --target pytest
-
-    - name: C++ tests
-      run: cmake --build build2 --target cpptest
-
-    # Third build - C++17 mode with unstable ABI
-    - name: Configure (unstable ABI)
-      run: >
-        cmake -S . -B build3
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=17
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT ${{runner.os == 'Windows' && '/GR /EHsc' || ''}}"
-        -DPYBIND11_INTERNALS_VERSION=10000000
-        ${{ matrix.args }}
-
-    - name: Build (unstable ABI)
-      run: cmake --build build3 -j 2
-
-    - name: Python tests (unstable ABI)
-      run: cmake --build build3 --target pytest
-
-    - name: Interface test
-      run: cmake --build build2 --target test_cmake_build
-
-    # This makes sure the setup_helpers module can build packages using
-    # setuptools
-    - name: Setuptools helpers test
-      run: |
-        pip install setuptools
-        pytest tests/extra_setuptools
-      if: "!(matrix.runs-on == 'windows-2022')"
-
-  manylinux:
-    name: Manylinux on 🐍 3.13t • GIL
-    runs-on: ubuntu-latest
-    timeout-minutes: 40
-    container: quay.io/pypa/musllinux_1_2_x86_64:latest
-    steps:
-      - uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
-
-      - name: Prepare venv
-        run: python3.13t -m venv .venv
-
-      - name: Install Python deps
-        run: .venv/bin/pip install -r tests/requirements.txt
-
-      - name: Configure C++11
-        run: >
-          cmake -S. -Bbuild
-          -DPYBIND11_WERROR=ON
-          -DDOWNLOAD_CATCH=ON
-          -DDOWNLOAD_EIGEN=ON
-          -DPython_ROOT_DIR=.venv
-          -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-
-      - name: Build C++11
-        run: cmake --build build -j2
-
-      - name: Python tests C++11
-        run: cmake --build build --target pytest -j2
-
-  deadsnakes:
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-        # TODO: Fails on 3.10, investigate
-        # JOB DISABLED (NEEDS WORK): https://github.com/pybind/pybind11/issues/4889
-        # - python-version: "3.9"
-        #   python-debug: true
-        #   valgrind: true
-        - python-version: "3.11"
-          python-debug: false
-
-    name: "🐍 ${{ matrix.python-version }}${{ matrix.python-debug && '-dbg' || '' }} (deadsnakes)${{ matrix.valgrind && ' • Valgrind' || '' }} • x64"
-    runs-on: ubuntu-20.04
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Setup Python ${{ matrix.python-version }} (deadsnakes)
-      uses: deadsnakes/action@v3.1.0
-      with:
-        python-version: ${{ matrix.python-version }}
-        debug: ${{ matrix.python-debug }}
-
-    - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v2.0
-
-    - name: Valgrind cache
-      if: matrix.valgrind
-      uses: actions/cache@v4
-      id: cache-valgrind
-      with:
-        path: valgrind
-        key: 3.16.1 # Valgrind version
-
-    - name: Compile Valgrind
-      if: matrix.valgrind && steps.cache-valgrind.outputs.cache-hit != 'true'
-      run: |
-        VALGRIND_VERSION=3.16.1
-        curl https://sourceware.org/pub/valgrind/valgrind-$VALGRIND_VERSION.tar.bz2 -o - | tar xj
-        mv valgrind-$VALGRIND_VERSION valgrind
-        cd valgrind
-        ./configure
-        make -j 2 > /dev/null
-
-    - name: Install Valgrind
-      if: matrix.valgrind
-      working-directory: valgrind
-      run: |
-        sudo make install
-        sudo apt-get update
-        sudo apt-get install libc6-dbg  # Needed by Valgrind
-
-    - name: Prepare env
-      run: |
-        python -m pip install -r tests/requirements.txt
-
-    - name: Configure
-      run: >
-        cmake -S . -B build
-        -DCMAKE_BUILD_TYPE=Debug
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=17
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-
-    - name: Build
-      run: cmake --build build -j 2
-
-    - name: Python tests
-      run: cmake --build build --target pytest
-
-    - name: C++ tests
-      run: cmake --build build --target cpptest
-
-    - name: Run Valgrind on Python tests
-      if: matrix.valgrind
-      run: cmake --build build --target memcheck
-
-
-  # Testing on clang using the excellent silkeh clang docker images
-  clang:
-    runs-on: ubuntu-latest
-    strategy:
-      fail-fast: false
-      matrix:
-        clang:
-          - dev
-        std:
-          - 11
-        container_suffix:
-          - ""
-        include:
-          - clang: 5
-            std: 14
-          - clang: 11
-            std: 20
-          - clang: 12
-            std: 20
-          - clang: 13
-            std: 20
-          - clang: 14
-            std: 20
-          - clang: 15
-            std: 20
-            container_suffix: "-bullseye"
-          - clang: 16
-            std: 20
-            container_suffix: "-bullseye"
-          - clang: 17
-            std: 20
-            container_suffix: "-bookworm"
-          - clang: 18
-            std: 20
-            container_suffix: "-bookworm"
-
-    name: "🐍 3 • Clang ${{ matrix.clang }} • C++${{ matrix.std }} • x64"
-    container: "silkeh/clang:${{ matrix.clang }}${{ matrix.container_suffix }}"
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Add wget and python3
-      run: apt-get update && apt-get install -y python3-dev python3-numpy python3-pytest libeigen3-dev
-
-    - name: Configure
-      shell: bash
-      run: >
-        cmake -S . -B build
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DCMAKE_CXX_STANDARD=${{ matrix.std }}
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-
-    - name: Build
-      run: cmake --build build -j 2
-
-    - name: Python tests
-      run: cmake --build build --target pytest
-
-    - name: C++ tests
-      run: cmake --build build --target cpptest
-
-    - name: Interface test
-      run: cmake --build build --target test_cmake_build
-
-
-  # Testing NVCC; forces sources to behave like .cu files
-  cuda:
-    runs-on: ubuntu-latest
-    name: "🐍 3.10 • CUDA 12.2 • Ubuntu 22.04"
-    container: nvidia/cuda:12.2.0-devel-ubuntu22.04
-
-    steps:
-    - uses: actions/checkout@v4
-
-    # tzdata will try to ask for the timezone, so set the DEBIAN_FRONTEND
-    - name: Install 🐍 3
-      run: apt-get update && DEBIAN_FRONTEND="noninteractive" apt-get install -y cmake git python3-dev python3-pytest python3-numpy
-
-    - name: Configure
-      run: cmake -S . -B build -DPYBIND11_CUDA_TESTS=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-
-    - name: Build
-      run: cmake --build build -j2 --verbose
-
-    - name: Python tests
-      run: cmake --build build --target pytest
-
-
-# TODO: Internal compiler error - report to NVidia
-#  # Testing CentOS 8 + PGI compilers
-#  centos-nvhpc8:
-#    runs-on: ubuntu-latest
-#    name: "🐍 3 • CentOS8 / PGI 20.11 • x64"
-#    container: centos:8
-#
-#    steps:
-#    - uses: actions/checkout@v4
-#
-#    - name: Add Python 3 and a few requirements
-#      run: yum update -y && yum install -y git python3-devel python3-numpy python3-pytest make environment-modules
-#
-#    - name: Install CMake with pip
-#      run: |
-#        python3 -m pip install --upgrade pip
-#        python3 -m pip install cmake --prefer-binary
-#
-#    - name: Install NVidia HPC SDK
-#      run: >
-#        yum -y install
-#        https://developer.download.nvidia.com/hpc-sdk/20.11/nvhpc-20-11-20.11-1.x86_64.rpm
-#        https://developer.download.nvidia.com/hpc-sdk/20.11/nvhpc-2020-20.11-1.x86_64.rpm
-#
-#    - name: Configure
-#      shell: bash
-#      run: |
-#        source /etc/profile.d/modules.sh
-#        module load /opt/nvidia/hpc_sdk/modulefiles/nvhpc/20.11
-#        cmake -S . -B build -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_STANDARD=14 -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-#
-#    - name: Build
-#      run: cmake --build build -j 2 --verbose
-#
-#    - name: Python tests
-#      run: cmake --build build --target pytest
-#
-#    - name: C++ tests
-#      run: cmake --build build --target cpptest
-#
-#    - name: Interface test
-#      run: cmake --build build --target test_cmake_build
-
-
-  # Testing on Ubuntu + NVHPC (previous PGI) compilers, which seems to require more workarounds
-  ubuntu-nvhpc7:
-    runs-on: ubuntu-20.04
-    name: "🐍 3 • NVHPC 23.5 • C++17 • x64"
-
-    env:
-      # tzdata will try to ask for the timezone, so set the DEBIAN_FRONTEND
-      DEBIAN_FRONTEND: 'noninteractive'
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Add NVHPC Repo
-      run: |
-        echo 'deb [trusted=yes] https://developer.download.nvidia.com/hpc-sdk/ubuntu/amd64 /' | \
-          sudo tee /etc/apt/sources.list.d/nvhpc.list
-
-    - name: Install 🐍 3 & NVHPC
-      run: |
-        sudo apt-get update -y && \
-        sudo apt-get install -y cmake environment-modules git python3-dev python3-pip python3-numpy && \
-        sudo apt-get install -y --no-install-recommends nvhpc-23-5 && \
-        sudo rm -rf /var/lib/apt/lists/*
-        python3 -m pip install --upgrade pip
-        python3 -m pip install --upgrade pytest
-
-    # On some systems, you many need further workarounds:
-    # https://github.com/pybind/pybind11/pull/2475
-    - name: Configure
-      shell: bash
-      run: |
-        source /etc/profile.d/modules.sh
-        module load /opt/nvidia/hpc_sdk/modulefiles/nvhpc/23.5
-        cmake -S . -B build -DDOWNLOAD_CATCH=ON \
-                            -DCMAKE_CXX_STANDARD=17 \
-                            -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") \
-                            -DCMAKE_CXX_FLAGS="-Wc,--pending_instantiations=0 -DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT" \
-                            -DPYBIND11_TEST_FILTER="test_smart_ptr.cpp"
-
-    - name: Build
-      run: cmake --build build -j 2 --verbose
-
-    - name: Python tests
-      run: cmake --build build --target pytest
-
-    - name: C++ tests
-      run: cmake --build build --target cpptest
-
-    - name: Interface test
-      run: cmake --build build --target test_cmake_build
-
-
-  # Testing on GCC using the GCC docker images (only recent images supported)
-  gcc:
-    runs-on: ubuntu-latest
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - { gcc: 9, std: 20 }
-          - { gcc: 10, std: 17 }
-          - { gcc: 10, std: 20 }
-          - { gcc: 11, std: 20 }
-          - { gcc: 12, std: 20 }
-          - { gcc: 13, std: 20 }
-
-    name: "🐍 3 • GCC ${{ matrix.gcc }} • C++${{ matrix.std }}• x64"
-    container: "gcc:${{ matrix.gcc }}"
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Add Python 3
-      run: apt-get update; apt-get install -y python3-dev python3-numpy python3-pytest python3-pip libeigen3-dev
-
-    - name: Update pip
-      run: python3 -m pip install --upgrade pip
-
-    - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v2.0
-
-    - name: Configure
-      shell: bash
-      run: >
-        cmake -S . -B build
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DCMAKE_CXX_STANDARD=${{ matrix.std }}
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-
-    - name: Build
-      run: cmake --build build -j 2
-
-    - name: Python tests
-      run: cmake --build build --target pytest
-
-    - name: C++ tests
-      run: cmake --build build --target cpptest
-
-    - name: Interface test
-      run: cmake --build build --target test_cmake_build
-
-    - name: Configure - Exercise cmake -DPYBIND11_TEST_OVERRIDE
-      if: matrix.gcc == '12'
-      shell: bash
-      run: >
-        cmake -S . -B build_partial
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DCMAKE_CXX_STANDARD=${{ matrix.std }}
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-        "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
-
-    - name: Build - Exercise cmake -DPYBIND11_TEST_OVERRIDE
-      if: matrix.gcc == '12'
-      run: cmake --build build_partial -j 2
-
-    - name: Python tests - Exercise cmake -DPYBIND11_TEST_OVERRIDE
-      if: matrix.gcc == '12'
-      run: cmake --build build_partial --target pytest
-
-  # Testing on ICC using the oneAPI apt repo
-  icc:
-    runs-on: ubuntu-20.04
-
-    name: "🐍 3 • ICC latest • x64"
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Add apt repo
-      run: |
-        sudo apt-get update
-        sudo apt-get install -y wget build-essential pkg-config cmake ca-certificates gnupg
-        wget https://apt.repos.intel.com/intel-gpg-keys/GPG-PUB-KEY-INTEL-SW-PRODUCTS-2023.PUB
-        sudo apt-key add GPG-PUB-KEY-INTEL-SW-PRODUCTS-2023.PUB
-        echo "deb https://apt.repos.intel.com/oneapi all main" | sudo tee /etc/apt/sources.list.d/oneAPI.list
-
-    - name: Add ICC & Python 3
-      run: sudo apt-get update; sudo apt-get install -y intel-oneapi-compiler-dpcpp-cpp-and-cpp-classic cmake python3-dev python3-numpy python3-pytest python3-pip
-
-    - name: Update pip
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        python3 -m pip install --upgrade pip
-
-    - name: Install dependencies
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        python3 -m pip install -r tests/requirements.txt
-
-    - name: Configure C++11
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake -S . -B build-11     \
-        -DPYBIND11_WERROR=ON    \
-        -DDOWNLOAD_CATCH=ON     \
-        -DDOWNLOAD_EIGEN=OFF    \
-        -DCMAKE_CXX_STANDARD=11             \
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"  \
-        -DCMAKE_CXX_COMPILER=$(which icpc)  \
-        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-
-    - name: Build C++11
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-11 -j 2 -v
-
-    - name: Python tests C++11
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        sudo service apport stop
-        cmake --build build-11 --target check
-
-    - name: C++ tests C++11
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-11 --target cpptest
-
-    - name: Interface test C++11
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-11 --target test_cmake_build
-
-    - name: Configure C++17
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake -S . -B build-17     \
-        -DPYBIND11_WERROR=ON    \
-        -DDOWNLOAD_CATCH=ON     \
-        -DDOWNLOAD_EIGEN=OFF    \
-        -DCMAKE_CXX_STANDARD=17             \
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"  \
-        -DCMAKE_CXX_COMPILER=$(which icpc)  \
-        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-
-    - name: Build C++17
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-17 -j 2 -v
-
-    - name: Python tests C++17
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        sudo service apport stop
-        cmake --build build-17 --target check
-
-    - name: C++ tests C++17
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-17 --target cpptest
-
-    - name: Interface test C++17
-      run: |
-        set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-17 --target test_cmake_build
-
-
-  # Testing on CentOS (manylinux uses a centos base).
-  centos:
-    runs-on: ubuntu-latest
-    strategy:
-      fail-fast: false
-      matrix:
-        container:
-          - "almalinux:8"
-          - "almalinux:9"
-
-    name: "🐍 3 • ${{ matrix.container }} • x64"
-    container: "${{ matrix.container }}"
-
-    steps:
-    - name: Latest actions/checkout
-      uses: actions/checkout@v4
-
-    - name: Add Python 3.8
-      if: matrix.container == 'almalinux:8'
-      run: dnf update -y && dnf install -y python38-devel gcc-c++ make git
-
-    - name: Add Python 3 (default)
-      if: matrix.container != 'almalinux:8'
-      run: dnf update -y && dnf install -y python3-devel gcc-c++ make git
-
-    - name: Update pip
-      run: python3 -m pip install --upgrade pip
-
-    - name: Install dependencies
-      run: |
-        python3 -m pip install cmake -r tests/requirements.txt
-
-    - name: Ensure NumPy 2 is used (required Python >= 3.9)
-      if: matrix.container == 'almalinux:9'
-      run: |
-        python3 -m pip install 'numpy>=2.0.0b1' 'scipy>=1.13.0rc1'
-
-    - name: Configure
-      shell: bash
-      run: >
-        cmake -S . -B build
-        -DCMAKE_BUILD_TYPE=MinSizeRel
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=11
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-
-    - name: Build
-      run: cmake --build build -j 2
-
-    - name: Python tests
-      run: cmake --build build --target pytest
-
-    - name: C++ tests
-      run: cmake --build build --target cpptest
-
-    - name: Interface test
-      run: cmake --build build --target test_cmake_build
-
-
-  # This tests an "install" with the CMake tools
-  install-classic:
-    name: "🐍 3.9 • Debian • x86 •  Install"
-    runs-on: ubuntu-latest
-    container: i386/debian:bullseye
-
-    steps:
-    - uses: actions/checkout@v1  # v1 is required to run inside docker
-
-    - name: Install requirements
-      run: |
-        apt-get update
-        apt-get install -y git make cmake g++ libeigen3-dev python3-dev python3-pip
-        pip3 install "pytest==6.*"
-
-    - name: Configure for install
-      run: >
-        cmake .
-        -DPYBIND11_INSTALL=1 -DPYBIND11_TEST=0
-        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-
-    - name: Make and install
-      run: make install
-
-    - name: Copy tests to new directory
-      run: cp -a tests /pybind11-tests
-
-    - name: Make a new test directory
-      run: mkdir /build-tests
-
-    - name: Configure tests
-      run: >
-        cmake ../pybind11-tests
-        -DDOWNLOAD_CATCH=ON
-        -DPYBIND11_WERROR=ON
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-      working-directory: /build-tests
-
-    - name: Python tests
-      run: make pytest -j 2
-      working-directory: /build-tests
-
-
-  # This verifies that the documentation is not horribly broken, and does a
-  # basic validation check on the SDist.
-  doxygen:
-    name: "Documentation build test"
-    runs-on: ubuntu-latest
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - uses: actions/setup-python@v5
-      with:
-        python-version: "3.x"
-
-    - name: Install Doxygen
-      run: sudo apt-get install -y doxygen librsvg2-bin # Changed to rsvg-convert in 20.04
-
-    - name: Build docs
-      run: pipx run nox -s docs
-
-    - name: Make SDist
-      run: pipx run nox -s build -- --sdist
-
-    - run: git status --ignored
-
-    - name: Check local include dir
-      run: >
-        ls pybind11;
-        python3 -c "import pybind11, pathlib; assert (a := pybind11.get_include()) == (b := str(pathlib.Path('include').resolve())), f'{a} != {b}'"
-
-    - name: Compare Dists (headers only)
-      working-directory: include
-      run: |
-        python3 -m pip install --user -U ../dist/*.tar.gz
-        installed=$(python3 -c "import pybind11; print(pybind11.get_include() + '/pybind11')")
-        diff -rq $installed ./pybind11
-
-  win32:
-    strategy:
-      fail-fast: false
-      matrix:
-        python:
-        - '3.8'
-        - '3.9'
-        - '3.10'
-        - '3.11'
-        - '3.12'
-
-        include:
-          - python: '3.12'
-            args: -DCMAKE_CXX_STANDARD=20
-          - python: '3.11'
-            args: -DCMAKE_CXX_STANDARD=20
-          - python: '3.10'
-            args: -DCMAKE_CXX_STANDARD=20
-          - python: '3.9'
-            args: -DCMAKE_CXX_STANDARD=20
-          - python: '3.8'
-            args: -DCMAKE_CXX_STANDARD=17
-
-
-    name: "🐍 ${{ matrix.python }} • MSVC 2019 • x86 ${{ matrix.args }}"
-    runs-on: windows-2019
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v5
-      with:
-        python-version: ${{ matrix.python }}
-        architecture: x86
-
-    - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v2.0
-
-    - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.13.0
-      with:
-        arch: x86
-
-    - name: Prepare env
-      run: |
-        python -m pip install -r tests/requirements.txt
-
-    # First build - C++11 mode and inplace
-    - name: Configure ${{ matrix.args }}
-      run: >
-        cmake -S . -B build
-        -G "Visual Studio 16 2019" -A Win32
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_FLAGS="/GR /EHsc /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-        ${{ matrix.args }}
-    - name: Build C++11
-      run: cmake --build build -j 2
-
-    - name: Python tests
-      run: cmake --build build -t pytest
-
-  win32-debug:
-    strategy:
-      fail-fast: false
-      matrix:
-        python:
-        - 3.8
-        - 3.9
-
-        include:
-          - python: 3.9
-            args: -DCMAKE_CXX_STANDARD=20
-          - python: 3.8
-            args: -DCMAKE_CXX_STANDARD=17
-
-    name: "🐍 ${{ matrix.python }} • MSVC 2019 (Debug) • x86 ${{ matrix.args }}"
-    runs-on: windows-2019
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v5
-      with:
-        python-version: ${{ matrix.python }}
-        architecture: x86
-
-    - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v2.0
-
-    - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.13.0
-      with:
-        arch: x86
-
-    - name: Prepare env
-      run: |
-        python -m pip install -r tests/requirements.txt
-
-    # First build - C++11 mode and inplace
-    - name: Configure ${{ matrix.args }}
-      run: >
-        cmake -S . -B build
-        -G "Visual Studio 16 2019" -A Win32
-        -DCMAKE_BUILD_TYPE=Debug
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_FLAGS="/GR /EHsc /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-        ${{ matrix.args }}
-    - name: Build C++11
-      run: cmake --build build --config Debug -j 2
-
-    - name: Python tests
-      run: cmake --build build --config Debug -t pytest
-
-
-  windows-2022:
-    strategy:
-      fail-fast: false
-      matrix:
-        python:
-        - 3.9
-
-    name: "🐍 ${{ matrix.python }} • MSVC 2022 C++20 • x64"
-    runs-on: windows-2022
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Setup Python ${{ matrix.python }}
-      uses: actions/setup-python@v5
-      with:
-        python-version: ${{ matrix.python }}
-
-    - name: Prepare env
-      # Ensure use of NumPy 2 (via NumPy nightlies but can be changed soon)
-      run: |
-        python3 -m pip install -r tests/requirements.txt
-        python3 -m pip install 'numpy>=2.0.0b1' 'scipy>=1.13.0rc1'
-
-    - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v2.0
-
-    - name: Configure C++20
-      run: >
-        cmake -S . -B build
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=20
-        -DCMAKE_CXX_FLAGS="/GR /EHsc /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-
-    - name: Build C++20
-      run: cmake --build build -j 2
-
-    - name: Python tests
-      run: cmake --build build --target pytest
-
-    - name: C++20 tests
-      run: cmake --build build --target cpptest -j 2
-
-    - name: Interface test C++20
-      run: cmake --build build --target test_cmake_build
-
-    - name: Configure C++20 - Exercise cmake -DPYBIND11_TEST_OVERRIDE
-      run: >
-        cmake -S . -B build_partial
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=20
-        -DCMAKE_CXX_FLAGS="/GR /EHsc /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-        "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
-
-    - name: Build C++20 - Exercise cmake -DPYBIND11_TEST_OVERRIDE
-      run: cmake --build build_partial -j 2
-
-    - name: Python tests - Exercise cmake -DPYBIND11_TEST_OVERRIDE
-      run: cmake --build build_partial --target pytest
-
-  mingw:
-    name: "🐍 3 • windows-latest • ${{ matrix.sys }}"
-    runs-on: windows-latest
-    defaults:
-      run:
-        shell: msys2 {0}
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - { sys: mingw64, env: x86_64 }
-          - { sys: mingw32, env: i686 }
-    steps:
-    - uses: msys2/setup-msys2@v2
-      with:
-        msystem: ${{matrix.sys}}
-        install: >-
-          git
-          mingw-w64-${{matrix.env}}-gcc
-          mingw-w64-${{matrix.env}}-python-pip
-          mingw-w64-${{matrix.env}}-python-numpy
-          mingw-w64-${{matrix.env}}-cmake
-          mingw-w64-${{matrix.env}}-make
-          mingw-w64-${{matrix.env}}-python-pytest
-          mingw-w64-${{matrix.env}}-boost
-          mingw-w64-${{matrix.env}}-catch
-
-    - uses: msys2/setup-msys2@v2
-      if: matrix.sys == 'mingw64'
-      with:
-        msystem: ${{matrix.sys}}
-        install: >-
-          git
-          mingw-w64-${{matrix.env}}-python-scipy
-          mingw-w64-${{matrix.env}}-eigen3
-
-    - uses: actions/checkout@v4
-
-    - name: Configure C++11
-      # LTO leads to many undefined reference like
-      # `pybind11::detail::function_call::function_call(pybind11::detail::function_call&&)
-      run: >-
-        cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
-        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-        -S . -B build
-
-    - name: Build C++11
-      run: cmake --build build -j 2
-
-    - name: Python tests C++11
-      run: cmake --build build --target pytest -j 2
-
-    - name: C++11 tests
-      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build --target cpptest -j 2
-
-    - name: Interface test C++11
-      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build --target test_cmake_build
-
-    - name: Clean directory
-      run: git clean -fdx
-
-    - name: Configure C++14
-      run: >-
-        cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
-        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-        -S . -B build2
-
-    - name: Build C++14
-      run: cmake --build build2 -j 2
-
-    - name: Python tests C++14
-      run: cmake --build build2 --target pytest -j 2
-
-    - name: C++14 tests
-      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build2 --target cpptest -j 2
-
-    - name: Interface test C++14
-      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build2 --target test_cmake_build
-
-    - name: Clean directory
-      run: git clean -fdx
-
-    - name: Configure C++17
-      run: >-
-        cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
-        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
-        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-        -S . -B build3
-
-    - name: Build C++17
-      run: cmake --build build3 -j 2
-
-    - name: Python tests C++17
-      run: cmake --build build3 --target pytest -j 2
-
-    - name: C++17 tests
-      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build3 --target cpptest -j 2
-
-    - name: Interface test C++17
-      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build3 --target test_cmake_build
-
-  windows_clang:
-
-    strategy:
-      matrix:
-        os: [windows-latest]
-        python: ['3.10']
-
-    runs-on: "${{ matrix.os }}"
-
-    name: "🐍 ${{ matrix.python }} • ${{ matrix.os }} • clang-latest"
-
-    steps:
-      - name: Show env
-        run: env
-
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Set up Clang
-        uses: egor-tensin/setup-clang@v1
-
-      - name: Setup Python ${{ matrix.python }}
-        uses: actions/setup-python@v5
-        with:
-          python-version: ${{ matrix.python }}
-
-      - name: Update CMake
-        uses: jwlawson/actions-setup-cmake@v2.0
-
-      - name: Install ninja-build tool
-        uses: seanmiddleditch/gha-setup-ninja@v5
-
-      - name: Run pip installs
-        run: |
-          python -m pip install --upgrade pip
-          python -m pip install -r tests/requirements.txt
-
-      - name: Show Clang++ version
-        run: clang++ --version
-
-      - name: Show CMake version
-        run: cmake --version
-
-      # TODO: WERROR=ON
-      - name: Configure Clang
-        run: >
-          cmake -G Ninja -S . -B .
-          -DPYBIND11_WERROR=OFF
-          -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
-          -DDOWNLOAD_CATCH=ON
-          -DDOWNLOAD_EIGEN=ON
-          -DCMAKE_CXX_COMPILER=clang++
-          -DCMAKE_CXX_STANDARD=17
-          -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-
-      - name: Build
-        run: cmake --build . -j 2
-
-      - name: Python tests
-        run: cmake --build . --target pytest -j 2
-
-      - name: C++ tests
-        run: cmake --build . --target cpptest -j 2
-
-      - name: Interface test
-        run: cmake --build . --target test_cmake_build -j 2
-
-      - name: Clean directory
-        run: git clean -fdx
-
-  macos_brew_install_llvm:
-    name: "macos-13 • brew install llvm"
-    runs-on: macos-13
-
-    env:
-      # https://apple.stackexchange.com/questions/227026/how-to-install-recent-clang-with-homebrew
-      LDFLAGS: '-L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib'
-
-    steps:
-      - name: Update PATH
-        run: echo "/usr/local/opt/llvm/bin" >> $GITHUB_PATH
-
-      - name: Show env
-        run: env
-
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Show Clang++ version before brew install llvm
-        run: clang++ --version
-
-      - name: brew install llvm
-        run: brew install llvm
-
-      - name: Show Clang++ version after brew install llvm
-        run: clang++ --version
-
-      - name: Update CMake
-        uses: jwlawson/actions-setup-cmake@v2.0
-
-      - name: Run pip installs
-        run: |
-          python3 -m pip install --upgrade pip
-          python3 -m pip install -r tests/requirements.txt
-          python3 -m pip install numpy
-          python3 -m pip install scipy
-
-      - name: Show CMake version
-        run: cmake --version
-
-      - name: CMake Configure
-        run: >
-          cmake -S . -B .
-          -DPYBIND11_WERROR=ON
-          -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
-          -DDOWNLOAD_CATCH=ON
-          -DDOWNLOAD_EIGEN=ON
-          -DCMAKE_CXX_COMPILER=clang++
-          -DCMAKE_CXX_STANDARD=17
-          -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-          -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-
-      - name: Build
-        run: cmake --build . -j 2
-
-      - name: Python tests
-        run: cmake --build . --target pytest -j 2
-
-      - name: C++ tests
-        run: cmake --build . --target cpptest -j 2
-
-      - name: Interface test
-        run: cmake --build . --target test_cmake_build -j 2
-
-      - name: CMake Configure - Exercise cmake -DPYBIND11_TEST_OVERRIDE
-        run: >
-          cmake -S . -B build_partial
-          -DPYBIND11_WERROR=ON
-          -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
-          -DDOWNLOAD_CATCH=ON
-          -DDOWNLOAD_EIGEN=ON
-          -DCMAKE_CXX_COMPILER=clang++
-          -DCMAKE_CXX_STANDARD=17
-          -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-          -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-          "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
-
-      - name: Build - Exercise cmake -DPYBIND11_TEST_OVERRIDE
-        run: cmake --build build_partial -j 2
-
-      - name: Python tests - Exercise cmake -DPYBIND11_TEST_OVERRIDE
-        run: cmake --build build_partial --target pytest -j 2
-
-      - name: Clean directory
-        run: git clean -fdx
diff --git a/.github/workflows/ci_sh_def.yml.patch b/.github/workflows/ci_sh_def.yml.patch
deleted file mode 100644
index ecfd7639c..000000000
--- a/.github/workflows/ci_sh_def.yml.patch
+++ /dev/null
@@ -1,223 +0,0 @@
---- ci.yml	2024-07-30 11:20:28.997003056 -0700
-+++ ci_sh_def.yml	2024-07-30 11:21:39.724969167 -0700
-@@ -1,4 +1,16 @@
--name: CI
-+# PLEASE KEEP THIS GROUP OF FILES IN SYNC AT ALL TIMES:
-+#     ci.yml
-+#     ci_sh_def.yml
-+#     ci_sh_def.yml.patch
-+# To import changes made to ci.yml *** ESPECIALLY AFTER `git merge master` ***:
-+#     patch -i ci_sh_def.yml.patch -o ci_sh_def.yml
-+# To update the patch file after making changes to ci_sh.yml:
-+#     diff -u ci.yml ci_sh_def.yml > ci_sh_def.yml.patch
-+#     git commit -a -m 'Tracking ci.yml changes from master.'
-+#
-+# Thanks a lot to @rhaschke for PR #2930!
-+
-+name: "CI-SH-DEF"
- 
- on:
-   workflow_dispatch:
-@@ -13,7 +25,7 @@
- permissions: read-all
- 
- concurrency:
--  group: test-sh-avl${{ github.ref }}
-+  group: test-sh-def-${{ github.ref }}
-   cancel-in-progress: true
- 
- env:
-@@ -126,6 +138,7 @@
-         -DDOWNLOAD_CATCH=ON
-         -DDOWNLOAD_EIGEN=ON
-         -DCMAKE_CXX_STANDARD=11
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT ${{runner.os == 'Windows' && '/GR /EHsc' || ''}}"
-         ${{ matrix.args }}
- 
-     - name: Build C++11
-@@ -155,6 +168,7 @@
-         -DDOWNLOAD_CATCH=ON
-         -DDOWNLOAD_EIGEN=ON
-         -DCMAKE_CXX_STANDARD=17
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT ${{runner.os == 'Windows' && '/GR /EHsc' || ''}}"
-         ${{ matrix.args }}
- 
-     - name: Build
-@@ -174,6 +188,7 @@
-         -DDOWNLOAD_CATCH=ON
-         -DDOWNLOAD_EIGEN=ON
-         -DCMAKE_CXX_STANDARD=17
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT ${{runner.os == 'Windows' && '/GR /EHsc' || ''}}"
-         -DPYBIND11_INTERNALS_VERSION=10000000
-         ${{ matrix.args }}
- 
-@@ -217,6 +232,7 @@
-           -DDOWNLOAD_CATCH=ON
-           -DDOWNLOAD_EIGEN=ON
-           -DPython_ROOT_DIR=.venv
-+          -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
- 
-       - name: Build C++11
-         run: cmake --build build -j2
-@@ -290,6 +306,7 @@
-         -DDOWNLOAD_CATCH=ON
-         -DDOWNLOAD_EIGEN=ON
-         -DCMAKE_CXX_STANDARD=17
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
- 
-     - name: Build
-       run: cmake --build build -j 2
-@@ -357,6 +374,7 @@
-         -DPYBIND11_WERROR=ON
-         -DDOWNLOAD_CATCH=ON
-         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
- 
-     - name: Build
-@@ -386,7 +404,7 @@
-       run: apt-get update && DEBIAN_FRONTEND="noninteractive" apt-get install -y cmake git python3-dev python3-pytest python3-numpy
- 
-     - name: Configure
--      run: cmake -S . -B build -DPYBIND11_CUDA_TESTS=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
-+      run: cmake -S . -B build -DPYBIND11_CUDA_TESTS=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
- 
-     - name: Build
-       run: cmake --build build -j2 --verbose
-@@ -474,7 +492,7 @@
-         cmake -S . -B build -DDOWNLOAD_CATCH=ON \
-                             -DCMAKE_CXX_STANDARD=17 \
-                             -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") \
--                            -DCMAKE_CXX_FLAGS="-Wc,--pending_instantiations=0" \
-+                            -DCMAKE_CXX_FLAGS="-Wc,--pending_instantiations=0 -DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT" \
-                             -DPYBIND11_TEST_FILTER="test_smart_ptr.cpp"
- 
-     - name: Build
-@@ -526,6 +544,7 @@
-         -DPYBIND11_WERROR=ON
-         -DDOWNLOAD_CATCH=ON
-         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
- 
-     - name: Build
-@@ -548,6 +567,7 @@
-         -DPYBIND11_WERROR=ON
-         -DDOWNLOAD_CATCH=ON
-         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-         "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
- 
-@@ -597,6 +617,7 @@
-         -DDOWNLOAD_CATCH=ON     \
-         -DDOWNLOAD_EIGEN=OFF    \
-         -DCMAKE_CXX_STANDARD=11             \
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"  \
-         -DCMAKE_CXX_COMPILER=$(which icpc)  \
-         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
- 
-@@ -629,6 +650,7 @@
-         -DDOWNLOAD_CATCH=ON     \
-         -DDOWNLOAD_EIGEN=OFF    \
-         -DCMAKE_CXX_STANDARD=17             \
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"  \
-         -DCMAKE_CXX_COMPILER=$(which icpc)  \
-         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
- 
-@@ -700,6 +722,7 @@
-         -DDOWNLOAD_CATCH=ON
-         -DDOWNLOAD_EIGEN=ON
-         -DCMAKE_CXX_STANDARD=11
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
- 
-     - name: Build
-@@ -750,6 +773,7 @@
-         cmake ../pybind11-tests
-         -DDOWNLOAD_CATCH=ON
-         -DPYBIND11_WERROR=ON
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-       working-directory: /build-tests
- 
-@@ -850,6 +874,7 @@
-         -DPYBIND11_WERROR=ON
-         -DDOWNLOAD_CATCH=ON
-         -DDOWNLOAD_EIGEN=ON
-+        -DCMAKE_CXX_FLAGS="/GR /EHsc /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-         ${{ matrix.args }}
-     - name: Build C++11
-       run: cmake --build build -j 2
-@@ -904,6 +929,7 @@
-         -DPYBIND11_WERROR=ON
-         -DDOWNLOAD_CATCH=ON
-         -DDOWNLOAD_EIGEN=ON
-+        -DCMAKE_CXX_FLAGS="/GR /EHsc /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-         ${{ matrix.args }}
-     - name: Build C++11
-       run: cmake --build build --config Debug -j 2
-@@ -946,6 +972,7 @@
-         -DDOWNLOAD_CATCH=ON
-         -DDOWNLOAD_EIGEN=ON
-         -DCMAKE_CXX_STANDARD=20
-+        -DCMAKE_CXX_FLAGS="/GR /EHsc /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
- 
-     - name: Build C++20
-       run: cmake --build build -j 2
-@@ -966,6 +993,7 @@
-         -DDOWNLOAD_CATCH=ON
-         -DDOWNLOAD_EIGEN=ON
-         -DCMAKE_CXX_STANDARD=20
-+        -DCMAKE_CXX_FLAGS="/GR /EHsc /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-         "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
- 
-     - name: Build C++20 - Exercise cmake -DPYBIND11_TEST_OVERRIDE
-@@ -1018,6 +1046,7 @@
-       run: >-
-         cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
-         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-         -S . -B build
- 
-     - name: Build C++11
-@@ -1039,6 +1068,7 @@
-       run: >-
-         cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
-         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-         -S . -B build2
- 
-     - name: Build C++14
-@@ -1060,6 +1090,7 @@
-       run: >-
-         cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
-         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
-+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-         -S . -B build3
- 
-     - name: Build C++17
-@@ -1127,6 +1158,7 @@
-           -DDOWNLOAD_EIGEN=ON
-           -DCMAKE_CXX_COMPILER=clang++
-           -DCMAKE_CXX_STANDARD=17
-+          -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
- 
-       - name: Build
-         run: cmake --build . -j 2
-@@ -1192,6 +1224,7 @@
-           -DDOWNLOAD_EIGEN=ON
-           -DCMAKE_CXX_COMPILER=clang++
-           -DCMAKE_CXX_STANDARD=17
-+          -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-           -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
- 
-       - name: Build
-@@ -1215,6 +1248,7 @@
-           -DDOWNLOAD_EIGEN=ON
-           -DCMAKE_CXX_COMPILER=clang++
-           -DCMAKE_CXX_STANDARD=17
-+          -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
-           -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
-           "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
- 
diff --git a/.github/workflows/emscripten.yaml b/.github/workflows/emscripten.yaml
index 14b2b9dc7..fe4cd821c 100644
--- a/.github/workflows/emscripten.yaml
+++ b/.github/workflows/emscripten.yaml
@@ -6,6 +6,7 @@ on:
     branches:
     - master
     - stable
+    - smart_holder
     - v*
 
 concurrency: