diff --git a/.github/workflows/ci_sh_def.yml b/.github/workflows/ci_sh_def.yml
index 11d24fcf7..92b43b663 100644
--- a/.github/workflows/ci_sh_def.yml
+++ b/.github/workflows/ci_sh_def.yml
@@ -45,7 +45,7 @@ jobs:
       matrix:
         runs-on: [ubuntu-20.04, windows-2022, macos-13]
         python:
-        - '3.6'
+        - '3.8'
         - '3.9'
         - '3.12'
         - '3.13'
@@ -61,16 +61,17 @@ jobs:
         include:
           # Just add a key
           - runs-on: ubuntu-20.04
-            python: '3.6'
+            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: '3.6'
+            python: '3.8'
             args: >
               -DPYBIND11_FINDPYTHON=ON
           # Inject a couple Windows 2019 runs
@@ -95,7 +96,7 @@ jobs:
 
     - name: Setup Boost (Linux)
       # Can't use boost + define _
-      if: runner.os == 'Linux' && matrix.python != '3.6'
+      if: runner.os == 'Linux' && matrix.exercise_D_ != 1
       run: sudo apt-get install libboost-dev
 
     - name: Setup Boost (macOS)
@@ -147,9 +148,7 @@ jobs:
       run: cmake --build . --target pytest -j 2
 
     - name: C++11 tests
-      # TODO: Figure out how to load the DLL on Python 3.8+
-      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10' || matrix.python == '3.11' || matrix.python == 'pypy-3.8'))"
-      run: cmake --build .  --target cpptest -j 2
+      run: cmake --build . --target cpptest -j 2
 
     - name: Interface test C++11
       run: cmake --build . --target test_cmake_build
@@ -179,8 +178,6 @@ jobs:
       run: cmake --build build2 --target pytest
 
     - name: C++ tests
-      # TODO: Figure out how to load the DLL on Python 3.8+
-      if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10' || matrix.python == '3.11' || matrix.python == 'pypy-3.8'))"
       run: cmake --build build2 --target cpptest
 
     # Third build - C++17 mode with unstable ABI
@@ -682,15 +679,13 @@ jobs:
         cmake --build build-17 --target test_cmake_build
 
 
-  # Testing on CentOS (manylinux uses a centos base, and this is an easy way
-  # to get GCC 4.8, which is the manylinux1 compiler).
+  # Testing on CentOS (manylinux uses a centos base).
   centos:
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
         container:
-          - "centos:7"  # GCC 4.8
           - "almalinux:8"
           - "almalinux:9"
 
@@ -700,18 +695,13 @@ jobs:
     steps:
     - name: Latest actions/checkout
       uses: actions/checkout@v4
-      if: matrix.container != 'centos:7'
 
-    - name: Pin actions/checkout as required for centos:7
-      uses: actions/checkout@v3
-      if: matrix.container == 'centos:7'
+    - 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 (RHEL 7)
-      if: matrix.container == 'centos:7'
-      run: yum update -y && yum install -y python3-devel gcc-c++ make git
-
-    - name: Add Python 3 (RHEL 8+)
-      if: matrix.container != 'centos:7'
+    - 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
@@ -836,17 +826,25 @@ jobs:
       fail-fast: false
       matrix:
         python:
-        - 3.6
-        - 3.7
-        - 3.8
-        - 3.9
+        - '3.7'
+        - '3.8'
+        - '3.9'
+        - '3.10'
+        - '3.11'
+        - '3.12'
 
         include:
-          - python: 3.9
+          - python: '3.12'
             args: -DCMAKE_CXX_STANDARD=20
-          - python: 3.8
+          - 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
-          - python: 3.7
+          - python: '3.7'
             args: -DCMAKE_CXX_STANDARD=14
 
 
diff --git a/.github/workflows/ci_sh_def.yml.patch b/.github/workflows/ci_sh_def.yml.patch
index 262e4f75f..439763ece 100644
--- a/.github/workflows/ci_sh_def.yml.patch
+++ b/.github/workflows/ci_sh_def.yml.patch
@@ -1,5 +1,5 @@
---- ci.yml	2024-06-19 10:06:18.454361731 -0700
-+++ ci_sh_def.yml	2024-06-19 10:07:59.514269934 -0700
+--- ci.yml	2024-06-21 22:56:01.205982412 -0700
++++ ci_sh_def.yml	2024-06-21 22:57:45.189902320 -0700
 @@ -1,4 +1,16 @@
 -name: CI
 +# PLEASE KEEP THIS GROUP OF FILES IN SYNC AT ALL TIMES:
@@ -27,7 +27,7 @@
    cancel-in-progress: true
  
  env:
-@@ -125,6 +137,7 @@
+@@ -126,6 +138,7 @@
          -DDOWNLOAD_CATCH=ON
          -DDOWNLOAD_EIGEN=ON
          -DCMAKE_CXX_STANDARD=11
@@ -35,7 +35,7 @@
          ${{ matrix.args }}
  
      - name: Build C++11
-@@ -156,6 +169,7 @@
+@@ -155,6 +168,7 @@
          -DDOWNLOAD_CATCH=ON
          -DDOWNLOAD_EIGEN=ON
          -DCMAKE_CXX_STANDARD=17
@@ -43,7 +43,7 @@
          ${{ matrix.args }}
  
      - name: Build
-@@ -177,6 +191,7 @@
+@@ -174,6 +188,7 @@
          -DDOWNLOAD_CATCH=ON
          -DDOWNLOAD_EIGEN=ON
          -DCMAKE_CXX_STANDARD=17
@@ -51,7 +51,7 @@
          -DPYBIND11_INTERNALS_VERSION=10000000
          ${{ matrix.args }}
  
-@@ -220,6 +235,7 @@
+@@ -217,6 +232,7 @@
            -DDOWNLOAD_CATCH=ON
            -DDOWNLOAD_EIGEN=ON
            -DPython_ROOT_DIR=.venv
@@ -59,7 +59,7 @@
  
        - name: Build C++11
          run: cmake --build build -j2
-@@ -293,6 +309,7 @@
+@@ -290,6 +306,7 @@
          -DDOWNLOAD_CATCH=ON
          -DDOWNLOAD_EIGEN=ON
          -DCMAKE_CXX_STANDARD=17
@@ -67,7 +67,7 @@
  
      - name: Build
        run: cmake --build build -j 2
-@@ -361,6 +378,7 @@
+@@ -358,6 +375,7 @@
          -DPYBIND11_WERROR=ON
          -DDOWNLOAD_CATCH=ON
          -DCMAKE_CXX_STANDARD=${{ matrix.std }}
@@ -75,7 +75,7 @@
          -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
  
      - name: Build
-@@ -390,7 +408,7 @@
+@@ -387,7 +405,7 @@
        run: apt-get update && DEBIAN_FRONTEND="noninteractive" apt-get install -y cmake git python3-dev python3-pytest python3-numpy
  
      - name: Configure
@@ -84,7 +84,7 @@
  
      - name: Build
        run: cmake --build build -j2 --verbose
-@@ -478,7 +496,7 @@
+@@ -475,7 +493,7 @@
          cmake -S . -B build -DDOWNLOAD_CATCH=ON \
                              -DCMAKE_CXX_STANDARD=17 \
                              -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") \
@@ -93,7 +93,7 @@
                              -DPYBIND11_TEST_FILTER="test_smart_ptr.cpp"
  
      - name: Build
-@@ -532,6 +550,7 @@
+@@ -529,6 +547,7 @@
          -DPYBIND11_WERROR=ON
          -DDOWNLOAD_CATCH=ON
          -DCMAKE_CXX_STANDARD=${{ matrix.std }}
@@ -101,7 +101,7 @@
          -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
  
      - name: Build
-@@ -554,6 +573,7 @@
+@@ -551,6 +570,7 @@
          -DPYBIND11_WERROR=ON
          -DDOWNLOAD_CATCH=ON
          -DCMAKE_CXX_STANDARD=${{ matrix.std }}
@@ -109,7 +109,7 @@
          -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
          "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
  
-@@ -603,6 +623,7 @@
+@@ -600,6 +620,7 @@
          -DDOWNLOAD_CATCH=ON     \
          -DDOWNLOAD_EIGEN=OFF    \
          -DCMAKE_CXX_STANDARD=11             \
@@ -117,7 +117,7 @@
          -DCMAKE_CXX_COMPILER=$(which icpc)  \
          -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
  
-@@ -635,6 +656,7 @@
+@@ -632,6 +653,7 @@
          -DDOWNLOAD_CATCH=ON     \
          -DDOWNLOAD_EIGEN=OFF    \
          -DCMAKE_CXX_STANDARD=17             \
@@ -125,7 +125,7 @@
          -DCMAKE_CXX_COMPILER=$(which icpc)  \
          -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
  
-@@ -713,6 +735,7 @@
+@@ -703,6 +725,7 @@
          -DDOWNLOAD_CATCH=ON
          -DDOWNLOAD_EIGEN=ON
          -DCMAKE_CXX_STANDARD=11
@@ -133,7 +133,7 @@
          -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
  
      - name: Build
-@@ -763,6 +786,7 @@
+@@ -753,6 +776,7 @@
          cmake ../pybind11-tests
          -DDOWNLOAD_CATCH=ON
          -DPYBIND11_WERROR=ON
@@ -141,7 +141,7 @@
          -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
        working-directory: /build-tests
  
-@@ -858,6 +882,7 @@
+@@ -856,6 +880,7 @@
          -DPYBIND11_WERROR=ON
          -DDOWNLOAD_CATCH=ON
          -DDOWNLOAD_EIGEN=ON
@@ -149,7 +149,7 @@
          ${{ matrix.args }}
      - name: Build C++11
        run: cmake --build build -j 2
-@@ -912,6 +937,7 @@
+@@ -910,6 +935,7 @@
          -DPYBIND11_WERROR=ON
          -DDOWNLOAD_CATCH=ON
          -DDOWNLOAD_EIGEN=ON
@@ -157,7 +157,7 @@
          ${{ matrix.args }}
      - name: Build C++11
        run: cmake --build build --config Debug -j 2
-@@ -954,6 +980,7 @@
+@@ -952,6 +978,7 @@
          -DDOWNLOAD_CATCH=ON
          -DDOWNLOAD_EIGEN=ON
          -DCMAKE_CXX_STANDARD=20
@@ -165,7 +165,7 @@
  
      - name: Build C++20
        run: cmake --build build -j 2
-@@ -974,6 +1001,7 @@
+@@ -972,6 +999,7 @@
          -DDOWNLOAD_CATCH=ON
          -DDOWNLOAD_EIGEN=ON
          -DCMAKE_CXX_STANDARD=20
@@ -173,7 +173,7 @@
          "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
  
      - name: Build C++20 - Exercise cmake -DPYBIND11_TEST_OVERRIDE
-@@ -1026,6 +1054,7 @@
+@@ -1024,6 +1052,7 @@
        run: >-
          cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
          -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
@@ -181,7 +181,7 @@
          -S . -B build
  
      - name: Build C++11
-@@ -1047,6 +1076,7 @@
+@@ -1045,6 +1074,7 @@
        run: >-
          cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
          -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
@@ -189,7 +189,7 @@
          -S . -B build2
  
      - name: Build C++14
-@@ -1068,6 +1098,7 @@
+@@ -1066,6 +1096,7 @@
        run: >-
          cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
          -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
@@ -197,7 +197,7 @@
          -S . -B build3
  
      - name: Build C++17
-@@ -1135,6 +1166,7 @@
+@@ -1133,6 +1164,7 @@
            -DDOWNLOAD_EIGEN=ON
            -DCMAKE_CXX_COMPILER=clang++
            -DCMAKE_CXX_STANDARD=17
@@ -205,7 +205,7 @@
  
        - name: Build
          run: cmake --build . -j 2
-@@ -1200,6 +1232,7 @@
+@@ -1198,6 +1230,7 @@
            -DDOWNLOAD_EIGEN=ON
            -DCMAKE_CXX_COMPILER=clang++
            -DCMAKE_CXX_STANDARD=17
@@ -213,7 +213,7 @@
            -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
  
        - name: Build
-@@ -1223,6 +1256,7 @@
+@@ -1221,6 +1254,7 @@
            -DDOWNLOAD_EIGEN=ON
            -DCMAKE_CXX_COMPILER=clang++
            -DCMAKE_CXX_STANDARD=17