diff --git a/.github/workflows/aarch64_toolchain.yml b/.github/workflows/aarch64_toolchain.yml
index ba441f646c..2dcd2f7078 100644
--- a/.github/workflows/aarch64_toolchain.yml
+++ b/.github/workflows/aarch64_toolchain.yml
@@ -1,7 +1,7 @@
 # ref: https://toolchains.bootlin.com/
 name: aarch64 Toolchain
 
-on: [push, pull_request, workflow_dispatch]
+on: [workflow_dispatch]
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
diff --git a/.github/workflows/amd64_cmake_glop_cpp.yml b/.github/workflows/amd64_cmake_glop_cpp.yml
index bf214fecf9..46fc59ec2e 100644
--- a/.github/workflows/amd64_cmake_glop_cpp.yml
+++ b/.github/workflows/amd64_cmake_glop_cpp.yml
@@ -1,7 +1,12 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 CMake Glop C++
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
diff --git a/.github/workflows/amd64_docker_bazel.yml b/.github/workflows/amd64_docker_bazel.yml
index 01cfd8666e..41bb700f27 100644
--- a/.github/workflows/amd64_docker_bazel.yml
+++ b/.github/workflows/amd64_docker_bazel.yml
@@ -1,7 +1,12 @@
 # ref: https://github.com/docker-library/official-images
 name: amd64 Docker Bazel
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
diff --git a/.github/workflows/amd64_docker_cmake.yml b/.github/workflows/amd64_docker_cmake.yml
index e514158d0c..573c8b8867 100644
--- a/.github/workflows/amd64_docker_cmake.yml
+++ b/.github/workflows/amd64_docker_cmake.yml
@@ -1,7 +1,12 @@
 # ref: https://github.com/docker-library/official-images
 name: amd64 Docker CMake
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
diff --git a/.github/workflows/amd64_freebsd_cmake.yml b/.github/workflows/amd64_freebsd_cmake.yml
index 7c7579928b..679eb4fab0 100644
--- a/.github/workflows/amd64_freebsd_cmake.yml
+++ b/.github/workflows/amd64_freebsd_cmake.yml
@@ -1,7 +1,7 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 FreeBSD CMake
 
-on: [push, pull_request, workflow_dispatch]
+on: [workflow_dispatch]
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
diff --git a/.github/workflows/amd64_linux_bazel.yml b/.github/workflows/amd64_linux_bazel.yml
index 1000515ea0..cef3600e54 100644
--- a/.github/workflows/amd64_linux_bazel.yml
+++ b/.github/workflows/amd64_linux_bazel.yml
@@ -1,15 +1,23 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Linux Bazel
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
+env:
+  cache-root: /tmp/bazel
+
 # Building using the github runner environement directly.
 jobs:
-  native:
+  amd64-Linux-Bazel-Python:
     strategy:
       matrix:
         python: [
@@ -19,11 +27,11 @@ jobs:
           #{version: '3.13'},
         ]
       fail-fast: false
-    name: amd64•Linux•Bazel•Python-${{matrix.python.version}}
-    runs-on: ubuntu-latest
     env:
       CC:  gcc-12
       CXX: g++-12
+      cache-name: ${{github.job}}-${{matrix.python.version}}
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
       - name: Check Java
@@ -31,7 +39,7 @@ jobs:
       - name: Check mvn
         run: mvn --version
       - name: Setup Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{matrix.python.version}}
       - name: Check Python
@@ -53,21 +61,26 @@ jobs:
         run: |
           sed -i -e 's/\(DEFAULT_PYTHON =\) "3.[0-9]\+"/\1 "${{matrix.python.version}}"/g' MODULE.bazel
           cat MODULE.bazel
+      - name: Restore bazel cache
+        uses: actions/cache/restore@v4
+        id: bazel-cache-restore
+        with:
+          key: ${{env.cache-name}}
+          path: ${{env.cache-root}}
       - name: Build
-        run: >
-          bazel build
-          -c opt
-          --subcommands=pretty_print
-          //ortools/... //examples/...
+        run: bazel --output_user_root=${{env.cache-root}} build --config=ci //ortools/... //examples/...
       - name: Test
-        run: >
-          bazel test
-          -c opt
-          --test_output=errors
-          //ortools/... //examples/...
+        run: bazel --output_user_root=${{env.cache-root}} test --config=ci //ortools/... //examples/...
+      - name: Save Bazel cache for branch main even when Build and Test fail.
+        uses: actions/cache/save@v4
+        # https://docs.github.com/en/actions/reference/workflows-and-actions/dependency-caching#restrictions-for-accessing-a-cache
+        if: always() && github.ref == 'refs/heads/main'
+        with:
+          key: ${{env.cache-name}}-${{github.sha}}
+          path: ${{env.cache-root}}
 
   amd64_linux_bazel:
     runs-on: ubuntu-latest
-    needs: native
+    needs: amd64-Linux-Bazel-Python
     steps:
       - uses: actions/checkout@v5
diff --git a/.github/workflows/amd64_linux_cmake_coinor_off.yml b/.github/workflows/amd64_linux_cmake_coinor_off.yml
index c9d3f1e5e5..ab00314f41 100644
--- a/.github/workflows/amd64_linux_cmake_coinor_off.yml
+++ b/.github/workflows/amd64_linux_cmake_coinor_off.yml
@@ -1,75 +1,135 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Linux CMake CoinOR OFF
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
-    strategy:
-      matrix:
-        cmake: [
-          {language: 'C++', args: '-DBUILD_CXX=ON'},
-          {language: '.Net', args: '-DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF -DBUILD_DOTNET=ON'},
-          {language: 'Java', args: '-DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF -DBUILD_JAVA=ON'},
-          {language: 'Python', args: '-DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF -DBUILD_PYTHON=ON'},
-        ]
-      fail-fast: false
-    name: amd64•Linux•CMake•${{matrix.cmake.language}}•CoinOR=OFF
+    name: amd64•Linux•CMake•CoinOR=OFF
     runs-on: ubuntu-latest
+    env:
+      deps_src_key: amd64_linux_coinor_deps_src
+      deps_build_key: amd64_linux_coinor_deps_build
+      ccache_key: amd64_linux_coinor_ccache
     steps:
-    - uses: actions/checkout@v5
-      # Install SWIG
-    - name: Swig install
-      run: sudo apt install -y swig
-    - name: Check swig
-      run: swig -version
-      # Install .NET SDKs
-    - name: Setup .NET 8.0
-      uses: actions/setup-dotnet@v4
-      with:
-        dotnet-version: 8.0.x
-    - name: Check dotnet
-      run: dotnet --info
-      # Install Java
-    - name: Check java
-      run: java -version
-      # Install Python
-    - name: Install python3 venv
-      run: sudo apt-get install python3-venv
-    - name: Update Path
-      run: echo "$HOME/.local/bin" >> $GITHUB_PATH
-      # CMake
-    - name: Check cmake
-      run: cmake --version
-    - name: Configure
-      run: >
-        cmake -S. -Bbuild
-        -DCMAKE_BUILD_TYPE=Release
-        -DBUILD_DEPS=ON
-        -DUSE_COINOR=OFF
-        ${{matrix.cmake.args}}
-    - name: Build
-      run: >
-        cmake --build build
-        --config Release
-        --target all
-        -v -j2
-    - name: Test
-      run: >
-        CTEST_OUTPUT_ON_FAILURE=1
-        cmake --build build
-        --config Release
-        --target test
-        -v
-    - name: Install
-      run: >
-        cmake --build build
-        --config Release
-        --target install
-        -v
-        -- DESTDIR=install
+      - uses: actions/checkout@v5
+      - name: Install Dependencies
+        run: |
+          sudo apt update
+          sudo apt install -y ninja-build ccache swig
+          swig -version
+        # Install .NET SDKs
+      - name: Setup .NET 8.0
+        uses: actions/setup-dotnet@v5
+        with:
+          dotnet-version: 8.0.x
+      - name: Check dotnet
+        run: dotnet --info
+        # Install Java
+      - name: Check java
+        run: java -version
+        # Install Python
+      - name: Install python3 venv
+        run: sudo apt-get install python3-venv
+      - name: Update Path
+        run: echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
+      - name: Check CMake
+        run: cmake --version
+      - name: Configure
+        run: >
+          cmake -S. -Bbuild
+          -G "Ninja"
+          -DCMAKE_BUILD_TYPE=Release
+          -DBUILD_DOTNET=ON -DBUILD_JAVA=ON -DBUILD_PYTHON=ON
+          -DUSE_GLPK=OFF -DUSE_SCIP=OFF
+          -DUSE_COINOR=OFF
+          -DCMAKE_INSTALL_PREFIX=install
+      - name: Build
+        run: >
+          cmake --build build
+          --config Release
+          --target all
+          -v -j2
+      - name: Test
+        run: >
+          CTEST_OUTPUT_ON_FAILURE=1
+          cmake --build build
+          --config Release
+          --target test
+          -v
+      - name: Install
+        run: >
+          cmake --build build
+          --config Release
+          --target install
+          -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
+
+  amd64_linux_cmake_coinor:
+    runs-on: ubuntu-latest
+    needs: native
+    steps:
+      - uses: actions/checkout@v5
diff --git a/.github/workflows/amd64_linux_cmake_cpp.yml b/.github/workflows/amd64_linux_cmake_cpp.yml
index ff4a10af3a..6c84859dad 100644
--- a/.github/workflows/amd64_linux_cmake_cpp.yml
+++ b/.github/workflows/amd64_linux_cmake_cpp.yml
@@ -1,13 +1,22 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Linux CMake C++
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     strategy:
@@ -15,17 +24,45 @@ jobs:
         cmake: [
           {name: "Make", generator: "Unix Makefiles", config: Release},
           {name: "Ninja", generator: "Ninja", config: Release},
-          {name: "Ninja Multi", generator: "Ninja Multi-Config", config: Release},
-        ]
+          {name: "NinjaMulti", generator: "Ninja Multi-Config", config: Release}
+         ]
       fail-fast: false
     name: amd64•Linux•CMake(${{matrix.cmake.name}})•C++
     runs-on: ubuntu-latest
+    env:
+      deps_src_key: amd64_linux_cpp_deps_src
+      deps_build_key: amd64_linux_cpp_deps_build_${{matrix.cmake.name}}
+      ccache_key: amd64_linux_cpp_ccache_${{matrix.cmake.name}}
     steps:
       - uses: actions/checkout@v5
-      - name: Install Ninja
+      - name: Install Dependencies
         run: |
-          sudo apt-get update
-          sudo apt-get install ninja-build
+          sudo apt update
+          sudo apt install -y ninja-build ccache
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
@@ -54,6 +91,32 @@ jobs:
           --config ${{matrix.cmake.config}}
           --target install
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   amd64_linux_cmake_cpp:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/amd64_linux_cmake_dotnet.yml b/.github/workflows/amd64_linux_cmake_dotnet.yml
index 176d21297c..90860faa69 100644
--- a/.github/workflows/amd64_linux_cmake_dotnet.yml
+++ b/.github/workflows/amd64_linux_cmake_dotnet.yml
@@ -1,34 +1,73 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Linux CMake .Net
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     name: amd64•Linux•CMake•.Net
     runs-on: ubuntu-latest
+    env:
+      deps_src_key: amd64_linux_dotnet_deps_src
+      deps_build_key: amd64_linux_dotnet_deps_build
+      ccache_key: amd64_linux_dotnet_ccache
     steps:
       - uses: actions/checkout@v5
-      - name: Swig install
+      - name: Install Dependencies
         run: |
-          sudo apt install -y swig
+          sudo apt update
+          sudo apt install -y ninja-build ccache swig
           swig -version
       - name: Setup .NET 8.0
-        uses: actions/setup-dotnet@v4
+        uses: actions/setup-dotnet@v5
         with:
           dotnet-version: 8.0.x
       - name: Check dotnet
         run: dotnet --info
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
         run: >
           cmake -S. -Bbuild
+          -G "Ninja"
           -DCMAKE_BUILD_TYPE=Release
           -DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF
           -DBUILD_DOTNET=ON
@@ -52,6 +91,32 @@ jobs:
           --config Release
           --target install
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   amd64_linux_cmake_dotnet:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/amd64_linux_cmake_glpk_on.yml b/.github/workflows/amd64_linux_cmake_glpk_on.yml
index c5062902e1..43519f09bb 100644
--- a/.github/workflows/amd64_linux_cmake_glpk_on.yml
+++ b/.github/workflows/amd64_linux_cmake_glpk_on.yml
@@ -1,28 +1,87 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Linux CMake GLPK ON
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     name: amd64•Linux•CMake•GLPK=ON
     runs-on: ubuntu-latest
+    env:
+      deps_src_key: amd64_linux_glpk_deps_src
+      deps_build_key: amd64_linux_glpk_deps_build
+      ccache_key: amd64_linux_glpk_ccache
     steps:
       - uses: actions/checkout@v5
-      - name: Check cmake
+      - name: Install Dependencies
+        run: |
+          sudo apt update
+          sudo apt install -y ninja-build ccache swig
+          swig -version
+        # Install .NET SDKs
+      - name: Setup .NET 8.0
+        uses: actions/setup-dotnet@v5
+        with:
+          dotnet-version: 8.0.x
+      - name: Check dotnet
+        run: dotnet --info
+        # Install Java
+      - name: Check java
+        run: java -version
+        # Install Python
+      - name: Install python3 venv
+        run: sudo apt-get install python3-venv
+      - name: Update Path
+        run: echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
+      - name: Check CMake
         run: cmake --version
       - name: Configure
         run: >
           cmake -S. -Bbuild
+          -G "Ninja"
           -DCMAKE_BUILD_TYPE=Release
-          -DBUILD_DEPS=ON
+          -DBUILD_DOTNET=ON -DBUILD_JAVA=ON -DBUILD_PYTHON=ON
           -DUSE_SCIP=OFF -DUSE_COINOR=OFF
           -DUSE_GLPK=ON
+          -DCMAKE_INSTALL_PREFIX=install
       - name: Build
         run: >
           cmake --build build
@@ -42,4 +101,35 @@ jobs:
           --config Release
           --target install
           -v
-          -- DESTDIR=install
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
+
+  amd64_linux_cmake_glpk:
+    runs-on: ubuntu-latest
+    needs: native
+    steps:
+      - uses: actions/checkout@v5
diff --git a/.github/workflows/amd64_linux_cmake_java.yml b/.github/workflows/amd64_linux_cmake_java.yml
index 2dd5bcec0b..1e6756c7e0 100644
--- a/.github/workflows/amd64_linux_cmake_java.yml
+++ b/.github/workflows/amd64_linux_cmake_java.yml
@@ -1,30 +1,69 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Linux CMake Java
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     name: amd64•Linux•CMake•Java
     runs-on: ubuntu-latest
+    env:
+      deps_src_key: amd64_linux_java_deps_src
+      deps_build_key: amd64_linux_java_deps_build
+      ccache_key: amd64_linux_java_ccache
     steps:
       - uses: actions/checkout@v5
-      - name: Swig install
+      - name: Install Dependencies
         run: |
-          sudo apt install -y swig
+          sudo apt update
+          sudo apt install -y ninja-build ccache swig
           swig -version
       - name: Check java
         run: java -version
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
         run: >
           cmake -S. -Bbuild
+          -G "Ninja"
           -DCMAKE_BUILD_TYPE=Release
           -DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF
           -DBUILD_JAVA=ON -DSKIP_GPG=ON
@@ -48,6 +87,32 @@ jobs:
           --config Release
           --target install
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   amd64_linux_cmake_java:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/amd64_linux_cmake_python.yml b/.github/workflows/amd64_linux_cmake_python.yml
index 0aa7174fb3..0879a5f938 100644
--- a/.github/workflows/amd64_linux_cmake_python.yml
+++ b/.github/workflows/amd64_linux_cmake_python.yml
@@ -1,77 +1,132 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Linux CMake Python
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     strategy:
       matrix:
-        cmake: [
-          {name: "Make", generator: "Unix Makefiles", config: Release},
-          {name: "Ninja", generator: "Ninja", config: Release},
-          {name: "Ninja Multi", generator: "Ninja Multi-Config", config: Release},
-        ]
         python: [
           {version: "3.9"},
-          {version: "3.10"},
-          {version: "3.11"},
-          {version: "3.12"},
+          #{version: "3.10"},
+          #{version: "3.11"},
+          #{version: "3.12"},
           {version: "3.13"},
-        ]
+         ]
       fail-fast: false
-    name: amd64•Linux•CMake(${{matrix.cmake.name}})•Python-${{matrix.python.version}}
+    name: amd64•Linux•CMake•Python${{matrix.python.version}}
     runs-on: ubuntu-latest
+    env:
+      deps_src_key: amd64_linux_python_deps_src_${{matrix.python.version}}
+      deps_build_key: amd64_linux_python_deps_build_${{matrix.python.version}}
+      ccache_key: amd64_linux_python_ccache_${{matrix.python.version}}
     steps:
       - uses: actions/checkout@v5
-      - name: Install Ninja
+      - name: Install Dependencies
         run: |
           sudo apt update
-          sudo apt install -y ninja-build
-      - name: Swig install
-        run: |
-          sudo apt install -y swig
+          sudo apt install -y ninja-build ccache swig
           swig -version
       - name: Setup Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{matrix.python.version}}
       - name: Update Path
         run: echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
         run: >
           cmake -S. -Bbuild
-          -G "${{matrix.cmake.generator}}"
-          -DCMAKE_BUILD_TYPE=${{matrix.cmake.config}}
+          -G "Ninja"
+          -DCMAKE_BUILD_TYPE=Release
           -DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF
           -DBUILD_PYTHON=ON
           -DCMAKE_INSTALL_PREFIX=install
       - name: Build
         run: >
           cmake --build build
-          --config ${{matrix.cmake.config}}
+          --config Release
           --target all
           -v -j2
       - name: Test
         run: >
           CTEST_OUTPUT_ON_FAILURE=1
           cmake --build build
-          --config ${{matrix.cmake.config}}
+          --config Release
           --target test
           -v
       - name: Install
         run: >
           cmake --build build
-          --config ${{matrix.cmake.config}}
+          --config Release
           --target install
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   amd64_linux_cmake_python:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/amd64_linux_cmake_scip_off.yml b/.github/workflows/amd64_linux_cmake_scip_off.yml
index 71a3e1693b..2b9f960c6a 100644
--- a/.github/workflows/amd64_linux_cmake_scip_off.yml
+++ b/.github/workflows/amd64_linux_cmake_scip_off.yml
@@ -1,75 +1,135 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Linux CMake SCIP OFF
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
-    strategy:
-      matrix:
-        cmake: [
-          {language: 'C++', args: '-DBUILD_CXX=ON'},
-          {language: '.Net', args: '-DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF -DBUILD_DOTNET=ON'},
-          {language: 'Java', args: '-DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF -DBUILD_JAVA=ON'},
-          {language: 'Python', args: '-DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF -DBUILD_PYTHON=ON'},
-        ]
-      fail-fast: false
-    name: amd64•Linux•CMake•${{matrix.cmake.language}}•SCIP=OFF
+    name: amd64•Linux•CMake•SCIP=OFF
     runs-on: ubuntu-latest
+    env:
+      deps_src_key: amd64_linux_scip_deps_src
+      deps_build_key: amd64_linux_scip_deps_build
+      ccache_key: amd64_linux_scip_ccache
     steps:
-    - uses: actions/checkout@v5
-      # Install SWIG
-    - name: Swig install
-      run: sudo apt install -y swig
-    - name: Check swig
-      run: swig -version
-      # Install .NET SDKs
-    - name: Setup .NET 8.0
-      uses: actions/setup-dotnet@v4
-      with:
-        dotnet-version: 8.0.x
-    - name: Check dotnet
-      run: dotnet --info
-      # Install Java
-    - name: Check java
-      run: java -version
-      # Install Python
-    - name: Install python3 venv
-      run: sudo apt-get install python3-venv
-    - name: Update Path
-      run: echo "$HOME/.local/bin" >> $GITHUB_PATH
-      # CMake
-    - name: Check cmake
-      run: cmake --version
-    - name: Configure
-      run: >
-        cmake -S. -Bbuild
-        -DCMAKE_BUILD_TYPE=Release
-        -DBUILD_DEPS=ON
-        -DUSE_SCIP=OFF
-        ${{matrix.cmake.args}}
-    - name: Build
-      run: >
-        cmake --build build
-        --config Release
-        --target all
-        -v -j2
-    - name: Test
-      run: >
-        CTEST_OUTPUT_ON_FAILURE=1
-        cmake --build build
-        --config Release
-        --target test
-        -v
-    - name: Install
-      run: >
-        cmake --build build
-        --config Release
-        --target install
-        -v
-        -- DESTDIR=install
+      - uses: actions/checkout@v5
+      - name: Install Dependencies
+        run: |
+          sudo apt update
+          sudo apt install -y ninja-build ccache swig
+          swig -version
+        # Install .NET SDKs
+      - name: Setup .NET 8.0
+        uses: actions/setup-dotnet@v5
+        with:
+          dotnet-version: 8.0.x
+      - name: Check dotnet
+        run: dotnet --info
+        # Install Java
+      - name: Check java
+        run: java -version
+        # Install Python
+      - name: Install python3 venv
+        run: sudo apt-get install python3-venv
+      - name: Update Path
+        run: echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
+      - name: Check CMake
+        run: cmake --version
+      - name: Configure
+        run: >
+          cmake -S. -Bbuild
+          -G "Ninja"
+          -DCMAKE_BUILD_TYPE=Release
+          -DBUILD_DOTNET=ON -DBUILD_JAVA=ON -DBUILD_PYTHON=ON
+          -DUSE_COINOR=OFF -DUSE_GLPK=OFF
+          -DUSE_SCIP=OFF
+          -DCMAKE_INSTALL_PREFIX=install
+      - name: Build
+        run: >
+          cmake --build build
+          --config Release
+          --target all
+          -v -j2
+      - name: Test
+        run: >
+          CTEST_OUTPUT_ON_FAILURE=1
+          cmake --build build
+          --config Release
+          --target test
+          -v
+      - name: Install
+        run: >
+          cmake --build build
+          --config Release
+          --target install
+          -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
+
+  amd64_linux_cmake_scip:
+    runs-on: ubuntu-latest
+    needs: native
+    steps:
+      - uses: actions/checkout@v5
diff --git a/.github/workflows/amd64_linux_cmake_system_deps.yml b/.github/workflows/amd64_linux_cmake_system_deps.yml
index e3d0c2a378..40536e3f8c 100644
--- a/.github/workflows/amd64_linux_cmake_system_deps.yml
+++ b/.github/workflows/amd64_linux_cmake_system_deps.yml
@@ -1,14 +1,19 @@
 # Test or-tools using system wide install dependencies.
 name: amd64 Linux CMake System Dependencies
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 jobs:
-  native:
+  docker:
     strategy:
       matrix:
         distro: [system_deps]
diff --git a/.github/workflows/amd64_macos_bazel.yml b/.github/workflows/amd64_macos_bazel.yml
index 08236edd8e..ae1810691d 100644
--- a/.github/workflows/amd64_macos_bazel.yml
+++ b/.github/workflows/amd64_macos_bazel.yml
@@ -1,15 +1,23 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 MacOS Bazel
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
+env:
+  cache-root: /private/tmp/bazel
+
 # Building using the github runner environement directly.
 jobs:
-  native:
+  amd64-MacOS-Bazel-Python:
     strategy:
       matrix:
         python: [
@@ -19,19 +27,20 @@ jobs:
           #{version: '3.13'},
         ]
       fail-fast: false
-    name: amd64•MacOS•Bazel•Python-${{matrix.python.version}}
+    env:
+      cache-name: ${{github.job}}-${{matrix.python.version}}
     runs-on: macos-13 # last macos intel based runner
     steps:
       - uses: actions/checkout@v5
       - name: Set Java to OpenJDK 17 (Temurin)
-        uses: actions/setup-java@v4
+        uses: actions/setup-java@v5
         with:
           distribution: 'temurin'
           java-version: '17'
       - name: Check mvn
         run: mvn --version
       - name: Setup Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{matrix.python.version}}
       - name: Check Python
@@ -46,21 +55,26 @@ jobs:
         run: |
           sed -i '' -e 's/\(DEFAULT_PYTHON =\) "3.[0-9]*"/\1 "${{matrix.python.version}}"/g' MODULE.bazel
           cat MODULE.bazel
+      - name: Restore bazel cache
+        uses: actions/cache/restore@v4
+        id: bazel-cache-restore
+        with:
+          key: ${{env.cache-name}}
+          path: ${{env.cache-root}}
       - name: Build
-        run: >
-          bazel build
-          -c opt
-          --subcommands=pretty_print
-          //ortools/... //examples/...
+        run: bazel --output_user_root=${{env.cache-root}} build --config=ci //ortools/... //examples/...
       - name: Test
-        run: >
-          bazel test
-          -c opt
-          --test_output=errors
-          //ortools/... //examples/...
+        run: bazel --output_user_root=${{env.cache-root}} test --config=ci //ortools/... //examples/...
+      - name: Save Bazel cache for branch main even when Build and Test fail.
+        uses: actions/cache/save@v4
+        # https://docs.github.com/en/actions/reference/workflows-and-actions/dependency-caching#restrictions-for-accessing-a-cache
+        if: always() && github.ref == 'refs/heads/main'
+        with:
+          key: ${{env.cache-name}}-${{github.sha}}
+          path: ${{env.cache-root}}
 
   amd64_macos_bazel:
     runs-on: ubuntu-latest
-    needs: native
+    needs: amd64-MacOS-Bazel-Python
     steps:
       - uses: actions/checkout@v5
diff --git a/.github/workflows/amd64_macos_cmake_cpp.yml b/.github/workflows/amd64_macos_cmake_cpp.yml
index c6fb2327ff..fbcabdd0de 100644
--- a/.github/workflows/amd64_macos_cmake_cpp.yml
+++ b/.github/workflows/amd64_macos_cmake_cpp.yml
@@ -1,13 +1,22 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 MacOS CMake C++
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     strategy:
@@ -19,8 +28,38 @@ jobs:
       fail-fast: false
     name: amd64•MacOS•CMake(${{matrix.cmake.name}})•C++
     runs-on: macos-13 # last macos intel based runner
+    env:
+      deps_src_key: amd64_macos_cpp_deps_src
+      deps_build_key: amd64_macos_cpp_deps_build_${{matrix.cmake.name}}
+      ccache_key: amd64_macos_cpp_ccache_${{matrix.cmake.name}}
     steps:
       - uses: actions/checkout@v5
+      - name: Install Dependencies
+        run: brew install ccache
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
@@ -49,6 +88,32 @@ jobs:
           --config ${{matrix.cmake.config}}
           --target ${{matrix.cmake.install_target}}
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   amd64_macos_cmake_cpp:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/amd64_macos_cmake_dotnet.yml b/.github/workflows/amd64_macos_cmake_dotnet.yml
index cec3a15407..7138ba1661 100644
--- a/.github/workflows/amd64_macos_cmake_dotnet.yml
+++ b/.github/workflows/amd64_macos_cmake_dotnet.yml
@@ -1,13 +1,22 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 MacOS CMake .Net
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     strategy:
@@ -19,18 +28,46 @@ jobs:
       fail-fast: false
     name: amd64•MacOS•CMake(${{matrix.cmake.name}})•.Net
     runs-on: macos-13 # last macos intel based runner
+    env:
+      deps_src_key: amd64_macos_dotnet_deps_src
+      deps_build_key: amd64_macos_dotnet_deps_build_${{matrix.cmake.name}}
+      ccache_key: amd64_macos_dotnet_ccache_${{matrix.cmake.name}}
     steps:
       - uses: actions/checkout@v5
-      - name: Swig install
+      - name: Install Dependencies
         run: |
-          brew install swig
+          brew install ccache swig
           swig -version
       - name: Setup .NET 8.0
-        uses: actions/setup-dotnet@v4
+        uses: actions/setup-dotnet@v5
         with:
           dotnet-version: 8.0.x
       - name: Check dotnet
         run: dotnet --info
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
@@ -60,6 +97,32 @@ jobs:
           --config ${{matrix.cmake.config}}
           --target ${{matrix.cmake.install_target}}
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   amd64_macos_cmake_dotnet:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/amd64_macos_cmake_java.yml b/.github/workflows/amd64_macos_cmake_java.yml
index 683aff028d..071031f5ae 100644
--- a/.github/workflows/amd64_macos_cmake_java.yml
+++ b/.github/workflows/amd64_macos_cmake_java.yml
@@ -1,13 +1,22 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 MacOS CMake Java
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     strategy:
@@ -19,14 +28,42 @@ jobs:
       fail-fast: false
     name: amd64•MacOS•CMake(${{matrix.cmake.name}})•Java
     runs-on: macos-13 # last macos intel based runner
+    env:
+      deps_src_key: amd64_macos_java_deps_src
+      deps_build_key: amd64_macos_java_deps_build_${{matrix.cmake.name}}
+      ccache_key: amd64_macos_java_ccache_${{matrix.cmake.name}}
     steps:
       - uses: actions/checkout@v5
-      - name: Swig install
+      - name: Install Dependencies
         run: |
-          brew install swig
+          brew install ccache swig
           swig -version
       - name: Check java
         run: java -version
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
@@ -56,6 +93,32 @@ jobs:
           --config ${{matrix.cmake.config}}
           --target ${{matrix.cmake.install_target}}
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   amd64_macos_cmake_java:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/amd64_macos_cmake_python.yml b/.github/workflows/amd64_macos_cmake_python.yml
index 4c9acb7d4d..eafa59d0b5 100644
--- a/.github/workflows/amd64_macos_cmake_python.yml
+++ b/.github/workflows/amd64_macos_cmake_python.yml
@@ -1,13 +1,22 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 MacOS CMake Python
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     strategy:
@@ -17,29 +26,57 @@ jobs:
           {name: "Make", generator: "Unix Makefiles", config: Release, build_target: all, test_target: test, install_target: install},
         ]
         python: [
-          {version: "3.9"},
-          {version: "3.10"},
-          {version: "3.11"},
-          {version: "3.12"},
+          #{version: "3.9"},
+          #{version: "3.10"},
+          #{version: "3.11"},
+          #{version: "3.12"},
           {version: "3.13"},
         ]
       fail-fast: false
     name: amd64•MacOS•CMake(${{matrix.cmake.name}})•Python-${{matrix.python.version}}
     runs-on: macos-13 # last macos intel based runner
+    env:
+      deps_src_key: amd64_macos_python_deps_src
+      deps_build_key: amd64_macos_python_deps_build_${{matrix.cmake.name}}
+      ccache_key: amd64_macos_python_ccache_${{matrix.cmake.name}}
     steps:
       - uses: actions/checkout@v5
-      - name: Swig install
+      - name: Install Dependencies
         run: |
-          brew install swig
+          brew install ccache swig
           swig -version
       - name: Setup Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{matrix.python.version}}
       - name: Update Path
         run: |
           echo "$HOME/Library/Python/${{matrix.python.version}}/bin" >> $GITHUB_PATH
           echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
@@ -69,6 +106,32 @@ jobs:
           --config ${{matrix.cmake.config}}
           --target ${{matrix.cmake.install_target}}
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   amd64_macos_cmake_python:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/amd64_web.yml b/.github/workflows/amd64_web.yml
index 050d7a4db8..73a6986df5 100644
--- a/.github/workflows/amd64_web.yml
+++ b/.github/workflows/amd64_web.yml
@@ -1,7 +1,8 @@
 # ref: https://github.com/docker-library/official-images
 name: amd64 Web
 
-on: [push, pull_request, workflow_dispatch]
+# still experimental
+on: [workflow_dispatch]
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
diff --git a/.github/workflows/amd64_windows_bazel.yml b/.github/workflows/amd64_windows_bazel.yml
index e154ba6039..3b0fb5bb60 100644
--- a/.github/workflows/amd64_windows_bazel.yml
+++ b/.github/workflows/amd64_windows_bazel.yml
@@ -1,15 +1,23 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Windows Bazel
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
+env:
+  cache-root: '%USERPROFILE%\AppData\Local\Temp\bazel'
+
 # Building using the github runner environement directly.
 jobs:
-  native:
+  amd64-Windows-Bazel-Python:
     strategy:
       matrix:
         python: [
@@ -19,11 +27,12 @@ jobs:
         #  {version: '3.13'},
         ]
       fail-fast: false # Don't cancel all jobs if one fails.
-    name: amd64•Windows•Bazel•Python-${{matrix.python.version}}
+    env:
+      cache-name: ${{github.job}}-${{matrix.python.version}}
     runs-on: windows-2022
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-java@v4
+      - uses: actions/setup-java@v5
         with:
           distribution: 'temurin'
           java-version: '17'
@@ -32,7 +41,7 @@ jobs:
       - name: Check mvn
         run: mvn --version
       - name: Setup Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{matrix.python.version}}
       - name: Check Python
@@ -41,21 +50,26 @@ jobs:
         run: choco install bazel
       - name: Check Bazel
         run: bazel version
+      - name: Restore bazel cache
+        uses: actions/cache/restore@v4
+        id: bazel-cache-restore
+        with:
+          key: ${{env.cache-name}}
+          path: ${{env.cache-root}}
       - name: Build
-        run: >
-          bazel build
-          -c opt
-          --subcommands=pretty_print
-          //ortools/... //examples/...
+        run: bazel --output_user_root=${{env.cache-root}} build --config=ci //ortools/... //examples/...
       - name: Test
-        run: >
-          bazel test
-          -c opt
-          --test_output=errors
-          //ortools/... //examples/...
+        run: bazel --output_user_root=${{env.cache-root}} test --config=ci //ortools/... //examples/...
+      - name: Save Bazel cache for branch main even when Build and Test fail.
+        uses: actions/cache/save@v4
+        # https://docs.github.com/en/actions/reference/workflows-and-actions/dependency-caching#restrictions-for-accessing-a-cache
+        if: always() && github.ref == 'refs/heads/main'
+        with:
+          key: ${{env.cache-name}}-${{github.sha}}
+          path: ${{env.cache-root}}
 
   amd64_windows_bazel:
     runs-on: ubuntu-latest
-    needs: native
+    needs: amd64-Windows-Bazel-Python
     steps:
       - uses: actions/checkout@v5
diff --git a/.github/workflows/amd64_windows_cmake_cpp.yml b/.github/workflows/amd64_windows_cmake_cpp.yml
index 205c77420f..7eff2e6cd4 100644
--- a/.github/workflows/amd64_windows_cmake_cpp.yml
+++ b/.github/workflows/amd64_windows_cmake_cpp.yml
@@ -1,7 +1,12 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Windows CMake C++
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
@@ -13,16 +18,33 @@ jobs:
     strategy:
       matrix:
         cmake: [
-          {name: "VS2022", generator: "Visual Studio 17 2022", config: Release, build_target: ALL_BUILD, test_target: RUN_TESTS, install_target: INSTALL},
-          # {name: "VS2022", generator: "Visual Studio 17 2022", config: Debug, build_target: ALL_BUILD, test_target: RUN_TESTS, install_target: INSTALL}, # too many symbols
+          {name: "VS2022", generator: "Visual Studio 17 2022", config: Release},
+          # {name: "VS2022", generator: "Visual Studio 17 2022", config: Debug}, # too many symbols
         ]
       fail-fast: false
     name: amd64•Windows•CMake(${{matrix.cmake.name}},${{matrix.cmake.config}})•C++
     runs-on: windows-latest
     env:
+      deps_src_key: amd64_windows_cpp_deps_src
+      deps_build_key: amd64_windows_cpp_deps_build_${{matrix.cmake.config}}
       CTEST_OUTPUT_ON_FAILURE: 1
     steps:
       - uses: actions/checkout@v5
+
+      # CONFIGURING CACHES
+      - name: Cache CMake dependency source code
+        uses: actions/cache@v4
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Cache CMake dependency build
+        uses: actions/cache@v4
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+
       - name: Check CMake
         run: |
           cmake --version
@@ -38,19 +60,19 @@ jobs:
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.build_target}}
+          --target ALL_BUILD
           -v -j2
       - name: Test
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.test_target}}
+          --target RUN_TESTS
           -v
       - name: Install
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.install_target}}
+          --target INSTALL
           -v
 
   amd64_windows_cmake_cpp:
diff --git a/.github/workflows/amd64_windows_cmake_dotnet.yml b/.github/workflows/amd64_windows_cmake_dotnet.yml
index dab5372296..01d6deef10 100644
--- a/.github/workflows/amd64_windows_cmake_dotnet.yml
+++ b/.github/workflows/amd64_windows_cmake_dotnet.yml
@@ -1,7 +1,12 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Windows CMake .Net
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
@@ -13,47 +18,66 @@ jobs:
     strategy:
       matrix:
         cmake: [
-          {name: "VS2022", generator: "Visual Studio 17 2022", config: Release, build_target: ALL_BUILD, test_target: RUN_TESTS, install_target: INSTALL},
+          {name: "VS2022", generator: "Visual Studio 17 2022", config: Release},
         ]
       fail-fast: false
     name: amd64•Windows•CMake(${{matrix.cmake.name}})•.Net
     runs-on: windows-latest
     env:
+      deps_src_key: amd64_windows_dotnet_deps_src
+      deps_build_key: amd64_windows_dotnet_deps_build_${{matrix.cmake.config}}
       CTEST_OUTPUT_ON_FAILURE: 1
     steps:
       - uses: actions/checkout@v5
       - name: Setup .NET 8.0
-        uses: actions/setup-dotnet@v4
+        uses: actions/setup-dotnet@v5
         with:
           dotnet-version: 8.0.x
       - name: Check dotnet
         run: dotnet --info
+
+      # CONFIGURING CACHES
+      - name: Cache CMake dependency source code
+        uses: actions/cache@v4
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Cache CMake dependency build
+        uses: actions/cache@v4
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+
       - name: Check CMake
-        run: cmake --version
+        run: |
+          cmake --version
+          cmake -G || true
       - name: Configure
         run: >
           cmake -S. -Bbuild
           -G "${{matrix.cmake.generator}}"
-          -DCMAKE_BUILD_TYPE=${{matrix.cmake.config}}
+          -DCMAKE_CONFIGURATION_TYPES=${{matrix.cmake.config}}
           -DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF
           -DBUILD_DOTNET=ON
       - name: Build
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.build_target}}
+          --target ALL_BUILD
           -v -j2
       - name: Test
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.test_target}}
+          --target RUN_TESTS
           -v
       - name: Install
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.install_target}}
+          --target INSTALL
           -v
 
   amd64_windows_cmake_dotnet:
diff --git a/.github/workflows/amd64_windows_cmake_java.yml b/.github/workflows/amd64_windows_cmake_java.yml
index 9be5a93381..9965df3af5 100644
--- a/.github/workflows/amd64_windows_cmake_java.yml
+++ b/.github/workflows/amd64_windows_cmake_java.yml
@@ -1,7 +1,12 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Windows CMake Java
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
@@ -13,7 +18,7 @@ jobs:
     strategy:
       matrix:
         cmake: [
-          {name: "VS2022", generator: "Visual Studio 17 2022", config: Release, build_target: ALL_BUILD, test_target: RUN_TESTS, install_target: INSTALL},
+          {name: "VS2022", generator: "Visual Studio 17 2022", config: Release},
         ]
         java: [
           # see https://endoflife.date/azul-zulu
@@ -27,18 +32,21 @@ jobs:
           {distrib: 'temurin', version: '17'}, # 2027/10
           {distrib: 'temurin', version: '21'}, # 2029/12
           # see https://endoflife.date/microsoft-build-of-openjdk
-          {distrib: 'microsoft', version: '11'}, # 2027/09
-          {distrib: 'microsoft', version: '17'}, # 2027/09
-          {distrib: 'microsoft', version: '21'}, # 2028/09
+          # microsoft jdk seems to use an older redistributable
+          #{distrib: 'microsoft', version: '11'}, # 2027/09
+          #{distrib: 'microsoft', version: '17'}, # 2027/09
+          #{distrib: 'microsoft', version: '21'}, # 2028/09
         ]
       fail-fast: false
     name: amd64•Windows•CMake(${{matrix.cmake.name}})•${{matrix.java.distrib}}-${{matrix.java.version}}
     runs-on: windows-latest
     env:
+      deps_src_key: amd64_windows_java_deps_src
+      deps_build_key: amd64_windows_java_deps_build_${{matrix.cmake.config}}
       CTEST_OUTPUT_ON_FAILURE: 1
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-java@v4
+      - uses: actions/setup-java@v5
         with:
           distribution: ${{matrix.java.distrib}}
           java-version: ${{matrix.java.version}}
@@ -46,32 +54,49 @@ jobs:
         run: |
           java -version
           mvn --version
+
+      # CONFIGURING CACHES
+      - name: Cache CMake dependency source code
+        uses: actions/cache@v4
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Cache CMake dependency build
+        uses: actions/cache@v4
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+
       - name: Check CMake
-        run: cmake --version
+        run: |
+          cmake --version
+          cmake -G || true
       - name: Configure
         run: >
           cmake -S. -Bbuild
           -G "${{matrix.cmake.generator}}"
-          -DCMAKE_BUILD_TYPE=${{matrix.cmake.config}}
+          -DCMAKE_CONFIGURATION_TYPES=${{matrix.cmake.config}}
           -DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF
           -DBUILD_JAVA=ON
       - name: Build
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.build_target}}
+          --target ALL_BUILD
           -v -j2
       - name: Test
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.test_target}}
+          --target RUN_TESTS
           -v
       - name: Install
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.install_target}}
+          --target INSTALL
           -v
 
   amd64_windows_cmake_java:
diff --git a/.github/workflows/amd64_windows_cmake_python.yml b/.github/workflows/amd64_windows_cmake_python.yml
index 821775e92d..7ec0449f12 100644
--- a/.github/workflows/amd64_windows_cmake_python.yml
+++ b/.github/workflows/amd64_windows_cmake_python.yml
@@ -1,7 +1,12 @@
 # ref: https://github.com/actions/runner-images
 name: amd64 Windows CMake Python
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
@@ -13,23 +18,25 @@ jobs:
     strategy:
       matrix:
         cmake: [
-          {name: "VS2022", generator: "Visual Studio 17 2022", config: Release, build_target: ALL_BUILD, test_target: RUN_TESTS, install_target: INSTALL},
+          {name: "VS2022", generator: "Visual Studio 17 2022", config: Release},
         ]
         python: [
           {version: "3.9", dir: Python309},
-          {version: "3.10", dir: Python310},
-          {version: "3.11", dir: Python311},
-          {version: "3.12", dir: Python312},
+          #{version: "3.10", dir: Python310},
+          #{version: "3.11", dir: Python311},
+          #{version: "3.12", dir: Python312},
           {version: "3.13", dir: Python313},
         ]
       fail-fast: false
     name: amd64•Windows•CMake(${{matrix.cmake.name}})•Python-${{matrix.python.version}}
     runs-on: windows-latest
     env:
+      deps_src_key: amd64_windows_python_deps_src
+      deps_build_key: amd64_windows_python_deps_build_${{matrix.cmake.config}}
       CTEST_OUTPUT_ON_FAILURE: 1
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-python@v5
+      - uses: actions/setup-python@v6
         with:
           python-version: ${{matrix.python.version}}
       - name: Install python3
@@ -38,32 +45,49 @@ jobs:
         run: >
           echo "$((Get-Item ~).FullName)/AppData/Roaming/Python/${{matrix.python.dir}}/Scripts" |
           Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append
+
+      # CONFIGURING CACHES
+      - name: Cache CMake dependency source code
+        uses: actions/cache@v4
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Cache CMake dependency build
+        uses: actions/cache@v4
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+
       - name: Check CMake
-        run: cmake --version
+        run: |
+          cmake --version
+          cmake -G || true
       - name: Configure
         run: >
           cmake -S. -Bbuild
           -G "${{matrix.cmake.generator}}"
-          -DCMAKE_BUILD_TYPE=${{matrix.cmake.config}}
+          -DCMAKE_CONFIGURATION_TYPES=${{matrix.cmake.config}}
           -DBUILD_CXX_SAMPLES=OFF -DBUILD_CXX_EXAMPLES=OFF
           -DBUILD_PYTHON=ON
       - name: Build
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.build_target}}
+          --target ALL_BUILD
           -v -j2
       - name: Test
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.test_target}}
+          --target RUN_TESTS
           -v
       - name: Install
         run: >
           cmake --build build
           --config ${{matrix.cmake.config}}
-          --target ${{matrix.cmake.install_target}}
+          --target INSTALL
           -v
 
   amd64_windows_cmake_python:
diff --git a/.github/workflows/arm64_macos_bazel.yml b/.github/workflows/arm64_macos_bazel.yml
index 73af4c8ce4..14b23c7fab 100644
--- a/.github/workflows/arm64_macos_bazel.yml
+++ b/.github/workflows/arm64_macos_bazel.yml
@@ -1,15 +1,23 @@
 # ref: https://github.com/actions/runner-images
 name: arm64 MacOS Bazel
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
+env:
+  cache-root: /private/tmp/bazel
+
 # Building using the github runner environement directly.
 jobs:
-  native:
+  arm64-MacOS-Bazel-Python:
     strategy:
       matrix:
         python: [
@@ -19,19 +27,20 @@ jobs:
           #{version: '3.13'},
         ]
       fail-fast: false
-    name: arm64•MacOS•Bazel•Python-${{matrix.python.version}}
+    env:
+      cache-name: ${{github.job}}-${{matrix.python.version}}
     runs-on: macos-latest # macos arm64 based runner
     steps:
       - uses: actions/checkout@v5
       - name: Set Java to OpenJDK 17 (Temurin)
-        uses: actions/setup-java@v4
+        uses: actions/setup-java@v5
         with:
           distribution: 'temurin'
           java-version: '17'
       - name: Check mvn
         run: mvn --version
       - name: Setup Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{matrix.python.version}}
       - name: Check Python
@@ -46,21 +55,26 @@ jobs:
         run: |
           sed -i '' -e 's/\(DEFAULT_PYTHON =\) "3.[0-9]*"/\1 "${{matrix.python.version}}"/g' MODULE.bazel
           cat MODULE.bazel
+      - name: Restore bazel cache
+        uses: actions/cache/restore@v4
+        id: bazel-cache-restore
+        with:
+          key: ${{env.cache-name}}
+          path: ${{env.cache-root}}
       - name: Build
-        run: >
-          bazel build
-          -c opt
-          --subcommands=pretty_print
-          //ortools/... //examples/...
+        run: bazel --output_user_root=${{env.cache-root}} build --config=ci //ortools/... //examples/...
       - name: Test
-        run: >
-          bazel test
-          -c opt
-          --test_output=errors
-          //ortools/... //examples/...
+        run: bazel --output_user_root=${{env.cache-root}} test --config=ci //ortools/... //examples/...
+      - name: Save Bazel cache for branch main even when Build and Test fail.
+        uses: actions/cache/save@v4
+        # https://docs.github.com/en/actions/reference/workflows-and-actions/dependency-caching#restrictions-for-accessing-a-cache
+        if: always() && github.ref == 'refs/heads/main'
+        with:
+          key: ${{env.cache-name}}-${{github.sha}}
+          path: ${{env.cache-root}}
 
   arm64_macos_bazel:
     runs-on: ubuntu-latest
-    needs: native
+    needs: arm64-MacOS-Bazel-Python
     steps:
       - uses: actions/checkout@v5
diff --git a/.github/workflows/arm64_macos_cmake_cpp.yml b/.github/workflows/arm64_macos_cmake_cpp.yml
index bbd4dfcb43..13f77d0736 100644
--- a/.github/workflows/arm64_macos_cmake_cpp.yml
+++ b/.github/workflows/arm64_macos_cmake_cpp.yml
@@ -1,13 +1,22 @@
 # ref: https://github.com/actions/runner-images
 name: arm64 MacOS CMake C++
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     strategy:
@@ -19,8 +28,38 @@ jobs:
       fail-fast: false
     name: arm64•MacOS•CMake(${{matrix.cmake.name}})•C++
     runs-on: macos-latest # macos M1 based runner
+    env:
+      deps_src_key: arm64_macos_cpp_deps_src
+      deps_build_key: arm64_macos_cpp_deps_build_${{matrix.cmake.name}}
+      ccache_key: arm64_macos_cpp_ccache_${{matrix.cmake.name}}
     steps:
       - uses: actions/checkout@v5
+      - name: Install Dependencies
+        run: brew install ccache
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
@@ -49,6 +88,32 @@ jobs:
           --config ${{matrix.cmake.config}}
           --target ${{matrix.cmake.install_target}}
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   arm64_macos_cmake_cpp:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/arm64_macos_cmake_dotnet.yml b/.github/workflows/arm64_macos_cmake_dotnet.yml
index 3887ac92f9..5b14908ce6 100644
--- a/.github/workflows/arm64_macos_cmake_dotnet.yml
+++ b/.github/workflows/arm64_macos_cmake_dotnet.yml
@@ -1,13 +1,22 @@
 # ref: https://github.com/actions/runner-images
 name: arm64 MacOS CMake .Net
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     strategy:
@@ -19,18 +28,46 @@ jobs:
       fail-fast: false
     name: arm64•MacOS•CMake(${{matrix.cmake.name}})•.Net
     runs-on: macos-latest # macos arm64 based runner
+    env:
+      deps_src_key: arm64_macos_dotnet_deps_src
+      deps_build_key: arm64_macos_dotnet_deps_build_${{matrix.cmake.name}}
+      ccache_key: arm64_macos_dotnet_ccache_${{matrix.cmake.name}}
     steps:
       - uses: actions/checkout@v5
-      - name: Swig install
+      - name: Install Dependencies
         run: |
-          brew install swig
+          brew install ccache swig
           swig -version
       - name: Setup .NET 8.0
-        uses: actions/setup-dotnet@v4
+        uses: actions/setup-dotnet@v5
         with:
           dotnet-version: 8.0.x
       - name: Check dotnet
         run: dotnet --info
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
@@ -60,6 +97,32 @@ jobs:
           --config ${{matrix.cmake.config}}
           --target ${{matrix.cmake.install_target}}
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   arm64_macos_cmake_dotnet:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/arm64_macos_cmake_java.yml b/.github/workflows/arm64_macos_cmake_java.yml
index 0ee363370e..cb6e2e84cd 100644
--- a/.github/workflows/arm64_macos_cmake_java.yml
+++ b/.github/workflows/arm64_macos_cmake_java.yml
@@ -1,13 +1,22 @@
 # ref: https://github.com/actions/runner-images
 name: arm64 MacOS CMake Java
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     strategy:
@@ -19,14 +28,42 @@ jobs:
       fail-fast: false
     name: arm64•MacOS•CMake(${{matrix.cmake.name}})•Java
     runs-on: macos-latest # macos arm64 based runner
+    env:
+      deps_src_key: arm64_macos_java_deps_src
+      deps_build_key: arm64_macos_java_deps_build_${{matrix.cmake.name}}
+      ccache_key: arm64_macos_java_ccache_${{matrix.cmake.name}}
     steps:
       - uses: actions/checkout@v5
-      - name: Swig install
+      - name: Install Dependencies
         run: |
-          brew install swig
+          brew install ccache swig
           swig -version
       - name: Check java
         run: java -version
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
@@ -56,6 +93,32 @@ jobs:
           --config ${{matrix.cmake.config}}
           --target ${{matrix.cmake.install_target}}
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   arm64_macos_cmake_java:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/arm64_macos_cmake_python.yml b/.github/workflows/arm64_macos_cmake_python.yml
index ca4df6011e..1c59a2ca5e 100644
--- a/.github/workflows/arm64_macos_cmake_python.yml
+++ b/.github/workflows/arm64_macos_cmake_python.yml
@@ -1,13 +1,22 @@
 # ref: https://github.com/actions/runner-images
 name: arm64 MacOS CMake Python
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
   cancel-in-progress: true
 
 # Building using the github runner environement directly.
+env:
+  CCACHE_BASEDIR: ${{github.workspace}}
+  CCACHE_DIR: ${{github.workspace}}/.ccache
+
 jobs:
   native:
     strategy:
@@ -17,29 +26,57 @@ jobs:
           {name: "Make", generator: "Unix Makefiles", config: Release, build_target: all, test_target: test, install_target: install},
         ]
         python: [
-          {version: "3.9"},
-          {version: "3.10"},
-          {version: "3.11"},
+          #{version: "3.9"},
+          #{version: "3.10"},
+          #{version: "3.11"},
           {version: "3.12"},
-          {version: "3.13"},
+          #{version: "3.13"},
         ]
       fail-fast: false
     name: arm64•MacOS•CMake(${{matrix.cmake.name}})•Python-${{matrix.python.version}}
     runs-on: macos-latest # macos arm64 based runner
+    env:
+      deps_src_key: arm64_macos_python_deps_src
+      deps_build_key: arm64_macos_python_deps_build_${{matrix.cmake.name}}
+      ccache_key: arm64_macos_python_ccache_${{matrix.cmake.name}}
     steps:
       - uses: actions/checkout@v5
-      - name: Swig install
+      - name: Install Dependencies
         run: |
-          brew install swig
+          brew install ccache swig
           swig -version
       - name: Setup Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{matrix.python.version}}
       - name: Update Path
         run: |
           echo "$HOME/Library/Python/${{matrix.python.version}}/bin" >> $GITHUB_PATH
           echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+      # RESTORING CACHES
+      - name: Restore CMake dependency source code
+        uses: actions/cache/restore@v4
+        id: deps_src_restore
+        with:
+          key: ${{env.deps_src_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: ${{github.workspace}}/build/_deps/*-src
+      - name: Restore CMake dependency build
+        uses: actions/cache/restore@v4
+        id: deps_build_restore
+        with:
+          key: ${{env.deps_build_key}}-${{hashFiles('CMakeLists.txt', 'cmake/**')}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Restore CCache
+        uses: actions/cache/restore@v4
+        id: ccache_restore
+        with:
+          key: ${{env.ccache_key}}-${{github.sha}}
+          restore-keys: ${{env.ccache_key}}-
+          path: ${{env.CCACHE_DIR}}
+
       - name: Check CMake
         run: cmake --version
       - name: Configure
@@ -69,6 +106,32 @@ jobs:
           --config ${{matrix.cmake.config}}
           --target ${{matrix.cmake.install_target}}
           -v
+      - name: CCache stats
+        run: |
+          ccache --show-stats
+          ccache --zero-stats
+
+      # SAVING CACHES
+      - name: Save CCache
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.ccache_restore.outputs.cache-primary-key}}
+          path: ${{env.CCACHE_DIR}}
+      - name: Save CMake dependency build
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_build_restore.outputs.cache-primary-key}}
+          path: |
+            ${{github.workspace}}/build/_deps/*-build
+            ${{github.workspace}}/build/_deps/*-subbuild
+      - name: Save CMake dependency source code
+        if: github.ref == 'refs/heads/main'
+        uses: actions/cache/save@v4
+        with:
+          key: ${{steps.deps_src_restore.outputs.cache-primary-key}}
+          path: ${{github.workspace}}/build/_deps/*-src
 
   arm64_macos_cmake_python:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/check_format.yml b/.github/workflows/check_format.yml
index 4a7f8c79cd..b999e80494 100644
--- a/.github/workflows/check_format.yml
+++ b/.github/workflows/check_format.yml
@@ -1,6 +1,11 @@
 name: Check Format
 
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
diff --git a/.github/workflows/mips_toolchain.yml b/.github/workflows/mips_toolchain.yml
index 1becd15d76..d75e27ce6b 100644
--- a/.github/workflows/mips_toolchain.yml
+++ b/.github/workflows/mips_toolchain.yml
@@ -1,7 +1,7 @@
 # ref: https://codescape.mips.com/components/toolchain/2021.09-01/downloads.html
 name: mips Toolchain
 
-on: [push, pull_request, workflow_dispatch]
+on: [workflow_dispatch]
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}
diff --git a/.github/workflows/powerpc_toolchain.yml b/.github/workflows/powerpc_toolchain.yml
index d23e220bc7..76710e5ab0 100644
--- a/.github/workflows/powerpc_toolchain.yml
+++ b/.github/workflows/powerpc_toolchain.yml
@@ -1,7 +1,7 @@
 # ref: https://toolchains.bootlin.com/
 name: powerpc Toolchain
 
-on: [push, pull_request, workflow_dispatch]
+on: [workflow_dispatch]
 
 concurrency:
   group: ${{github.workflow}}-${{github.ref}}