diff --git a/.github/workflows/Fortran-tests-linux.yml b/.github/workflows/Fortran-tests-linux.yml
index 95e0265cb..299914e0c 100644
--- a/.github/workflows/Fortran-tests-linux.yml
+++ b/.github/workflows/Fortran-tests-linux.yml
@@ -44,6 +44,7 @@ jobs:
           cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} \
                                                -DMUMPS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
                                                -DMETIS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
+                                               -DKRYLOV_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
                                                -DBQPD=${{github.workspace}}/dependencies/lib/libbqpd.a \
                                                -DMUMPS_LIBRARY=${{github.workspace}}/dependencies/lib/libdmumps.a \
                                                -DMUMPS_COMMON_LIBRARY=${{github.workspace}}/dependencies/lib/libmumps_common.a \
@@ -51,6 +52,7 @@ jobs:
                                                -DMUMPS_MPISEQ_LIBRARY=${{github.workspace}}/dependencies/lib/libmpiseq.a \
                                                -DHIGHS=${{github.workspace}}/dependencies/lib/libhighs.a \
                                                -DMETIS_LIBRARY=${{github.workspace}}/dependencies/lib/libmetis.a \
+                                               -DKRYLOV=${{github.workspace}}/dependencies/lib/libkrylov.so \
                                                -DBLAS_LIBRARIES="${{github.workspace}}/dependencies/lib/libblas.a;${{github.workspace}}/dependencies/lib/libcblas.a" \
                                                -DLAPACK_LIBRARIES=${{github.workspace}}/dependencies/lib/liblapack.a \
                                                -DBUILD_STATIC_LIBS=ON \
@@ -61,7 +63,7 @@ jobs:
 
       - name: Compile Fortran tests
         working-directory: ${{github.workspace}}/interfaces/Fortran
-        run: gfortran example_uno.f90 -o example_uno -L../../build -luno -L${{github.workspace}}/dependencies/lib -lhighs -ldmumps -lmumps_common -lmpiseq -lpord -lmetis -lbqpd -llapack -lcblas -lblas -lstdc++
+        run: gfortran example_uno.f90 -o example_uno -L../../build -luno -L${{github.workspace}}/dependencies/lib -lhighs -ldmumps -lmumps_common -lmpiseq -lpord -lmetis -lbqpd -lkrylov -llapack -lcblas -lblas -lstdc++
 
       - name: Run Fortran tests
         working-directory: ${{github.workspace}}/interfaces/Fortran
diff --git a/.github/workflows/build-python-wheels.yml b/.github/workflows/build-python-wheels.yml
index abc82232b..14e5d2b3e 100644
--- a/.github/workflows/build-python-wheels.yml
+++ b/.github/workflows/build-python-wheels.yml
@@ -26,7 +26,9 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  CIBW_TEST_COMMAND: python {project}/interfaces/Python/example/example_hs015.py
+  CIBW_TEST_COMMAND: >
+    python {project}/interfaces/Python/tests/run_wheel_tests.py
+  CIBW_TEST_REQUIRES: numpy
 
 jobs:
   build_wheels:
@@ -52,6 +54,11 @@ jobs:
         with:
           python-version: "3.11"
 
+      - name: Install unzip (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: C:/msys64/usr/bin/bash -lc "pacman -Sy --noconfirm --needed unzip"
+
       - run: pip install cibuildwheel
         if: runner.os != 'Windows'
 
@@ -72,17 +79,41 @@ jobs:
           echo "LIBGFORTRAN_FOLDER=$LIBGFORTRAN_FOLDER" >> $GITHUB_ENV
           echo "OPENMP_LIB=$(brew --prefix libomp)/lib/libomp.dylib" >> $GITHUB_ENV
 
+      - name: Install matching MinGW (GCC 14.2.0 posix-seh-msvcrt)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          $url = "https://github.com/niXman/mingw-builds-binaries/releases/download/14.2.0-rt_v12-rev0/x86_64-14.2.0-release-posix-seh-msvcrt-rt_v12-rev0.7z"
+          Invoke-WebRequest $url -OutFile mingw.7z
+          7z x mingw.7z -oC:\mingw1420 -y          # clean dir, NOT C:\mingw64
+          # the archive contains a top-level mingw64\ folder, so the compiler ends up at:
+          C:\mingw1420\mingw64\bin\gcc --version
+          C:\mingw1420\mingw64\bin\g++ --version
+
+      - name: Put 14.2 toolchain first on PATH (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: echo "C:\mingw1420\mingw64\bin" | Out-File -FilePath $env:GITHUB_PATH -Append
+
       - name: Build wheels (Linux)
         if: runner.os == 'Linux'
         run: cibuildwheel --output-dir ${{github.workspace}}/wheelhouse
         env:
           CIBW_BUILD: ${{ matrix.sys.build }}
-          CIBW_SKIP: cp*-*_i686 *-win32
-          CIBW_ENVIRONMENT_LINUX:
+          CIBW_SKIP: cp38-* *_i686 *-win32
+          CIBW_MANYLINUX_X86_64_IMAGE: manylinux_2_34
+          CIBW_MANYLINUX_AARCH64_IMAGE: manylinux_2_34
+          CIBW_ENVIRONMENT_LINUX: >
             CMAKE_GENERATOR=Ninja
             CMAKE_BUILD_PARALLEL_LEVEL=$(nproc)
+            LD_LIBRARY_PATH=/project/dependencies/lib:/project/dependencies/lib/julia
+            AUDITWHEEL_PLAT=manylinux_2_35_$(uname -m)
+          # Linux wheels need glibc 2.35; test them in a separate job
+          CIBW_TEST_SKIP: "*-manylinux_*"
           CIBW_BEFORE_ALL_LINUX:
             bash dependencies/scripts/download_dependencies.sh
+          CIBW_REPAIR_WHEEL_COMMAND_LINUX: >
+            auditwheel repair --exclude libkrylov.so --exclude 'libjulia*.so*' --exclude 'libopenlibm*.so*' -w {dest_dir} {wheel}
 
       - name: Build wheels (macOS)
         if: startsWith(matrix.sys.os, 'macos')
@@ -114,6 +145,10 @@ jobs:
             CMAKE_TOOLCHAIN_FILE=/tmp/clang_toolchain.cmake
             CMAKE_GENERATOR=Ninja
             CMAKE_BUILD_PARALLEL_LEVEL=$(sysctl -n hw.logicalcpu)
+          CIBW_CONFIG_SETTINGS_MACOS: >
+            cmake.define.KRYLOV=dependencies/lib/libkrylov.dylib
+          CIBW_REPAIR_WHEEL_COMMAND_MACOS: >
+            delocate-wheel --require-archs {delocate_archs} --ignore-missing-dependencies -w {dest_dir} -v {wheel}
 
       - name: Build wheels (Windows)
         if: runner.os == 'Windows'
@@ -121,29 +156,67 @@ jobs:
         shell: pwsh
         env:
           CIBW_SKIP: cp314t-* cp*-*_i686 *-win32
-          CIBW_BEFORE_BUILD_WINDOWS: >
+          CIBW_BEFORE_ALL_WINDOWS: >
             C:/msys64/usr/bin/bash -lc "cd \"$(cygpath -u '{package}')\" && ./dependencies/scripts/download_dependencies.sh" &&
             pwsh -Command "Get-ChildItem -Path '{package}/dependencies' -Recurse |
             ForEach-Object { $_.LastWriteTime = Get-Date }"
           CIBW_REPAIR_WHEEL_COMMAND_WINDOWS: >
             pwsh -Command "$env:SOURCE_DATE_EPOCH='315532800';
-            delvewheel repair --add-path 'C:/msys64/mingw64/bin;dependencies/bin;dependencies/lib' -w {dest_dir} {wheel}"
+            delvewheel repair --no-mangle-all --add-path 'dependencies/bin;dependencies/lib' -w {dest_dir} {wheel}"
           CIBW_ENVIRONMENT_WINDOWS: >
             CMAKE_BUILD_PARALLEL_LEVEL=$(nproc)
             CMAKE_GENERATOR="MinGW Makefiles"
-            CMAKE_MAKE_PROGRAM=C:/mingw64/bin/mingw32-make.exe
-            CMAKE_C_COMPILER=C:/mingw64/bin/gcc.exe
-            CMAKE_CXX_COMPILER=C:/mingw64/bin/g++.exe
-            CMAKE_Fortran_COMPILER=C:/mingw64/bin/gfortran.exe
+            CMAKE_MAKE_PROGRAM=C:/mingw1420/mingw64/bin/mingw32-make.exe
+            CMAKE_C_COMPILER=C:/mingw1420/mingw64/bin/gcc.exe
+            CMAKE_CXX_COMPILER=C:/mingw1420/mingw64/bin/g++.exe
+            CMAKE_Fortran_COMPILER=C:/mingw1420/mingw64/bin/gfortran.exe
           CIBW_CONFIG_SETTINGS_WINDOWS: >
             cmake.define.METIS_LIBRARY=dependencies/bin/libmetis.dll
+            cmake.define.KRYLOV=dependencies/bin/libkrylov.dll
             cmake.define.AUXILIARY_LIBRARIES=dependencies/lib/libstdc++.a
 
       - name: Store artifacts
         uses: actions/upload-artifact@v4
+        if: success() || failure()
         with:
           name: cibw-wheels-${{ matrix.sys.os }}-${{ strategy.job-index }}
-          path: wheelhouse/*.whl
+          path: ${{ github.workspace }}/wheelhouse/*.whl
+          if-no-files-found: warn
+
+  # test the Linux wheels with glibc ≥ 2.35
+  test-linux-wheels:
+    name: Test Linux wheels (${{ matrix.runs-on }})
+    needs: build_wheels
+    runs-on: ${{ matrix.runs-on }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - runs-on: ubuntu-24.04
+            pattern: cibw-wheels-ubuntu-latest-*
+          - runs-on: ubuntu-24.04-arm
+            pattern: cibw-wheels-ubuntu-22.04-arm-*
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/download-artifact@v4
+        with:
+          pattern: ${{ matrix.pattern }}
+          path: wheelhouse
+          merge-multiple: true
+
+      - uses: actions/setup-python@v5
+        with: { python-version: '3.11' }
+
+      - name: Run tests
+        shell: bash
+        run: |
+          ls -R wheelhouse || { echo "no wheels downloaded"; exit 1; }
+          python -m pip install numpy
+          python -m pip install --no-index --find-links "$GITHUB_WORKSPACE/wheelhouse" --only-binary=:all: unopy
+          cd "$RUNNER_TEMP"   # run from outside the repo so 'import unopy' hits the wheel, not the source
+          python "$GITHUB_WORKSPACE/interfaces/Python/tests/run_wheel_tests.py"
 
   build_sdist:
     name: Build source distribution
@@ -275,4 +348,4 @@ jobs:
 
       - name: Run example
         working-directory: ${{github.workspace}}/interfaces/Python/example
-        run: python example_hs015.py
\ No newline at end of file
+        run: python example_hs015.py
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 3f87c901d..8965591db 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -192,6 +192,7 @@ jobs:
           -DCMAKE_FORTRAN_COMPILER=gfortran \
           -DMUMPS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
           -DMETIS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
+          -DKRYLOV_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
           -DBQPD=${{github.workspace}}/dependencies/lib/libbqpd.a \
           -DMETIS_LIBRARY=${{github.workspace}}/dependencies/lib/libmetis.a \
           -DMUMPS_LIBRARY=${{github.workspace}}/dependencies/lib/libdmumps.a \
@@ -201,6 +202,7 @@ jobs:
           -DBLAS_LIBRARIES="${{github.workspace}}/dependencies/lib/libcblas.a;${{github.workspace}}/dependencies/lib/libblas.a" \
           -DLAPACK_LIBRARIES=${{github.workspace}}/dependencies/lib/liblapack.a \
           -DHIGHS=${{github.workspace}}/dependencies/lib/libhighs.a \
+          -DKRYLOV=${{github.workspace}}/dependencies/lib/libkrylov.so \
           -DBUILD_STATIC_LIBS=ON \
           -DBUILD_SHARED_LIBS=ON
         
@@ -214,6 +216,7 @@ jobs:
           -DCMAKE_FORTRAN_COMPILER=ifx \
           -DMUMPS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
           -DMETIS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
+          -DKRYLOV_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
           -DBQPD=${{github.workspace}}/dependencies/lib/libbqpd.a \
           -DMETIS_LIBRARY=${{github.workspace}}/dependencies/lib/libmetis.a \
           -DMUMPS_LIBRARY=${{github.workspace}}/dependencies/lib/libdmumps.a \
@@ -223,6 +226,7 @@ jobs:
           -DBLAS_LIBRARIES="${{github.workspace}}/dependencies/lib/libcblas.a;${{github.workspace}}/dependencies/lib/libblas.a" \
           -DLAPACK_LIBRARIES=${{github.workspace}}/dependencies/lib/liblapack.a \
           -DHIGHS=${{github.workspace}}/dependencies/lib/libhighs.a \
+          -DKRYLOV=${{github.workspace}}/dependencies/lib/libkrylov.so \
           -DBUILD_STATIC_LIBS=ON \
           -DBUILD_SHARED_LIBS=ON
 
diff --git a/.github/workflows/unit-tests-asan-ubsan.yml b/.github/workflows/unit-tests-asan-ubsan.yml
new file mode 100644
index 000000000..67ab0cd37
--- /dev/null
+++ b/.github/workflows/unit-tests-asan-ubsan.yml
@@ -0,0 +1,207 @@
+name: Unit tests with ASAN/UBSAN
+
+on:
+  push:
+    branches: [ "main" ]
+    paths-ignore:
+      - '*.md'
+      - 'LICENSE'
+      - '*.cff'
+      - '*.yml'
+      - '*.yaml'
+      - 'docs/**'
+  pull_request:
+    branches: [ "main" ]
+    paths-ignore:
+      - '*.md'
+      - 'LICENSE'
+      - '*.cff'
+      - '*.yml'
+      - '*.yaml'
+      - 'docs/**'
+
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+
+          # ---------- LINUX ----------
+          - os: ubuntu-latest
+            toolchain: gcc
+            build_type: Debug
+            shell: bash
+
+          - os: ubuntu-24.04-arm
+            toolchain: gcc
+            build_type: Debug
+            shell: bash
+
+          # ---------- MACOS ----------
+          - os: macos-15
+            toolchain: gcc
+            build_type: Debug
+            shell: bash
+
+          - os: macos-15-intel
+            toolchain: gcc
+            build_type: Debug
+            shell: bash
+
+          # ---------- WINDOWS MINGW ----------
+          - os: windows-latest
+            toolchain: mingw
+            build_type: Debug
+            shell: msys2 {0}
+
+    env:
+      BUILD_TYPE: ${{ matrix.build_type }}
+
+    defaults:
+      run:
+        shell: ${{ matrix.shell }}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      # =========================================================
+      # TOOLCHAIN SETUP
+      # =========================================================
+
+      # ----- macOS -----
+      - name: Install libomp (macOS)
+        if: startsWith(matrix.os, 'macos')
+        run: |
+          brew install libomp
+          LIBGFORTRAN_FOLDER=$(dirname "$(gfortran-15 -print-file-name=libgfortran.dylib)")
+          echo "LIBGFORTRAN_FOLDER=$LIBGFORTRAN_FOLDER" >> $GITHUB_ENV
+          echo "OPENMP_LIB=$(brew --prefix libomp)/lib/libomp.dylib" >> $GITHUB_ENV
+
+      # ----- MinGW -----
+      - name: Setup MSYS2
+        if: matrix.toolchain == 'mingw'
+        uses: msys2/setup-msys2@v2
+        with:
+          path-type: inherit
+          msystem: MINGW64
+          update: true
+          install: |
+            mingw-w64-x86_64-gcc-fortran
+            mingw-w64-x86_64-cmake
+            mingw-w64-x86_64-make
+            mingw-w64-x86_64-metis
+
+      # =========================================================
+      # DEPENDENCIES
+      # =========================================================
+
+      - name: Download dependencies
+        run: bash dependencies/scripts/download_dependencies.sh
+
+      # =========================================================
+      # CONFIGURE
+      # =========================================================
+
+      - name: Configure (Linux with ASan + UBSan)
+        if: startsWith(matrix.os, 'ubuntu')
+        run: |
+          SANITIZER_FLAGS="-fsanitize=address,undefined -fno-omit-frame-pointer -fno-sanitize-recover=all -O1 -g"
+
+          echo "ASAN_OPTIONS=detect_leaks=1:abort_on_error=1" >> $GITHUB_ENV
+          echo "UBSAN_OPTIONS=print_stacktrace=1:halt_on_error=1" >> $GITHUB_ENV
+
+          cmake -B build \
+            -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} \
+            -DENABLE_TESTS=ON \
+            -DCMAKE_C_COMPILER=gcc \
+            -DCMAKE_CXX_COMPILER=g++ \
+            -DCMAKE_Fortran_COMPILER=gfortran \
+            -DCMAKE_C_FLAGS="${SANITIZER_FLAGS}" \
+            -DCMAKE_CXX_FLAGS="${SANITIZER_FLAGS}" \
+            -DCMAKE_EXE_LINKER_FLAGS="${SANITIZER_FLAGS}" \
+            -DCMAKE_SHARED_LINKER_FLAGS="${SANITIZER_FLAGS}" \
+            -DMUMPS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
+            -DMETIS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
+            -DBQPD=${{github.workspace}}/dependencies/lib/libbqpd.a \
+            -DMETIS_LIBRARY=${{github.workspace}}/dependencies/lib/libmetis.a \
+            -DMUMPS_LIBRARY=${{github.workspace}}/dependencies/lib/libdmumps.a \
+            -DMUMPS_COMMON_LIBRARY=${{github.workspace}}/dependencies/lib/libmumps_common.a \
+            -DMUMPS_PORD_LIBRARY=${{github.workspace}}/dependencies/lib/libpord.a \
+            -DMUMPS_MPISEQ_LIBRARY=${{github.workspace}}/dependencies/lib/libmpiseq.a \
+            -DBLAS_LIBRARIES="${{github.workspace}}/dependencies/lib/libcblas.a;${{github.workspace}}/dependencies/lib/libblas.a" \
+            -DLAPACK_LIBRARIES=${{github.workspace}}/dependencies/lib/liblapack.a \
+            -DHIGHS=${{github.workspace}}/dependencies/lib/libhighs.a \
+            -DBUILD_STATIC_LIBS=OFF \
+            -DBUILD_SHARED_LIBS=ON
+
+      - name: Configure (Mac)
+        if: startsWith(matrix.os, 'macos')
+        run: |
+          cmake -B build \
+            -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} \
+            -DENABLE_TESTS=ON \
+            -DCMAKE_C_COMPILER=clang \
+            -DCMAKE_CXX_COMPILER=clang++ \
+            -DCMAKE_Fortran_COMPILER=gfortran-15 \
+            -DCMAKE_EXE_LINKER_FLAGS="-L${{env.LIBGFORTRAN_FOLDER}}" \
+            -DCMAKE_SHARED_LINKER_FLAGS="-L${{env.LIBGFORTRAN_FOLDER}}" \
+            -DOpenMP_C_FLAGS="-Xpreprocessor -fopenmp" \
+            -DOpenMP_C_LIB_NAMES="omp" \
+            -DOpenMP_CXX_FLAGS="-Xpreprocessor -fopenmp" \
+            -DOpenMP_CXX_LIB_NAMES="omp" \
+            -DOpenMP_omp_LIBRARY=${{ env.OPENMP_LIB }} \
+            -DMUMPS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
+            -DMETIS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
+            -DBQPD=${{github.workspace}}/dependencies/lib/libbqpd.a \
+            -DMETIS_LIBRARY=${{github.workspace}}/dependencies/lib/libmetis.a \
+            -DMUMPS_LIBRARY=${{github.workspace}}/dependencies/lib/libdmumps.a \
+            -DMUMPS_COMMON_LIBRARY=${{github.workspace}}/dependencies/lib/libmumps_common.a \
+            -DMUMPS_PORD_LIBRARY=${{github.workspace}}/dependencies/lib/libpord.a \
+            -DMUMPS_MPISEQ_LIBRARY=${{github.workspace}}/dependencies/lib/libmpiseq.a \
+            -DBLAS_LIBRARIES="${{github.workspace}}/dependencies/lib/libcblas.a;${{github.workspace}}/dependencies/lib/libblas.a" \
+            -DLAPACK_LIBRARIES=${{github.workspace}}/dependencies/lib/liblapack.a \
+            -DHIGHS=${{github.workspace}}/dependencies/lib/libhighs.a \
+            -DBUILD_STATIC_LIBS=ON \
+            -DBUILD_SHARED_LIBS=OFF
+
+      - name: Configure (MinGW)
+        if: matrix.toolchain == 'mingw'
+        shell: msys2 {0}
+        run: |
+          cmake -G "MinGW Makefiles" \
+            -B build \
+            -DCMAKE_BUILD_TYPE=${BUILD_TYPE} \
+            -DENABLE_TESTS=ON \
+            -DCMAKE_C_COMPILER=gcc \
+            -DCMAKE_CXX_COMPILER=g++ \
+            -DCMAKE_Fortran_COMPILER=gfortran \
+            -DMUMPS_INCLUDE_DIR=${GITHUB_WORKSPACE}/dependencies/include \
+            -DMETIS_INCLUDE_DIR=/mingw64/include \
+            -DBQPD=${GITHUB_WORKSPACE}/dependencies/lib/libbqpd.a \
+            -DMETIS_LIBRARY=/mingw64/lib/libmetis.a \
+            -DMUMPS_LIBRARY=${GITHUB_WORKSPACE}/dependencies/lib/libdmumps.a \
+            -DMUMPS_COMMON_LIBRARY=${GITHUB_WORKSPACE}/dependencies/lib/libmumps_common.a \
+            -DMUMPS_PORD_LIBRARY=${GITHUB_WORKSPACE}/dependencies/lib/libpord.a \
+            -DMUMPS_MPISEQ_LIBRARY=${GITHUB_WORKSPACE}/dependencies/lib/libmpiseq.a \
+            -DBLAS_LIBRARIES="${GITHUB_WORKSPACE}/dependencies/lib/libcblas.a;${GITHUB_WORKSPACE}/dependencies/lib/libblas.a" \
+            -DLAPACK_LIBRARIES=${GITHUB_WORKSPACE}/dependencies/lib/liblapack.a \
+            -DHIGHS=${GITHUB_WORKSPACE}/dependencies/lib/libhighs.a \
+            -DBUILD_STATIC_LIBS=ON \
+            -DBUILD_SHARED_LIBS=OFF
+
+      # =========================================================
+      # BUILD
+      # =========================================================
+
+      - name: Build
+        run: cmake --build build --target run_unotest --config ${{env.BUILD_TYPE}} --parallel
+
+      # =========================================================
+      # TEST
+      # =========================================================
+
+      - name: Run tests
+        working-directory: build
+        run: ctest --output-on-failure -C ${{env.BUILD_TYPE}}
diff --git a/.github/workflows/unit-tests.yml b/.github/workflows/unit-tests.yml
index 09999c800..a0a993cf2 100644
--- a/.github/workflows/unit-tests.yml
+++ b/.github/workflows/unit-tests.yml
@@ -104,14 +104,9 @@ jobs:
       # CONFIGURE
       # =========================================================
 
-      - name: Configure (Linux with ASan + UBSan)
+      - name: Configure (Linux)
         if: startsWith(matrix.os, 'ubuntu')
         run: |
-          SANITIZER_FLAGS="-fsanitize=address,undefined -fno-omit-frame-pointer -fno-sanitize-recover=all -O1 -g"
-
-          echo "ASAN_OPTIONS=detect_leaks=1:abort_on_error=1" >> $GITHUB_ENV
-          echo "UBSAN_OPTIONS=print_stacktrace=1:halt_on_error=1" >> $GITHUB_ENV
-
           cmake -B build \
             -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} \
             -DENABLE_TESTS=ON \
@@ -124,6 +119,7 @@ jobs:
             -DCMAKE_SHARED_LINKER_FLAGS="${SANITIZER_FLAGS}" \
             -DMUMPS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
             -DMETIS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
+            -DKRYLOV_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
             -DBQPD=${{github.workspace}}/dependencies/lib/libbqpd.a \
             -DMETIS_LIBRARY=${{github.workspace}}/dependencies/lib/libmetis.a \
             -DMUMPS_LIBRARY=${{github.workspace}}/dependencies/lib/libdmumps.a \
@@ -133,6 +129,7 @@ jobs:
             -DBLAS_LIBRARIES="${{github.workspace}}/dependencies/lib/libcblas.a;${{github.workspace}}/dependencies/lib/libblas.a" \
             -DLAPACK_LIBRARIES=${{github.workspace}}/dependencies/lib/liblapack.a \
             -DHIGHS=${{github.workspace}}/dependencies/lib/libhighs.a \
+            -DKRYLOV=${{github.workspace}}/dependencies/lib/libkrylov.so \
             -DBUILD_STATIC_LIBS=OFF \
             -DBUILD_SHARED_LIBS=ON
 
@@ -154,6 +151,7 @@ jobs:
             -DOpenMP_omp_LIBRARY=${{ env.OPENMP_LIB }} \
             -DMUMPS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
             -DMETIS_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
+            -DKRYLOV_INCLUDE_DIR=${{github.workspace}}/dependencies/include \
             -DBQPD=${{github.workspace}}/dependencies/lib/libbqpd.a \
             -DMETIS_LIBRARY=${{github.workspace}}/dependencies/lib/libmetis.a \
             -DMUMPS_LIBRARY=${{github.workspace}}/dependencies/lib/libdmumps.a \
@@ -163,6 +161,7 @@ jobs:
             -DBLAS_LIBRARIES="${{github.workspace}}/dependencies/lib/libcblas.a;${{github.workspace}}/dependencies/lib/libblas.a" \
             -DLAPACK_LIBRARIES=${{github.workspace}}/dependencies/lib/liblapack.a \
             -DHIGHS=${{github.workspace}}/dependencies/lib/libhighs.a \
+            -DKRYLOV=${{github.workspace}}/dependencies/lib/libkrylov.dylib \
             -DBUILD_STATIC_LIBS=ON \
             -DBUILD_SHARED_LIBS=OFF
 
@@ -179,6 +178,7 @@ jobs:
             -DCMAKE_Fortran_COMPILER=gfortran \
             -DMUMPS_INCLUDE_DIR=${GITHUB_WORKSPACE}/dependencies/include \
             -DMETIS_INCLUDE_DIR=/mingw64/include \
+            -DKRYLOV_INCLUDE_DIR=${GITHUB_WORKSPACE}/dependencies/include \
             -DBQPD=${GITHUB_WORKSPACE}/dependencies/lib/libbqpd.a \
             -DMETIS_LIBRARY=/mingw64/lib/libmetis.a \
             -DMUMPS_LIBRARY=${GITHUB_WORKSPACE}/dependencies/lib/libdmumps.a \
@@ -188,6 +188,7 @@ jobs:
             -DBLAS_LIBRARIES="${GITHUB_WORKSPACE}/dependencies/lib/libcblas.a;${GITHUB_WORKSPACE}/dependencies/lib/libblas.a" \
             -DLAPACK_LIBRARIES=${GITHUB_WORKSPACE}/dependencies/lib/liblapack.a \
             -DHIGHS=${GITHUB_WORKSPACE}/dependencies/lib/libhighs.a \
+            -DKRYLOV=${GITHUB_WORKSPACE}/dependencies/bin/libkrylov.dll \
             -DBUILD_STATIC_LIBS=ON \
             -DBUILD_SHARED_LIBS=OFF
 
@@ -202,6 +203,12 @@ jobs:
       # TEST
       # =========================================================
 
+      - name: Set PATH (Windows)
+        if: matrix.toolchain == 'mingw'
+        shell: msys2 {0}
+        run: |
+          echo "PATH=${GITHUB_WORKSPACE}/dependencies/bin:$PATH" >> $GITHUB_ENV
+
       - name: Run tests
         working-directory: build
         run: ctest --output-on-failure -C ${{env.BUILD_TYPE}}
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1761a6668..2ee7be295 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -256,6 +256,26 @@ if(SPRAL)
    message(STATUS "Found SPRAL")
 endif()
 
+# Krylov
+find_library(KRYLOV krylov)
+if(KRYLOV)
+   target_link_libraries(uno_dependencies INTERFACE ${KRYLOV})
+   target_compile_definitions(uno_dependencies INTERFACE HAS_KRYLOV)
+
+   get_filename_component(KRYLOV_DIRECTORY ${KRYLOV} DIRECTORY)
+   # The bundle ships krylov.h in an 'include' folder sibling to the library
+   # directory (lib/ on Linux/macOS, bin/ on Windows).
+   find_path(KRYLOV_INCLUDE_DIR krylov.h
+             HINTS "${KRYLOV_DIRECTORY}/../include" "${KRYLOV_DIRECTORY}")
+   target_include_directories(uno_dependencies SYSTEM INTERFACE ${KRYLOV_INCLUDE_DIR})
+
+   if(ENABLE_TESTS)
+      target_sources(run_unotest PRIVATE unotest/functional_tests/KrylovSolversTests.cpp)
+   endif()
+
+   message(STATUS "Found Krylov")
+endif()
+
 # helper function: resolve a mixed list of -lflags and relative paths to absolute paths
 function(resolve_library_paths input_list output_list)
    set(result)
@@ -383,10 +403,73 @@ if(SKBUILD)
       target_compile_definitions(unopy PRIVATE PYBIND11_DETAILED_ERROR_MESSAGES)
    endif()
 
+   # The installed extension loads libkrylov from a 'lib' subdirectory of the
+   # package. Point a relative RPATH there so @rpath/libkrylov.dylib (macOS) /
+   # libkrylov.so (Linux) resolves to unopy/lib/ at runtime. Windows has no
+   # RPATH; unopy/__init__.py adds unopy/lib via os.add_dll_directory().
+   if(APPLE)
+      set_target_properties(unopy PROPERTIES INSTALL_RPATH "@loader_path/lib")
+   elseif(UNIX)
+      set_target_properties(unopy PROPERTIES INSTALL_RPATH "$ORIGIN/lib")
+   endif()
+
    install(TARGETS unopy
            LIBRARY DESTINATION unopy    # Linux/macOS: unopy/unopy.so
            RUNTIME DESTINATION unopy    # Windows: unopy/unopy.pyd
    )
+
+   # =========================================================================
+   # Bundle the Krylov + Julia runtime into the wheel, INTACT
+   # =========================================================================
+   # juliac emits a *relocatable tree* that the repair tools (delocate/auditwheel/
+   # delvewheel) cannot place correctly: libkrylov finds its Julia runtime through
+   # baked-in relative paths and runtime dlopen(), neither of which the repair
+   # tools follow. So we install the tree ourselves into unopy/lib on every
+   # platform; the difference is only the source layout.
+   #
+   # Unix (macOS/Linux): libkrylov carries rpaths assuming it lives in a directory
+   # named 'lib' with the public libjulia.* alongside it and the internal kernel in
+   # a 'julia/' sibling (@loader_path/../lib, @loader_path/../lib/julia; the $ORIGIN
+   # equivalents on Linux). We copy the whole lib/ tree verbatim so those resolve.
+   #
+   # Windows: juliac output is flat (libkrylov.dll and all Julia DLLs together in
+   # dependencies/bin, no rpath, no julia/ subdir). delvewheel can't vendor them
+   # (libkrylov isn't in the .pyd's traceable import graph, and Julia loads its
+   # kernel by dlopen), so we install the flat DLL set into unopy/lib and
+   # unopy/__init__.py adds that directory via os.add_dll_directory().
+   if(KRYLOV AND NOT WIN32)
+      get_filename_component(KRYLOV_ABS "${KRYLOV}" ABSOLUTE)
+      get_filename_component(KRYLOV_DIR "${KRYLOV_ABS}" DIRECTORY)
+
+      # Copy the ENTIRE dependency lib/ tree into unopy/lib, preserving structure:
+      #   lib/libkrylov.dylib        -> unopy/lib/libkrylov.dylib
+      #   lib/libjulia.*.dylib       -> unopy/lib/libjulia.*.dylib   (Julia public)
+      #   lib/julia/*.dylib          -> unopy/lib/julia/*.dylib      (Julia internal)
+      # This reproduces juliac's build-time layout exactly, so every one of
+      # libkrylov's baked-in rpaths resolves: @loader_path/../lib finds the public
+      # libjulia.*, @loader_path/../lib/julia finds the internal kernel. Installing
+      # only libkrylov + the julia/ subdir (as before) missed libjulia.*, which
+      # sits at the top of lib/, not inside lib/julia/.
+      #
+      # Static archives are excluded: they're linked into the extension at build
+      # time, not loaded at runtime, so they would only bloat the wheel.
+      install(DIRECTORY "${KRYLOV_DIR}/"
+              DESTINATION unopy/lib
+              USE_SOURCE_PERMISSIONS
+              PATTERN "*.a"   EXCLUDE
+              PATTERN "*.lib" EXCLUDE)
+   elseif(KRYLOV AND WIN32)
+      get_filename_component(KRYLOV_ABS "${KRYLOV}" ABSOLUTE)
+      get_filename_component(KRYLOV_DIR "${KRYLOV_ABS}" DIRECTORY)
+
+      # Flat layout: install every DLL sitting next to libkrylov.dll (the Julia
+      # kernel + Julia's own MinGW runtime + libkrylov itself) into unopy/lib.
+      # __init__.py puts unopy/lib on the DLL search path so the .pyd finds
+      # libkrylov and libkrylov's dlopen()s of the Julia kernel resolve.
+      install(DIRECTORY "${KRYLOV_DIR}/"
+              DESTINATION unopy/lib
+              FILES_MATCHING PATTERN "*.dll")
+   endif()
 endif()
 
 # ======================
diff --git a/dependencies/scripts/download_dependencies.sh b/dependencies/scripts/download_dependencies.sh
index 52a077fc7..4694fa1e6 100755
--- a/dependencies/scripts/download_dependencies.sh
+++ b/dependencies/scripts/download_dependencies.sh
@@ -5,24 +5,56 @@ set -e
 OS_NAME="$(uname -s)"
 case "$OS_NAME" in
     Linux*)
-      if [[ "$CIBW_BUILD" == *musllinux* ]] || ldd --version 2>&1 | grep -qi musl; then
-        OS="linux-musl"
+      if ldd --version 2>&1 | grep -qi musl; then
+        echo "Unsupported OS: linux-musl"
+        exit 1
       else
         OS="linux-gnu"
+        OS_KRYLOV="linux"
+        EXTENSION_KRYLOV="tar.gz"
       fi
       ;;
-    Darwin*) OS="apple-darwin";;
-    Windows*) OS="w64-mingw32";;
-    MINGW64_NT*) OS="w64-mingw32";;
-    MSYS_NT*) OS="w64-mingw32";;
-    *) echo "Unsupported OS: $OS_NAME"; exit 1;;
+    Darwin*)
+		OS="apple-darwin"
+		OS_KRYLOV="macos"
+		EXTENSION_KRYLOV="tar.gz"
+		;;
+    Windows*|MINGW64_NT*|MSYS_NT*)
+		OS="w64-mingw32"
+		OS_KRYLOV="windows"
+		EXTENSION_KRYLOV="zip"
+		;;
+    *)
+		echo "Unsupported OS: $OS_NAME"
+		exit 1
+		;;
 esac
 # detect architecture
 ARCH_NAME="$(uname -m)"
 case "$ARCH_NAME" in
-    x86_64|amd64) ARCH="x86_64";;
-    arm64|aarch64) ARCH="aarch64";;
-    *) echo "Unknown architecture '$ARCH_NAME'."; exit 1;;
+    x86_64|amd64)
+		ARCH="x86_64"
+		ARCH_KRYLOV="x86_64"
+		;;
+    arm64|aarch64)
+		ARCH="aarch64";
+		case "$OS_KRYLOV" in
+			linux*)
+				ARCH_KRYLOV="aarch64"
+				;;
+			macos*)
+				ARCH_KRYLOV="arm64"
+				;;
+			*)
+				echo "Unsupported aarch64 OS: $OS_KRYLOV"
+				exit 1
+				;;
+		esac
+		;;
+    *)
+		echo "Unknown architecture '$ARCH_NAME'."
+		exit 1
+		;;
 esac
 
 # change directory
@@ -48,6 +80,21 @@ curl -L -o UnoUtils.tar.gz "$ASSET_URL"
 tar -xzf UnoUtils.tar.gz
 pwd
 
+# download Krylov.jl
+VERSION="v0.10.8"
+REPO="https://github.com/JuliaSmoothOptimizers/Krylov.jl/releases/download/${VERSION}"
+ASSET_NAME="libkrylov-${OS_KRYLOV}-${ARCH_KRYLOV}.${EXTENSION_KRYLOV}"
+ASSET_URL="${REPO}/${ASSET_NAME}"
+echo "Downloading: ${ASSET_URL}"
+if [[ "$OS_KRYLOV" == "windows" ]]; then
+	curl -L -o libkrylov.zip "$ASSET_URL"
+	unzip libkrylov.zip
+else
+	curl -L -o libkrylov.tar.gz "$ASSET_URL"
+	tar -xzf libkrylov.tar.gz
+fi
+pwd
+
 # delete unwanted directories
 # rm -rf lib/cmake/cblas* lib/cmake/lapack* lib/pkgconfig
 rm -rf lib/cmake lib/pkgconfig
diff --git a/interfaces/Python/tests/run_wheel_tests.py b/interfaces/Python/tests/run_wheel_tests.py
new file mode 100644
index 000000000..a7830ff2e
--- /dev/null
+++ b/interfaces/Python/tests/run_wheel_tests.py
@@ -0,0 +1,12 @@
+# Copyright (c) 2026 Charlie Vanaret
+# Licensed under the MIT license. See LICENSE file in the project directory for details.
+
+import unopy
+
+# test libkrylov (raises on failure)
+unopy.test_libkrylov()
+
+# run the hs015 example
+import runpy, os
+here = os.path.dirname(__file__)
+runpy.run_path(os.path.join(here, "..", "example", "example_hs015.py"), run_name="__main__")
\ No newline at end of file
diff --git a/interfaces/Python/unopy.cpp b/interfaces/Python/unopy.cpp
index acacb1812..b43301e01 100644
--- a/interfaces/Python/unopy.cpp
+++ b/interfaces/Python/unopy.cpp
@@ -5,6 +5,7 @@
 #include <pybind11/stl.h>
 #include "unopy.hpp"
 #include "Uno.hpp"
+#include "ingredients/subproblem_solvers/Krylov/KrylovSolvers.hpp"
 
 namespace py = pybind11;
 
@@ -22,6 +23,9 @@ namespace uno {
       module.doc() = description;
 
       module.def("current_uno_version", &Uno::current_version);
+#ifdef HAS_KRYLOV
+      module.def("test_libkrylov", &test_krylov_solvers);
+#endif
 
       define_Model(module);
       define_Result(module);
diff --git a/interfaces/Python/unopy/__init__.py b/interfaces/Python/unopy/__init__.py
index 1033e3d01..84fb96cf9 100644
--- a/interfaces/Python/unopy/__init__.py
+++ b/interfaces/Python/unopy/__init__.py
@@ -1,14 +1,22 @@
 import os
 import sys
 
-# load bundled DLLs from unopy.libs
+# Bundled DLLs ship in two places:
+#   unopy/lib    - libkrylov + the Julia runtime (installed by CMake)
+#   unopy.libs   - libraries vendored by delvewheel (e.g. the Fortran runtime)
 basedir = os.path.dirname(__file__)
+libdir = os.path.join(basedir, 'lib')
 subdir = os.path.join(basedir, '..', 'unopy.libs')
-if os.name == 'nt' and os.path.isdir(subdir):
-    # Prepend to PATH so our DLLs are found before any system MinGW ones
-    os.environ['PATH'] = subdir + os.pathsep + os.environ.get('PATH', '')
-    os.add_dll_directory(subdir)
+
+if os.name == 'nt':
+    # Prepend to PATH so our DLLs win over any system MinGW ones. libdir is
+    # prepended last, so it lands first on PATH — Julia's libstdc++ should take
+    # precedence over the one delvewheel vendored from msys2.
+    for d in (subdir, libdir):
+        if os.path.isdir(d):
+            os.environ['PATH'] = d + os.pathsep + os.environ.get('PATH', '')
+            os.add_dll_directory(d)
 elif sys.platform == 'cygwin':
-    os.environ['PATH'] = os.pathsep.join((os.environ['PATH'], basedir, subdir))
+    os.environ['PATH'] = os.pathsep.join((os.environ['PATH'], basedir, libdir, subdir))
 
 from .unopy import *
\ No newline at end of file
diff --git a/pyproject.toml b/pyproject.toml
index 16da582d1..1805bf22e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -22,6 +22,7 @@ license = "MIT"
 dependencies = [
     "numpy",
 ]
+requires-python = ">=3.9"
 
 [project.urls]
 Repository = "https://github.com/cvanaret/Uno"
@@ -49,3 +50,6 @@ MUMPS_PORD_LIBRARY = "dependencies/lib/libpord.a"
 MUMPS_MPISEQ_LIBRARY = "dependencies/lib/libmpiseq.a"
 # HiGHS
 HIGHS = "dependencies/lib/libhighs.a"
+# Krylov.jl
+KRYLOV = "dependencies/lib/libkrylov.so"
+KRYLOV_INCLUDE_DIR = "dependencies/include"
\ No newline at end of file
diff --git a/uno/ingredients/subproblem_solvers/Krylov/KrylovSolvers.hpp b/uno/ingredients/subproblem_solvers/Krylov/KrylovSolvers.hpp
new file mode 100644
index 000000000..02427f905
--- /dev/null
+++ b/uno/ingredients/subproblem_solvers/Krylov/KrylovSolvers.hpp
@@ -0,0 +1,96 @@
+// Copyright (c) 2026 Charlie Vanaret
+// Licensed under the MIT license. See LICENSE file in the project directory for details.
+
+#ifndef UNO_KRYLOVSOLVERS_H
+#define UNO_KRYLOVSOLVERS_H
+
+#include <krylov.h>
+#include <cassert>
+#include <cmath>
+#include <iostream>
+
+static void test_krylov_solvers() {
+   /*
+   * basic_cg.c — minimal example: solve a 5x5 SPD system with CG.
+   * A = tridiag(-1, 2, -1),  b = [1, 0, 0, 0, 1]^T
+   * Expected output:
+   *   Solved: yes   niter: 3   time: ...
+   *   x = [ 1.00  1.00  1.00  1.00  1.00 ]
+   */
+
+   #define N 5
+
+   /* Tridiagonal matrix stored as three diagonals for simplicity. */
+   typedef struct {
+      int    n;
+      double diag[N];   /* main diagonal */
+      double off[N-1];  /* sub/super diagonal */
+   } TriDiag;
+
+   /* Matvec callback:  y = A * x  */
+   const auto matvec_A = [](const void *xv, void *yv, void *userdata) {
+      const double *x  = (const double *) xv;
+      double       *y  = (double *) yv;
+      const TriDiag *A = (const TriDiag *) userdata;
+      const int n = A->n;
+
+      for (int i = 0; i < n; i++) {
+         y[i] = A->diag[i] * x[i];
+         if (i > 0)   y[i] += A->off[i-1] * x[i-1];
+         if (i < n-1) y[i] += A->off[i]   * x[i+1];
+      }
+   };
+
+   /* Build A = tridiag(-1, 2, -1) */
+   TriDiag A;
+   A.n = N;
+   for (int i = 0; i < N;   i++) A.diag[i] = 2.0;
+   for (int i = 0; i < N-1; i++) A.off[i]  = -1.0;
+
+   /* Right-hand side */
+   double b[N] = {1.0, 0.0, 0.0, 0.0, 1.0};
+
+   /* Solution buffer */
+   double x[N];
+
+   /* -----------------------------------------------------------------------
+   * Create workspace for CG, double precision, CPU
+   * --------------------------------------------------------------------- */
+   void *ws = NULL;
+   int ret = krylov_workspace_create(KRYLOV_CG, N, N, KRYLOV_FLOAT64, KRYLOV_CPU,
+                                     NULL,   /* workspace options (NULL = defaults) */
+                                     &ws);
+   assert(ret == 0);
+
+   /* -----------------------------------------------------------------------
+   * Solve
+   * --------------------------------------------------------------------- */
+   KrylovOptions opts = krylov_default_options();
+   opts.atol = 1e-10;   /* absolute tolerance */
+   opts.rtol = 1e-10;   /* relative tolerance */
+   ret = krylov_solve(ws,
+                     matvec_A,   /* y = A*x */
+                     NULL,       /* y = Aᴴ*x  (CG doesn't need it) */
+                     NULL,       /* matvec_M: left/centered preconditioner (none) */
+                     NULL,       /* matvec_N: right preconditioner (none) */
+                     b,          /* right-hand side b (size m) */
+                     NULL,       /* c = NULL  (CG only needs one RHS) */
+                     &A,         /* userdata forwarded to matvec_A */
+                     &opts);     /* solver options (NULL = all defaults) */
+   assert(ret == 0);
+
+   /* -----------------------------------------------------------------------
+   * Retrieve results
+   * --------------------------------------------------------------------- */
+   ret = krylov_get_x(ws, x, N);
+   assert(ret == 0);
+
+   std::cout << "KrylovSolvers: CG solution (should be a vector of 1):";
+   for (int i = 0; i < N; i++) {
+      std::cout << ' ' << x[i];
+   }
+   std::cout << '\n';
+   krylov_workspace_free(ws);
+}
+
+#endif // UNO_KRYLOVSOLVERS_H
\ No newline at end of file
diff --git a/unotest/functional_tests/KrylovSolversTests.cpp b/unotest/functional_tests/KrylovSolversTests.cpp
new file mode 100644
index 000000000..0686fda1a
--- /dev/null
+++ b/unotest/functional_tests/KrylovSolversTests.cpp
@@ -0,0 +1,102 @@
+// Copyright (c) 2026 Charlie Vanaret
+// Licensed under the MIT license. See LICENSE file in the project directory for details.
+
+#include <gtest/gtest.h>
+#include "ingredients/subproblem_solvers/Krylov/KrylovSolvers.hpp"
+
+/*
+ * basic_cg.c — minimal example: solve a 5x5 SPD system with CG.
+ *
+ * A = tridiag(-1, 2, -1),  b = [1, 0, 0, 0, 1]^T
+ *
+ * Compile (after building libkrylov with CMake):
+ *
+ *   gcc -o basic_cg basic_cg.c -I../include -L../build -lkrylov -Wl,-rpath,../build
+ *
+ * Expected output:
+ *   Solved: yes   niter: 3   time: ...
+ *   x = [ 1.00  1.00  1.00  1.00  1.00 ]
+ */
+
+/* -------------------------------------------------------------------------
+ * Problem data
+ * ------------------------------------------------------------------------- */
+
+#define N 5
+
+/* Tridiagonal matrix stored as three diagonals for simplicity. */
+typedef struct {
+  int    n;
+  double diag[N];   /* main diagonal */
+  double off[N-1];  /* sub/super diagonal */
+} TriDiag;
+
+/* Matvec callback:  y = A * x  */
+static void matvec_A(const void *xv, void *yv, void *userdata) {
+  const double *x  = (const double *)xv;
+  double       *y  = (double *)yv;
+  const TriDiag *A = (const TriDiag *)userdata;
+  int n = A->n;
+
+  for (int i = 0; i < n; i++) {
+    y[i] = A->diag[i] * x[i];
+    if (i > 0)   y[i] += A->off[i-1] * x[i-1];
+    if (i < n-1) y[i] += A->off[i]   * x[i+1];
+  }
+}
+
+TEST(Krylov, Example) {
+  /* Build A = tridiag(-1, 2, -1) */
+  TriDiag A;
+  A.n = N;
+  for (int i = 0; i < N;   i++) A.diag[i] = 2.0;
+  for (int i = 0; i < N-1; i++) A.off[i]  = -1.0;
+
+  /* Right-hand side */
+  double b[N] = {1.0, 0.0, 0.0, 0.0, 1.0};
+
+  /* Solution buffer */
+  double x[N];
+
+  /* -----------------------------------------------------------------------
+   * Create workspace for CG, double precision, CPU
+   * --------------------------------------------------------------------- */
+  void *ws = NULL;
+  int ret = krylov_workspace_create(KRYLOV_CG, N, N, KRYLOV_FLOAT64, KRYLOV_CPU,
+                                    NULL,   /* workspace options (NULL = defaults) */
+                                    &ws);
+  ASSERT_EQ(ret, 0);
+
+  /* -----------------------------------------------------------------------
+   * Solve
+   * --------------------------------------------------------------------- */
+  KrylovOptions opts = krylov_default_options();
+  opts.atol = 1e-10;   /* absolute tolerance */
+  opts.rtol = 1e-10;   /* relative tolerance */
+  ret = krylov_solve(ws,
+                     matvec_A,   /* y = A*x */
+                     NULL,       /* y = Aᴴ*x  (CG doesn't need it) */
+                     NULL,       /* matvec_M: left/centered preconditioner (none) */
+                     NULL,       /* matvec_N: right preconditioner (none) */
+                     b,          /* right-hand side b (size m) */
+                     NULL,       /* c = NULL  (CG only needs one RHS) */
+                     &A,         /* userdata forwarded to matvec_A */
+                     &opts);     /* solver options (NULL = all defaults) */
+  ASSERT_EQ(ret, 0);
+
+  /* -----------------------------------------------------------------------
+   * Retrieve results
+   * --------------------------------------------------------------------- */
+  ret = krylov_get_x(ws, x, N);
+  ASSERT_EQ(ret, 0);
+
+  const double tolerance = 1e-8;
+  for (int i = 0; i < N; i++) {
+    EXPECT_NEAR(x[i], 1., tolerance);
+  }
+
+  /* -----------------------------------------------------------------------
+   * Free workspace
+   * --------------------------------------------------------------------- */
+  krylov_workspace_free(ws);
+}
\ No newline at end of file