diff --git a/.github/workflows/unit-tests.yml b/.github/workflows/unit-tests.yml
new file mode 100644
index 0000000..b7f7371
--- /dev/null
+++ b/.github/workflows/unit-tests.yml
@@ -0,0 +1,143 @@
+# Copyright (C) 2005 - 2026 Settlers Freaks <sf-team at siedler25.org>
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+name: Unit tests
+
+on:
+  push:
+    branches:
+      - master
+      - develop
+      - bugfix/**
+      - feature/**
+      - fix/**
+      - github/**
+      - pr/**
+  pull_request:
+
+concurrency:
+  group: ${{format('tests-{0}:{1}', github.repository, github.ref)}}
+  cancel-in-progress: true
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  StyleAndFormatting:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - run: curl -sSL --retry 5 --connect-timeout 15 https://github.com/Return-To-The-Roots/s25client/raw/refs/heads/master/.clang-format --output .clang-format
+      - name: Validation
+        run: tools/ci/staticValidation.sh "$GITHUB_WORKSPACE"
+      - name: Formatting
+        uses: DoozyX/clang-format-lint-action@bcb4eb2cb0d707ee4f3e5cc3b456eb075f12cf73 # v0.20
+        with:
+          source: "libs tests"
+          clangFormatVersion: 10
+      - name: Lint markdown files
+        uses: avto-dev/markdown-lint@04d43ee9191307b50935a753da3b775ab695eceb # v1.5.0
+        with:
+          args: .
+      - name: Check licensing
+        run:
+          pip install --user reuse
+          reuse lint
+  UnitTests:
+    strategy:
+      matrix:
+        include:
+          - { compiler: gcc-9,       os: ubuntu-22.04,         buildType: Debug,   boostVersion: 1.73.0 } # Older ones fail due to PTHREAD_STACK_MIN use in Boost.Thread
+          - { compiler: clang,       os: macos-26,             buildType: Debug,   boostVersion: 1.81.0 } # New libc++ only supported since 1.81
+          # Latest GCC
+          - { compiler: gcc-14,      os: ubuntu-24.04,         buildType: Debug,   boostVersion: 1.87.0 }
+          # Latest Clang
+          - { compiler: clang-19,    os: ubuntu-24.04,         buildType: Debug,   boostVersion: 1.81.0 }
+          # Windows
+          - { compiler: msvc-14.3,   os: windows-2022,         buildType: Debug,   boostVersion: 1.87.0, generator: 'Visual Studio 17 2022' }
+          - { compiler: msvc-14.5,   os: windows-2025-vs2026,  buildType: Debug,   boostVersion: 1.91.0, generator: 'Visual Studio 18 2026' }
+          - { compiler: gcc, sys: MINGW64, os: windows-latest, buildType: Debug,   boostVersion: 1.91.0, generator: 'Ninja' }
+
+    runs-on: ${{matrix.os}}
+    defaults:
+      run:
+        shell: ${{matrix.sys && 'msys2 {0}' || 'bash'}}
+    steps:
+      - name: Setup MSYS2 environment for MinGW
+        if: matrix.sys
+        uses: msys2/setup-msys2@ec48f7c5447b3140e2b088413ae3a55687bccb6e # v2.33.0
+        with:
+          msystem: ${{matrix.sys}}
+          update: true
+          install: git python
+          pacboy: gcc:p cmake:p ninja:p miniupnpc:p
+
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Install system packages (Linux)
+        if: runner.os == 'Linux'
+        run: |
+          pkgs=${{matrix.compiler}}
+          pkgs=${pkgs/gcc-/g++-}
+          sudo apt install ccache libminiupnpc-dev $pkgs
+      - name: Install system packages (OSX)
+        if: runner.os == 'macOS'
+        run: brew install ccache cmake miniupnpc
+      - name: Install system packages (Windows)
+        if: runner.os == 'Windows' && ! matrix.sys
+        run: choco install wget
+
+      - name: Setup compiler
+        if: "!startsWith(matrix.compiler, 'msvc')"
+        run: tools/ci/setupCompiler.sh
+        env:
+          COMPILER: ${{matrix.compiler}}
+
+      - name: Setup cmake
+        if: runner.os != 'Windows'
+        uses: jwlawson/actions-setup-cmake@0d6a7d60b009d01c9e7523be22153ff8f19460d3  # v2.2.0
+        with:
+          cmake-version: '3.20.x'
+
+      - name: Setup CCache
+        if: runner.os != 'Windows'
+        uses: hendrikmuhs/ccache-action@d62db5f07c26379fc4b4e0916f098a92573c3b03  # v1.2.23
+        with:
+          key: ${{matrix.os}}-${{matrix.compiler}}-${{matrix.buildType}}-${{matrix.boostVersion}}
+          max-size: 200M
+
+      - run: echo "BOOST_ROOT=${{runner.temp}}/boost${{matrix.boostVersion}}" >> $GITHUB_ENV
+      - name: Cache Boost installation
+        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+        with:
+          path: ${{env.BOOST_ROOT}}
+          key: ${{matrix.os}}-${{matrix.compiler}}-${{matrix.boostVersion}}-${{matrix.buildType}}
+
+      - name: Install Boost
+        env:
+          BOOST_VERSION: ${{matrix.boostVersion}}
+          TOOLSET: ${{matrix.compiler}}
+          VARIANT: ${{matrix.buildType}}
+        run: |
+          echo "ADDITIONAL_CMAKE_FLAGS=-DBoost_NO_SYSTEM_PATHS=ON" >> $GITHUB_ENV
+          LINK=""
+          if [[ "$RUNNER_OS" == "Windows" ]]; then
+            LINK=static
+          else
+            LINK=shared
+          fi
+          tools/ci/installBoost.sh "${BOOST_VERSION}" "${BOOST_ROOT}" "filesystem,locale,test" $LINK
+
+      - name: Checkout libendian
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          repository: Return-To-The-Roots/libendian
+          ref: master
+          path: ${{github.workspace}}/libendian
+      - name: Build
+        run: tools/ci/build.sh "${{matrix.buildType}}" "${ADDITIONAL_CMAKE_FLAGS}" "tests"
+        env:
+          GENERATOR: ${{matrix.generator}}
+          LIBENDIAN_DIR: ${{github.workspace}}/libendian
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8512d04..12c621a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,6 +7,21 @@ project(s25util)
 
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
 
+if(PROJECT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
+    set(isTopLevel TRUE)
+    find_path(RTTR_LIBENDIAN_DIR NAMES "include/libendian" HINTS ${CMAKE_CURRENT_SOURCE_DIR}/../libendian PATHS ENV LIBENDIAN_DIR PATH_SUFFIXES ".." libendian)
+    if(NOT RTTR_LIBENDIAN_DIR)
+        message(FATAL_ERROR "Path to libendian not found! You can set the full path in the env var LIBENDIAN_DIR ($ENV{LIBENDIAN_DIR})")
+    endif()
+    add_subdirectory(${RTTR_LIBENDIAN_DIR} libendian)
+    include(EnableCCache)
+    include(RttrBoostCfg)
+    # Boost 1.73 contains Boost.Nowide, 1.74 a required fix
+    find_package(Boost 1.74 COMPONENTS nowide)
+else()
+    set(isTopLevel FALSE)
+endif()
+
 # The super project might e.g. call find_package(Boost ... nowide), if the target is not defined, download directly
 if(NOT TARGET Boost::nowide)
     message(STATUS "Fetching Boost.Nowide from repository...")
diff --git a/appveyor.yml b/appveyor.yml
new file mode 100644
index 0000000..c2760d2
--- /dev/null
+++ b/appveyor.yml
@@ -0,0 +1,38 @@
+# Copyright (C) 2005 - 2026 Settlers Freaks <sf-team at siedler25.org>
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+version: 1.0.{build}
+
+shallow_clone: true
+
+branches:
+  only: [master]
+  
+image: Visual Studio 2019
+
+configuration:
+  - Debug
+  - Release
+  
+platform: x64
+    
+environment:
+  global:
+    BOOST_DIR: 'C:\Libraries\boost_1_85_0'
+    RTTR_DISABLE_ASSERT_BREAKPOINT: 1
+
+install:
+  - git clone https://github.com/Return-To-The-Roots/libendian.git libendian
+  - set CMAKE_PREFIX_PATH=%CMAKE_PREFIX_PATH%;%cd%\libendian
+
+before_build:
+  - mkdir build
+  - cd build
+  - dir /a:d %BOOST_DIR%
+  - cmake -G "Visual Studio 16 2019" -A %platform% -DRTTR_ENABLE_WERROR=ON -DBOOST_ROOT="%BOOST_DIR%\lib64-msvc-14.2\cmake" -DBoost_VERBOSE=ON ..
+    
+build_script: cmake --build . --config %configuration% --parallel 4
+
+test_script: ctest --output-on-failure -C %configuration% --parallel 4
+
diff --git a/cmake/AddTestcase.cmake b/cmake/AddTestcase.cmake
index 352b471..63306a1 100644
--- a/cmake/AddTestcase.cmake
+++ b/cmake/AddTestcase.cmake
@@ -1,4 +1,4 @@
-# Copyright (C) 2005 - 2021 Settlers Freaks <sf-team at siedler25.org>
+# Copyright (C) 2005 - 2026 Settlers Freaks <sf-team at siedler25.org>
 #
 # SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -56,4 +56,8 @@ function(add_testcase)
         )
         set_tests_properties(${name} PROPERTIES ENVIRONMENT "${options}")
     endif()
+    if(NOT TARGET tests)
+        add_custom_target(tests)
+    endif()
+    add_dependencies(tests ${name})
 endfunction()
diff --git a/cmake/RttrBoostCfg.cmake b/cmake/RttrBoostCfg.cmake
index 3b2fed5..f427acb 100644
--- a/cmake/RttrBoostCfg.cmake
+++ b/cmake/RttrBoostCfg.cmake
@@ -7,7 +7,7 @@
 # Show message about boost config
 
 # Default boost libs are static on self-build windows versions and dynamic in the linux package repos
-if(WIN32 AND NOT MINGW)
+if(WIN32)
 	set(RTTR_USE_STATIC_BOOST_DEFAULT ON)
 else()
 	set(RTTR_USE_STATIC_BOOST_DEFAULT OFF)
diff --git a/libs/common/include/s25util/span.hpp b/libs/common/include/s25util/span.hpp
index be99ed2..891191c 100644
--- a/libs/common/include/s25util/span.hpp
+++ b/libs/common/include/s25util/span.hpp
@@ -214,19 +214,19 @@ class span
     constexpr span() noexcept : s_(0, 0)
     {}
 
-    template<class I, std::enable_if_t<E == dynamic_extent && detail::span_convertible_v<I, T>, int> = 0>
+    template<class I, std::enable_if_t<detail::span_convertible_v<I, T> && E == dynamic_extent, int> = 0>
     constexpr span(I* f, size_type c) : s_(f, c)
     {}
 
-    template<class I, std::enable_if_t<E != dynamic_extent && detail::span_convertible_v<I, T>, int> = 0>
+    template<class I, std::enable_if_t<detail::span_convertible_v<I, T> && E != dynamic_extent, int> = 0>
     explicit constexpr span(I* f, size_type c) : s_(f, c)
     {}
 
-    template<class I, class L, std::enable_if_t<E == dynamic_extent && detail::span_convertible_v<I, T>, int> = 0>
+    template<class I, class L, std::enable_if_t<detail::span_convertible_v<I, T> && E == dynamic_extent, int> = 0>
     constexpr span(I* f, L* l) : s_(f, l - f)
     {}
 
-    template<class I, class L, std::enable_if_t<E != dynamic_extent && detail::span_convertible_v<I, T>, int> = 0>
+    template<class I, class L, std::enable_if_t<detail::span_convertible_v<I, T> && E != dynamic_extent, int> = 0>
     explicit constexpr span(I* f, L* l) : s_(f, l - f)
     {}
 
@@ -242,11 +242,11 @@ class span
     constexpr span(const std::array<U, N>& a) noexcept : s_(a.data(), N)
     {}
 
-    template<class R, std::enable_if_t<E == dynamic_extent && detail::span_is_range_v<R, T>, int> = 0>
+    template<class R, std::enable_if_t<detail::span_is_range_v<R, T> && E == dynamic_extent, int> = 0>
     constexpr span(R&& r) noexcept(noexcept(std::data(r)) && noexcept(r.size())) : s_(std::data(r), r.size())
     {}
 
-    template<class R, std::enable_if_t<E != dynamic_extent && detail::span_is_range_v<R, T>, int> = 0>
+    template<class R, std::enable_if_t<detail::span_is_range_v<R, T> && E != dynamic_extent, int> = 0>
     explicit constexpr span(R&& r) noexcept(noexcept(std::data(r)) && noexcept(r.size())) : s_(std::data(r), r.size())
     {}
 
diff --git a/tools/ci/build.sh b/tools/ci/build.sh
new file mode 100755
index 0000000..1bbfa2d
--- /dev/null
+++ b/tools/ci/build.sh
@@ -0,0 +1,71 @@
+#!/bin/bash
+
+# Copyright (C) 2005 - 2026 Settlers Freaks <sf-team at siedler25.org>
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+set -euo pipefail
+
+function print_on_gha {
+    [[ "${GITHUB_ACTIONS:-false}" != "true" ]] || echo "$@"
+}
+function startGroup {
+	print_on_gha "::group::$1"
+}
+function endGroup {
+	print_on_gha "::endgroup::"
+}
+
+# Required by the tests
+export USER="${USER:-TestUser}"
+
+BUILD_TYPE="${1}"
+CMAKE_FLAGS="${2}"
+TARGET="${3:-install}"
+
+[[ -d build ]] || mkdir build
+cd build
+
+if [[ -z ${GENERATOR:-} ]]; then
+    if [[ "${RUNNER_OS:-}" == "Linux" ]] || [[ "${RUNNER_OS:-}" == "macOS" ]]; then
+        GENERATOR="Unix Makefiles"
+    else
+      echo 'Missing $GENERATOR!'
+      exit 1
+    fi
+fi
+if [[ $GENERATOR == "Visual Studio"* ]]; then
+    BUILD_FLAGS=""
+else
+    BUILD_FLAGS="-j3"
+fi
+
+cmake --version
+
+set -x
+# shellcheck disable=SC2086
+cmake \
+    -G "$GENERATOR" \
+    -DCMAKE_BUILD_TYPE="${BUILD_TYPE}" \
+    -DRTTR_ENABLE_WERROR=ON \
+    -DCMAKE_INSTALL_PREFIX="$PWD/installed" \
+    ${CMAKE_FLAGS} \
+    ..
+
+cmake --build . --target "$TARGET" --config "${BUILD_TYPE}" -- $BUILD_FLAGS
+
+# Execute tests
+export RTTR_DISABLE_ASSERT_BREAKPOINT=1
+export BOOST_TEST_LOG_LEVEL=message
+export BOOST_TEST_REPORT_LEVEL=detailed
+if ! ctest --output-on-failure -C "${BUILD_TYPE}" -j2; then
+    startGroup "CMake cache"
+    cat CMakeCache.txt
+    endGroup
+    echo "LD:${LD_LIBRARY_PATH:-}"
+    echo "DYLD:${DYLD_LIBRARY_PATH:-}"
+    echo "PATH:$PATH"
+    startGroup "Rerun failed tests only"
+    ctest --output-on-failure -C "${BUILD_TYPE}" --rerun-failed --extra-verbose
+    endGroup
+fi
diff --git a/tools/ci/checkUTF8.sh b/tools/ci/checkUTF8.sh
new file mode 100755
index 0000000..4c9b02d
--- /dev/null
+++ b/tools/ci/checkUTF8.sh
@@ -0,0 +1,22 @@
+#!/bin/bash
+#
+# Copyright (C) 2005 - 2026 Settlers Freaks <sf-team at siedler25.org>
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# Check that all source files in the current folder are valid UTF-8.
+# Prints the filenames of files that are not valid UTF-8 to stderr.
+# Exits 0 if all files are valid UTF-8, 1 otherwise.
+
+set -euo pipefail
+
+failed=0
+while IFS= read -r -d '' file; do
+    # Try to convert all source files from UTF-8 to detect encoding errors
+    if ! iconv -f UTF-8 "$file" > /dev/null; then
+        printf '%s\n' "$file" >&2
+        failed=1
+    fi
+done < <(find . --exclude-dir=.git -type f \( -name '*.cpp' -o -name '*.hpp' -o -name '*.tpp' -o -name '*.h' \) -print0)
+
+exit "$failed"
diff --git a/tools/ci/installBoost.sh b/tools/ci/installBoost.sh
index f9dc52b..15f7dea 100755
--- a/tools/ci/installBoost.sh
+++ b/tools/ci/installBoost.sh
@@ -11,6 +11,7 @@ INSTALL_DIR="${2:?Missing install dir}"
 required_libs="${3:?Missing libs}"
 link="${4:-static}"
 
+# shellcheck disable=SC2206
 required_libs=( ${required_libs//,/ } )
 
 function print_on_gha {
@@ -46,15 +47,14 @@ if all_libs_exist; then
 fi
 
 BUILD_DIR=/tmp/boost
-BUILD_LOG=/tmp/boost.log
 
 mkdir -p "${BUILD_DIR}" && cd "${BUILD_DIR}"
 
 startGroup "Download Boost"
 FILE_NAME="boost_${VERSION//./_}"
-URL="https://archives.boost.io/release/${VERSION}/source/${FILE_NAME}.tar.bz2"
+URL="https://archives.boost.io/release/${VERSION}/source/${FILE_NAME}.tar.gz"
 echo "Downloading and extracting file from $URL..."
-wget "${URL}" -qO- | tar jx
+wget "${URL}" -qO- | tar zx
 if [ ! -f "${FILE_NAME}/bootstrap.sh" ]; then
     echo "Download failed or files invalid" >&2
 	endGroup
@@ -67,13 +67,14 @@ endGroup
 
 if [[ "${TRAVIS_OS_NAME:-}" == "windows" ]] || [[ "${RUNNER_OS:-}" == "Windows" ]]; then
     NPROC=3
-    : "${TOOLSET:=toolset=msvc}"
+    : "${TOOLSET:=msvc}"
     : "${VARIANT:=debug,release}"
 else
     # Linux and OSX version
     NPROC=$(nproc 2>/dev/null || sysctl -n hw.ncpu)
     : "${VARIANT:=release}"
 fi
+VARIANT=$(printf '%s' "$VARIANT" | tr '[:upper:]' '[:lower:]')
 
 libraries=$(join , "${required_libs[@]}")
 
@@ -84,7 +85,9 @@ endGroup
 
 startGroup "Building $link Boost in $VARIANT mode"
 echo "Installing ${libraries}, variants ${VARIANT} to ${INSTALL_DIR} using ${TOOLSET:-default toolset}"
-./b2 link="${link}" ${TOOLSET:-} variant="${VARIANT}" --prefix="${INSTALL_DIR}" -j${NPROC} install
+set -x
+# shellcheck disable=SC2086
+./b2 address-model=64 link="${link}" ${TOOLSET+toolset=$TOOLSET} variant="${VARIANT}" --prefix="${INSTALL_DIR}" -j${NPROC} install
 endGroup
 
 echo "Boost build finished successfully"
diff --git a/tools/ci/setupCompiler.sh b/tools/ci/setupCompiler.sh
new file mode 100755
index 0000000..54b3040
--- /dev/null
+++ b/tools/ci/setupCompiler.sh
@@ -0,0 +1,26 @@
+#!/bin/bash
+
+# Copyright (C) 2005 - 2026 Settlers Freaks <sf-team at siedler25.org>
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+set -euo pipefail
+
+CC="$COMPILER"
+
+if [[ "$CC" =~ clang ]]; then
+  CXX=${CC/clang/clang++}
+elif [[ "$CC" =~ gcc ]]; then
+  CXX=${CC/gcc/g++}
+else
+  echo "Unknown compiler: $CC"
+  exit 1
+fi
+ver=7 # default
+if [[ "$CC" =~ gcc- ]]; then
+  ver="${CC##*gcc-}"
+fi
+GCOV=gcov-${ver}
+echo "CC=$CC" >> $GITHUB_ENV
+echo "CXX=$CXX" >> $GITHUB_ENV
+echo "GCOV=$GCOV" >> $GITHUB_ENV
diff --git a/tools/ci/staticValidation.sh b/tools/ci/staticValidation.sh
new file mode 100755
index 0000000..0bc07c8
--- /dev/null
+++ b/tools/ci/staticValidation.sh
@@ -0,0 +1,24 @@
+#!/bin/bash
+
+# Copyright (C) 2005 - 2026 Settlers Freaks <sf-team at siedler25.org>
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+set -euo pipefail
+
+SRC_DIR="${1:?SRC_DIR missing}"
+scriptPath=$(dirname "$(readlink -f "$0")")
+
+cd "${SRC_DIR}"
+
+if ! "$scriptPath/checkUTF8.sh"; then
+  echo "Some files are not in UTF8 encoding (see filenames above)"
+  exit 1
+fi
+
+canonicalBugs="$(grep -r -l --include '*.h' --include '*.cpp' --include '*.hpp' --include '*.tpp' "::canonical(" || true)"
+if [[ "${canonicalBugs}" != "" ]]; then
+  echo "Following files use buggy boost::filesystem::canonical: ${canonicalBugs}"
+  echo "If this is only used on non-windows use canonical unqualified: using bfs::canonical; canonical(...)"
+  exit 1
+fi