diff --git a/.clang-tidy b/.clang-tidy
index 376c3848..752ae48f 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -38,6 +38,7 @@ Checks: >
         -modernize-use-override,
         -modernize-use-trailing-return-type,
         -modernize-use-using,
+        -readability-avoid-nested-conditional-operator,
         -readability-braces-around-statements,
         -readability-function-cognitive-complexity,
         -readability-function-size,
@@ -45,9 +46,11 @@ Checks: >
         -readability-identifier-length,
         -readability-isolate-declaration,
         -readability-magic-numbers,
+        -readability-redundant-inline-specifier,
         -readability-simplify-boolean-expr,
         -readability-uppercase-literal-suffix,
         -performance-avoid-endl,
+        -performance-enum-size,
         -performance-inefficient-string-concatenation,
         -performance-no-automatic-move,
         -performance-noexcept-move-constructor
diff --git a/.github/workflows/CI-unixish.yml b/.github/workflows/CI-unixish.yml
index 2acd8d93..ea6ed37b 100644
--- a/.github/workflows/CI-unixish.yml
+++ b/.github/workflows/CI-unixish.yml
@@ -63,6 +63,7 @@ jobs:
         make clean
         make -j$(nproc) test selfcheck CXXFLAGS="-g3 -D_GLIBCXX_DEBUG"
 
+    # TODO: change it to -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_DEBUG when the compiler is at least Clang 18
     - name: Run with libc++ debug mode
       if: matrix.os == 'ubuntu-22.04' && matrix.compiler == 'clang++'
       run: |
diff --git a/.github/workflows/clang-tidy.yml b/.github/workflows/clang-tidy.yml
index 4fb98b0f..a57f874b 100644
--- a/.github/workflows/clang-tidy.yml
+++ b/.github/workflows/clang-tidy.yml
@@ -21,19 +21,19 @@ jobs:
         run: |
           wget https://apt.llvm.org/llvm.sh
           chmod +x llvm.sh
-          sudo ./llvm.sh 17
-          sudo apt-get install clang-tidy-17
+          sudo ./llvm.sh 18
+          sudo apt-get install clang-tidy-18
 
       - name: Verify clang-tidy configuration
         run: |
-          clang-tidy-17 --verify-config
+          clang-tidy-18 --verify-config
 
       - name: Prepare CMake
         run: |
           cmake -S . -B cmake.output -G "Unix Makefiles" -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DDISABLE_CPP03_SYNTAX_CHECK=ON
         env:
-          CXX: clang-17
+          CXX: clang-18
 
       - name: Clang-Tidy
         run: |
-          run-clang-tidy-17 -q -j $(nproc) -p=cmake.output
+          run-clang-tidy-18 -q -j $(nproc) -p=cmake.output
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5954ac87..30ee1431 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -28,6 +28,8 @@ elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     add_compile_options(-Wno-multichar -Wno-four-char-constants)
     # ignore C++11-specific warning
     add_compile_options(-Wno-suggest-override -Wno-suggest-destructor-override)
+    # contradicts -Wcovered-switch-default
+    add_compile_options(-Wno-switch-default)
     # TODO: fix these?
     add_compile_options(-Wno-padded -Wno-sign-conversion -Wno-implicit-int-conversion -Wno-shorten-64-to-32 -Wno-shadow-field-in-constructor)