diff --git a/.github/workflows/clang_format.yml b/.github/workflows/clang_format.yml
index 9654a89..f46327c 100644
--- a/.github/workflows/clang_format.yml
+++ b/.github/workflows/clang_format.yml
@@ -17,19 +17,12 @@ permissions:
 jobs:
   clang-format:
     name: Enforce clang-format
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-slim
     env:
-      CLANG_MAJOR_VERSION: 17
+      CLANG_MAJOR_VERSION: 20
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8  # v5.0.0
 
-      - name: Add Clang/LLVM repositories
-        run: |-
-          set -x
-          source /etc/os-release
-          wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-          sudo add-apt-repository "deb http://apt.llvm.org/${UBUNTU_CODENAME}/ llvm-toolchain-${UBUNTU_CODENAME}-${CLANG_MAJOR_VERSION} main"
-
       - name: Install clang-format
         run: |-
           set -x
diff --git a/.github/workflows/codespell.yml b/.github/workflows/codespell.yml
index d39d9fe..083c157 100644
--- a/.github/workflows/codespell.yml
+++ b/.github/workflows/codespell.yml
@@ -17,11 +17,11 @@ permissions:
 jobs:
   codespell:
     name: Enforce codespell-clean spelling
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8  # v5.0.0
 
-      - uses: codespell-project/actions-codespell@8f01853be192eb0f849a5c7d721450e7a467c579  # v2.2
+      - uses: codespell-project/actions-codespell@e3258cca84ce02b0bb36a3d41f2c18f719a0cc1a  # v2.4.3
         with:
           # "nd" (with lowercase "n") is from ".Nd" (with uppercase "n") in ttyplot.1
           # https://github.com/codespell-project/codespell/issues/3233#issuecomment-1828026522
diff --git a/.github/workflows/linux_and_macos.yml b/.github/workflows/linux_and_macos.yml
index e3923ee..a86c3fe 100644
--- a/.github/workflows/linux_and_macos.yml
+++ b/.github/workflows/linux_and_macos.yml
@@ -26,52 +26,40 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - cc: gcc-14
+          - cc: gcc-11
             clang_major_version: null
-            clang_repo_suffix: null
             make: make
-            runs-on: ubuntu-24.04
-          - cc: clang-18
-            clang_major_version: 18
-            clang_repo_suffix: -18
-            make: bmake
             runs-on: ubuntu-22.04
-          - cc: musl-gcc
+          - cc: musl-gcc  # based on gcc-13
             clang_major_version: null
-            clang_repo_suffix: null
             make: bmake
-            runs-on: ubuntu-22.04
-          - cc: gcc-13
-            clang_major_version: null
-            clang_repo_suffix: null
+            runs-on: ubuntu-24.04
+          - cc: clang-22
+            clang_major_version: 22
+            make: remake
+            runs-on: ubuntu-26.04
+            experimental: true  # preview OS (see continue-on-error above)
+          - cc: clang-18
+            clang_major_version: 18
             make: make
-            runs-on: macos-14
+            runs-on: macos-15
           - cc: gcc-15
             clang_major_version: null
-            clang_repo_suffix: null
             make: bmake
-            runs-on: macos-15-intel
+            runs-on: macos-26-intel
           - cc: clang-20
             clang_major_version: 20
-            clang_repo_suffix: null
-            make: bsdmake
-            runs-on: macos-26
-            experimental: true  # preview OS; UI test renders blank (see continue-on-error above)
+            make: remake
+            runs-on: xcode-27
+            experimental: true  # preview OS (see continue-on-error above)
     steps:
-      - name: Add Clang/LLVM repositories
-        if: "${{ runner.os == 'Linux' && contains(matrix.cc, 'clang') }}"
-        run: |-
-          set -x
-          source /etc/os-release
-          wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-          sudo add-apt-repository "deb http://apt.llvm.org/${UBUNTU_CODENAME}/ llvm-toolchain-${UBUNTU_CODENAME}${{ matrix.clang_repo_suffix }} main"
-
       - name: Install build dependencies
         if: "${{ runner.os == 'Linux' }}"
         run: |-
           sudo apt-get update
           sudo apt-get install --yes --no-install-recommends \
             bmake \
+            remake \
             libncurses-dev \
             musl-tools \
             pkg-config
@@ -81,16 +69,9 @@ jobs:
         run: |-
           brew install \
             bmake \
-            bsdmake \
+            remake \
             coreutils
 
-      - name: Install build dependency Clang ${{ matrix.clang_major_version }}
-        if: "${{ runner.os == 'Linux' && contains(matrix.cc, 'clang') }}"
-        run: |-
-          sudo apt-get install --yes --no-install-recommends -V \
-              clang-${{ matrix.clang_major_version }} \
-              libclang-rt-${{ matrix.clang_major_version }}-dev
-
       - name: Add versioned aliases for Clang ${{ matrix.clang_major_version }}
         if: "${{ runner.os == 'macOS' && contains(matrix.cc, 'clang') }}"
         run: |-
@@ -157,7 +138,7 @@ jobs:
           fi
 
           # musl-gcc and compilers on macOS do not seem to support linking with sanitizers
-          if [[ ${{ matrix.cc }} =~ musl || ${{ matrix.runs-on }} =~ macos ]]; then
+          if [[ ${{ matrix.cc }} =~ musl || ${{ matrix.runs-on }} =~ macos|xcode ]]; then
             sanitizer=
           else
             # ASan: https://clang.llvm.org/docs/AddressSanitizer.html