diff --git a/.github/workflows/mhs.yaml b/.github/workflows/mhs.yaml
new file mode 100644
index 0000000..5eac2cd
--- /dev/null
+++ b/.github/workflows/mhs.yaml
@@ -0,0 +1,62 @@
+name: mhs-ci
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+jobs:
+  build-mhs-os-string:
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      fail-fast: false
+      matrix:
+        # windows doesn't quite work yet
+        os: [ubuntu-latest, macOS-15-intel, macOS-latest]
+        mhs: [0.15.0.0]
+
+    steps:
+
+    - name: checkout mhs repo
+      uses: actions/checkout@v4
+      with:
+        repository: augustss/MicroHs
+        ref: v${{ matrix.mhs }}
+        path: mhs
+
+    - name: make and install mhs
+      if: runner.os == 'Windows'
+      run: |
+        cd mhs
+        nmake /F Makefile.windows
+
+    - name: make and install mhs
+      if: runner.os != 'Windows'
+      run: |
+        cd mhs
+        make minstall
+
+    - name: install packages
+      run: |
+        cd mhs
+        export PATH="$HOME/.mcabal/bin:$PATH"
+        make -f Makefile.packages
+      shell: bash
+
+    - name: checkout os-string repo
+      uses: actions/checkout@v4
+      with:
+        path: os-string
+
+    - name: compile and install os-string package
+      run: |
+        export PATH="$HOME/.mcabal/bin:$PATH"
+        cd os-string
+        mcabal -r install
+
+    - name: cleanup
+      run: |
+        rm -rf "$HOME/.mcabal"
+
diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 8e8fb2f..88d4b41 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -13,15 +13,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macOS-13, windows-latest]
-        ghc: ['9.4', '9.6', '9.8', '9.10', '9.12']
-        include:
-          - os: ubuntu-latest
-            ghc: '8.10'
-          - os: ubuntu-latest
-            ghc: '9.0'
-          - os: ubuntu-latest
-            ghc: '9.2'
+        os: [ubuntu-latest, macOS-15-intel, macOS-latest, windows-latest]
+        ghc: ['9.6', '9.8', '9.10', '9.12', '9.14']
     steps:
     - uses: actions/checkout@v4
 
@@ -58,75 +51,6 @@ jobs:
         with:
           args: sh -c "cabal update && cabal test"
 
-  # We use github.com/haskell self-hosted runners for ARM testing.
-  # If they become unavailable in future, put ['armv7', 'aarch64']
-  # back to emulation jobs above.
-  arm:
-    runs-on: [self-hosted, Linux, ARM64]
-    strategy:
-      fail-fast: true
-      matrix:
-        arch: [arm32v7, arm64v8]
-    steps:
-      - uses: docker://hasufell/arm64v8-ubuntu-haskell:focal
-        name: Cleanup
-        with:
-          args: "find . -mindepth 1 -maxdepth 1 -exec rm -rf -- {} +"
-
-      - name: Checkout code
-        uses: actions/checkout@v4
-
-      - if: matrix.arch == 'arm32v7'
-        uses: docker://hasufell/arm32v7-ubuntu-haskell:focal
-        name: Run build (arm32v7 linux)
-        with:
-          args: sh -c "cabal update && ghcup install ghc --isolate=/usr --force 9.2.2 && cabal test -w ghc-9.2.2"
-
-      - if: matrix.arch == 'arm64v8'
-        uses: docker://hasufell/arm64v8-ubuntu-haskell:focal
-        name: Run build (arm64v8 linux)
-        with:
-          args: sh -c "cabal update && ghcup install ghc --isolate=/usr --force 9.2.2 && cabal test -w ghc-9.2.2"
-
-  darwin_arm:
-    runs-on: ${{ matrix.os }}
-    env:
-      MACOSX_DEPLOYMENT_TARGET: 10.13
-      HOMEBREW_CHANGE_ARCH_TO_ARM: 1
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - os: [self-hosted, macOS, ARM64]
-            ghc: 8.10.7
-          - os: [self-hosted, macOS, ARM64]
-            ghc: 9.2.8
-          - os: [self-hosted, macOS, ARM64]
-            ghc: 9.4.7
-    steps:
-      - name: Checkout code
-        uses: actions/checkout@v4
-
-      - name: Install prerequisites
-        run: |
-          bash .github/scripts/brew.sh git coreutils llvm@13 autoconf automake
-          echo PATH="$HOME/.brew/bin:$HOME/.brew/sbin:$HOME/.brew/opt/llvm@13/bin:$PATH" >> "$GITHUB_ENV"
-          echo CC="$HOME/.brew/opt/llvm@13/bin/clang" >> "$GITHUB_ENV"
-          echo CXX="$HOME/.brew/opt/llvm@13/bin/clang++" >> "$GITHUB_ENV"
-          echo LD=ld >> "$GITHUB_ENV"
-          echo AR="$HOME/.brew/opt/llvm@13/bin/llvm-ar" >> "$GITHUB_ENV"
-          echo RANLIB="$HOME/.brew/opt/llvm@13/bin/llvm-ranlib" >> "$GITHUB_ENV"
-
-      - uses: haskell/ghcup-setup@v1
-        with:
-          ghc: ${{ matrix.ghc }}
-          cabal: latest
-
-      - name: Run build
-        run: |
-          cabal update
-          cabal test
-
   freebsd:
     runs-on: ${{ matrix.os }}
     strategy: