diff --git a/.github/workflows/Build.yml b/.github/workflows/Build.yml
index 6248fc431..22b0c3fe2 100644
--- a/.github/workflows/Build.yml
+++ b/.github/workflows/Build.yml
@@ -90,6 +90,58 @@ jobs:
       #   uses: mxschmitt/action-tmate@v3
       #   timeout-minutes: 15
 
+  # Build and test QUIP with MPI + ScaLAPACK (Linux only)
+  build-mpi:
+    name: Build QUIP with MPI (ubuntu-latest)
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          submodules: 'recursive'
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update -y
+          sudo apt-get install -y gfortran meson ninja-build \
+            libopenblas-dev liblapack-dev \
+            libnetcdf-dev libhdf5-serial-dev \
+            libopenmpi-dev libscalapack-openmpi-dev
+
+      - name: Install Python dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install numpy ase meson-python build
+          pip install 'f90wrap>=0.3.0'
+        env:
+          FC: gfortran
+          CC: gcc
+
+      - name: Build QUIP libraries (MPI)
+        run: |
+          meson setup builddir -Dmpi=true
+          meson compile -C builddir
+
+      - name: Build and install quippy
+        run: |
+          cd quippy
+          pip install .
+
+      - name: Run tests (including ScaLAPACK)
+        run: |
+          cd tests
+          BUILDDIR=${{ github.workspace }}/builddir/src/Programs \
+            HAVE_SCALAPACK=1 \
+            OMPI_ALLOW_RUN_AS_ROOT=1 \
+            OMPI_ALLOW_RUN_AS_ROOT_CONFIRM=1 \
+            python run_all.py
+
   # Builds the QUIP docs webpage image. This only happens ON the public
   # branch, after tests pass and pull requests are completed
   # TEMPORARILY DISABLED - needs investigation
diff --git a/meson.build b/meson.build
index f6aa346a9..7901cd4e5 100644
--- a/meson.build
+++ b/meson.build
@@ -31,6 +31,7 @@ if get_option('gap')
     '-DGAP_VERSION='+gap_version_res.stdout().strip(),
     '-DHAVE_GAP',
     '-DHAVE_TB',
+    '-DHAVE_QR',
     ], language:'fortran')
 endif
 
@@ -65,8 +66,13 @@ add_global_arguments([
 
 if get_option('mpi')
   message('MPI ON')
+  scalapack_dep = dependency('scalapack', required: false)
+  if not scalapack_dep.found()
+    message('scalapack not found via pkg-config/cmake, trying system library search')
+    scalapack_dep = fortran.find_library('scalapack', required: true)
+  endif
   mpi_dep = [
-    dependency('scalapack'),
+    scalapack_dep,
     dependency('mpi', language: 'fortran'),
     dependency('mpi', language: 'c'),
   ]
diff --git a/src/Programs/meson.build b/src/Programs/meson.build
index 5a8fb65d6..015cb8140 100644
--- a/src/Programs/meson.build
+++ b/src/Programs/meson.build
@@ -12,7 +12,7 @@ link_quip = [
 # gap_fit library (special case - needed before gap_fit_exe)
 gap_fit_lib = library('gap_fit',
   '../GAP/gap_fit_module.F90',
-  dependencies: [blas_dep],
+  dependencies: [blas_dep, mpi_dep],
   link_with: link_quip,
 )
 
diff --git a/tests/test_gapfit.py b/tests/test_gapfit.py
index 2cd40416c..cdcb732bc 100644
--- a/tests/test_gapfit.py
+++ b/tests/test_gapfit.py
@@ -125,6 +125,13 @@ def check_gap_committee(self, err_tol=0.2):
         assert np.all(mean_errs < err_tol)
         np.random.seed(None)
 
+    def check_qr_path(self):
+        """check that QR decomposition was used (requires -DHAVE_QR)"""
+        with open(self.log_name) as f:
+            log = f.read()
+        self.assertIn("Using LAPACK to solve QR", log,
+                      "QR decomposition not used - check -DHAVE_QR is set")
+
     def check_gap_fit(self, ref_file=None):
         """check GP coefficients match expected values"""
         assert self.proc.returncode == 0, self.proc
@@ -226,6 +233,7 @@ def test_si_soap_cur_points(self):
         gap = self.get_gap(self.gap_soap_template, 'sparse_method=cur_points')
         config = self.get_config('Si.np1.xyz', gap, extra='condition_number_norm=I')
         self.run_gap_fit(config)
+        self.check_qr_path()
         self.check_gap_fit(ref_file)
 
     def test_si_distance_2b_uniform(self):
@@ -234,6 +242,7 @@ def test_si_distance_2b_uniform(self):
         gap = self.get_gap(self.gap_distance_2b_template, 'sparse_method=uniform')
         config = self.get_config('Si.np1.xyz', gap)
         self.run_gap_fit(config)
+        self.check_qr_path()
         self.check_gap_fit(ref_file)
 
     def test_si_two_descriptors(self):
@@ -244,6 +253,7 @@ def test_si_two_descriptors(self):
         gap = ":".join([gap1, gap2])
         config = self.get_config('Si.np1.xyz', gap)
         self.run_gap_fit(config)
+        self.check_qr_path()
         self.check_gap_fit(ref_file)
 
     def test_sic_distance_2b_uniform(self):
@@ -252,6 +262,7 @@ def test_sic_distance_2b_uniform(self):
         gap = self.get_gap(self.gap_distance_2b_template, 'sparse_method=uniform')
         config = self.get_config('SiC.np1.xyz', gap)
         self.run_gap_fit(config)
+        self.check_qr_path()
         self.check_gap_fit(ref_file)
 
     def test_si_distance_2b_index(self):
@@ -261,6 +272,7 @@ def test_si_distance_2b_index(self):
         config = self.get_config('Si.np1.xyz', gap)
         self.make_first_index_file_from_ref(ref_file, self.index_name_inp)
         self.run_gap_fit(config)
+        self.check_qr_path()
         self.check_gap_fit(ref_file)
 
     def test_si_config_file_sparsify_only(self):