diff --git a/.github/workflows/cmake.yml b/.github/workflows/cmake.yml
index aff291dd9d8..5ea7c4ce135 100644
--- a/.github/workflows/cmake.yml
+++ b/.github/workflows/cmake.yml
@@ -27,6 +27,13 @@ jobs:
     runs-on: ubuntu-22.04
     env:
       CMakeVersion: "3.22.0"
+      CC: clang-${{ matrix.llvm-version }}
+      CXX: clang++-${{ matrix.llvm-version }}
+      ASAN_OPTIONS: detect_leaks=0
+
+    strategy:
+      matrix:
+        llvm-version: [19]
     steps:
       - name: Checkout GRASS
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
@@ -41,10 +48,19 @@ jobs:
           echo "$GITHUB_WORKSPACE/cmake-${{ env.CMakeVersion }}-${arch}/bin" >> $GITHUB_PATH
       - run: |
           cmake --version
+      - name: Apt LLVM
+        run: |
+          wget https://apt.llvm.org/llvm.sh
+          chmod +x llvm.sh
+          sudo ./llvm.sh ${{ matrix.llvm-version }}
+          sudo apt-get update
       - name: Install dependencies
         run: |
           sudo apt-get update -y
           sudo apt-get install -y wget git gawk findutils ninja-build libpq-dev \
+            clang-${{ matrix.llvm-version }} clang-tools-${{ matrix.llvm-version }} \
+            libomp-${{ matrix.llvm-version }}-dev lld-${{ matrix.llvm-version }} \
+            llvm-${{ matrix.llvm-version }} \
             gettext unixodbc-dev libnetcdf-dev
           xargs -a <(awk '! /^ *(#|$)/' ".github/workflows/apt.txt") -r -- \
               sudo apt-get install -y --no-install-recommends --no-install-suggests
@@ -61,7 +77,9 @@ jobs:
         run: |
           cmake ${CMAKE_OPTIONS} -S $GITHUB_WORKSPACE -B $GITHUB_WORKSPACE/build -G Ninja \
             -DCMAKE_INSTALL_PREFIX=$HOME/install -DWITH_NLS=ON -DWITH_GUI=OFF -DWITH_DOCS=OFF \
-            -DWITH_READLINE=ON -DWITH_ODBC=ON -DWITH_NETCDF=ON -DWITH_BZLIB=ON
+            -DWITH_READLINE=ON -DWITH_ODBC=ON -DWITH_NETCDF=ON -DWITH_BZLIB=ON \
+            -DBUILD_SHARED_LIBS=OFF \
+            -DCMAKE_C_COMPILER=clang-${{ matrix.llvm-version }} -DCMAKE_CXX_COMPILER=clang++-${{ matrix.llvm-version }}
       - name: Print CMakeCache.txt
         shell: bash -el {0}
         run: |
@@ -75,6 +93,8 @@ jobs:
       - name: Add the bin directory to PATH
         run: |
           echo "$HOME/install/bin" >> $GITHUB_PATH
+      - name: Set profile file name env var
+        run: echo "LLVM_PROFILE_FILE=${{ github.workspace }}/grass-prof-%p-%4m.profraw" >> $GITHUB_ENV
       - name: Print installed versions
         if: always()
         run: .github/workflows/print_versions.sh
@@ -89,3 +109,46 @@ jobs:
           name: testreport-CMake
           path: testreport
           retention-days: 3
+      - name: Use llvm's coverage script
+        if: ${{ !cancelled() }}
+        run: |
+          WORKSPACE=$GITHUB_WORKSPACE
+
+          BUILD_DIR=$(pwd)/dist*
+          FAST_BUILD_DIR=$(pwd)/clang-build
+          REPORT_DIR=$(pwd)/coverage-reports
+          HOST=
+          LLVM_PROFDATA=llvm-profdata-${{ matrix.llvm-version }}
+          LLVM_COV=llvm-cov-${{ matrix.llvm-version }}
+          ARTIFACT_PREP_SCRIPT=$WORKSPACE/utils/prepare-code-coverage-artifact.py
+
+          PROFILES_DIR=$WORKSPACE
+
+          COV_BINARIES=$(find ./build/output/ -type f \( -executable -o -name "*.dylib" -o -name "*.so*" \) \
+            -exec file {} + | grep -E 'Mach-O|ELF' | cut -d':' -f1)
+
+          rm -rf $REPORT_DIR
+          mkdir -p $REPORT_DIR
+          python $ARTIFACT_PREP_SCRIPT $LLVM_PROFDATA $LLVM_COV \
+            $PROFILES_DIR $REPORT_DIR $COV_BINARIES \
+            --unified-report \
+            --lcov=grass.llvm-source.coverage.lcov
+      - name: Make profile data available
+        if: ${{ !cancelled() }}
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
+        with:
+          name: >-
+            profile-data-${{ 'cmake' }}
+          path: |
+            *.prof*
+            *coverage*
+            llvm_coverage*/**
+          retention-days: 1
+      - name: Upload coverage reports to Codecov
+        if: ${{ !cancelled() }}
+        uses: codecov/codecov-action@18283e04ce6e62d37312384ff67231eb8fd56d24 # v5.4.3
+        with:
+          verbose: true
+          flags: linux-cmake
+          name: linux-cmake
+          token: ${{ secrets.CODECOV_TOKEN }}
diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index e9e693e57c3..1ba916cb163 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -55,6 +55,7 @@ jobs:
       - name: Prepare Conda environment file
         env:
           test_dependencies: |
+            findutils
             ipython
             pytest
             pytest-github-actions-annotate-failures
@@ -73,6 +74,8 @@ jobs:
           # Persist on the same period (date).
           cache-environment-key: environment-${{ steps.date.outputs.date }}
 
+      - name: Set profile file name env var
+        run: echo "LLVM_PROFILE_FILE=${{ github.workspace }}/grass-prof-%p-%4m.profraw" >> $GITHUB_ENV
       - name: Environment info
         shell: bash -el {0}
         run: |
@@ -89,6 +92,9 @@ jobs:
         if: ${{ !cancelled() }}
         shell: micromamba-shell {0}
         run: source ./.github/workflows/print_versions.sh
+      - name: Print config
+        shell: micromamba-shell {0}
+        run: grass --config
 
       - name: Run pytest with multiple workers in parallel
         shell: micromamba-shell {0}
@@ -147,3 +153,61 @@ jobs:
           name: testreport-macOS
           path: testreport
           retention-days: 3
+      # - name: Merge and index profile data
+      #   shell: micromamba-shell {0}
+      #   run: |
+      #     llvm-profdata merge -sparse *.profraw -o merged.profdata
+      #     rm *.profraw
+      # - name: Export coverage report with llvm-cov export (all, json)
+      #   shell: micromamba-shell {0}
+      #   continue-on-error: true
+      #   run: |
+      #     COV_BINARIES=$(find . -type f \( -executable -o -name "*.dylib" \) \
+      #       -exec file {} + | grep -E 'Mach-O|ELF' | cut -d':' -f1)
+      #     llvm-cov export -format=text -instr-profile=merged.profdata \
+      #       /Users/runner/install/grass85/lib/libgrass_gis.8.5.dylib  \
+      #       | tee coverage.all1.json
+      - name: Use llvm's coverage script
+        if: ${{ !cancelled() }}
+        shell: micromamba-shell {0}
+        run: |
+          WORKSPACE=$GITHUB_WORKSPACE
+
+          BUILD_DIR=$(pwd)/dist*
+          FAST_BUILD_DIR=$(pwd)/clang-build
+          REPORT_DIR=$(pwd)/coverage-reports
+          HOST=
+          LLVM_PROFDATA=llvm-profdata
+          LLVM_COV=llvm-cov
+          ARTIFACT_PREP_SCRIPT=$WORKSPACE/utils/prepare-code-coverage-artifact.py
+
+          PROFILES_DIR=$WORKSPACE
+
+          COV_BINARIES=$(find . -type f \( -executable -o -name "*.dylib" \) \
+            -exec file {} + | grep -E 'Mach-O|ELF' | cut -d':' -f1)
+
+          rm -rf $REPORT_DIR
+          mkdir -p $REPORT_DIR
+          python $ARTIFACT_PREP_SCRIPT $LLVM_PROFDATA $LLVM_COV \
+            $PROFILES_DIR $REPORT_DIR $COV_BINARIES \
+            --unified-report \
+            --lcov=grass.llvm-source.coverage.lcov
+      - name: Make profile data available
+        if: ${{ !cancelled() }}
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
+        with:
+          name: >-
+            profile-data-${{ 'macos-14' }}
+          path: |
+            *.prof*
+            *coverage*
+            llvm_coverage*/**
+          retention-days: 1
+      - name: Upload coverage reports to Codecov
+        if: ${{ !cancelled() }}
+        uses: codecov/codecov-action@18283e04ce6e62d37312384ff67231eb8fd56d24 # v5.4.3
+        with:
+          verbose: true
+          flags: pytest-macos-14
+          name: pytest-macos-14
+          token: ${{ secrets.CODECOV_TOKEN }}
diff --git a/.github/workflows/macos_install.sh b/.github/workflows/macos_install.sh
index 4f340c73f9e..bdb19d5c6d4 100755
--- a/.github/workflows/macos_install.sh
+++ b/.github/workflows/macos_install.sh
@@ -59,14 +59,20 @@ CONFIGURE_FLAGS="\
   --without-x \
 "
 
+export EXTRA_COV_FLAGS="-fprofile-instr-generate -fcoverage-mapping"
 export CFLAGS="-O2 -pipe -ffp-contract=off -arch ${CONDA_ARCH} -DGL_SILENCE_DEPRECATION -Wall -Wextra -Wpedantic -Wvla"
 export CXXFLAGS="-O2 -pipe -ffp-contract=off -stdlib=libc++ -arch ${CONDA_ARCH} -Wall -Wextra -Wpedantic"
 export CPPFLAGS="-isystem${CONDA_PREFIX}/include"
 
-./configure $CONFIGURE_FLAGS
+export CFLAGS="$EXTRA_COV_FLAGS $CFLAGS"
+export CXXFLAGS="$EXTRA_COV_FLAGS $CXXFLAGS"
+
+LDFLAGS="-fprofile-instr-generate $LDFLAGS" ./configure $CONFIGURE_FLAGS
 
 EXEMPT=""
-make -j$(sysctl -n hw.ncpu) CFLAGS="$CFLAGS -Werror $EXEMPT" \
+# make -j$(sysctl -n hw.ncpu) CFLAGS="$CFLAGS -Werror $EXEMPT" \
+#   CXXFLAGS="$CXXFLAGS -Werror $EXEMPT"
+make -j1 CFLAGS="$CFLAGS -Werror $EXEMPT" \
   CXXFLAGS="$CXXFLAGS -Werror $EXEMPT"
 
 make install
diff --git a/.gunittest.cfg b/.gunittest.cfg
index bb5636cbb51..0419736f180 100644
--- a/.gunittest.cfg
+++ b/.gunittest.cfg
@@ -25,6 +25,9 @@ exclude =
     vector/v.in.pdal/testsuite/test_v_in_pdal_basic.py
     vector/v.in.pdal/testsuite/test_v_in_pdal_filter.py
     vector/v.out.lidar/testsuite/test_v_out_lidar.py
+    temporal/.*
+    *.sh
+    raster/r.s*
 
 # Maximum time for execution of one test file (not a test function)
 # after which test is terminated (which may not terminate child processes
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 255b94dfc99..ab42d05eeee 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -45,6 +45,9 @@ if(NOT CMAKE_C_STANDARD)
   set(CMAKE_C_STANDARD 11)
   set(CMAKE_C_STANDARD_REQUIRED ON)
 endif()
+SET(CMAKE_CXX_FLAGS  "${CMAKE_CXX_FLAGS} -g -fprofile-instr-generate -fcoverage-mapping -fno-omit-frame-pointer -fsanitize=address")
+SET(CMAKE_C_FLAGS  "${CMAKE_C_FLAGS} -g -fprofile-instr-generate -fcoverage-mapping -fno-omit-frame-pointer -fsanitize=address")
+SET(CMAKE_EXE_LINKER_FLAGS  "${CMAKE_EXE_LINKER_FLAGS} -fprofile-instr-generate -fno-omit-frame-pointer -fsanitize=address")
 
 set(x11_default_option_enabled ON)
 set(nls_default_option_enabled ON)
diff --git a/imagery/i.smap/model.c b/imagery/i.smap/model.c
index dd567cfe5bb..4dd3ab5f761 100644
--- a/imagery/i.smap/model.c
+++ b/imagery/i.smap/model.c
@@ -141,7 +141,7 @@ void extract(DCELL ***img,          /* multispectral image, img[band][i][j] */
                         ll[i][j][m] = subll[0];
                     }
                     /* compute mixture likelihood */
-                    else {
+                    else if (C->nsubclasses > 1) {
                         /* find the most likely subclass */
                         for (k = 0; k < C->nsubclasses; k++) {
                             if (k == 0)
@@ -157,6 +157,9 @@ void extract(DCELL ***img,          /* multispectral image, img[band][i][j] */
 
                         ll[i][j][m] = log(subsum) + maxlike;
                     }
+                    else {
+                        ll[i][j][m] = 0.0;
+                    }
                 }
             }
         }
diff --git a/utils/prepare-code-coverage-artifact.py b/utils/prepare-code-coverage-artifact.py
new file mode 100644
index 00000000000..5edc4538133
--- /dev/null
+++ b/utils/prepare-code-coverage-artifact.py
@@ -0,0 +1,266 @@
+#!/usr/bin/env python
+
+
+"""Prepare a code coverage artifact.
+
+- Collate raw profiles into one indexed profile.
+- Generate html reports for the given binaries.
+
+Caution: The positional arguments to this script must be specified before any
+optional arguments, such as --restrict.
+"""
+
+import argparse
+import glob
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+
+def merge_raw_profiles(host_llvm_profdata, profile_data_dir, preserve_profiles):
+    print(":: Merging raw profiles...", end="")
+    sys.stdout.flush()
+    raw_profiles = glob.glob(os.path.join(profile_data_dir, "*.profraw"))
+    manifest_path = os.path.join(profile_data_dir, "profiles.manifest")
+    profdata_path = os.path.join(profile_data_dir, "Coverage.profdata")
+    Path(manifest_path).write_text("\n".join(raw_profiles), encoding="utf-8")
+    subprocess.check_call(
+        [
+            host_llvm_profdata,
+            "merge",
+            "-sparse",
+            "-f",
+            manifest_path,
+            "-o",
+            profdata_path,
+        ]
+    )
+    if not preserve_profiles:
+        for raw_profile in raw_profiles:
+            os.remove(raw_profile)
+    os.remove(manifest_path)
+    print("Done!")
+    return profdata_path
+
+
+def prepare_export_file(
+    host_llvm_cov,
+    profile,
+    report_file,
+    binaries,
+    restricted_dirs,
+    compilation_dir,
+    export_format,
+):
+    export_format_label = export_format
+    if export_format == "text":
+        export_format_label = "json"
+    print(f":: Preparing {export_format_label} report for {binaries}...", end="")
+    sys.stdout.flush()
+    objects = []
+    for i, binary in enumerate(binaries):
+        if i == 0:
+            objects.append(binary)
+        else:
+            objects.extend(("-object", binary))
+    invocation = (
+        [host_llvm_cov, "export"]
+        + objects
+        + [
+            "-format",
+            export_format,
+            "-instr-profile",
+            profile,
+            "-skip-functions",
+        ]
+        + restricted_dirs
+    )
+    if compilation_dir:
+        invocation += ["-compilation-dir=" + compilation_dir]
+    with Path(report_file).open("w", encoding="utf-8") as summary:
+        subprocess.check_call(
+            invocation,
+            stdout=summary,
+        )
+    print("Done!")
+
+
+def prepare_html_report(
+    host_llvm_cov, profile, report_dir, binaries, restricted_dirs, compilation_dir
+):
+    print(f":: Preparing html report for {binaries}...", end="")
+    sys.stdout.flush()
+    objects = []
+    for i, binary in enumerate(binaries):
+        if i == 0:
+            objects.append(binary)
+        else:
+            objects.extend(("-object", binary))
+    invocation = (
+        [host_llvm_cov, "show"]
+        + objects
+        + [
+            "-format",
+            "html",
+            "-instr-profile",
+            profile,
+            "-o",
+            report_dir,
+            "-show-line-counts-or-regions",
+            "-dump",
+            "-show-directory-coverage",
+            "-Xdemangler",
+            "c++filt",
+            "-Xdemangler",
+            "-n",
+        ]
+        + restricted_dirs
+    )
+    if compilation_dir:
+        invocation += ["-compilation-dir=" + compilation_dir]
+    subprocess.check_call(invocation)
+    with Path(report_dir, "summary.txt").open("wb") as summary:
+        subprocess.check_call(
+            [host_llvm_cov, "report"]
+            + objects
+            + ["-instr-profile", profile]
+            + restricted_dirs,
+            stdout=summary,
+        )
+    print("Done!")
+
+
+def prepare_html_reports(
+    host_llvm_cov,
+    profdata_path,
+    report_dir,
+    binaries,
+    unified_report,
+    restricted_dirs,
+    compilation_dir,
+):
+    if unified_report:
+        prepare_html_report(
+            host_llvm_cov,
+            profdata_path,
+            report_dir,
+            binaries,
+            restricted_dirs,
+            compilation_dir,
+        )
+    else:
+        for binary in binaries:
+            binary_report_dir = os.path.join(report_dir, os.path.basename(binary))
+            prepare_html_report(
+                host_llvm_cov,
+                profdata_path,
+                binary_report_dir,
+                [binary],
+                restricted_dirs,
+                compilation_dir,
+            )
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("host_llvm_profdata", help="Path to llvm-profdata")
+    parser.add_argument("host_llvm_cov", help="Path to llvm-cov")
+    parser.add_argument(
+        "profile_data_dir", help="Path to the directory containing the raw profiles"
+    )
+    parser.add_argument(
+        "report_dir", help="Path to the output directory for html reports"
+    )
+    parser.add_argument(
+        "binaries",
+        metavar="B",
+        type=str,
+        nargs="*",
+        help="Path to an instrumented binary",
+    )
+    parser.add_argument(
+        "--only-merge",
+        action="store_true",
+        help="Only merge raw profiles together, skip report generation",
+    )
+    parser.add_argument(
+        "--preserve-profiles", help="Do not delete raw profiles", action="store_true"
+    )
+    parser.add_argument(
+        "--use-existing-profdata", help="Specify an existing indexed profile to use"
+    )
+    parser.add_argument(
+        "--unified-report",
+        action="store_true",
+        help="Emit a unified report for all binaries",
+    )
+    parser.add_argument(
+        "--json", help="If specified, export the coverage data to this json file"
+    )
+    parser.add_argument(
+        "--lcov", help="If specified, export the coverage data to this lcov file"
+    )
+    parser.add_argument(
+        "--restrict",
+        metavar="R",
+        type=str,
+        nargs="*",
+        default=[],
+        help="Restrict the reporting to the given source paths"
+        " (must be specified after all other positional arguments)",
+    )
+    parser.add_argument(
+        "-C",
+        "--compilation-dir",
+        type=str,
+        default="",
+        help="The compilation directory of the binary",
+    )
+    args = parser.parse_args()
+
+    if args.use_existing_profdata and args.only_merge:
+        print("--use-existing-profdata and --only-merge are incompatible")
+        sys.exit(1)
+
+    if args.use_existing_profdata:
+        profdata_path = args.use_existing_profdata
+    else:
+        profdata_path = merge_raw_profiles(
+            args.host_llvm_profdata, args.profile_data_dir, args.preserve_profiles
+        )
+
+    if not len(args.binaries):
+        print("No binaries specified, no work to do!")
+        sys.exit(1)
+
+    if not args.only_merge:
+        prepare_html_reports(
+            args.host_llvm_cov,
+            profdata_path,
+            args.report_dir,
+            args.binaries,
+            args.unified_report,
+            args.restrict,
+            args.compilation_dir,
+        )
+        if args.json:
+            prepare_export_file(
+                args.host_llvm_cov,
+                profdata_path,
+                args.json,
+                args.binaries,
+                args.restrict,
+                args.compilation_dir,
+                export_format="text",
+            )
+        if args.lcov:
+            prepare_export_file(
+                args.host_llvm_cov,
+                profdata_path,
+                args.lcov,
+                args.binaries,
+                args.restrict,
+                args.compilation_dir,
+                export_format="lcov",
+            )