diff --git a/.github/scripts/run_scheduled_tests.sh b/.github/scripts/run_scheduled_tests.sh
new file mode 100755
index 000000000..810bdba14
--- /dev/null
+++ b/.github/scripts/run_scheduled_tests.sh
@@ -0,0 +1,117 @@
+#!/bin/sh -eu
+#
+# THis scripts is called by .github/workflows/semi-weeekly_tests.yml
+# The idea is to do some further functional UltraGrid tests
+
+# see also (taken from) .github/scripts/Linux/utils/Dockerfile.ubuntu
+ubuntu_packages="
+    libasound2t64\
+    libegl1\
+    libfontconfig1\
+    libglx-mesa0\
+    libgmp10\
+    libharfbuzz0b\
+    libopengl0\
+    libp11-kit0\
+    libx11-6\
+    openbox\
+    xvfb"
+
+case "$RUNNER_OS" in
+        Linux)
+                sudo apt update
+                sudo apt -y install $ubuntu_packages
+                Xvfb :99 -screen 0 1920x1080x24 &
+                export DISPLAY=:99
+                openbox &
+
+                ug_build=UltraGrid-continuous-x86_64.AppImage
+                prepare() {
+                        chmod +x "$ug_build"
+                        ./"$ug_build" --appimage-extract
+                }
+                run_uv=squashfs-root/AppRun
+                run_reflector="squashfs-root/AppRun -o hd-rum-transcode"
+                ;;
+        Windows)
+                ug_build=UltraGrid-continuous-win64.zip
+                prepare() {
+                        unzip "$ug_build"
+                }
+                run_uv=UltraGrid-continuous-win64/uv.exe
+                run_reflector=UltraGrid-continuous-win64/hd-rum-transcode.exe
+                ;;
+        macOS)
+                ug_build=UltraGrid-continuous-arm64.dmg
+                prepare() {
+                        hdiutil mount "$ug_build"
+                }
+                brew install coreutils
+                alias timeout=gtimeout
+                run_uv=/Volumes/ULTRAGRID/uv-qt.app/Contents/MacOS/uv
+                run_reflector=/Volumes/ULTRAGRID/uv-qt.app/Contents/MacOS/\
+hd-rum-transcode
+esac
+
+curl -LOf https://github.com/CESNET/UltraGrid/releases/download/continuous/\
+"$ug_build"
+
+prepare
+
+## used by run_test_data.sh
+## @param $1 args
+## @param $2 opts (optional, separated by comma):
+##  - should_fail - expected outcome of the command is failure
+##  - should_timeout - the command is expected to keep running
+##                     (will be terminated by timeout)
+##  - run_reflector - instead of uv, pass the args to hd-rum-transcode
+add_test() {
+        eval "test_${test_count}_args=\${1?}"
+        eval "test_${test_count}_opts=\${2-}"
+        test_count=$((test_count + 1))
+}
+
+test_count=0
+. "$(dirname "$0")"/run_scheduled_tests_data.sh
+
+set +e
+i=0
+while [ $i -lt $test_count ]; do
+        eval "args=\$test_${i}_args"
+        eval "opts=\$test_${i}_opts"
+
+        exec=$run_uv
+        tool=uv
+        if expr -- "$opts" : '.*run_reflector' >/dev/null; then
+                tool=reflector
+                exec=$run_reflector
+        fi
+
+        timeout=5
+        timeout $timeout $exec $args
+        rc=$?
+
+        if [ $rc = 124 ]; then
+                if ! expr -- "$opts" : '.*should_timeout' >/dev/null; then
+                        printf "$tool with arguments %s timeout (limit: %d sec)!\n" \
+                                "$args" "$timeout"
+                        exit 1
+                fi
+        elif expr -- "$opts" : '.*should_fail' >/dev/null; then
+                if [ $rc -eq 0 ]; then
+                        printf "$tool with arguments %s should have failed but\
+ returned 0!\n" "$args"
+                        exit 1
+                fi
+        else
+                if [ $rc -ne 0 ]; then
+                        printf "$tool with arguments %s returned %d but should have\
+ succeeeded!\n" "$args" "$rc"
+                        exit 1
+                fi
+
+        fi
+
+        i=$((i + 1))
+done
+
diff --git a/.github/scripts/run_scheduled_tests_data.sh b/.github/scripts/run_scheduled_tests_data.sh
new file mode 100644
index 000000000..0defd0342
--- /dev/null
+++ b/.github/scripts/run_scheduled_tests_data.sh
@@ -0,0 +1,14 @@
+# test cases for run_scheduled_tests.sh
+#
+# For the documentation of add_test parameters see the
+# run_scheduled_tests.sh file.
+
+# UltraGrid
+add_test -v                                                  # basic sanity test
+add_test --nonexistent-param                   should_fail
+add_test "-d sdl"                              should_timeout
+add_test "-t testcard -c lavc:e=libx265 -f rs -d dummy" should_timeout
+
+# reflector
+add_test -v                                    run_reflector # basic sanity test
+add_test "8M 5004"                             run_reflector,should_timeout
diff --git a/.github/workflows/coverity-scan.yml b/.github/workflows/coverity-scan.yml
index ef99aeb1f..ac54b2cd9 100644
--- a/.github/workflows/coverity-scan.yml
+++ b/.github/workflows/coverity-scan.yml
@@ -9,6 +9,7 @@ on:
 
 jobs:
   Coverity:
+    # run by cron only in CESNET/UltraGrid, on push to coverity_scan anywhere
     if: github.repository == 'CESNET/UltraGrid' || github.event.schedule == null
     runs-on: ubuntu-latest
     env:
diff --git a/.github/workflows/semi-weekly_tests.yml b/.github/workflows/semi-weekly_tests.yml
new file mode 100644
index 000000000..7c82a2d33
--- /dev/null
+++ b/.github/workflows/semi-weekly_tests.yml
@@ -0,0 +1,27 @@
+name: Continuous build semi-weekly tests
+
+on:
+  push:
+    branches:
+      - run_tests
+  schedule:
+   - cron:  '00 13 * * 1,5' # Mo,Fr at 13:00 UTC
+
+jobs:
+  run_tests:
+    # run by cron only in CESNET/UltraGrid, on push to run_tests anywhere
+    if: github.repository == 'CESNET/UltraGrid' || github.event.schedule == null
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+
+    runs-on: ${{ matrix.os }}
+    defaults:
+      run:
+        shell: ${{ matrix.os == 'windows-latest' && 'C:\shells\msys2bash.cmd {0}' || 'bash {0}' }}
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Run
+      shell: bash
+      run: .github/scripts/run_scheduled_tests.sh