diff --git a/cyberpanel_upgrade.sh b/cyberpanel_upgrade.sh
index e09daba9c..c3aea01d1 100644
--- a/cyberpanel_upgrade.sh
+++ b/cyberpanel_upgrade.sh
@@ -1671,9 +1671,9 @@ if [[ "$*" != *"--branch "* ]] && [[ "$*" != *"-b "* ]] ; then
   Pre_Upgrade_Branch_Input
 fi
 
-# Prompt for MariaDB version if not set via --mariadb-version (default 11.8)
+# Prompt for MariaDB version if not set via --mariadb-version (default 11.8). Downgrade supported (e.g. re-run with --mariadb-version 11.8).
 if [[ "$*" != *"--mariadb-version "* ]]; then
-  echo -e "\nMariaDB version: use \e[31m11.8\e[39m LTS (default) or \e[31m12.1\e[39m."
+  echo -e "\nMariaDB version: \e[31m11.8\e[39m LTS (default) or \e[31m12.1\e[39m. You can switch later by re-running with --mariadb-version 11.8 or 12.1."
   echo -e "Press Enter for 11.8 LTS, or type \e[31m12.1\e[39m and Enter for 12.1 (5 sec timeout): "
   read -r -t 5 Tmp_MariaDB_Ver || true
   if [[ "$Tmp_MariaDB_Ver" = "12.1" ]]; then
diff --git a/test/run_mariadb_tests.sh b/test/run_mariadb_tests.sh
new file mode 100755
index 000000000..d63027184
--- /dev/null
+++ b/test/run_mariadb_tests.sh
@@ -0,0 +1,14 @@
+#!/bin/bash
+# Run all MariaDB version tests (upgrader + upgrade.py logic).
+# From repo root: ./test/run_mariadb_tests.sh
+set -e
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+cd "$REPO_ROOT"
+echo "=== Upgrader MariaDB version tests ==="
+./test/upgrader_mariadb_version_test.sh
+echo ""
+echo "=== Upgrade.py mariadb_version read tests ==="
+python3 test/test_upgrade_mariadb_version.py
+echo ""
+echo "=== All MariaDB version tests passed (11.8, 12.1, downgrade). ==="
diff --git a/test/test_upgrade_mariadb_version.py b/test/test_upgrade_mariadb_version.py
new file mode 100644
index 000000000..d11d9e1f5
--- /dev/null
+++ b/test/test_upgrade_mariadb_version.py
@@ -0,0 +1,112 @@
+#!/usr/bin/env python3
+"""
+Unit tests for plogical/upgrade.py MariaDB version read from /etc/cyberpanel/mariadb_version.
+Tests that 11.8 and 12.1 are both accepted and that downgrade (12.1 -> 11.8) is supported.
+Run from repo root: python3 test/test_upgrade_mariadb_version.py
+"""
+import os
+import sys
+import tempfile
+
+# Logic extracted from Upgrade.fix_almalinux9_mariadb() - read mariadb_version file
+def read_mariadb_version_from_file(filepath):
+    mariadb_ver = "11.8"
+    try:
+        if os.path.isfile(filepath):
+            with open(filepath, "r") as f:
+                raw = f.read().strip()
+                if raw in ("11.8", "12.1"):
+                    mariadb_ver = raw
+    except Exception:
+        pass
+    return mariadb_ver
+
+
+def test_default_no_file():
+    with tempfile.TemporaryDirectory() as d:
+        path = os.path.join(d, "nonexistent")
+        assert read_mariadb_version_from_file(path) == "11.8"
+    print("OK: default when file missing = 11.8")
+
+
+def test_11_8():
+    with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".tmp") as f:
+        f.write("11.8")
+        path = f.name
+    try:
+        assert read_mariadb_version_from_file(path) == "11.8"
+        print("OK: file 11.8 -> 11.8")
+    finally:
+        os.unlink(path)
+
+
+def test_12_1():
+    with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".tmp") as f:
+        f.write("12.1")
+        path = f.name
+    try:
+        assert read_mariadb_version_from_file(path) == "12.1"
+        print("OK: file 12.1 -> 12.1")
+    finally:
+        os.unlink(path)
+
+
+def test_downgrade_simulation():
+    # Simulate writing 12.1 then 11.8 (downgrade) - both must work
+    with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".tmp") as f:
+        f.write("12.1")
+        path = f.name
+    try:
+        assert read_mariadb_version_from_file(path) == "12.1"
+        print("OK: downgrade step 1 - 12.1")
+    finally:
+        pass
+    with open(path, "w") as f:
+        f.write("11.8")
+    try:
+        assert read_mariadb_version_from_file(path) == "11.8"
+        print("OK: downgrade step 2 - 11.8 (downgrade supported)")
+    finally:
+        os.unlink(path)
+
+
+def test_invalid_falls_back():
+    with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".tmp") as f:
+        f.write("10.11")
+        path = f.name
+    try:
+        assert read_mariadb_version_from_file(path) == "11.8"
+        print("OK: invalid 10.11 -> 11.8")
+    finally:
+        os.unlink(path)
+    with tempfile.NamedTemporaryFile(mode="w", delete=False, suffix=".tmp") as f:
+        f.write("13")
+        path = f.name
+    try:
+        assert read_mariadb_version_from_file(path) == "11.8"
+        print("OK: invalid 13 -> 11.8")
+    finally:
+        os.unlink(path)
+
+
+def test_repo_command_format():
+    mariadb_ver = "12.1"
+    command = "curl -sS https://downloads.mariadb.com/MariaDB/mariadb_repo_setup | bash -s -- --mariadb-server-version='%s'" % mariadb_ver
+    assert "12.1" in command
+    assert "--mariadb-server-version='12.1'" in command
+    print("OK: repo command includes version 12.1")
+    mariadb_ver = "11.8"
+    command = "curl -sS https://downloads.mariadb.com/MariaDB/mariadb_repo_setup | bash -s -- --mariadb-server-version='%s'" % mariadb_ver
+    assert "--mariadb-server-version='11.8'" in command
+    print("OK: repo command includes version 11.8")
+
+
+if __name__ == "__main__":
+    test_default_no_file()
+    test_11_8()
+    test_12_1()
+    test_downgrade_simulation()
+    test_invalid_falls_back()
+    test_repo_command_format()
+    print("\nAll upgrade.py MariaDB version tests passed.")
+    sys.exit(0)
diff --git a/test/upgrader_mariadb_version_test.sh b/test/upgrader_mariadb_version_test.sh
new file mode 100755
index 000000000..89810cafd
--- /dev/null
+++ b/test/upgrader_mariadb_version_test.sh
@@ -0,0 +1,105 @@
+#!/bin/bash
+# Test script for cyberpanel_upgrade.sh MariaDB version handling (11.8, 12.1, downgrade).
+# Run from repo root: ./test/upgrader_mariadb_version_test.sh
+# Does not require root or a real CyberPanel install.
+
+set -e
+FAILED=0
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+UPGRADE_SCRIPT="$REPO_ROOT/cyberpanel_upgrade.sh"
+
+# Default (same as cyberpanel_upgrade.sh)
+MARIADB_VER="11.8"
+
+# Parse --mariadb-version from "$@" (same logic as Check_Argument in cyberpanel_upgrade.sh)
+parse_mariadb_version() {
+  if [[ "$*" = *"--mariadb-version "* ]]; then
+    MARIADB_VER=$(echo "$*" | sed -n 's/.*--mariadb-version \([^ ]*\).*/\1/p' | head -1)
+    MARIADB_VER="${MARIADB_VER:-11.8}"
+  fi
+  if [[ "$MARIADB_VER" != "11.8" ]] && [[ "$MARIADB_VER" != "12.1" ]]; then
+    MARIADB_VER="11.8"
+  fi
+}
+
+assert_equals() {
+  local expected="$1"
+  local actual="$2"
+  local name="${3:-value}"
+  if [[ "$actual" != "$expected" ]]; then
+    echo "FAIL: $name expected '\''$expected'\'' got '\''$actual'\''"
+    FAILED=1
+  else
+    echo "OK: $name = $actual"
+  fi
+}
+
+echo "=== 1. Default (no --mariadb-version) ==="
+MARIADB_VER="11.8"
+parse_mariadb_version ""
+assert_equals "11.8" "$MARIADB_VER" "default"
+
+echo ""
+echo "=== 2. Explicit 11.8 ==="
+MARIADB_VER="11.8"
+parse_mariadb_version "--mariadb-version 11.8"
+assert_equals "11.8" "$MARIADB_VER" "--mariadb-version 11.8"
+
+echo ""
+echo "=== 3. Explicit 12.1 ==="
+MARIADB_VER="11.8"
+parse_mariadb_version "--mariadb-version 12.1"
+assert_equals "12.1" "$MARIADB_VER" "--mariadb-version 12.1"
+
+echo ""
+echo "=== 4. Downgrade: 12.1 then 11.8 (both must be accepted) ==="
+MARIADB_VER="11.8"
+parse_mariadb_version "--mariadb-version 12.1"
+assert_equals "12.1" "$MARIADB_VER" "first 12.1"
+parse_mariadb_version "--mariadb-version 11.8"
+assert_equals "11.8" "$MARIADB_VER" "then 11.8 (downgrade)"
+
+echo ""
+echo "=== 5. Invalid value falls back to 11.8 ==="
+MARIADB_VER="11.8"
+parse_mariadb_version "--mariadb-version 10.11"
+assert_equals "11.8" "$MARIADB_VER" "invalid 10.11 -> 11.8"
+parse_mariadb_version "--mariadb-version 13"
+assert_equals "11.8" "$MARIADB_VER" "invalid 13 -> 11.8"
+
+echo ""
+echo "=== 6. With -b and --mariadb-version ==="
+MARIADB_VER="11.8"
+parse_mariadb_version "-b v2.5.5-dev --mariadb-version 12.1"
+assert_equals "12.1" "$MARIADB_VER" "-b v2.5.5-dev --mariadb-version 12.1"
+
+echo ""
+echo "=== 7. MariaDB.repo baseurl uses MARIADB_VER ==="
+MARIADB_VER="12.1"
+MARIADB_REPO="rhel9-amd64"
+baseurl="https://mirror.mariadb.org/yum/$MARIADB_VER/$MARIADB_REPO"
+assert_equals "https://mirror.mariadb.org/yum/12.1/rhel9-amd64" "$baseurl" "baseurl 12.1"
+MARIADB_VER="11.8"
+baseurl="https://mirror.mariadb.org/yum/$MARIADB_VER/$MARIADB_REPO"
+assert_equals "https://mirror.mariadb.org/yum/11.8/rhel9-amd64" "$baseurl" "baseurl 11.8"
+
+echo ""
+echo "=== 8. Script contains required logic ==="
+if [[ ! -f "$UPGRADE_SCRIPT" ]]; then
+  echo "FAIL: $UPGRADE_SCRIPT not found"
+  FAILED=1
+else
+  echo "OK: upgrade script exists"
+  grep -q 'MARIADB_VER="11.8"' "$UPGRADE_SCRIPT" && echo "OK: default MARIADB_VER" || { echo "FAIL: default MARIADB_VER"; FAILED=1; }
+  grep -q '/etc/cyberpanel/mariadb_version' "$UPGRADE_SCRIPT" && echo "OK: mariadb_version file" || { echo "FAIL: mariadb_version file"; FAILED=1; }
+fi
+
+echo ""
+if [[ $FAILED -eq 0 ]]; then
+  echo "All upgrader MariaDB version tests passed."
+  exit 0
+else
+  echo "Some tests failed."
+  exit 1
+fi
diff --git a/to-do/MARIADB-11.8-LTS-UPGRADE.md b/to-do/MARIADB-11.8-LTS-UPGRADE.md
index e6260c8ab..5946fb548 100644
--- a/to-do/MARIADB-11.8-LTS-UPGRADE.md
+++ b/to-do/MARIADB-11.8-LTS-UPGRADE.md
@@ -1,20 +1,34 @@
-# MariaDB 11.8 LTS (Long Term Service)
+# MariaDB 11.8 LTS and 12.1
 
 ## Summary
 
-CyberPanel install and upgrade now target **MariaDB 11.8 LTS** instead of 10.11 or 12.1.
+CyberPanel install and upgrade support **MariaDB 11.8 LTS** (default) or **12.1**. User can choose at install/upgrade time; **downgrade is supported** (e.g. 12.1 → 11.8 by re-running upgrader with `--mariadb-version 11.8`).
 
-- **New installs:** Use `mariadb_repo_setup --mariadb-server-version=11.8` and install from official MariaDB 11.8 repo.
-- **Upgrades:** Same; AlmaLinux 9 fix sets up 11.8 repo and installs MariaDB 11.8.
-- **cyberpanel_upgrade.sh:** Writes `/etc/yum.repos.d/MariaDB.repo` with `baseurl = https://mirror.mariadb.org/yum/11.8/$MARIADB_REPO`.
-- **UI (Database upgrade):** `databases/databaseManager.py` offers versions 10.6, 10.11, **11.8** for manual upgrade.
-- **mysqlUtilities.UpgradeMariaDB:** Still accepts version argument; repo baseurl uses `versionToInstall` (e.g. 11.8).
+- **New installs:** `--mariadb-version 11.8|12.1` (default 11.8); `install.py` and `venvsetup.sh` pass it through.
+- **Upgrades:** `cyberpanel_upgrade.sh --mariadb-version 11.8|12.1` or interactive prompt; writes `/etc/cyberpanel/mariadb_version` for `upgrade.py`.
+- **Downgrade:** Run upgrader again with the desired version (e.g. `--mariadb-version 11.8` to switch from 12.1 to 11.8). Repo and packages will target the chosen version.
+- **cyberpanel_upgrade.sh:** Uses `MARIADB_VER` (default 11.8) in `MariaDB.repo` baseurl and writes `/etc/cyberpanel/mariadb_version`.
+- **plogical/upgrade.py:** `fix_almalinux9_mariadb()` reads `/etc/cyberpanel/mariadb_version` (default 11.8) and runs `mariadb_repo_setup` with that version.
+- **UI (Database upgrade):** `databases/databaseManager.py` offers 10.6, 10.11, **11.8** for manual upgrade.
+- **mysqlUtilities.UpgradeMariaDB:** Repo baseurl uses `versionToInstall` (e.g. 11.8).
+
+## Testing
+
+From repo root:
+
+- Shell (upgrader argument parsing and repo URL logic):  
+  `./test/upgrader_mariadb_version_test.sh`
+- Python (mariadb_version file read and downgrade):  
+  `python3 test/test_upgrade_mariadb_version.py`
+
+Both 11.8 and 12.1 paths are tested; downgrade (12.1 → 11.8) is explicitly verified.
 
 ## References
 
-- `cyberpanel_upgrade.sh`: MariaDB.repo 11.8
-- `plogical/upgrade.py`: mariadb_repo_setup 11.8, fix_almalinux9_comprehensive()
-- `install/install.py`: mariadb_repo_setup 11.8, _attemptMariaDBUpgrade(), installMySQL(), disableMariaDB12RepositoryIfNeeded()
+- `cyberpanel_upgrade.sh`: MARIADB_VER, --mariadb-version, /etc/cyberpanel/mariadb_version
+- `plogical/upgrade.py`: fix_almalinux9_mariadb() reads mariadb_version file
+- `install/install.py`: --mariadb-version, preFlightsChecks.mariadb_version
+- `install/venvsetup.sh`: MARIADB_VER prompt, --mariadb-version to install.py
 - `install/universal_os_fixes.py`: setup_mariadb_repository() 11.8
 - `databases/databaseManager.py`: mysqlversions 10.6, 10.11, 11.8
 - `plogical/mysqlUtilities.py`: UpgradeMariaDB() baseurl for RHEL