diff --git a/multipass/run_parallel_iiab_test.sh b/multipass/run_parallel_iiab_test.sh
index 8a39dd4..bff400e 100644
--- a/multipass/run_parallel_iiab_test.sh
+++ b/multipass/run_parallel_iiab_test.sh
@@ -7,6 +7,7 @@
 #   --clean                      Stop+delete+purge target VMs (by BASE-<number>, regardless of COUNT)
 # Distro selection:
 #   --debian-13          Debian 13 only (sets IMAGE=$DEBIAN13_IMAGE_URL and BASE=deb13)
+#   --ubuntu-release VER Use specific Ubuntu release (e.g., 24.04, 26.04); sets IMAGE and BASE dynamically
 #   --both-distros       Run Ubuntu + Debian 13 in parallel: COUNT=N => 2N VMs (default order: interleaved)
 #   --first-ubuntu       (with --both-distros) order: all Ubuntu first, then all Debian
 #   --first-debian       (with --both-distros) order: all Debian first, then all Ubuntu
@@ -46,8 +47,8 @@ SCRIPT_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)"
 # Source: Debian cloud images live under cloud.debian.org/images/cloud/ ('genericcloud' includes cloud-init).
 DEBIAN13_IMAGE_URL="${DEBIAN13_IMAGE_URL:-https://cloud.debian.org/images/cloud/trixie/latest/debian-13-genericcloud-${DPKG_ARCH}.qcow2}"
 
-IMAGE="${IMAGE:-24.04}"
-BASE="${BASE:-ubu2404}"
+IMAGE="${IMAGE:-26.04}"
+BASE="${BASE:-ubu2604}"
 # cloud-init controls
 CLOUD_INIT_FILE="${CLOUD_INIT_FILE:-}"
 RPIOS_CLOUD_INIT_FILE="${RPIOS_CLOUD_INIT_FILE:-$SCRIPT_DIR/cloud-init-rpios-like-arm64.yaml}"
@@ -100,6 +101,7 @@ Aliases:
   --test-pr N                                     (same as --run-pr N)
 Image shortcuts:
   --debian-13   Use Debian 13 cloud image; sets IMAGE=\$DEBIAN13_IMAGE_URL and BASE=deb13
+  --ubuntu-release VER  Use specific Ubuntu release (e.g., 24.04, 26.04); sets IMAGE and BASE dynamically
   --both-distros  Run both Ubuntu + Debian 13 (COUNT=N => N + N VMs)
   --first-ubuntu  With --both-distros: run all Ubuntu first, then Debian
   --first-debian  With --both-distros: run all Debian first, then Ubuntu
@@ -132,6 +134,12 @@ while [[ $# -gt 0 ]]; do
       [[ $# -lt 2 ]] && { echo "[ERROR] --cloud-init needs a file path"; exit 2; }
       CLOUD_INIT_FILE="$2"; shift 2 ;;
 
+    --ubuntu-release)
+      [[ $# -lt 2 ]] && { echo "[ERROR] --ubuntu-release needs a version (e.g. 24.04 or 26.04)"; exit 2; }
+      IMAGE="$2"
+      BASE="ubu${2//./}"
+      shift 2 ;;
+
     --debian-13)
       DEBIAN13_ONLY=1
       IMAGE="$DEBIAN13_IMAGE_URL"
@@ -231,7 +239,9 @@ else
   DEB_BASE="deb13"
 fi
 
-LOGROOT="${LOGROOT:-iiab_multipass_runs_$(date +%Y%m%d)}"
+LOG_MONTH="$(date +%Y%m)"
+LOG_RUN="$(date +%Y%m%d_%H%M%S)"
+LOGROOT="${LOGROOT:-iiab_multipass_runs_${LOG_MONTH}/${LOG_RUN}}"
 mkdir -p "$LOGROOT"
 echo "[INFO] Logging files stored at: $LOGROOT"
 
@@ -346,15 +356,12 @@ clean_targets() {
   local list
   list="$(multipass list 2>/dev/null | awk 'NR>1 {print $1}' || true)"
 
+  # Regex modified to catch any Ubuntu base (ubu followed by 4 digits) or the Debian base
   if [[ "$BOTH_DISTROS" == "1" ]]; then
-    local ubu_re deb_re
-    ubu_re="$(re_escape "$UBU_BASE")"
     deb_re="$(re_escape "$DEB_BASE")"
-    printf '%s\n' "$list" | grep -E "^(${ubu_re}|${deb_re})-[0-9]+$" || true
+    printf '%s\n' "$list" | grep -E "^(ubu[0-9]{4}|${deb_re})-[0-9]+$" || true
   else
-    local base_re
-    base_re="$(re_escape "$BASE")"
-    printf '%s\n' "$list" | grep -E "^${base_re}-[0-9]+$" || true
+    printf '%s\n' "$list" | grep -E "^(ubu[0-9]{4}|deb13|rpios-d13)-[0-9]+$" || true
   fi
 }