diff --git a/src/init.sh b/src/init.sh
index b45ff5c..3593cdd 100755
--- a/src/init.sh
+++ b/src/init.sh
@@ -65,14 +65,23 @@ visibility = ["//visibility:public"],
 )
 _EOB
 
+case "$BRANCH_NAME" in
+  "lineage-19.1" | "lineage-20.0" | "lineage-21.0" )
+    build_file="new_build.sh"
+    ;;
+  * )
+    build_file="legacy-build.sh"
+    ;;
+esac
+
 if [ "$CRONTAB_TIME" = "now" ]; then
-  /root/build.sh
+  /root/$build_file
 else
   # Initialize the cronjob
   cronFile=/tmp/buildcron
   printf "SHELL=/bin/bash\n" > $cronFile
   printenv -0 | sed -e 's/=\x0/=""\n/g'  | sed -e 's/\x0/\n/g' | sed -e "s/_=/PRINTENV=/g" >> $cronFile
-  printf '\n%s /usr/bin/flock -n /var/lock/build.lock /root/build.sh >> /var/log/docker.log 2>&1\n' "$CRONTAB_TIME" >> $cronFile
+  printf "\n%s /usr/bin/flock -n /var/lock/build.lock /root/$build_file >> /var/log/docker.log 2>&1\n" "$CRONTAB_TIME" >> $cronFile
   crontab $cronFile
   rm $cronFile
 
diff --git a/src/build.sh b/src/legacy-build.sh
similarity index 100%
rename from src/build.sh
rename to src/legacy-build.sh
diff --git a/src/new_build.sh b/src/new_build.sh
new file mode 100755
index 0000000..f06e95e
--- /dev/null
+++ b/src/new_build.sh
@@ -0,0 +1,485 @@
+#!/bin/bash
+
+# Slimmed-down Docker build script
+# Copyright (c) 2017 Julian Xhokaxhiu
+# Copyright (C) 2017-2018 Nicola Corna <nicola@corna.info>
+# Copyright (C) 2024 Pete Fotheringham <petefoth@e.email>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>
+
+
+# Outline
+# - Call `begin.sh`
+# - Handle parameters and environment variables
+#      -  CLEAN_OUTDIR
+#      -  PARALLEL_JOBS
+#      -  RETRY_FETCHES
+# - Branch-specific stuff
+# - handle local manifests
+# - Sync mirror if we're using one
+# -  main sync and build loop
+#    For each device in `$DEVICE_LIST`
+#     - setup subdirectories
+#     - `repo init`
+#     - `repo sync`
+#     - setup our overlays
+#     - Set RELEASE_TYPE
+#     - Handle OTA_URL
+#     - Add custom packages to be installed
+#     - Handle keys
+#     - Prepare the environment
+#     - Call `before.sh`
+#     - `breakfast` - in case of failure, call
+#         - `post-build.sh`
+#         - `do_cleanup`
+#     - Call `pre-build.sh`
+#     - Call `mka`
+#     - move artefacts to `ZIPDIR`
+#         - ROM zip file
+#         - `.img` files
+#         - create the checksum files
+#         - Remove old zips and logs
+#     - call `post-build.sh`
+#     - call `do_cleanup`
+# - call `end.sh`
+
+# do_cleanup function
+do_cleanup() {
+  echo ">> [$(date)] Cleaning up" | tee -a "$DEBUG_LOG"
+
+  if [ "$BUILD_OVERLAY" = true ]; then
+    # The Jack server must be stopped manually, as we want to unmount $TMP_DIR/merged
+    cd "$TMP_DIR"
+    if [ -f "$TMP_DIR/merged/prebuilts/sdk/tools/jack-admin" ]; then
+      "$TMP_DIR/merged/prebuilts/sdk/tools/jack-admin kill-server" &> /dev/null || true
+    fi
+    lsof | grep "$TMP_DIR/merged" | awk '{ print $2 }' | sort -u | xargs -r kill &> /dev/null || true
+
+    while lsof | grep -q "$TMP_DIR"/merged; do
+      sleep 1
+    done
+
+    umount "$TMP_DIR/merged"
+  fi
+
+  if [ "$CLEAN_AFTER_BUILD" = true ]; then
+    echo ">> [$(date)] Cleaning source dir for device $codename" | tee -a "$DEBUG_LOG"
+    if [ "$BUILD_OVERLAY" = true ]; then
+      cd "$TMP_DIR"
+      rm -rf ./* || true
+    else
+      cd "$source_dir"
+      (set +eu ; mka "${jobs_arg[@]}" clean) &>> "$DEBUG_LOG"
+    fi
+  fi
+}
+
+# Build script
+
+set -eEuo pipefail
+repo_log="$LOGS_DIR/repo-$(date +%Y%m%d).log"
+
+# cd to working directory
+cd "$SRC_DIR"
+
+# Call `begin.sh`
+if [ -f /root/userscripts/begin.sh ]; then
+  echo ">> [$(date)] Running begin.sh"
+  /root/userscripts/begin.sh || { echo ">> [$(date)] Error: begin.sh failed!"; exit 1; }
+fi
+
+# Handle parameters and environment variables
+branch=$BRANCH_NAME
+echo ">> [$(date)] Branch:  $branch"
+
+devices=$DEVICE_LIST
+echo ">> [$(date)] Devices: $devices"
+
+vendor=lineage
+
+## Check for non-working environment variable values
+if [ "$LOCAL_MIRROR" = true ]; then
+  echo "Using LOCAL_MIRROR is not yet working"
+  exit 1
+fi
+
+if [ "$BUILD_OVERLAY" = true ]; then
+  echo "Using BUILD_OVERLAY is not yet working"
+  exit 1
+fi
+
+## CLEAN_OUTDIR
+if [ "$CLEAN_OUTDIR" = true ]; then
+ echo ">> [$(date)] Cleaning '$ZIP_DIR'"
+ rm -rf "${ZIP_DIR:?}/"*
+fi
+
+## PARALLEL_JOBS
+jobs_arg=()
+if [ -n "${PARALLEL_JOBS-}" ]; then
+  if [[ "$PARALLEL_JOBS" =~ ^[1-9][0-9]*$ ]]; then
+    jobs_arg+=( "-j$PARALLEL_JOBS" )
+  else
+    echo "PARALLEL_JOBS is not a positive number: $PARALLEL_JOBS"
+    exit 1
+  fi
+fi
+
+## RETRY_FETCHES
+retry_fetches_arg=()
+if [ -n "${RETRY_FETCHES-}" ]; then
+  if [[ "$RETRY_FETCHES" =~ ^[1-9][0-9]*$ ]]; then
+    retry_fetches_arg+=( "--retry-fetches=$RETRY_FETCHES" )
+  else
+    echo "RETRY_FETCHES is not a positive number: $RETRY_FETCHES"
+    exit 1
+  fi
+fi
+
+# Branch-specific stuff
+branch_dir=${branch//[^[:alnum:]]/_}
+branch_dir=${branch_dir^^}
+
+mkdir -p "$SRC_DIR/$branch_dir"
+cd "$SRC_DIR/$branch_dir"
+
+if [ -n "$branch" ] && [ -n "$devices" ]; then
+  case "$branch" in
+    lineage-19.1*)
+      themuppets_branch="lineage-19.1"
+      android_version="12"
+      ;;
+    lineage-20.0*)
+      themuppets_branch="lineage-20.0"
+      android_version="13"
+      ;;
+    lineage-21.0*)
+      themuppets_branch="lineage-21.0"
+      android_version="14"
+      ;;
+    *)
+      echo ">> [$(date)] Building branch $branch is not (yet) suppported"
+      exit 1
+      ;;
+    esac
+    android_version_major=$(cut -d '.' -f 1 <<< $android_version)
+fi
+
+# Handle local manifests
+## Copy local manifests
+echo ">> [$(date)] Copying '$LMANIFEST_DIR/*.xml' to '.repo/local_manifests/'"
+mkdir -p .repo/local_manifests
+rsync -a --delete --include '*.xml' --exclude '*' "$LMANIFEST_DIR/" .repo/local_manifests/
+
+## Pick up TheMuppets manifest if required
+rm -f .repo/local_manifests/proprietary.xml
+if [ "$INCLUDE_PROPRIETARY" = true ]; then
+  wget -q -O .repo/local_manifests/proprietary.xml "https://raw.githubusercontent.com/TheMuppets/manifests/$themuppets_branch/muppets.xml"
+  /root/build_manifest.py --remote "https://gitlab.com" --remotename "gitlab_https" \
+    "https://gitlab.com/the-muppets/manifest/raw/$themuppets_branch/muppets.xml" .repo/local_manifests/proprietary_gitlab.xml
+fi
+
+# Sync mirror if we're using one
+if [ "$LOCAL_MIRROR" = true ]; then
+  echo "Using LOCAL_MIRROR is not yet working"
+
+  # cd "$MIRROR_DIR"
+  # if [ "$INIT_MIRROR" = true ]; then
+  #   if [ ! -d .repo ]; then
+  #     echo ">> [$(date)] Initializing mirror repository" | tee -a "$repo_log"
+  #     ( yes||: ) | repo init -u https://github.com/LineageOS/mirror --mirror --no-clone-bundle -p linux --git-lfs &>> "$repo_log"
+  #   fi
+  # else
+  #   echo ">> [$(date)] Initializing mirror repository disabled" | tee -a "$repo_log"
+  # fi
+  # if [ "$SYNC_MIRROR" = true ]; then
+  #   echo ">> [$(date)] Syncing mirror repository" | tee -a "$repo_log"
+  #   repo sync "${jobs_arg[@]}" "${retry_fetches_arg[@]}" --force-sync --no-clone-bundle &>> "$repo_log"
+  #
+  # else
+  #   echo ">> [$(date)] Sync mirror repository disabled" | tee -a "$repo_log"
+  # fi
+fi
+
+
+# -  main sync and build loop
+#    For each device in `$DEVICE_LIST`
+for codename in ${devices//,/ }; do
+  if [ -n "$codename" ]; then
+    builddate=$(date +%Y%m%d)
+
+    # setup subdirectories
+    if [ "$ZIP_SUBDIR" = true ]; then
+      zipsubdir=$codename
+      mkdir -p "$ZIP_DIR/$zipsubdir"
+    else
+      zipsubdir=
+    fi
+    if [ "$LOGS_SUBDIR" = true ]; then
+      logsubdir=$codename
+      mkdir -p "$LOGS_DIR/$logsubdir"
+    else
+      logsubdir=
+    fi
+
+  # `repo init`
+  if [ "$CALL_REPO_INIT" = true ]; then
+    echo ">> [$(date)] (Re)initializing branch repository" | tee -a "$repo_log"
+    if [ "$LOCAL_MIRROR" = true ]; then
+      ( yes||: ) | repo init -u https://github.com/LineageOS/android.git --reference "$MIRROR_DIR" -b "$branch" -g default,-darwin,-muppets,muppets_"${codename}" --git-lfs &>> "$repo_log"
+    else
+      ( yes||: ) | repo init -u https://github.com/LineageOS/android.git -b "$branch" -g default,-darwin,-muppets,muppets_"${codename}" --git-lfs &>> "$repo_log"
+    fi
+  else
+    echo ">> [$(date)] Calling repo init disabled"
+  fi
+
+  # `repo sync`
+  if [ "$CALL_REPO_SYNC" = true ]; then
+    echo ">> [$(date)] Syncing branch repository" | tee -a "$repo_log"
+    repo sync "${jobs_arg[@]}" "${retry_fetches_arg[@]}" --current-branch --force-sync &>> "$repo_log"
+  else
+    echo ">> [$(date)] Syncing branch repository disabled" | tee -a "$repo_log"
+  fi
+
+  if [ "$CALL_GIT_LFS_PULL" = true ]; then
+    echo ">> [$(date)] Calling git lfs pull" | tee -a "$repo_log"
+    repo forall -v -c git lfs pull &>> "$repo_log"
+  else
+    echo ">> [$(date)] Calling git lfs pull disabled" | tee -a "$repo_log"
+  fi
+
+  if [ ! -d "vendor/$vendor" ]; then
+    echo ">> [$(date)] Missing \"vendor/$vendor\", aborting"
+    exit 1
+  fi
+
+  # Setup our overlays
+    if [ "$BUILD_OVERLAY" = true ]; then
+      echo "Using BUILD_OVERLAY is not yet working"
+      exit 1
+
+      # lowerdir=$SRC_DIR/$branch_dir
+      # upperdir=$TMP_DIR/device
+      # workdir=$TMP_DIR/workdir
+      # merged=$TMP_DIR/merged
+      # mkdir -p "$upperdir" "$workdir" "$merged"
+      # mount -t overlay overlay -o lowerdir="$lowerdir",upperdir="$upperdir",workdir="$workdir" "$merged"
+      # source_dir="$TMP_DIR/merged"
+    else
+      source_dir="$SRC_DIR/$branch_dir"
+    fi
+
+    mkdir -p "vendor/$vendor/overlay/microg/"
+    sed -i "1s;^;PRODUCT_PACKAGE_OVERLAYS := vendor/$vendor/overlay/microg\n;" "vendor/$vendor/config/common.mk"
+
+    makefile_containing_version="vendor/$vendor/config/common.mk"
+    if [ -f "vendor/$vendor/config/version.mk" ]; then
+      makefile_containing_version="vendor/$vendor/config/version.mk"
+    fi
+    los_ver_major=$(sed -n -e 's/^\s*PRODUCT_VERSION_MAJOR = //p' "$makefile_containing_version")
+    los_ver_minor=$(sed -n -e 's/^\s*PRODUCT_VERSION_MINOR = //p' "$makefile_containing_version")
+    los_ver="$los_ver_major.$los_ver_minor"
+
+    DEBUG_LOG="$LOGS_DIR/$logsubdir/lineage-$los_ver-$builddate-$RELEASE_TYPE-$codename.log"
+
+    # Set RELEASE_TYPE
+    echo ">> [$(date)] Setting \"$RELEASE_TYPE\" as release type"
+    sed -i "/\$(filter .*\$(${vendor^^}_BUILDTYPE)/,/endif/d" "$makefile_containing_version"
+
+    # Set a custom updater URI if a OTA URL is provided
+    echo ">> [$(date)] Adding OTA URL overlay (for custom URL $OTA_URL)"
+    if [ -n "$OTA_URL" ]; then
+      if [ -d "packages/apps/Updater/app/src/main/res/values" ]; then
+        # "New" Updater project structure
+        updater_values_dir="packages/apps/Updater/app/src/main/res/values"
+      elif [ -d "packages/apps/Updater/res/values" ]; then
+        # "Old" Updater project structure
+        updater_values_dir="packages/apps/Updater/res/values"
+      else
+        echo ">> [$(date)] ERROR: no 'values' dir of Updater app found"
+        exit 1
+      fi
+
+      updater_url_overlay_dir="vendor/$vendor/overlay/microg/${updater_values_dir}/"
+      mkdir -p "$updater_url_overlay_dir"
+
+      if grep -q updater_server_url ${updater_values_dir}/strings.xml; then
+        # "New" updater configuration: full URL (with placeholders {device}, {type} and {incr})
+        sed "s|{name}|updater_server_url|g; s|{url}|$OTA_URL/v1/{device}/{type}/{incr}|g" /root/packages_updater_strings.xml > "$updater_url_overlay_dir/strings.xml"
+      elif grep -q conf_update_server_url_def ${updater_values_dir}/strings.xml; then
+        # "Old" updater configuration: just the URL
+        sed "s|{name}|conf_update_server_url_def|g; s|{url}|$OTA_URL|g" /root/packages_updater_strings.xml > "$updater_url_overlay_dir/strings.xml"
+      else
+        echo ">> [$(date)] ERROR: no known Updater URL property found"
+        exit 1
+      fi
+    fi
+
+    # Add custom packages to be installed
+    if [ -n "$CUSTOM_PACKAGES" ]; then
+      echo ">> [$(date)] Adding custom packages ($CUSTOM_PACKAGES)"
+      sed -i "1s;^;PRODUCT_PACKAGES += $CUSTOM_PACKAGES\n\n;" "vendor/$vendor/config/common.mk"
+    fi
+
+    # Handle keys
+    if [ "$SIGN_BUILDS" = true ]; then
+      echo ">> [$(date)] Adding keys path ($KEYS_DIR)"
+      # Soong (Android 9+) complains if the signing keys are outside the build path
+      ln -sf "$KEYS_DIR" user-keys
+      if [ "$android_version_major" -lt "10" ]; then
+        sed -i "1s;^;PRODUCT_DEFAULT_DEV_CERTIFICATE := user-keys/releasekey\nPRODUCT_OTA_PUBLIC_KEYS := user-keys/releasekey\nPRODUCT_EXTRA_RECOVERY_KEYS := user-keys/releasekey\n\n;" "vendor/$vendor/config/common.mk"
+      fi
+
+      if [ "$android_version_major" -ge "10" ]; then
+        sed -i "1s;^;PRODUCT_DEFAULT_DEV_CERTIFICATE := user-keys/releasekey\nPRODUCT_OTA_PUBLIC_KEYS := user-keys/releasekey\n\n;" "vendor/$vendor/config/common.mk"
+      fi
+    fi
+
+    # Prepare the environment
+    if [ "$PREPARE_BUILD_ENVIRONMENT" = true ]; then
+      echo ">> [$(date)] Preparing build environment"
+      set +eu
+      # shellcheck source=/dev/null
+      source build/envsetup.sh > /dev/null
+      set -eu
+    else
+      echo ">> [$(date)] Preparing build environment disabled"
+    fi
+
+    userscriptfail=false
+
+    # Call `before.sh`
+    if [ -f /root/userscripts/before.sh ]; then
+      echo ">> [$(date)] Running before.sh"
+      echo "before.sh is now called *after* repo sync."
+      echo "In previous versions, iot was called *before* repo sync"
+      /root/userscripts/before.sh || { echo ">> [$(date)] Error: before.sh failed for $branch!"; userscriptfail=true; continue; }
+    fi
+
+    # Call breakfast
+    breakfast_returncode=0
+    if [ "$CALL_BREAKFAST" = true ]; then
+      set +eu
+      breakfast "$codename" "$BUILD_TYPE" &>> "$DEBUG_LOG"
+      breakfast_returncode=$?
+      set -eu
+    else
+      echo ">> [$(date)] Calling breakfast disabled"
+    fi
+
+    if [ $breakfast_returncode -ne 0 ]; then
+        echo ">> [$(date)] breakfast failed for $codename, $branch branch" | tee -a "$DEBUG_LOG"
+        # call post-build.sh so the failure is logged in a way that is more visible
+        if [ -f /root/userscripts/post-build.sh ]; then
+          echo ">> [$(date)] Running post-build.sh for $codename" >> "$DEBUG_LOG"
+          /root/userscripts/post-build.sh "$codename" false "$branch" &>> "$DEBUG_LOG" || echo ">> [$(date)] Warning: post-build.sh failed!"
+        fi
+        do_cleanup
+        continue
+    fi
+
+    # Call pre-build.sh
+    if [ -f /root/userscripts/pre-build.sh ]; then
+      echo ">> [$(date)] Running pre-build.sh for $codename" >> "$DEBUG_LOG"
+      /root/userscripts/pre-build.sh "$codename" &>> "$DEBUG_LOG" || {
+        echo ">> [$(date)] Error: pre-build.sh failed for $codename on $branch!"; userscriptfail=true; continue; }
+    fi
+
+    # Call mka
+    build_successful=true
+    if [ "$CALL_MKA" = true ]; then
+      # Start the build
+      echo ">> [$(date)] Starting build for $codename, $branch branch" | tee -a "$DEBUG_LOG"
+      build_successful=false
+      files_to_hash=()
+
+      if (set +eu ; mka "${jobs_arg[@]}" target-files-package bacon) &>> "$DEBUG_LOG"; then
+        echo ">> [$(date)] Moving build artifacts for $codename to '$ZIP_DIR/$zipsubdir'" | tee -a "$DEBUG_LOG"
+
+        # Move the ROM zip files to the main OUT directory
+        cd out/target/product/"$codename"
+        files_to_hash=()
+        for build in lineage-*.zip; do
+          cp -v system/build.prop "$ZIP_DIR/$zipsubdir/$build.prop" &>> "$DEBUG_LOG"
+          mv "$build" "$ZIP_DIR/$zipsubdir/" &>> "$DEBUG_LOG"
+          files_to_hash+=( "$build" )
+        done
+
+        # Now handle the .img files - where are they?
+        img_dir=$(find "$source_dir/out/target/product/$codename/obj/PACKAGING" -name "IMAGES")
+        if [ -d "$img_dir" ]; then
+          cd "$img_dir"
+        fi
+
+        # rename and copy the images to the zips directory
+        for image in recovery boot vendor_boot dtbo super_empty vbmeta vendor_kernel_boot init_boot; do
+          if [ -f "$image.img" ]; then
+            recovery_name="lineage-$los_ver-$builddate-$RELEASE_TYPE-$codename-$image.img"
+            echo ">> [$(date)] Copying $image.img" to "$ZIP_DIR/$zipsubdir/$recovery_name" >> "$DEBUG_LOG"
+            cp "$image.img" "$ZIP_DIR/$zipsubdir/$recovery_name" &>> "$DEBUG_LOG"
+            files_to_hash+=( "$recovery_name" )
+          fi
+        done
+
+        # create the checksum files
+        cd "$ZIP_DIR/$zipsubdir"
+        for f in "${files_to_hash[@]}"; do
+          sha256sum "$f" > "$ZIP_DIR/$zipsubdir/$f.sha256sum"
+        done
+        cd "$source_dir"
+        build_successful=true
+      else
+        echo ">> [$(date)] Failed build for $codename" | tee -a "$DEBUG_LOG"
+      fi
+
+      # Remove old zips and logs
+      if [ "$DELETE_OLD_ZIPS" -gt "0" ]; then
+        if [ "$ZIP_SUBDIR" = true ]; then
+          /usr/bin/python /root/clean_up.py -n "$DELETE_OLD_ZIPS" -V "$los_ver" -N 1 "$ZIP_DIR/$zipsubdir"
+        else
+          /usr/bin/python /root/clean_up.py -n "$DELETE_OLD_ZIPS" -V "$los_ver" -N 1 -c "$codename" "$ZIP_DIR"
+        fi
+      fi
+      if [ "$DELETE_OLD_LOGS" -gt "0" ]; then
+        if [ "$LOGS_SUBDIR" = true ]; then
+          /usr/bin/python /root/clean_up.py -n "$DELETE_OLD_LOGS" -V "$los_ver" -N 1 "$LOGS_DIR/$logsubdir"
+        else
+          /usr/bin/python /root/clean_up.py -n "$DELETE_OLD_LOGS" -V "$los_ver" -N 1 -c "$codename" "$LOGS_DIR"
+        fi
+      fi
+    else
+      echo ">> [$(date)] Calling mka for $codename, $branch branch disabled"
+    fi
+
+    # call post-build.sh
+    if [ -f /root/userscripts/post-build.sh ]; then
+      echo ">> [$(date)] Running post-build.sh for $codename" >> "$DEBUG_LOG"
+      /root/userscripts/post-build.sh "$codename" "$build_successful" "$branch" &>> "$DEBUG_LOG" || {
+        echo ">> [$(date)] Error: post-build.sh failed for $codename on $branch!"; userscriptfail=true; }
+    fi
+    echo ">> [$(date)] Finishing build for $codename" | tee -a "$DEBUG_LOG"
+
+    do_cleanup
+    if [ "$userscriptfail" = true ]; then
+      echo ">> [$(date)] One or more userscripts failed!"
+      exit 1
+    fi
+  fi
+done
+
+if [ -f /root/userscripts/end.sh ]; then
+  echo ">> [$(date)] Running end.sh"
+  /root/userscripts/end.sh || echo ">> [$(date)] Error: end.sh failed!"
+fi