diff --git a/scripts/on-device-install/README.md b/scripts/on-device-install/README.md
index 2619fa28..777bde46 100644
--- a/scripts/on-device-install/README.md
+++ b/scripts/on-device-install/README.md
@@ -177,9 +177,16 @@ redirect to discover the newest tag. If that lookup fails (offline, or a `curl`
 build without `-w` support), it falls back to a pinned version baked into the
 script.
 
-> **Tip — rollback:** if the new binary misbehaves, the installer left a `.backup` file alongside it:
+> **Tip — rollback:** if the new binary misbehaves, the installer left a backup file
+> alongside it, gzip-compressed as `.backup.gz` (plain `.backup`, uncompressed, if
+> `gzip` wasn't available on your device):
 > ```bash
-> ls /mnt/nv/aftertouch/aftertouch-service*.backup
+> ls /mnt/nv/aftertouch/aftertouch-service*.backup*
+> # .backup.gz (compressed):
+> gunzip -c /mnt/nv/aftertouch/aftertouch-service.<old-version>.backup.gz \
+>    > /mnt/nv/aftertouch/aftertouch-service
+> chmod +x /mnt/nv/aftertouch/aftertouch-service
+> # or, for an uncompressed .backup:
 > cp /mnt/nv/aftertouch/aftertouch-service.<old-version>.backup \
 >    /mnt/nv/aftertouch/aftertouch-service
 > /etc/init.d/aftertouch restart
diff --git a/scripts/on-device-install/install.sh b/scripts/on-device-install/install.sh
index 01461810..774ad2cd 100644
--- a/scripts/on-device-install/install.sh
+++ b/scripts/on-device-install/install.sh
@@ -97,6 +97,7 @@ fi
 # prior run was interrupted.
 echo "Disk usage before pre-install GC:"; df -h "$INSTALL_DIR"
 for f in "$INSTALL_DIR/aftertouch-service".*.backup \
+          "$INSTALL_DIR/aftertouch-service".*.backup.gz \
           "$INSTALL_DIR/aftertouch-service".*.old \
           "$INSTALL_DIR/aftertouch-service.new"; do
   [ -f "$f" ] || continue
@@ -121,8 +122,24 @@ if [ -f "$INSTALL_DIR/aftertouch-service" ]; then
   if [ -z "$current_version" ] || [ "$current_version" = "dev" ]; then
     current_version=$(date +%Y%m%d-%H%M%S)
   fi
+  # Binaries are tens of MB and only growing (see #614 investigation into
+  # Go 1.27's default binary-size increase), while /mnt/nv is small (tens of
+  # MB total). Stream straight into the compressed file rather than cp-then-
+  # gzip: at this point in the script the old binary is still live AND the
+  # newly-downloaded one is already sitting in $UPDATE_TMP_DIR, so an
+  # intermediate uncompressed backup copy would briefly need all three full
+  # copies on disk at once -- exactly the kind of moment that has already
+  # caused "no space left on device" failures here. Best effort: if gzip is
+  # missing, or the stream fails partway (e.g. disk fills mid-compress),
+  # fall back to a plain uncompressed copy exactly as before.
   BACKUP_FILE="$INSTALL_DIR/aftertouch-service.${current_version}.backup"
-  cp -p "$INSTALL_DIR/aftertouch-service" "$BACKUP_FILE"
+  if command -v gzip >/dev/null 2>&1 \
+      && gzip -c < "$INSTALL_DIR/aftertouch-service" > "$BACKUP_FILE.gz"; then
+    BACKUP_FILE="$BACKUP_FILE.gz"
+  else
+    rm -f "$BACKUP_FILE.gz"
+    cp -p "$INSTALL_DIR/aftertouch-service" "$BACKUP_FILE"
+  fi
   echo "Backed up current binary ($current_version) → $BACKUP_FILE"
 fi
 
@@ -136,6 +153,7 @@ chmod +x "$INSTALL_DIR/aftertouch-service"
 if [ -n "$BACKUP_FILE" ]; then
   echo "Disk usage before post-install GC:"; df -h "$INSTALL_DIR"
   for f in "$INSTALL_DIR/aftertouch-service".*.backup \
+            "$INSTALL_DIR/aftertouch-service".*.backup.gz \
             "$INSTALL_DIR/aftertouch-service".*.old \
             "$INSTALL_DIR/aftertouch-service.new"; do
     [ -f "$f" ] || continue