diff --git a/bin/omarchy-dev-benchmark-theme-switcher b/bin/omarchy-dev-benchmark-theme-switcher
index b814025f..97460bed 100755
--- a/bin/omarchy-dev-benchmark-theme-switcher
+++ b/bin/omarchy-dev-benchmark-theme-switcher
@@ -19,7 +19,8 @@ Usage:
 
 Measure the non-interactive parts of the theme switcher:
 - theme preview index build (omarchy-theme-switcher before UI handoff)
-- image selector row/thumbnail cache prep (omarchy-menu-images --cache-only)
+- lazy selector row prep used by the interactive theme switcher
+- full thumbnail cache warmup cost (omarchy-menu-images --cache-only)
 
 Options:
   --repeat=<count>  Number of warm runs to measure for each case (default: 5)
@@ -100,6 +101,7 @@ if [[ ! $REPEAT =~ ^[0-9]+$ ]] || (( REPEAT < 1 )); then
 fi
 
 benchmark_cache=$(mktemp -d)
+thumbnail_cache=$(mktemp -d)
 stub_bin=$(mktemp -d)
 
 cleanup() {
@@ -107,8 +109,9 @@ cleanup() {
 
   if [[ $KEEP_CACHE == "true" ]]; then
     printf 'Benchmark cache: %s\n' "$benchmark_cache"
+    printf 'Thumbnail cache: %s\n' "$thumbnail_cache"
   else
-    rm -rf "$benchmark_cache"
+    rm -rf "$benchmark_cache" "$thumbnail_cache"
   fi
 }
 trap cleanup EXIT
@@ -126,20 +129,35 @@ benchmark_env=(
   "PATH=$stub_bin:$OMARCHY_BIN_DIR:$PATH"
 )
 
+thumbnail_env=(
+  env
+  "OMARCHY_PATH=$OMARCHY_PATH"
+  "XDG_CACHE_HOME=$thumbnail_cache"
+  "PATH=$stub_bin:$OMARCHY_BIN_DIR:$PATH"
+)
+
 preview_dir="$benchmark_cache/omarchy/theme-selector/previews"
+thumbnail_preview_dir="$thumbnail_cache/omarchy/theme-selector/previews"
 
 build_theme_index() {
   "${benchmark_env[@]}" "$OMARCHY_BIN_DIR/omarchy-theme-switcher"
 }
 
+prepare_selector_lazy() {
+  "${benchmark_env[@]}" "$OMARCHY_BIN_DIR/omarchy-menu-images" --prepare-only --lazy-thumbnails --show-labels --filterable "$preview_dir"
+}
+
 prepare_image_cache() {
-  "${benchmark_env[@]}" "$OMARCHY_BIN_DIR/omarchy-menu-images" --cache-only "$preview_dir"
+  "${thumbnail_env[@]}" "$OMARCHY_BIN_DIR/omarchy-menu-images" --cache-only "$thumbnail_preview_dir"
 }
 
 printf 'Theme switcher benchmark (%d warm runs each)\n\n' "$REPEAT"
 printf '%-34s %s ms\n' "theme index cold" "$(format_ms "$(measure_once build_theme_index)")"
 run_case "theme index warm" build_theme_index
-printf '%-34s %s ms\n' "selector cache cold" "$(format_ms "$(measure_once prepare_image_cache)")"
-run_case "selector cache warm" prepare_image_cache
+printf '%-34s %s ms\n' "selector prep cold (lazy)" "$(format_ms "$(measure_once prepare_selector_lazy)")"
+run_case "selector prep warm (lazy)" prepare_selector_lazy
+"${thumbnail_env[@]}" "$OMARCHY_BIN_DIR/omarchy-theme-switcher" >/dev/null
+printf '%-34s %s ms\n' "thumbnail cache cold" "$(format_ms "$(measure_once prepare_image_cache)")"
+run_case "thumbnail cache warm" prepare_image_cache
 
 printf '\nTheme previews: %d\n' "$(find -L "$preview_dir" -maxdepth 1 -type f 2>/dev/null | wc -l)"
diff --git a/bin/omarchy-menu-images b/bin/omarchy-menu-images
index 86369daf..970f9392 100755
--- a/bin/omarchy-menu-images
+++ b/bin/omarchy-menu-images
@@ -1,7 +1,7 @@
 #!/bin/bash
 
 # omarchy:summary=Open a generic image selector menu
-# omarchy:args=[--selected <image>] [--colors-file <path>] [--print-name] [--show-labels] [--filterable] [--cache-only] <image-dir>...
+# omarchy:args=[--selected <image>] [--colors-file <path>] [--print-name] [--show-labels] [--filterable] [--lazy-thumbnails] [--cache-only] <image-dir>...
 
 OMARCHY_PATH=${OMARCHY_PATH:-$HOME/.local/share/omarchy}
 
@@ -10,11 +10,13 @@ colors_file=""
 print_name=false
 show_labels=false
 filterable=false
+lazy_thumbnails=false
+prepare_only=false
 cache_only=false
 image_dirs=()
 
 usage() {
-  echo "Usage: omarchy-menu-images [--selected <image>] [--colors-file <path>] [--print-name] [--show-labels] [--filterable] [--cache-only] <image-dir>..."
+  echo "Usage: omarchy-menu-images [--selected <image>] [--colors-file <path>] [--print-name] [--show-labels] [--filterable] [--lazy-thumbnails] [--cache-only] <image-dir>..."
 }
 
 while [[ $# -gt 0 ]]; do
@@ -49,6 +51,14 @@ while [[ $# -gt 0 ]]; do
       filterable=true
       shift
       ;;
+    --lazy-thumbnails)
+      lazy_thumbnails=true
+      shift
+      ;;
+    --prepare-only)
+      prepare_only=true
+      shift
+      ;;
     --cache-only)
       cache_only=true
       shift
@@ -108,7 +118,8 @@ mkdir -p "$cache_dir"
 cache_key=$(printf '%s' "$image_dirs_env" | md5sum | cut -d ' ' -f 1)
 rows_cache_file="$cache_dir/$cache_key.rows"
 rows_signature_file="$cache_dir/$cache_key.signature"
-rows_signature=""
+rows_signature="v2"$'\n'
+rows_cacheable=true
 image_files=()
 
 for dir in "${image_dirs[@]}"; do
@@ -123,6 +134,29 @@ for dir in "${image_dirs[@]}"; do
   fi
 done
 
+generate_thumbnail() {
+  local image="$1"
+  local thumbnail="$2"
+  local lock="$thumbnail.lock"
+  local tmp="$thumbnail.$$.jpg"
+
+  if mkdir "$lock" 2>/dev/null; then
+    if magick "${image}[0]" -auto-orient -resize '1536x864^' -gravity center -extent '1536x864' -strip -quality 82 "$tmp"; then
+      mv -f "$tmp" "$thumbnail"
+    else
+      rm -f "$tmp" "$thumbnail"
+    fi
+
+    rmdir "$lock" 2>/dev/null || true
+  else
+    for ((i = 0; i < 3000; i++)); do
+      [[ -f $thumbnail ]] && return
+      [[ -d $lock ]] || break
+      sleep 0.01
+    done
+  fi
+}
+
 thumbnail_for() {
   local image="$1"
   local signature hash thumbnail
@@ -131,14 +165,25 @@ thumbnail_for() {
   hash=$(awk -F '\t' -v path="$image" -v sig="$signature" '$1 == path && $2 == sig { print $3; exit }' "$index_file" 2>/dev/null)
 
   if [[ -z $hash ]]; then
-    hash=$(md5sum "$image" | cut -d ' ' -f 1)
+    hash=$(printf '%s\t%s' "$image" "$signature" | md5sum | cut -d ' ' -f 1)
     printf '%s\t%s\t%s\n' "$image" "$signature" "$hash" >>"$index_file"
   fi
 
   thumbnail="$cache_dir/$hash.jpg"
 
   if [[ ! -f $thumbnail ]]; then
-    magick "${image}[0]" -auto-orient -resize '1536x864^' -gravity center -extent '1536x864' -strip -quality 82 "$thumbnail"
+    if [[ $lazy_thumbnails == true && $cache_only != true ]]; then
+      rows_cacheable=false
+
+      if [[ $prepare_only != true ]]; then
+        generate_thumbnail "$image" "$thumbnail" >/dev/null 2>&1 &
+      fi
+
+      printf '%s' "$image"
+      return
+    fi
+
+    generate_thumbnail "$image" "$thumbnail"
   fi
 
   [[ -f $thumbnail ]] && printf '%s' "$thumbnail"
@@ -150,6 +195,9 @@ else
   for image in "${image_files[@]}"; do
     thumbnail=$(thumbnail_for "$image")
     [[ -n $thumbnail ]] || continue
+    if [[ $lazy_thumbnails == true && $cache_only != true && $thumbnail == "$image" ]]; then
+      rows_cacheable=false
+    fi
 
     if [[ -z $rows ]]; then
       rows="$image"$'\t'"$thumbnail"
@@ -158,8 +206,12 @@ else
     fi
   done
 
-  printf '%s' "$rows" >"$rows_cache_file"
-  printf '%s' "$rows_signature" >"$rows_signature_file"
+  if [[ $rows_cacheable == true ]]; then
+    printf '%s' "$rows" >"$rows_cache_file"
+    printf '%s' "$rows_signature" >"$rows_signature_file"
+  else
+    rm -f "$rows_cache_file" "$rows_signature_file"
+  fi
 fi
 
 rows_payload=${rows//$'\t'/$'\f'}
@@ -173,7 +225,7 @@ if [[ -f $colors_file ]]; then
   colors_payload=${colors_payload//$'\n'/$'\v'}
 fi
 
-if [[ $cache_only == true ]]; then
+if [[ $cache_only == true || $prepare_only == true ]]; then
   exit 0
 fi
 
diff --git a/bin/omarchy-theme-switcher b/bin/omarchy-theme-switcher
index 2b3209ec..4a1e55e5 100755
--- a/bin/omarchy-theme-switcher
+++ b/bin/omarchy-theme-switcher
@@ -93,5 +93,6 @@ exec omarchy-menu-images \
   --print-name \
   --show-labels \
   --filterable \
+  --lazy-thumbnails \
   --selected "$selected_preview" \
   "$preview_dir"