diff --git a/AGENTS.md b/AGENTS.md
index 7cba058..695972e 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -51,10 +51,12 @@ CSS file (Gruvbox, light + dark, theme toggle without reload).
 - **Dates**: all visible dates (post cards, garden table) are rendered by the generator's
   `dateText()` helper as `Fri 2026-08-28` (English weekday + ISO date); `blog_data.date`
   stays ISO for sorting, `blog_data.dateText` is added for display. JSON-LD keeps ISO dates.
-- **Thumbnails** (`thumbSrc()`): prefer a child note of the article titled `*_thumb.*`
-  (e.g. `ngc281_thumb.jpg`) → `api/notes/<id>/download`; otherwise use the first `<img>`
-  from the note content. Layout: image left, summary right (`.blog-post-inner`),
-  `max-height:256px`, lazy-loaded. **There is no server-side resizing** – see "Limitations".
+- **Thumbnails** (`thumbSrc()`): prefer a child note of the article titled `thumb.<ext>` **or**
+  `*_thumb.<ext>` (e.g. `thumb.png`, `ngc281_thumb.jpg`) → `api/notes/<id>/download`; otherwise
+  use the first `<img>` from the note content. Layout: image left, summary right (`.blog-post-inner`),
+  `max-height:256px`, lazy-loaded. The generator auto-sets `shareHiddenFromTree` on matching
+  thumb child notes so they never appear in the blog menu. **There is no server-side resizing** –
+  see "Limitations".
 - Regenerates `feed.xml`, `sitemap.xml`, `state_map` (garden states) and `blog_data`
   (search index: id/title/url/summary/tags/category). Sets `shareDescription` from `summary`.
 
diff --git a/blog_generator.js b/blog_generator.js
index f2e1493..c68589a 100644
--- a/blog_generator.js
+++ b/blog_generator.js
@@ -103,7 +103,7 @@ function run() {
 
     function thumbSrc(a) {
         try {
-            const thumbs = (a.getChildNotes() || []).filter(n => /_thumb\.[A-Za-z0-9]+$/i.test(n.title));
+            const thumbs = (a.getChildNotes() || []).filter(n => /^(?:thumb|.+_thumb)\.[A-Za-z0-9]+$/i.test(n.title));
             if (thumbs.length) return "api/notes/" + thumbs[0].noteId + "/download";
         } catch (e) {}
         try {
@@ -598,6 +598,19 @@ function run() {
         }
     }
 
+    function hideThumbChildren() {
+        for (const a of articles) {
+            try {
+                for (const c of a.getChildNotes()) {
+                    if (/^(?:thumb|.+_thumb)\.[A-Za-z0-9]+$/i.test(c.title) && !c.hasLabel("shareHiddenFromTree")) {
+                        c.setLabel("shareHiddenFromTree", "");
+                        c.save();
+                    }
+                }
+            } catch (e) {}
+        }
+    }
+
     buildIndex();
 
     const systemNote = api.getNote(BLOG_SYSTEM_NOTE_ID);
@@ -617,5 +630,6 @@ function run() {
     buildSitemap();
     ensureSeoMeta();
     buildBlogData();
+    hideThumbChildren();
     removeEmptyCategories();
 }
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