diff --git a/eleventy.config.js b/eleventy.config.js
index 4a1bb97..dc8545c 100644
--- a/eleventy.config.js
+++ b/eleventy.config.js
@@ -1364,6 +1364,21 @@ export default function (eleventyConfig) {
     return result;
   });
 
+  // Find other published posts that share the same external target URL
+  // (repostOf, likeOf, bookmarkOf, inReplyTo). Used to cross-link related posts.
+  eleventyConfig.addFilter("sameTargetPosts", function (posts, targetUrl, currentUrl) {
+    if (!targetUrl) return [];
+    const norm = (u) => String(u).replace(/\/$/, "");
+    const t = norm(targetUrl);
+    return (posts || []).filter((p) => {
+      if (norm(p.url) === norm(currentUrl)) return false;
+      const d = p.data;
+      return [d.repostOf, d.repost_of, d.likeOf, d.like_of,
+              d.bookmarkOf, d.bookmark_of, d.inReplyTo, d.in_reply_to]
+        .some((v) => v && norm(v) === t);
+    });
+  });
+
   // Strip garden/* tags from a category list so they don't render as
   // plain category pills alongside the garden badge.
   eleventyConfig.addFilter("withoutGardenTags", (categories) => {