diff --git a/koha-tmpl/intranet-tmpl/prog/en/modules/tools/viewlog.tt b/koha-tmpl/intranet-tmpl/prog/en/modules/tools/viewlog.tt
index e666323931..179875227f 100644
--- a/koha-tmpl/intranet-tmpl/prog/en/modules/tools/viewlog.tt
+++ b/koha-tmpl/intranet-tmpl/prog/en/modules/tools/viewlog.tt
@@ -95,6 +95,16 @@
         table.struct-diff ul.diff-obj li {
             white-space: nowrap;
         }
+        /* Catalog log info column (biblio JSON payload) */
+        div.loginfo-struct {
+            font-family: monospace;
+            font-size: 0.85em;
+        }
+        div.loginfo-struct ul.diff-obj {
+            list-style: none;
+            margin: 0;
+            padding: 0 0 0 0.8em;
+        }
     </style>
 [% END %]
 </head>
diff --git a/koha-tmpl/intranet-tmpl/prog/js/viewlog.js b/koha-tmpl/intranet-tmpl/prog/js/viewlog.js
index 399732f0e2..c2b45ebea6 100644
--- a/koha-tmpl/intranet-tmpl/prog/js/viewlog.js
+++ b/koha-tmpl/intranet-tmpl/prog/js/viewlog.js
@@ -21,6 +21,56 @@ function collectDiffEntries(node, prefix) {
     return entries;
 }
 
+/**
+ * Pretty-print a parsed JSON value as nested <ul> markup. Arrays become
+ * ordered lists preserving MARC-in-JSON field order; objects render their
+ * keys. Used by both the struct-diff renderer and the catalog info renderer.
+ */
+function fmtJsonValue(v) {
+    if (v === undefined || v === null) return "";
+    if (typeof v !== "object") return $("<span>").text(String(v)).html();
+    if (Array.isArray(v)) {
+        var items = v
+            .map(function (item) {
+                return "<li>" + fmtJsonValue(item) + "</li>";
+            })
+            .join("");
+        return '<ul class="diff-obj">' + items + "</ul>";
+    }
+    var items = Object.keys(v)
+        .map(function (k) {
+            return (
+                "<li>" +
+                $("<span>").text(k).html() +
+                ": " +
+                fmtJsonValue(v[k]) +
+                "</li>"
+            );
+        })
+        .join("");
+    return '<ul class="diff-obj">' + items + "</ul>";
+}
+
+/**
+ * Render the info column for a CATALOGUING log entry. The payload is
+ * "biblio <JSON>" where the JSON is the pre-change (MODIFY) or final
+ * (DELETE) state of the record, including a MARC-in-JSON `_marc` key.
+ * Returns rendered HTML, or null if the text doesn't look like a
+ * biblio JSON payload (e.g. the bare "biblio" prefix logged on ADD).
+ */
+function renderCatalogInfo(raw) {
+    if (!raw) return null;
+    var match = raw.match(/^biblio\s+(\{[\s\S]*\})\s*$/);
+    if (!match) return null;
+    var parsed;
+    try {
+        parsed = JSON.parse(match[1]);
+    } catch (e) {
+        return null;
+    }
+    return '<div class="loginfo-struct">' + fmtJsonValue(parsed) + "</div>";
+}
+
 /**
  * Render Struct::Diff JSON as a human-readable before/after table.
  * Falls back to a <pre> block for non-Struct::Diff JSON or plain text.
@@ -40,39 +90,16 @@ function renderStructDiff(raw) {
     var entries = collectDiffEntries(diff.D, "");
     if (!entries.length) return "";
 
-    function fmt(v) {
-        if (v === undefined || v === null) return "";
-        if (typeof v !== "object") return $("<span>").text(String(v)).html();
-        if (Array.isArray(v)) {
-            var items = v
-                .map(function (item) {
-                    return "<li>" + fmt(item) + "</li>";
-                })
-                .join("");
-            return '<ul class="diff-obj">' + items + "</ul>";
-        }
-        var items = Object.keys(v)
-            .map(function (k) {
-                return (
-                    "<li>" +
-                    $("<span>").text(k).html() +
-                    ": " +
-                    fmt(v[k]) +
-                    "</li>"
-                );
-            })
-            .join("");
-        return '<ul class="diff-obj">' + items + "</ul>";
-    }
-
     var rows = entries
         .map(function (e) {
             var before =
                 e.before !== undefined
-                    ? "<del>" + fmt(e.before) + "</del>"
+                    ? "<del>" + fmtJsonValue(e.before) + "</del>"
                     : "";
             var after =
-                e.after !== undefined ? "<ins>" + fmt(e.after) + "</ins>" : "";
+                e.after !== undefined
+                    ? "<ins>" + fmtJsonValue(e.after) + "</ins>"
+                    : "";
             return (
                 "<tr>" +
                 '<td class="diff-key">' +
@@ -269,6 +296,14 @@ $(document).ready(function () {
             $(this).html(renderStructDiff(raw));
         }
     });
+
+    $("div.loginfo").each(function () {
+        var raw = $(this).text().trim();
+        var rendered = renderCatalogInfo(raw);
+        if (rendered) {
+            $(this).html(rendered);
+        }
+    });
     patron_autocomplete($("#user"), {
         "on-select-callback": function (event, ui) {
             $("#user").val(ui.item.patron_id);