diff --git a/l4d2web/l4d2web/static/js/files-overlay.js b/l4d2web/l4d2web/static/js/files-overlay.js
index 103d246..8c2cd26 100644
--- a/l4d2web/l4d2web/static/js/files-overlay.js
+++ b/l4d2web/l4d2web/static/js/files-overlay.js
@@ -89,13 +89,14 @@
     options.credentials = "same-origin";
     const response = await fetch(url, options);
     let body = null;
+    let rawText = "";
     try {
-      const text = await response.text();
-      body = text ? JSON.parse(text) : null;
+      rawText = await response.text();
+      body = rawText ? JSON.parse(rawText) : null;
     } catch (_e) {
       body = null;
     }
-    return { ok: response.ok, status: response.status, body };
+    return { ok: response.ok, status: response.status, body, rawText };
   }
 
   async function postJson(url, payload) {
@@ -609,12 +610,34 @@
       const content = (window.__filesEditor && window.__filesEditor.getValue)
         ? window.__filesEditor.getValue()
         : ta.value;
-      const r = await postJson(`${baseUrl}/files/save`, { path: relPath, content });
+
+      // Rename-on-save: if the user edited the filename input, compose the
+      // new path (sibling rename only — joining parent of relPath with the
+      // new filename). Send payload.new_path so the server moves and writes
+      // atomically. Matches the legacy save handler's contract.
+      const filenameInput = modalContent.querySelector("[data-editor-filename]");
+      const editedFilename = filenameInput ? filenameInput.value.trim() : "";
+      const originalLeaf = relPath.split("/").pop() || relPath;
+      const parent = relPath.includes("/") ? relPath.slice(0, relPath.lastIndexOf("/")) : "";
+      let newPath = null;
+      if (editedFilename && editedFilename !== originalLeaf) {
+        newPath = parent ? `${parent}/${editedFilename}` : editedFilename;
+      }
+
+      const payload = { path: relPath, content };
+      if (newPath) payload.new_path = newPath;
+
+      const r = await postJson(`${baseUrl}/files/save`, payload);
       if (r.ok) {
         if (typeof window.closeModal === "function") window.closeModal();
-        scheduleRefresh(parentOf(relPath));
+        scheduleRefresh(parentOf(newPath || relPath));
+      } else if (r.status === 409) {
+        // Conflict (destination already exists) — show error and keep modal
+        // open so the user can pick a different filename.
+        alert(r.rawText || `Conflict: destination already exists.`);
+        return;
       } else {
-        alert((r.body && r.body.error) || `Save failed (HTTP ${r.status}).`);
+        alert((r.body && r.body.error) || r.rawText || `Save failed (HTTP ${r.status}).`);
       }
       return;
     }