diff --git a/TrimSP.html b/TrimSP.html
index a275856..e16643c 100644
--- a/TrimSP.html
+++ b/TrimSP.html
@@ -4,8 +4,16 @@
   <meta http-equiv="Content-type" content="text/html;charset=UTF-8">
   <link rel="stylesheet" href="ZGUI.css">
   <link rel="stylesheet" href="https://www.w3schools.com/w3css/4/w3.css">
-  <script src="TrimSPelec.js"></script>
-  <!script src="TrimSPWeb.js"></script>
+  <script src="TrimSPweb.js"></script>
+  <script>
+    // Electron exposes CommonJS module support; plain browsers do not.
+    // Load the Electron-specific helpers only for the standalone app.
+    if (typeof module !== 'undefined' && module.exports) {
+      document.write('<script src="TrimSPelec.js"><\\/script>');
+    } else {
+      document.write('<script src="plotly.js"><\\/script>');
+    }
+  </script>
   <script src="TrimSPlib.js"></script>
   <script src="myplots.js"></script>
   <!script src="https://cdn.plot.ly/plotly-latest.min.js"></script>
diff --git a/TrimSPlib.js b/TrimSPlib.js
index 923bfe1..72ac418 100644
--- a/TrimSPlib.js
+++ b/TrimSPlib.js
@@ -3748,6 +3748,10 @@ async function startSequence() {
 	randStr = (Math.random() + 1).toString(36).substring(7);
 	All["fileNamePrefix"] = randStr;
 	All["workPath"] = "/tmp/" + randStr;
+	// prep_cfg() reads these values from the DOM, so keep the hidden web
+	// fields synchronized with the randomized server-side run directory.
+	document.getElementById("fileNamePrefix").value = All["fileNamePrefix"];
+	document.getElementById("workPath").value = All["workPath"];
 	updateStatusBar({ backend: 'Web backend' });
     }
     updateStatusBar({ workPath: All["workPath"], run: 'Starting run...' });
diff --git a/TrimSPweb.js b/TrimSPweb.js
index cb9f2a8..b7062b3 100644
--- a/TrimSPweb.js
+++ b/TrimSPweb.js
@@ -6,6 +6,12 @@ function writeAsciiFile(filename,content) {
     //console.log(filename, content);
     // Prepare CGI args use POST for long files
     let cgiargs = "fn="+filename; // POST
+    // Forward the GUI-selected RNG backend to the CGI wrapper, which passes it
+    // to trimspNL as the optional second command-line argument.
+    let rngType = document.getElementById("rngType");
+    if (rngType) {
+	cgiargs += "&rngType=" + rngType.value;
+    }
     let lines = content.split(/\n/);
     let prefix = filename.split(/\//);
     for (let i=0; i<lines.length; i++) {
@@ -48,6 +54,12 @@ function writeAsciiFile2(filename,content) {
     //console.log(filename, content);
     // Prepare CGI args use GET for short files
     let cgiargs = "?fn="+filename; // GET
+    // Keep GET and POST requests equivalent for callers that still use this
+    // short-file helper.
+    let rngType = document.getElementById("rngType");
+    if (rngType) {
+	cgiargs += "&rngType=" + rngType.value;
+    }
     let lines = content.split(/\n/);
     let prefix = filename.split(/\//);
     for (let i=0; i<lines.length; i++) {
@@ -121,4 +133,3 @@ function fileExists(filename) {
         return 1;
     }
 }
-