diff --git a/lib/launcher.js b/lib/launcher.js
index 068fd334..3382eb3e 100644
--- a/lib/launcher.js
+++ b/lib/launcher.js
@@ -243,7 +243,18 @@ class Launcher {
             }
         }
 
-        const themeName = this.config.theme || 'forge-light'
+        // Mirror the NR5+ theme gate from nr-launcher's runtimeSettings.js.
+        const storedTheme = this.config.theme || 'forge-light'
+        const snapshotNRVersion = this.snapshot?.modules?.['node-red']
+        const nrMajor = parseInt((snapshotNRVersion || '0.0.0').split('.')[0], 10) || 0
+        let themeName = storedTheme
+        if (nrMajor >= 5) {
+            if (themeName === 'forge-light' || themeName === 'forge-dark' || themeName === 'forge') {
+                themeName = 'forge'
+            }
+        } else if (themeName === 'forge') {
+            themeName = 'forge-light'
+        }
         const assistant = {
             enabled: this.settings?.assistant?.enabled || false, // overall enable/disable
             url: `${this.config.forgeURL}/api/v1/assistant/`, // URL for the assistant service