diff --git a/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/Pages/EnvelopeSenderEditorPage.razor b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/Pages/EnvelopeSenderEditorPage.razor
index 1c211e79..02a5588f 100644
--- a/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/Pages/EnvelopeSenderEditorPage.razor
+++ b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/Pages/EnvelopeSenderEditorPage.razor
@@ -348,8 +348,17 @@
 
     protected override void OnInitialized()
     {
-        // If no session id exists yet, generate one and redirect so it sticks in the URL.
-        // This is the ONLY navigation that uses forceLoad; afterwards the page lives forever.
+        // Intentionally empty.
+        // esid redirect is done in OnAfterRenderAsync to avoid NavigationException
+        // during SSR prerendering, where NavigateTo throws by design.
+    }
+
+    protected override async Task OnAfterRenderAsync(bool firstRender)
+    {
+        if (!firstRender) return;
+
+        // Generate a session id on first interactive render and push it into the URL.
+        // At this point SignalR is connected and NavigateTo is safe.
         if (string.IsNullOrWhiteSpace(Esid))
         {
             var sid = Guid.NewGuid().ToString("N");