fix: ensure session state is removed correctly when closing tabs

frontend/src/js/app.js

@@ -384,8 +384,8 @@
       this.rawViewer.destroyViewer(sessionId);
       window.NexusTerminal.GitHubViewer.destroyViewer(sessionId);
       window.NexusTerminal.VNCViewer.destroyViewer(sessionId);
-      this.state.removeSession(sessionId);
       this.tabs.removeTab(sessionId);
+      this.state.removeSession(sessionId);
       this.updateStatusBar();
     }
 

frontend/src/js/tabs.js

@@ -65,6 +65,7 @@
      */
     removeTab(sessionId) {
       const idx = this.order.indexOf(sessionId);
+      const wasActive = this.app.state.activeSessionId === sessionId;
       if (idx !== -1) this.order.splice(idx, 1);
 
       // Remove tab element
@@ -77,8 +78,8 @@
       const panel = document.getElementById(`panel-${sessionId}`);
       if (panel) panel.remove();
 
-      // If this was the active tab, activate the nearest neighbour
-      if (this.app.state.activeSessionId === sessionId) {
+      // Activate the nearest neighbour
+      if (wasActive) {
         const next =
           this.order.length > 0
             ? this.order[Math.min(idx, this.order.length - 1)]
@@ -176,8 +177,8 @@
       this.app.terminals.destroyTerminal(sessionId);
       this.app.rawViewer.destroyViewer(sessionId);
       window.NexusTerminal.GitHubViewer.destroyViewer(sessionId);
-      this.app.state.removeSession(sessionId);
       this.removeTab(sessionId);
+      this.app.state.removeSession(sessionId);
     }
 
     /**

frontend/src/js/terminal.js

@@ -112,6 +112,34 @@
         });
       }
 
+      // Alternate-screen scroll passthrough for screen/tmux/byobu.
+      // When the terminal is in the alternate buffer (used by multiplexers),
+      // convert mouse-wheel events into arrow-key sequences so the remote
+      // application handles scrollback instead of xterm.js (which has no
+      // scrollback content in alternate mode).
+      const viewportEl = container.querySelector(".xterm-viewport");
+      if (viewportEl) {
+        viewportEl.addEventListener("wheel", (e) => {
+          if (term.buffer.active !== term.buffer.alternate) return;
+          // Only intercept when mouse tracking is NOT active (if mouse mode
+          // is on, xterm.js already forwards events correctly).
+          if (term.modes && term.modes.mouseTrackingMode &&
+              term.modes.mouseTrackingMode !== "none") return;
+
+          e.preventDefault();
+          e.stopPropagation();
+          const lines = Math.max(1, Math.round(Math.abs(e.deltaY) / 40));
+          const seq = e.deltaY < 0 ? "\x1b[A" : "\x1b[B";
+          const data = seq.repeat(lines);
+          const b64 = btoa(data);
+          try {
+            window.go.api.Service.WriteSession(sessionId, b64);
+          } catch (_) {
+            /* non-critical */
+          }
+        }, { passive: false });
+      }
+
       // Drag-and-drop file handling
       container.addEventListener("dragover", (e) => {
         if (