fix: forward wheel events with coordinates when mouse tracking is active

lib/input-handler.ts

@@ -894,16 +894,36 @@ export class InputHandler {
     if (this.isDisposed) return;
     if (!this.mouseConfig?.hasMouseTracking()) return;
 
+    this.sendWheelMouseEvent(event);
+
+    // Prevent default scrolling when mouse tracking is active
+    event.preventDefault();
+  }
+
+  /**
+   * Send a wheel event as a mouse tracking sequence.
+   * Public so that Terminal can forward wheel events when mouse tracking is
+   * active (the Terminal-level capture handler stops propagation to prevent
+   * browser scrolling, so this method allows explicit forwarding).
+   */
+  handleWheelEvent(event: WheelEvent): void {
+    if (this.isDisposed) return;
+
+    this.sendWheelMouseEvent(event);
+  }
+
+  /**
+   * Encode and send a wheel event as a mouse tracking escape sequence.
+   * Button 64 = scroll up, button 65 = scroll down, with cell coordinates.
+   */
+  private sendWheelMouseEvent(event: WheelEvent): void {
     const cell = this.pixelToCell(event);
     if (!cell) return;
 
     // Wheel events: button 64 = scroll up, button 65 = scroll down
     const button = event.deltaY < 0 ? 64 : 65;
 
     this.sendMouseEvent(button, cell.col, cell.row, false, event);
-
-    // Prevent default scrolling when mouse tracking is active
-    event.preventDefault();
   }
 
   /**

lib/terminal.ts

@@ -1552,6 +1552,20 @@ export class Terminal implements ITerminalCore {
       return;
     }
 
+    // When mouse tracking is active, the application wants to receive mouse
+    // wheel events with coordinates so it can determine which pane/zone the
+    // cursor is over (critical for TUIs with multiple scroll regions like
+    // tmux, vim splits, etc.).  Delegate to the InputHandler which sends
+    // proper SGR/X10 mouse sequences with the cell position.
+    if (this.wasmTerm?.hasMouseTracking()) {
+      // InputHandler.handleWheel is registered on the same container but in
+      // the bubbling phase.  Since we already called stopPropagation() above
+      // (to prevent the browser from scrolling the page), we need to forward
+      // the event explicitly.
+      this.inputHandler?.handleWheelEvent(e);
+      return;
+    }
+
     // Check if in alternate screen mode (vim, less, htop, etc.)
     const isAltScreen = this.wasmTerm?.isAlternateScreen() ?? false;