diff --git a/src/gui_2.py b/src/gui_2.py
index 360c2b1e..d4698f6a 100644
--- a/src/gui_2.py
+++ b/src/gui_2.py
@@ -500,6 +500,42 @@ class App:
    try:
     self.controller.on_warmup_complete(lambda status: _on_warmup_complete_callback(self, status))
    except Exception: pass
+   self._diag_layout_state()
+
+ def _diag_layout_state(self) -> None:
+  """
+  One-shot startup diagnostic: log show_windows state and warn if the
+  on-disk manualslop_layout.ini references window names that no longer
+  exist in the current code. Helps users and test operators detect
+  stale layout state at a glance instead of debugging missing panels.
+  [C: src/gui_2.py:App._post_init]
+  """
+  import os as _os
+  visible_by_default = [w for w, v in self.show_windows.items() if v]
+  sys.stderr.write(f"[GUI] show_windows entries: {len(self.show_windows)}, visible by default: {len(visible_by_default)}\n")
+  if visible_by_default:
+   sys.stderr.write(f"[GUI] visible-by-default windows: {', '.join(sorted(visible_by_default))}\n")
+  ini_path = _os.path.join(_os.getcwd(), "manualslop_layout.ini")
+  if not _os.path.exists(ini_path):
+   sys.stderr.write(f"[GUI] no layout file at {ini_path} (HelloImGui will create a fresh one on shutdown)\n")
+   return
+  ini_size = _os.path.getsize(ini_path)
+  sys.stderr.write(f"[GUI] layout file: {ini_path} ({ini_size} bytes)\n")
+  try:
+   with open(ini_path, encoding="utf-8") as _f:
+    _ini_text = _f.read()
+  except Exception as _e:
+   sys.stderr.write(f"[GUI] could not read layout file: {_e}\n")
+   return
+  _STALE_WINDOW_NAMES = {
+   "Projects", "Files", "Screenshots", "Discussion History",
+   "Provider", "Message", "Response", "Tool Calls",
+   "Comms History", "System Prompts", "Theme",
+  }
+  _stale_found = [n for n in _STALE_WINDOW_NAMES if f"[Window][{n}]" in _ini_text]
+  if _stale_found:
+   sys.stderr.write(f"[GUI] WARNING: layout has {len(_stale_found)} stale window name(s) that no longer exist: {', '.join(_stale_found)}\n")
+   sys.stderr.write(f"[GUI] Run the 'Reset Layout' command from the Command Palette (or delete {ini_path}) to regenerate.\n")
 
  def _trigger_hot_reload(self) -> bool:
   from src.hot_reloader import HotReloader