diff --git a/src/gui_2.py b/src/gui_2.py
index 09209ee..8e94086 100644
--- a/src/gui_2.py
+++ b/src/gui_2.py
@@ -507,6 +507,37 @@ class App:
    f.write(data)
    # ---------------------------------------------------------------- helpers
 
+ def _populate_auto_slices(self, f_item: models.FileItem) -> None:
+  from src import mcp_client
+  import re
+  mcp_client.configure([{"path": f_item.path}])
+  outline = mcp_client.py_get_code_outline(f_item.path)
+  if outline.startswith("ERROR") or outline.startswith("ACCESS DENIED"):
+   return
+  pattern = re.compile(r'^\s*\[(.*?)\] (.*?) \(Lines (\d+)-(\d+)\)', re.MULTILINE)
+  try:
+   with open(f_item.path, "r", encoding="utf-8") as f:
+    text = f.read()
+  except Exception:
+   return
+  try:
+   from src.fuzzy_anchor import FuzzyAnchor
+  except ImportError:
+   FuzzyAnchor = None
+  for match in pattern.finditer(outline):
+   kind, name, s_str, e_str = match.groups()
+   s_line = int(s_str)
+   e_line = int(e_str)
+   if any(s.get('start_line') == s_line and s.get('end_line') == e_line for s in f_item.custom_slices):
+    continue
+   if FuzzyAnchor:
+    slice_data = FuzzyAnchor.create_slice(text, s_line, e_line)
+   else:
+    slice_data = {"start_line": s_line, "end_line": e_line}
+   slice_data['tag'] = 'auto-ast'
+   slice_data['comment'] = name
+   f_item.custom_slices.append(slice_data)
+
  def _render_text_viewer(self, label: str, content: str, text_type: str = 'text', force_open: bool = False) -> None:
   if imgui.button("[+]##" + str(id(content))) or force_open:
    self.text_viewer_type = text_type
@@ -1889,6 +1920,46 @@ class App:
    
    imgui.end_popup()
 
+ def _render_add_context_files_modal(self) -> None:
+  if imgui.begin_popup_modal("Select Context Files", None, imgui.WindowFlags_.always_auto_resize)[0]:
+   imgui.text("Select files from project to add to context:")
+   imgui.begin_child("ctx_picker_list", imgui.ImVec2(600, 300), True)
+   
+   from src import models
+   # Create a temporary selection set if not initialized
+   if not hasattr(self, '_ui_picker_selected'):
+    self._ui_picker_selected = set()
+   
+   for f in self.files:
+    fpath = f.path if hasattr(f, 'path') else str(f)
+    # Skip if already in context
+    if any((cf.path if hasattr(cf, 'path') else str(cf)) == fpath for cf in self.context_files):
+     continue
+    is_sel = fpath in self._ui_picker_selected
+    clicked, new_sel = imgui.checkbox(f"{fpath}##picker_{fpath}", is_sel)
+    if clicked:
+     if new_sel:
+      self._ui_picker_selected.add(fpath)
+     else:
+      self._ui_picker_selected.discard(fpath)
+   imgui.end_child()
+   imgui.separator()
+   
+   if imgui.button("Add Selected", imgui.ImVec2(120, 0)):
+    for fpath in self._ui_picker_selected:
+     f_item = models.FileItem(path=fpath)
+     self.context_files.append(f_item)
+     self._populate_auto_slices(f_item)
+    self._ui_picker_selected.clear()
+    imgui.close_current_popup()
+
+   imgui.same_line()
+   if imgui.button("Cancel", imgui.ImVec2(120, 0)):
+    if hasattr(self, '_ui_picker_selected'):
+     self._ui_picker_selected.clear()
+    imgui.close_current_popup()
+   imgui.end_popup()
+
  def _render_preset_manager_content(self, is_embedded: bool = False) -> None:
   avail = imgui.get_content_region_avail()
   if not hasattr(self, "_prompt_md_preview"): self._prompt_md_preview = False
@@ -2953,7 +3024,9 @@ class App:
     for f in self.files:
      f_path = f.path if hasattr(f, "path") else str(f)
      if f_path not in context_paths:
-      self.context_files.append(copy.deepcopy(f))
+      f_copy = copy.deepcopy(f)
+      self.context_files.append(f_copy)
+      self._populate_auto_slices(f_copy)
    imgui.same_line()
    if imgui.button("Del##batch"):
     new_files = []
diff --git a/tests/test_auto_slices.py b/tests/test_auto_slices.py
new file mode 100644
index 0000000..7f49995
--- /dev/null
+++ b/tests/test_auto_slices.py
@@ -0,0 +1,92 @@
+import pytest
+from unittest.mock import MagicMock, patch, mock_open
+from src.gui_2 import App
+from src import models
+
+@pytest.fixture
+def mock_app():
+ with (
+  patch('src.models.load_config', return_value={
+   "ai": {"provider": "gemini", "model": "model-1"},
+   "projects": {"paths": [], "active": ""},
+   "gui": {"show_windows": {}}
+  }),
+  patch('src.project_manager.load_project', return_value={}),
+  patch('src.project_manager.migrate_from_legacy_config', return_value={}),
+  patch('src.project_manager.save_project'),
+  patch('src.session_logger.open_session'),
+  patch('src.session_logger.reset_session'),
+  patch('src.app_controller.AppController._init_ai_and_hooks'),
+  patch('src.app_controller.AppController._fetch_models'),
+  patch('src.gui_2.App._load_fonts'),
+  patch('src.gui_2.App._post_init')
+ ):
+  app = App()
+  app.files = []
+  app.context_files = []
+  return app
+
+def test_populate_auto_slices_basic(mock_app: App) -> None:
+ f_item = models.FileItem(path="test.py")
+ mock_outline = "[Class] MyClass (Lines 1-10)\n[Method] my_method (Lines 2-5)\n[Func] top_func (Lines 12-15)"
+ 
+ with (
+  patch('src.mcp_client.configure') as mock_conf,
+  patch('src.mcp_client.py_get_code_outline', return_value=mock_outline) as mock_outline_tool,
+  patch('builtins.open', mock_open(read_data="dummy content"))
+ ):
+  mock_app._populate_auto_slices(f_item)
+  
+  assert len(f_item.custom_slices) == 3
+  s0 = f_item.custom_slices[0]
+  assert s0["start_line"] == 1
+  assert s0["end_line"] == 10
+  assert s0["tag"] == 'auto-ast'
+  assert s0["comment"] == "MyClass"
+
+def test_add_selected_triggers_auto_slices(mock_app):
+ f_mock = MagicMock()
+ f_mock.path = "test.py"
+ mock_app.files = [f_mock]
+ mock_app._ui_picker_selected = {"test.py"}
+ 
+ with patch('src.gui_2.imgui') as mock_imgui:
+  mock_imgui.begin_popup_modal.return_value = (True, True)
+  mock_imgui.button.side_effect = lambda label, size=None: label == "Add Selected"
+  mock_imgui.checkbox.return_value = (False, False)
+  mock_imgui.begin_child.return_value = True
+  mock_imgui.ImVec2 = MagicMock()
+  mock_imgui.WindowFlags_ = MagicMock()
+  
+  with patch.object(mock_app, '_populate_auto_slices') as mock_populate:
+   mock_app._render_add_context_files_modal()
+   
+   assert mock_populate.called
+   assert len(mock_app.context_files) == 1
+   assert mock_app.context_files[0].path == "test.py"
+
+def test_add_all_triggers_auto_slices(mock_app):
+ f_mock = MagicMock()
+ f_mock.path = "test_all.py"
+ mock_app.files = [f_mock]
+ mock_app.context_files = []
+ 
+ with patch('src.gui_2.imgui') as mock_imgui:
+  mock_imgui.button.side_effect = lambda label, size=None: label == "Add All##addall"
+  mock_imgui.collapsing_header.return_value = True
+  mock_imgui.begin_child.return_value = True
+  mock_imgui.begin_table.return_value = True
+  mock_imgui.tree_node_ex.return_value = False
+  mock_imgui.checkbox.return_value = (False, False)
+  mock_imgui.combo.return_value = (False, 0)
+  mock_imgui.input_text.return_value = (False, "")
+  mock_imgui.TableFlags_ = MagicMock()
+  mock_imgui.TableColumnFlags_ = MagicMock()
+  mock_imgui.TreeNodeFlags_ = MagicMock()
+  
+  with patch.object(mock_app, '_populate_auto_slices') as mock_populate:
+   mock_app._render_context_composition_panel()
+   
+   assert mock_populate.called
+   assert len(mock_app.context_files) == 1
+   assert mock_app.context_files[0].path == "test_all.py"