diff --git a/src/app_controller.py b/src/app_controller.py
index 6f8e39e7..f21db854 100644
--- a/src/app_controller.py
+++ b/src/app_controller.py
@@ -2723,6 +2723,16 @@ class AppController:
     self.files.append(models.FileItem.from_dict(p))
    else:
     self.files.append(models.FileItem(path=str(p)))
+  import copy
+  self.context_files = []
+  for f in self.files:
+   if isinstance(f, models.FileItem):
+    fi = copy.deepcopy(f)
+   else:
+    fi = models.FileItem(path=str(f))
+   self.context_files.append(fi)
+  if hasattr(self, "_app") and self._app is not None:
+   self._app.ui_selected_context_files = {f.path for f in self.context_files if f.auto_aggregate}
   self.screenshots = list(self.project.get("screenshots", {}).get("paths", []))
   disc_sec = self.project.get("discussion", {})
   self.disc_roles = list(disc_sec.get("roles", ["User", "AI", "Vendor API", "System"]))
diff --git a/tests/test_project_switch_persona_preset.py b/tests/test_project_switch_persona_preset.py
index d6f14da0..1c042806 100644
--- a/tests/test_project_switch_persona_preset.py
+++ b/tests/test_project_switch_persona_preset.py
@@ -170,3 +170,51 @@ def test_load_context_preset_missing_raises_keyerror(tmp_path, monkeypatch):
 
     with pytest.raises(KeyError, match="Context preset 'NonexistentPreset' not found"):
         ctrl.load_context_preset("NonexistentPreset")
+
+
+def test_switch_project_resets_context_files(tmp_path, monkeypatch):
+    project_a_path, project_b_path = _setup_two_projects(tmp_path)
+
+    proj_a_data = '''[project]
+name = "project_a"
+[files]
+base_dir = "."
+paths = [
+  { path = "C:/projects/forth/bootslop/main.c", view_mode = "full" },
+  { path = "C:/projects/Pikuma/ps1/code/gte_hello/hello_gte.c", view_mode = "full" },
+]
+'''
+    project_a_path.write_text(proj_a_data)
+
+    proj_b_data = '''[project]
+name = "project_b"
+[files]
+base_dir = "."
+paths = [
+  { path = "C:/projects/gencpp/base/dependencies/timing.cpp", view_mode = "full" },
+  { path = "C:/projects/gencpp/base/dependencies/timing.hpp", view_mode = "full" },
+]
+'''
+    project_b_path.write_text(proj_b_data)
+
+    ctrl = AppController()
+    monkeypatch.setattr(ctrl, "_rebuild_rag_index", lambda: None)
+    monkeypatch.setattr(ctrl, "_flush_to_project", lambda: None)
+
+    ctrl.active_project_path = str(project_a_path)
+    ctrl.project = project_manager.load_project(str(project_a_path))
+    ctrl.preset_manager = presets.PresetManager(Path(project_a_path).parent)
+    ctrl.tool_preset_manager = tool_presets.ToolPresetManager(Path(project_a_path).parent)
+    ctrl.persona_manager = PersonaManager(Path(project_a_path).parent)
+    ctrl._refresh_from_project()
+
+    assert len(ctrl.context_files) == 2
+    assert any("forth" in f.path for f in ctrl.context_files)
+    assert any("gte_hello" in f.path for f in ctrl.context_files)
+
+    ctrl._switch_project(str(project_b_path))
+
+    assert len(ctrl.context_files) == 2
+    assert all("gencpp" in f.path for f in ctrl.context_files)
+    assert not any("forth" in f.path for f in ctrl.context_files)
+    assert not any("gte_hello" in f.path for f in ctrl.context_files)