diff --git a/src/aggregate.py b/src/aggregate.py
index da04e0d9..c7e49615 100644
--- a/src/aggregate.py
+++ b/src/aggregate.py
@@ -199,52 +199,83 @@ def build_file_items(base_dir: Path, files: list[str | dict[str, Any]]) -> list[
      mtime = path.stat().st_mtime
      error = False
      if not error and view_mode != "full":
-      if view_mode == "summary":
-       content = summarize.summarise_file(path, content)
-      elif view_mode == "skeleton":
-       if path.suffix == ".py":
-        if not parser: parser = ASTParser("python")
-        content = parser.get_skeleton(content, path=str(path))
-       elif path.suffix in ['.c', '.h', '.cpp', '.hpp', '.cxx', '.cc']:
-        from src import mcp_client
-        if path.suffix in ['.c', '.h']: content = mcp_client.ts_c_get_skeleton(str(path))
-        else: content = mcp_client.ts_cpp_get_skeleton(str(path))
-       else:
-        content = summarize.summarise_file(path, content)
-      elif view_mode == "outline":
-       if path.suffix == ".py":
-        if not parser: parser = ASTParser("python")
-        content = parser.get_code_outline(content, path=str(path))
-       elif path.suffix in ['.c', '.h', '.cpp', '.hpp', '.cxx', '.cc']:
-        from src import mcp_client
-        if path.suffix in ['.c', '.h']: content = mcp_client.ts_c_get_code_outline(str(path))
-        else: content = mcp_client.ts_cpp_get_code_outline(str(path))
-       else:
-        content = summarize.summarise_file(path, content)
-      elif view_mode == "none":
-       content = "(context excluded)"
-      elif view_mode == "custom":
-       if custom_slices:
-        lines = content.splitlines()
-        slices_text = []
-        for s in custom_slices:
-         start = s.get("start_line", 1)
-         end = s.get("end_line", len(lines))
-         tag = s.get("tag", "unnamed")
-         comment = s.get("comment", "")
-         s_idx = max(0, start - 1)
-         e_idx = min(len(lines), end)
-         chunk = "\n".join(lines[s_idx:e_idx])
-         slices_text.append(f"---\n[Slice: {tag}] ({comment})\nLines {start}-{end}:\n{chunk}")
-        content = "\n\n".join(slices_text)
-       else:
+      try:
+       if view_mode == "summary":
         content = summarize.summarise_file(path, content)
+       elif view_mode == "skeleton":
+        suffix_lower = path.suffix.lower()
+        if suffix_lower == ".py":
+         if not parser: parser = ASTParser("python")
+         content = parser.get_skeleton(content, path=str(path))
+        elif suffix_lower in ['.c', '.h', '.cpp', '.hpp', '.cxx', '.cc']:
+         from src import mcp_client
+         if suffix_lower in ['.c', '.h']: content = mcp_client.ts_c_get_skeleton(str(path))
+         else: content = mcp_client.ts_cpp_get_skeleton(str(path))
+        else:
+         content = summarize.summarise_file(path, content)
+       elif view_mode == "outline":
+        suffix_lower = path.suffix.lower()
+        if suffix_lower == ".py":
+         if not parser: parser = ASTParser("python")
+         content = parser.get_code_outline(content, path=str(path))
+        elif suffix_lower in ['.c', '.h', '.cpp', '.hpp', '.cxx', '.cc']:
+         from src import mcp_client
+         if suffix_lower in ['.c', '.h']: content = mcp_client.ts_c_get_code_outline(str(path))
+         else: content = mcp_client.ts_cpp_get_code_outline(str(path))
+        else:
+         content = summarize.summarise_file(path, content)
+       elif view_mode == "masked":
+        suffix_lower = path.suffix.lower()
+        if ast_mask:
+         mask_sections = []
+         from src import mcp_client
+         for symbol, mode in ast_mask.items():
+          if mode == "hide": continue
+          res = ""
+          if suffix_lower == ".py":
+           res = mcp_client.py_get_definition(str(path), symbol) if mode == "def" else mcp_client.py_get_signature(str(path), symbol)
+          elif suffix_lower in [".c", ".h", ".cpp", ".hpp", ".cxx", ".cc"]:
+           is_cpp = any(ext in suffix_lower for ext in [".cpp", ".hpp", ".cxx", ".cc"])
+           if mode == "def":
+            res = mcp_client.ts_cpp_get_definition(str(path), symbol) if is_cpp else mcp_client.ts_c_get_definition(str(path), symbol)
+           else:
+            res = mcp_client.ts_cpp_get_signature(str(path), symbol) if is_cpp else mcp_client.ts_c_get_signature(str(path), symbol)
+          if res: mask_sections.append(res)
+         if mask_sections:
+          content = "\n\n".join(mask_sections)
+         else:
+          content = "(no masked sections visible)"
+        else:
+         content = "(no ast mask defined)"
+       elif view_mode == "none":
+        content = "(context excluded)"
+       elif view_mode == "custom":
+        if custom_slices:
+         lines = content.splitlines()
+         slices_text = []
+         for s in custom_slices:
+          start = s.get("start_line", 1)
+          end = s.get("end_line", len(lines))
+          tag = s.get("tag", "unnamed")
+          comment = s.get("comment", "")
+          s_idx = max(0, start - 1)
+          e_idx = min(len(lines), end)
+          chunk = "\n".join(lines[s_idx:e_idx])
+          slices_text.append(f"---\n[Slice: {tag}] ({comment})\nLines {start}-{end}:\n{chunk}")
+         content = "\n\n".join(slices_text)
+        else:
+         content = summarize.summarise_file(path, content)
+      except Exception as e:
+       import traceback
+       content = f"ERROR in {view_mode} view mode for {path}:\n{traceback.format_exc()}"
+       error = True
     except FileNotFoundError:
      content = f"ERROR: file not found: {path}"
      mtime = 0.0
      error = True
     except Exception as e:
-     content = f"ERROR: {e}"
+     import traceback
+     content = f"ERROR reading {path}:\n{traceback.format_exc()}"
      mtime = 0.0
      error = True
     items.append({"path": path, "entry": entry, "content": content, "error": error, "mtime": mtime, "tier": tier, "auto_aggregate": auto_aggregate, "force_full": force_full, "view_mode": view_mode, "ast_signatures": ast_signatures, "ast_definitions": ast_definitions, "ast_mask": ast_mask, "custom_slices": custom_slices})
diff --git a/src/app_controller.py b/src/app_controller.py
index f3f0040d..d6d99226 100644
--- a/src/app_controller.py
+++ b/src/app_controller.py
@@ -2929,29 +2929,20 @@ class AppController:
   if name not in presets:
    raise KeyError(f"Context preset '{name}' not found.")
   preset = presets[name]
-  # Apply it to the current state
-  self.ui_file_paths = [f.path for f in preset.files]
-  self.screenshots = list(preset.screenshots)
-  self._save_active_project()
-  # We need to tell gui_2 to populate the full FileItem state from the preset, 
-  # which it does in _handle_refresh_from_project. But we also need to pass the detailed properties.
-  # We will let the project_manager handle merging in the preset files via configuration next turn.
-  # Wait, project manager doesn't load preset files into self.files automatically here.
-  # Let's write the preset files into self.project["files"] directly.
-  import copy
-  self.project.setdefault("files", {})["paths"] = [
-   {
-    "path": f.path,
-    "view_mode": f.view_mode,
-    "custom_slices": copy.deepcopy(f.custom_slices),
-    "ast_mask": copy.deepcopy(f.ast_mask),
-    "ast_signatures": getattr(f, "ast_signatures", False),
-    "ast_definitions": getattr(f, "ast_definitions", False)
-   } for f in preset.files
-  ]
-  self._save_active_project()
-  return preset
 
+  # Update only temporary context state, not project files
+  import copy
+  self.context_files = []
+  for f in preset.files:
+   fi = models.FileItem(path=f.path, view_mode=f.view_mode)
+   fi.custom_slices = copy.deepcopy(f.custom_slices) if hasattr(f, 'custom_slices') else []
+   fi.ast_mask = copy.deepcopy(f.ast_mask) if hasattr(f, 'ast_mask') else {}
+   fi.ast_signatures = getattr(f, 'ast_signatures', False)
+   fi.ast_definitions = getattr(f, 'ast_definitions', False)
+   self.context_files.append(fi)
+
+  self.screenshots = list(preset.screenshots)
+  return preset
  def _cb_load_track(self, track_id: str) -> None:
   """
     [C: src/gui_2.py:App._render_mma_track_browser]
@@ -3459,11 +3450,19 @@ class AppController:
   models.save_config(self.config)
   track_id = self.active_track.id if self.active_track else None
   flat = project_manager.flat_config(self.project, self.active_discussion, track_id=track_id)
-  flat.setdefault("files", {})["paths"] = self.context_files
+  
+  import copy
+  flat["files"] = copy.copy(flat.get("files", {}))
+  flat["files"]["paths"] = self.context_files
 
-  # Configure MCP so that aggregate.py can fetch skeletons for external files (e.g. gencpp)
-  file_dicts = [f.to_dict() if hasattr(f, 'to_dict') else {"path": str(f)} for f in self.context_files]
-  mcp_client.configure(file_dicts, [self.active_project_root] if self.active_project_root else None)
+  import os
+  file_dicts = []
+  for f in self.context_files:
+   p = f.path if hasattr(f, 'path') else str(f)
+   if not os.path.isabs(p):
+    p = os.path.join(self.ui_files_base_dir, p)
+   file_dicts.append({"path": p})
+  mcp_client.configure(file_dicts, [self.ui_files_base_dir])
 
   persona = self.personas.get(self.ui_active_persona)
   strategy = persona.aggregation_strategy if persona else "auto"
diff --git a/src/gui_2.py b/src/gui_2.py
index e328deb4..71732077 100644
--- a/src/gui_2.py
+++ b/src/gui_2.py
@@ -627,7 +627,16 @@ class App:
     [C: tests/test_context_presets.py:test_load_context_preset, tests/test_context_presets.py:test_load_nonexistent_preset]
   """
   preset = self.controller.load_context_preset(name)
-  self.context_files = [models.FileItem(path=f.path, view_mode=f.view_mode) for f in preset.files]
+  from src import models
+  import copy
+  self.context_files = []
+  for f in preset.files:
+   fi = models.FileItem(path=f.path, view_mode=f.view_mode)
+   fi.custom_slices = copy.deepcopy(f.custom_slices) if hasattr(f, 'custom_slices') else []
+   fi.ast_mask = copy.deepcopy(f.ast_mask) if hasattr(f, 'ast_mask') else {}
+   fi.ast_signatures = getattr(f, 'ast_signatures', False)
+   fi.ast_definitions = getattr(f, 'ast_definitions', False)
+   self.context_files.append(fi)
   self.screenshots = list(preset.screenshots)
   self.ui_file_paths = [f.path for f in preset.files]
   self.ui_screenshot_paths = list(preset.screenshots)
@@ -3017,7 +3026,6 @@ def render_ast_inspector_modal(app: App) -> None:
         if imgui.is_item_hovered():
          app._hovered_ast_node = full_path
         
-        # Calculate space left and align radio buttons to the right
         btn_width = 150 # Estimated width of the 3 radio buttons
         avail_width = imgui.get_content_region_avail().x
         if avail_width > btn_width:
@@ -3255,7 +3263,6 @@ def render_context_files_table(app: App) -> None:
         imgui.text_colored(imgui.ImVec4(1.0, 0.5, 0.0, 1.0), "[Slices Active]")
 
 def render_context_presets(app: App) -> None:
- imgui.text("Presets")
  presets      = app.controller.project.get('context_presets', {})
  preset_names = [""] + sorted(presets.keys())
  active = getattr(app, "ui_active_context_preset", "")
@@ -3264,47 +3271,86 @@ def render_context_presets(app: App) -> None:
   idx = preset_names.index(active)
  except ValueError:
   idx = 0
- ch, new_idx = imgui.combo("##ctx_preset", idx, preset_names)
- if ch:
-  app.ui_active_context_preset = preset_names[new_idx]
-  if preset_names[new_idx]: app.load_context_preset(preset_names[new_idx])
- imgui.same_line()
- changed, new_name = imgui.input_text("##new_preset", getattr(app, "ui_new_context_preset_name", ""))
- if changed: app.ui_new_context_preset_name = new_name
- imgui.same_line()
- if imgui.button("Save##ctx") or getattr(app, "_pending_save_ctx_click", False):
-  app._pending_save_ctx_click = False
-  name = getattr(app, "ui_new_context_preset_name", "").strip()
-  if name:
-   missing = []
-   root = app.controller.active_project_root
-   for f in app.context_files:
-    path = f.path if hasattr(f, "path") else str(f)
-    if not os.path.isabs(path):
-     full_path = os.path.join(root, path)
-    else:
-     full_path = path
-    if not os.path.exists(full_path):
-     missing.append(path)
-
-   if missing:
-    app.missing_context_files = missing
-    app.show_missing_files_modal = True
-    app.target_context_preset_name = name
-   else:
+ 
+ with imscope.table("ctx_presets_layout", 2, imgui.TableFlags_.none):
+  imgui.table_next_column()
+  imgui.set_next_item_width(-1)
+  ch, new_idx = imgui.combo("##ctx_preset", idx, preset_names)
+  if ch:
+   app.ui_active_context_preset = preset_names[new_idx]
+   if preset_names[new_idx]:
+    app.controller.load_context_preset(preset_names[new_idx])
+    app.controller._refresh_from_project()
+    app.context_files = list(app.controller.files)
+  
+  imgui.table_next_column()
+  if active:
+   if imgui.button("Update##override", imgui.ImVec2(-1, 0)):
     preset_files = []
     for f in app.context_files:
+     import copy
+     from src import models
      p = f.path if hasattr(f, 'path') else str(f)
      vm = f.view_mode if hasattr(f, 'view_mode') else 'summary'
-     preset_files.append(models.ContextFileEntry(path=p, view_mode=vm))
-    preset = models.ContextPreset(name=name, files=preset_files, screenshots=list(app.screenshots))
+     slc = copy.deepcopy(f.custom_slices) if hasattr(f, 'custom_slices') else []
+     msk = copy.deepcopy(f.ast_mask) if hasattr(f, 'ast_mask') else {}
+     sig = f.ast_signatures if hasattr(f, 'ast_signatures') else False
+     dfn = f.ast_definitions if hasattr(f, 'ast_definitions') else False
+     preset_files.append(models.ContextFileEntry(path=p, view_mode=vm, custom_slices=slc, ast_mask=msk, ast_signatures=sig, ast_definitions=dfn))
+    preset = models.ContextPreset(name=active, files=preset_files, screenshots=list(app.screenshots))
     app.controller.save_context_preset(preset)
-    app.ui_new_context_preset_name = ""
- imgui.same_line()
- if imgui.button("Delete##ctx"):
-  if getattr(app, "ui_active_context_preset", ""):
-   app.delete_context_preset(app.ui_active_context_preset)
-   app.ui_active_context_preset = ""
+  else:
+   imgui.text_disabled("No active preset")
+
+  imgui.table_next_row()
+  imgui.table_next_column()
+  imgui.set_next_item_width(-1)
+  changed, new_name = imgui.input_text("##new_preset", getattr(app, "ui_new_context_preset_name", ""))
+  if changed: app.ui_new_context_preset_name = new_name
+  
+  imgui.table_next_column()
+  if imgui.button("Save As##ctx", imgui.ImVec2(-1, 0)) or getattr(app, "_pending_save_ctx_click", False):
+   app._pending_save_ctx_click = False
+   name = getattr(app, "ui_new_context_preset_name", "").strip()
+   if name:
+    missing = []
+    root = app.controller.active_project_root
+    for f in app.context_files:
+     path = f.path if hasattr(f, "path") else str(f)
+     if not os.path.isabs(path):
+      full_path = os.path.join(root, path)
+     else:
+      full_path = path
+     if not os.path.exists(full_path):
+      missing.append(path)
+
+    if missing:
+     app.missing_context_files = missing
+     app.show_missing_files_modal = True
+     app.target_context_preset_name = name
+    else:
+     preset_files = []
+     for f in app.context_files:
+      import copy
+      from src import models
+      p = f.path if hasattr(f, 'path') else str(f)
+      vm = f.view_mode if hasattr(f, 'view_mode') else 'summary'
+      slc = copy.deepcopy(f.custom_slices) if hasattr(f, 'custom_slices') else []
+      msk = copy.deepcopy(f.ast_mask) if hasattr(f, 'ast_mask') else {}
+      sig = f.ast_signatures if hasattr(f, 'ast_signatures') else False
+      dfn = f.ast_definitions if hasattr(f, 'ast_definitions') else False
+      preset_files.append(models.ContextFileEntry(path=p, view_mode=vm, custom_slices=slc, ast_mask=msk, ast_signatures=sig, ast_definitions=dfn))
+     preset = models.ContextPreset(name=name, files=preset_files, screenshots=list(app.screenshots))
+     app.controller.save_context_preset(preset)
+     app.ui_new_context_preset_name = ""
+
+  if active:
+   imgui.table_next_row()
+   imgui.table_next_column()
+   imgui.table_next_column()
+   if imgui.button("Delete Active", imgui.ImVec2(-1, 0)):
+    app.delete_context_preset(active)
+    app.ui_active_context_preset = ""
 
 def render_snapshot_tab(app: App) -> None:
  if imgui.begin_tab_bar("snapshot_tabs"):
@@ -5380,9 +5426,15 @@ def render_context_modals(app: App) -> None:
    name = app.target_context_preset_name
    preset_files = []
    for f in app.context_files:
+    import copy
+    from src import models
     p = f.path if hasattr(f, 'path') else str(f)
     vm = f.view_mode if hasattr(f, 'view_mode') else 'summary'
-    preset_files.append(models.ContextFileEntry(path=p, view_mode=vm))
+    slc = copy.deepcopy(f.custom_slices) if hasattr(f, 'custom_slices') else []
+    msk = copy.deepcopy(f.ast_mask) if hasattr(f, 'ast_mask') else {}
+    sig = f.ast_signatures if hasattr(f, 'ast_signatures') else False
+    dfn = f.ast_definitions if hasattr(f, 'ast_definitions') else False
+    preset_files.append(models.ContextFileEntry(path=p, view_mode=vm, custom_slices=slc, ast_mask=msk, ast_signatures=sig, ast_definitions=dfn))
    preset = models.ContextPreset(name=name, files=preset_files, screenshots=list(app.screenshots))
    app.controller.save_context_preset(preset)
    app.ui_new_context_preset_name = ""
diff --git a/src/summarize.py b/src/summarize.py
index 8abd33e3..84c18c38 100644
--- a/src/summarize.py
+++ b/src/summarize.py
@@ -22,7 +22,6 @@ For each file, extracts structural information:
 Returns a compact markdown string per file, suitable for use as a low-token
 context block that replaces full file contents in the initial <context> send.
 """
-
 import ast
 import re
 from pathlib import Path
@@ -42,7 +41,6 @@ def _summarise_python(path: Path, content: str) -> str:
  except SyntaxError as e:
   parts.append(f"_Parse error: {e}_")
   return "\n".join(parts)
-  # Imports
  imports = []
  for node in ast.walk(tree):
   if isinstance(node, ast.Import):
@@ -54,7 +52,6 @@ def _summarise_python(path: Path, content: str) -> str:
  if imports:
   unique_imports = sorted(set(imports))
   parts.append(f"imports: {', '.join(unique_imports)}")
-  # Top-level constants (ALL_CAPS assignments)
  constants = []
  for node in ast.iter_child_nodes(tree):
   if isinstance(node, ast.Assign):
@@ -66,7 +63,6 @@ def _summarise_python(path: Path, content: str) -> str:
     constants.append(node.target.id)
  if constants:
   parts.append(f"constants: {', '.join(constants)}")
-  # Classes + their methods
  for node in ast.iter_child_nodes(tree):
   if isinstance(node, ast.ClassDef):
    methods = [
@@ -77,7 +73,6 @@ def _summarise_python(path: Path, content: str) -> str:
     parts.append(f"class {node.name}: {', '.join(methods)}")
    else:
     parts.append(f"class {node.name}")
-    # Top-level functions
  top_fns = [
   node.name for node in ast.iter_child_nodes(tree)
   if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef))
@@ -90,7 +85,6 @@ def _summarise_toml(path: Path, content: str) -> str:
  lines = content.splitlines()
  line_count = len(lines)
  parts = [f"**TOML** — {line_count} lines"]
- # Extract top-level table headers [key] and [[key]]
  table_pat = re.compile(r"^\s*\[{1,2}([^\[\]]+)\]{1,2}")
  tables = []
  for line in lines:
@@ -99,7 +93,6 @@ def _summarise_toml(path: Path, content: str) -> str:
    tables.append(m.group(1).strip())
  if tables:
   parts.append(f"tables: {', '.join(tables)}")
-  # Top-level key = value (not inside a [table])
  kv_pat = re.compile(r"^([a-zA-Z_][a-zA-Z0-9_]*)\s*=")
  in_table = False
  top_keys = []
@@ -140,7 +133,6 @@ def _summarise_generic(path: Path, content: str) -> str:
  if preview:
   parts.append("preview:\n```\n" + "\n".join(preview) + "\n```")
  return "\n".join(parts)
- # ------------------------------------------------------------------ dispatch
 
 _SUMMARISERS: dict[str, Callable[[Path, str], str]] = {
  ".py":   _summarise_python,
@@ -148,6 +140,10 @@ _SUMMARISERS: dict[str, Callable[[Path, str], str]] = {
  ".md":   _summarise_markdown,
  ".ini":  _summarise_generic,
  ".txt":  _summarise_generic,
+ ".c":    _summarise_generic,
+ ".h":    _summarise_generic,
+ ".cpp":  _summarise_generic,
+ ".hpp":  _summarise_generic,
  ".ps1":  _summarise_generic,
 }
 
@@ -163,19 +159,17 @@ def summarise_file(path: Path, content: str) -> str:
  cached = _summary_cache.get_summary(str(path), content_hash)
  if cached:
   return cached
-
  suffix = path.suffix.lower() if hasattr(path, "suffix") else ""
  fn = _SUMMARISERS.get(suffix, _summarise_generic)
  try:
   heuristic_outline = fn(path, content)
-  
   # Smart AI Summarization
   is_code = suffix in [".py", ".ps1", ".js", ".ts", ".cpp", ".c", ".h", ".cs", ".go", ".rs", ".lua"]
   try:
    from src import ai_client
    smart_summary = ai_client.run_subagent_summarization(
     file_path=str(path),
-    content=content[:10000], # Cap content to 10k chars for summarization
+    content=content[:10000],
     is_code=is_code,
     outline=heuristic_outline
    )
@@ -184,8 +178,7 @@ def summarise_file(path: Path, content: str) -> str:
    else:
     summary = heuristic_outline
   except Exception:
-   summary = heuristic_outline # Fallback
-  
+   summary = heuristic_outline
   _summary_cache.set_summary(str(path), content_hash, summary)
   return summary
  except Exception as e: