diff --git a/Dockerfile b/Dockerfile
index f300729..dbecfc7 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -38,6 +38,18 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     curl \
     plantuml \
     jq \
+    nano \
+    # GUI dependencies for dearpygui
+    libgl1 \
+    libegl1 \
+    libxkbcommon0 \
+    libxcb-cursor0 \
+    libxcb-icccm4 \
+    libxcb-keysyms1 \
+    libxcb-shape0 \
+    libxcb-xinerama0 \
+    libxcb-randr0 \
+    libxcb-render-util0 \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app
@@ -59,6 +71,9 @@ COPY tests/ ./tests/
 # Install Orchestrated Discussions
 RUN pip install --no-cache-dir -e ".[dev]"
 
+# Install dearpygui for GUI (optional, may fail on some systems)
+RUN pip install --no-cache-dir dearpygui || echo "dearpygui install failed, GUI will use TUI fallback"
+
 # Create directories
 RUN mkdir -p /root/.smarttools /root/.local/bin
 
diff --git a/src/discussions/runner.py b/src/discussions/runner.py
index 7693f50..970b3d8 100644
--- a/src/discussions/runner.py
+++ b/src/discussions/runner.py
@@ -246,12 +246,16 @@ class VariableStore:
         else:
             self._store[name] = value
 
-    def get(self, ref: str):
+    def get(self, ref: str, default=None):
         """
         Get a variable value. Ref can be:
         - $varname - simple lookup
         - $varname.field - JSON field access
         - $varname.field.subfield - nested access
+
+        Args:
+            ref: Variable reference (e.g., "$varname" or "$varname.field")
+            default: Default value if variable not found
         """
         if not ref.startswith("$"):
             return ref  # Literal value
@@ -261,7 +265,7 @@ class VariableStore:
 
         value = self._store.get(parts[0])
         if value is None:
-            return None
+            return default
 
         # Navigate nested fields
         for part in parts[1:]:
@@ -271,9 +275,9 @@ class VariableStore:
                 idx = int(part)
                 value = value[idx] if idx < len(value) else None
             else:
-                return None
+                return default
             if value is None:
-                return None
+                return default
 
         return value