diff --git a/docs/APP_REFACTORING_DESIGN.md b/docs/APP_REFACTORING_DESIGN.md
index fabd800..c41db0d 100644
--- a/docs/APP_REFACTORING_DESIGN.md
+++ b/docs/APP_REFACTORING_DESIGN.md
@@ -91,7 +91,7 @@ To refactor `app.tsx` safely and maintain continuous code correctness, we will m
 
 #### Phase 3: Shifting to URL as Single Source of Truth
 We will gradually eliminate React state variables in `src/app.tsx` and derive them (including settings like `standalone`, `showWikiTreeMenus`, and `freezeAnimation`) directly from the `useLocation()` search query parameters on render:
-*   [ ] **Step 3.1a:** Shift `chartType` to URL as SSOT. Derive it using `useMemo` from search parameters, replace calls to `setChartType` with URL updates, and remove the React state variable and sync effect.
+*   [x] **Step 3.1a:** Shift `chartType` to URL as SSOT. Derive it using `useMemo` from search parameters, replace calls to `setChartType` with URL updates, and remove the React state variable and sync effect.
 *   [ ] **Step 3.1b:** Shift `standalone` to URL as SSOT. Derive it directly from search parameters on render and remove its React state variable.
 *   [ ] **Step 3.1c:** Shift `showWikiTreeMenus` to URL as SSOT. Derive it directly from search parameters on render and remove its React state variable.
 *   [ ] **Step 3.1d:** Shift `freezeAnimation` to URL as SSOT. Derive it directly from search parameters on render and remove its React state variable.
diff --git a/src/app.tsx b/src/app.tsx
index 7fb17b0..dc00f16 100644
--- a/src/app.tsx
+++ b/src/app.tsx
@@ -98,8 +98,7 @@ export function App() {
    * from WikiTree.
    */
   const [showWikiTreeMenus, setShowWikiTreeMenus] = useState(true);
-  /** Type of displayed chart. */
-  const [chartType, setChartType] = useState<ChartType>(ChartType.Hourglass);
+
   /** Whether to show the error popup. */
   const [showErrorPopup, setShowErrorPopup] = useState(false);
   /** Specification of the source of the data. */
@@ -122,6 +121,10 @@ export function App() {
   const navigate = useNavigate();
   const location = useLocation();
 
+  const args = useMemo(() => getArguments(location), [location]);
+  /** Type of displayed chart. */
+  const chartType = args.chartType;
+
   /** Prevents the Google Drive "Open with" state from being processed more than once. */
   const stateProcessed = useRef(false);
   /** Tracks whether the component is currently mounted to prevent state updates after unmount. */
@@ -353,7 +356,6 @@ export function App() {
         setDetailIndi(args.selection?.id);
         setStandalone(args.standalone);
         setShowWikiTreeMenus(args.showWikiTreeMenus);
-        setChartType(args.chartType);
         setFreezeAnimation(args.freezeAnimation);
         setConfig(args.config);
         const currentFetchId = ++fetchIdRef.current;
@@ -399,7 +401,6 @@ export function App() {
         const loadMoreFromWikitree =
           args.sourceSpec.source === DataSourceEnum.WIKITREE &&
           (!selection || selection.id !== args.selection?.id);
-        setChartType(args.chartType);
         setState(
           loadMoreFromWikitree ? AppState.LOADING_MORE : AppState.SHOWING_CHART,
         );