diff --git a/src/sw/sw-viewer.stories.tsx b/src/sw/sw-viewer.stories.tsx
index 07f377a..bcd9a1e 100644
--- a/src/sw/sw-viewer.stories.tsx
+++ b/src/sw/sw-viewer.stories.tsx
@@ -30,11 +30,11 @@ function Log({ lines }: { lines: string[] }) {
 }
 
 /** A viewer screen: header on top, the drawing area below it (panels are placed inside this frame). */
-function ViewerFrame({ width = 1440, height = 620, children, header }: { width?: number; height?: number; header: ReactNode; children?: ReactNode }) {
+function ViewerFrame({ width = 1440, height = 620, children, header }: { width?: number | null; height?: number; header: ReactNode; children?: ReactNode }) {
   return (
     <div className="sw-story-scroller">
-      {/* Fills the Story column up to `width`, so panels placed at the right edge stay visible. */}
-      <div className="sw-viewer-story-frame" style={{ width: "100%", maxWidth: width, height }} data-viewer-frame="">
+      {/* Fills the Story column up to `width` (null: the whole column), so panels placed at the right edge stay visible. */}
+      <div className="sw-viewer-story-frame" style={{ width: "100%", maxWidth: width ?? undefined, height }} data-viewer-frame="">
         {header}
         <div className="sw-viewer-story-canvas" aria-label="도면 영역 (예시)">{children}</div>
       </div>
@@ -58,7 +58,8 @@ function AboutPanel({ demo }: { demo: ViewerDemo }) {
   )
 }
 
-function ViewerScreen({ width = 1440, initialDocument = SAMPLES[1].name as string | null, open = [] as ("layers" | "options" | "properties")[], windowControls = false }) {
+// 2026-10-22 (user request): the Viewer Header screens have no 1440px maximum; they fill the Story column.
+function ViewerScreen({ width = null as number | null, initialDocument = SAMPLES[1].name as string | null, open = [] as ("layers" | "options" | "properties")[], windowControls = false }) {
   const demo = useViewerDemo({ initialDocument, initialPanels: open })
   // 2026-10-21 new viewer version: SWHeader's own minimize / close (SWHeaderWindowControls, same icons, size, hover)
   // at the right end after the existing trailing items (the `trailing` slot, no new API). The program owns the real