fix(webui): compact single-pane chat header

webui/src/App.tsx

@@ -2816,6 +2816,7 @@ function Shell({
                       hostChromeTitleInset={hostSidebarCollapsed}
                       hideThemeButton={!context.active}
                       hideHeaderTitle
+                      inlineHandle={workbenchPaneSessions.length > 1}
                       headerActions={context.headerActions}
                       headerPortalTarget={context.headerPortalTarget}
                       headerActive={context.active}

webui/src/components/thread/ThreadShell.tsx

@@ -346,6 +346,7 @@ interface ThreadShellProps {
   hostChromeTitleInset?: boolean;
   hideThemeButton?: boolean;
   hideHeaderTitle?: boolean;
+  inlineHandle?: boolean;
   hideHeader?: boolean;
   headerActions?: ReactNode;
   headerPortalTarget?: HTMLElement | null;
@@ -645,6 +646,7 @@ export function ThreadShell({
   hostChromeTitleInset = false,
   hideThemeButton = false,
   hideHeaderTitle = false,
+  inlineHandle = false,
   hideHeader = false,
   headerActions,
   headerPortalTarget,
@@ -1614,7 +1616,7 @@ export function ThreadShell({
   const threadHeader = !hideHeader ? (
     <ThreadHeader
       title={title}
-      handle={temporary || hideHeaderTitle ? null : session?.handle}
+      handle={temporary || (hideHeaderTitle && inlineHandle) ? null : session?.handle}
       onToggleSidebar={onToggleSidebar}
       theme={theme}
       onToggleTheme={onToggleTheme}
@@ -1638,7 +1640,7 @@ export function ThreadShell({
   return (
     <section ref={shellRef} className="relative flex min-h-0 flex-1 overflow-hidden">
       <div className="relative flex min-w-0 flex-1 flex-col overflow-hidden">
-        {hideHeaderTitle && !temporary && session?.handle ? (
+        {hideHeaderTitle && inlineHandle && !temporary && session?.handle ? (
           <div
             aria-label={`Session @${session.handle.name}`}
             className="flex h-8 shrink-0 items-center px-3 text-[12px]"

webui/src/tests/thread-shell.test.tsx

@@ -417,6 +417,52 @@ describe("ThreadShell", () => {
     );
   });
 
+  it("moves the session handle into the pane only when the workbench is split", () => {
+    const client = makeClient();
+    const portal = document.createElement("div");
+    document.body.append(portal);
+    const activeSession = {
+      ...session("pane-handle"),
+      handle: {
+        id: "handle_11111111111111111111111111111111",
+        name: "soro",
+      },
+    };
+
+    const { unmount } = render(wrap(
+      client,
+      <ThreadShell
+        session={activeSession}
+        title="Single pane"
+        onToggleSidebar={() => {}}
+        hideHeaderTitle
+        headerPortalTarget={portal}
+      />,
+    ));
+
+    expect(within(portal).getByText("@soro")).toBeInTheDocument();
+    expect(screen.queryByLabelText("Session @soro")).not.toBeInTheDocument();
+
+    unmount();
+    const splitView = render(wrap(
+      client,
+      <ThreadShell
+        session={activeSession}
+        title="Split pane"
+        onToggleSidebar={() => {}}
+        hideHeaderTitle
+        inlineHandle
+        headerPortalTarget={portal}
+      />,
+    ));
+
+    expect(screen.getByLabelText("Session @soro")).toHaveTextContent("@soro");
+    expect(within(portal).queryByText("@soro")).not.toBeInTheDocument();
+
+    splitView.unmount();
+    portal.remove();
+  });
+
   it("keeps inferred file paths non-interactive when the availability probe fails", async () => {
     await preloadMarkdownText();
     const client = makeClient();