diff --git a/webui/src/components/thread/PromptNavigator.tsx b/webui/src/components/thread/PromptNavigator.tsx
index 2e618bd18..aa1bf318a 100644
--- a/webui/src/components/thread/PromptNavigator.tsx
+++ b/webui/src/components/thread/PromptNavigator.tsx
@@ -47,23 +47,19 @@ export function PromptNavigator({
 
   return (
     <>
-      <div
-        className="pointer-events-none absolute right-3 top-2 z-20"
+      <Button
+        type="button"
+        variant="ghost"
+        size="icon"
+        className={cn(
+          "host-no-drag h-8 w-8 rounded-full text-muted-foreground/80",
+          "hover:bg-accent/40 hover:text-foreground",
+        )}
+        aria-label={t("thread.promptNavigator.open")}
+        onClick={() => setOpen(true)}
       >
-        <Button
-          type="button"
-          variant="ghost"
-          size="icon"
-          className={cn(
-            "pointer-events-auto h-8 w-8 rounded-full text-muted-foreground/80",
-            "hover:bg-accent/40 hover:text-foreground",
-          )}
-          aria-label={t("thread.promptNavigator.open")}
-          onClick={() => setOpen(true)}
-        >
-          <ListTree className="h-4 w-4" />
-        </Button>
-      </div>
+        <ListTree className="h-4 w-4" />
+      </Button>
 
       <Sheet open={open} onOpenChange={setOpen}>
         <SheetContent
diff --git a/webui/src/components/thread/ThreadHeader.tsx b/webui/src/components/thread/ThreadHeader.tsx
index c3a8a1806..26e3ce82b 100644
--- a/webui/src/components/thread/ThreadHeader.tsx
+++ b/webui/src/components/thread/ThreadHeader.tsx
@@ -14,6 +14,7 @@ interface ThreadHeaderProps {
   hostChromeTitleInset?: boolean;
   hideThemeButton?: boolean;
   minimal?: boolean;
+  promptNavigatorAction?: ReactNode;
   sessionInfoAction?: ReactNode;
 }
 
@@ -26,6 +27,7 @@ export function ThreadHeader({
   hostChromeTitleInset = false,
   hideThemeButton = false,
   minimal = false,
+  promptNavigatorAction,
   sessionInfoAction,
 }: ThreadHeaderProps) {
   const { t } = useTranslation();
@@ -60,6 +62,7 @@ export function ThreadHeader({
 
       <div className="ml-auto flex shrink-0 items-center gap-1">
         {sessionInfoAction}
+        {promptNavigatorAction}
         {!hideThemeButton ? (
           <ThemeButton
             theme={theme}
diff --git a/webui/src/components/thread/ThreadShell.tsx b/webui/src/components/thread/ThreadShell.tsx
index 22dac883d..6c96558f1 100644
--- a/webui/src/components/thread/ThreadShell.tsx
+++ b/webui/src/components/thread/ThreadShell.tsx
@@ -3,11 +3,12 @@ import type { PointerEvent as ReactPointerEvent } from "react";
 import { useTranslation } from "react-i18next";
 
 import { FilePreviewPanel } from "@/components/FilePreviewPanel";
+import { PromptNavigator } from "@/components/thread/PromptNavigator";
 import { SessionInfoPopover } from "@/components/thread/SessionInfoPopover";
 import { ThreadComposer } from "@/components/thread/ThreadComposer";
 import { ThreadHeader } from "@/components/thread/ThreadHeader";
 import { StreamErrorNotice } from "@/components/thread/StreamErrorNotice";
-import { ThreadViewport } from "@/components/thread/ThreadViewport";
+import { ThreadViewport, type ThreadViewportHandle } from "@/components/thread/ThreadViewport";
 import { useNanobotStream, type SendImage, type SendOptions } from "@/hooks/useNanobotStream";
 import { useSessionHistory } from "@/hooks/useSessions";
 import { fetchCliApps, fetchMcpPresets, fetchSettings, listSlashCommands } from "@/lib/api";
@@ -211,6 +212,7 @@ export function ThreadShell({
   const filePreviewWidthRef = useRef(FILE_PREVIEW_DEFAULT_WIDTH);
   const filePreviewCloseTimerRef = useRef<number | null>(null);
   const pendingFirstRef = useRef<PendingFirstMessage | null>(null);
+  const viewportRef = useRef<ThreadViewportHandle | null>(null);
   const messageCacheRef = useRef<Map<string, UIMessage[]>>(new Map());
   /** Last chatId we associated with the in-memory thread (for cache-on-switch). */
   const prevChatIdForCacheRef = useRef<string | null>(null);
@@ -717,6 +719,12 @@ export function ThreadShell({
   const sessionInfoAction = historyKey ? (
     <SessionInfoPopover sessionKey={historyKey} token={token} title={title} />
   ) : undefined;
+  const promptNavigatorAction = historyKey ? (
+    <PromptNavigator
+      messages={displayMessages}
+      onJumpToPrompt={(promptId) => viewportRef.current?.jumpToUserPrompt(promptId)}
+    />
+  ) : undefined;
 
   return (
     <section ref={shellRef} className="relative flex min-h-0 flex-1 overflow-hidden">
@@ -731,10 +739,12 @@ export function ThreadShell({
             hostChromeTitleInset={hostChromeTitleInset}
             hideThemeButton={hideThemeButton}
             minimal={!session && !loading}
+            promptNavigatorAction={promptNavigatorAction}
             sessionInfoAction={sessionInfoAction}
           />
         ) : null}
         <ThreadViewport
+          ref={viewportRef}
           messages={displayMessages}
           isStreaming={isStreaming}
           emptyState={emptyState}
diff --git a/webui/src/components/thread/ThreadViewport.tsx b/webui/src/components/thread/ThreadViewport.tsx
index 2a278f9f7..a0b01ef52 100644
--- a/webui/src/components/thread/ThreadViewport.tsx
+++ b/webui/src/components/thread/ThreadViewport.tsx
@@ -1,7 +1,9 @@
 import {
+  forwardRef,
   type ReactNode,
   useCallback,
   useEffect,
+  useImperativeHandle,
   useLayoutEffect,
   useMemo,
   useRef,
@@ -10,7 +12,6 @@ import {
 import { ArrowDown } from "lucide-react";
 import { useTranslation } from "react-i18next";
 
-import { PromptNavigator } from "@/components/thread/PromptNavigator";
 import { PromptRail } from "@/components/thread/PromptRail";
 import { ThreadMessages } from "@/components/thread/ThreadMessages";
 import { isAgentActivityMember } from "@/components/thread/AgentActivityCluster";
@@ -22,6 +23,10 @@ import {
 import { cn } from "@/lib/utils";
 import type { CliAppInfo, McpPresetInfo, UIMessage } from "@/lib/types";
 
+export interface ThreadViewportHandle {
+  jumpToUserPrompt: (promptId: string) => void;
+}
+
 interface ThreadViewportProps {
   messages: UIMessage[];
   isStreaming: boolean;
@@ -54,7 +59,7 @@ export function windowMessages(messages: UIMessage[], visibleCount: number): UIM
   return messages.slice(start);
 }
 
-export function ThreadViewport({
+export const ThreadViewport = forwardRef<ThreadViewportHandle, ThreadViewportProps>(function ThreadViewport({
   messages,
   isStreaming,
   composer,
@@ -65,7 +70,7 @@ export function ThreadViewport({
   cliApps = [],
   mcpPresets = [],
   onOpenFilePreview,
-}: ThreadViewportProps) {
+}, ref) {
   const { t } = useTranslation();
   const scrollRef = useRef<HTMLDivElement>(null);
   const contentRef = useRef<HTMLDivElement>(null);
@@ -161,6 +166,8 @@ export function ThreadViewport({
     setVisibleMessageCount((count) => Math.max(count, messages.length - index));
   }, [messages]);
 
+  useImperativeHandle(ref, () => ({ jumpToUserPrompt }), [jumpToUserPrompt]);
+
   const measureComposerDock = useCallback(() => {
     const el = composerDockRef.current;
     if (!el) return;
@@ -330,13 +337,6 @@ export function ThreadViewport({
         />
       ) : null}
 
-      {hasMessages ? (
-        <PromptNavigator
-          messages={messages}
-          onJumpToPrompt={jumpToUserPrompt}
-        />
-      ) : null}
-
       {showScrollToBottomButton && !atBottom && (
         <Button
           variant="outline"
@@ -356,4 +356,4 @@ export function ThreadViewport({
       )}
     </div>
   );
-}
+});
diff --git a/webui/src/tests/thread-viewport.test.tsx b/webui/src/tests/thread-viewport.test.tsx
index cc73b6db4..88a71089d 100644
--- a/webui/src/tests/thread-viewport.test.tsx
+++ b/webui/src/tests/thread-viewport.test.tsx
@@ -1,10 +1,13 @@
+import { useRef } from "react";
 import { act, fireEvent, render, screen, waitFor, within } from "@testing-library/react";
 import { describe, expect, it, vi } from "vitest";
 
+import { PromptNavigator } from "@/components/thread/PromptNavigator";
 import {
   HISTORY_WINDOW_INCREMENT,
   INITIAL_HISTORY_WINDOW,
   ThreadViewport,
+  type ThreadViewportHandle,
   windowMessages,
 } from "@/components/thread/ThreadViewport";
 import type { UIMessage } from "@/lib/types";
@@ -35,6 +38,24 @@ function makeLongMessages(count: number): UIMessage[] {
   }));
 }
 
+function ViewportWithPromptNavigator({ messages }: { messages: UIMessage[] }) {
+  const viewportRef = useRef<ThreadViewportHandle | null>(null);
+  return (
+    <div>
+      <PromptNavigator
+        messages={messages}
+        onJumpToPrompt={(promptId) => viewportRef.current?.jumpToUserPrompt(promptId)}
+      />
+      <ThreadViewport
+        ref={viewportRef}
+        messages={messages}
+        isStreaming={false}
+        composer={<div />}
+      />
+    </div>
+  );
+}
+
 describe("ThreadViewport", () => {
   it("keeps the scroll-to-bottom button above a growing composer", () => {
     const originalResizeObserver = globalThis.ResizeObserver;
@@ -220,15 +241,9 @@ describe("ThreadViewport", () => {
 
   it("opens a prompt navigator list and jumps to a selected prompt", async () => {
     const promptMessages = makeLongMessages(5);
-    const { container } = render(
-      <ThreadViewport
-        messages={promptMessages}
-        isStreaming={false}
-        composer={<div />}
-      />,
-    );
+    const { container } = render(<ViewportWithPromptNavigator messages={promptMessages} />);
 
-    const scroller = container.firstElementChild?.firstElementChild as HTMLElement;
+    const scroller = container.querySelector(".thread-viewport-scrollbar") as HTMLElement;
     const scrollTo = vi.fn();
     Object.defineProperties(scroller, {
       scrollHeight: { configurable: true, value: 1800 },
@@ -267,13 +282,7 @@ describe("ThreadViewport", () => {
 
   it("expands the history window before jumping to an older prompt from the navigator", async () => {
     const longMessages = makeLongMessages(300);
-    render(
-      <ThreadViewport
-        messages={longMessages}
-        isStreaming={false}
-        composer={<div />}
-      />,
-    );
+    render(<ViewportWithPromptNavigator messages={longMessages} />);
 
     expect(screen.queryByText("message 20")).not.toBeInTheDocument();