diff --git a/apps/portal/src/components/HarNetworkViewer.stories.tsx b/apps/portal/src/components/HarNetworkViewer.stories.tsx
new file mode 100644
index 00000000..b280e342
--- /dev/null
+++ b/apps/portal/src/components/HarNetworkViewer.stories.tsx
@@ -0,0 +1,74 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+import type { Meta, StoryObj } from "@storybook/react-vite";
+import { http, HttpResponse } from "msw";
+import { HarNetworkViewer } from "./HarNetworkViewer";
+
+const base = new Date("2026-06-21T12:00:00Z").getTime();
+const methods = ["GET", "POST", "GET", "PUT", "GET", "DELETE"];
+
+// Enough rows that the table is much taller than the viewport, plus a large
+// JSON body so the detail panel's own content has to scroll.
+const sampleHar = {
+  log: {
+    entries: Array.from({ length: 60 }, (_, i) => ({
+      startedDateTime: new Date(base + i * 250).toISOString(),
+      time: 40 + ((i * 37) % 900),
+      request: {
+        method: methods[i % methods.length],
+        url: `https://api.example.com/v1/items/${i}?page=${i % 5}`,
+        headers: [
+          { name: "accept", value: "application/json" },
+          { name: "user-agent", value: "scope-worker/1.0" },
+        ],
+        ...(i % 2 === 1 && {
+          postData: { mimeType: "application/json", text: JSON.stringify({ id: i, name: `item-${i}` }) },
+        }),
+      },
+      response: {
+        status: i % 13 === 0 ? 500 : i % 7 === 0 ? 404 : 200,
+        statusText: i % 13 === 0 ? "Internal Server Error" : i % 7 === 0 ? "Not Found" : "OK",
+        headers: Array.from({ length: 12 }, (_, h) => ({ name: `x-header-${h}`, value: `value-${i}-${h}` })),
+        content: {
+          size: 512 + i * 128,
+          mimeType: "application/json",
+          text: JSON.stringify({ id: i, items: Array.from({ length: 40 }, (_, n) => ({ n, label: `row ${n}` })) }),
+        },
+      },
+    })),
+  },
+};
+
+const harHandler = http.get("*/api/v1/requests/:id/har", () => HttpResponse.json(sampleHar));
+
+const meta = {
+  component: HarNetworkViewer,
+  tags: ["ai-generated", "needs-work"],
+  parameters: {
+    layout: "fullscreen",
+    msw: { handlers: [harHandler] },
+  },
+  // Stand-in for the portal's sticky 3rem app header (see Layout.tsx), so the
+  // detail panel's sticky offset renders the way it does in the portal.
+  decorators: [
+    (Story) => (
+      <>
+        <div className="sticky top-0 z-50 flex h-12 items-center border-b border-border/60 bg-background px-3 text-sm text-muted-foreground">
+          App header
+        </div>
+        <div className="w-full px-6 py-6 lg:px-8">
+          <Story />
+        </div>
+      </>
+    ),
+  ],
+} satisfies Meta<typeof HarNetworkViewer>;
+
+export default meta;
+type Story = StoryObj<typeof meta>;
+
+/** Scroll down and select a lower row: the detail panel should stay in view. */
+export const LongList: Story = {
+  args: { runId: "demo-run" },
+};
diff --git a/apps/portal/src/components/HarNetworkViewer.tsx b/apps/portal/src/components/HarNetworkViewer.tsx
index 9ca527ad..315d41fe 100644
--- a/apps/portal/src/components/HarNetworkViewer.tsx
+++ b/apps/portal/src/components/HarNetworkViewer.tsx
@@ -329,7 +329,7 @@ function DetailPanel({ entry, onClose }: { entry: HarEntry; onClose: () => void
   const responseBody = decodeBody(entry.response.content);
 
   return (
-    <div className="w-1/2 flex flex-col max-h-[600px]">
+    <div className="w-1/2 flex flex-col self-start sticky top-12 max-h-[calc(100vh-3rem)] border-b">
       {/* Panel header */}
       <div className="flex items-center justify-between px-3 py-2 border-b bg-muted/30">
         <div className="flex items-center gap-2">