diff --git a/.pr/evidence/01_home.png b/.pr/evidence/01_home.png
new file mode 100644
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diff --git a/.pr/evidence/02_after_reload.png b/.pr/evidence/02_after_reload.png
new file mode 100644
index 0000000000..2b7da8ccc5
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diff --git a/.pr/evidence/03_conversation.png b/.pr/evidence/03_conversation.png
new file mode 100644
index 0000000000..afb36bb689
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diff --git a/.pr/evidence/04_negative_rejection.png b/.pr/evidence/04_negative_rejection.png
new file mode 100644
index 0000000000..2e867eac28
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diff --git a/.pr/evidence/05_reply.png b/.pr/evidence/05_reply.png
new file mode 100644
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diff --git a/frontend/__tests__/components/features/conversation-panel/conversation-card.test.tsx b/frontend/__tests__/components/features/conversation-panel/conversation-card.test.tsx
index 850263e25e..0acab01a61 100644
--- a/frontend/__tests__/components/features/conversation-panel/conversation-card.test.tsx
+++ b/frontend/__tests__/components/features/conversation-panel/conversation-card.test.tsx
@@ -16,6 +16,7 @@ import { ConversationCard } from "#/components/features/conversation-panel/conve
 import { clickOnEditButton } from "./utils";
 import { ConversationCardActions } from "#/components/features/conversation-panel/conversation-card/conversation-card-actions";
 import { V1SandboxStatus } from "#/api/sandbox-service/sandbox-service.types";
+import ConversationService from "#/api/conversation-service/conversation-service.api";
 
 vi.mock("react-i18next", async () => {
   const actual = await vi.importActual("react-i18next");
@@ -352,6 +353,69 @@ describe("ConversationCard", () => {
     expect(onClick).not.toHaveBeenCalled();
   });
 
+  it("opens the VS Code URL without an opener reference", async () => {
+    const user = userEvent.setup();
+    const vscodeUrl = "https://vscode.example.dev/?tkn=abc&folder=workspace";
+    vi.spyOn(ConversationService, "getVSCodeUrl").mockResolvedValue({
+      vscode_url: vscodeUrl,
+    });
+    renderWithProviders(
+      <ConversationCard
+        conversationId="conv-1"
+        onDelete={onDelete}
+        title="Conversation 1"
+        selectedRepository={null}
+        lastUpdatedAt="2021-10-01T12:00:00Z"
+        showOptions
+        contextMenuOpen
+        onContextMenuToggle={vi.fn()}
+      />,
+    );
+
+    await user.click(
+      within(screen.getByTestId("context-menu")).getByTestId(
+        "download-vscode-button",
+      ),
+    );
+
+    await vi.waitFor(() =>
+      expect(window.open).toHaveBeenCalledWith(
+        vscodeUrl,
+        "_blank",
+        "noopener,noreferrer",
+      ),
+    );
+  });
+
+  it("does not open a non-http(s) VS Code URL", async () => {
+    const user = userEvent.setup();
+    const getVSCodeUrl = vi
+      .spyOn(ConversationService, "getVSCodeUrl")
+      // eslint-disable-next-line no-script-url
+      .mockResolvedValue({ vscode_url: "javascript:alert(1)" });
+    renderWithProviders(
+      <ConversationCard
+        conversationId="conv-1"
+        onDelete={onDelete}
+        title="Conversation 1"
+        selectedRepository={null}
+        lastUpdatedAt="2021-10-01T12:00:00Z"
+        showOptions
+        contextMenuOpen
+        onContextMenuToggle={vi.fn()}
+      />,
+    );
+
+    await user.click(
+      within(screen.getByTestId("context-menu")).getByTestId(
+        "download-vscode-button",
+      ),
+    );
+
+    await vi.waitFor(() => expect(getVSCodeUrl).toHaveBeenCalledWith("conv-1"));
+    expect(window.open).not.toHaveBeenCalled();
+  });
+
   it("should not display the edit or delete options if the handler is not provided", async () => {
     const onContextMenuToggle = vi.fn();
     const { rerender } = renderWithProviders(
@@ -486,7 +550,7 @@ describe("ConversationCard", () => {
     (sandboxStatus, shouldShow) => {
       renderWithProviders(
         <ConversationCardActions
-          contextMenuOpen={true}
+          contextMenuOpen
           onContextMenuToggle={vi.fn()}
           onStop={vi.fn()}
           sandboxStatus={sandboxStatus}
diff --git a/frontend/__tests__/hooks/query/use-unified-vscode-url.test.tsx b/frontend/__tests__/hooks/query/use-unified-vscode-url.test.tsx
new file mode 100644
index 0000000000..86df6f9614
--- /dev/null
+++ b/frontend/__tests__/hooks/query/use-unified-vscode-url.test.tsx
@@ -0,0 +1,81 @@
+import { renderHook, waitFor } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import React from "react";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { useUnifiedVSCodeUrl } from "#/hooks/query/use-unified-vscode-url";
+import { useBatchAppConversations } from "#/hooks/query/use-batch-app-conversations";
+import { useBatchSandboxes } from "#/hooks/query/use-batch-sandboxes";
+import { I18nKey } from "#/i18n/declaration";
+
+vi.mock("#/hooks/use-conversation-id", () => ({
+  useConversationId: () => ({ conversationId: "conv-1" }),
+}));
+vi.mock("#/hooks/use-runtime-is-ready", () => ({
+  useRuntimeIsReady: () => true,
+}));
+vi.mock("#/hooks/query/use-batch-app-conversations");
+vi.mock("#/hooks/query/use-batch-sandboxes");
+
+const createWrapper = () => {
+  const queryClient = new QueryClient({
+    defaultOptions: { queries: { retry: false } },
+  });
+  function Wrapper({ children }: { children: React.ReactNode }) {
+    return (
+      <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>
+    );
+  }
+  return Wrapper;
+};
+
+function mockSandboxVSCodeUrl(url: string) {
+  vi.mocked(useBatchAppConversations).mockReturnValue({
+    data: [{ sandbox_id: "sb-1" }],
+    isLoading: false,
+  } as unknown as ReturnType<typeof useBatchAppConversations>);
+  vi.mocked(useBatchSandboxes).mockReturnValue({
+    data: [{ id: "sb-1", exposed_urls: [{ name: "VSCODE", url }] }],
+    isLoading: false,
+  } as unknown as ReturnType<typeof useBatchSandboxes>);
+}
+
+describe("useUnifiedVSCodeUrl", () => {
+  afterEach(() => {
+    vi.resetAllMocks();
+  });
+
+  it("returns an http(s) sandbox VS Code URL", async () => {
+    mockSandboxVSCodeUrl("https://vscode.example.dev/?tkn=abc");
+
+    const { result } = renderHook(() => useUnifiedVSCodeUrl(), {
+      wrapper: createWrapper(),
+    });
+
+    await waitFor(() =>
+      expect(result.current.data).toEqual({
+        url: "https://vscode.example.dev/?tkn=abc",
+        error: null,
+      }),
+    );
+  });
+
+  it.each([
+    // eslint-disable-next-line no-script-url
+    "javascript:alert(1)",
+    "data:text/html,<script>alert(1)</script>",
+    "not-a-valid-url",
+  ])("reports %s as not available", async (url) => {
+    mockSandboxVSCodeUrl(url);
+
+    const { result } = renderHook(() => useUnifiedVSCodeUrl(), {
+      wrapper: createWrapper(),
+    });
+
+    await waitFor(() =>
+      expect(result.current.data).toEqual({
+        url: null,
+        error: I18nKey.VSCODE$URL_NOT_AVAILABLE,
+      }),
+    );
+  });
+});
diff --git a/frontend/__tests__/routes/accept-tos.test.tsx b/frontend/__tests__/routes/accept-tos.test.tsx
index 27b5fb130f..1329660270 100644
--- a/frontend/__tests__/routes/accept-tos.test.tsx
+++ b/frontend/__tests__/routes/accept-tos.test.tsx
@@ -83,7 +83,12 @@ describe("AcceptTOS", () => {
   beforeEach(() => {
     sessionStorage.clear();
     useSelectedOrganizationStore.setState({ organizationId: "test-org-id" });
-    vi.stubGlobal("location", { href: "" });
+    vi.stubGlobal("location", {
+      href: "",
+      origin: "http://localhost",
+      pathname: "/accept-tos",
+      search: "",
+    });
   });
 
   afterEach(() => {
diff --git a/frontend/__tests__/utils/vscode-url-helper.test.ts b/frontend/__tests__/utils/vscode-url-helper.test.ts
index a55b03bbbf..f181564321 100644
--- a/frontend/__tests__/utils/vscode-url-helper.test.ts
+++ b/frontend/__tests__/utils/vscode-url-helper.test.ts
@@ -56,6 +56,16 @@ describe("transformVSCodeUrl", () => {
   it("should handle invalid URLs gracefully", () => {
     const input = "not-a-valid-url";
 
-    expect(transformVSCodeUrl(input)).toBe(input);
+    expect(transformVSCodeUrl(input)).toBeNull();
+  });
+
+  it.each([
+    "not-a-valid-url",
+    // eslint-disable-next-line no-script-url
+    "javascript:alert(1)",
+    "data:text/html,<script>alert(1)</script>",
+    "file:///etc/passwd",
+  ])("should reject %s", (input) => {
+    expect(transformVSCodeUrl(input)).toBeNull();
   });
 });
diff --git a/frontend/src/components/features/conversation-panel/conversation-card/conversation-card.tsx b/frontend/src/components/features/conversation-panel/conversation-card/conversation-card.tsx
index ee4474cc59..3dcb3fba59 100644
--- a/frontend/src/components/features/conversation-panel/conversation-card/conversation-card.tsx
+++ b/frontend/src/components/features/conversation-panel/conversation-card/conversation-card.tsx
@@ -90,7 +90,7 @@ export function ConversationCard({
         if (data.vscode_url) {
           const transformedUrl = transformVSCodeUrl(data.vscode_url);
           if (transformedUrl) {
-            window.open(transformedUrl, "_blank");
+            window.open(transformedUrl, "_blank", "noopener,noreferrer");
           }
         }
         // VS Code URL not available
diff --git a/frontend/src/hooks/query/use-unified-vscode-url.ts b/frontend/src/hooks/query/use-unified-vscode-url.ts
index ddc9be3783..00123caffe 100644
--- a/frontend/src/hooks/query/use-unified-vscode-url.ts
+++ b/frontend/src/hooks/query/use-unified-vscode-url.ts
@@ -59,10 +59,15 @@ export const useUnifiedVSCodeUrl = () => {
         };
       }
 
-      return {
-        url: transformVSCodeUrl(vscodeUrl.url),
-        error: null,
-      };
+      const url = transformVSCodeUrl(vscodeUrl.url);
+      if (!url) {
+        return {
+          url: null,
+          error: I18nKey.VSCODE$URL_NOT_AVAILABLE,
+        };
+      }
+
+      return { url, error: null };
     },
     enabled: runtimeIsReady && !!conversationId && !!sandboxesQuery.data,
     refetchOnMount: true,
diff --git a/frontend/src/utils/vscode-url-helper.ts b/frontend/src/utils/vscode-url-helper.ts
index 21f32a66a8..b2c75d4121 100644
--- a/frontend/src/utils/vscode-url-helper.ts
+++ b/frontend/src/utils/vscode-url-helper.ts
@@ -1,31 +1,37 @@
+const ALLOWED_PROTOCOLS = new Set(["http:", "https:"]);
+
 /**
  * Helper function to transform VS Code URLs
  *
  * This function checks if a VS Code URL points to localhost and replaces it with
- * the current window's hostname if they don't match.
+ * the current window's hostname if they don't match. URLs that do not parse or
+ * are not http(s) are rejected, since the value comes from the backend and is
+ * opened in a new tab.
  *
  * @param vsCodeUrl The original VS Code URL from the backend
- * @returns The transformed URL with the correct hostname
+ * @returns The transformed URL with the correct hostname, or null if rejected
  */
 export function transformVSCodeUrl(vsCodeUrl: string | null): string | null {
   if (!vsCodeUrl) return null;
 
+  let url: URL;
   try {
-    const url = new URL(vsCodeUrl);
+    url = new URL(vsCodeUrl);
+  } catch {
+    return null;
+  }
 
-    // Check if the URL points to localhost
-    if (
-      url.hostname === "localhost" &&
-      window.location.hostname !== "localhost"
-    ) {
-      // Replace localhost with the current hostname
-      url.hostname = window.location.hostname;
-      return url.toString();
-    }
+  if (!ALLOWED_PROTOCOLS.has(url.protocol)) return null;
 
-    return vsCodeUrl;
-  } catch {
-    // Silently handle the error and return the original URL
-    return vsCodeUrl;
+  // Check if the URL points to localhost
+  if (
+    url.hostname === "localhost" &&
+    window.location.hostname !== "localhost"
+  ) {
+    // Replace localhost with the current hostname
+    url.hostname = window.location.hostname;
+    return url.toString();
   }
+
+  return vsCodeUrl;
 }