test(frontend): add useChatSession + ChatMessagesContainer coverage tests

- useChatSession.test.ts: 5 tests for newestSequence and forwardPaginated memos
- ChatMessagesContainer.test.tsx: 5 tests verifying top/bottom sentinel placement
  based on forwardPaginated prop

autogpt_platform/frontend/src/app/(platform)/copilot/__tests__/useChatSession.test.ts

@@ -0,0 +1,122 @@
+import { renderHook } from "@testing-library/react";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { useChatSession } from "../useChatSession";
+
+const mockUseGetV2GetSession = vi.fn();
+
+vi.mock("@/app/api/__generated__/endpoints/chat/chat", () => ({
+  useGetV2GetSession: (...args: unknown[]) => mockUseGetV2GetSession(...args),
+  usePostV2CreateSession: () => ({ mutateAsync: vi.fn(), isPending: false }),
+  getGetV2GetSessionQueryKey: (id: string) => ["session", id],
+  getGetV2ListSessionsQueryKey: () => ["sessions"],
+}));
+
+vi.mock("@tanstack/react-query", () => ({
+  useQueryClient: () => ({
+    invalidateQueries: vi.fn(),
+    setQueryData: vi.fn(),
+  }),
+}));
+
+vi.mock("nuqs", () => ({
+  parseAsString: { withDefault: (v: unknown) => v },
+  useQueryState: () => ["sess-1", vi.fn()],
+}));
+
+vi.mock("../helpers/convertChatSessionToUiMessages", () => ({
+  convertChatSessionMessagesToUiMessages: vi.fn(() => ({
+    messages: [],
+    historicalDurations: new Map(),
+  })),
+}));
+
+vi.mock("../helpers", () => ({
+  resolveSessionDryRun: vi.fn(() => false),
+}));
+
+vi.mock("@sentry/nextjs", () => ({
+  captureException: vi.fn(),
+}));
+
+function makeQueryResult(data: object | null) {
+  return {
+    data: data ? { status: 200, data } : undefined,
+    isLoading: false,
+    isError: false,
+    isFetching: false,
+    refetch: vi.fn(),
+  };
+}
+
+describe("useChatSession — newestSequence and forwardPaginated", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("returns null / false when no session data", () => {
+    mockUseGetV2GetSession.mockReturnValue(makeQueryResult(null));
+    const { result } = renderHook(() => useChatSession());
+    expect(result.current.newestSequence).toBeNull();
+    expect(result.current.forwardPaginated).toBe(false);
+  });
+
+  it("returns newestSequence from session data", () => {
+    mockUseGetV2GetSession.mockReturnValue(
+      makeQueryResult({
+        messages: [],
+        has_more_messages: true,
+        oldest_sequence: 0,
+        newest_sequence: 99,
+        forward_paginated: false,
+        active_stream: null,
+      }),
+    );
+    const { result } = renderHook(() => useChatSession());
+    expect(result.current.newestSequence).toBe(99);
+  });
+
+  it("returns null for newestSequence when field is missing", () => {
+    mockUseGetV2GetSession.mockReturnValue(
+      makeQueryResult({
+        messages: [],
+        has_more_messages: false,
+        oldest_sequence: 0,
+        newest_sequence: null,
+        forward_paginated: false,
+        active_stream: null,
+      }),
+    );
+    const { result } = renderHook(() => useChatSession());
+    expect(result.current.newestSequence).toBeNull();
+  });
+
+  it("returns forwardPaginated=true when session is forward-paginated", () => {
+    mockUseGetV2GetSession.mockReturnValue(
+      makeQueryResult({
+        messages: [],
+        has_more_messages: true,
+        oldest_sequence: 0,
+        newest_sequence: 49,
+        forward_paginated: true,
+        active_stream: null,
+      }),
+    );
+    const { result } = renderHook(() => useChatSession());
+    expect(result.current.forwardPaginated).toBe(true);
+  });
+
+  it("returns forwardPaginated=false when session is backward-paginated", () => {
+    mockUseGetV2GetSession.mockReturnValue(
+      makeQueryResult({
+        messages: [],
+        has_more_messages: true,
+        oldest_sequence: 50,
+        newest_sequence: 99,
+        forward_paginated: false,
+        active_stream: null,
+      }),
+    );
+    const { result } = renderHook(() => useChatSession());
+    expect(result.current.forwardPaginated).toBe(false);
+  });
+});

autogpt_platform/frontend/src/app/(platform)/copilot/components/ChatMessagesContainer/__tests__/ChatMessagesContainer.test.tsx

@@ -0,0 +1,173 @@
+import { render, screen, cleanup } from "@/tests/integrations/test-utils";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { ChatMessagesContainer } from "../ChatMessagesContainer";
+
+const mockScrollEl = {
+  scrollHeight: 100,
+  scrollTop: 0,
+  clientHeight: 500,
+};
+
+vi.mock("use-stick-to-bottom", () => ({
+  useStickToBottomContext: () => ({ scrollRef: { current: mockScrollEl } }),
+  Conversation: ({ children }: { children: React.ReactNode }) => (
+    <div>{children}</div>
+  ),
+  ConversationContent: ({ children }: { children: React.ReactNode }) => (
+    <div>{children}</div>
+  ),
+  ConversationScrollButton: () => null,
+}));
+
+vi.mock("@/components/ai-elements/conversation", () => ({
+  Conversation: ({ children }: { children: React.ReactNode }) => (
+    <div>{children}</div>
+  ),
+  ConversationContent: ({ children }: { children: React.ReactNode }) => (
+    <div>{children}</div>
+  ),
+  ConversationScrollButton: () => null,
+}));
+
+vi.mock("@/components/ai-elements/message", () => ({
+  Message: ({ children }: { children: React.ReactNode }) => (
+    <div>{children}</div>
+  ),
+  MessageContent: ({ children }: { children: React.ReactNode }) => (
+    <div>{children}</div>
+  ),
+  MessageActions: ({ children }: { children: React.ReactNode }) => (
+    <div>{children}</div>
+  ),
+}));
+
+vi.mock("../components/AssistantMessageActions", () => ({
+  AssistantMessageActions: () => null,
+}));
+vi.mock("../components/CopyButton", () => ({ CopyButton: () => null }));
+vi.mock("../components/CollapsedToolGroup", () => ({
+  CollapsedToolGroup: () => null,
+}));
+vi.mock("../components/MessageAttachments", () => ({
+  MessageAttachments: () => null,
+}));
+vi.mock("../components/MessagePartRenderer", () => ({
+  MessagePartRenderer: () => null,
+}));
+vi.mock("../components/ReasoningCollapse", () => ({
+  ReasoningCollapse: () => null,
+}));
+vi.mock("../components/ThinkingIndicator", () => ({
+  ThinkingIndicator: () => null,
+}));
+vi.mock("../../JobStatsBar/TurnStatsBar", () => ({
+  TurnStatsBar: () => null,
+}));
+vi.mock("../../JobStatsBar/useElapsedTimer", () => ({
+  useElapsedTimer: () => ({ elapsedSeconds: 0 }),
+}));
+vi.mock("../../CopilotPendingReviews/CopilotPendingReviews", () => ({
+  CopilotPendingReviews: () => null,
+}));
+vi.mock("../helpers", () => ({
+  buildRenderSegments: () => [],
+  getTurnMessages: () => [],
+  parseSpecialMarkers: () => ({ markerType: null }),
+  splitReasoningAndResponse: (parts: unknown[]) => ({
+    reasoningParts: [],
+    responseParts: parts,
+  }),
+}));
+
+type ObserverCallback = (entries: { isIntersecting: boolean }[]) => void;
+class MockIntersectionObserver {
+  static lastCallback: ObserverCallback | null = null;
+  private callback: ObserverCallback;
+  constructor(cb: ObserverCallback) {
+    this.callback = cb;
+    MockIntersectionObserver.lastCallback = cb;
+  }
+  observe() {}
+  disconnect() {}
+  unobserve() {}
+  takeRecords() {
+    return [];
+  }
+  root = null;
+  rootMargin = "";
+  thresholds = [];
+}
+
+const BASE_PROPS = {
+  messages: [],
+  status: "ready" as const,
+  error: undefined,
+  isLoading: false,
+  sessionID: "sess-1",
+  hasMoreMessages: true,
+  isLoadingMore: false,
+  onLoadMore: vi.fn(),
+  onRetry: vi.fn(),
+};
+
+describe("ChatMessagesContainer", () => {
+  beforeEach(() => {
+    mockScrollEl.scrollHeight = 100;
+    mockScrollEl.scrollTop = 0;
+    mockScrollEl.clientHeight = 500;
+    MockIntersectionObserver.lastCallback = null;
+    vi.stubGlobal("IntersectionObserver", MockIntersectionObserver);
+  });
+
+  afterEach(() => {
+    cleanup();
+    vi.unstubAllGlobals();
+  });
+
+  it("renders top sentinel when forwardPaginated is false (backward pagination)", () => {
+    render(<ChatMessagesContainer {...BASE_PROPS} forwardPaginated={false} />);
+    expect(
+      screen.getByRole("button", { name: /load older messages/i }),
+    ).toBeDefined();
+  });
+
+  it("renders top sentinel when forwardPaginated is undefined (default, backward)", () => {
+    render(<ChatMessagesContainer {...BASE_PROPS} />);
+    expect(
+      screen.getByRole("button", { name: /load older messages/i }),
+    ).toBeDefined();
+  });
+
+  it("renders bottom sentinel when forwardPaginated is true (forward pagination)", () => {
+    render(<ChatMessagesContainer {...BASE_PROPS} forwardPaginated={true} />);
+    expect(
+      screen.getByRole("button", { name: /load older messages/i }),
+    ).toBeDefined();
+  });
+
+  it("hides sentinel when hasMoreMessages is false", () => {
+    render(
+      <ChatMessagesContainer
+        {...BASE_PROPS}
+        hasMoreMessages={false}
+        forwardPaginated={true}
+      />,
+    );
+    expect(
+      screen.queryByRole("button", { name: /load older messages/i }),
+    ).toBeNull();
+  });
+
+  it("hides sentinel when onLoadMore is not provided", () => {
+    render(
+      <ChatMessagesContainer
+        {...BASE_PROPS}
+        onLoadMore={undefined}
+        forwardPaginated={true}
+      />,
+    );
+    expect(
+      screen.queryByRole("button", { name: /load older messages/i }),
+    ).toBeNull();
+  });
+});