stack/apps/web/src/hooks/useChat.test.ts

/**
 * @file useChat.test.ts
 * @description Tests for the useChat hook that manages chat state and LLM interactions
 */

import { renderHook, act } from "@testing-library/react";
import { describe, it, expect, beforeEach, vi, afterEach, type MockedFunction } from "vitest";
import { useChat, type Message } from "./useChat";
import * as chatApi from "@/lib/api/chat";
import * as ideasApi from "@/lib/api/ideas";
import type { Idea } from "@/lib/api/ideas";
import type { ChatResponse } from "@/lib/api/chat";

// Mock the API modules - use importOriginal to preserve types/enums
vi.mock("@/lib/api/chat", () => ({
  sendChatMessage: vi.fn(),
  streamChatMessage: vi.fn(),
}));

vi.mock("@/lib/api/ideas", async (importOriginal) => {
  // eslint-disable-next-line @typescript-eslint/consistent-type-imports
  const actual = await importOriginal<typeof import("@/lib/api/ideas")>();
  return {
    ...actual,
    createConversation: vi.fn(),
    updateConversation: vi.fn(),
    getIdea: vi.fn(),
  };
});

const mockSendChatMessage = chatApi.sendChatMessage as MockedFunction<
  typeof chatApi.sendChatMessage
>;
const mockStreamChatMessage = chatApi.streamChatMessage as MockedFunction<
  typeof chatApi.streamChatMessage
>;
const mockCreateConversation = ideasApi.createConversation as MockedFunction<
  typeof ideasApi.createConversation
>;
const mockUpdateConversation = ideasApi.updateConversation as MockedFunction<
  typeof ideasApi.updateConversation
>;
const mockGetIdea = ideasApi.getIdea as MockedFunction<typeof ideasApi.getIdea>;

/**
 * Creates a mock ChatResponse
 */
function createMockChatResponse(content: string, model = "llama3.2"): ChatResponse {
  return {
    message: { role: "assistant" as const, content },
    model,
    done: true,
    promptEvalCount: 10,
    evalCount: 5,
  };
}

/**
 * Creates a mock Idea
 */
function createMockIdea(id: string, title: string, content: string): Idea {
  return {
    id,
    workspaceId: "workspace-1",
    title,
    content,
    status: "CAPTURED",
    priority: "medium",
    tags: ["chat"],
    metadata: { conversationType: "chat" },
    creatorId: "user-1",
    createdAt: new Date().toISOString(),
    updatedAt: new Date().toISOString(),
  } as Idea;
}

/**
 * Configure streamChatMessage to immediately fail,
 * triggering the fallback to sendChatMessage.
 */
function makeStreamFail(): void {
  mockStreamChatMessage.mockImplementation(
    (
      _request,
      _onChunk,
      _onComplete,
      onError: (err: Error) => void,
      _signal?: AbortSignal
    ): void => {
      // Call synchronously so the Promise rejects immediately
      onError(new Error("Streaming not available"));
    }
  );
}

/**
 * Configure streamChatMessage to succeed with given tokens.
 * Uses a ref-style object to share cancellation state across the async boundary.
 */
function makeStreamSucceed(tokens: string[]): void {
  mockStreamChatMessage.mockImplementation(
    (
      _request,
      onChunk: (chunk: string) => void,
      onComplete: () => void,
      _onError: (err: Error) => void,
      signal?: AbortSignal
    ): void => {
      const state = { cancelled: false };
      signal?.addEventListener("abort", () => {
        state.cancelled = true;
      });
      const run = async (): Promise<void> => {
        for (const token of tokens) {
          if (state.cancelled) return;
          await Promise.resolve();
          onChunk(token);
        }
        if (!state.cancelled) {
          onComplete();
        }
      };
      void run();
    }
  );
}

describe("useChat", () => {
  beforeEach(() => {
    vi.clearAllMocks();
    // Default: streaming fails so tests exercise the fallback path
    makeStreamFail();
  });

  afterEach(() => {
    vi.restoreAllMocks();
  });

  describe("initial state", () => {
    it("should initialize with welcome message", () => {
      const { result } = renderHook(() => useChat());

      expect(result.current.messages).toHaveLength(1);
      expect(result.current.messages[0]?.role).toBe("assistant");
      expect(result.current.messages[0]?.id).toBe("welcome");
      expect(result.current.isLoading).toBe(false);
      expect(result.current.isStreaming).toBe(false);
      expect(result.current.error).toBeNull();
      expect(result.current.conversationId).toBeNull();
    });

    it("should expose abortStream function", () => {
      const { result } = renderHook(() => useChat());
      expect(typeof result.current.abortStream).toBe("function");
    });
  });

  describe("sendMessage (fallback path when streaming fails)", () => {
    it("should add user message and assistant response via fallback", async () => {
      mockSendChatMessage.mockResolvedValueOnce(createMockChatResponse("Hello there!"));
      mockCreateConversation.mockResolvedValueOnce(createMockIdea("conv-1", "Test", ""));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("Hello");
      });

      expect(result.current.messages).toHaveLength(3); // welcome + user + assistant
      expect(result.current.messages[1]?.role).toBe("user");
      expect(result.current.messages[1]?.content).toBe("Hello");
      expect(result.current.messages[2]?.role).toBe("assistant");
      expect(result.current.messages[2]?.content).toBe("Hello there!");
    });

    it("should not send empty messages", async () => {
      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("");
        await result.current.sendMessage("   ");
      });

      expect(mockSendChatMessage).not.toHaveBeenCalled();
      expect(mockStreamChatMessage).not.toHaveBeenCalled();
      expect(result.current.messages).toHaveLength(1); // only welcome
    });

    it("should handle API errors gracefully", async () => {
      vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      mockSendChatMessage.mockRejectedValueOnce(new Error("API Error"));

      const onError = vi.fn();
      const { result } = renderHook(() => useChat({ onError }));

      await act(async () => {
        await result.current.sendMessage("Hello");
      });

      expect(result.current.error).toBe("Unable to send message. Please try again.");
      expect(onError).toHaveBeenCalledWith(expect.any(Error));
      expect(result.current.messages).toHaveLength(3);
      expect(result.current.messages[2]?.content).toBe("Something went wrong. Please try again.");
    });
  });

  describe("streaming path", () => {
    it("should stream tokens into assistant message", async () => {
      const tokens = ["Hello", " world", "!"];
      makeStreamSucceed(tokens);
      mockCreateConversation.mockResolvedValueOnce(createMockIdea("conv-1", "Test", ""));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("Hi");
      });

      expect(result.current.messages).toHaveLength(3);
      expect(result.current.messages[2]?.role).toBe("assistant");
      expect(result.current.messages[2]?.content).toBe("Hello world!");
    });

    it("should set isStreaming true during streaming then false when done", async () => {
      let capturedOnChunk: ((chunk: string) => void) | undefined;
      let capturedOnComplete: (() => void) | undefined;

      mockStreamChatMessage.mockImplementation(
        (
          _request,
          onChunk: (chunk: string) => void,
          onComplete: () => void,
          _onError: (err: Error) => void
        ): void => {
          capturedOnChunk = onChunk;
          capturedOnComplete = onComplete;
        }
      );

      mockCreateConversation.mockResolvedValueOnce(createMockIdea("conv-1", "Test", ""));

      const { result } = renderHook(() => useChat());

      let sendDone = false;
      act(() => {
        void result.current.sendMessage("Hello").then(() => {
          sendDone = true;
        });
      });

      // Send first token (triggers streaming state)
      await act(async () => {
        capturedOnChunk?.("Hello");
        await Promise.resolve();
      });

      expect(result.current.isStreaming).toBe(true);

      // Complete the stream
      await act(async () => {
        capturedOnComplete?.();
        await Promise.resolve();
        await Promise.resolve();
        await Promise.resolve();
      });

      expect(result.current.isStreaming).toBe(false);
      expect(sendDone).toBe(true);
    });

    it("should keep partial content on abort", async () => {
      let capturedOnChunk: ((chunk: string) => void) | undefined;

      mockStreamChatMessage.mockImplementation(
        (
          _request,
          onChunk: (chunk: string) => void,
          _onComplete: () => void,
          _onError: (err: Error) => void,
          signal?: AbortSignal
        ): void => {
          capturedOnChunk = onChunk;
          if (signal) {
            signal.addEventListener("abort", () => {
              // Stream aborted
            });
          }
        }
      );

      const { result } = renderHook(() => useChat());

      act(() => {
        void result.current.sendMessage("Hello");
      });

      await act(async () => {
        capturedOnChunk?.("Partial");
        capturedOnChunk?.(" content");
        await Promise.resolve();
      });

      await act(async () => {
        result.current.abortStream();
        await Promise.resolve();
      });

      expect(result.current.isStreaming).toBe(false);
      const assistantMsg = result.current.messages.find(
        (m) => m.role === "assistant" && m.id !== "welcome"
      );
      expect(assistantMsg?.content).toBe("Partial content");
    });

    it("should not send while streaming", async () => {
      let capturedOnChunk: ((chunk: string) => void) | undefined;

      mockStreamChatMessage.mockImplementation(
        (
          _request,
          onChunk: (chunk: string) => void,
          _onComplete: () => void,
          _onError: (err: Error) => void
        ): void => {
          capturedOnChunk = onChunk;
        }
      );

      const { result } = renderHook(() => useChat());

      act(() => {
        void result.current.sendMessage("First");
      });

      await act(async () => {
        capturedOnChunk?.("token");
        await Promise.resolve();
      });

      expect(result.current.isStreaming).toBe(true);

      await act(async () => {
        await result.current.sendMessage("Second");
      });

      // Only one stream call
      expect(mockStreamChatMessage).toHaveBeenCalledTimes(1);
    });
  });

  describe("rapid sends - stale closure prevention", () => {
    it("should not lose messages on rapid sequential sends", async () => {
      // Use streaming success path for deterministic behavior
      makeStreamSucceed(["Response 1"]);

      mockCreateConversation.mockResolvedValue(createMockIdea("conv-1", "Test", ""));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("Message 1");
      });

      expect(result.current.messages).toHaveLength(3); // welcome + user1 + assistant1

      makeStreamSucceed(["Response 2"]);

      await act(async () => {
        await result.current.sendMessage("Message 2");
      });

      expect(result.current.messages).toHaveLength(5); // welcome + user1 + assistant1 + user2 + assistant2

      const userMessages = result.current.messages.filter((m) => m.role === "user");
      expect(userMessages).toHaveLength(2);
      expect(userMessages[0]?.content).toBe("Message 1");
      expect(userMessages[1]?.content).toBe("Message 2");
    });

    it("should use functional updates for all message state changes", async () => {
      mockCreateConversation.mockResolvedValue(createMockIdea("conv-1", "Test", ""));

      const { result } = renderHook(() => useChat());

      const messageCounts: number[] = [];

      makeStreamSucceed(["R1"]);
      await act(async () => {
        await result.current.sendMessage("Test 1");
      });
      messageCounts.push(result.current.messages.length);

      makeStreamSucceed(["R2"]);
      await act(async () => {
        await result.current.sendMessage("Test 2");
      });
      messageCounts.push(result.current.messages.length);

      makeStreamSucceed(["R3"]);
      await act(async () => {
        await result.current.sendMessage("Test 3");
      });
      messageCounts.push(result.current.messages.length);

      expect(messageCounts).toEqual([3, 5, 7]);
      expect(result.current.messages).toHaveLength(7);
      const userMessages = result.current.messages.filter((m) => m.role === "user");
      expect(userMessages).toHaveLength(3);
    });

    it("should maintain correct message order with ref-based state tracking", async () => {
      mockCreateConversation.mockResolvedValue(createMockIdea("conv-1", "Test", ""));

      const { result } = renderHook(() => useChat());

      makeStreamSucceed(["First response"]);
      await act(async () => {
        await result.current.sendMessage("Query 1");
      });

      makeStreamSucceed(["Second response"]);
      await act(async () => {
        await result.current.sendMessage("Query 2");
      });

      makeStreamSucceed(["Third response"]);
      await act(async () => {
        await result.current.sendMessage("Query 3");
      });

      const messages = result.current.messages;
      expect(messages[0]?.id).toBe("welcome");
      expect(messages[1]?.content).toBe("Query 1");
      expect(messages[2]?.content).toBe("First response");
      expect(messages[3]?.content).toBe("Query 2");
      expect(messages[4]?.content).toBe("Second response");
      expect(messages[5]?.content).toBe("Query 3");
      expect(messages[6]?.content).toBe("Third response");
    });
  });

  describe("loadConversation", () => {
    it("should load conversation from backend", async () => {
      const savedMessages: Message[] = [
        {
          id: "msg-1",
          role: "user",
          content: "Saved message",
          createdAt: new Date().toISOString(),
        },
        {
          id: "msg-2",
          role: "assistant",
          content: "Saved response",
          createdAt: new Date().toISOString(),
        },
      ];

      mockGetIdea.mockResolvedValueOnce(
        createMockIdea("conv-123", "My Conversation", JSON.stringify(savedMessages))
      );

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.loadConversation("conv-123");
      });

      expect(result.current.messages).toHaveLength(2);
      expect(result.current.messages[0]?.content).toBe("Saved message");
      expect(result.current.conversationId).toBe("conv-123");
      expect(result.current.conversationTitle).toBe("My Conversation");
    });

    it("should fall back to welcome message when stored JSON is corrupted", async () => {
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      mockGetIdea.mockResolvedValueOnce(
        createMockIdea("conv-bad", "Corrupted", "not valid json {{{")
      );

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.loadConversation("conv-bad");
      });

      expect(result.current.messages).toHaveLength(1);
      expect(result.current.messages[0]?.id).toBe("welcome");
    });

    it("should fall back to welcome message when stored data has wrong shape", async () => {
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      mockGetIdea.mockResolvedValueOnce(
        createMockIdea("conv-bad", "Wrong Shape", JSON.stringify({ not: "an array" }))
      );

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.loadConversation("conv-bad");
      });

      expect(result.current.messages).toHaveLength(1);
      expect(result.current.messages[0]?.id).toBe("welcome");
    });

    it("should fall back to welcome message when messages have invalid roles", async () => {
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      const badMessages = [
        { id: "msg-1", role: "hacker", content: "Bad", createdAt: "2026-01-01" },
      ];
      mockGetIdea.mockResolvedValueOnce(
        createMockIdea("conv-bad", "Bad Roles", JSON.stringify(badMessages))
      );

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.loadConversation("conv-bad");
      });

      expect(result.current.messages).toHaveLength(1);
      expect(result.current.messages[0]?.id).toBe("welcome");
    });

    it("should set sanitized error and call onError when getIdea rejects", async () => {
      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => undefined);
      mockGetIdea.mockRejectedValueOnce(new Error("Not found"));

      const onError = vi.fn();
      const { result } = renderHook(() => useChat({ onError }));

      await act(async () => {
        await result.current.loadConversation("conv-missing");
      });

      expect(result.current.error).toBe("Unable to load conversation. Please try again.");
      expect(onError).toHaveBeenCalledWith(expect.any(Error));
      expect(consoleSpy).toHaveBeenCalledWith(
        "Failed to load conversation",
        expect.objectContaining({
          errorType: "LOAD_ERROR",
          ideaId: "conv-missing",
          timestamp: expect.any(String) as string,
        })
      );
      expect(result.current.isLoading).toBe(false);
    });

    it("should not re-throw when getIdea rejects", async () => {
      vi.spyOn(console, "error").mockImplementation(() => undefined);
      mockGetIdea.mockRejectedValueOnce(new Error("Server error"));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await expect(result.current.loadConversation("conv-err")).resolves.toBeUndefined();
      });

      expect(result.current.error).toBe("Unable to load conversation. Please try again.");
    });
  });

  describe("startNewConversation", () => {
    it("should reset to initial state", async () => {
      makeStreamSucceed(["Response"]);
      mockCreateConversation.mockResolvedValueOnce(createMockIdea("conv-1", "Test", ""));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("Hello");
      });

      expect(result.current.messages.length).toBeGreaterThan(1);

      act(() => {
        result.current.startNewConversation();
      });

      expect(result.current.messages).toHaveLength(1);
      expect(result.current.messages[0]?.id).toBe("welcome");
      expect(result.current.conversationId).toBeNull();
      expect(result.current.conversationTitle).toBeNull();
    });
  });

  describe("clearError", () => {
    it("should clear error state", async () => {
      vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      mockSendChatMessage.mockRejectedValueOnce(new Error("Test error"));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("Hello");
      });

      expect(result.current.error).toBe("Unable to send message. Please try again.");

      act(() => {
        result.current.clearError();
      });

      expect(result.current.error).toBeNull();
    });
  });

  describe("error context logging", () => {
    it("should log comprehensive error context when sendMessage fails", async () => {
      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      mockSendChatMessage.mockRejectedValueOnce(new Error("LLM timeout"));

      const { result } = renderHook(() => useChat({ model: "llama3.2" }));

      await act(async () => {
        await result.current.sendMessage("Hello world");
      });

      expect(consoleSpy).toHaveBeenCalledWith(
        "Failed to send chat message",
        expect.objectContaining({
          errorType: "LLM_ERROR",
          messageLength: 11,
          messagePreview: "Hello world",
          model: "llama3.2",
          timestamp: expect.any(String) as string,
        })
      );
    });

    it("should truncate long message previews to 50 characters", async () => {
      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      mockSendChatMessage.mockRejectedValueOnce(new Error("Failed"));

      const longMessage = "A".repeat(100);
      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage(longMessage);
      });

      expect(consoleSpy).toHaveBeenCalledWith(
        "Failed to send chat message",
        expect.objectContaining({
          messagePreview: "A".repeat(50),
          messageLength: 100,
        })
      );
    });

    it("should include message count in error context", async () => {
      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);

      // First successful message via streaming
      makeStreamSucceed(["OK"]);
      mockCreateConversation.mockResolvedValueOnce(createMockIdea("conv-1", "Test", ""));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("First");
      });

      // Second message: streaming fails, fallback fails
      makeStreamFail();
      mockSendChatMessage.mockRejectedValueOnce(new Error("Fail"));

      await act(async () => {
        await result.current.sendMessage("Second");
      });

      expect(consoleSpy).toHaveBeenCalledWith(
        "Failed to send chat message",
        expect.objectContaining({
          messageCount: expect.any(Number) as number,
        })
      );
    });
  });

  describe("LLM vs persistence error separation", () => {
    it("should show LLM error and add error message to chat when API fails", async () => {
      vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      mockSendChatMessage.mockRejectedValueOnce(new Error("Model not available"));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("Hello");
      });

      expect(result.current.error).toBe("Unable to send message. Please try again.");
      expect(result.current.messages).toHaveLength(3);
      expect(result.current.messages[2]?.content).toBe("Something went wrong. Please try again.");
    });

    it("should keep assistant message visible when save fails (streaming path)", async () => {
      vi.spyOn(console, "error").mockImplementation(() => undefined);
      makeStreamSucceed(["Great answer!"]);
      mockCreateConversation.mockRejectedValueOnce(new Error("Database connection lost"));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("Hello");
      });

      expect(result.current.messages).toHaveLength(3); // welcome + user + assistant
      expect(result.current.messages[2]?.content).toBe("Great answer!");
      expect(result.current.error).toContain("Message sent but failed to save");
    });

    it("should keep assistant message visible when save fails (fallback path)", async () => {
      vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      mockSendChatMessage.mockResolvedValueOnce(createMockChatResponse("Great answer!"));
      mockCreateConversation.mockRejectedValueOnce(new Error("Database connection lost"));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("Hello");
      });

      expect(result.current.messages).toHaveLength(3);
      expect(result.current.messages[2]?.content).toBe("Great answer!");
      expect(result.current.error).toContain("Message sent but failed to save");
    });

    it("should log with PERSISTENCE_ERROR type when save fails", async () => {
      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      mockSendChatMessage.mockResolvedValueOnce(createMockChatResponse("Response"));
      mockCreateConversation.mockRejectedValueOnce(new Error("DB error"));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("Test");
      });

      expect(consoleSpy).toHaveBeenCalledWith(
        "Failed to save conversation",
        expect.objectContaining({
          errorType: "PERSISTENCE_ERROR",
        })
      );

      const llmErrorCalls = consoleSpy.mock.calls.filter((call) => {
        const ctx: unknown = call[1];
        return (
          typeof ctx === "object" &&
          ctx !== null &&
          "errorType" in ctx &&
          (ctx as { errorType: string }).errorType === "LLM_ERROR"
        );
      });
      expect(llmErrorCalls).toHaveLength(0);
    });

    it("should use different user-facing messages for LLM vs save errors", async () => {
      vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);

      // LLM error path (streaming fails + fallback fails)
      mockSendChatMessage.mockRejectedValueOnce(new Error("Timeout"));
      const { result: result1 } = renderHook(() => useChat());

      await act(async () => {
        await result1.current.sendMessage("Test");
      });

      const llmError = result1.current.error;

      // Save error path (streaming succeeds, save fails)
      makeStreamSucceed(["OK"]);
      mockCreateConversation.mockRejectedValueOnce(new Error("DB down"));
      const { result: result2 } = renderHook(() => useChat());

      await act(async () => {
        await result2.current.sendMessage("Test");
      });

      const saveError = result2.current.error;

      expect(llmError).toBe("Unable to send message. Please try again.");
      expect(saveError).toContain("Message sent but failed to save");
      expect(llmError).not.toEqual(saveError);
    });

    it("should handle non-Error throws from LLM API", async () => {
      vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      mockSendChatMessage.mockRejectedValueOnce("string error");

      const onError = vi.fn();
      const { result } = renderHook(() => useChat({ onError }));

      await act(async () => {
        await result.current.sendMessage("Hello");
      });

      expect(result.current.error).toBe("Unable to send message. Please try again.");
      expect(onError).toHaveBeenCalledWith(expect.any(Error));
      expect(result.current.messages[2]?.content).toBe("Something went wrong. Please try again.");
    });

    it("should handle non-Error throws from persistence layer", async () => {
      vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);
      makeStreamSucceed(["OK"]);
      mockCreateConversation.mockRejectedValueOnce("DB string error");

      const onError = vi.fn();
      const { result } = renderHook(() => useChat({ onError }));

      await act(async () => {
        await result.current.sendMessage("Hello");
      });

      expect(result.current.messages[2]?.content).toBe("OK");
      expect(result.current.error).toBe("Message sent but failed to save. Please try again.");
      expect(onError).toHaveBeenCalledWith(expect.any(Error));
    });

    it("should handle updateConversation failure for existing conversations", async () => {
      vi.spyOn(console, "error").mockImplementation(() => undefined);
      vi.spyOn(console, "warn").mockImplementation(() => undefined);

      // First message via fallback
      mockSendChatMessage.mockResolvedValueOnce(createMockChatResponse("First response"));
      mockCreateConversation.mockResolvedValueOnce(createMockIdea("conv-1", "Test", ""));

      const { result } = renderHook(() => useChat());

      await act(async () => {
        await result.current.sendMessage("First");
      });

      expect(result.current.conversationId).toBe("conv-1");

      // Second message via fallback, updateConversation fails
      makeStreamFail();
      mockSendChatMessage.mockResolvedValueOnce(createMockChatResponse("Second response"));
      mockUpdateConversation.mockRejectedValueOnce(new Error("Connection reset"));

      await act(async () => {
        await result.current.sendMessage("Second");
      });

      const assistantMessages = result.current.messages.filter(
        (m) => m.role === "assistant" && m.id !== "welcome"
      );
      expect(assistantMessages[assistantMessages.length - 1]?.content).toBe("Second response");
      expect(result.current.error).toBe("Message sent but failed to save. Please try again.");
    });
  });
});