fix(web): Remove re-throw from loadConversation to prevent unhandled rejections

- Make loadConversation fully self-contained like sendMessage (handle
  errors internally via state, onError callback, and structured logging)
- Remove duplicate try/catch+log from Chat.tsx imperative handle
- Replace re-throw tests with delegation and no-throw tests
- Add hook-level loadConversation error path tests (getIdea rejection)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/components/chat/Chat.test.tsx

@@ -103,7 +103,7 @@ describe("Chat", () => {
   });
 
   describe("loadConversation via ref", () => {
-    it("should successfully load a conversation", async () => {
+    it("should delegate to useChat.loadConversation", async () => {
       const mockLoadConversation = vi.fn().mockResolvedValue(undefined);
       mockUseChat.mockReturnValue(
         createMockUseChatReturn({ loadConversation: mockLoadConversation })
@@ -117,9 +117,10 @@ describe("Chat", () => {
       expect(mockLoadConversation).toHaveBeenCalledWith("conv-123");
     });
 
-    it("should log error context and re-throw on network failure", async () => {
-      const networkError = new Error("Network request failed");
-      const mockLoadConversation = vi.fn().mockRejectedValue(networkError);
+    it("should not re-throw when useChat.loadConversation handles errors internally", async () => {
+      // useChat.loadConversation handles errors internally (sets error state, logs, calls onError)
+      // and does NOT re-throw, so the imperative handle should resolve cleanly
+      const mockLoadConversation = vi.fn().mockResolvedValue(undefined);
       mockUseChat.mockReturnValue(
         createMockUseChatReturn({ loadConversation: mockLoadConversation })
       );
@@ -127,57 +128,13 @@ describe("Chat", () => {
       const ref = createRef<ChatRef>();
       render(<Chat ref={ref} />);
 
-      await expect(ref.current?.loadConversation("conv-123")).rejects.toThrow(
-        "Network request failed"
-      );
-
-      expect(consoleSpy).toHaveBeenCalledWith(
-        "Failed to load conversation",
-        expect.objectContaining({
-          error: networkError,
-          conversationId: "conv-123",
-        })
-      );
-    });
-
-    it("should log error context and re-throw on API error (500)", async () => {
-      const apiError = new Error("Internal Server Error");
-      const mockLoadConversation = vi.fn().mockRejectedValue(apiError);
-      mockUseChat.mockReturnValue(
-        createMockUseChatReturn({ loadConversation: mockLoadConversation })
-      );
-
-      const ref = createRef<ChatRef>();
-      render(<Chat ref={ref} />);
-
-      await expect(ref.current?.loadConversation("conv-456")).rejects.toThrow(
-        "Internal Server Error"
-      );
-
-      expect(consoleSpy).toHaveBeenCalledWith(
-        "Failed to load conversation",
-        expect.objectContaining({
-          conversationId: "conv-456",
-        })
-      );
-    });
-
-    it("should re-throw error for caller to handle", async () => {
-      const mockLoadConversation = vi.fn().mockRejectedValue(new Error("Auth failed"));
-      mockUseChat.mockReturnValue(
-        createMockUseChatReturn({ loadConversation: mockLoadConversation })
-      );
-
-      const ref = createRef<ChatRef>();
-      render(<Chat ref={ref} />);
-
-      // Verify the error propagates to the caller
-      await expect(ref.current?.loadConversation("conv-789")).rejects.toThrow("Auth failed");
+      // Should resolve without throwing
+      await expect(ref.current?.loadConversation("conv-123")).resolves.toBeUndefined();
     });
   });
 
   describe("sendMessage delegation", () => {
-    it("should delegate to useChat.sendMessage without extra error handling", async () => {
+    it("should delegate to useChat.sendMessage", async () => {
       const mockSendMessage = vi.fn().mockResolvedValue(undefined);
       mockUseChat.mockReturnValue(createMockUseChatReturn({ sendMessage: mockSendMessage }));
 

apps/web/src/components/chat/Chat.tsx

@@ -94,12 +94,7 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
   // Expose methods to parent via ref
   useImperativeHandle(ref, () => ({
     loadConversation: async (cId: string): Promise<void> => {
-      try {
-        await loadConversation(cId);
-      } catch (err) {
-        console.error("Failed to load conversation", { error: err, conversationId: cId });
-        throw err;
-      }
+      await loadConversation(cId);
     },
     startNewConversation: (projectId?: string | null): void => {
       startNewConversation(projectId);

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

@@ -377,6 +377,44 @@ describe("useChat", () => {
       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());
+
+      // Should resolve without throwing - errors are handled internally
+      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", () => {

apps/web/src/hooks/useChat.ts

@@ -290,7 +290,6 @@ export function useChat(options: UseChatOptions = {}): UseChatReturn {
           ideaId,
           timestamp: new Date().toISOString(),
         });
-        throw err;
       } finally {
         setIsLoading(false);
       }