Let's create this Excel-like UI with a chatbot sidebar using React. I'll provide the code for the main components:

This implementation creates an Excel-like tabular UI with the ability to add new columns and rows, along with a simple chatbot interface on the left side. Here's a breakdown of the components:

1. ExcelWithChat.tsx: This is the main component that combines the Excel-like table and the chatbot. It uses a flex layout to position the chatbot on the left and the table on the right.
2. ExcelTable.tsx: This component implements the Excel-like table functionality. It uses a 2D array of cells to represent the table data. Each cell has an id and a value. The component provides buttons to add new rows and columns, and allows editing of cell values.
3. Chatbot.tsx: This is a basic chatbot interface that displays messages and allows the user to send new messages. It doesn't implement any actual AI functionality, but it does simulate responses.

To use this in your Next.js application, you would typically place the ExcelWithChat component in a page file, like so:

This implementation provides a foundation that you can build upon. Some potential improvements could include:

1. Persistence of table data (e.g., saving to localStorage or a backend)
2. More advanced Excel-like features (formulas, cell formatting, etc.)
3. Integration with a real chatbot or AI service for the sidebar
4. Improved styling and responsiveness

Let me know if you want to expand on any part of this implementation or if you have any questions!

I'll modify the Excel-like UI to include headers, and reposition the "Add Row" and "Add Column" buttons as you've requested. Let's update the ExcelTable component to incorporate these changes.

These changes implement the following improvements:

1. Headers: The table now has editable headers. By default, they start with 'A', 'B', 'C', but users can click on them to edit.
2. Add Column button: This is now positioned at the right end of the header row, represented by a '+' icon.
3. Add Row button: This is now a full-width button at the bottom of the table, labeled "Add Row" with a '+' icon.
4. Styling: The table now uses full width and has improved spacing and borders.
5. Accessibility: Added aria-labels to inputs for better screen reader support.
6. Responsiveness: The table is now wrapped in an overflow container to handle many columns gracefully.

To use this updated version, you would still place the ExcelWithChat component in your page file as before:

This implementation provides a more Excel-like experience with editable headers and conveniently positioned add buttons. Users can now easily add rows and columns, edit cell contents, and modify column headers.

Some potential further improvements could include:

1. Implementing cell selection and multi-cell operations
2. Adding basic formula support
3. Implementing data persistence (local storage or backend integration)
4. Adding more Excel-like features such as cell formatting, sorting, or filtering

Let me know if you want to expand on any of these features or if you have any questions about the implementation!