Thank you for providing the screenshot and Applet ID.
This error occurs when a project’s accumulated chat and iteration history grows beyond the maximum input token capacity allowed for a single request. Because the Build Agent includes prior conversation turns and tool actions to maintain continuity, submitting a new prompt—even a single line—evaluates the entire history and exceeds the input limit.
You can try clearing the conversation overhead directly in your original project while keeping all your work intact:
Open your original Aeroplane Ludo Game Engine project in Google AI Studio.
In the chat panel on the left, click “Start new chat”.
Looking at your screenshot, it looks like you are pasting a large CLI transcript (Paste September 18...) combined with large files in your project’s File Explorer (bun.lock, assets/, and src/data/), this might be causing the issue.