Can I code ChatGPT Plus?

COPYBuild a personal chat UI, not a language model — that's a real, achievable weekend project, not a lesser version of the real product: 1. A text input and a message list, with responses streamed token-by-token from an existing LLM API (most APIs support streaming natively — use it, don't wait for the full response before showing anything). 2. Conversation history stored per user in your own database — ordinary CRUD, list past conversations, resume one, start a new one. 3. System-prompt customization if you want a specific persona or behavior — a text field you control, sent alongside every message in that conversation. Use an established, capable model via its API for the actual generation — that's not cutting a corner, it's the same approach this register recommends throughout for every other AI-wrapper idea. Out of scope, and a different order of magnitude entirely: training or fine-tuning a foundation model competitive with existing frontier models, which needs data, compute, and research investment individuals and most companies simply don't have.