What happened
The launch post described ChatGPT as a sibling of InstructGPT, trained with RLHF, offered free to collect feedback. It was not framed as a scientific discovery. It was a product: a browser chat that non-specialists could use immediately for code, prose, and analysis. Independent accounts (The Verge, MIT Technology Review) document the unexpectedly fast workplace adoption. This ledger entry scores the deployment of that professional tool, not monthly active users. Harm from fabricated citations and related misuse is recorded on separate events. Later models replaced GPT-3.5 inside the product; credit for the launch stays with the ChatGPT/GPT-3.5 system that shipped on 30 November 2022.