Two major misconceptions about ChatGPT: 1. The model in ChatGPT is not the same as the one with the same name provided to developers via API, and the differences are significant. For example, even though both are called GPT-5, the version in ChatGPT includes many hidden System Prompt instructions, and its context window is less than 200K tokens (the smallest version is only 16K). However, the GPT-5 API has a 400K context window and allows full customization of the System Prompt. 2. While a larger context window is generally better, as historical information accumulates, it can impact the reasoning and performance of subsequent responses. So, it's best to start a new conversation each time instead of piling up chat history.