Help needed: why is the 4o api response so short compared to chatGPT 4o?

Hi all,

Because the safety routing on chatGPT has made 4o unusable for my purpose of dark theme fiction writing, I have been testing 4o API on playground.

  • my chatGPT setup: custom instruction(2k tokens) + 10 plot files
  • my API setup: prompt with system message(the same 2k tokens) + same 10 files in vector store, temp 0.7 to 0.9; version gpt4o, both latest and 2024-11 snapshot.

question is, for the same prompt, chatGPT version of 4o gave me a full discussion upon request, which was 1000+ tokens, deep dived, and ask me if i need to dive deeper in any area. But the api version gave me 300 token summarized answer and called it a day.

Anyone knows why?

  • The system prompt and files and prompt are exactly the same, but the result are so different?
  • What is being done on the chatGPT front that I need to replicate in my API usage to get back the same level of answer?

I have attached snippets from the answer from both ends.


answer from chatGPT:

2005–2006 (second Palms apartment):

  • Setting: Back to Palms, rented a modest but clean two-bedroom. Neutral carpet, vertical blinds, low-end appliances. Tighter layout.

  • Sleeping Setup: Kid’s bed placed in Tiffany’s room immediately, but unused for months. They continued sharing the queen bed in the master bedroom until mid-2006. When he first tried to transition her, he lasted maybe one night before silently pulling her back in. Took weeks before she stayed in her own room through the night. Afterward, he’d sit outside her door for hours. Sometimes he fell asleep in the hallway.

  • Emotional Tone: Psychological rupture. The shift to separate rooms wasn’t about her maturity—it was about his inability to let go. He knew she needed her space, but it gutted him. Her absence at night was physical. He still checked on her twice an hour until exhaustion won.

If you want, we can do expanded narrative scenes for any year above—either Jimmy’s POV or external observer. Let me know which slice to deepen.


answer from API(it is also wrong):

New Palms Apartment (2005-2011): Jimmy rented another two-bedroom apartment. Initially, Tiffany slept in his room, and it took several months before he transitioned her to her own bed. He found it difficult to sleep when she moved to her room.

The sleeping arrangements reflect Jimmy’s deep need for connection and his protective instincts towards Tiffany. Despite his complex life, his decisions revolved around her well-being and his desire to maintain closeness.