I don’t know what changed, but recently Gemini 2.5 often breaks the format written in the prompt system instruction. In a few responses at the beginning, the format looks good, but then it starts to ignore the format prompt, no matter how I fix the prompt. There’s only a 1/20 chance it will follow the format.
Oh, additionally I don’t like when it comments when I tell it clearly do not comment anything in the response.
Hi @RandomGuy
Could you please share a minimal, reproducible example of your code? Will try to reproduce the issue on my end
Thank you
It’s like I prompt it to write the title before the answer.
**[title]:**
[answer]
After some responses, it answers directly, ignoring the prepended title.
Hi @RandomGuy ,
The model treats the conversation history as a pattern to follow. Sometimes pattern is interrupted and then this happens .
If you are using the Gemini API or AI Studio, you should place the formatting rule in the System Instruction block, not the user prompt. System instructions carry a higher weight and persist throughout the context. or If you are using normal chat interface ,Try reminding the model your rule every few turns like : “Remember to format every response with [title]: before the answer.” or else use Few-Shot Prompting technique .
Please try these methods and let me know if they work as expected.
Thank you.