Repeating a Prompt Rule Helps — But Only Up to Four Times
Say It Four Times (In Your System Prompt)
A developer tests the common advice to repeat important instructions in system prompts. Using Gemini 2.5 Flash, they measure how often the model obeys a rule about quote style across 1,080 runs. Results: one mention gives 74% compliance, four mentions 97%, and further repetitions add nothing. The post also reveals that many prompt tweaks are coin flips, and that the model may ignore constraints it files under a different category, like docstrings.
If you've ever tweaked a prompt, run it twice, and concluded the tweak worked, this is the number that should bother you. It bothers me.
- zknill
I'm really put of reading ai-isms like "It quits working around the fourth time, and the average hides who it worked for"
This is classic Claude, and makes me think the author didn't read, edit, or invest in their own words.
- leecommamichael
> and the average hides who it worked for.
**** off. Can't even get through the ****ing subtitle any longer these days.
- joaquincabezas
Beetlejuice Beetlejuice Beetlejuice… Beetlejuice