Using GitHub Spark to Reverse Engineer GitHub Spark

7 simonw 3 7/24/2025, 3:34:54 PM simonwillison.net ↗

Comments (3)

simonw · 1d ago
The system prompt for Spark is a masterpiece. Well worth reading if you have any interest in prompt engineering or a react development or even just web design in general: https://github.com/simonw/system-exploration-g/blob/main/src...
florians · 4h ago
Especially the design principles are a collection of best practices. Part of it feels like reading Apple’s HIG or Material Design Guidelines. Part of it Refactoring UI. It’s what you learn (or wish you would learn) in design school. Or from a good mentor. Or acquire through years of experience and reading.

Curious: How certain are you that this is indeed the original system prompt, without further hallucination?

simonw · 2h ago
I'm pretty confident in it: I saw the same result from a few different attempts, it's consistent with how the app itself appears to work, and the GitHub Next Twitter account tweeted my article without noting any inaccuracies.

Generally my past experience has been that leaked system prompts aren't hallucinated. Models are very good at repeating text that's just been fed into them.