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system prompt
The standing instructions above the chat: who the model is, what it may touch, how it should fail.
What is system prompt?
A system prompt is the persistent brief. User turns are episodes. The system prompt is the show bible: repo conventions, forbidden moves, the test command, the definition of done.
Why does system prompt matter when vibe coding?
Without one, every turn renegotiates the job. With a sloppy one, the model role-plays “senior engineer” and still rewrites half the tree. Put mechanical limits in tools; put taste and procedure in the system prompt.
How do you do system prompt?
Keep a SYSTEM.md in the repo. Point the agent at it. Update it when a turn goes wrong, the same way you would fix a test.
How do you ask a model for system prompt?
Follow SYSTEM.md. It outranks this turn. If this turn conflicts with it, stop and say so.
What goes wrong with system prompt?
A novel in the system prompt. Models lose the middle. Short, testable rules beat a manifesto.