System prompt
The basic, hidden instructions that tell an agent who it is and how to behave, before any message from you.
Where you learn it
In module 06 · Subagents: separate helpers, in the Claude Code for Beginners course.
Related terms
Learn Claude Code from zero, in plain English
12 modules with 1–2 minute lessons, which you can also do on your phone. The first two modules are free.