System prompts are composed at agent construction (src/agent/teacher-agent.ts), one composition per agent — the probe/teach split (docs/probe-teach-split.md):
1.`src/agent/system-prompt.md` — the SHARED base: the teaching philosophy (both principles), accuracy, quiz-option construction, the question tools, formatting. Owned by the master seam; do not edit from a worker.
2. Every numeric-prefix `*.md` fragment in the agent's directory (`prober/` or `teacher/`), in **sorted filename order**, joined with `---` separators. The loader enforces the numeric prefix (`\d*-*.md`) — other files (like this README) never enter the model's prompt.