1 min lesson
Context, indexing and retrieval
Rebuild the parts of "Context, indexing and retrieval", then say why each one matters.
Step 1 of 3
The model only knows what made it into the context window - and the context window is small, expensive and curated by the harness, not by your whole repo.
This one mechanism explains the single most common developer complaint about coding agents: why didn't it use my other file? Teaching it well retires a whole category of support questions, which is direct DX value.