Architecture

blendtutor is a Cargo workspace of two crates:

• blendtutor-core — the reusable library: the lesson model, language runners (R and Python), grading, and LLM providers, built up slice by slice. It holds all domain logic and is free of anyhow; error reporting lives at the CLI edge.
• blendtutor-cli — a thin command-line shell (binary blendtutor) that parses arguments and delegates to core.

The dependency only ever points cli → core; core never imports cli (ADR-0001). That boundary is what lets a future GUI reuse core directly.

How the docs mirror the code

This book is structured to track the core module boundaries: as top-level modules land (lesson model, runners, grading, providers), each gets a narrative chapter here, while the generated API reference documents the corresponding public surface. Prose explains why a module exists and how it fits; rustdoc documents what each item is. Keeping them in their native tools — and merging the rustdoc output under /api at deploy time — avoids duplicating the API surface by hand.