From the API Down
You have shipped an agentic tutor to 50,000 people a day without ever training a model. This works downward from the API call you already make, to the tensor, and back up to the lab. Eighty-one lessons.
How to read it
Parts 0 to 3 descend: your API call becomes a string, then tokens, then tensors, then a training run, then the corpus that made it possible. Parts 4 to 11 climb back up: the history, post-training, inference, context, agents, evaluation. By 11.5 you are back at the request in lesson 0.1 and can explain every box in it.
Read in order if you can. If you cannot, use the payoff marks. Every lesson carries one:
| Mark | Means |
|---|---|
| Changes what you do at work this week. | |
| Changes a decision you will make this month. | |
| Background. It is what makes the three-mark lessons land. |
Tick Only what pays rent soonest above and the contents collapse to the three-mark lessons plus everything they genuinely require, in order. That is 49 lessons instead of 81. It is not a shortcut past the hard parts: attention and hardware literacy stay in, because Part 6 does not land without them. Any lesson you open out of order tells you at the top which of its prerequisites you have not read, and how many hours they are.
Six threads run through all of it
The KV cache, cost, data, evaluation, it is just text, and scaling. Each one recurs in a dozen lessons across different parts, which is what makes 81 lessons a book rather than a list. The threads page collects each one in reading order.
Every lesson ends with something to ship
Not an exercise, and never a training run on a laptop with no CUDA. Each lesson closes with one small thing to do in your own stack, in under an hour, that only makes sense once you have read it: count the tokens in your serialized tool definitions, reorder a prompt for cache hits, calibrate your judge against fifty human labels. Each part closes with one larger shipment. Those are listed under each part above.
A second Claude session can teach alongside it
Open a terminal in this folder and run claude. It reads
CLAUDE.md, which tells it the syllabus, how the material is calibrated, and
how to teach it. Then:
/doubt 1.3 | Ask about a specific lesson. It reads that lesson first, plus your notes on it, and answers at the level the lesson is pitched at. |
/quiz 1.3 | Be questioned on it. Synthesis questions, not recall, and it tells you where you were vague. |
/where | What you have read, what is next, and what to ship. |
write lessons 1.4-1.6 | Generate the next batch when you have finished the current one. |
Every lesson page has a copy button for the right command at the bottom.
Keys
j k | Next and previous lesson |
/ | Search |
m | Mark the lesson read |
Progress, notes and section ticks are stored in this browser only. Export both from the bottom of this page before you clear site data or move machines.