Primers

The useful 20% of anything — the smallest reading that lets you actually do the thing, or actually reference it correctly. One confusion cleared per page, everything else deliberately left out.

17 primers

Non-alcoholic beer, the useful 20%

Two families, opposite faults: alcohol taken out tastes thin, alcohol never made tastes sweet. How each is made, and how to pick a better can.

Deterministic edits with Claude, the useful 20%

Outcome-based pricing, the useful 20%

Agent payments, the useful 20%

"An agent that hunts for the best deal will hunt for the cheapest way to pay, so agents will route around cards." Mostly, no. The buyer never sees the card fee; the…

AI agents, the useful 20%

The model is not the agent. The model is one stateless function call: text in, text out, with the option to ask for a tool. The agent is the loop around it — the code…

APIs & MCP — What's the Same, What Isn't

an API is a contract written for a programmer ; MCP is a contract written for a model . MCP does not replace APIs — it is a standard wrapper that sits on top of them,…

Claude Code Sessions Primer — One Session, One Thread of Work

"Could I name this session for the one thing it's doing?" If the honest name is a project folder — ! Main , General Coding — it's a holding tank. If it's a sentence —…

Front-End Primer — Modern Stacks for Vibecoding

"Is this a single-file job or a components job?" — everything above is downstream of that split. Single file = speed and portability; components (.tsx) = reuse, types,…

GPT-6 Astra Primer — What Actually Changed

the headline numbers are model gains, but the numbers that change what you can build are harness gains. Astra's biggest practical delta is that the scaffolding around…

Langfuse — the useful 20%

Langfuse does not see what Claude sees. The Claude Code hook ships each turn's prompt, reply, tool calls and token counts, but not CLAUDE.md , skills or auto-loaded…

LangGraph, the useful 20%

LangGraph is not an AI library. It is a small state-machine library: nodes are plain functions, edges say which function runs next, and a shared state object gets passed…

Printing Bench Map

One folder, three ways in: the phone, Cowork, and Claude Code. The folder lives on the Mac and syncs through iCloud. Each level of the folder carries its own CLAUDE.md ,…

Ready Player One, the useful 20%

The movie is not a condensed version of the book — it's a different puzzle wearing the same setup. Spielberg's 2018 film keeps Halliday's hidden Easter egg and its three…

Snow Crash, the useful 20%

The word “metaverse” did not start at a tech company. Neal Stephenson coined it — and, separately, landed on “avatar” in its modern sense — in this 1992 novel, to…

Star Trek's first episode, the useful 20%

There isn't one answer, and that's the whole trap. Three different episodes can honestly claim “first”: The Cage was filmed first and rejected as too cerebral for 1964…

The Roadless Rule — Background & Factful Read

the Forest Service cannot maintain the roads it already has. The 2001 rule was, at its origin, a decision to stop extending a network the agency was already failing to…

Walden, the useful 20%

He wasn't a hermit. Walden Pond sat about a mile and a half from downtown Concord — Thoreau walked into town every day or two, friends walked out to see him, and (this…