Essay 7.1 — The Plugin Kit, Part 1 of 9. Essay 7 opens here; Parts 2 through 9 follow.

Multiple plugin "cells" arranged as a cellular composition, evoking the plugin kit as a community of cells working together. This is the og:image source for the B7 series (Essays 7.2-7.9 use this as their social card; opener 7.1 uses its own anatomy image below). Lives on disk at blog/b7/images/plugin-kit-b7-banner.png
Banner 7. The plugin kit — cells composing the brain. Each owns one concern. Each protects itself.

A plugin is a cell.

Essay 5 opened the always-on layer — the plugins that run continuously, each minding one concern, side-by-side with the CLAUDE.md hierarchy. Essay 6 opened the phasic layer — the cycle of phases whose moves are themselves Markov chains. Both layers are built from the same kind of object: a plugin, sitting in its own directory under .claude/plugins/, carrying its own organs. This essay opens that object. ⓘ

The cell metaphor is load-bearing. A plugin is not a collection of loose files; it is a system of cognitive organs that read each other, write to each other, and depend on each other through declared channels. Each organ inside the cell carries the same read / write / depend-on triple: ⓘ

  • Who reads it — which subsystem (the LLM, Claude Code itself, another plugin, the human operator) consumes the contents at runtime.
  • Who writes it — which ceremony or phase is allowed to mutate it. Most organs have exactly one writer; the security model rests on that exclusivity.
  • What it depends on — which other organs must already be in place for this organ to function correctly.

The read / write / depend-on triple is how the cell wall stays porous (organs talk through declared channels) and rigid (organs never reach through undeclared ones). Essay 7 opens the cell organ by organ, naming who reads it / writes it / what it depends on at each step, then closes with a Tier-3 walkthrough of authoring a new plugin from scratch. ⓘ

A single plugin "cell" with its internal cognitive organs visible inside the cell wall, the PLUGIN-LOCK ceremony drawn as a membrane gate on the wall, and the three property labels (reads / writes / depends on) listed beside the cell as the universal anatomy frame
Image 7.1. A plugin is a cell. Cognitive organs live inside the wall; the PLUGIN-LOCK membrane gates every edit; three properties name each organ.

The journey ahead

Essay 7 covers the plugin kit across the sub-essays listed below:

Essays 7.2 through 7.7 deep-dive the universal organs, one cluster per essay — the parts every plugin carries. Essay 7.8 opens the ceremony that protects edits to those organs once the plugin is in flight. Essay 7.9 is for the architects in the audience — a walkthrough of putting the kit to use, authoring a new plugin end to end.

We start with the universal skeleton — CLAUDE.md, hooks, and scripts — the load-bearing organs Essay 7.2 deep-dives. ⓘ

A consulting practice could organize its own seed agent’s plugin around a [CLIENT-INTAKE] ceremony built from the same cell skeleton; the organ list (hooks, scripts, hidden state) transfers wholesale. Nothing in the kit is mathematically enforced; the protections are friction (PLUGIN-LOCK gating each edit, test-pass-or-revert undoing failed runs, dual voices coaching the operator and the LLM separately) plus operator discipline. ⓘ

Essay 7.1 — The Plugin Kit, Part 1 of 9.

Previous: Essay 6.10 — The Plan-State Machine — Long-Horizon Memory — closes the markov phasic brain series. Next: Essay 7.2 — Skeleton: CLAUDE.md, Hooks, and Scripts — the universal organs governed by PLUGIN-LOCK.