Files
hq/02-DECISIONS/0077-the-controller-and-the-foundation.md
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jschoubben 1111bd84d7 Establish the repo for the completed Phase 0-3 build
Settles the design repository now that the self-upgrade build is on main:
- Records the two decisions that shipped without a record — ADR 0077 (the
  controller/foundation/node vocabulary) and ADR 0078 (the store and broker are
  ordinary modules); accepts ADR 0075 and 0076, which shipped work rests on.
- Fills issue 051's amended-design and wires ADR 0078 into 07-the-foundation.
- Sweeps the repo rename (mesh-control -> mesh-controller) into the mutable docs
  now that the forge repo is renamed; updates the glossary note and repos.md.
- Fixes the six broken links from the design-doc renames, indexes the glossary,
  regenerates the decisions reading order.

Both checks (records.py, index.py) are green. Statuses stay honest: the build is
on main and lab-proven but not deployed as the production mesh, so the to-be docs
remain in-progress and the as-is layer (the hal mesh) is unchanged — graduation
to implemented + as-is belongs to deployment, not merge.

https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx
2026-09-17 00:04:58 +02:00

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Markdown

---
topic: the mesh
status: accepted
date: 2026-09-16
deciders: jochen
reconstructed: false
extends: 0006-the-substrate-and-the-control-plane.md
---
# 77. The parts are named controller, foundation, node — not control plane, substrate, master
## Context
The words drifted. In conversation and in code the same thing was called *control plane*,
*controller*, *master*, and *hub*; the store-and-broker pair was called *substrate* and
*foundation*; a machine was a *node*, a *worker-node*, a *peer*, a *slave*. A mesh named
differently by two people is a mesh they describe differently, and the drift was worst on the
parts talked about most.
Three of the terms carried wrong ideas. *Control plane* is borrowed from networking's
control-plane/data-plane split and means nothing here. *Master/slave* and *hub/peer* imply a
subordinate — but no node is: a node applies its own declaration and keeps running when the
control-node dies, so it is as much its own machine as any other. *Substrate* is a biology
metaphor that landed for no one.
## Considered Options
1. **Keep the inherited words.** Rejected: they are the source of the drift, and two of them
(control plane, substrate) are metaphors that teach the wrong shape to anyone reading them cold.
2. **master / slave, or hub / peer, for the nodes.** Rejected: both name a hierarchy the mesh does
not have. The control-node owns no other node; lose it and the rest keep running what they were
last told.
3. **controller / foundation / node + control-node.** Chosen.
## Decision
The component that decides what each node should be, holds the mesh's records, and tells nodes is
the **controller** — the module `mesh-controller`, which claims the mesh-scoped `the-controller`
seat. The store and broker raised at genesis are the **foundation**. Machines are **nodes**;
there are 0..n of them, and exactly one — the one running the controller — is the **control-node**.
Retired: *control plane*, *substrate*, *master/slave*, *hub/peer*, *worker-node*.
[`00-META/glossary.md`](../00-META/glossary.md) is the authority, and a new name for an existing
thing lands there in the change that introduces it in code.
## Consequences
`mesh-control` became `mesh-controller` across the module, container, image, binary, `cmd/` dir and
the git repository; `substrate` became `foundation` in the embedded base bundles, the default
template and the example lock; the seat `the-control-plane` became `the-controller`. The 03-DESIGN
prose and 00-META follow the new words.
What got harder: the records under `02-DECISIONS/` are immutable, so they keep the words they were
written with — this record included, whose own title names what it retires. A term retired here
still appears there, and the glossary is how to read it. The git repository on the forge was
renamed `mesh-control` → `mesh-controller`.
## References
- [`00-META/glossary.md`](../00-META/glossary.md) — one name per thing, and the words retired.
- The rename shipped across all six code repositories and hq (main).