Files
hq/03-DESIGN/01-to-be/README.md
T
jschoubben bc271d4de0 A worked guide: one module, four capabilities, four languages
What the SDK contains, answered by exclusion as much as by inclusion. It is the
protocol and nothing else — no configuration loader, because configuration
arrives as files the mesh wrote; no API clients, because a Plex client changes
when Plex changes and that has nothing to do with any other module; no storage,
HTTP or logging, because the language has those. The test for anything proposed
is ADR 0039's: does editing it recompile unrelated modules, and does it change
often. Both, and it stays out.

Then the worked module: events in TypeScript, tools in Go, a provisioner in Rust,
a scheduled job in Python. Four artifacts, four toolchains, four processes, one
module — and each part is an ordinary project in its language depending on the
mesh SDK the ordinary way, so a laptop resolves what a build resolves.

And publishing a package as a module capability, which makes the SDK unspecial:
it is simply the first module that published a library. A Plex client belongs to
the Plex module because that is the only thing that knows when Plex changed.

Three things left open rather than papered over: which registry (the catalogue
holds verdaccio and a forge usually serves one too, and nothing says which is
ours), who may publish (a credential that does not exist), and what a range means
in a mesh where everything else is pinned by digest — a mesh that can rebuild a
commit and get a different library is a real change, and should be decided rather
than arrived at.

Claude-Session: https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx
2026-09-15 14:12:01 +02:00

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6.5 KiB
Markdown

# 03-DESIGN / 01-to-be
The mesh being built toward. Every statement here traces to a record in
[`02-DECISIONS/`](../../02-DECISIONS/); nothing arrives by drafting.
A document here describes an intention. What currently runs is in
[`00-as-is/`](../00-as-is/), and the two are never merged — when something ships, the as-is
document is written and this one's status becomes `implemented`.
| Document | Covers | Rests on |
|---|---|---|
| [`00-work-breakdown.md`](00-work-breakdown.md) | How modules move across one at a time, until the old registry can be switched off | [ADR 0001](../../02-DECISIONS/0001-mesh-brokers-nodes-host-agents-think.md), [ADR 0016](../../02-DECISIONS/0016-the-lab.md) |
| [`01-end-to-end-testing.md`](01-end-to-end-testing.md) | The lab: a real mesh a change can be run against before it reaches nodes | [ADR 0016](../../02-DECISIONS/0016-the-lab.md), [0029](../../02-DECISIONS/0016-the-lab.md) |
| [`02-scenario-declaration.md`](02-scenario-declaration.md) | What a scenario declares — the underlay, and what to place on it | [ADR 0016](../../02-DECISIONS/0016-the-lab.md) |
| [`03-scenario-lifecycle.md`](03-scenario-lifecycle.md) | What happens to a scenario — raise, snapshot, restore, move, destroy | [ADR 0016](../../02-DECISIONS/0016-the-lab.md) |
| [`04-lab-installation.md`](04-lab-installation.md) | Getting the lab onto a clean machine, and why it verifies capability rather than installation | [ADR 0010](../../02-DECISIONS/0010-delivery.md) |
| [`05-the-node-host.md`](05-the-node-host.md) | Tier 0 — the one thing installed by hand, and the only thing that changes a machine | [ADR 0005](../../02-DECISIONS/0005-the-node-host.md) |
| [`06-the-control-plane.md`](06-the-control-plane.md) | Tier 2 — what the term means, and the test for what belongs in it | [ADR 0005](../../02-DECISIONS/0005-the-node-host.md) |
| [`07-the-substrate.md`](07-the-substrate.md) | Tier 1 — what the control plane consumes and cannot grant itself | [ADR 0004](../../02-DECISIONS/0004-a-node-and-how-it-joins.md), [0048](../../02-DECISIONS/0006-the-substrate-and-the-control-plane.md) |
| [`08-connectivity.md`](08-connectivity.md) | One context in full — overlay, resolution, exposure, filtering, certificates | [ADR 0007](../../02-DECISIONS/0007-connectivity.md), [0050](../../02-DECISIONS/0007-connectivity.md), [0051](../../02-DECISIONS/0004-a-node-and-how-it-joins.md), [0055](../../02-DECISIONS/0006-the-substrate-and-the-control-plane.md) |
| [`09-the-node-lifecycle.md`](09-the-node-lifecycle.md) | How a machine becomes a node, stays one, and stops being one | [ADR 0004](../../02-DECISIONS/0004-a-node-and-how-it-joins.md), [0051](../../02-DECISIONS/0004-a-node-and-how-it-joins.md) |
| [`10-delivery.md`](10-delivery.md) | Modules, the three edges, and how a change becomes a running thing | [ADR 0010](../../02-DECISIONS/0010-delivery.md), [0064](../../02-DECISIONS/0009-modules-and-the-graph.md), [0065](../../02-DECISIONS/0009-modules-and-the-graph.md) |
| [`11-a-board.md`](11-a-board.md) | What a person sees of the mesh, and why it is read from what runs | [ADR 0008](../../02-DECISIONS/0008-a-context-owns-its-store.md), [ADR 0001](../../02-DECISIONS/0001-mesh-brokers-nodes-host-agents-think.md) |
| [`12-a-module-repository.md`](12-a-module-repository.md) | A module repository, and what builds it | [ADR 0009](../../02-DECISIONS/0009-modules-and-the-graph.md), [ADR 0010](../../02-DECISIONS/0010-delivery.md), [ADR 0005](../../02-DECISIONS/0005-the-node-host.md) |
| [`13-credentials-and-their-rotation.md`](13-credentials-and-their-rotation.md) | Credentials, and moving them without a consumer holding one the provider does not know about | [ADR 0001](../../02-DECISIONS/0001-mesh-brokers-nodes-host-agents-think.md), [ADR 0009](../../02-DECISIONS/0009-modules-and-the-graph.md) |
| [`14-model-access.md`](14-model-access.md) | Model access as a provision, and what a licence is bound to | [ADR 0024](../../02-DECISIONS/0024-model-access-is-a-provision.md), [ADR 0009](../../02-DECISIONS/0009-modules-and-the-graph.md) |
| [`15-the-agent-session.md`](15-the-agent-session.md) | One mechanism started twice — a node's session and the mesh's | [ADR 0004](../../02-DECISIONS/0004-a-node-and-how-it-joins.md), [ADR 0026](../../02-DECISIONS/0026-the-mesh-has-a-session-of-its-own.md) |
| [`16-module-coverage.md`](16-module-coverage.md) | What a module must be able to say, measured against 127 that exist | [ADR 0009](../../02-DECISIONS/0009-modules-and-the-graph.md), [ADR 0005](../../02-DECISIONS/0005-the-node-host.md) |
| [`17-raising-a-mesh.md`](17-raising-a-mesh.md) | How a mesh comes into existence, and how a machine joins one that exists | [ADR 0067](../../02-DECISIONS/0067-genesis-is-a-pivot.md), [ADR 0006](../../02-DECISIONS/0006-the-substrate-and-the-control-plane.md), [ADR 0005](../../02-DECISIONS/0005-the-node-host.md) |
| [`18-building-a-module.md`](18-building-a-module.md) | How a build is modelled, and why a recipe that is always a Dockerfile does not fit what a module is | [ADR 0040](../../02-DECISIONS/0040-what-a-module-is.md), [ADR 0039](../../02-DECISIONS/0039-what-the-sdk-holds-and-refuses.md), [ADR 0009](../../02-DECISIONS/0009-modules-and-the-graph.md) |
| [`19-the-module-protocol.md`](19-the-module-protocol.md) | What a module's code and the mesh say to each other; an SDK is an implementation of it | [ADR 0074](../../02-DECISIONS/0074-the-wire-is-specified-not-the-types.md), [ADR 0042](../../02-DECISIONS/0042-the-shape-of-an-event-on-the-wire.md), [ADR 0043](../../02-DECISIONS/0043-a-module-broker-account-is-scoped-by-emits-and-consumes.md) |
| [`20-writing-a-module.md`](20-writing-a-module.md) | A worked guide: one module, four capabilities, four languages, and the packages it publishes | [ADR 0074](../../02-DECISIONS/0074-the-wire-is-specified-not-the-types.md), [ADR 0040](../../02-DECISIONS/0040-what-a-module-is.md), [ADR 0039](../../02-DECISIONS/0039-what-the-sdk-holds-and-refuses.md) |
## Not yet written
- **The remaining six contexts.**
[ADR 0006](../../02-DECISIONS/0006-the-substrate-and-the-control-plane.md)
settles the list at seven; `connectivity` is the first written in full
([`08`](08-connectivity.md)) and the other six do not exist yet. The work breakdown says in
what order they are needed.
- ~~**Domain grouping outside the core.**~~ **Not needed.**
[ADR 0009](../../02-DECISIONS/0009-modules-and-the-graph.md) is
superseded by [ADR 0009](../../02-DECISIONS/0009-modules-and-the-graph.md):
there is no domain module to group into, so there is no domain list to settle. Relationships
are edges, and grouping is a tag and a query.