ADR 0074 — the wire is specified; an SDK is what passes the suite

ADR 0039 settles what belongs in an SDK. It does not say what happens when there
is more than one, and there already is: the contracts are expressed as Go types
in the control plane and host and as TypeScript types in the SDK, and nobody has
felt it because both live in one repository.

They already disagree. The provision's field is "resource" in one and "Provision"
in the other; "consumer" means the module in one and the node in the other; the
envelope declares six headers on one side and emits four on both — the missing
two being x-causation-id and x-schema, the second of which is exactly what a body
needs in order to change shape without silent misreads.

That class of failure does not announce itself. Two implementations disagreeing
about an envelope do not fail to compile — they ignore each other's messages, and
a mesh where a module stops reacting looks like a mesh where nothing happened.

So the decision is to specify the wire rather than share the types, because the
shapes are the easy half. What two implementations actually disagree about is
behaviour: queue naming and durability, which headers are required and what an
unknown one means, taking identity from the sealed credential rather than the
environment, dedup on an id only the emitter can make, pinning a fingerprint
rather than trusting an authority.

And the suite is executable rather than prose, because a specification nobody can
run is a document two implementations drift from while both believe they conform.
The two existing implementations are the first made to pass it — a suite only new
SDKs must satisfy would certify every future language against a disagreement that
is already here.

Claude-Session: https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx

02-DECISIONS/README.md

@@ -106,6 +106,7 @@ python3 00-META/checks/index.py            fail if stale
 - **0071** — [Genesis clones from a mesh, and checks what it got](0071-where-genesis-gets-its-source.md)
 - **0072** — [Two graphs, and a build chain that orders itself](0072-two-graphs-and-the-build-chain.md)
 - **0073** — [The installer carries a builder, and the registry stays where it is](0073-the-installer-carries-a-builder.md)
+- **0074** — [The wire is specified; an SDK is whatever passes the conformance suite](0074-the-wire-is-specified-not-the-types.md)  *(proposed)*
 
 ### What runs on them, and how it gets there