The record claimed the two implementations already disagreed. Inspection showed
the live wire agrees: the disagreeing grant types were dead (removed), and the
envelope's two extra headers are optional and set when relevant, not missing.
The danger was dead types contradicting the wire, not live disagreement — which
is a sharper reason for specifying the wire and checking against it, not a weaker
one. The model stands; the conformance suite's job is prevention rather than
repairing a present break.
Claude-Session: https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx
The tool runtime's manifest names the SDK as a git dependency at a pinned commit;
its lock file names a sibling directory that exists on one workstation. It builds
only because the recipe runs npm install, which tolerates a lock disagreeing with
its manifest and re-resolves from the manifest — the one command that hides this.
It matters because a lock exists to make a build reproducible and this one
describes one machine, and because it is the first thing a fresh mesh builds: the
toolchain carries the SDK and everything with code of its own compiles inside it,
so a dependency resolved differently on the build machine than on a workstation
is a difference in every module the mesh will ever build.
And it is about to be copied. Each language's toolchain will carry that
language's SDK the same way, so the shape is worth settling before there are four
of them.
Claude-Session: https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx
Two corrections, both from the operator and both better than what was written.
An SDK is an implementation of the mesh's module protocol in one language, and
nothing more. The first draft defined it by the test it passes, which describes
how you check one rather than what one is — and leaves it sounding like a library
that helpers could accumulate in.
And the protocol is split per capability, which was missing entirely. A module
that only consumes events uses the event capability; one that serves tools uses
the tool capability; a provider uses provisioning. Nothing about consuming an
event requires knowing how a grant is answered, so an SDK need not implement all
of it to be real.
That has a precedent here: a host declares which resource kinds it can apply, and
a partial host is a real thing rather than a broken one (ADR 0005). An SDK
implementing the floor and events is exactly as legitimate, and a module written
against it is a module that does events.
Which changes what adding a language costs. A Rust SDK doing connection and
events is useful the day it exists, with tools and provisioning following when
something needs them — rather than a language being unsupported until it is
entirely supported, which is what makes adding one a project instead of a
contribution.
Conformance is therefore per capability too: a monolithic pass or fail would make
a partial implementation indistinguishable from a broken one, which is the
distinction the whole thing rests on.
Claude-Session: https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx
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
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