The design layer described every service by role and never once by name:
Postgres appeared in zero design documents. That was over-application of the
research rule "never identify the mesh it observed", which is about node names
and domains, not software.
Two things were actually broken by it. substrate.lock pins images by digest and
a digest belongs to a named image, so the bundle could not be written from the
design. And a reader could not tell a settled choice from an unexamined one --
"a relational store" reads identically either way.
ADR 0048 names them: PostgreSQL, LavinMQ, MinIO, an OCI registry, Docker. The
argument for each is continuity, which is a real argument -- replacing a
substrate service migrates the mesh's own state. Role and product are now both
written, because the design depends on the protocol while the installer needs
the product.
Also separates two questions the substrate doc had merged: being substrate and
being in the bundle. Only Postgres must precede the control plane; the rest are
substrate by role and ordinary by delivery. Whether the bus joins it is left
open, because it turns on the control plane's internal shape.
Names the forge as Gitea, and records ingress/Traefik as an unclosed gap rather
than a naming one -- nothing says what terminates TLS or which tier owns it.
Fixes a miscount: the host's bootstrap vocabulary is six shapes, not five.
Nineteen files, seventy-nine mentions, no definition. That is how-we-build §5
failing on this repository's own vocabulary — ubiquitous language is checked,
not assumed.
The definition, and it is not arbitrary: the control plane is everything that
needs to know about MORE THAN ONE NODE. It follows from ADR 0037, which has the
host applying rather than deciding precisely because deciding needs knowledge
the machine does not have. So the line falls exactly there — writing a file is
the host's, choosing which nodes run the store is the control plane's, and
anything a single machine could answer alone does not belong here at all.
That last consequence is worth having: putting a single-machine concern in tier
2 is a mistake the tier rule will NOT catch, because the dependency direction
stays correct.
Also states what it is not — not the thing that changes machines, not a surface,
not the substrate, and not privileged on a node beyond what the declaration
vocabulary allows. And the property that makes tier 2 unlike the others: it is
itself a consumer, with the same requirements as any module, which is the
circularity the bundle exists to resolve rather than hide.
Scoped deliberately: this defines the term and does not design the contexts
inside it. Ten is the skeleton's claim rather than a settled list, and research
006 still asks whether the record belongs here or in the substrate.
jschoubben