Building tier 0 forced the question "the one binary installed by hand" had been
carrying unexamined. A TypeScript host needs a runtime present before it runs,
so the thing installed by hand becomes two — and the second must be installed by
the means the host exists to replace.
So the host is a statically linked binary that requires nothing present, written
in Go. Rejected: a runtime installed first, which breaks the property the tier
rests on; and bundling the runtime into the executable, which carries ninety
megabytes to preserve a language choice and puts a young feature at the bottom
of the stack.
The argument that decided it is architectural rather than about taste. 0037
means the host never queries the mesh database and 0039 means it only receives
declarations, so the host shares NO code with any other tier — not a client, not
a schema, not the SDK. The language boundary falls exactly on a boundary that
already exists, and a second language usually costs duplicated logic where here
there is none to duplicate.
§8 gains a scope: it said "TypeScript throughout" when everything was a service
or a surface, and is now scoped to those with tier 0 named. Another sync owed.
Playbook 04 steps 2 and 4: repos.md records mesh-host as existing, the design
takes code: [mesh-host] and status: in-progress.
Playbook 02 step 3, on four recorded decisions. Tier 0 has one job — apply
declared state on this machine — and the six absorbed concerns are instances of
it, not additions to it.
Specifies the six parts and what each owns, and the two properties that make
apply trustworthy rather than merely present: every applier reads back, because
setting a value is not evidence the value took; and what was applied is recorded
after it works, never before, because a failed apply leaves the machine wherever
it reached and nothing must claim otherwise.
Build order is staged so each stage is verifiable in the lab before the next
exists. Stage 1 is profile and inventory — no control plane, no declarations, no
network — and it is deliberately the smallest useful thing, because `place:` has
nothing to place and the lab therefore raises empty machines. Stage 1 ends that,
and every later stage is tested by a lab that already works.
Stage 2 is the one that could invalidate the tier boundary: whether one host can
raise the substrate alone is Move 1's assumption and has never been proved.
Every decision the design rests on is given the test that asserts it, per 0034 —
including the dependency-direction lint, which is what makes "the host never
queries the mesh database" a rule rather than an intention.
Six things left open and named, including the one that host-size.md could not
measure: zero dependencies, but still six vocabularies.
jschoubben