jschoubben
ccbbfa9c8a
Closes the two open questions in 06 and 08, which turned out to be one question: how many control planes run, and what happens when the hub is down. Both were drifting toward redundancy by default -- a standby plane, a second hub, an election to pick between them. That is not one feature but a property every layer must then honour, and each layer gets it wrong independently. Not wanted, and not needed. A handful of machines with one node hosting the registry is not a distributed system. The argument for why this is sound rather than merely cheap is that the design already tolerates it by construction. ADR 0036 makes reachability state rather than class; the host reconciles from its own store (0043) and never needed to ask anybody to hold the state it was last given. So the control plane being down is not a new failure mode -- it is every node in the ordinary disconnected situation at once. What is lost is change, not operation. No node holds a contended role: the control plane is assigned like any other module, and the overlay hub is declared (0050). No promotion, no quorum, no fencing, no split brain, no replicated store, and no "which node is authoritative" recurring at every layer. Two consequences stated plainly rather than buried. The control-plane node is a single point of failure -- deliberate, and said out loud so it stays deliberate. And recovery is restore rather than failover, which makes backup the availability story rather than hygiene. The sharpest one is the clock: the control plane owns certificate issuance (0049), so an outage outlasting a renewal window expires every public name. That bounds how long recovery may take, and nothing measures it today.
02-DECISIONS
Architecture decision records — the "why" trail behind the rules in
00-META and the specifications in 03-DESIGN.
Numbered 02 because a decision precedes the design it authorises. Research concludes,
the decision is recorded here, and only then is the design written. Following the folder
numbers walks the process in the order it happens.
One file per decision, numbered, never deleted. A superseded record has its status: changed
and gains a pointer to what replaced it — its text is never edited. The reasoning that was
rejected is the expensive half to rediscover.
The records run in the order the decisions were taken, oldest first.
Every decision is a record. There is no ledger and no index file — if a decision is worth
recording it is worth a record, and if it is not worth a record it is not recorded
(ADR 0026). A "decision" small enough to be one line is
almost always a rule, and a rule belongs in
00-META/how-we-build.md, where it is enforced and keeps the
incident that earned it.
Frontmatter
---
status: proposed | accepted | superseded
date: YYYY-MM-DD # when the decision was taken, not when it was written down
deciders: name
reconstructed: true|false # true when the record was written after the fact from evidence
superseded-by: # 02-DECISIONS/NNNN-....md, when status is superseded
extends: # 02-DECISIONS/NNNN-....md, when this record widens an earlier one
---
Body
# N. Title in plain language
## Context what was true, with evidence
## Considered Options numbered, each with why it was rejected
## Decision what was decided
## Consequences what follows, including what got harder
## References commits, pull requests, knowledge-base entries, prior art
State evidence, not assertion. "Zero of 124 modules declare brain as a dependency"
outranks "the dependency rule is not followed".
Reconstructed records
Records 0001–0014 were written on 2026-08-23, after the decisions they describe. Records 0015 onward were taken as records. Those
decisions were taken in implementation rather than in a document; the records state what was
decided and the evidence it was decided from, and each carries reconstructed: true and says
so in its first lines.
A reconstructed record is not a transcript. Where the deliberation is not recoverable, the options section states what the alternatives were and why the chosen one won on the evidence available — not a discussion that did not happen. Where a date is not establishable it says so rather than guessing.
Index
The index is generated, not maintained — run the hq-status skill, which reads the
frontmatter of every record. A hand-written index drifts from the folder it describes, and
this one had already done so after a single addition.