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hq/02-DECISIONS
jschoubben 89302aa3e0 The protocol is split per capability, and an SDK implements it
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
2026-09-15 13:40:15 +02:00
..

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 A superseded record has its status: changed and gains a pointer to what replaced it — its text is never edited.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 0019). 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

A number identifies a record and never changes. Records are referenced from outside this repository — code comments, commit messages — so a number that moves invalidates them silently. Renumbering once cost 96 references across two code repositories, and that is why the numbers are now fixed.

So the folder is in creation order, and the reading order lives here. It is generated from each record's topic: and written, because a reader looking at the folder on a forge sees the folder rather than a command. The objection to a written index is that it drifts — which is answered by checking it rather than by refusing to write one:

python3 00-META/checks/index.py --write    regenerate
python3 00-META/checks/index.py            fail if stale

What the mesh is

Its tiers, from the bottom up

What runs on them, and how it gets there

How it is built

How it is checked

How we work