# 02-DECISIONS

Architecture decision records — the "why" trail behind the rules in
[`00-META`](../00-META/) and the specifications in [`03-DESIGN`](../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 A superseded record has its `status:` changed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](0026-every-decision-is-a-record.md)). A "decision" small enough to be one line is
almost always a **rule**, and a rule belongs in
[`00-META/how-we-build.md`](../00-META/how-we-build.md), where it is enforced and keeps the
incident that earned it.

## Frontmatter

```yaml
---
status: proposed | accepted | superseded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superseded-by:            # 02-DECISIONS/NNNN-....md, when status is superseded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 `hal-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.