jschoubben
fccac61e58
Supersedes 0032, which decided the right thing and described it wrongly. The decision is unchanged: the account that installed the host owns the mesh, and there is no user model. What was wrong was inventing "a surface that delegates authentication" for the board. It is a web application with a login, in the way every web application has a login. That is a fact about an application, not a property of the mesh. The cost was not cosmetic. It made the identity module look like part of the mesh's authority — something the mesh depends on to know who anybody is — when the mesh knows nothing about people at all and one of the applications running on it happens to have a login. Keeps the line that is worth writing down, and states it more plainly: signing in to an application must not become authority over the mesh. Today it cannot, because the board reads and does not act. The moment it can assign a module, whoever it lets in has mesh authority — and it would arrive as a feature rather than as a decision. So a surface that can change the mesh is a change to who owns the mesh, and is taken as one. Not forbidden; just not something that turns up in a pull request titled "add assign button".
135 lines
7.3 KiB
Markdown
135 lines
7.3 KiB
Markdown
# 02-DECISIONS
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Architecture decision records — the "why" trail behind the rules in
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[`00-META`](../00-META/) and the specifications in [`03-DESIGN`](../03-DESIGN/).
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**Numbered `02` because a decision precedes the design it authorises.** Research concludes,
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the decision is recorded here, and only then is the design written. Following the folder
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numbers walks the process in the order it happens.
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One file per decision, numbered, never deleted. A superseded record has its `status:` changed
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and gains a pointer to what replaced it — **its text is never edited**. The reasoning that was
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rejected is the expensive half to rediscover.
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The records run in the order the decisions were taken, oldest first.
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**Every decision is a record.** There is no ledger and no index file — if a decision is worth
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recording it is worth a record, and if it is not worth a record it is not recorded
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([ADR 0019](0019-how-this-repository-works.md)). A "decision" small enough to be one line is
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almost always a **rule**, and a rule belongs in
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[`00-META/how-we-build.md`](../00-META/how-we-build.md), where it is enforced and keeps the
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incident that earned it.
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## Frontmatter
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```yaml
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---
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status: proposed | accepted | superseded
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date: YYYY-MM-DD # when the decision was taken, not when it was written down
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deciders: name
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reconstructed: true|false # true when the record was written after the fact from evidence
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superseded-by: # 02-DECISIONS/NNNN-....md, when status is superseded
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extends: # 02-DECISIONS/NNNN-....md, when this record widens an earlier one
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---
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```
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## Body
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```
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# N. Title in plain language
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## Context what was true, with evidence
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## Considered Options numbered, each with why it was rejected
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## Decision what was decided
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## Consequences what follows, including what got harder
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## References commits, pull requests, knowledge-base entries, prior art
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```
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State evidence, not assertion. *"Zero of 124 modules declare `brain` as a dependency"*
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outranks *"the dependency rule is not followed"*.
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## Reconstructed records
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Records 0001–0014 were written on 2026-08-23, after the decisions they describe. Records 0015 onward were taken as records. Those
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decisions were taken in implementation rather than in a document; the records state what was
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decided and the evidence it was decided from, and each carries `reconstructed: true` and says
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so in its first lines.
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A reconstructed record is not a transcript. Where the deliberation is not recoverable, the
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options section states what the alternatives were and why the chosen one won on the evidence
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available — not a discussion that did not happen. Where a date is not establishable it says so
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rather than guessing.
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## Index
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**A number identifies a record and never changes.** Records are referenced from outside this
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repository — code comments, commit messages — so a number that moves invalidates them silently.
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Renumbering once cost 96 references across two code repositories, and that is why the numbers
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are now fixed.
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So the folder is in creation order, and **the reading order lives here.** It is generated from
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each record's `topic:` and written, because a reader looking at the folder on a forge sees the
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folder rather than a command. The objection to a written index is that it drifts — which is
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answered by checking it rather than by refusing to write one:
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```
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python3 00-META/checks/index.py --write regenerate
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python3 00-META/checks/index.py fail if stale
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```
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<!-- index:start -->
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### What the mesh is
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- **0001** — [The mesh brokers capabilities; nodes host; agents think](0001-mesh-brokers-nodes-host-agents-think.md)
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- **0002** — [Nodes communicate over a message broker, not over HTTP](0002-nodes-communicate-over-a-broker.md)
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- **0003** — [An agent is a persistent employee, not an instance of a pool](0003-agents-are-persistent-employees.md)
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### Its tiers, from the bottom up
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- **0004** — [A node, and how it joins](0004-a-node-and-how-it-joins.md)
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- **0005** — [The node host](0005-the-node-host.md)
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- **0006** — [The substrate and the control plane](0006-the-substrate-and-the-control-plane.md)
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- **0007** — [Connectivity](0007-connectivity.md)
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- **0008** — [A context owns its store, exclusively](0008-a-context-owns-its-store.md)
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- **0028** — [The substrate supplies the control plane and nothing else](0028-the-substrate-supplies-the-control-plane-and-nothing-else.md)
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- **0029** — [A network is a shape, because an action cannot be undone](0029-a-network-is-a-shape-because-an-action-cannot-be-undone.md)
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- **0030** — [Data outlives the mesh that declared it](0030-data-outlives-the-mesh-that-declared-it.md)
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- **0031** — [The control plane authenticates nobody, so identity is a module](0031-the-control-plane-authenticates-nobody.md)
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- **0033** — [The substrate is a store and a broker](0033-the-substrate-is-a-store-and-a-broker.md)
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### What runs on them, and how it gets there
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- **0009** — [Modules and the graph](0009-modules-and-the-graph.md)
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- **0010** — [Delivery](0010-delivery.md)
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- **0024** — [Model access is a provision, and a licence is a thing with a name](0024-model-access-is-a-provision.md)
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- **0026** — [The mesh has a session of its own, and it is the node session's mechanism](0026-the-mesh-has-a-session-of-its-own.md)
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- **0027** — [A provision names what the consumer is coupled to, not the role it plays](0027-a-provision-names-what-the-consumer-is-coupled-to.md)
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### How it is built
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- **0011** — [Managed files are generated onto nodes and never edited there](0011-managed-files-are-generated-never-edited.md)
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- **0012** — [The mesh creates no symlinks — a derived file is a copy](0012-the-mesh-creates-no-symlinks.md)
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- **0013** — [Schema and state changes are numbered migrations, in the same language as the code](0013-schema-changes-are-numbered-migrations.md)
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- **0014** — [No workspace — each module is a standalone package consuming published dependencies](0014-no-npm-workspace.md)
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- **0015** — [Applications live in their own repository; the monorepo is for the mesh](0015-applications-live-in-their-own-repository.md)
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- **0016** — [The lab](0016-the-lab.md)
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### How it is checked
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- **0017** — [A test defends a decision](0017-a-test-defends-a-decision.md)
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- **0018** — [A picture of a system is read from the system, never from what asked for it](0018-a-picture-is-read-from-what-runs.md)
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### How we work
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- **0019** — [How this repository works](0019-how-this-repository-works.md)
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- **0020** — [The mesh is governed by a constitution, injected where work is decided](0020-the-mesh-is-governed-by-a-constitution.md)
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- **0021** — [HQ is the source of the mesh constitution](0021-hq-is-the-source-of-the-constitution.md)
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- **0022** — [The constitution absorbs what is already enforced](0022-the-constitution-absorbs-what-is-enforced.md)
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- **0023** — [The approval is the checkpoint, not the second pair of hands](0023-approval-is-the-checkpoint.md)
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- **0025** — [The design record is read where it is written, never copied to be found](0025-the-design-record-is-read-not-copied.md)
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- **0032** — [The local account owns the mesh; a surface delegates to a module](0032-the-local-account-owns-the-mesh.md) *(superseded)*
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- **0034** — [The local account owns the mesh, and a web application's login is not that](0034-the-local-account-owns-the-mesh.md)
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<!-- index:end -->
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