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The consolidation left a sparse sequence -- 1, 4, 6, 7, 9, 10, 12, 15, 16, 18, 19, 25, 34, 35, 36, 37, 40, 42, 44, 45, 48, 49, 58 -- where the gaps were only the archaeology of what used to be there. Renumbered contiguously. Renames run in ascending order, so every target number is already free and no two files ever collide. The reference rewrite is one simultaneous pass rather than a sequence of replacements. Numbers moved into slots other numbers were vacating -- the node host went 37 to 16 while the lab went 16 to 9 -- so replacing one at a time would have cascaded and silently pointed things at the wrong record. Seven plain-text references survived the merges as prose rather than links, naming records that no longer existed: the enrolment token, the link boundary, what a declaration is, reachability, the repository structure. Each mapped to the consolidated record that now holds it. Verified rather than assumed: every [ADR NNNN](path) link now has matching text and target, checked across the whole repository, and the checker passes. Frontmatter `consolidates:` lists dropped -- they named records that are gone, and each consolidated record already says in prose what it absorbed.
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status, date, deciders, reconstructed, extends
| status | date | deciders | reconstructed | extends |
|---|---|---|---|---|
| accepted | 2026-08-26 | jochen | false | 0019-modules-and-the-graph.md |
20. A context owns its store, exclusively
Context
ADR 0019 settles what a module declares. This settles what a grant may be, and it is the half that removes things.
how-we-build §4 already says contexts integrate through the record, never through a shared
schema, and states the cost: several domains share one forty-five-table schema, which is why
work belonging to one context keeps having to be implemented in another.
That was written as a principle. Counted, it is thirteen foreign tables belonging to three separate contexts, living in the mesh's own registry database.
Considered options
- A schema per consumer inside a shared database. Namespaced, revocable by dropping the schema, with a cross-context join possible but deliberate. Rejected: it keeps the letter of §4 and leaves the temptation in place, and a boundary that is merely inconvenient to cross gets crossed.
- Read-only roles on another context's store. Rejected for the same reason and one worse: reading another context's tables couples you to its layout exactly as firmly as writing them, and the coupling is invisible until the owner changes a column.
- Exclusive ownership. Chosen.
Decision
A context is granted only what it exclusively owns.
No shared writes. No read-only role on another context's store. If you need what another context holds, you ask it or you subscribe to it.
The unit is the context, not the process. Everything inside a context — its service, its surface, its tools — reads its own store freely. A board showing the mesh's own nodes and modules is the mesh showing its own data, not a boundary crossing. What is forbidden is a different context reading it.
Asking or subscribing is derived, not chosen
ADR 0015 makes disconnection an ordinary situation. So:
- Anything that must keep working while disconnected cannot ask — there is nobody to ask. It keeps a local copy, which means subscribing.
- Anything where a stale answer is worse than none cannot subscribe. A display may lag; a decision about whether a grant is still valid may not.
Neither is a query against another store, whatever transport it travels over.
What this removes
The first clear list of what the design deletes rather than adds:
- Grant kinds. There is one: an exclusive resource. No schema grants, no read roles, no rules about who may see what inside a shared thing.
- The question of who owns which table, and the guessing at revocation time. Removing a consumer drops what it was granted, whole.
- Cross-context migration ordering. Two contexts migrating one database must be ordered against each other. Exclusive ownership means a context's migrations are ordered only against itself.
- A class of permission modelling a shared store would otherwise need.
Consequences
- Cross-context reporting is harder, and that is the point. Anything wanting to see across contexts consumes their events or calls their interfaces. That is §4's argument, and the cost it names is the one already paid.
- A single surface over several contexts still works — that is what a surface is. It reads interfaces, not stores. This holds while the contexts sit behind one interface; splitting a context into its own deployable costs that, and the composition would have nowhere to live that tier 3 permits. A real constraint on how far the control plane may be split.
- Three contexts must move out of the registry database, taking thirteen tables with them. Their dependency on the registry then shrinks to almost nothing — one of them needs a single table.
- The node appliers were already handled. ADR 0016 stopped the host querying the mesh database for tier reasons unrelated to this, and it removes most of the remaining direct readers as a side effect.
- What a consumer does about events missed while disconnected is not decided — replay from a point, ask once and resume, or rebuild. The question every projection has.
References
how-we-build.md§4 — the rule this makes enforceable.- Research 011 — the count, the worked provider, and the dashboard case.
- ADR 0015 — why asking or subscribing is derived.