2026-09-05 10:27:11 +00:00
1 changed files with 24 additions and 0 deletions
@@ -208,6 +208,30 @@ first clear instance:
  against itself.
 - **A whole class of permission modelling** that a shared store would otherwise need.

+### The hardest case for it: a dashboard reading everything
+
+Raised immediately, and it is the right test — a board showing nodes, modules, pipelines, agents
+and tasks wants to read a dozen stores. Under this rule it cannot read any of them.
+
+**It survives, and not by luck: the board is a surface, and surfaces already may not do this.**
+The skeleton puts `api/` in the control plane as *the one interface every surface speaks to*, and
+tier 3 as *thin; no logic lives here*. A board reading stores directly is a surface reaching past
+the context that owns the data — which the tier rule forbids for reasons that have nothing to do
+with databases.
+
+So the dashboard is not a counter-example. It is an instance the rule catches, and the two rules
+turn out to be one rule seen from two sides: **exclusive ownership is the tier rule, expressed in
+terms of storage.**
+
+**The general shape, for anything that needs to see across many things:** consume the record and
+own your own view. A reporting context builds a projection from events and reads its own store.
+It does not read anybody else's.
+
+**And the cost is not small, so it should be said plainly.** A projection is more work than a
+join, and it lags. Today a board queries the mesh's own database directly — that is ordinary,
+it works, and this rule makes it a migration rather than a preference. The reason to pay it is
+[`how-we-build`](../../00-META/how-we-build.md) §4's already-measured cost, not elegance.
+
 ### What it does not answer

 **The mesh's own registry is read by many things.** Under this rule they cannot read its tables,