Issue 170: assigning a module claims every seat it could hold

Assigning postgres on ace claimed mesh-store and made novox's own store assignment unresolvable. The resolver reads a manifest's claims as 'does hold'; ADR 0110 says the assignment holds, by a deliberate act the controller already has (seat …, HoldSeat) but resolution does not consult.
2026-09-30 14:29:11 +02:00
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+---
+status: open
+opened: 2026-09-30
+located-in:
+  - mesh-controller internal/catalogue/resolve.go (holdings are derived from every resolved assignment's manifest `claims`)
+  - mesh-controller cmd/mesh-controller/seats.go (the deliberate act exists — HoldSeat, "recording … as its standing holder" — beside it)
+fixed-by:
+amended-design:
+---
+
+# 170 — Assigning a module claims every seat it could hold
+
+## What was observed
+
+ace's migration needs a postgres of its own: the operator's decision is that a `postgres` module
+assigned on ace provides `postgres-database` to ace's modules and has **nothing to do with the
+`mesh-store` seat**, which novox's assignment holds by a deliberate act already taken ("make
+novox's postgres the mesh-store").
+
+`assign ace postgres` (2026-09-30):
+
+```
+ace is assigned postgres
+
+AND 1 other machine(s) cannot be worked out as things stand, so nothing will be sent to them:
+  novox
+    - postgres on novox claims "mesh-store", which postgres on ace already holds — one per mesh
+mesh-controller: these assignments cannot be applied:
+  - postgres on ace claims "mesh-store", which postgres on novox already holds — one per mesh
+```
+
+The second assignment did not merely fail: it made **the control plane's own store's
+assignment unresolvable** until unassigned. Nothing was pushed; the state is restored.
+
+## Why
+
+`resolve.go` derives what a node holds from the manifest's `claims` of every module resolved on
+it, so a claim in a definition is a claim by every assignment of that module. The deliberate
+act ADR 0110 describes exists beside it — `seat …` records "X on Y as its standing holder"
+(`HoldSeat`) — but resolution does not consult that record; it consults the manifests.
+
+## What was decided
+
+[ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md):
+
+> **A definition says which seats a module *can* hold. An assignment says which it *does*
+> hold.** The store module can hold `mesh-store`, and it may be assigned to every node. Exactly
+> one of those assignments holds the seat, because that assignment said so.
+
+The manifest's `claims` is being read as *does hold*.
+
+## What would be right
+
+Resolution takes the holder of a seat from the recorded holding (the seat's standing holder),
+not from the manifests: a module whose definition can hold a seat is assignable anywhere, and only
+the assignment recorded as holder claims it — with the refusal reserved for a second *recorded*
+holder at the seat's scope. Assigning postgres to ace is then exactly what the operator said it
+is: a database provider on ace, and no more.
+
+## Until then
+
+`postgres` cannot be assigned on any second node; ace's database windows (baserow, letta, n8n,
+car-hunter, txt-game) wait on this.