Merge pull request 'Design 18 and ADR 0190: shared build work proven live on all four machines, and the five gaps the switch found' (#313) from design/18-shared-build-work-proven-live into main

02-DECISIONS/0190-a-seats-work-is-shared-by-its-holders-and-building-is-the-first-such-role.md

@@ -102,7 +102,7 @@ is unchanged: a tier's asks go out together and are now worked together.
 | An ask is never delivered to a busy holder | the same test: the busy holder's ask count stays at one until it acknowledges |
 | A holder that dies mid-work leaves its ask for another | the same test, one holder closed mid-ask |
 | The asker names no machine | the controller's seat table: `node-build-agent` accepts `build` and the asking side publishes to the seat's accept subject, as the existing tests of `build` already require |
-| Live | `builds` shows a tier's builds `on` more than one machine within one plan; `seats` shows `node-build-agent` held on every machine with a container runtime |
+| Live | `builds` shows a tier's builds `on` more than one machine within one plan; `seats` shows `node-build-agent` held on every machine with a container runtime — *held on all four machines and a build taken by a workstation's agent, 2026-10-03* |
 
 ## References
 

03-DESIGN/01-to-be/18-building-a-module.md

@@ -5,7 +5,7 @@ code:
   - mesh-controller cmd/mesh-builder
   - mesh-controller internal/builder
   - mesh-catalog modules/build-agent
-updated: 2026-10-02
+updated: 2026-10-03
 decisions:
   - 02-DECISIONS/0190-a-seats-work-is-shared-by-its-holders-and-building-is-the-first-such-role.md
   - 02-DECISIONS/0157-a-build-says-what-it-does-on-the-bus-as-it-happens.md
@@ -283,6 +283,15 @@ the bus credential — said once in the module's manifest. The outcome names the
 This is the bus's shared-work pattern, not a build-specific one: any module declaring a node seat with
 `accepts` has its work shared by its holders the same way. Building is the first use.
 
+*Built and proven live 2026-10-03.* `build-agent` holds `node-build-agent` on all four machines; the first
+build taken by a workstation's agent was a catalogue module at 09:35 UTC; the one-holder `builder` is
+retired. The switch found five gaps, each an issue: a worker whose type changed stranded its holder
+([206](../../04-ISSUES/206-a-seats-worker-changing-type-strands-the-holder-and-the-build-that-would-fix-it/00-report.md)),
+a re-made worker replayed the stream's history ([207](../../04-ISSUES/207-a-re-made-worker-replayed-every-ask-the-stream-kept/00-report.md)),
+a seat's worker is made only when the controller starts ([208](../../04-ISSUES/208-a-seats-worker-is-made-only-when-the-controller-starts/00-report.md)),
+a module's identifier must fit the tightest backend's key (the slug), and an idle machine's empty fetch
+was read as the end (fixed in the controller the same day).
+
 ## A build says what it does, as it happens
 
 *2026-10-01 — [ADR 0157](../../02-DECISIONS/0157-a-build-says-what-it-does-on-the-bus-as-it-happens.md).*