ADR 0157: a build says what it does on the bus, as it happens; designs 25 and 18 carry it

2026-10-01 00:43:26 +02:00
parent 763e327610
commit 2ffe1d0915
4 changed files with 127 additions and 3 deletions
@@ -5,8 +5,9 @@ code:
  - mesh-controller cmd/mesh-builder
  - mesh-controller internal/builder
  - mesh-catalog modules/builder
-updated: 2026-09-30
+updated: 2026-10-01
 decisions:
+  - 02-DECISIONS/0157-a-build-says-what-it-does-on-the-bus-as-it-happens.md
  - 02-DECISIONS/0150-a-modules-own-code-runs-as-supervised-processes-under-one-account.md
  - 02-DECISIONS/0142-the-mesh-delivers-its-own-components-as-binaries.md
  - 02-DECISIONS/0111-a-build-source-is-on-the-git-seat-or-external.md
@@ -267,6 +268,28 @@ ships one and wrong for code the mesh built, which has no unit until the mesh wr
 **Tools, hooks and consumers are not further modes**, which is the test of whether three is the
 right number: they are loaded by a tool host, and a tool host is a process that stays up.

+## 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).*
+
+A build machine narrates every build on the bus as the role it holds: `started` when it takes the
+work, one `log.<build id>` event per line — every command it runs with its duration, every step of
+the recipe, and on failure the command's own output, line by line — and `built` for the outcome as
+before. The same lines still go to the machine's standard error, so a build machine with nobody
+listening is as readable as it was; a listener reads the same lines, live, from anywhere on the mesh.
+
+One build is one subject. A reader follows it by subscribing that subject and nothing else, and the
+events stream keeps it for a week, so `builds --log <id>` — on the command line and as the
+controller's seat verb through the console — reads it back afterwards. `builds` lists every build's
+id beside it, and `build` says the id it asked with. The mesh keeps no second copy: the stream is the
+log. A viewer of builds, when one is built, is a subscriber over these subjects and the outcome; the
+builder needs nothing more for it.
+
+*How it is checked:* the holder's grant is exactly `started`, `built` and `log.*` (broker test); a
+build's lines reach a reader of its subject in order and the stream holds them afterwards (link test
+against a real server); the seat verb with an id reads the log (controller test); and, live, a build
+after the roll-out read line by line through the console.
+
 ## The builder compiles the languages the mesh is written in

 *2026-09-29 —