diff --git a/03-DESIGN/01-to-be/47-milestones/G-20-lead-answers.md b/03-DESIGN/01-to-be/47-milestones/G-20-lead-answers.md
index 397e93f5..b47dc0e3 100644
--- a/03-DESIGN/01-to-be/47-milestones/G-20-lead-answers.md
+++ b/03-DESIGN/01-to-be/47-milestones/G-20-lead-answers.md
@@ -390,3 +390,6 @@ names the principle that settles it, and is cited as "design 47 G A-n".
 - **A-98** (§297; principles 3 and 7) The node agent gains one act, `Env.Stop`: it stops a module's units and containers
   and removes nothing, so a revert's data survives; the revert stops the newer build with it, asks `restore-kept`, and
   then `Apply` starts the reverted build. `Remove` keeps its meaning.
+- **A-99** (§230, A-91, A-97; principle 7) `build` is a step every pipeline has, placed first and required whatever its
+  policy names, so the runner's step enum gains `build`; each module's pipeline asks the build of its own module's
+  entry only, and a group's members are built by their own pipelines.