diff --git a/03-DESIGN/01-to-be/47-milestones/G-22-lead-answers-2.md b/03-DESIGN/01-to-be/47-milestones/G-22-lead-answers-2.md
index 3e013d70..b7c682e7 100644
--- a/03-DESIGN/01-to-be/47-milestones/G-22-lead-answers-2.md
+++ b/03-DESIGN/01-to-be/47-milestones/G-22-lead-answers-2.md
@@ -164,3 +164,6 @@ the principle that settles it, cited as "design 47 G A-n".
 - **A-220** (§71, §441, A-167, A-207, A-215; principle 7) The serving parts `widens` compares are the holders of the
   seats `mesh-pipeline-runner` (the runner), `mesh-catalog` (step detection), each step's own seat (the build seats
   that run lint and tests) and `node-engine` (the composer, A-167), found by `seatlist.HolderOf`.
+- **A-221** (§509, A-208; principle 8, one word per thing) On every forge message `branch` names the watched branch
+  the move changed, on `merged` as on `pushed`; a merged pull request's own branch is kept as `head` (a group is
+  known by its head branch); `pushed`'s head before is `before`.