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 b47dc0e3..16dd3db1 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
@@ -393,3 +393,6 @@ names the principle that settles it, and is cited as "design 47 G A-n".
 - **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.
+- **A-100** (§379, A-96; principle 7) As built in mesh-delivery a5e1a5e5 and 5a352482: `build.ended` is said for a done
+  build only; its `branch` is empty for the trunk; its old-section stream keeps 7 days with no keep-last setting (an
+  old `streams` entry has none), which A-96's "kept last per subject" gives up.