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 d6d5f1fa..2088c0b5 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
@@ -61,3 +61,7 @@ names the principle that settles it, and is cited as "design 47 G A-n".
 - **A-15** (§614; principle 3) In the branch follower an `entry` the holder refuses is `not-found`; a transport error leaves
   it `asked` and is asked again; each part writes `entry-not-found` from the follower's changes. As built in mesh-delivery
   ab616fa6.
+- **A-16** (§461, §485, §503; principle 7, the rule that shared code lives in mesh-sdk) A stdio module's writer is made by
+  one mesh-sdk constructor, `views.NewStdioWriter`, generic as the writer is,, which fills `Publish` from the module's own event
+  publish and `Listen` from its subscription; no module writes that adapter. The tool runner's own finding writer
+  (mesh-tools' first views) hands in `Publish` and `Listen` from its bus connection, in its one place.