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 9f7cb4ae..c292c8d6 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
@@ -71,3 +71,8 @@ names the principle that settles it, and is cited as "design 47 G A-n".
 - **A-18** (§587, §305; principle 7) What G retires leaves no trace: the gate's record type drops the `remove` operation
   and `OpRemove` (§587: a removal is no operation), and its `table`, `recheck` and `close` go with their handlers and
   tools (§305). `checks`, which no line retires, stays.
+- **A-19** (§641, §556; principles 1, 7 and 2) `HearSeatEvents` learns that a stream is kept last per subject from the
+  stream's own info on the bus, with no new parameter; its ordered read at the start filters on the same subjects as its
+  durable; the read's messages go to the same handler as the durable's, so one path handles both; it names the read
+  `waiting` and then `read` through one callback option it calls, which the module wires to its first views, so
+  `process` imports nothing of `views`.