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 e06812b7..c68f227c 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
@@ -307,3 +307,7 @@ names the principle that settles it, and is cited as "design 47 G A-n".
   existing `grants_first_views`; while the catalog half is unread the part keeps what the bus loaded and only adds,
   which is §684's way past the cycle, so no registered branch holds nothing. The part's remaining reads of the
   indexer's `manifests`, `modules` and `verdicts` go too (§196): the catalog half answers them.
+- **A-80** (A-66, A-68, A-69, §375, §73; principles 7 and 8) What the indexer keeps as heard (`steps-since`, `toolchain`,
+  `delivered`, `pending`, `acted`) lives in one state of its own, `heard`, not in `own-build`, which keeps its one key;
+  every key part is escaped as a name (§73), so a dotted module name parses; a kind-3 edge compares its artifact's
+  language with `toolchain.<language>`.