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 c49257a8..9eb787df 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
@@ -294,3 +294,11 @@ names the principle that settles it, and is cited as "design 47 G A-n".
 - **A-77** (§373; principles 1 and 7) A wait's bound is a bound key with its own time to live in the waiting part's own
   state, as the condition keeper times its two hours (COND7): its expiry is heard as the bus's event and ends the wait
   then, failing the step naming the member; no timer in the process and no looking only at the next event.
+- **A-78** (§374, §375, §377, §354; principles 1 and 7) For `outdated` and its inputs, the indexer keeps what it hears:
+  (a) `acted.<acting part>.<dependent>` in its own state, the newest `wait-ended` (ran or released) with the build it
+  acted for, compared with the dependent's current build (its newest entry's fingerprint); (b) what a delivered
+  version serves is read from that version's catalog entry (its manifest's `serves` and words); (c) a derived edge is
+  marked by a field `filled: true` the contract's `VersionEdge` gains, the machines that place a module come from the
+  assigner's `placement` (A-62), and each node's last `running` from the node-engine's stream read whole at start
+  (§556); (d) an `inputs` entry is also keyed by its run ask's id, so the build seat's `step-ended` of that ask finds
+  and deletes it.