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 d015e5d3..f254df8b 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
@@ -339,3 +339,6 @@ names the principle that settles it, and is cited as "design 47 G A-n".
 - **A-86** (§354, §375; principle 7) `KeepInput` is called by the indexer's own `input` verb, when a run on request's asker
   hands an input; the indexer asks no `run` itself. A kind-3 edge's language is its catalog edge's target artifact's
   language, else the one language the entry's artifacts share, as built in mesh-delivery 652285f0.
+- **A-87** (§568, §589, A-70, A-76; principle 7) As built in mesh-delivery bd228d51: a fault with no node says `no node`;
+  `FaultClass` maps `buildstep.PassingCause`'s words onto A-76's four classes. `builder_build`'s `newest: <branch>` is
+  read by the tools bundle following the catalog half itself, as A-70 has it for `reserved`.