run 26

docs/pt2-protocol-summary.md

@@ -285,6 +285,11 @@ Current caution:
   `A0`, `EC` fell back to `07 80 C0 40 30 6D`.
 - Exact and host-shaped handling of `07 80 FB 50 26 50` did not yield a stable
   next-stage response.
+- Follow-up context tests suggest `A0` matters beyond `EC`:
+  without `A0`, both `E8` and `E9` fell back to `07 80 40 40 30 ED` instead of
+  opening their known `7A` branches.
+- At the same time, `A0` is not sufficient to make every branch deterministic:
+  a later `A0 -> E9` control repeat returned heartbeat only.
 
 ## What We Know
 
@@ -322,8 +327,8 @@ Current caution:
 - Overall, the evidence is getting stronger for selector-like host entries that
   open related response families, but weaker for a fully reproducible multi-turn
   "conversation" state.
-- At least on the `EC` branch, `A0` now looks more like part of the selection
-  context than a purely generic primer.
+- `A0` now looks more like part of the selection context than a purely generic
+  primer, but its effect is branch-dependent and not fully deterministic.
 
 ## What We Do Not Know