diff --git a/docs/RUST.md b/docs/RUST.md
index 66ce214..be43531 100644
--- a/docs/RUST.md
+++ b/docs/RUST.md
@@ -231,6 +231,15 @@ closes it.
   app's runtime log, design the smallest route (the app keeps its own
   recent log; a debug button copies it; Dev Updater reads it), write
   the decision in docs/DECISIONS.md, build it.
+- [x] APK size: release profile tuned (`42af780`), -35% APK, -40% .so;
+  see "APK size (2026-09-07)". **Open question for Iris**: 3.6 MB of the
+  remaining 11.2 MB .so is six embedded Noto Sans TTFs
+  (`iris/core/src/primitive/text.rs`). Loading the platform's own fonts
+  instead (fontique's system collection: Roboto/Noto on Android, the
+  desktop's own on Linux) removes them and makes text match what the
+  rest of her phone shows (UI_RULES "show what the reader already sees
+  elsewhere"), at the cost of the app no longer looking identical on
+  every device. Not done without her verdict.
 - [ ] Masks with a shape -- docs/LAYOUT.md "Masks with a shape (decided
   2026-09-07)". A mask references a primitive already drawn
   (rect SDF, texture or glyph alpha), chained and multiplied; `.masked()`