diff --git a/docs/FRICTION.md b/docs/FRICTION.md
index 8b93fb4..68a1be6 100644
--- a/docs/FRICTION.md
+++ b/docs/FRICTION.md
@@ -34,6 +34,15 @@ _(append new raw signals here; the next kaizen review consumes them)_
   boma convention, where prose reminders don't hold. → consider a mechanical guard
   (Stop-hook family) or a CLAUDE.md/skill-override note that suppresses the spec-review
   gate.
+- `[recurring]` **Subagent faithfulness self-reports can be wrong — controller must
+  diff** (2026-06-10): during the ADR-023 retroactive restructure, an implementer
+  subagent reported "0 substantive deletions, the See-also lines reappear verbatim" for
+  ADR-014, but it had actually dropped the cross-reference lines. Caught only by the
+  controller independently running `git show <sha> | grep '^-[^-]'`. For
+  faithfulness-critical edits delegated to subagents, the agent's own audit is not
+  sufficient evidence. → systematize a controller-side deletion-audit step (every `-`
+  line must be a classified, expected change) before accepting any "presentational-only"
+  restructure; consider a helper script.
 
 ---