diff --git a/SKILL.md b/SKILL.md
index 5bdc136..1ac5128 100644
--- a/SKILL.md
+++ b/SKILL.md
@@ -541,7 +541,10 @@ and reconciles the target doc with the Body.
   other's running build. Nothing was lost, only because the second agent
   stopped and reported a concurrency hazard instead of forcing the checkout.
   **A brief that names a repo path without naming a worktree is a defect in
-  the brief.**
+  the brief.** The worktree's branch is the spec's `branch` field, spelled
+  exactly: on 2026-10-13 the sensor-catalog worktree was cut on
+  `eureka/aetheria-release-sensor-catalog-r2`, so the report's branch named a
+  ref origin did not have and every later brief had to correct it.
 - **Commit the prose map to `main`, and name its branch in every brief.** On
   2026-09-22 a Hands agent found no fix-batch-4 section: the live copy was on
   Self's working branch, and `main` was a day behind. Specs now live in the
diff --git a/references/changelog.md b/references/changelog.md
index 4f65410..38bdca4 100644
--- a/references/changelog.md
+++ b/references/changelog.md
@@ -2,6 +2,14 @@
 
 Record each change to the skill together with the evidence that motivated it.
 
+## 2026-10-14: a worktree's branch is the spec's branch
+
+Self, session `self-2026-10-14-ag`.
+
+Evidence. `aetheria-release:cut_report:cut-sensor-catalog.h4` names branch `eureka/aetheria-release-sensor-catalog`, the spec's; the worktree Self cut was on `eureka/aetheria-release-sensor-catalog-r2`, the only ref origin has. The Soul s3 brief had to carry the correction. Lesson recorded in the 2026-10-13b handoff, found in no owner by Life on re-entry.
+
+What changed. `SKILL.md`, Self's worktree bullet: the worktree's branch is the spec's `branch` field, spelled exactly.
+
 ## 2026-10-12: no test run of any size on Starfire
 
 Self, session `self-2026-10-12-eureka`.