diff --git a/.trellis/spec/hyb-oa/project-governance.md b/.trellis/spec/hyb-oa/project-governance.md
index 81749beb..61c4a9d9 100644
--- a/.trellis/spec/hyb-oa/project-governance.md
+++ b/.trellis/spec/hyb-oa/project-governance.md
@@ -72,6 +72,14 @@ tasks after TRELLIS2.
   Do not treat that inferred task as new execution approval. Activate
   the next approved task explicitly when work actually resumes. Commit, push,
   archive and production operations retain their separate approval boundaries.
+- Worktrees are for genuine isolation (risky merges, DB-touching regression
+  runs, parallel tasks across sessions/agents), not a default habit. Once the
+  isolated work is merged or its branch's HEAD is an ancestor of the target
+  branch, remove the worktree (`git worktree remove`) instead of leaving it
+  "for later" — this project has previously accumulated over a dozen stale
+  worktrees consuming double-digit GB of disk because cleanup was deferred.
+  A quick `git worktree list` + `git merge-base --is-ancestor <head> main`
+  check identifies safe-to-remove ones during any disk or repo-hygiene pass.
 
 ## Risk-Scoped Execution