diff --git a/docs/Development-Plan.md b/docs/Development-Plan.md
index a43f7ac..86544af 100644
--- a/docs/Development-Plan.md
+++ b/docs/Development-Plan.md
@@ -130,7 +130,8 @@ Built alongside `control.py`, reusing the state store, log, views, publisher,
 pollers and recovery. The first milestone is the smallest end-to-end path; each
 later one widens it and extends the end-to-end test (M1.6) to cover it.
 
-**M2.1 The slice.** *Needs discussion* (the loop's shape in code).
+**M2.1 The slice.** *Needs discussion* (the loop's shape in code). **Done** (#96,
+#97, #98, #99; first live run: sandbox #255, follow-ups in #100).
 - An issue assigned to `dev-agent` → a work item (D1); a restatement in the item's
   thread; a go-ahead bound to its revision (L3, L5); one milestone through
   `start_milestone` / `finish_milestone` on a harness branch (D4); the PR; a review