diff --git a/engineering/0021/SESSION-0021.0-TRANSCRIPT-2026-06-11T21-42--INPROGRESS.md b/engineering/0021/SESSION-0021.0-TRANSCRIPT-2026-06-11T21-42--INPROGRESS.md
new file mode 100644
index 0000000..dcdbef2
--- /dev/null
+++ b/engineering/0021/SESSION-0021.0-TRANSCRIPT-2026-06-11T21-42--INPROGRESS.md
@@ -0,0 +1,24 @@
+# Session 0021.0 — Transcript
+
+> App: engineering
+> Start: 2026-06-11T21-42 (PST)
+> Type: planning-and-executing
+> Claude-Session: 207b955c-7e90-4dbb-a6a0-3489acd31538
+> Status: **PLACEHOLDER — claimed at session start; finalized at session end.**
+>
+> This file reserves session ID 0021 for engineering. The driver replaces this
+> body with the full transcript and renames the file to its final
+> SESSION-0021.0-TRANSCRIPT-2026-06-11T21-42--<end>.md form at session end.
+
+## Launch prompt
+
+```
+Build gitea-forge-backups SLICE-4 — restore runbook (RB-1/RB-2 → infra/backup-restore-gitea.md) + one proving drill onto a scratch Gitea, T-2 green, drill recorded, per specs/gitea-forge-backups.md §7.2 (engineering#30)
+
+```
+
+## Deferred decisions
+
+_Autonomous-mode low-confidence calls the driver made and would have
+liked operator input on. Appended as the session runs; surfaced at
+finalize. Empty if none._
diff --git a/engineering/sessions.json b/engineering/sessions.json
index 3c3a163..71262a5 100644
--- a/engineering/sessions.json
+++ b/engineering/sessions.json
@@ -58,5 +58,8 @@
   },
   "0020": {
     "title": ""
+  },
+  "0021": {
+    "title": ""
   }
 }