diff --git a/engineering/0004/SESSION-0004.0-TRANSCRIPT-2026-06-05T12-37--INPROGRESS.md b/engineering/0004/SESSION-0004.0-TRANSCRIPT-2026-06-05T12-37--INPROGRESS.md
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+# Session 0004.0 — Transcript
+
+> App: engineering
+> Start: 2026-06-05T12-37 (PST)
+> Type: coding
+> Status: **PLACEHOLDER — claimed at session start; finalized at session end.**
+>
+> This file reserves session ID 0004 for engineering. The driver replaces this
+> body with the full transcript and renames the file to its final
+> SESSION-0004.0-TRANSCRIPT-2026-06-05T12-37--<end>.md form at session end.
+
+## Launch prompt
+
+```
+Tangent: define best practices for a "Solution Design" (a combined business analyst + product + engineering spec) in the Engineering docs, and reference it in the engineering handbook.
+
+A Solution Design should contain:
+- Business Context
+- Problem Statement
+- Targeted Business Outcome(s) with success metrics
+- Business Use Cases — BDD format, business-centric (no product/technical detail), each with acceptance criteria (what does a user successfully completing that business scenario look like?)
+- Product Use Cases — BDD format, describe the UX (buttons, notifications, etc.), each linked to a Business Use Case where applicable
+- Wireframes — show the user experience; doesn't need to be polished, but UX components should be in approximately the right location
+- Technical Design — high-level architecture diagrams, and for each Product Use Case a sequence diagram + technical implementation details
+- Delivery Plan — overall approach/strategy, then a Slicing Plan (Slices -> completed Product Use Cases), plus anything else useful for execution
+
+Question to answer: "Am I missing anything?"
+
+```
+
+## 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
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--- a/engineering/sessions.json
+++ b/engineering/sessions.json
@@ -7,5 +7,8 @@
   },
   "0003": {
     "title": ""
+  },
+  "0004": {
+    "title": ""
   }
 }