diff --git a/CLAUDE.md b/CLAUDE.md
index be343f61..1312d5ed 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -227,6 +227,34 @@ Before accepting a spec, run it past
 a spec around "no Rust changes required" — correct layer placement is the goal,
 not minimal backend churn.
 
+### 🔴 A spec becomes an architecture doc when it ships
+
+`docs/specs/` holds **only work that has not shipped**. There is no "Implemented"
+resting state for a spec file: when the last acceptance criterion is met, fold
+the design into [docs/architecture/](docs/architecture/README.md) and **delete
+the spec in the same commit**.
+
+This is not tidying. A directory that mixes promises with descriptions makes both
+unreliable — you cannot tell from a file whether it describes the build or
+proposes a change to it, and stale specs then quietly disagree with the code
+while reading as authority.
+
+- **Every spec names its destination up front** — the template's "Destination on
+  completion" line. Deciding at spec time which architecture doc will absorb it
+  is a design check in itself: a feature that fits no existing doc is usually a
+  feature whose layer assignment is unclear.
+- **Carry the reasoning, not the plan.** The architecture doc gets the *why* a
+  future change still needs — invariants, rejected alternatives that would be
+  re-attempted, the defect a piece of code exists to prevent. Acceptance
+  criteria, phase breakdowns and migration steps die with the spec; git history
+  keeps them.
+- **Deferred work outlives its spec.** Anything the spec listed as out-of-scope
+  and still worth doing goes beside the code it concerns, not into the void.
+- **Rewrite inbound references before deleting** — source comments and CI
+  scripts cite spec paths, and `check-doc-links` only sees markdown.
+- **Partially implemented is a real status.** A spec stays until *all* of it
+  ships, with the header naming what is left.
+
 ## Conventions
 
 ### Rust Backend
diff --git a/docs/specs/SPEC-REVIEW-CHECKLIST.md b/docs/specs/SPEC-REVIEW-CHECKLIST.md
index f6114b35..9f287814 100644
--- a/docs/specs/SPEC-REVIEW-CHECKLIST.md
+++ b/docs/specs/SPEC-REVIEW-CHECKLIST.md
@@ -53,6 +53,18 @@ Copy the boxes into the review comment (or the PR) and tick them.
 - [ ] Traceability coverage stays ≥ 88% (the CI gate — a ratchet, so check
       `bun run traces:coverage` rather than trusting this number).
 
+## Lifecycle
+
+- [ ] **"Destination on completion" names a real architecture doc and section.**
+      This spec file is deleted when it ships; something has to absorb the
+      design. If nothing fits, the layer assignment is probably unclear — go back
+      to that table.
+- [ ] The spec separates the **durable half** (invariants, rejected alternatives,
+      the defect a decision exists to prevent) from the **disposable half**
+      (phases, migration steps, acceptance criteria). Only the first is folded in.
+- [ ] Anything listed as out of scope but still worth doing is written where it
+      will be found after this file is gone — beside the code it concerns.
+
 ## Conflicts & hygiene
 
 - [ ] If this spec revises/supersedes another, the older spec gets a banner
diff --git a/docs/specs/SPEC-TEMPLATE.md b/docs/specs/SPEC-TEMPLATE.md
index e27df44b..61e28a5e 100644
--- a/docs/specs/SPEC-TEMPLATE.md
+++ b/docs/specs/SPEC-TEMPLATE.md
@@ -6,12 +6,27 @@
   "Layer assignment" — read its comment before writing it.
 
   Before merging a spec, run it past docs/specs/SPEC-REVIEW-CHECKLIST.md.
+
+  LIFECYCLE: this file is temporary. docs/specs/ holds only unshipped work — when
+  the last acceptance criterion is met, the design is folded into
+  docs/architecture/ and this file is deleted in the same commit. Write it
+  knowing that: the durable half is the reasoning (invariants, rejected
+  alternatives, the defect a decision prevents), and the disposable half is the
+  plan (phases, migration steps, acceptance criteria).
 -->
 
-**Status:** Proposed <!-- Proposed | Accepted | Implemented | Superseded -->
+**Status:** Proposed <!-- Proposed | Accepted | Partially implemented | Superseded.
+     NOT "Implemented" — a fully shipped spec is folded into docs/architecture/
+     and deleted. See "Destination on completion" below. -->
 **Requirements:** <!-- UR-xxx → DR-yyy; allocate new DRs in requirements.md. -->
 **UX spec:** <!-- link to the relevant ux-flows.md section, or "n/a". -->
 **Supersedes / revises:** <!-- link any spec this changes, or delete this line. -->
+**Destination on completion:** <!--
+     Which architecture doc absorbs this design when it ships, and roughly which
+     section. e.g. "05-platform-backends.md — a new section beside
+     ExoPlayerBackend". Name it NOW: a feature that fits no existing doc usually
+     has an unclear layer assignment, which is worth finding out at spec time.
+     This spec file is deleted in the same commit that folds it in. -->
 
 ## Summary