diff --git a/docs/contract-additions/e12-ota-backup.md b/docs/contract-additions/e12-ota-backup.md
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+# E12 — Sovereign OTA + Snapshot/Backup (Software Update + Time Machine)
+
+**Gap #5 of the [feature-gaps-zero campaign](https://github.com/SourceOS-Linux/sourceos-spec/issues/267).**
+Replaces two macOS subsystems at once — **Software Update** (OTA) and **Time Machine /
+Migration Assistant** (backup/restore) — with a signed, reproducible, rollbackable
+generation model. No vendor cloud; every update and every restore is consent-gated and
+receipted, and a failed verify rolls back fail-closed.
+
+## Update model — signed atomic generations
+An update is a new **generation** of the reproducible image tree (Guix generations /
+Nix profiles), never an in-place mutation. It follows the [B₁₁ change loop](../surfaces/b11-life-mirror.html)
+exactly:
+
+| Step | What | Fail-closed rule |
+|---|---|---|
+| **A · stage** | fetch a signed image; verify signature + provenance (SLSA/in-toto) | unsigned or unverifiable ⇒ refuse, never staged |
+| **B · verify** | boot-test the generation; run the eval gate; the twin re-mirrors the new surface set | any check red ⇒ **auto-rollback** to the last sealed generation |
+| **Q · commit** | owner consent (QR / present-owner) commits the generation as default-boot | no consent ⇒ hold on the current generation |
+
+The base is sealed by **measured boot** (PureBoot/Heads + dm-verity) — the Atzilut
+seal in the framework. A tripwire trip *during* an update drives the automaton to
+SAFE-HALT and hands recovery to the present owner.
+
+## Backup model — generations to a sovereign store
+- **Snapshot:** each generation + user-space state snapshots to a sovereign store
+  (prophet-backups / MinIO via restic/borg), encrypted, agent-scoped, region-tolerated
+  (GDPR Ch. V — same residency rule as the consent plane).
+- **Restore / migrate:** restoring is *booting a prior generation* — Migration Assistant
+  parity without a vendor account. Diff any two generations before committing a restore.
+
+## Governance
+An OTA is `purpose = administer` (commit) / `ship` (publish an image); a restore is
+`operate`. All are consent-gated + emit an `AutonomyAdmissionReceipt` bound to the
+generation hash. The runtime enforcement is the same [consent plane](./e11-consent-receipts-ux.md);
+the surface is the E11 pane (an update shows as a pending consent with its warrant).
+
+## Superiority over macOS
+- **Reproducible + rollbackable** — every update is a content-addressed generation you can
+  diff and revert; Software Update is neither.
+- **Receipted** — each update/restore is a sealed receipt with its warrant; macOS shows a spinner.
+- **No vendor cloud** — backups live in *your* sovereign store, not iCloud.
+
+## Done-definition
+Signed atomic update-tree + measured-boot attestation + snapshot/restore of a generation,
+all consent-gated + receipted; passes the **update seam** purple-team test (no path commits
+an unsigned, unverified, or un-consented generation as default-boot).
+
+## Non-goals
+Not a package manager (that's Guix/Nix underneath) and not a general file-sync product —
+E12 is specifically the *update + backup/restore generation lifecycle* and its governance.
diff --git a/docs/contract-additions/sovereign-shell-assembly.md b/docs/contract-additions/sovereign-shell-assembly.md
new file mode 100644
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+++ b/docs/contract-additions/sovereign-shell-assembly.md
@@ -0,0 +1,46 @@
+# Sovereign Shell Assembly — how the OS is built from the parts
+
+The build index for the SociOS/SourceOS agentic shell: every component the
+[feature-gaps-zero campaign](https://github.com/SourceOS-Linux/sourceos-spec/issues/267)
+produced, its owning repo, and where it plugs into the [source-os](https://github.com/SourceOS-Linux/source-os)
+image build. Read with the [census](./macos-replacement-matrix.md) (the *what*) and the
+[integrated-agent-native-stack contract](./integrated-agent-native-stack.md) (the *how*).
+
+## Components (built this campaign)
+| Component | Repo | Kind | Integration point |
+|---|---|---|---|
+| Consent plane (spaces/purposes/gate) | agent-standards · policy-fabric · goose-guard · ontogenesis | runtime + ontology | enforced at 3 surfaces; TCC replacement |
+| lampstand (parse + router) | sourceos-shell `tools/lampstand_*` | service logic | Spotlight replacement; routes to IR + consent |
+| MeshTransfer (E3) | sourceos-shell `tools/mesh_transfer` | schema + gate | Continuity/AirDrop; `sourceos-shell` mesh service |
+| netwatch (System Graph) | TurtleTerm `turtle-netwatch` | agent | Activity Monitor replacement; ingests to hellgraph |
+| Canonical surfaces (7) | sourceos-spec `docs/surfaces/` | UI + tokens | E11 pane, B₁₁ automaton, launcher, turn-witness, framework, genesis/flywheel |
+| Surface feeds + producer | sourceos-spec `docs/surfaces/data` + `tools/build_surface_feed.py` | live-state seam | surfaces read feeds; `provenance` LIVE/SAMPLE |
+| E12 OTA + backup | (spec) `e12-ota-backup.md` | generation lifecycle | Software Update + Time Machine replacement |
+
+## Vendored dependencies (consumed, not forked)
+Pinned by release + verified by `tools/verify_vendor.py` (recomputes the deterministic
+`git archive` sha512). A pin that can't be verified is a build failure.
+
+| Dep | Pin | Why vendored | Lock |
+|---|---|---|---|
+| **hellgraph** (System Graph) | `v0.4.45` (`dbe854f`) · MIT | not our lane — netwatch ingests into it; surface feeds read from it | `vendor/hellgraph.lock.json` |
+
+> Rule: hellgraph is **consumed vendored**, never modified here. Bump the pin by
+> re-running `verify_vendor.py --checkout <path>` against a new release tag.
+
+## Build order (bottom-up)
+1. **Base** — measured boot (Heads + dm-verity) seals the image (Atzilut). *(source-os)*
+2. **Substrate** — vendored hellgraph (System Graph) + telemetry. *(vendored + source-os)*
+3. **Governance** — consent plane loaded; taints/tolerations active (fail-closed). *(agent-standards/policy-fabric)*
+4. **Shell services** — lampstand, mesh transfer, netwatch, goose. *(sourceos-shell/TurtleTerm)*
+5. **Surfaces** — E11/B₁₁/launcher/turn-witness wired to feeds. *(sourceos-spec/docs/surfaces)*
+6. **Update lifecycle** — E12 OTA + backup generations. *(source-os)*
+
+Each layer is fail-closed and receipted; a layer that can't verify the one below it
+does not come up. This is the buildable spine referenced by the census and E12.
+
+## What remains to a bootable image
+- Package the shell components into the source-os workstation profile (a NixOS/Guix
+  module) + a contract test that the flake evaluates. *(source-os; verified by `nix build`)*
+- E12 update-tree implementation + measured-boot attestation. *(source-os)*
+- Local model serving (E2/E6) for the Noetica concierge. *(agent-machine)*
diff --git a/tools/verify_vendor.py b/tools/verify_vendor.py
new file mode 100644
index 0000000..bef72c6
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+++ b/tools/verify_vendor.py
@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+"""Verify vendored dependency pins.
+
+Validates every vendor/*.lock.json has the required shape, and — when a local
+checkout is available (--checkout <path> or <name> next to this repo) — recomputes
+the deterministic `git archive --format=tar <commit>` sha512 and asserts it matches
+the pinned integrity hash. Vendored deps are consumed, never floating: a pin that
+can't be verified is a failure, not a warning.
+"""
+from __future__ import annotations
+import argparse, hashlib, json, subprocess, sys
+from pathlib import Path
+
+REQUIRED = ["name", "repo", "reason", "pin", "integrity"]
+
+
+def _archive_sha512(checkout: Path, commit: str) -> str:
+    tar = subprocess.run(["git", "-C", str(checkout), "archive", "--format=tar", commit],
+                         check=True, stdout=subprocess.PIPE).stdout
+    return hashlib.sha512(tar).hexdigest()
+
+
+def verify(lock: dict, checkout: Path | None) -> list[str]:
+    errs = [f"missing key {k!r}" for k in REQUIRED if k not in lock]
+    if errs:
+        return errs
+    if checkout and checkout.exists():
+        got = _archive_sha512(checkout, lock["pin"]["commit"])
+        want = lock["integrity"]["git_archive_tar"]
+        if got != want:
+            errs.append(f"integrity mismatch: got {got[:16]}… want {want[:16]}…")
+    return errs
+
+
+def main(argv=None) -> int:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--vendor-dir", type=Path, default=Path(__file__).resolve().parents[1] / "vendor")
+    ap.add_argument("--checkout", type=Path, help="local checkout to recompute the hash against")
+    a = ap.parse_args(argv)
+    locks = sorted(a.vendor_dir.glob("*.lock.json"))
+    if not locks:
+        print("no vendor locks found", file=sys.stderr); return 1
+    bad = 0
+    for lp in locks:
+        lock = json.loads(lp.read_text())
+        errs = verify(lock, a.checkout)
+        if errs:
+            bad += 1; print(f"FAIL {lp.name}: {'; '.join(errs)}")
+        else:
+            hv = " (hash verified)" if a.checkout and a.checkout.exists() else " (shape ok; hash not checked — no checkout)"
+            print(f"OK   {lp.name} → {lock['name']} @ {lock['pin'].get('tag', lock['pin']['commit'][:12])}{hv}")
+    return 1 if bad else 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/vendor/hellgraph.lock.json b/vendor/hellgraph.lock.json
new file mode 100644
index 0000000..30e8bad
--- /dev/null
+++ b/vendor/hellgraph.lock.json
@@ -0,0 +1,22 @@
+{
+  "name": "hellgraph",
+  "repo": "https://github.com/SocioProphet/hellgraph",
+  "reason": "Consumed vendored, not forked: hellgraph is the System Graph substrate that netwatch ingests into and that the B11/E11 surface feeds read. It is not our lane to modify — we pin a release and verify integrity.",
+  "pin": {
+    "tag": "v0.4.45",
+    "commit": "dbe854faf5b8f53a484fd164ba6f84328b5dd24b",
+    "tree": "4161b5f614691e1248a303137ea833a4f9bf97df",
+    "released_on_main": true
+  },
+  "integrity": {
+    "algo": "sha512",
+    "git_archive_tar": "5f892c91e892206fd9b266202c3a4960528211fd593c79e64ea7ffaf8cc9ab5f29ec73bb5c06c09fc26acc866f13bf3ac12375ac8ac7d76f64e6e5d406ff7421",
+    "note": "sha512 of `git archive --format=tar <commit>` — deterministic for the commit; recompute with tools/verify_vendor.py"
+  },
+  "consumers": [
+    "docs/surfaces/data (surface feed producer, build_surface_feed.py)",
+    "TurtleTerm/turtle-netwatch (System Graph ingest)",
+    "sourceos-shell (System Graph consumption)"
+  ],
+  "vendored_at": "2026-08-03"
+}