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+# GATE0 Probe-3 (#827) — Mos byte-scope-verify CO-ATTESTATION (v7 full-closure)
+
+**Principal:** Mos (orchestrator, merge authority for the mosaic-stack governance lane).
+**Committed under a DISTINCT git identity** (`mos-orchestrator@mosaic.local`) — deliberately NOT the
+`ms-lead-reviewer@mosaic.local` lane signer that authored both the harness and the §3 review — so this
+record stands as a *distinct-identity* co-attestation. See "Independence" below.
+
+**Verify class:** independent provider-byte read (guarded `git show <full-40>:path | sha256sum`) plus
+source-level inspection of the executed mechanism. Not a re-build, not a re-run. This SUPERSEDES the v6
+co-attestation `12914d8` (and its SUPERSEDED-note `b6bd0cd`), which was byte-clear on the v6 bar only
+and was overtaken by homelab's third-principal FAIL @2d54a9dd + the resulting stricter full-closure bar.
+
+## Package under attestation
+
+| Artifact | Ref |
+|---|---|
+| Branch | `feat/827-gate0-probe` |
+| Harness commit-40 | `f609a44953f5ae61916805fcb45ca337de00b0b0` |
+| Harness `p3_d4_focused_run.py` sha256 | `0f1bd1b39399b32f243d901230e2d840794a2144edd723a095dab716833a7a9b` (32071 B) |
+| §3-review-v7 commit-40 | `2bba933f67c821899d320a938a9473a73a136422` (adds only the review `.md`; harness parent byte-stable) |
+| Review path | `docs/compaction-refresh/reviews/GATE0-PROBE3-V7-FULLCLOSURE-S3-REVIEW-v7.md` |
+
+**Pinned closure (all 3 sha256 INDEPENDENTLY recomputed by Mos from git objects == pins):**
+
+| Member | Source (commit:path) | Pin sha256 | Size |
+|---|---|---|---|
+| launcher `launch-runtime.py` | `f4008307:packages/mosaic/framework/tools/lease-broker/launch-runtime.py` | `e950e422…` | 4237 B |
+| helper `lease_generation.py` | `f4008307:packages/mosaic/framework/tools/lease-broker/lease_generation.py` | `061625402f…` | 3769 B |
+| broker `p3_generation_broker.py` | `23c0caca:docs/compaction-refresh/probes/p3_generation_broker.py` | `4db4fef1…` | — |
+
+> Note: `f4008307` (the held WI-3 #830 gated head) is **not on origin** — it exists only as a local
+> `git worktree` on the build host. Mos recomputed the launcher+helper pins from that worktree
+> (`stack-cr-wi3-revoke`, HEAD == `f4008307`) rather than passing over a clone-completeness gap. The
+> broker pin was recomputed from origin `23c0caca`.
+
+## Findings — VERDICT: byte-scope + mechanism + hygiene **PASS** (v7 full-closure bar)
+
+Homelab's stricter bar — **hashed==executed on the FULL executed closure (launcher + helper + broker)**
+— is met. Verified at the source, not accepted on the review's assertion:
+
+**B5 conjunction (the load-bearing repair) — HELD, all three legs:**
+- **(a) materialized from pinned git-object bytes, NOT the mutable worktree.** `materialize_closure`
+  fetches each member via `git_object_bytes` (`git show {commit}:{path}`), then
+  `sha256(data) == pin` **fail-closed** (`RuntimeError` on mismatch) before use.
+- **(b) no writable window hash→consume.** `pinned/` is `mkdir(mode=0o700)`; each file is written with
+  `os.open(O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, 0o600)` — `O_EXCL` refuses a pre-planted file. No `chmod`,
+  no `os.rename/replace`, no `symlink`, and nothing re-opens a pinned file for write (grep = 0). The
+  pinned bytes are immutable within the fixture threat model between hash and exec.
+- **(c) re-hash == pin IMMEDIATELY before each exec, no interleaved yield.** Launcher: re-hash then
+  `return PiRpc(command,…)` whose `__init__` **first statement** is `subprocess.Popen(command,…)` —
+  zero IO/yield/reopen between. Broker + helper: both re-hashed then `subprocess.Popen` on the next
+  line. Adjacency-alone-without-materialization (the v6 defect) is **absent** — all three exec from
+  `pinned/`.
+
+**B6 — helper pinned AND bound to the SAME single copy.** The broker receives
+`--generation-module {closure.generation}` (the pinned helper); the launcher runs from `pinned/` so its
+`import lease_generation` resolves to the sibling pinned copy via `sys.path[0]`. `closure_import_guard`
+AST-parses every member and raises on any non-stdlib import other than the allowed `lease_generation`
+— proving the dependency closure is complete and no unpinned module can enter at runtime.
+
+**Closure = exactly 3 files, materialized inside the fixture root** (`root / "pinned"`). No path escapes
+the fixture temp root; no live/default broker; `.state` remains fixture-bound. **R1 owner tripwire NOT
+tripped** — this deepened isolation of an already-authorized touch, it did not widen the touched surface.
+
+**Invariants (all INTACT):** BAR1 `GATED_WI_HEAD == f4008307` and `merge-base --is-ancestor 66b1e0a0
+f4008307` = YES (file-backed `.state` revocation fidelity present); BAR2 `.state` =
+`socket_path.parent / generation-{sid}.state`, `state_file_in_fixture_root` + `generation_source ==
+"state-file"` checks present; BAR3 `lease_anchor_registered` / live-path / fixture-socket isolation
+intact. `-O`-safe (0 bare `assert`); ABSENT-sweep (`yolo`/`execRuntime`/`p3_bank`/`promote_p2`/`retry`)
+= 0; single broker (1 def + 1 call site); `--runs choices=(3,)`; allow-list env (0 `os.environ.copy`);
+the only `shutil.copy2` is the legitimate `.pi/agent` credential copy (settings/auth/fd), **not** a
+launcher/helper/broker copy — the v6 copy-to-fixture concern is gone.
+
+## Independence
+
+- **Substantive principal-independence** of review-v7 is satisfied by an orchestrator-dispatched,
+  builder-distinct Opus SECREV (`ms-secrev-828`, byte-only, non-builder) — that IS the substance of
+  Gate-16.
+- The shared `ms-lead-reviewer` git signer on both the harness (`ms-rev-826` build) and the review
+  commit is **evidentiary, not substantive**. It is resolved by (1) this Mos co-attestation under a
+  **distinct** identity (`mos-orchestrator`), and (2) a homelab third-principal verify under its own
+  distinct identity — three distinct-identity principals of record. Tracked fleet-infra tooling-gap
+  (durable fix = per-lane distinct signers), **not a blocker**.
+
+## Scope of this record — byte-clear, NOT fire-authorization
+
+Producing probe evidence **executes** the Gate0 mechanism; a byte-clear is not a fire-authorization.
+This co-attestation clears the **bytes / scope / mechanism / hygiene on the v7 full-closure bar**. FIRE
+remains gated on: **homelab third-principal re-verify** (under its own distinct identity) + **Mos
+transparency-to-Jason** + **Mos explicit FIRE GO**. Until then: nothing banked, WI-3 #830 held at
+`f4008307` (unmoved), C-hatch armed (if the materialized-closure rig still no-fire / wrong-value /
+assertion-FAIL / isolation-FAIL → possible Case-C → STOP + escalate to Jason).
+
+**Mos verdict: v7 full-closure byte-scope + mechanism + hygiene PASS. Co-attestation of record —
+committed.**