docs(827): Gate0 Probe-3 no-site §3-review v10 PASS @ce5ba762

Independent Opus SECREV review (ms-secrev-828 lane, dispatched by mosaic-100;
Gate-16 author≠reviewer; byte-only; did not build).
Reviewed object = ce5ba76205
harness sha256 = 7e14ead89a7b2a297fcc17e7653291b3bcace1d2002a8f90a989db74f6985b6f
Verdict PASS: B9 no-site startup closure — launcher -s -S -B (no -I) :515,
broker -I -S -B :554; empirically confirmed site NOT imported (no_site=1) so
system-site .pth/sitecustomize cannot run unpinned startup code; -S leaves
sys.path[0] intact so launcher sibling import + broker explicit --generation-module
import both still bind the pinned helper; delta vs 1c34e3cb = EXACT 2-line -S only
(byte-compared). All priors (B5/B6/B6c/B7/B8/fidelity/traceability/lease_anchor/
live-path/single-broker/--runs/-O-safe) byte-stable. Byte review only; ran nothing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/compaction-refresh/reviews/GATE0-PROBE3-V10-NOSITE-S3-REVIEW-v10.md

@@ -0,0 +1,86 @@
+# Gate0 Probe-3 (D4) No-Site Startup Closure — §3-Conformance Review v10
+
+**Verdict: ✅ PASS**
+
+## Pin (GUARD 1 — reviewed object)
+
+- **Reviewed object = `ce5ba762051354338889959bfce2b0381f4a4e2a`** (harness commit, branch `feat/827-gate0-probe`).
+- **Reviewed file:** `docs/compaction-refresh/probes/p3_d4_focused_run.py` — sha256 (pushed provider bytes, `-o FILE`, FULL-40 ref, verified before trust): `7e14ead89a7b2a297fcc17e7653291b3bcace1d2002a8f90a989db74f6985b6f` (32753 bytes, no not-found sentinel).
+- **Closure pins (unchanged):** launcher `e950e422…` @f4008307 · helper `061625402f08488eac47acd23272904e71fd1a71fd15b3bdab158632c801be4c` @f4008307 · broker `4db4fef1…` @23c0caca.
+
+## Independence (GUARD 2 — principal-independence attestation)
+
+Distinct Opus SECREV session, orchestrator-dispatched — the **`ms-secrev-828` reviewer lane, dispatched by
+`mosaic-100`** — **byte review only, ran nothing** (harness/broker not executed); did **not** build this harness
+(builder = ms-rev-826); is not Mos; distinct principal from both. This re-verifies from scratch on the v10 SHA after
+homelab's 4th-round FAIL @`1c34e3cb` (no `-S` → `site` startup-closure hole) superseded my v9 PASS + Mos's co-attest.
+The `-S`/`-s`/`-I` behavior checks below use a *throwaway* script to observe interpreter startup — not the harness.
+
+## ★ B9 — No-site startup closure (the homelab 4th-round FAIL)
+
+The delta vs `1c34e3cb` is **exactly two `-S` insertions**, byte-confirmed by `diff` (nothing else; +28 B fully
+accounted by the two `        "-S",\n` lines):
+
+- **(i) Launcher command** (`launch_verified_pi`, :512-516): `sys.executable, "-s", "-S", "-B", str(launcher), …` —
+  carries `-s` + **`-S`** + `-B`, and **no `-I`**.
+- **(ii) Broker command** (`launch_verified_broker`, :551-554): `sys.executable, "-I", "-S", "-B", str(broker_path), …`
+  — carries `-I` + **`-S`** + `-B`.
+- **(iii) `site` not imported at child startup** — empirically confirmed (Python 3.11.2, throwaway script):
+  `python3 -s -S -B main.py` → `sys.flags.no_site == 1`, `'site' in sys.modules == False`; `python3 -I -S -B main.py`
+  → `no_site == 1`. So system-site `.pth` executable lines and `sitecustomize`/`usercustomize` **cannot run unpinned
+  startup code** before the pinned launcher/broker. (Contrast without `-S`: `python3 -s -B` → `no_site == 0`, `site`
+  imported — the exact v9 hole this closes.)
+- **(iv)** No harness reliance on any site-injected path/hook (env is the constructed allow-list; children execute
+  pinned bytes).
+- **(v) `-S` does not touch `sys.path[0]`** (unlike `-I`/`-P`) — empirically confirmed: `python3 -s -S -B main.py`
+  keeps `sys.path[0]` = the script's directory, so the launcher's bare `from lease_generation import
+  initialize_runtime_generation` (`f4008307:launch-runtime.py:15`) **still binds `pinned/lease_generation.py`** with
+  `-S` present. The broker's explicit `--generation-module` import (via `importlib`) binds the pinned helper
+  regardless of `sys.path`/site, so `-I -S` is correct there.
+- **(vi) Delta = exact 2-line `-S` only** vs `1c34e3cb` (git-diff/byte-compared, not accepted on assertion).
+
+## All prior bars — byte-stable (delta was only the two `-S` lines)
+
+- **B6(c):** launcher still carries no `-I`; sibling import binds `pinned/` (confirmed above with `-S` present). ✅
+- **B7:** broker `Popen` `env=environment` (allow-list, **not** `os.environ`; no `PYTHONPATH`/`PYTHONHOME`/
+  `PYTHONPYCACHEPREFIX`) + `-I`. ✅
+- **B8:** `reject_pinned_bytecode` fail-closed before each consumer; `PYTHONDONTWRITEBYTECODE=1` + `PYTHONNOUSERSITE=1`
+  in env; `-B` on both children. ✅
+- **B5:** 3-leg conjunction — materialize each of launcher/helper/broker from git-object bytes with `sha256==pin`
+  fail-closed; `pinned/` `0o700` in fixture root, files `O_EXCL 0o600` (no writable window); re-hash `==pin`
+  immediately before each `Popen`; launcher + broker consume the same single pinned helper. ✅
+- **B6:** `closure_import_guard` AST present; single pinned helper; broker `--generation-module = closure.generation`. ✅
+- **Fidelity:** extension bumps `generation-{sid}.state` via `MOSAIC_LEASE_GENERATION_FILE` (not in-mem); broker
+  `read_runtime_generation`; `assert_d4` `generation_source=="state-file"` / `state_file_in_fixture_root` /
+  `new→MUTATOR_UNVERIFIED` / `prior→STALE_GENERATION`; `.state` fixture-root-bound. ✅
+- **Traceability:** `GATED_WI_HEAD == f4008307` + `merge-base --is-ancestor 66b1e0a0 f4008307`. ✅
+- `lease_anchor_registered` + `hex-256` INTACT; LIVE-PATH (pinned gated launcher); single p3 broker;
+  promotion=fixture-only; `--runs choices=(3,)`; `-O`-safe (0 bare `assert`); `copy2` = creds-only; allow-list env
+  (0 `os.environ.copy`). ✅
+
+## ABSENT sweep
+
+P5/P6/P2-bank/retry-launder/mosaic-yolo/execRuntime = 0; `source-invalid` = 0; no live/real-broker path; no `.state`
+outside fixture root; no exec-at-import (`__main__`-guarded); no adjacency-only-exec-from-worktree; the only change is
+the authorized `-S` no-site isolation-deepening (no mechanism change, no scope-widen); `-O`-safe.
+
+## Verdict
+
+**PASS @ `ce5ba762`.** B9 (no-site startup closure) is closed — both children carry `-S`, `site` is not imported at
+startup (so system-site `.pth`/`sitecustomize` cannot execute unpinned code before the pinned launcher/broker),
+`-S` leaves `sys.path[0]` intact so the launcher sibling import and the broker explicit-path import both still bind
+the pinned helper, and the delta vs `1c34e3cb` is exactly the two `-S` insertions. All prior bars (B5/B6/B6c/B7/B8/
+fidelity/traceability/lease_anchor/live-path/single-broker/promotion/`--runs`/`-O`-safe) are byte-stable. Zero
+out-of-scope surface. **Findings: none.**
+
+## Scope reminder (not a finding)
+
+Producing this evidence **executes** the Gate0 mechanism (§3/§5). This review clears **bytes** only; **FIRE remains
+separately gated on Mos's explicit post-clear GO**, his byte-scope-verify co-attestation, and homelab's
+third-principal verify — not authorized by this review.
+
+---
+
+**Reviewer:** distinct Opus SECREV session (`ms-secrev-828` lane, dispatched by `mosaic-100`), Gate-16 author≠reviewer,
+byte review only; ran nothing.
+**Reviewed object (pin):** `ce5ba762051354338889959bfce2b0381f4a4e2a` · harness sha256 `7e14ead89a7b2a297fcc17e7653291b3bcace1d2002a8f90a989db74f6985b6f`.