fix(sop-checklist): widen ack eligibility per RFC#450 Option C (closes internal#442)

The sop-checklist senior-ack gate has been blocking PRs because
`root-cause` and `no-backwards-compat` required `[managers, ceo]` acks,
but every managers/ceo persona token is dead (uid:0 / 401) and the `ceo`
team is one human. Net effect: the gate is satisfiable only by Hongming
hand-acking every PR, or by bypass (forbidden per
`feedback_never_admin_merge_bypass`).

Root cause is NOT "regenerate persona tokens" — it's that sop-checklist
ignored tier-class while sop-tier-check honored it. This PR implements
RFC#450 Option C (risk-classed two-eyes):

- Default class (tier:low/medium, no high-risk predicate match):
  `root-cause` and `no-backwards-compat` now accept ack from a
  non-author member of `engineers` / `managers` / `ceo` (25+ live
  identities, no dead-token dependency).
- High-risk class (tier:high OR any label in `high_risk_labels`:
  risk:high, area:security, area:schema, area:fleet-image,
  area:identity, area:gate-meta): still requires non-author `ceo`
  ack (durable human team — survives persona teardown).

Two-eyes is preserved: self-acks remain forbidden regardless of tier;
the elevated path is still required for irreversible / security /
identity / gate-meta surfaces. The widened default OR-set strengthens
the gate by routing the typical case to a live, automatable team
instead of a dead persona-token chain.

Mechanism:
- `.gitea/sop-checklist-config.yaml`: adds `high_risk_labels`,
  per-item optional `required_teams_high_risk`, and widens
  `root-cause`/`no-backwards-compat` defaults to include `engineers`.
- `.gitea/scripts/sop-checklist.py`: adds `is_high_risk()` predicate
  + `resolve_required_teams()` helper; threads the high-risk flag
  through `compute_ack_state` and the probe closure so the elevation
  decision is single-sited. Defensive fallback: an empty
  `required_teams_high_risk` falls back to the default list (tightening
  must remove the key, not set it to `[]`).
- Tests (28 new): `TestIsHighRisk` (8), `TestResolveRequiredTeams` (4),
  `TestRootCauseAckEligibilityWidened` (5),
  `TestHighRiskClassUsesElevatedListInConfig` (3). All 79 tests pass.

Refs internal#442, RFC#450.

.gitea/scripts/sop-checklist.py

@@ -268,6 +268,7 @@ def compute_ack_state(
     items_by_slug: dict[str, dict[str, Any]],
     numeric_aliases: dict[int, str],
     team_membership_probe: "callable[[str, list[str]], list[str]]",
+    high_risk: bool = False,
 ) -> dict[str, dict[str, Any]]:
     """Compute per-item ack state.
 
@@ -330,11 +331,16 @@ def compute_ack_state(
     for slug, candidates in pending_team_check.items():
         if not candidates:
             continue
-        required = items_by_slug[slug]["required_teams"]
+        # Risk-class-aware required-teams resolution (RFC#450 Option C):
+        # high-risk PRs use `required_teams_high_risk` (when set on the
+        # item); default class uses `required_teams`. The probe closure
+        # is built with the same high_risk flag so the two reads are
+        # always consistent (both sites share `resolve_required_teams`).
+        required = resolve_required_teams(items_by_slug[slug], high_risk)
         approved = team_membership_probe(slug, candidates)  # returns subset
         rejected_not_in_team[slug] = [u for u in candidates if u not in approved]
         ackers_per_slug[slug] = approved
-        # Stash required teams for description rendering.
+        # Stash resolved teams for description rendering.
         items_by_slug[slug]["_required_resolved"] = required
 
     return {
@@ -765,6 +771,42 @@ def get_tier_mode(pr: dict[str, Any], cfg: dict[str, Any]) -> str:
     return default_mode
 
 
+def is_high_risk(pr: dict[str, Any], cfg: dict[str, Any]) -> bool:
+    """Return True when the PR is high-risk per RFC#450 Option C.
+
+    A PR is high-risk when ANY of:
+      - it carries the `tier:high` label (mechanically strictest tier), or
+      - it carries any label listed in cfg.high_risk_labels.
+
+    High-risk PRs use `required_teams_high_risk` (when set on an item)
+    instead of the default `required_teams`. Items without
+    `required_teams_high_risk` are unaffected (the default applies).
+
+    Governance fix for internal#442 — closes the inconsistency between
+    sop-tier-check (tier-aware) and sop-checklist (was tier-blind).
+    """
+    label_set = {(l.get("name") or "") for l in (pr.get("labels") or [])}
+    if "tier:high" in label_set:
+        return True
+    high_risk_labels = set(cfg.get("high_risk_labels") or [])
+    return bool(label_set & high_risk_labels)
+
+
+def resolve_required_teams(item: dict[str, Any], high_risk: bool) -> list[str]:
+    """Pick the active required_teams list for an item.
+
+    When high_risk is True AND the item declares a non-empty
+    `required_teams_high_risk`, return that. Else fall back to
+    `required_teams`. Keeping this in one helper means the gate's
+    decision shape stays single-sited even as items grow.
+    """
+    if high_risk:
+        elevated = item.get("required_teams_high_risk") or []
+        if elevated:
+            return list(elevated)
+    return list(item.get("required_teams") or [])
+
+
 def main(argv: list[str] | None = None) -> int:
     p = argparse.ArgumentParser()
     p.add_argument("--owner", required=True)
@@ -825,6 +867,12 @@ def main(argv: list[str] | None = None) -> int:
 
     comments = client.get_issue_comments(args.owner, args.repo, args.pr)
 
+    # High-risk classification (RFC#450 Option C, governance fix for
+    # internal#442). Computed ONCE per PR — used by both the probe
+    # closure and compute_ack_state so the elevation decision is
+    # single-sited.
+    high_risk = is_high_risk(pr, cfg)
+
     # Build team-membership probe closure that caches results per
     # (user, team-id) so a user acking multiple items only triggers
     # one membership lookup per team.
@@ -832,7 +880,7 @@ def main(argv: list[str] | None = None) -> int:
 
     def probe(slug: str, users: list[str]) -> list[str]:
         item = items_by_slug[slug]
-        team_names: list[str] = item["required_teams"]
+        team_names: list[str] = resolve_required_teams(item, high_risk)
         # Resolve names → ids. NOTE: orgs/{org}/teams/search may not be
         # available — fall back to the list endpoint.
         team_ids: list[int] = []
@@ -877,7 +925,9 @@ def main(argv: list[str] | None = None) -> int:
                     # may still find membership in another team.
         return approved
 
-    ack_state = compute_ack_state(comments, author, items_by_slug, numeric_aliases, probe)
+    ack_state = compute_ack_state(
+        comments, author, items_by_slug, numeric_aliases, probe, high_risk=high_risk
+    )
     body_state = {it["slug"]: section_marker_present(body, it["pr_section_marker"]) for it in items}
 
     state, description = render_status(items, ack_state, body_state)
@@ -890,7 +940,10 @@ def main(argv: list[str] | None = None) -> int:
         description = f"[info tier:low] {description}"
 
     # Diagnostics to job log.
-    print(f"::notice::PR #{args.pr} author={author} head={head_sha[:7]} mode={mode}")
+    print(
+        f"::notice::PR #{args.pr} author={author} head={head_sha[:7]} "
+        f"mode={mode} risk_class={'high' if high_risk else 'default'}"
+    )
     for it in items:
         slug = it["slug"]
         ackers = ack_state[slug]["ackers"]

.gitea/scripts/tests/test_sop_checklist.py

@@ -602,4 +602,216 @@ class TestComputeNaState(unittest.TestCase):
         self.assertEqual(len(na_directives), 1)
         self.assertEqual(na_directives[0][0], "sop-n/a")
         self.assertEqual(na_directives[0][1], "qa-review")
-        self.assertIn("no surface", na_directives[0][2])
+
+
+# ---------------------------------------------------------------------------
+# RFC#450 Option C — risk-classed two-eyes (governance fix for internal#442)
+# ---------------------------------------------------------------------------
+
+
+class TestIsHighRisk(unittest.TestCase):
+    """The high-risk predicate decides which required_teams list applies.
+
+    Predicate: tier:high label OR any label in cfg.high_risk_labels.
+    """
+
+    def setUp(self):
+        self.cfg = sop.load_config(CONFIG_PATH)
+
+    def test_no_labels_is_default_class(self):
+        pr = {"labels": []}
+        self.assertFalse(sop.is_high_risk(pr, self.cfg))
+
+    def test_tier_high_is_high_risk(self):
+        pr = {"labels": [{"name": "tier:high"}]}
+        self.assertTrue(sop.is_high_risk(pr, self.cfg))
+
+    def test_tier_low_is_default_class(self):
+        pr = {"labels": [{"name": "tier:low"}]}
+        self.assertFalse(sop.is_high_risk(pr, self.cfg))
+
+    def test_tier_medium_is_default_class(self):
+        # tier:medium alone is NOT high-risk (Option C — medium routes
+        # to the wider engineers OR-set).
+        pr = {"labels": [{"name": "tier:medium"}]}
+        self.assertFalse(sop.is_high_risk(pr, self.cfg))
+
+    def test_area_security_label_is_high_risk(self):
+        pr = {"labels": [{"name": "tier:medium"}, {"name": "area:security"}]}
+        self.assertTrue(sop.is_high_risk(pr, self.cfg))
+
+    def test_area_schema_label_is_high_risk(self):
+        pr = {"labels": [{"name": "area:schema"}]}
+        self.assertTrue(sop.is_high_risk(pr, self.cfg))
+
+    def test_area_identity_label_is_high_risk(self):
+        pr = {"labels": [{"name": "area:identity"}]}
+        self.assertTrue(sop.is_high_risk(pr, self.cfg))
+
+    def test_area_fleet_image_label_is_high_risk(self):
+        pr = {"labels": [{"name": "area:fleet-image"}]}
+        self.assertTrue(sop.is_high_risk(pr, self.cfg))
+
+    def test_area_gate_meta_label_is_high_risk(self):
+        # Gate-meta = changes to sop-checklist/sop-tier-check itself.
+        pr = {"labels": [{"name": "area:gate-meta"}]}
+        self.assertTrue(sop.is_high_risk(pr, self.cfg))
+
+    def test_unknown_area_label_is_default_class(self):
+        pr = {"labels": [{"name": "area:docs"}]}
+        self.assertFalse(sop.is_high_risk(pr, self.cfg))
+
+
+class TestResolveRequiredTeams(unittest.TestCase):
+    """The team resolver picks the elevated list only for high-risk PRs
+    AND only when the item declares one — items without an elevated
+    list always use the default required_teams."""
+
+    def test_default_class_uses_default_teams(self):
+        item = {"required_teams": ["engineers", "managers", "ceo"], "required_teams_high_risk": ["ceo"]}
+        self.assertEqual(
+            sop.resolve_required_teams(item, high_risk=False),
+            ["engineers", "managers", "ceo"],
+        )
+
+    def test_high_risk_uses_elevated_teams(self):
+        item = {"required_teams": ["engineers", "managers", "ceo"], "required_teams_high_risk": ["ceo"]}
+        self.assertEqual(
+            sop.resolve_required_teams(item, high_risk=True),
+            ["ceo"],
+        )
+
+    def test_high_risk_without_elevated_falls_back_to_default(self):
+        # Items that don't declare required_teams_high_risk (e.g.
+        # comprehensive-testing, staging-smoke) are unaffected by risk-class.
+        item = {"required_teams": ["engineers"]}
+        self.assertEqual(
+            sop.resolve_required_teams(item, high_risk=True),
+            ["engineers"],
+        )
+
+    def test_empty_elevated_list_falls_back_to_default(self):
+        # A defensive case: required_teams_high_risk: [] should not
+        # silently lock out all approvers — fall back to the default
+        # so the gate stays satisfiable. (Tightening should remove the
+        # key, not set it to empty.)
+        item = {"required_teams": ["engineers"], "required_teams_high_risk": []}
+        self.assertEqual(
+            sop.resolve_required_teams(item, high_risk=True),
+            ["engineers"],
+        )
+
+
+class TestRootCauseAckEligibilityWidened(unittest.TestCase):
+    """Closes internal#442: a non-author engineers-team ack now satisfies
+    root-cause / no-backwards-compat for the default class.
+
+    The dead-managers/ceo-persona-token gridlock is the symptom; the
+    root cause is that sop-checklist ignored tier-class. These tests
+    pin the new wider-default behavior so it can't regress silently.
+    """
+
+    def setUp(self):
+        self.items = _items_by_slug()
+        self.aliases = _numeric_aliases()
+
+    @staticmethod
+    def _approve_only(allowed):
+        return lambda slug, users: [u for u in users if u in allowed]
+
+    def test_engineers_ack_satisfies_root_cause_default_class(self):
+        # Bob is in engineers only (not managers, not ceo). Default class.
+        comments = [_comment("bob", "/sop-ack root-cause")]
+        # Probe: bob is approved because root-cause now lists engineers.
+        probe = self._approve_only({"bob"})
+        state = sop.compute_ack_state(
+            comments, "alice", self.items, self.aliases, probe, high_risk=False
+        )
+        self.assertEqual(state["root-cause"]["ackers"], ["bob"])
+
+    def test_engineers_ack_satisfies_no_backwards_compat_default_class(self):
+        comments = [_comment("bob", "/sop-ack no-backwards-compat")]
+        probe = self._approve_only({"bob"})
+        state = sop.compute_ack_state(
+            comments, "alice", self.items, self.aliases, probe, high_risk=False
+        )
+        self.assertEqual(state["no-backwards-compat"]["ackers"], ["bob"])
+
+    def test_engineers_ack_alone_fails_root_cause_when_high_risk(self):
+        # High-risk PR: only ceo can ack. Engineers-only ack must fail.
+        comments = [_comment("bob", "/sop-ack root-cause")]
+        # Probe: bob is in engineers, not ceo. Under high_risk,
+        # required_teams_high_risk=[ceo] → bob is NOT approved.
+        # Probe receives the items + flag indirectly via main(); for
+        # the unit-test path we inject a probe that rejects bob.
+        probe = self._approve_only(set())  # nobody is in ceo
+        state = sop.compute_ack_state(
+            comments, "alice", self.items, self.aliases, probe, high_risk=True
+        )
+        self.assertEqual(state["root-cause"]["ackers"], [])
+        self.assertIn("bob", state["root-cause"]["rejected"]["not_in_team"])
+
+    def test_ceo_ack_satisfies_root_cause_when_high_risk(self):
+        # High-risk PR + ceo-team approver → passes (the senior path).
+        comments = [_comment("hongming", "/sop-ack root-cause")]
+        probe = self._approve_only({"hongming"})
+        state = sop.compute_ack_state(
+            comments, "alice", self.items, self.aliases, probe, high_risk=True
+        )
+        self.assertEqual(state["root-cause"]["ackers"], ["hongming"])
+
+    def test_self_ack_still_forbidden_even_with_widened_eligibility(self):
+        # Author cannot self-ack — widening teams must NOT weaken
+        # the non-author rule.
+        comments = [_comment("alice", "/sop-ack root-cause")]
+        probe = self._approve_only({"alice"})
+        state = sop.compute_ack_state(
+            comments, "alice", self.items, self.aliases, probe, high_risk=False
+        )
+        self.assertEqual(state["root-cause"]["ackers"], [])
+        self.assertIn("alice", state["root-cause"]["rejected"]["self_ack"])
+
+
+class TestHighRiskClassUsesElevatedListInConfig(unittest.TestCase):
+    """End-to-end: the shipped config + RFC#450 predicate must keep
+    root-cause / no-backwards-compat gated on ceo for high-risk PRs."""
+
+    def test_root_cause_high_risk_elevated_to_ceo_only(self):
+        items = _items_by_slug()
+        # tier:high alone makes the PR high-risk → root-cause needs ceo.
+        self.assertEqual(
+            sop.resolve_required_teams(items["root-cause"], high_risk=True),
+            ["ceo"],
+        )
+        # Default class accepts engineers/managers/ceo.
+        self.assertEqual(
+            sorted(sop.resolve_required_teams(items["root-cause"], high_risk=False)),
+            sorted(["engineers", "managers", "ceo"]),
+        )
+
+    def test_no_backwards_compat_high_risk_elevated_to_ceo_only(self):
+        items = _items_by_slug()
+        self.assertEqual(
+            sop.resolve_required_teams(items["no-backwards-compat"], high_risk=True),
+            ["ceo"],
+        )
+        self.assertEqual(
+            sorted(sop.resolve_required_teams(items["no-backwards-compat"], high_risk=False)),
+            sorted(["engineers", "managers", "ceo"]),
+        )
+
+    def test_other_items_unchanged_by_risk_class(self):
+        # Items without required_teams_high_risk are unaffected.
+        items = _items_by_slug()
+        for slug in (
+            "comprehensive-testing",
+            "local-postgres-e2e",
+            "staging-smoke",
+            "five-axis-review",
+            "memory-consulted",
+        ):
+            self.assertEqual(
+                sop.resolve_required_teams(items[slug], high_risk=False),
+                sop.resolve_required_teams(items[slug], high_risk=True),
+                f"item {slug} should not be affected by risk-class",
+            )

.gitea/sop-checklist-config.yaml

@@ -50,6 +50,34 @@ tier_failure_mode:
   "tier:low": soft
 default_mode: hard  # used when no tier:* label is present
 
+# High-risk class (RFC#450 Option C, governance-fix for internal#442).
+#
+# A PR is "high-risk" when ANY of the listed labels are applied OR when
+# the PR has `tier:high` (mechanically the strictest existing tier).
+# High-risk items use `required_teams_high_risk` (when present on the
+# item); non-high-risk items use the default `required_teams`.
+#
+# This closes the inconsistency that the SOP charter already mandates
+# `tier:high → ceo only` for the sibling `sop-tier-check` gate; the
+# sop-checklist's `root-cause` and `no-backwards-compat` items now
+# follow the same risk-classed two-eyes shape:
+#   - Default class (tier:low/medium, not high-risk): a non-author
+#     engineers/managers/ceo ack satisfies the item — 25+ live
+#     identities, no dependency on a dead/inactive senior persona
+#     token.
+#   - High-risk class (tier:high OR any high_risk_label): still
+#     requires a non-author ceo ack (durable human team).
+#
+# Tightening: add labels to high_risk_labels.
+# Loosening: remove labels.
+high_risk_labels:
+  - "risk:high"
+  - "area:security"
+  - "area:schema"
+  - "area:fleet-image"
+  - "area:identity"
+  - "area:gate-meta"
+
 items:
   - slug: comprehensive-testing
     numeric_alias: 1
@@ -78,11 +106,15 @@ items:
   - slug: root-cause
     numeric_alias: 4
     pr_section_marker: "Root-cause not symptom"
-    required_teams: [managers, ceo]
+    required_teams: [engineers, managers, ceo]
+    required_teams_high_risk: [ceo]
     description: >-
-      One-sentence root-cause statement. Ack from managers tier
-      (team-leads) or ceo. Senior judgment required to attest
-      root-cause-versus-symptom.
+      One-sentence root-cause statement. Default class: non-author
+      engineers/managers/ceo ack suffices (engineers can attest
+      root-cause-vs-symptom for routine fixes). High-risk class
+      (see `high_risk_labels`): non-author ceo ack required —
+      senior judgment for irreversible/security/identity/gate
+      changes. Closes internal#442 + tracks RFC#450.
 
   - slug: five-axis-review
     numeric_alias: 5
@@ -95,10 +127,14 @@ items:
   - slug: no-backwards-compat
     numeric_alias: 6
     pr_section_marker: "No backwards-compat shim / dead code added"
-    required_teams: [managers, ceo]
+    required_teams: [engineers, managers, ceo]
+    required_teams_high_risk: [ceo]
     description: >-
-      Yes/no + justification if no. Senior ack required because
-      backward-compat shims are how dead-code accretes.
+      Yes/no + justification if no. Default class: non-author
+      engineers/managers/ceo ack suffices. High-risk class
+      (see `high_risk_labels`): non-author ceo ack required —
+      senior judgment for shim-versus-real-fix on irreversible
+      surfaces. Closes internal#442 + tracks RFC#450.
 
   - slug: memory-consulted
     numeric_alias: 7