feat(reviewer): require trust-gate proof in empty-queue reports (#198)

Add assess_empty_queue_report to block empty-queue claims without
pr_inventory_trust_gate.status == trusted_empty, reject weak merge-commit
corroboration, extend inventory handoff fields, and wire the gate into
build_final_report and capability-stop terminal validation.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

review_proofs.py

@@ -664,6 +664,8 @@ def build_final_report(checkout_proof, inventory, validation, contamination,
             report_text, review_decision_lock
         )
 
+    empty_queue_report = assess_empty_queue_report(report_text)
+
     contamination_status = contamination.get("status", "unknown")
     checkout_proven = bool(checkout_proof.get("proven"))
     validation_claimable = bool(validation.get("claimable"))
@@ -787,6 +789,11 @@ def build_final_report(checkout_proof, inventory, validation, contamination,
             "reviewer worktree safety proof missing or failed (#233)"
         )
         downgrade_reasons.extend(worktree.get("reasons", []))
+    if empty_queue_report.get("claimed") and not empty_queue_report.get("proven"):
+        downgrade_reasons.append(
+            "empty-queue report missing or failed trust-gate proof (#198)"
+        )
+        downgrade_reasons.extend(empty_queue_report.get("reasons", []))
 
     merge_allowed = (
         identity_eligible
@@ -846,6 +853,12 @@ def build_final_report(checkout_proof, inventory, validation, contamination,
         "unrelated_mutations_avoided": bool(
             worktree.get("unrelated_mutations_avoided")
         ),
+        "empty_queue_trust_gate_proven": (
+            empty_queue_report.get("proven")
+            if empty_queue_report.get("claimed")
+            else True
+        ),
+        "empty_queue_trust_gate_status": empty_queue_report.get("status"),
     }
 
 
@@ -1016,6 +1029,14 @@ HANDOFF_ROLE_FIELDS = {
         ("Repositories checked", ("repositories checked", "repos checked")),
         ("Open PR counts", ("open pr counts", "open pr count",
                             "open prs per repo")),
+        ("PR inventory trust gate", ("pr inventory trust gate",
+                                     "pr_inventory_trust_gate.status",
+                                     "trust gate status")),
+        ("Trust gate reasons", ("trust gate reasons",
+                                "pr_inventory_trust_gate.reason")),
+        ("Trust gate corroborated", ("trust gate corroborated",
+                                     "pr_inventory_trust_gate.corroborated")),
+        ("Inventory profile", ("inventory profile", "inventory mcp profile")),
         ("Selected PR or reason", ("selected pr", "none selected",
                                    "reason none selected")),
         ("Inventory completeness", ("inventory complete", "inventory scoped",
@@ -1399,6 +1420,148 @@ def format_pr_inventory_trust_gate_report(gate: dict) -> list[str]:
     return lines
 
 
+_EMPTY_QUEUE_CLAIM = re.compile(
+    r"\b0 open pr|\bno open pr|\bno eligible pr|\bempty (?:review )?queue|"
+    r"nothing to review|queue cleared|inventory empty|"
+    r"open pr count:\s*0|workflow correctly stops with nothing",
+    re.I,
+)
+
+_WEAK_EMPTY_QUEUE_CORROBORATION = re.compile(
+    r"latest commit.*(?:merge|pr #)|merge of pr #|"
+    r"master latest commit|recent merge proves",
+    re.I,
+)
+
+_TRUST_GATE_STATUS_LINE = re.compile(
+    r"pr_inventory_trust_gate\.status:\s*(\S+)",
+    re.I,
+)
+
+
+def parse_trust_gate_status_from_report(report_text: str | None) -> str | None:
+    """Extract ``pr_inventory_trust_gate.status`` from report text, if present."""
+    match = _TRUST_GATE_STATUS_LINE.search(report_text or "")
+    return match.group(1).strip().lower() if match else None
+
+
+def assess_empty_queue_report(
+    report_text: str | None,
+    *,
+    trust_gate: dict | None = None,
+    task_role: str | None = None,
+    inventory_profile: str | None = None,
+) -> dict:
+    """Issue #198: empty-queue reports must cite the formal trust-gate result.
+
+    Blocks reports that claim an empty queue without
+    ``pr_inventory_trust_gate.status == trusted_empty``, required inventory
+    metadata, or that rely on weak corroboration (e.g. a recent merge commit).
+    """
+    text = report_text or ""
+    lower = text.lower()
+    reasons: list[str] = []
+    missing: list[str] = []
+
+    if not _EMPTY_QUEUE_CLAIM.search(text):
+        return {
+            "claimed": False,
+            "proven": True,
+            "block": False,
+            "status": None,
+            "missing_fields": [],
+            "reasons": [],
+        }
+
+    status = (
+        (trust_gate or {}).get("status")
+        or parse_trust_gate_status_from_report(text)
+    )
+    status_norm = (status or "").strip().lower() or None
+
+    if not status_norm:
+        missing.append("pr_inventory_trust_gate.status")
+        reasons.append(
+            "empty-queue report missing pr_inventory_trust_gate.status; "
+            "fail closed"
+        )
+    elif status_norm != "trusted_empty":
+        reasons.append(
+            f"empty-queue report has trust-gate status '{status_norm}', "
+            "not trusted_empty"
+        )
+
+    has_gate_reasons = (
+        "pr_inventory_trust_gate.reason" in lower
+        or bool((trust_gate or {}).get("reasons"))
+    )
+    if status_norm and status_norm != "trusted_empty" and not has_gate_reasons:
+        missing.append("pr_inventory_trust_gate.reasons")
+
+    if status_norm == "trusted_empty":
+        if "pr_inventory_trust_gate.corroborated" not in lower and (
+            trust_gate or {}
+        ).get("corroborated") is not True:
+            missing.append("pr_inventory_trust_gate.corroborated")
+
+    inventory_markers = (
+        "repository:",
+        "remote:",
+        "owner:",
+        "state filter:",
+        "state_filter:",
+    )
+    if not any(marker in lower for marker in inventory_markers):
+        missing.append("inventory remote/owner/repo/state filter")
+
+    profile_markers = (
+        "mcp profile:",
+        "mcp-profile:",
+        "inventory profile:",
+        "active profile:",
+    )
+    has_profile = (
+        any(marker in lower for marker in profile_markers)
+        or bool((inventory_profile or "").strip())
+    )
+    if not has_profile:
+        missing.append("inventory MCP profile")
+
+    if _WEAK_EMPTY_QUEUE_CORROBORATION.search(text):
+        if "pr_inventory_trust_gate.status: trusted_empty" not in lower:
+            reasons.append(
+                "weak corroboration (recent merge commit) cannot substitute "
+                "for pr_inventory_trust_gate.status == trusted_empty"
+            )
+
+    role = (task_role or "").strip().lower()
+    if role == "author" and re.search(
+        r"reviewer queue|nothing to review|review backlog empty",
+        text,
+        re.I,
+    ):
+        reasons.append(
+            "author-bound session presented reviewer queue inventory as a "
+            "reviewer decision"
+        )
+
+    if missing:
+        reasons.extend(
+            f"empty-queue report missing required field: {field}"
+            for field in missing
+        )
+
+    proven = not reasons and not missing
+    return {
+        "claimed": True,
+        "proven": proven,
+        "block": not proven,
+        "status": status_norm,
+        "missing_fields": missing,
+        "reasons": reasons,
+    }
+
+
 def assess_duplicate_search_proof(report_text, matches):
     """#207: reject LLM duplicate summaries that omit known title matches."""
     return issue_duplicate_gate.assess_duplicate_search_proof(