Reject malformed persisted settlement header evidence

Preserve safe shared error envelopes and read-only legacy defaults. Add exact/latest evidence-integrity regressions for service, gateway and MCP consumers.

tests/test_comprehensive_settlement.py

@@ -610,3 +610,78 @@ def test_saved_evidence_privacy_contract_filters_keys_not_allowlisted_scalar_val
     contract = (Path(__file__).resolve().parents[1] / "docs/interface-contract.md").read_text()
     assert "allowlisted scalar values are preserved" in contract
     assert "not a content-based secret redactor" in contract
+
+
+@pytest.mark.parametrize("field", ["excluded_evidence", "carried_evidence", "applied_evidence"])
+@pytest.mark.parametrize("corrupt", ["malformed_json", "wrong_json_object"])
+@pytest.mark.parametrize("lookup", ["exact", "latest"])
+def test_saved_reader_rejects_corrupt_header_evidence_without_writes(tmp_path, monkeypatch, field, corrupt, lookup):
+    path = dbfile(tmp_path)
+    saved = ok(close_draft(path, new_draft(path)))
+    marker = "SYNTHETIC_CORRUPT_EVIDENCE_MARKER"
+    payload = "{" + marker if corrupt == "malformed_json" else json.dumps({"private": marker})
+    with sqlite3.connect(path) as conn:
+        columns = {row[1] for row in conn.execute("PRAGMA table_info(asset_snapshot_runs)")}
+        assert field in columns, f"required settlement evidence column missing: {field}"
+        conn.execute(f"UPDATE asset_snapshot_runs SET {field}=? WHERE id=?", (payload, saved["run_id"]))
+        conn.commit()
+        before = list(conn.iterdump())
+
+    query = {"run_id": saved["run_id"]} if lookup == "exact" else {"month": "2026-09"}
+    result = service.get_monthly_settlement_snapshot(db_path=path, **query)
+    expected = {"success": False, "error_code": "data_integrity_error", "error": "snapshot evidence is malformed", "snapshot_run_id": saved["run_id"]}
+    assert result == expected
+    from jarca_ledger_mcp.adapters.streamlit import settlement_gateway
+    gateway = settlement_gateway.get_monthly_settlement_snapshot(db_path=path, **query)
+    assert gateway == result
+    from jarca_ledger_mcp.adapters.mcp import server
+    monkeypatch.setenv("JARCA_LEDGER_DB_PATH", path)
+    tool = server.mcp._tool_manager._tools["get_monthly_settlement_snapshot"]
+    assert tool.fn(**query) == result
+    assert service.get_asset_snapshot_report("2026-09-30", db_path=path) == expected
+    assert marker not in json.dumps(result)
+    assert not ({"run_id", "totals", "income_total", "source_snapshot", "cashflow_items", "excluded_items", "carried_items", "applied_evidence"} & result.keys())
+    with sqlite3.connect(path) as conn:
+        assert list(conn.iterdump()) == before
+
+
+@pytest.mark.parametrize("field", ["excluded_evidence", "carried_evidence", "applied_evidence"])
+def test_saved_reader_accepts_empty_header_evidence_without_changing_legacy_api_shapes(tmp_path, field):
+    path = dbfile(tmp_path)
+    saved = ok(close_draft(path, new_draft(path)))
+    with sqlite3.connect(path) as conn:
+        columns = {row[1] for row in conn.execute("PRAGMA table_info(asset_snapshot_runs)")}
+        assert field in columns, f"required settlement evidence column missing: {field}"
+        conn.execute(f"UPDATE asset_snapshot_runs SET {field}='[]' WHERE id=?", (saved["run_id"],))
+        conn.commit()
+    with sqlite3.connect(path) as conn:
+        before = list(conn.iterdump())
+    exact = ok(service.get_monthly_settlement_snapshot(run_id=saved["run_id"], db_path=path))
+    latest = ok(service.get_monthly_settlement_snapshot(month="2026-09", db_path=path))
+    assert exact == latest
+    public_field = {"excluded_evidence": "excluded_items", "carried_evidence": "carried_items", "applied_evidence": "applied_evidence"}[field]
+    assert exact[public_field] == []
+    assert exact["source"] == "settlement_snapshot" and exact["is_comprehensive"] is True
+    cashflow = ok(service.get_monthly_cashflow_report("2026-09", db_path=path))
+    assert "run_id" not in cashflow and "totals" not in cashflow and "cashflow_items" not in cashflow
+    with sqlite3.connect(path) as conn:
+        assert list(conn.iterdump()) == before
+
+
+def test_schema_eleven_legacy_reader_returns_empty_evidence_without_writes(tmp_path):
+    from test_legacy_snapshot_migration import _legacy_closed_db
+    path, _ = _legacy_closed_db(tmp_path)
+    with sqlite3.connect(path) as conn:
+        assert conn.execute("SELECT COUNT(*) FROM asset_snapshot_runs").fetchone()[0] == 0
+        before = list(conn.iterdump())
+    exact = ok(service.get_monthly_settlement_snapshot(run_id="legacy-run-correction", db_path=path))
+    latest = ok(service.get_monthly_settlement_snapshot(month="2026-06", db_path=path))
+    # Headerless legacy correction metadata already differs by lookup mode;
+    # this rework preserves that separate existing behavior rather than changing it.
+    for result in (exact, latest):
+        assert result["legacy"] is True and result["is_comprehensive"] is False
+        assert result["source_snapshot"] == {}
+        assert result["excluded_items"] == [] and result["carried_items"] == [] and result["applied_evidence"] == []
+        assert all(value is None for value in result["totals"].values())
+    with sqlite3.connect(path) as conn:
+        assert list(conn.iterdump()) == before