diff --git a/api/tests/integration/conftest.py b/api/tests/integration/conftest.py
index 81cb26d..6c067f5 100644
--- a/api/tests/integration/conftest.py
+++ b/api/tests/integration/conftest.py
@@ -13,8 +13,15 @@ from src.main import app
 
             
 @pytest.fixture
-def client():
+def db_session():
+    """Сессия БД теста: её же использует client, всё откатывается в конце теста."""
     db_ref = SessionLocal()
+    yield db_ref
+
+
+@pytest.fixture
+def client(db_session):
+    db_ref = db_session
     loop_ref = None
 
     async def _get_db():
diff --git a/api/tests/integration/test_heavy_get_json.py b/api/tests/integration/test_heavy_get_json.py
new file mode 100644
index 0000000..6b16a28
--- /dev/null
+++ b/api/tests/integration/test_heavy_get_json.py
@@ -0,0 +1,66 @@
+"""AURORA-1848: тяжёлые GET отдают готовый JSON из Postgres.
+
+Эталон — старый путь (методы репозиториев и сервисов, которыми пользуется выгрузка Excel)
+в той же сессии теста. Спека: openspec/changes/aurora-1848-sheet-json/specs/sheet-read-api/spec.md
+"""
+from types import SimpleNamespace
+
+import pytest
+
+from src.main import app
+
+ADMIN = SimpleNamespace(id=1, role_id=1)  # fixture.sql: admin
+ISP = SimpleNamespace(id=2, role_id=2)    # fixture.sql: isp1, EXECUTOR_DFIP
+YEAR = 2026
+
+HEAVY_GET_PATHS = [
+    "/api/v1/form/{form_id}/sheet/{sheet}",
+    "/api/v1/svod/1/{sheet}/{year}",
+    "/api/v1/svod/2/{sheet}/{year}",
+    "/api/v1/projects/{project_id}/report/{year}/{report_type}",
+    "/api/v1/rf-rollup/{branch_id}/{year}",
+    "/api/v1/projects/{project_id}/summary",
+    "/api/v1/projects/plan-summary",
+    "/api/v1/projects/fact-summary",
+    "/api/v1/projects/detail-summary",
+]
+OPENAPI_REF = "#/components/schemas/BaseListResponse_SheetResponse_"
+
+
+def _payload(rows) -> list[dict]:
+    """Строки старого пути в том виде, в каком их отдавал BaseListResponse[SheetResponse]."""
+    return [{"row_type": r[0], "depth": r[1], "sort_order": r[2], "data": r[3]} for r in rows]
+
+
+def old_rows(client, coro_factory) -> list[dict]:
+    """Вызвать старый метод (coro_factory() -> awaitable list[tuple]) в цикле приложения."""
+    async def _go():
+        return _payload(await coro_factory())
+
+    return client.portal.call(_go)
+
+
+def expected_sheet(rows: list[dict]) -> list[dict]:
+    """Ожидаемый ответ листа и сводов по эталону старого пути. Фаза B (Task 13) меняет тело на strip_nulls."""
+    return rows
+
+
+def get_ok(client, url, headers, params=None) -> list[dict]:
+    r = client.get(url, headers=headers, params=params)
+    assert r.status_code == 200, r.text
+    assert r.headers["content-type"] == "application/json"
+    assert float(r.headers["x-db-time-ms"]) >= 0
+    body = r.json()
+    assert list(body) == ["success", "message", "result", "count"]
+    assert body["success"] is True and body["message"] is None
+    assert body["count"] == len(body["result"])
+    for row in body["result"]:
+        assert row.keys() == {"row_type", "depth", "sort_order", "data"}
+    return body["result"]
+
+
+def test_openapi_heavy_get_schema_unchanged():
+    spec = app.openapi()
+    for path in HEAVY_GET_PATHS:
+        schema = spec["paths"][path]["get"]["responses"]["200"]["content"]["application/json"]["schema"]
+        assert schema == {"$ref": OPENAPI_REF}, path