diff --git a/api/src/schemas/consolidations.py b/api/src/schemas/consolidations.py
index c235249..3d7eb37 100644
--- a/api/src/schemas/consolidations.py
+++ b/api/src/schemas/consolidations.py
@@ -42,12 +42,18 @@ class RefOut(BaseModel):
 
 
 class ConsolidationCreate(BaseModel):
-    """Тело `POST /consolidations`: ГК, ГСК периметра, период."""
+    """Тело `POST /consolidations`: ГК, ГСК, период и необязательный выбранный периметр (модалка [42],
+    front-api-gaps D-1).
+
+    `legal_entity_ids` нет или `null` — периметр из текущих членов ГСК; список — ровно эти ЮЛ ГК (дубли схлопывает
+    сервис).
+    """
 
     company_group_id: uuid.UUID
     related_group_id: uuid.UUID
     year: int = Field(ge=YEAR_MIN, le=YEAR_MAX)
     quarter: PeriodQuarter
+    legal_entity_ids: list[uuid.UUID] | None = Field(default=None, max_length=MAX_MEMBERS)
 
 
 class LockOut(BaseModel):
diff --git a/api/src/services/consolidations.py b/api/src/services/consolidations.py
index 01e54aa..72846c0 100644
--- a/api/src/services/consolidations.py
+++ b/api/src/services/consolidations.py
@@ -3,13 +3,14 @@
 audit-trail `CONSOLIDATION_CREATE`; design D-15, D-16).
 
 Порядок операции: право (`require` на маршруте) → видимость (ГК/версия — через ГК, невидимое = несуществующее, 404
-с тем же телом) → проверки → запись. Перимeтр версии при создании — текущие члены ГСК, `is_head_entity = false`;
-ГСК в `consolidation.related_group_id` не сохраняется (фиксируется при верификации, Срез 7). Блокировка на создателя
-не ставится. Параллельное создание того же периода ловит UNIQUE `uq_consolidation_group_year_quarter` →
-`IntegrityError` → 409 `CONSOLIDATION_EXISTS` (`common/constraint_conflicts.py`).
+с тем же телом) → проверки → запись. Перимeтр версии при создании — текущие члены ГСК или выбранные ЮЛ ГК
+(`legal_entity_ids`, front-api-gaps D-1), `is_head_entity = false`; ГСК в `consolidation.related_group_id` не
+сохраняется (фиксируется при верификации, Срез 7). Блокировка на создателя не ставится. Параллельное создание того
+же периода ловит UNIQUE `uq_consolidation_group_year_quarter` → `IntegrityError` → 409 `CONSOLIDATION_EXISTS` (`common/constraint_conflicts.py`).
 """
 
 import uuid
+from collections.abc import Sequence
 
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -87,11 +88,13 @@ class ConsolidationService:
         self._principal = principal
 
     async def create(self, data: ConsolidationCreate) -> VersionCard:
-        """Консолидация ГК за период с версией №1 (`INITIATED`), периметром из ГСК, историей и аудитом.
+        """Консолидация ГК за период с версией №1 (`INITIATED`), периметром (ГСК или выбранные ЮЛ), историей и аудитом.
 
         Проверки по порядку: ГК видима (404) → ГСК видима (404), принадлежит ГК и `kind = gsk` (422
-        `RELATED_GROUP_MISMATCH`) → в ГСК не меньше двух текущих членов (422 `PERIMETER_TOO_SMALL`) → периода ещё нет
-        (409 `CONSOLIDATION_EXISTS`; гонку закрывает UNIQUE). Всё — в транзакции запроса: любая ошибка откатывает всё.
+        `RELATED_GROUP_MISMATCH`) → периметр: без `legal_entity_ids` — текущие члены ГСК, не меньше двух (422
+        `PERIMETER_TOO_SMALL`); со списком — `_validate_perimeter` (422 `ENTITY_NOT_IN_GROUP` / `PERIMETER_TOO_SMALL`) →
+        периода ещё нет (409 `CONSOLIDATION_EXISTS`; гонку закрывает UNIQUE). Всё — в транзакции запроса: любая ошибка
+        откатывает всё.
         После проверки ГК берётся advisory-блокировка привязок ГК (R-2): подхват документов (`bind_confirmed`) не
         разминётся с параллельным подтверждением или автозаменой документа ЮЛ этой ГК.
         """
@@ -106,15 +109,18 @@ class ConsolidationService:
             raise NotFoundError(RELATED_GROUP_NOT_FOUND)
         if related.kind != RelatedGroupKind.gsk or related.company_group_id != group.id:
             raise DomainValidationError("RELATED_GROUP_MISMATCH", "ГСК должна принадлежать выбранной ГК")
-        entities = [entity for _, entity in await directories_repo.current_members(self._session, related.id)]
-        if len(entities) < MIN_PERIMETER:
-            raise DomainValidationError(
-                "PERIMETER_TOO_SMALL", f"В ГСК должно быть не меньше {MIN_PERIMETER} ЮЛ, сейчас {len(entities)}"
-            )
+        if data.legal_entity_ids is None:
+            entity_ids = [entity.id for _, entity in await directories_repo.current_members(self._session, related.id)]
+            if len(entity_ids) < MIN_PERIMETER:
+                raise DomainValidationError(
+                    "PERIMETER_TOO_SMALL", f"В ГСК должно быть не меньше {MIN_PERIMETER} ЮЛ, сейчас {len(entity_ids)}"
+                )
+        else:
+            entity_ids = await self._validate_perimeter(group.id, data.legal_entity_ids)
         if await repo.get_consolidation_for_group(self._session, self._scope, group.id, data.year, data.quarter):
             raise ConflictError("CONSOLIDATION_EXISTS", "Консолидация ГК за этот период уже создана")
 
-        consolidation, version = await self._insert(group.id, data, entities)
+        consolidation, version = await self._insert(group.id, data, entity_ids)
         await self._audit.record(
             action=AuditAction.CONSOLIDATION_CREATE,
             section=AuditSection.CONSOLIDATION,
@@ -125,7 +131,7 @@ class ConsolidationService:
                 "consolidation_id": consolidation.id,
                 "year": consolidation.year,
                 "quarter": consolidation.quarter,
-                "members": sorted(entity.id for entity in entities),
+                "members": sorted(entity_ids),
             },
         )
         return await self._card(version, consolidation)
@@ -247,17 +253,7 @@ class ConsolidationService:
         """
         user = self._principal.user
         version, consolidation = await lock_editable_version(self._session, self._scope, version_id, user.id)
-        requested = list(dict.fromkeys(data.legal_entity_ids))
-        valid = await repo.entities_in_group(self._session, consolidation.company_group_id, requested)
-        foreign = [entity_id for entity_id in requested if entity_id not in valid]
-        if foreign:
-            raise DomainValidationError(
-                "ENTITY_NOT_IN_GROUP", "ЮЛ не принадлежат ГК консолидации", legal_entity_ids=foreign
-            )
-        if len(requested) < MIN_PERIMETER:
-            raise DomainValidationError(
-                "PERIMETER_TOO_SMALL", f"В периметре должно быть не меньше {MIN_PERIMETER} ЮЛ, сейчас {len(requested)}"
-            )
+        requested = await self._validate_perimeter(consolidation.company_group_id, data.legal_entity_ids)
 
         current = {member.legal_entity_id: member for member, _ in await repo.members(self._session, version.id)}
         added = [entity_id for entity_id in requested if entity_id not in current]
@@ -291,8 +287,27 @@ class ConsolidationService:
         )
         return await self._card(version, consolidation)
 
+    async def _validate_perimeter(
+        self, company_group_id: uuid.UUID, entity_ids: Sequence[uuid.UUID]
+    ) -> list[uuid.UUID]:
+        """Периметр консолидации — одно правило для создания и `PUT …/members` (front-api-gaps D-1): дубли схлопываются
+        в порядке первого вхождения → все ЮЛ существуют и принадлежат ГК (422 `ENTITY_NOT_IN_GROUP`, `legal_entity_ids`
+        — чужие в порядке запроса) → не меньше двух (422 `PERIMETER_TOO_SMALL`)."""
+        requested = list(dict.fromkeys(entity_ids))
+        valid = await repo.entities_in_group(self._session, company_group_id, requested)
+        foreign = [entity_id for entity_id in requested if entity_id not in valid]
+        if foreign:
+            raise DomainValidationError(
+                "ENTITY_NOT_IN_GROUP", "ЮЛ не принадлежат ГК консолидации", legal_entity_ids=foreign
+            )
+        if len(requested) < MIN_PERIMETER:
+            raise DomainValidationError(
+                "PERIMETER_TOO_SMALL", f"В периметре должно быть не меньше {MIN_PERIMETER} ЮЛ, сейчас {len(requested)}"
+            )
+        return requested
+
     async def _insert(
-        self, group_id: uuid.UUID, data: ConsolidationCreate, entities: list[LegalEntity]
+        self, group_id: uuid.UUID, data: ConsolidationCreate, entity_ids: list[uuid.UUID]
     ) -> tuple[Consolidation, ConsolidationVersion]:
         """Записывает консолидацию, версию №1, периметр и первую запись истории; подхватывает документы."""
         now = utc_now()
@@ -322,8 +337,8 @@ class ConsolidationService:
         self._session.add(version)
         await self._session.flush()
         self._session.add_all(
-            ConsolidationMember(consolidation_version_id=version.id, legal_entity_id=entity.id, is_head_entity=False)
-            for entity in entities
+            ConsolidationMember(consolidation_version_id=version.id, legal_entity_id=entity_id, is_head_entity=False)
+            for entity_id in entity_ids
         )
         self._session.add(
             ConsolidationStatusHistory(
@@ -336,7 +351,7 @@ class ConsolidationService:
         )
         await self._session.flush()
         await consolidation_documents.bind_confirmed(
-            self._session, version=version, consolidation=consolidation, entity_ids=[entity.id for entity in entities]
+            self._session, version=version, consolidation=consolidation, entity_ids=entity_ids
         )
         return consolidation, version
 
diff --git a/api/tests/test_api_consolidations.py b/api/tests/test_api_consolidations.py
index 8bc64f6..7d8c7f5 100644
--- a/api/tests/test_api_consolidations.py
+++ b/api/tests/test_api_consolidations.py
@@ -3,6 +3,7 @@
 `CONSOLIDATION_CREATE`; design D-15, D-16)."""
 
 import uuid
+from collections.abc import Sequence
 from typing import Any
 
 import pytest
@@ -18,7 +19,7 @@ from src.models.consolidation import (
     ConsolidationStatusHistory,
     ConsolidationVersion,
 )
-from src.models.directories import CompanyGroup, LegalEntity, RegionalOffice, RelatedGroup
+from src.models.directories import CompanyGroup, LegalEntity, RegionalOffice, RelatedGroup, RelatedGroupMember
 from src.models.enums import AuditAction, AuditSection, ConsolidationStatus, PeriodQuarter, RelatedGroupKind
 from tests.conftest import AuthClientFactory
 from tests.factories import (
@@ -73,6 +74,18 @@ def _body(group: CompanyGroup, gsk: RelatedGroup, year: int = 2024, quarter: str
     return {"company_group_id": str(group.id), "related_group_id": str(gsk.id), "year": year, "quarter": quarter}
 
 
+def _with_ids(body: dict[str, Any], ids: Sequence[uuid.UUID | str]) -> dict[str, Any]:
+    """Тело создания с явным периметром (модалка [42], front-api-gaps D-1)."""
+    return {**body, "legal_entity_ids": [str(entity_id) for entity_id in ids]}
+
+
+async def _gsk_members(session: AsyncSession, gsk: RelatedGroup) -> set[uuid.UUID]:
+    stmt = select(RelatedGroupMember.legal_entity_id).where(
+        RelatedGroupMember.related_group_id == gsk.id, RelatedGroupMember.is_current.is_(True)
+    )
+    return set((await session.execute(stmt)).scalars())
+
+
 async def _count(session: AsyncSession, model: type) -> int:
     return (await session.execute(select(func.count()).select_from(model))).scalar_one()
 
@@ -175,6 +188,149 @@ async def test_create_ignores_closed_memberships(auth_client: AuthClientFactory,
     assert "ООО Бывший" not in [member["name"] for member in response.json()["members"]]
 
 
+@pytest.mark.integration
+async def test_create_with_selected_perimeter_wider_than_gsk(
+    auth_client: AuthClientFactory, seeded: AsyncSession
+) -> None:
+    """Выбранный периметр шире ГСК: ровно эти ЮЛ, одно событие создания, состав ГСК не меняется."""
+    group, gsk, entities = await _scenario(seeded)
+    outsider = await make_legal_entity(seeded, name="ООО Вне ГСК", group=group)
+    selected = [*entities, outsider]
+    client = await auth_client(KA_RF)
+
+    response = await client.post(CONSOLIDATIONS, json=_with_ids(_body(group, gsk), [e.id for e in selected]))
+
+    assert response.status_code == HTTP_CREATED, response.text
+    assert {member["id"] for member in response.json()["members"]} == {str(e.id) for e in selected}
+    event = (
+        await seeded.execute(select(AuditEvent).where(AuditEvent.action == AuditAction.CONSOLIDATION_CREATE))
+    ).scalar_one()
+    assert event.after_value is not None
+    assert event.after_value["members"] == sorted(str(e.id) for e in selected)
+    membership = select(func.count()).select_from(AuditEvent).where(AuditEvent.action == AuditAction.MEMBERSHIP_CHANGE)
+    assert (await seeded.execute(membership)).scalar_one() == 0
+    assert await _gsk_members(seeded, gsk) == {e.id for e in entities}
+    assert await _count(seeded, ConsolidationLock) == 0
+
+
+@pytest.mark.integration
+async def test_create_gsk_of_one_with_second_entity_selected(
+    auth_client: AuthClientFactory, seeded: AsyncSession
+) -> None:
+    """ГСК из одного ЮЛ, второе отмечено вручную — периметр из двух (проверка размера — по выбранным)."""
+    group, gsk, (single,) = await _scenario(seeded, members=1)
+    second = await make_legal_entity(seeded, name="ООО Второе", group=group)
+    client = await auth_client(KA_RF)
+
+    response = await client.post(CONSOLIDATIONS, json=_with_ids(_body(group, gsk), [single.id, second.id]))
+
+    assert response.status_code == HTTP_CREATED, response.text
+    assert {member["id"] for member in response.json()["members"]} == {str(single.id), str(second.id)}
+
+
+@pytest.mark.integration
+async def test_create_with_entity_of_other_group_is_rejected(
+    auth_client: AuthClientFactory, seeded: AsyncSession
+) -> None:
+    group, gsk, entities = await _scenario(seeded)
+    other_group = await make_company_group(seeded, name="ГК Соседняя", office=await _office(seeded, ROSTOV))
+    stranger = await make_legal_entity(seeded, name="ООО Чужое", group=other_group)
+    client = await auth_client(KA_RF)
+
+    body = _with_ids(_body(group, gsk), [*[e.id for e in entities], stranger.id])
+    response = await client.post(CONSOLIDATIONS, json=body)
+
+    assert response.status_code == HTTP_UNPROCESSABLE, response.text
+    detail = response.json()["detail"]
+    assert detail["code"] == "ENTITY_NOT_IN_GROUP"
+    assert detail["legal_entity_ids"] == [str(stranger.id)]
+    assert await _count(seeded, Consolidation) == 0
+
+
+@pytest.mark.integration
+async def test_create_with_unknown_entity_is_not_in_group(auth_client: AuthClientFactory, seeded: AsyncSession) -> None:
+    group, gsk, entities = await _scenario(seeded)
+    ghost = uuid.uuid4()
+    client = await auth_client(KA_RF)
+
+    response = await client.post(CONSOLIDATIONS, json=_with_ids(_body(group, gsk), [*[e.id for e in entities], ghost]))
+
+    assert response.status_code == HTTP_UNPROCESSABLE, response.text
+    assert response.json()["detail"]["code"] == "ENTITY_NOT_IN_GROUP"
+    assert response.json()["detail"]["legal_entity_ids"] == [str(ghost)]
+
+
+@pytest.mark.integration
+async def test_create_with_duplicates_collapsing_to_one_is_too_small(
+    auth_client: AuthClientFactory, seeded: AsyncSession
+) -> None:
+    group, gsk, entities = await _scenario(seeded)
+    client = await auth_client(KA_RF)
+
+    response = await client.post(CONSOLIDATIONS, json=_with_ids(_body(group, gsk), [entities[0].id, entities[0].id]))
+
+    assert response.status_code == HTTP_UNPROCESSABLE, response.text
+    assert response.json()["detail"]["code"] == "PERIMETER_TOO_SMALL"
+    assert await _count(seeded, Consolidation) == 0
+
+
+@pytest.mark.integration
+async def test_create_with_empty_selected_perimeter_is_too_small(
+    auth_client: AuthClientFactory, seeded: AsyncSession
+) -> None:
+    """Review Focus: `[]` — явный пустой периметр, а не «поле не передано» (ГСК из двух не подставляется)."""
+    group, gsk, _ = await _scenario(seeded)
+    client = await auth_client(KA_RF)
+
+    response = await client.post(CONSOLIDATIONS, json=_with_ids(_body(group, gsk), []))
+
+    assert response.status_code == HTTP_UNPROCESSABLE, response.text
+    assert response.json()["detail"]["code"] == "PERIMETER_TOO_SMALL"
+
+
+@pytest.mark.integration
+async def test_create_with_null_selected_perimeter_takes_gsk(
+    auth_client: AuthClientFactory, seeded: AsyncSession
+) -> None:
+    """Решение №3: `legal_entity_ids: null` равнозначно отсутствию поля."""
+    group, gsk, entities = await _scenario(seeded)
+    client = await auth_client(KA_RF)
+
+    response = await client.post(CONSOLIDATIONS, json={**_body(group, gsk), "legal_entity_ids": None})
+
+    assert response.status_code == HTTP_CREATED, response.text
+    assert {member["id"] for member in response.json()["members"]} == {str(e.id) for e in entities}
+
+
+@pytest.mark.integration
+async def test_create_gsk_mismatch_reported_before_perimeter(
+    auth_client: AuthClientFactory, seeded: AsyncSession
+) -> None:
+    """Порядок проверок (решение №5): ГСК раньше периметра."""
+    group, _, _ = await _scenario(seeded)
+    gsz = await make_related_group(seeded, group=group, kind=RelatedGroupKind.gsz, name="ГСЗ")
+    client = await auth_client(KA_RF)
+
+    response = await client.post(CONSOLIDATIONS, json=_with_ids(_body(group, gsz), [uuid.uuid4()]))
+
+    assert response.status_code == HTTP_UNPROCESSABLE, response.text
+    assert response.json()["detail"]["code"] == "RELATED_GROUP_MISMATCH"
+
+
+@pytest.mark.integration
+async def test_create_selected_perimeter_longer_than_limit(
+    auth_client: AuthClientFactory, seeded: AsyncSession
+) -> None:
+    group, gsk, _ = await _scenario(seeded)
+    client = await auth_client(KA_RF)
+
+    response = await client.post(CONSOLIDATIONS, json=_with_ids(_body(group, gsk), [uuid.uuid4() for _ in range(501)]))
+
+    assert response.status_code == HTTP_UNPROCESSABLE, response.text
+    assert response.json()["detail"][0]["loc"] == ["body", "legal_entity_ids"]
+    assert await _count(seeded, Consolidation) == 0
+
+
 @pytest.mark.integration
 async def test_create_repeated_period_is_conflict(auth_client: AuthClientFactory, seeded: AsyncSession) -> None:
     group, gsk, _ = await _scenario(seeded)
diff --git a/api/tests/test_openapi_routes.py b/api/tests/test_openapi_routes.py
index 90d2758..f5ecd88 100644
--- a/api/tests/test_openapi_routes.py
+++ b/api/tests/test_openapi_routes.py
@@ -244,3 +244,10 @@ def test_protected_routes_require_bearer_and_public_do_not(schema: dict[str, Any
             elif not has_bearer:
                 missing.append(f"{method.upper()} {path}")
     assert missing == [], f"маршруты без схемы {BEARER_SCHEME} (Authorize в Swagger не подставит токен): {missing}"
+
+
+def test_consolidation_create_has_optional_selected_perimeter(schema: dict[str, Any]) -> None:
+    """front-api-gaps D-1: `legal_entity_ids` в теле создания — необязательный массив."""
+    create = schema["components"]["schemas"]["ConsolidationCreate"]
+    assert "legal_entity_ids" in create["properties"]
+    assert "legal_entity_ids" not in create.get("required", [])
diff --git a/api/tests/test_schemas_consolidations.py b/api/tests/test_schemas_consolidations.py
index 6cdbdf6..1e52a44 100644
--- a/api/tests/test_schemas_consolidations.py
+++ b/api/tests/test_schemas_consolidations.py
@@ -37,6 +37,16 @@ def test_consolidation_create_year_bounds() -> None:
             ConsolidationCreate(year=year, **ids)
 
 
+def test_consolidation_create_selected_perimeter_bounds() -> None:
+    """D-1: `legal_entity_ids` необязателен (`None` — периметр из ГСК), не больше `MAX_MEMBERS`."""
+    ids = {"company_group_id": uuid.uuid4(), "related_group_id": uuid.uuid4(), "year": 2024, "quarter": "Q3"}
+    assert ConsolidationCreate(**ids).legal_entity_ids is None  # type: ignore[arg-type]
+    selected = [uuid.uuid4() for _ in range(MAX_MEMBERS)]
+    assert len(ConsolidationCreate(**ids, legal_entity_ids=selected).legal_entity_ids or []) == MAX_MEMBERS  # type: ignore[arg-type]
+    with pytest.raises(ValidationError):
+        ConsolidationCreate(**ids, legal_entity_ids=[*selected, uuid.uuid4()])  # type: ignore[arg-type]
+
+
 def test_osv_page_params_limit_bounds() -> None:
     assert (OsvPageParams().limit, OsvPageParams().offset) == (500, 0)  # noqa: PLR2004
     assert OsvPageParams(limit=MAX_LIMIT).limit == MAX_LIMIT