diff --git a/api/routers/fabric.py b/api/routers/fabric.py
index bb7c921..98e704b 100644
--- a/api/routers/fabric.py
+++ b/api/routers/fabric.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import uuid
 from typing import Any
 
 import httpx
@@ -10,6 +11,8 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from api.database import get_session
 from api.models.fabric_graph import FabricGraphEdge, FabricGraphImport, FabricGraphNode
 from api.schemas.fabric_graph import (
+    FabricGraphActivationRequest,
+    FabricGraphActivationResult,
     FabricGraphEdgeRead,
     FabricGraphImportRead,
     FabricGraphIngestResult,
@@ -19,6 +22,7 @@ from api.schemas.fabric_graph import (
 )
 from api.services.fabric_graph import (
     FabricGraphValidationError,
+    activate_fabric_graph_import,
     ingest_fabric_graph_export,
     record_fabric_graph_error,
     split_graph_ingest_body,
@@ -132,6 +136,34 @@ async def latest_graph_import(
     return FabricGraphImportRead.model_validate(import_run)
 
 
+@router.post(
+    "/graph-exports/{import_id}/activate",
+    response_model=FabricGraphActivationResult,
+)
+async def activate_graph_import(
+    import_id: uuid.UUID,
+    body: FabricGraphActivationRequest | None = None,
+    session: AsyncSession = Depends(get_session),
+) -> FabricGraphActivationResult:
+    request = body or FabricGraphActivationRequest()
+    try:
+        import_run, previous_import_id, activated = await activate_fabric_graph_import(
+            session,
+            import_id,
+            requested_by=request.requested_by,
+        )
+    except ValueError as exc:
+        raise HTTPException(status_code=409, detail=str(exc)) from exc
+    if import_run is None:
+        raise HTTPException(status_code=404, detail=f"Fabric graph import '{import_id}' not found")
+    return FabricGraphActivationResult(
+        import_run=FabricGraphImportRead.model_validate(import_run),
+        previous_import_id=previous_import_id,
+        activated=activated,
+        idempotent=not activated,
+    )
+
+
 @router.get("/graph/nodes", response_model=list[FabricGraphNodeRead])
 async def list_graph_nodes(
     source_repo_slug: str = "railiance-fabric",
diff --git a/api/schemas/fabric_graph.py b/api/schemas/fabric_graph.py
index 3c9e98e..6afe417 100644
--- a/api/schemas/fabric_graph.py
+++ b/api/schemas/fabric_graph.py
@@ -261,6 +261,17 @@ class FabricGraphIngestResult(BaseModel):
     edge_count: int
 
 
+class FabricGraphActivationRequest(BaseModel):
+    requested_by: str = "operator"
+
+
+class FabricGraphActivationResult(BaseModel):
+    import_run: FabricGraphImportRead
+    previous_import_id: uuid.UUID | None = None
+    activated: bool
+    idempotent: bool
+
+
 class FabricGraphNodeRead(BaseModel):
     model_config = ConfigDict(from_attributes=True)
 
diff --git a/api/services/fabric_graph.py b/api/services/fabric_graph.py
index 8a98bf3..48f1fef 100644
--- a/api/services/fabric_graph.py
+++ b/api/services/fabric_graph.py
@@ -221,6 +221,55 @@ async def ingest_fabric_graph_export(
     return import_run, True, False
 
 
+async def activate_fabric_graph_import(
+    session: AsyncSession,
+    import_id: Any,
+    *,
+    requested_by: str,
+) -> tuple[FabricGraphImport | None, Any | None, bool]:
+    """Select a retained valid import as the active read model.
+
+    Imports are immutable. Activation only moves the per-source ``is_latest``
+    marker, which makes cutover rollback fast and avoids re-fetching an older
+    authority payload during an incident.
+    """
+    result = await session.execute(
+        select(FabricGraphImport).where(FabricGraphImport.id == import_id)
+    )
+    import_run = result.scalar_one_or_none()
+    if import_run is None:
+        return None, None, False
+    if import_run.validation_status != "valid":
+        raise ValueError("Only a valid Fabric graph import can be activated.")
+
+    previous_result = await session.execute(
+        select(FabricGraphImport).where(
+            FabricGraphImport.source_repo_slug == import_run.source_repo_slug,
+            FabricGraphImport.is_latest.is_(True),
+        )
+    )
+    previous = previous_result.scalars().first()
+    if previous is not None and previous.id == import_run.id:
+        return import_run, previous.id, False
+
+    await _mark_latest(session, import_run)
+    import_run.last_seen_at = datetime.now(timezone.utc)
+    await _record_progress(
+        session,
+        "Fabric graph read model activation changed.",
+        {
+            "source_repo_slug": import_run.source_repo_slug,
+            "import_id": str(import_run.id),
+            "previous_import_id": str(previous.id) if previous else None,
+            "content_hash": import_run.content_hash,
+            "requested_by": requested_by,
+        },
+    )
+    await session.commit()
+    await session.refresh(import_run)
+    return import_run, previous.id if previous else None, True
+
+
 def validate_fabric_graph_export(payload: dict[str, Any]) -> FabricGraphExportPayload:
     try:
         export = FabricGraphExportPayload.model_validate(payload)
diff --git a/docs/fabric-graph-read-model.md b/docs/fabric-graph-read-model.md
index 15ddcec..da83e4c 100644
--- a/docs/fabric-graph-read-model.md
+++ b/docs/fabric-graph-read-model.md
@@ -61,6 +61,20 @@ curl -s http://127.0.0.1:8000/fabric/graph-exports/latest
 curl -s http://127.0.0.1:8000/fabric/graph/summary
 ```
 
+Imports are immutable and retained. To roll the read model back to a previously
+validated import without depending on the source service, activate its import
+record; repeat the operation with the newer import id to roll forward again:
+
+```bash
+curl -s -X POST \
+  http://127.0.0.1:8000/fabric/graph-exports/<import-id>/activate \
+  -H "Content-Type: application/json" \
+  -d '{"requested_by":"operator-rollback"}'
+```
+
+Activation only moves the per-source latest marker. It does not alter or delete
+either graph snapshot, and activating the current import is idempotent.
+
 Representative relationship queries:
 
 ```bash
diff --git a/tests/test_routers_core.py b/tests/test_routers_core.py
index 49ed399..42ef6ea 100644
--- a/tests/test_routers_core.py
+++ b/tests/test_routers_core.py
@@ -1545,6 +1545,33 @@ class TestFabricGraphReadModel:
         assert latest_flags[first_id] is False
         assert latest_flags[second_id] is True
 
+    async def test_retained_valid_import_can_be_activated_for_rollback(self, client):
+        r = await client.post("/fabric/graph-exports", json=_fabric_graph_export())
+        first_id = r.json()["import_run"]["id"]
+        r = await client.post("/fabric/graph-exports", json=_fabric_graph_export(extra_node=True))
+        second_id = r.json()["import_run"]["id"]
+
+        r = await client.post(
+            f"/fabric/graph-exports/{first_id}/activate",
+            json={"requested_by": "cutover-test"},
+        )
+        assert r.status_code == 200, r.text
+        assert r.json()["activated"] is True
+        assert r.json()["idempotent"] is False
+        assert r.json()["previous_import_id"] == second_id
+        assert r.json()["import_run"]["id"] == first_id
+        assert (await client.get("/fabric/graph/summary")).json()["node_count"] == 3
+
+        r = await client.post(f"/fabric/graph-exports/{first_id}/activate")
+        assert r.status_code == 200, r.text
+        assert r.json()["activated"] is False
+        assert r.json()["idempotent"] is True
+
+        r = await client.post(f"/fabric/graph-exports/{second_id}/activate")
+        assert r.status_code == 200, r.text
+        assert r.json()["previous_import_id"] == first_id
+        assert (await client.get("/fabric/graph/summary")).json()["node_count"] == 4
+
     async def test_read_only_queries_filter_graph_without_mutating_state_hub_entities(self, client):
         await _create_domain(client)
         topic = await _create_topic(client)