feat(api): expose owning project on entity resolve

Expose project_external_id on v2 entity resolve responses so cloud callers can authorize cross-project targets without a second tenant DB lookup.

src/basic_memory/api/v2/routers/knowledge_router.py

@@ -18,6 +18,7 @@ from basic_memory.deps import (
     EntityServiceV2ExternalDep,
     SearchServiceV2ExternalDep,
     LinkResolverV2ExternalDep,
+    ProjectRepositoryDep,
     ProjectConfigV2ExternalDep,
     AppConfigDep,
     EntityRepositoryV2ExternalDep,
@@ -152,6 +153,7 @@ async def resolve_identifier(
     data: EntityResolveRequest,
     link_resolver: LinkResolverV2ExternalDep,
     entity_repository: EntityRepositoryV2ExternalDep,
+    project_repository: ProjectRepositoryDep,
 ) -> EntityResolveResponse:
     """Resolve a string identifier (external_id, permalink, title, or path) to entity info.
 
@@ -175,6 +177,7 @@ async def resolve_identifier(
         {
             "external_id": "550e8400-e29b-41d4-a716-446655440000",
             "entity_id": 123,
+            "project_external_id": "4b9b7a10-7a63-48d2-ae3f-0d6a2c69313f",
             "permalink": "specs/search",
             "file_path": "specs/search.md",
             "title": "Search Specification",
@@ -209,9 +212,17 @@ async def resolve_identifier(
         if not entity:
             raise HTTPException(status_code=404, detail=f"Entity not found: '{data.identifier}'")
 
+        owner_project = await project_repository.get_by_id(entity.project_id)
+        if not owner_project:  # pragma: no cover
+            raise HTTPException(
+                status_code=500,
+                detail="Resolved entity references an unknown project",
+            )
+
         result = EntityResolveResponse(
             external_id=entity.external_id,
             entity_id=entity.id,
+            project_external_id=owner_project.external_id,
             permalink=entity.permalink,
             file_path=entity.file_path,
             title=entity.title,

src/basic_memory/schemas/v2/entity.py

@@ -45,6 +45,7 @@ class EntityResolveResponse(BaseModel):
 
     external_id: str = Field(..., description="External UUID (primary API identifier)")
     entity_id: int = Field(..., description="Numeric entity ID (internal identifier)")
+    project_external_id: str = Field(..., description="External UUID of the owning project")
     permalink: Optional[str] = Field(None, description="Entity permalink")
     file_path: str = Field(..., description="Relative file path")
     title: str = Field(..., description="Entity title")

tests/api/v2/test_knowledge_router.py

@@ -1,11 +1,14 @@
 """Tests for V2 knowledge graph API routes (ID-based endpoints)."""
 
+from datetime import datetime, timezone
 import uuid
 
 import pytest
 from httpx import AsyncClient
 
-from basic_memory.models import Project
+from basic_memory.models import Entity as EntityModel, Project
+from basic_memory.repository.entity_repository import EntityRepository
+from basic_memory.repository.project_repository import ProjectRepository
 from basic_memory.schemas import DeleteEntitiesResponse
 from basic_memory.schemas.response import DirectoryMoveResult, DirectoryDeleteResult
 from basic_memory.schemas.v2 import EntityResponseV2, EntityResolveResponse
@@ -40,10 +43,55 @@ async def test_resolve_identifier_by_permalink(
     assert response.status_code == 200
     resolved = EntityResolveResponse.model_validate(response.json())
     assert resolved.entity_id == entity_id
+    assert resolved.project_external_id == test_project.external_id
     assert resolved.permalink == created_entity.permalink
     assert resolved.resolution_method == "permalink"
 
 
+@pytest.mark.asyncio
+async def test_resolve_identifier_returns_target_project_external_id_for_cross_project_link(
+    client: AsyncClient,
+    session_maker,
+    tmp_path,
+    v2_project_url,
+):
+    """Cross-project resolves should expose the owning project external ID."""
+    project_repository = ProjectRepository(session_maker)
+    other_project = await project_repository.create(
+        {
+            "name": "other-project",
+            "description": "Secondary project",
+            "path": str(tmp_path / "other-project"),
+            "is_active": True,
+            "is_default": False,
+        }
+    )
+    now = datetime.now(timezone.utc)
+    other_entity_repository = EntityRepository(session_maker, project_id=other_project.id)
+    target = await other_entity_repository.add(
+        EntityModel(
+            title="Cross Project Note",
+            note_type="note",
+            content_type="text/markdown",
+            file_path="docs/Cross Project Note.md",
+            permalink=f"{other_project.permalink}/docs/cross-project-note",
+            created_at=now,
+            updated_at=now,
+            project_id=other_project.id,
+        )
+    )
+
+    response = await client.post(
+        f"{v2_project_url}/knowledge/resolve",
+        json={"identifier": "other-project::Cross Project Note", "strict": True},
+    )
+
+    assert response.status_code == 200
+    resolved = EntityResolveResponse.model_validate(response.json())
+    assert resolved.entity_id == target.id
+    assert resolved.project_external_id == other_project.external_id
+
+
 @pytest.mark.asyncio
 async def test_resolve_identifier_not_found(client: AsyncClient, v2_project_url):
     """Test resolving a non-existent identifier returns 404."""