feat: expose external_id in EntityResponse and link resolver (#569)

Signed-off-by: Drew Cain <groksrc@gmail.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: groksrc

src/basic_memory/schemas/response.py

@@ -195,6 +195,7 @@ class EntityResponse(SQLAlchemyModel):
     entity_metadata: Optional[Dict] = None
     checksum: Optional[str] = None
     content_type: ContentType
+    external_id: Optional[str] = None
     observations: List[ObservationResponse] = []
     relations: List[RelationResponse] = []
     created_at: datetime

src/basic_memory/services/link_resolver.py

@@ -1,5 +1,6 @@
 """Service for resolving markdown links to permalinks."""
 
+import uuid as uuid_mod
 from typing import Optional, Tuple, Dict
 
 from loguru import logger
@@ -63,6 +64,19 @@ async def resolve_link(
         explicit_project_reference = "::" in clean_text
         clean_text = normalize_project_reference(clean_text)
 
+        # --- External ID Resolution ---
+        # Try external_id first if identifier looks like a UUID.
+        # Canonicalize to lowercase-hyphen form so uppercase or unhyphenated
+        # UUIDs also match the stored external_id values.
+        try:
+            canonical_id = str(uuid_mod.UUID(clean_text))
+            entity = await self.entity_repository.get_by_external_id(canonical_id)
+            if entity:
+                logger.debug(f"Found entity by external_id: {entity.permalink}")
+                return entity
+        except ValueError:
+            pass
+
         # Trigger: link uses project namespace syntax (project::note)
         # Why: treat it as an explicit cross-project reference
         # Outcome: resolve only within the referenced project scope

tests/services/test_link_resolver.py

@@ -1,5 +1,6 @@
 """Tests for link resolution service."""
 
+import uuid
 from datetime import datetime, timezone
 
 import pytest
@@ -857,3 +858,44 @@ async def test_simple_link_no_slash_skips_relative_resolution(relative_path_reso
     # testing/nested/ is not the same folder as testing/, but it's closer than nested/
     # The context-aware resolution will pick the closest match
     assert result.file_path == "testing/nested/deep-note.md"
+
+
+# ============================================================================
+# External ID (UUID) resolution tests
+# ============================================================================
+
+
+@pytest.mark.asyncio
+async def test_resolve_link_by_external_id(link_resolver, test_entities):
+    """Test resolving a link using a valid external_id (UUID)."""
+    entity = test_entities[0]
+    result = await link_resolver.resolve_link(entity.external_id)
+    assert result is not None
+    assert result.id == entity.id
+    assert result.external_id == entity.external_id
+
+
+@pytest.mark.asyncio
+async def test_resolve_link_by_external_id_uppercase(link_resolver, test_entities):
+    """Test that uppercase UUID is canonicalized and resolves correctly."""
+    entity = test_entities[0]
+    upper_id = entity.external_id.upper()
+    result = await link_resolver.resolve_link(upper_id)
+    assert result is not None
+    assert result.id == entity.id
+
+
+@pytest.mark.asyncio
+async def test_resolve_link_by_external_id_nonexistent(link_resolver):
+    """Test that a valid UUID format that doesn't match any entity returns None."""
+    fake_id = str(uuid.uuid4())
+    result = await link_resolver.resolve_link(fake_id)
+    assert result is None
+
+
+@pytest.mark.asyncio
+async def test_resolve_link_non_uuid_falls_through(link_resolver, test_entities, project_prefix):
+    """Test that non-UUID strings skip UUID resolution and use normal lookup."""
+    result = await link_resolver.resolve_link("Core Service")
+    assert result is not None
+    assert result.permalink == f"{project_prefix}/components/core-service"