fix: Terminate sync immediately when project is deleted (#366)

Signed-off-by: phernandez <paul@basicmachines.co>
Co-authored-by: Claude <noreply@anthropic.com>

src/basic_memory/repository/entity_repository.py

@@ -135,7 +135,20 @@ class EntityRepository(Repository[Entity]):
                     )
                 return found
 
-            except IntegrityError:
+            except IntegrityError as e:
+                # Check if this is a FOREIGN KEY constraint failure
+                error_str = str(e)
+                if "FOREIGN KEY constraint failed" in error_str:
+                    # Import locally to avoid circular dependency (repository -> services -> repository)
+                    from basic_memory.services.exceptions import SyncFatalError
+
+                    # Project doesn't exist in database - this is a fatal sync error
+                    raise SyncFatalError(
+                        f"Cannot sync file '{entity.file_path}': "
+                        f"project_id={entity.project_id} does not exist in database. "
+                        f"The project may have been deleted. This sync will be terminated."
+                    ) from e
+
                 await session.rollback()
 
                 # Re-query after rollback to get a fresh, attached entity

src/basic_memory/services/exceptions.py

@@ -20,3 +20,18 @@ class DirectoryOperationError(Exception):
     """Raised when directory operations fail"""
 
     pass
+
+
+class SyncFatalError(Exception):
+    """Raised when sync encounters a fatal error that prevents continuation.
+
+    Fatal errors include:
+    - Project deleted during sync (FOREIGN KEY constraint)
+    - Database corruption
+    - Critical system failures
+
+    When this exception is raised, the entire sync operation should be terminated
+    immediately rather than attempting to continue with remaining files.
+    """
+
+    pass

src/basic_memory/sync/sync_service.py

@@ -22,6 +22,7 @@ from basic_memory.models import Entity, Project
 from basic_memory.repository import EntityRepository, RelationRepository, ObservationRepository
 from basic_memory.repository.search_repository import SearchRepository
 from basic_memory.services import EntityService, FileService
+from basic_memory.services.exceptions import SyncFatalError
 from basic_memory.services.link_resolver import LinkResolver
 from basic_memory.services.search_service import SearchService
 from basic_memory.services.sync_status_service import sync_status_tracker, SyncStatus
@@ -514,6 +515,13 @@ class SyncService:
             return entity, checksum
 
         except Exception as e:
+            # Check if this is a fatal error (or caused by one)
+            # Fatal errors like project deletion should terminate sync immediately
+            if isinstance(e, SyncFatalError) or isinstance(e.__cause__, SyncFatalError):
+                logger.error(f"Fatal sync error encountered, terminating sync: path={path}")
+                raise
+
+            # Otherwise treat as recoverable file-level error
             error_msg = str(e)
             logger.error(f"Failed to sync file: path={path}, error={error_msg}")