feat(library): allow admin delete of Daedalus-managed library via shared cascade

Admin/HTML library delete previously hard-blocked workspace-scoped
(Daedalus-managed) libraries, leaving no way to clear an orphaned Library
node — e.g. one left behind when a Daedalus workspace delete failed to
propagate. A recreate of that workspace then collides on the global
Library.name unique constraint and 500s, freezing ingest.

Allow the delete behind the existing confirm warning (low risk: source
content lives in Daedalus and is recreated + re-embedded on next sync),
and route both the API and HTML delete paths through one shared cascade.

- Add library/services/library_delete.delete_library_cascade(lib), keyed on
  Library uid so it covers global and workspace-scoped libraries. It removes
  Chunks, Images/ImageEmbeddings, Items, Collections, the Library, then GCs
  orphan-only Concepts (verbatim from the API view, re-keyed workspace_id->uid).
- workspace_detail_or_delete (API) now calls the shared helper.
- library_delete (HTML) no longer blocks workspace_id libraries; it calls the
  cascade instead of a bare lib.delete() (which leaked child nodes — also a
  latent bug for global libraries with content).
- Confirm-delete template shows a caution banner for Daedalus-managed libraries.

No migration: Mnemosyne library data is in Neo4j (neomodel); no schema change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

mnemosyne/library/api/workspaces.py

@@ -23,6 +23,7 @@ from rest_framework.permissions import IsAuthenticated
 from rest_framework.response import Response
 
 from library.content_types import get_library_type_config
+from library.services.library_delete import delete_library_cascade
 
 from .serializers import WorkspaceCreateSerializer, WorkspaceStatusSerializer
 
@@ -165,74 +166,15 @@ def workspace_detail_or_delete(request, workspace_id):
     if lib is None:
         return Response(status=status.HTTP_204_NO_CONTENT)
 
-    library_uid = lib.uid
+    # Delete the Library and everything reachable + unique to it, plus
-    library_name = lib.name
+    # orphan-Concept GC. Shared with the admin/HTML delete path.
-
+    result = delete_library_cascade(lib)
-    # Step 1-4: delete chunks, items, collections, then the library itself.
-    # We collect Item s3_keys first so the caller can clean up S3
-    # asynchronously (a future enhancement — for now, the keys are logged).
-    s3_rows, _ = db.cypher_query(
-        "MATCH (l:Library {workspace_id: $wsid})-[:CONTAINS]->(:Collection)"
-        "-[:CONTAINS]->(i:Item) RETURN i.uid, i.s3_key",
-        {"wsid": workspace_id},
-    )
-    item_s3_keys = [(r[0], r[1]) for r in s3_rows if r[1]]
-
-    db.cypher_query(
-        """
-        MATCH (l:Library {workspace_id: $wsid})-[:CONTAINS]->(:Collection)
-        -[:CONTAINS]->(i:Item)-[:HAS_CHUNK]->(c:Chunk)
-        DETACH DELETE c
-        """,
-        {"wsid": workspace_id},
-    )
-    db.cypher_query(
-        """
-        MATCH (l:Library {workspace_id: $wsid})-[:CONTAINS]->(:Collection)
-        -[:CONTAINS]->(i:Item)-[:HAS_IMAGE]->(img:Image)
-        OPTIONAL MATCH (img)-[:HAS_EMBEDDING]->(emb:ImageEmbedding)
-        DETACH DELETE img, emb
-        """,
-        {"wsid": workspace_id},
-    )
-    db.cypher_query(
-        """
-        MATCH (l:Library {workspace_id: $wsid})-[:CONTAINS]->(:Collection)
-        -[:CONTAINS]->(i:Item)
-        DETACH DELETE i
-        """,
-        {"wsid": workspace_id},
-    )
-    db.cypher_query(
-        """
-        MATCH (l:Library {workspace_id: $wsid})-[:CONTAINS]->(col:Collection)
-        DETACH DELETE col
-        """,
-        {"wsid": workspace_id},
-    )
-    db.cypher_query(
-        "MATCH (l:Library {workspace_id: $wsid}) DETACH DELETE l",
-        {"wsid": workspace_id},
-    )
-
-    # Step 5: orphan Concept garbage collection.
-    orphan_result, _ = db.cypher_query(
-        """
-        MATCH (con:Concept)
-        WHERE NOT (con)<-[:REFERENCES]-() AND NOT (con)<-[:MENTIONS]-()
-              AND NOT (con)<-[:DEPICTS]-()
-        WITH con
-        DETACH DELETE con
-        RETURN count(con) AS deleted
-        """
-    )
-    orphans_deleted = orphan_result[0][0] if orphan_result else 0
 
     logger.info(
         "Workspace deleted workspace_id=%s library_uid=%s name=%s "
         "items=%d orphans_deleted=%d",
-        workspace_id, library_uid, library_name,
+        workspace_id, result["library_uid"], result["name"],
-        len(item_s3_keys), orphans_deleted,
+        result["item_count"], result["orphans_deleted"],
     )
 
     return Response(status=status.HTTP_204_NO_CONTENT)

mnemosyne/library/services/library_delete.py

@@ -0,0 +1,108 @@
+"""
+Shared Library deletion cascade.
+
+Deletes a Library node and everything reachable AND unique to it
+(Collections, Items, Chunks, Images + ImageEmbeddings), then garbage-collects
+Concepts that are no longer referenced by any other Library.
+
+Keyed on the Library ``uid`` so it works for *both* global libraries
+(``workspace_id`` is null) and workspace-scoped libraries. This is the single
+source of truth used by:
+
+  * the Daedalus integration API (``DELETE /library/api/workspaces/{id}/``), and
+  * the admin/HTML delete view (``library_delete``).
+
+Concept-safe: orphan-only Concept GC happens at the end. Concepts still
+referenced by another library (workspace or global) are preserved.
+"""
+
+import logging
+
+from neomodel import db
+
+logger = logging.getLogger(__name__)
+
+
+def delete_library_cascade(lib) -> dict:
+    """Delete ``lib`` and all content reachable and unique to it.
+
+    :param lib: A ``library.models.Library`` node instance.
+    :returns: Dict with ``library_uid``, ``name``, ``item_count``,
+        ``item_s3_keys`` (list of ``(uid, s3_key)`` for async S3 cleanup),
+        and ``orphans_deleted`` (Concept GC count).
+    """
+    library_uid = lib.uid
+    library_name = lib.name
+
+    # Collect Item s3_keys first so the caller can clean up S3 asynchronously
+    # (a future enhancement — for now, the keys are returned/logged).
+    s3_rows, _ = db.cypher_query(
+        "MATCH (l:Library {uid: $uid})-[:CONTAINS]->(:Collection)"
+        "-[:CONTAINS]->(i:Item) RETURN i.uid, i.s3_key",
+        {"uid": library_uid},
+    )
+    item_s3_keys = [(r[0], r[1]) for r in s3_rows if r[1]]
+
+    db.cypher_query(
+        """
+        MATCH (l:Library {uid: $uid})-[:CONTAINS]->(:Collection)
+        -[:CONTAINS]->(i:Item)-[:HAS_CHUNK]->(c:Chunk)
+        DETACH DELETE c
+        """,
+        {"uid": library_uid},
+    )
+    db.cypher_query(
+        """
+        MATCH (l:Library {uid: $uid})-[:CONTAINS]->(:Collection)
+        -[:CONTAINS]->(i:Item)-[:HAS_IMAGE]->(img:Image)
+        OPTIONAL MATCH (img)-[:HAS_EMBEDDING]->(emb:ImageEmbedding)
+        DETACH DELETE img, emb
+        """,
+        {"uid": library_uid},
+    )
+    db.cypher_query(
+        """
+        MATCH (l:Library {uid: $uid})-[:CONTAINS]->(:Collection)
+        -[:CONTAINS]->(i:Item)
+        DETACH DELETE i
+        """,
+        {"uid": library_uid},
+    )
+    db.cypher_query(
+        """
+        MATCH (l:Library {uid: $uid})-[:CONTAINS]->(col:Collection)
+        DETACH DELETE col
+        """,
+        {"uid": library_uid},
+    )
+    db.cypher_query(
+        "MATCH (l:Library {uid: $uid}) DETACH DELETE l",
+        {"uid": library_uid},
+    )
+
+    # Orphan Concept garbage collection: drop Concepts no longer referenced
+    # by any Item (REFERENCES/MENTIONS) or Image (DEPICTS).
+    orphan_result, _ = db.cypher_query(
+        """
+        MATCH (con:Concept)
+        WHERE NOT (con)<-[:REFERENCES]-() AND NOT (con)<-[:MENTIONS]-()
+              AND NOT (con)<-[:DEPICTS]-()
+        WITH con
+        DETACH DELETE con
+        RETURN count(con) AS deleted
+        """
+    )
+    orphans_deleted = orphan_result[0][0] if orphan_result else 0
+
+    logger.info(
+        "Library cascade-deleted library_uid=%s name=%s items=%d orphans_deleted=%d",
+        library_uid, library_name, len(item_s3_keys), orphans_deleted,
+    )
+
+    return {
+        "library_uid": library_uid,
+        "name": library_name,
+        "item_count": len(item_s3_keys),
+        "item_s3_keys": item_s3_keys,
+        "orphans_deleted": orphans_deleted,
+    }

mnemosyne/library/templates/library/library_confirm_delete.html

@@ -12,6 +12,18 @@
     <div class="alert alert-warning mb-6">
         <span>Are you sure you want to delete <strong>{{ library.name }}</strong>? This action cannot be undone.</span>
     </div>
+    {% if library.workspace_id %}
+    <div class="alert alert-error mb-6">
+        <span>
+            <strong>This Library is managed by Daedalus</strong>
+            (workspace <code>{{ library.workspace_id }}</code>).
+            Deleting it here removes its embedded content from Mnemosyne, but the
+            source files still live in Daedalus — it will be <strong>recreated and
+            re-embedded on the next Daedalus sync</strong>. Use this to clear an
+            orphaned Library that is blocking workspace re-registration.
+        </span>
+    </div>
+    {% endif %}
     <form method="post">
         {% csrf_token %}
         <div class="flex gap-2">

mnemosyne/library/views.py

@@ -319,20 +319,20 @@ def library_delete(request, uid):
         messages.error(request, f"Library not found: {e}")
         return redirect("library:library-list")
 
-    # Daedalus owns the lifecycle of workspace-scoped libraries — they can
+    # Daedalus owns the lifecycle of workspace-scoped libraries. Deleting one
-    # only be deleted via DELETE /library/api/workspaces/{workspace_id}/.
+    # here is allowed but discouraged: the confirm page warns that Daedalus
-    # Block the human delete path so a stray click can't desync state.
+    # still holds the source content and will recreate + re-embed it on the
-    if lib.workspace_id:
+    # next sync. The risk is low (no data loss — only re-embedding cost), and
-        messages.error(
+    # this is the supported escape hatch for clearing an orphaned Library that
-            request,
+    # blocks workspace re-registration.
-            f'"{lib.name}" is managed by Daedalus workspace '
-            f"{lib.workspace_id}. Delete it from Daedalus, not here.",
-        )
-        return redirect("library:library-detail", uid=uid)
-
     if request.method == "POST":
         name = lib.name
-        lib.delete()
+        # Use the shared cascade so child nodes (Collections/Items/Chunks/
+        # Images) and orphan Concepts are removed too — a bare lib.delete()
+        # would leak them.
+        from .services.library_delete import delete_library_cascade
+
+        delete_library_cascade(lib)
         messages.success(request, f'Library "{name}" deleted.')
         return redirect("library:library-list")
     return render(request, "library/library_confirm_delete.html", {"library": lib})