fix(chunk-context): address PR #767 round-3 review — gate readability + legacy-fallback comment

- search/context.py: rename triple-negation gate condition to
  `skip_offset_lookup` named boolean for readability; convert new
  logger.warning to lazy %-style per repo convention.
- api/visualization.py, auth/viz_routes.py: add comment on the offset-only
  Qdrant scroll branch noting it is a legacy path for pre-astrolabe#75
  clients and degrades gracefully on Qdrant Cloud strict mode.

Reviewer item #2 (extracting the duplicated scroll block into a shared
helper) deferred to a follow-up issue per the reviewer's "not blocking"
framing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/api/visualization.py

@@ -601,6 +601,12 @@ async def get_chunk_context(request: Request) -> JSONResponse:
                         with_payload=["chunk_bbox", "page_number"],
                     )
                 else:
+                    # Legacy fallback for clients that don't send chunk_index
+                    # (pre-cbcoutinho/astrolabe#75). chunk_start/end_offset
+                    # aren't indexed in Qdrant Cloud strict mode, so this
+                    # call may fail with HTTP 400 there; the outer except
+                    # logs a warning and the response degrades gracefully
+                    # (no chunk_bbox).
                     points_response = await qdrant_client.scroll(
                         collection_name=settings.get_collection_name(),
                         scroll_filter=Filter(

nextcloud_mcp_server/auth/viz_routes.py

@@ -659,6 +659,12 @@ async def chunk_context_endpoint(request: Request) -> JSONResponse:
                         with_payload=["chunk_bbox", "page_number"],
                     )
                 else:
+                    # Legacy fallback for clients that don't send chunk_index
+                    # (pre-cbcoutinho/astrolabe#75). chunk_start/end_offset
+                    # aren't indexed in Qdrant Cloud strict mode, so this
+                    # call may fail with HTTP 400 there; the outer except
+                    # logs a warning and the response degrades gracefully
+                    # (no chunk_bbox).
                     points_response = await qdrant_client.scroll(
                         collection_name=settings.get_collection_name(),
                         scroll_filter=Filter(

nextcloud_mcp_server/search/context.py

@@ -283,12 +283,13 @@ async def get_chunk_with_context(
             chunk_text = await _get_chunk_by_index_from_qdrant(
                 user_id, doc_id_int, doc_type, chunk_index
             )
-        # Skip the offset fallback for files when the indexed lookup was
+        # Skip the offset fallback for files when the indexed chunk_index
-        # already attempted: Qdrant Cloud's strict mode requires an index on
+        # lookup already ran: chunk_start/end_offset aren't indexed in Qdrant
-        # filtered fields, and chunk_start/end_offset aren't indexed there, so
+        # Cloud strict mode, so the call returns 400 and surfaces a misleading
-        # the call returns 400 and surfaces a misleading logger.error. The
+        # logger.error. The file fast-fail below correctly handles the miss
-        # file fast-fail below correctly handles the miss without it.
+        # without it.
-        if chunk_text is None and not (chunk_index is not None and doc_type == "file"):
+        skip_offset_lookup = chunk_index is not None and doc_type == "file"
+        if chunk_text is None and not skip_offset_lookup:
             chunk_text = await _get_chunk_from_qdrant(
                 user_id, doc_id_int, doc_type, chunk_start, chunk_end
             )
@@ -394,9 +395,12 @@ async def get_chunk_with_context(
     # (the chunk has been removed or re-indexed with different offsets).
     if doc_type == "file":
         logger.warning(
-            f"Chunk not found in Qdrant for file {doc_id} "
+            "Chunk not found in Qdrant for file %s (chunk_index=%s, "
-            f"(chunk_index={chunk_index}, offsets={chunk_start}-{chunk_end}); "
+            "offsets=%s-%s); skipping slow PDF re-parse fallback",
-            "skipping slow PDF re-parse fallback"
+            doc_id,
+            chunk_index,
+            chunk_start,
+            chunk_end,
         )
         return None