fix(search): address PR #813 review (viz verify-on-read, owners cache, docs)

- viz_routes: run verify_search_results before returning results. After the
  accessible_owners expansion the viz can surface OTHER users' shared docs, so
  it must drop ones the caller can no longer access (revoked share) — same as
  the nc_semantic_search tool path. (Blocking review item.)
- access_filter: cache list_accessible_owners per user for 30s to keep the OCS
  shares round-trip off the search hot path (failures aren't cached); document
  the single-page OCS limitation; add a clear_accessible_owners_cache() test
  helper. Comment the empty-accessible_owners MatchAny([]) edge case.
- verification: comment why cross-user eviction is a deliberate no-op (eviction
  is scoped to the querying user's id, so a recipient's revoked access never
  deletes the owner's points; the recipient self-heals via accessible_owners).
- algorithms: declare SearchResult.original_score (set by the viz route) so the
  now-precisely-typed result list type-checks.
- tests: cross-user eviction-no-op safety test; autouse owners-cache reset in
  the access_filter + shared-search tests; replace async-no-await qdrant fakes
  with AsyncMock (clears SonarCloud S7503).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/auth/viz_routes.py

@@ -38,6 +38,7 @@ from nextcloud_mcp_server.search.context import (
     get_chunk_bbox_and_page_from_qdrant,
     get_chunk_with_context,
 )
+from nextcloud_mcp_server.search.verification import verify_search_results
 from nextcloud_mcp_server.utils.validation import is_valid_nextcloud_doc_id
 from nextcloud_mcp_server.vector.oauth_sync import (
     NotProvisionedError,
@@ -226,10 +227,18 @@ async def vector_visualization_search(request: Request) -> JSONResponse:
                 # Sort by score before verification
                 all_results.sort(key=lambda r: r.score, reverse=True)
 
-            # No verification needed for visualization - we only need Qdrant metadata
-            # (title, excerpt, doc_type) which is already in search results.
-            # Verification is only needed for sampling (LLM needs full content).
-            search_results = all_results[:limit]
+            # Verify-on-read (ADR-019). Now that accessible_owners is expanded
+            # via OCS shares, the result set can include OTHER users' shared
+            # documents — so we must drop any the caller can no longer access
+            # (e.g. a revoked share whose index entry hasn't reconciled yet),
+            # exactly as the nc_semantic_search tool path does. Skipping this
+            # would let the viz surface stale titles/excerpts from another
+            # user's index after a share is revoked.
+            with trace_operation("vector_viz.verify_on_read"):
+                verified_results, _dropped = await verify_search_results(
+                    nc_client, all_results
+                )
+            search_results = verified_results[:limit]
             search_duration = time.perf_counter() - search_start
 
         # Store original scores and normalize for visualization

nextcloud_mcp_server/search/access_filter.py

@@ -17,12 +17,26 @@ by their original indexer. New points carry both fields.
 from __future__ import annotations
 
 import logging
+import time
 from typing import Any, Protocol
 
 from qdrant_client.models import FieldCondition, Filter, MatchAny, MatchValue
 
 logger = logging.getLogger(__name__)
 
+# Short-lived per-user cache for the OCS shares lookup, which otherwise runs on
+# every search/viz request. Trades up to this many seconds of share-visibility
+# staleness (a freshly-granted share is searchable a little late) for avoiding
+# an OCS round-trip per query. Safe: verify-on-read still gates each result
+# against Nextcloud, so a revoked share is caught there regardless of this cache.
+_OWNERS_CACHE_TTL_SECONDS = 30.0
+_owners_cache: dict[str, tuple[float, list[str]]] = {}
+
+
+def clear_accessible_owners_cache() -> None:
+    """Drop all cached accessible-owners entries (used by tests)."""
+    _owners_cache.clear()
+
 
 class _SharingClientProtocol(Protocol):
     """Subset of SharingClient that this module actually uses."""
@@ -42,9 +56,22 @@ async def list_accessible_owners(
     Duplicates are removed; ordering is not significant (Qdrant ``MatchAny``
     treats the list as a set).
 
+    Results are cached per user for ``_OWNERS_CACHE_TTL_SECONDS`` to keep the
+    OCS round-trip off the search hot path. Failures are not cached.
+
+    Note: ``list_shares(shared_with_me=True)`` returns whatever the OCS endpoint
+    yields in a single page (SharingClient does not paginate today). A user with
+    more incoming shares than the OCS page size could have some owners omitted;
+    if that becomes real, add pagination to SharingClient.
+
     Sharing API failures are non-fatal — we degrade to ``[user_id]`` and log
     so a hiccup in OCS doesn't black-hole the user's own search.
     """
+    now = time.monotonic()
+    cached = _owners_cache.get(user_id)
+    if cached is not None and now - cached[0] < _OWNERS_CACHE_TTL_SECONDS:
+        return list(cached[1])  # copy so callers can't mutate the cached value
+
     owners: set[str] = {user_id}
     try:
         shares = await sharing_client.list_shares(shared_with_me=True)
@@ -55,7 +82,7 @@ async def list_accessible_owners(
             user_id,
             exc,
         )
-        return [user_id]
+        return [user_id]  # don't cache failures — retry on the next search
 
     for share in shares:
         # OCS returns the share owner under `uid_owner` (the file owner,
@@ -65,8 +92,10 @@ async def list_accessible_owners(
         if isinstance(owner, str) and owner:
             owners.add(owner)
 
-    logger.debug("Accessible owners for user %s: %d entries", user_id, len(owners))
-    return list(owners)
+    result = list(owners)
+    _owners_cache[user_id] = (now, result)
+    logger.debug("Accessible owners for user %s: %d entries", user_id, len(result))
+    return list(result)
 
 
 def build_ownership_filter(
@@ -90,6 +119,11 @@ def build_ownership_filter(
         A Qdrant ``Filter`` ready to be nested under a parent ``must`` clause.
     """
     owners = accessible_owners if accessible_owners is not None else [user_id]
+    # Edge case: an explicit empty ``accessible_owners`` yields
+    # ``MatchAny(any=[])``, which Qdrant treats as matching nothing — so the
+    # owner_id branch contributes no results and access comes solely from the
+    # legacy ``user_id`` branch below (self-owned content). Callers that want
+    # share expansion must pass a non-empty list.
     return Filter(
         should=[
             FieldCondition(key="owner_id", match=MatchAny(any=owners)),

nextcloud_mcp_server/search/algorithms.py

@@ -168,6 +168,9 @@ class SearchResult:
     chunk_index: int = 0
     total_chunks: int = 1
     point_id: str | None = None
+    # Pre-normalization score, set by the visualization route before it rescales
+    # ``score`` to [0, 1] for visual encoding (see auth/viz_routes.py).
+    original_score: float | None = None
 
     def __post_init__(self):
         """Validate score is non-negative.

nextcloud_mcp_server/search/verification.py

@@ -586,6 +586,15 @@ async def verify_search_results(
     if evict_on_missing and inaccessible:
 
         async def evict(doc_id: str, doc_type: str) -> None:
+            # Eviction is scoped to the QUERYING user's own points
+            # (user_id == the searcher). For a cross-user shared document
+            # (owner_id=alice surfaced to bob via accessible_owners), bob
+            # failing verification evicts with user_id=bob — a deliberate
+            # no-op, because alice's points carry user_id=alice and must NOT
+            # be deleted just because bob's share was revoked. Bob's view
+            # self-heals via list_accessible_owners (alice drops out of his
+            # accessible owners once OCS no longer reports the share). See the
+            # legacy-user_id semantics note in build_ownership_filter.
             try:
                 await delete_document_points(doc_id, doc_type, user_id)
             except Exception as e: