fix(search): gate verify-on-read file results on vector-index tag membership

Verify-on-read only checked file *accessibility* (file_accessible_by_id),
never tag membership, so a file removed from the `vector-index` tag (but
still readable) kept surfacing in semantic search, and stale points only
got evicted when they happened to rank in a search's top-K.

Rework `_verify_files` to gate on current `vector-index` tag membership via
a single batch `find_files_by_tag(tag, mime_type_filter="application/pdf")`
REPORT per search (plus a one-shot EXCLUDED_TAGS lookup for exclusion-wins
parity) — exactly what the scanner indexes. A file is kept iff it is in that
set, so untagged / deleted / excluded files drop out immediately and the
existing eviction wiring reclaims their Qdrant points. The gate is strict
for all file results, own and shared. Mirrors the batch-fetch-and-intersect
shape of `_verify_news_items` (one semaphore slot, fail-open on fetch error,
malformed-id keep).

- Promote the tag name to a `vector_sync_pdf_tag` Settings field (dynaconf
  env mapping VECTOR_SYNC_PDF_TAG) used by both scanner and verifier;
  drop the scanner's direct os.getenv.
- Expose `find_files_by_tag` on NextcloudClientProtocol.
- Rewrite the file-verifier unit tests (tagged/untagged/deleted/excluded/
  fail-open/non-numeric); update the ACL + verify-on-read integration tests
  to seed tagged PDFs.
- Amend ADR-019 and the configuration.md verify-on-read latency budget.

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

docs/ADR-019-verify-on-read-for-semantic-search.md

@@ -4,6 +4,22 @@
 **Date**: 2026-05-01
 **Depends On**: ADR-007 (Background Vector Sync), ADR-010 (Webhook-Based Vector Sync)
 
+> **Update (2026-06-02) — tag-aware file verification.** The `file` verifier
+> described below as a per-id WebDAV check (`PROPFIND`, later
+> `file_accessible_by_id`) now gates on current **`vector-index` tag
+> membership** instead. It issues a single
+> `find_files_by_tag(<VECTOR_SYNC_PDF_TAG>, mime_type_filter="application/pdf")`
+> REPORT per search (plus a one-shot `EXCLUDED_TAGS` lookup) and keeps only
+> files in that set — i.e. exactly what the scanner indexes. This is the
+> "fetch once and intersect" shape (like `news_item`), not per-id fan-out, and
+> it closes a gap the original design missed: a file *removed from the tag* (as
+> opposed to deleted/unshared) stayed accessible and so survived the old check,
+> lingering in results until the scanner's grace-period sweep. **Decision:** the
+> gate is strict for all file results, own and shared — a shared file survives
+> only if the owner's (userVisible) tag surfaces in the *searcher's* tag REPORT
+> (validated by `tests/integration/test_acl_shared_search.py`). See
+> `docs/configuration.md` → "Verify-on-Read Latency Budget" for the cost.
+
 ## Context
 
 The vector index in Qdrant is a *recall layer*, not the source of truth. Authoritative state for every indexed document — whether a note exists, whether a file is still shared with the user, whether a deck card is on a board the user can read — lives in Nextcloud, not in our index. Whenever those two views drift, semantic search returns **ghost records**: results that point to documents the user can no longer access (or that no longer exist at all).

docs/configuration.md

@@ -645,10 +645,12 @@ This adds Nextcloud round-trips to the search path that operators should be
 aware of:
 
 - **Per-search cost**: one Nextcloud round-trip per *unique* `(doc_id, doc_type)`
-  in the result set. Chunking means a 10-result page typically references 3-5
+  in the result set — except `file` and `news_item`, which each batch into a
-  unique documents, so verification adds 3-5 round-trips. With the default
+  single call per search regardless of how many results they contribute (see
-  20-way concurrency this is one parallel batch — usually under 100 ms on a
+  the Files and News caveats below). Chunking means a 10-result page typically
-  healthy connection.
+  references 3-5 unique documents, so verification adds 3-5 round-trips. With
+  the default 20-way concurrency this is one parallel batch — usually under
+  100 ms on a healthy connection.
 - **Concurrency**: all verifications fan out under a shared semaphore.
   Tunable via the `VERIFICATION_CONCURRENCY` env var (settings field
   `verification_concurrency`, default 20) — lower it if your Nextcloud
@@ -664,14 +666,28 @@ aware of:
   search that surfaces news results. Disabling News in the indexer or running
   with a smaller backlog mitigates this; per-item paginated verification is
   tracked as a future improvement.
-- **Eviction**: when verification finds a definitive miss (404 / 403), the
+- **Files caveat**: `file` results are gated on current **`vector-index` tag
-  corresponding Qdrant points are deleted in the background on a lifespan-owned
+  membership**, not bare access — the verifier issues a single
-  task group — fire-and-forget, does **not** block the search response.
+  `find_files_by_tag(<tag>, mime_type_filter="application/pdf")` REPORT per
-  Eviction failures are logged but never propagated; the next query will
+  search that contains any file result (plus a one-shot `EXCLUDED_TAGS`
-  re-verify and re-attempt (self-healing).
+  lookup), then keeps only files in that set. This matches exactly what the
+  scanner indexes, so a file removed from the tag (or deleted, or moved under
+  an excluded folder) drops out of results immediately rather than waiting for
+  the scanner sweep. The REPORT expands tagged folders via a `Depth: infinity`
+  SEARCH, so deployments that tag whole directory trees pay that walk once per
+  search; configure `VECTOR_SYNC_PDF_TAG` to change the tag name. **Shared
+  files**: a file an owner tagged and shared with the searcher only survives
+  verification if the owner's (userVisible) tag surfaces in the *searcher's*
+  tag REPORT.
+- **Eviction**: when verification finds a definitive miss (a 404 / 403, or — for
+  files — absence from the tag set), the corresponding Qdrant points are deleted
+  in the background on a lifespan-owned task group — fire-and-forget, does
+  **not** block the search response. Eviction failures are logged but never
+  propagated; the next query will re-verify and re-attempt (self-healing).
 - **Failure modes**: transient errors (5xx, network) keep results visible
   (fail open) so a flaky link does not silently shrink result pages; only
-  *definitive* 404 / 403 drops them.
+  *definitive* misses (404 / 403, or a file no longer in the tag set) drop them.
+  If the file tag REPORT itself errors, all file results are kept (fail open).
 
 If eviction ever needs to be disabled (debugging, benchmarking), the
 `evict_on_missing=False` keyword argument on `verify_search_results()` skips

nextcloud_mcp_server/config.py

@@ -93,6 +93,10 @@ _DEFAULTS: dict[str, Any] = {
     # leave work stuck behind the 5x-scan-interval staleness gate.
     # Escape hatch only — leave on by default.
     "vector_sync_orphan_sweep_enabled": True,
+    # System tag that marks files for vector indexing. The scanner indexes
+    # files carrying this tag; verify-on-read gates results on current
+    # membership of this tag (ADR-019).
+    "vector_sync_pdf_tag": "vector-index",
     # Verify-on-read concurrency cap (ADR-019)
     "verification_concurrency": 20,
     # Qdrant
@@ -625,6 +629,10 @@ class Settings:
     vector_sync_queue_max_size: int = 10000
     vector_sync_user_poll_interval: int = 60  # seconds - OAuth mode user discovery
     vector_sync_orphan_sweep_enabled: bool = True  # card #101
+    # System tag marking files for vector indexing. The scanner indexes files
+    # carrying this tag and verify-on-read gates results on current membership
+    # (ADR-019), so an untagged file drops out of search immediately.
+    vector_sync_pdf_tag: str = "vector-index"
 
     # Verify-on-read concurrency (ADR-019). Cap on parallel Nextcloud
     # round-trips during search-result verification fan-out. Lower this if the
@@ -1217,6 +1225,7 @@ def get_settings() -> Settings:
         "vector_sync_queue_max_size": "VECTOR_SYNC_QUEUE_MAX_SIZE",
         "vector_sync_user_poll_interval": "VECTOR_SYNC_USER_POLL_INTERVAL",
         "vector_sync_orphan_sweep_enabled": "VECTOR_SYNC_ORPHAN_SWEEP_ENABLED",
+        "vector_sync_pdf_tag": "VECTOR_SYNC_PDF_TAG",
         # Verify-on-read (ADR-019)
         "verification_concurrency": "VERIFICATION_CONCURRENCY",
         # Qdrant settings

nextcloud_mcp_server/search/algorithms.py

@@ -75,6 +75,14 @@ class NextcloudClientProtocol(Protocol):
         """News client for accessing news item documents."""
         ...
 
+    # Top-level client helper (not a sub-client) used by verify-on-read to
+    # gate file results on current vector-index tag membership.
+    async def find_files_by_tag(
+        self, tag_name: str, mime_type_filter: str | None = None
+    ) -> list[dict]:
+        """Return files carrying ``tag_name`` (folders expanded by MIME)."""
+        ...
+
 
 async def get_indexed_doc_types(
     user_id: str, accessible_owners: list[str] | None = None

nextcloud_mcp_server/search/verification.py

@@ -8,18 +8,21 @@ access (deleted, unshared, etc.) and lazily evicting them from the index.
 Per-doc_type verifiers are registered in ``_VERIFIERS``. Each takes the
 authenticated client, the (deduplicated) list of ``SearchResult``s for that
 doc_type, and a shared concurrency semaphore. They return the subset of
-``doc_id`` values that are currently accessible. Verifiers read whatever
+``doc_id`` values that are currently visible to the user. Verifiers read
-metadata they need (file path, deck card board/stack ids) directly from the
+whatever metadata they need (e.g. deck card board/stack ids) directly from the
 SearchResult — these fields are populated at index-time and propagated by
 the algorithm layer (see ``search/bm25_hybrid.py`` and ``search/semantic.py``)
-so verification adds zero extra Qdrant round-trips.
+so verification adds zero extra Qdrant round-trips. The file verifier is the
+exception: it gates results on current ``vector-index`` tag membership via a
+single batch tag REPORT (which also confirms access), so it does not read
+per-result metadata.
 
 Concurrency is bounded by a shared semaphore (default 20) so a large search
 result page (or a multi-doc_type query) cannot exhaust the httpx connection
 pool or trigger Nextcloud rate limiting. The 20-slot default matches the
 context-expansion convention in ``server/semantic.py``.
 
-Failure policy:
+Failure policy (notes / deck_card / news_item — the per-access verifiers):
 
 - Definitive 403/404 from Nextcloud → drop the result and schedule eviction.
 - Transient errors (5xx, network blips, unexpected exceptions) → keep the
@@ -28,6 +31,12 @@ Failure policy:
 - Unsupported doc_type (no registered verifier) → keep the result and log a
   warning. Verification is opt-in per type; a missing verifier is a soft
   failure, not a search failure.
+
+The ``file`` verifier is the exception to the first rule: it gates on current
+``vector-index`` tag membership (a single batch tag REPORT), so a file is
+dropped+evicted when it is absent from the tag set — untagged, deleted, or
+under an ``EXCLUDED_TAGS`` folder — not on a per-file 403/404. A failed tag
+fetch still fails open. See ``_verify_files`` for the full contract.
 """
 
 import logging
@@ -132,81 +141,110 @@ async def _verify_files(
     results: list[SearchResult],
     semaphore: anyio.Semaphore,
 ) -> set[str]:
-    """Return the doc_ids of file results this user may actually access.
+    """Return the doc_ids of file results this user may currently see.
 
-    Verifies each file by its *global* Nextcloud file id via an ACL-aware
+    A file is included iff it *currently* carries the ``vector-index`` tag (the
-    WebDAV SEARCH (``webdav.file_accessible_by_id``), NOT by path. This is the
+    same tag the scanner indexes on) AND is not under an ``EXCLUDED_TAGS``
-    ACL-aware-search fix: a file an owner shared with the querying user mounts
+    folder — full parity with the indexing rules. The tag REPORT runs over the
-    at a different path under each tree, so the previous path-based check
+    querying user's own files tree (including mounted shares), so membership in
-    (``get_file_info``) produced false 404s and dropped legitimate shared-file
+    the tagged set already implies the file is *accessible*; this single batch
-    hits. Definitive 403/404 → inaccessible (dropped + scheduled for eviction
+    fetch therefore subsumes the old per-file ``file_accessible_by_id`` check
-    by the caller); transient/ambiguous errors → kept (fail-open).
+    and replaces N round-trips with one.
+
+    This is the verify-on-read fix for stale tags (ADR-019): a file removed
+    from the ``vector-index`` tag — or outright deleted — drops out of the
+    tagged set, so it is dropped from results and scheduled for eviction by the
+    caller immediately, rather than lingering until the scanner's grace-period
+    sweep reconciles it.
+
+    Failure policy mirrors ``_verify_news_items``: if the tag fetch itself
+    fails we keep every file result (fail-open, the next query re-verifies),
+    and malformed/non-numeric doc_ids are kept (defense-in-depth — the numeric
+    tag REPORT cannot match them, and producer-side validation is the real
+    boundary, so false-positive is preferred over false-negative).
     """
-    # safe: cooperative concurrency, no lock needed (see verify_search_results)
+    # Lazy import to break an import cycle: ``server/__init__`` imports
-    accessible: set[str] = set()
+    # ``server.semantic`` which imports this module, so importing
+    # ``server.tag_exclusion`` at module load time would re-enter a
+    # partially-initialised ``server`` package depending on import order.
+    from nextcloud_mcp_server.server.tag_exclusion import (  # noqa: PLC0415
+        get_excluded_file_paths,
+        is_path_excluded,
+    )
 
-    async def check(result: SearchResult) -> None:
+    tag_name = get_settings().vector_sync_pdf_tag
-        doc_id = result.id
-        # file_path is propagated from the Qdrant payload by the algorithm
-        # layer (bm25_hybrid.py / semantic.py); kept here only for log context.
-        file_path = (result.metadata or {}).get("path")
 
-        # Verify by *global* file ID via an ACL-aware WebDAV SEARCH, NOT by
+    # One batch fetch per search, holding a single semaphore slot (same
-        # path. For files the vector ``doc_id`` IS the Nextcloud file ID, and
+    # backpressure rationale as _verify_news_items): the tagged-file REPORT
-        # file_accessible_by_id searches the user's whole tree (incl. mounted
+    # plus optional Depth:infinity folder expansion — and the EXCLUDED_TAGS
-        # shares), so a file an owner shared with this user verifies as
+    # lookup — are one round-trip set, not one per result.
-        # accessible even though it lives at a different path under the owner's
+    #
-        # root. A path-based check (the old behaviour) would 404 on shared
+    # TODO(perf): if folder expansion dominates query latency, cache the
-        # files mounted at the recipient's root by basename and silently drop
+    # tagged-id set per user with a short TTL (mirroring the
-        # legitimate ACL-aware-search results.
+    # list_accessible_owners cache in search/access_filter.py). Skipped here so
-        #
+    # an untag is reflected on the very next search rather than after a TTL.
-        # Hoisted cast mirrors _verify_notes: a malformed id keeps the result
+    async with semaphore:
-        # (fail open) with a specific log line rather than a generic
-        # "unexpected error" from the catch-all below.
         try:
-            file_id_int = int(doc_id)
+            tagged = await client.find_files_by_tag(
-        except (TypeError, ValueError) as e:
+                tag_name, mime_type_filter="application/pdf"
+            )
+        except HTTPStatusError as e:
             logger.warning(
-                "Non-numeric file id %r (%s): %s; keeping result",
+                "Transient error fetching %r-tagged files for verification: "
-                doc_id,
+                "%s %s; keeping all file results",
-                file_path,
+                tag_name,
+                e.response.status_code,
                 e,
             )
+            return {r.id for r in results}
+        except Exception as e:
+            logger.warning(
+                "Unexpected error fetching %r-tagged files for verification: "
+                "%s; keeping all file results",
+                tag_name,
+                e,
+            )
+            return {r.id for r in results}
+
+        # Exclusion wins: a tagged file under an EXCLUDED_TAGS folder must not
+        # surface, matching the scanner's defense-in-depth filter. A failure
+        # here degrades to "no exclusion" rather than dropping legitimate hits.
+        try:
+            excluded_paths = await get_excluded_file_paths(client.webdav)
+        except Exception as e:
+            logger.warning(
+                "EXCLUDED_TAGS lookup failed during verification (%s); "
+                "proceeding without exclusion filter",
+                e,
+            )
+            excluded_paths = set()
+
+    tagged_ids: set[str] = set()
+    for f in tagged:
+        file_id = f.get("id")
+        if file_id is None:
+            continue
+        if excluded_paths and is_path_excluded(f.get("path", ""), excluded_paths):
+            continue
+        # Normalise to str — Qdrant doc_id payload is keyword-indexed and the
+        # scanner stringifies file ids on write, so SearchResult.id is a str.
+        tagged_ids.add(str(file_id))
+
+    accessible: set[str] = set()
+    for r in results:
+        doc_id = r.id
+        if doc_id in tagged_ids:
             accessible.add(doc_id)
-            return
+        elif not is_valid_nextcloud_doc_id(doc_id):
-
+            logger.warning(
-        async with semaphore:
+                "Malformed file doc_id %r in verifier; keeping to avoid "
-            try:
+                "dropping a potentially legitimate result (cannot match "
-                if await client.webdav.file_accessible_by_id(file_id_int):
+                "against the numeric tag REPORT)",
-                    accessible.add(doc_id)
+                doc_id,
-                # else: definitively inaccessible (not owned, not shared) —
+            )
-                # drop and let the caller schedule eviction.
+            accessible.add(doc_id)
-            except HTTPStatusError as e:
+        # else: a valid file id absent from the tagged set is untagged/deleted/
-                if _is_definitive_404_or_403(e):
+        # excluded — drop it and let the caller schedule eviction.
-                    return
-                logger.warning(
-                    "Transient error verifying file %s (%s): %s %s; keeping result",
-                    doc_id,
-                    file_path,
-                    e.response.status_code,
-                    e,
-                )
-                accessible.add(doc_id)
-            except Exception as e:
-                # Network blip / unexpected WebDAV error — ambiguous, not a
-                # definitive denial. Keep the result; the next query re-verifies.
-                logger.warning(
-                    "Unexpected error verifying file %s (%s): %s; keeping result",
-                    doc_id,
-                    file_path,
-                    e,
-                )
-                accessible.add(doc_id)
-
-    async with anyio.create_task_group() as tg:
-        for r in results:
-            tg.start_soon(check, r)
-
     return accessible
 
 

nextcloud_mcp_server/vector/scanner.py

@@ -4,7 +4,6 @@ Periodically scans enabled users' content and queues changed documents for proce
 """
 
 import logging
-import os
 import random
 import time
 from dataclasses import dataclass
@@ -396,7 +395,7 @@ async def scan_user_documents(
             # PDF descendants (Depth: infinity SEARCH), so a tag on a
             # folder applies to every PDF beneath it.
             settings = get_settings()
-            tag_name = os.getenv("VECTOR_SYNC_PDF_TAG", "vector-index")
+            tag_name = settings.vector_sync_pdf_tag
             tagged_files = await nc_client.find_files_by_tag(
                 tag_name, mime_type_filter="application/pdf"
             )

tests/integration/test_acl_shared_search.py

@@ -54,6 +54,16 @@ def _reset_owners_cache():
 
 
 _DOC_TEXT = "Confidential quarterly infrastructure budget and capacity plan"
+# Minimal valid PDF. verify-on-read gates file results on the vector-index tag
+# via find_files_by_tag(..., mime_type_filter="application/pdf"), so the shared
+# file must be a PDF (matching what the scanner actually indexes), not a .txt.
+_PDF_BYTES = (
+    b"%PDF-1.4\n"
+    b"1 0 obj<</Type/Catalog/Pages 2 0 R>>endobj\n"
+    b"2 0 obj<</Type/Pages/Kids[3 0 R]/Count 1>>endobj\n"
+    b"3 0 obj<</Type/Page/Parent 2 0 R/MediaBox[0 0 200 200]>>endobj\n"
+    b"trailer<</Root 1 0 R>>\n%%EOF\n"
+)
 
 
 def _user_client(username: str, password: str) -> NextcloudClient:
@@ -81,7 +91,13 @@ async def acl_users(test_users_setup):
 
 @pytest.fixture
 async def shared_file(acl_users):
-    """alice creates a nested file and shares it with bob (not diana).
+    """alice creates a nested PDF, tags it ``vector-index``, and shares it with
+    bob (not diana).
+
+    The vector-index tag is required because verify-on-read now gates file
+    results on current tag membership (in addition to ACL access). The tag is
+    created userVisible so the owner's assignment surfaces in the recipient's
+    systemtag REPORT — this fixture is the live check of that assumption.
 
     Yields (file_id, owner_relative_path); cleans up the directory after.
     """
@@ -89,18 +105,28 @@ async def shared_file(acl_users):
     suffix = uuid.uuid4().hex[:8]
     test_dir = f"acl_e2e_{suffix}"
     nested = f"{test_dir}/reports"
-    path = f"{nested}/budget.txt"
+    path = f"{nested}/budget.pdf"
 
     await alice.webdav.create_directory(test_dir)
     await alice.webdav.create_directory(nested)
-    await alice.webdav.write_file(path, _DOC_TEXT.encode(), "text/plain")
+    await alice.webdav.write_file(path, _PDF_BYTES, "application/pdf")
     file_id = (await alice.webdav.get_file_info(path))["id"]
+    tag = await alice.webdav.get_or_create_tag(
+        name=get_settings().vector_sync_pdf_tag,
+        user_visible=True,
+        user_assignable=True,
+    )
+    await alice.webdav.assign_tag_to_file(file_id, tag["id"])
     await alice.sharing.create_share(
         path=f"/{path}", share_with="bob", share_type=0, permissions=1
     )
     try:
         yield file_id, path
     finally:
+        try:
+            await alice.webdav.remove_tag_from_file(file_id, tag["id"])
+        except Exception:
+            pass
         await alice.webdav.delete_resource(test_dir)
 
 
@@ -132,7 +158,7 @@ async def seeded_semantic(monkeypatch, shared_file):
                     "user_id": "alice",
                     "is_placeholder": False,
                     "file_path": path,
-                    "title": "budget.txt",
+                    "title": "budget.pdf",
                     "excerpt": _DOC_TEXT,
                     "chunk_index": 0,
                     "total_chunks": 1,
@@ -180,7 +206,13 @@ async def _search_as(user_client, file_id_unused) -> list:
 async def test_recipient_finds_shared_file_without_indexing(acl_users, seeded_semantic):
     """Bob finds alice's shared file end-to-end: real share lookup expands his
     accessible owners to include alice, the filter surfaces her point, and
-    real verification confirms his ACL access — all without bob indexing."""
+    real verification confirms both his ACL access AND that the file is still
+    in the vector-index tag set — all without bob indexing.
+
+    This also exercises the strict tag-gate's key assumption: a vector-index
+    tag alice assigned (userVisible) surfaces in bob's systemtag REPORT for a
+    file shared into his tree. If a future Nextcloud version stops surfacing an
+    owner's tag to a recipient, this assertion is where it fails first."""
     file_id = seeded_semantic
     # Sanity: the live OCS lookup really does expand bob to include alice.
     owners = await list_accessible_owners(acl_users["bob"].sharing, "bob")

tests/integration/test_verify_on_read.py

@@ -5,16 +5,16 @@ instance — the verification path's whole purpose is to consult Nextcloud as
 the source of truth, so unit-level mocks don't catch protocol or status-code
 mismatches between our verifier and the real API.
 
-**Coverage**: only the ``note`` verifier is exercised against real Nextcloud
+**Coverage**: the ``note`` verifier and the ``file`` verifier (tag-membership
-here. The ``file`` (WebDAV PROPFIND), ``deck_card`` (Deck app), and
+gate, see the shared-recipient tests below) are exercised against real
-``news_item`` (News app) verifiers are unit-tested with mocked HTTP
+Nextcloud here. The ``deck_card`` (Deck app) and ``news_item`` (News app)
-responses in ``tests/unit/search/test_verification.py``. Adding integration
+verifiers are unit-tested with mocked HTTP responses in
-coverage for those types is tracked as a follow-up — it requires fixture
+``tests/unit/search/test_verification.py``. Adding integration coverage for
-data (tagged PDFs in user files, a Deck board with cards, a News feed) that
+those types is tracked as a follow-up — it requires fixture data (a Deck board
-is non-trivial to seed from CI. The mocked unit tests are accurate for
+with cards, a News feed) that is non-trivial to seed from CI. The mocked unit
-status-code semantics but won't catch payload-shape regressions in those
+tests are accurate for status-code semantics but won't catch payload-shape
-Nextcloud apps; the trade-off is documented here so future readers know
+regressions in those Nextcloud apps; the trade-off is documented here so
-which suite owns which verifier.
+future readers know which suite owns which verifier.
 
 Qdrant is mocked out (``delete_document_points`` and the payload-resolution
 helpers) so these tests don't require a running vector database. The unit
@@ -30,6 +30,7 @@ import pytest
 from httpx import BasicAuth, HTTPStatusError
 
 from nextcloud_mcp_server.client import NextcloudClient
+from nextcloud_mcp_server.config import get_settings
 from nextcloud_mcp_server.search import verification
 from nextcloud_mcp_server.search.algorithms import SearchResult
 from nextcloud_mcp_server.search.verification import verify_search_results
@@ -38,6 +39,17 @@ logger = logging.getLogger(__name__)
 
 pytestmark = pytest.mark.integration
 
+# Minimal valid PDF — the file verifier gates on the vector-index tag via
+# find_files_by_tag(..., mime_type_filter="application/pdf"), so file fixtures
+# must be PDFs (matching what the scanner indexes), not .txt.
+_PDF_BYTES = (
+    b"%PDF-1.4\n"
+    b"1 0 obj<</Type/Catalog/Pages 2 0 R>>endobj\n"
+    b"2 0 obj<</Type/Pages/Kids[3 0 R]/Count 1>>endobj\n"
+    b"3 0 obj<</Type/Page/Parent 2 0 R/MediaBox[0 0 200 200]>>endobj\n"
+    b"trailer<</Root 1 0 R>>\n%%EOF\n"
+)
+
 
 def _result_for_note(note_id: int) -> SearchResult:
     return SearchResult(
@@ -51,9 +63,10 @@ def _result_for_note(note_id: int) -> SearchResult:
 
 def _result_for_file(file_id: int, path: str) -> SearchResult:
     # Mirrors what the algorithm layer propagates: doc_id IS the global file id,
-    # ``path`` is carried in metadata (owner-relative) for log context only.
+    # stringified (SearchResult.id is always str), ``path`` is carried in
+    # metadata (owner-relative) for log context only.
     return SearchResult(
-        id=file_id,
+        id=str(file_id),
         doc_type="file",
         title=path.split("/")[-1],
         excerpt="...",
@@ -222,11 +235,13 @@ async def alice_bob_clients(test_users_setup):
 async def test_verify_keeps_nested_file_shared_with_recipient(
     alice_bob_clients, mocker
 ):
-    """The PR #813 acceptance check at the verifier layer.
+    """The PR #813 acceptance check at the verifier layer, under tag-gating.
 
-    Alice owns a file in a *subfolder* and shares it with Bob. Verifying the
+    Alice owns a PDF in a *subfolder*, tags it ``vector-index`` (userVisible),
-    result as Bob must KEEP it — proving the id-based check sees the share.
+    and shares it with Bob. Verifying the result as Bob must KEEP it — proving
-    A path-based check (the old behaviour) would 404 here and wrongly drop it.
+    the tag REPORT surfaces an owner-assigned tag on a file shared into Bob's
+    tree. If a future Nextcloud version stops surfacing the owner's tag to a
+    recipient, this is where strict tag-gating regresses shared search.
     """
     spy_evict = mocker.AsyncMock()
     mocker.patch.object(verification, "delete_document_points", spy_evict)
@@ -235,12 +250,18 @@ async def test_verify_keeps_nested_file_shared_with_recipient(
     suffix = uuid.uuid4().hex[:8]
     test_dir = f"acl_verify_{suffix}"
     nested_dir = f"{test_dir}/reports"
-    shared_path = f"{nested_dir}/shared.txt"
+    shared_path = f"{nested_dir}/shared.pdf"
 
     await alice.webdav.create_directory(test_dir)
     await alice.webdav.create_directory(nested_dir)
-    await alice.webdav.write_file(shared_path, b"alice's shared report", "text/plain")
+    await alice.webdav.write_file(shared_path, _PDF_BYTES, "application/pdf")
     file_id = (await alice.webdav.get_file_info(shared_path))["id"]
+    tag = await alice.webdav.get_or_create_tag(
+        name=get_settings().vector_sync_pdf_tag,
+        user_visible=True,
+        user_assignable=True,
+    )
+    await alice.webdav.assign_tag_to_file(file_id, tag["id"])
 
     await alice.sharing.create_share(
         path=f"/{shared_path}", share_with="bob", share_type=0, permissions=1
@@ -251,18 +272,23 @@ async def test_verify_keeps_nested_file_shared_with_recipient(
             bob, [_result_for_file(file_id, shared_path)]
         )
 
-        assert [r.id for r in kept] == [file_id], (
+        assert [r.id for r in kept] == [str(file_id)], (
-            "a nested file shared with bob must pass verification for bob"
+            "a nested tagged PDF shared with bob must pass verification for bob"
         )
         assert dropped_count == 0
         spy_evict.assert_not_awaited()
     finally:
+        try:
+            await alice.webdav.remove_tag_from_file(file_id, tag["id"])
+        except Exception:
+            pass
         await alice.webdav.delete_resource(test_dir)
 
 
 async def test_verify_drops_unshared_file_for_other_user(alice_bob_clients, mocker):
-    """Negative control: a file Alice did NOT share is inaccessible to Bob and
+    """Negative control: a file Alice did NOT share is absent from Bob's
-    must be dropped + scheduled for eviction under his identity."""
+    vector-index tag set (and his tree), so it must be dropped + scheduled for
+    eviction under his identity."""
     spy_evict = mocker.AsyncMock()
     mocker.patch.object(verification, "delete_document_points", spy_evict)
 
@@ -282,6 +308,6 @@ async def test_verify_drops_unshared_file_for_other_user(alice_bob_clients, mock
 
         assert kept == [], "an unshared file must not pass verification for bob"
         assert dropped_count == 1
-        spy_evict.assert_awaited_once_with(file_id, "file", bob.username)
+        spy_evict.assert_awaited_once_with(str(file_id), "file", bob.username)
     finally:
         await alice.webdav.delete_resource(test_dir)

tests/unit/search/test_verification.py

@@ -437,141 +437,135 @@ async def test_verify_news_items_malformed_api_response_keeps_all(mocker):
 # ---------------------------------------------------------------------------
 
 
+def _patch_excluded(mocker, paths: set[str] | None = None, *, side_effect=None):
+    """Patch the lazily-imported EXCLUDED_TAGS lookup used by _verify_files."""
+    if side_effect is not None:
+        mock = mocker.AsyncMock(side_effect=side_effect)
+    else:
+        mock = mocker.AsyncMock(return_value=paths if paths is not None else set())
+    return mocker.patch(
+        "nextcloud_mcp_server.server.tag_exclusion.get_excluded_file_paths", mock
+    )
+
+
+def _file_client(mocker, *, tagged=None, find_side_effect=None, username="alice"):
+    """Build a client whose find_files_by_tag returns the given tagged files."""
+    if find_side_effect is not None:
+        find = mocker.AsyncMock(side_effect=find_side_effect)
+    else:
+        find = mocker.AsyncMock(return_value=tagged if tagged is not None else [])
+    return SimpleNamespace(
+        find_files_by_tag=find,
+        webdav=SimpleNamespace(),
+        username=username,
+    )
+
+
 @pytest.mark.unit
-async def test_verify_files_accessible_by_global_id_is_kept(mocker):
+async def test_verify_files_tagged_is_kept(mocker):
-    """File verifier resolves the file by its global ID (the doc_id), ACL-aware.
+    """A file currently carrying the vector-index tag is kept, and the tagged
+    set is fetched with a single batch call (not one per result)."""
+    _patch_excluded(mocker)
+    client = _file_client(mocker, tagged=[{"id": 100, "path": "/Documents/foo.pdf"}])
 
-    This is what lets a recipient verify a file an owner shared with them:
+    result = await _verify_files(client, [_make_result(100, doc_type="file")], _sem())
-    file_accessible_by_id searches the user's whole tree (incl. mounted
-    shares) by global file id, not a path under the caller's own root (which
-    would 404 on shared files mounted at a different path).
-    """
-    webdav_client = SimpleNamespace(
-        file_accessible_by_id=mocker.AsyncMock(return_value=True)
-    )
-    client = SimpleNamespace(webdav=webdav_client, username="alice")
-
-    result = await _verify_files(
-        client,
-        [_make_result(100, doc_type="file", metadata={"path": "Documents/foo.txt"})],
-        _sem(),
-    )
 
     assert result == {"100"}
-    webdav_client.file_accessible_by_id.assert_awaited_once_with(100)
+    client.find_files_by_tag.assert_awaited_once_with(
+        "vector-index", mime_type_filter="application/pdf"
+    )
 
 
 @pytest.mark.unit
-async def test_verify_files_inaccessible_id_drops(mocker):
+async def test_verify_files_untagged_drops(mocker):
-    """file_accessible_by_id returning False (file not in the user's tree) is a
+    """A file removed from the vector-index tag (absent from the tagged set) is
-    definitive drop — the file is neither owned by nor shared with the user."""
+    dropped even though it may still exist and be readable by the user."""
-    webdav_client = SimpleNamespace(
+    _patch_excluded(mocker)
-        file_accessible_by_id=mocker.AsyncMock(return_value=False)
+    client = _file_client(mocker, tagged=[{"id": 100, "path": "/Documents/foo.pdf"}])
-    )
-    client = SimpleNamespace(webdav=webdav_client, username="alice")
 
     result = await _verify_files(
         client,
-        [_make_result(123, doc_type="file", metadata={"path": "gone.txt"})],
+        [_make_result(100, doc_type="file"), _make_result(200, doc_type="file")],
         _sem(),
     )
 
+    # 100 is still tagged → kept; 200 was untagged → dropped.
+    assert result == {"100"}
+
+
+@pytest.mark.unit
+async def test_verify_files_deleted_drops(mocker):
+    """A deleted file is absent from the tagged set → dropped (caller evicts)."""
+    _patch_excluded(mocker)
+    client = _file_client(mocker, tagged=[])
+
+    result = await _verify_files(client, [_make_result(123, doc_type="file")], _sem())
+
     assert result == set()
 
 
 @pytest.mark.unit
-async def test_verify_files_403_404_drops(mocker):
+async def test_verify_files_excluded_path_drops(mocker):
-    """A 403/404 raised by the SEARCH call is treated as a definitive drop,
+    """A tagged file under an EXCLUDED_TAGS folder must not surface — exclusion
-    consistent with the shared _is_definitive_404_or_403 policy used by every
+    wins, parity with the scanner's defense-in-depth filter."""
-    verifier. (Normal inaccessibility surfaces as an empty result set, not a
+    # get_excluded_file_paths returns slash-stripped (normalised) paths.
-    status code, and is covered by test_verify_files_inaccessible_id_drops.)"""
+    _patch_excluded(mocker, {"Secret"})
-    for status in (403, 404):
+    client = _file_client(
-        webdav_client = SimpleNamespace(
+        mocker,
-            file_accessible_by_id=mocker.AsyncMock(side_effect=_http_error(status))
+        tagged=[
-        )
+            {"id": 100, "path": "/Documents/foo.pdf"},
-        client = SimpleNamespace(webdav=webdav_client, username="alice")
+            {"id": 200, "path": "/Secret/bar.pdf"},
+        ],
+    )
 
+    result = await _verify_files(
+        client,
+        [_make_result(100, doc_type="file"), _make_result(200, doc_type="file")],
+        _sem(),
+    )
+
+    assert result == {"100"}
+
+
+@pytest.mark.unit
+async def test_verify_files_tag_fetch_failure_keeps_all(mocker):
+    """If the tag REPORT itself fails (HTTP or otherwise), keep every file
+    result (fail-open) — never silently shrink results on a backend blip."""
+    _patch_excluded(mocker)
+    for exc in (_http_error(503), _http_error(429), RuntimeError("dav blew up")):
+        client = _file_client(mocker, find_side_effect=exc)
         result = await _verify_files(
             client,
-            [_make_result(124, doc_type="file", metadata={"path": "x.txt"})],
+            [_make_result(7, doc_type="file"), _make_result(8, doc_type="file")],
             _sem(),
         )
-
+        assert result == {"7", "8"}, f"{exc!r} on the tag fetch must keep all results"
-        assert result == set(), f"{status} on the SEARCH call must drop"
 
 
 @pytest.mark.unit
-async def test_verify_files_non_numeric_id_keeps_unverified(mocker):
+async def test_verify_files_exclusion_lookup_failure_proceeds(mocker):
-    """Without a numeric file id we cannot verify — fail open, don't drop."""
+    """If the EXCLUDED_TAGS lookup fails, proceed without the exclusion filter
-    webdav_client = SimpleNamespace(
+    rather than dropping legitimate tagged hits."""
-        file_accessible_by_id=mocker.AsyncMock(
+    _patch_excluded(mocker, side_effect=RuntimeError("ocs down"))
-            side_effect=AssertionError("must not be called")
+    client = _file_client(mocker, tagged=[{"id": 100, "path": "/Documents/foo.pdf"}])
-        )
+
-    )
+    result = await _verify_files(client, [_make_result(100, doc_type="file")], _sem())
-    client = SimpleNamespace(webdav=webdav_client, username="alice")
+
+    assert result == {"100"}
+
+
+@pytest.mark.unit
+async def test_verify_files_non_numeric_id_keeps(mocker):
+    """A malformed (non-numeric) doc_id cannot be matched against the numeric
+    tag REPORT, so it is kept (defense-in-depth, false-positive preferred)."""
+    _patch_excluded(mocker)
+    client = _file_client(mocker, tagged=[])
 
     result = await _verify_files(
-        client,
+        client, [_make_result("not-a-file-id", doc_type="file")], _sem()
-        [_make_result("not-a-file-id", doc_type="file", metadata={"path": "x.txt"})],
-        _sem(),
     )
+
     assert result == {"not-a-file-id"}
-    webdav_client.file_accessible_by_id.assert_not_awaited()
-
-
-@pytest.mark.unit
-async def test_verify_files_transient_5xx_keeps(mocker):
-    webdav_client = SimpleNamespace(
-        file_accessible_by_id=mocker.AsyncMock(side_effect=_http_error(503))
-    )
-    client = SimpleNamespace(webdav=webdav_client, username="alice")
-
-    result = await _verify_files(
-        client,
-        [_make_result(7, doc_type="file", metadata={"path": "x.txt"})],
-        _sem(),
-    )
-
-    assert result == {"7"}
-
-
-@pytest.mark.unit
-async def test_verify_files_429_keeps_as_transient(mocker):
-    """HTTP 429 from the SEARCH call must NOT silently drop file results."""
-    webdav_client = SimpleNamespace(
-        file_accessible_by_id=mocker.AsyncMock(side_effect=_http_error(429))
-    )
-    client = SimpleNamespace(webdav=webdav_client, username="alice")
-
-    result = await _verify_files(
-        client,
-        [_make_result(7, doc_type="file", metadata={"path": "x.txt"})],
-        _sem(),
-    )
-
-    assert result == {"7"}
-
-
-@pytest.mark.unit
-async def test_verify_files_unexpected_exception_keeps(mocker):
-    """A non-HTTP exception from file_accessible_by_id must not drop the result.
-
-    The catch-all ``except Exception`` branch in the file verifier exists
-    so a bug in the WebDAV client (or an httpx ConnectError on a flaky
-    network) cannot silently shrink result pages.
-    """
-    webdav_client = SimpleNamespace(
-        file_accessible_by_id=mocker.AsyncMock(side_effect=RuntimeError("dav blew up"))
-    )
-    client = SimpleNamespace(webdav=webdav_client, username="alice")
-
-    result = await _verify_files(
-        client,
-        [_make_result(8, doc_type="file", metadata={"path": "y.txt"})],
-        _sem(),
-    )
-
-    assert result == {"8"}
 
 
 # ---------------------------------------------------------------------------
@@ -889,11 +883,11 @@ async def test_verify_evicts_cross_user_file_under_querying_user_id(mocker):
     """
     spy_evict = mocker.AsyncMock()
     mocker.patch.object(verification, "delete_document_points", spy_evict)
+    _patch_excluded(mocker)
 
-    webdav_client = SimpleNamespace(
+    # The shared file is no longer in bob's tagged set (share revoked → absent
-        file_accessible_by_id=mocker.AsyncMock(return_value=False)
+    # from his vector-index tag REPORT), so the file verifier drops it.
-    )
+    client = _file_client(mocker, tagged=[], username="bob")
-    client = SimpleNamespace(webdav=webdav_client, username="bob")
 
     kept, dropped_count = await verify_search_results(
         client,