From 327d843f643dfad9416f334a983d04ff67a31929 Mon Sep 17 00:00:00 2001
From: Chris Coutinho <chris@coutinho.io>
Date: Thu, 20 Nov 2025 11:22:20 +0100
Subject: [PATCH] feat: Implement per-chunk vector visualization with context
 expansion
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Major improvements to vector visualization page:
- Refactor PCA to display individual chunks instead of averaged documents
- Add context expansion module for fetching surrounding text from notes and PDFs
- Update deduplication to use (doc_id, doc_type, chunk_start, chunk_end) keys
- Fix Alpine.js rendering with chunk-specific keys including offsets
- Refactor authentication helper to return NextcloudClient for better reuse
- Add async context manager support to NextcloudClient

Technical details:
- viz_routes.py: Fetch specific chunk vectors instead of averaging per document
- context.py: New module supporting both notes and PDF text extraction via PyMuPDF
- search algorithms: Extract page_number, chunk_index, total_chunks from Qdrant
- vector-viz.js/html: Use chunk positions in expansion tracking keys

This enables users to see which specific chunks match their query
and view them with surrounding context in the PCA visualization.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
---
 .../auth/static/vector-viz.js                 |   2 +-
 .../auth/templates/vector_viz.html            |  14 +-
 nextcloud_mcp_server/auth/userinfo_routes.py  |  45 +--
 nextcloud_mcp_server/auth/viz_routes.py       | 251 ++++++++---------
 nextcloud_mcp_server/client/__init__.py       |   9 +
 nextcloud_mcp_server/models/semantic.py       |  23 ++
 nextcloud_mcp_server/search/algorithms.py     |   6 +
 nextcloud_mcp_server/search/bm25_hybrid.py    |  21 +-
 nextcloud_mcp_server/search/context.py        | 265 ++++++++++++++++++
 nextcloud_mcp_server/search/semantic.py       |  21 +-
 10 files changed, 485 insertions(+), 172 deletions(-)
 create mode 100644 nextcloud_mcp_server/search/context.py

diff --git a/nextcloud_mcp_server/auth/static/vector-viz.js b/nextcloud_mcp_server/auth/static/vector-viz.js
index c01c1e7..f59f46c 100644
--- a/nextcloud_mcp_server/auth/static/vector-viz.js
+++ b/nextcloud_mcp_server/auth/static/vector-viz.js
@@ -217,7 +217,7 @@ function vizApp() {
         },
 
         async toggleChunk(result) {
-            const resultKey = `${result.doc_type}_${result.id}`;
+            const resultKey = `${result.doc_type}_${result.id}_${result.chunk_start_offset || 0}`;
 
             if (this.isChunkExpanded(resultKey)) {
                 delete this.expandedChunks[resultKey];
diff --git a/nextcloud_mcp_server/auth/templates/vector_viz.html b/nextcloud_mcp_server/auth/templates/vector_viz.html
index a052d9e..214b582 100644
--- a/nextcloud_mcp_server/auth/templates/vector_viz.html
+++ b/nextcloud_mcp_server/auth/templates/vector_viz.html
@@ -117,7 +117,7 @@
 
         <template x-if="!loading && results.length > 0">
             <div x-transition.opacity.duration.200ms>
-                <template x-for="result in results" :key="result.id">
+                <template x-for="result in results" :key="`${result.doc_type}_${result.id}_${result.chunk_start_offset || 0}`">
                     <div style="padding: 12px; border-bottom: 1px solid #eee;">
                         <a :href="getNextcloudUrl(result)" target="_blank" style="font-weight: 500; color: #0066cc; text-decoration: none;">
                             <span x-text="result.title"></span>
@@ -134,22 +134,22 @@
                             <button
                                 class="chunk-toggle-btn"
                                 @click="toggleChunk(result)"
-                                x-text="isChunkExpanded(`${result.doc_type}_${result.id}`) ? 'Hide Chunk' : 'Show Chunk'"
+                                x-text="isChunkExpanded(`${result.doc_type}_${result.id}_${result.chunk_start_offset || 0}`) ? 'Hide Chunk' : 'Show Chunk'"
                             ></button>
                         </template>
 
                         <!-- Chunk context (expanded inline) -->
-                        <template x-if="isChunkExpanded(`${result.doc_type}_${result.id}`)">
+                        <template x-if="isChunkExpanded(`${result.doc_type}_${result.id}_${result.chunk_start_offset || 0}`)">
                             <div class="chunk-context" x-transition.opacity.duration.200ms>
-                                <template x-if="chunkLoading[`${result.doc_type}_${result.id}`]">
+                                <template x-if="chunkLoading[`${result.doc_type}_${result.id}_${result.chunk_start_offset || 0}`]">
                                     <div style="color: #666; font-style: italic;">Loading chunk...</div>
                                 </template>
-                                <template x-if="!chunkLoading[`${result.doc_type}_${result.id}`]">
+                                <template x-if="!chunkLoading[`${result.doc_type}_${result.id}_${result.chunk_start_offset || 0}`]">
                                     <div>
-                                        <template x-if="expandedChunks[`${result.doc_type}_${result.id}`]?.has_more_before">
+                                        <template x-if="expandedChunks[`${result.doc_type}_${result.id}_${result.chunk_start_offset || 0}`]?.has_more_before">
                                             <span class="chunk-ellipsis">...</span>
                                         </template>
-                                        <span class="chunk-text" x-text="expandedChunks[`${result.doc_type}_${result.id}`]?.before_context"></span><span class="chunk-matched" x-text="expandedChunks[`${result.doc_type}_${result.id}`]?.chunk_text"></span><span class="chunk-text" x-text="expandedChunks[`${result.doc_type}_${result.id}`]?.after_context"></span><template x-if="expandedChunks[`${result.doc_type}_${result.id}`]?.has_more_after">
+                                        <span class="chunk-text" x-text="expandedChunks[`${result.doc_type}_${result.id}_${result.chunk_start_offset || 0}`]?.before_context"></span><span class="chunk-matched" x-text="expandedChunks[`${result.doc_type}_${result.id}_${result.chunk_start_offset || 0}`]?.chunk_text"></span><span class="chunk-text" x-text="expandedChunks[`${result.doc_type}_${result.id}_${result.chunk_start_offset || 0}`]?.after_context"></span><template x-if="expandedChunks[`${result.doc_type}_${result.id}_${result.chunk_start_offset || 0}`]?.has_more_after">
                                             <span class="chunk-ellipsis">...</span>
                                         </template>
                                     </div>
diff --git a/nextcloud_mcp_server/auth/userinfo_routes.py b/nextcloud_mcp_server/auth/userinfo_routes.py
index 4a015da..bfe7408 100644
--- a/nextcloud_mcp_server/auth/userinfo_routes.py
+++ b/nextcloud_mcp_server/auth/userinfo_routes.py
@@ -18,6 +18,8 @@ from starlette.authentication import requires
 from starlette.requests import Request
 from starlette.responses import HTMLResponse, JSONResponse
 
+from nextcloud_mcp_server.client import NextcloudClient
+
 logger = logging.getLogger(__name__)
 
 # Setup Jinja2 environment for templates
@@ -25,14 +27,20 @@ _template_dir = Path(__file__).parent / "templates"
 _jinja_env = Environment(loader=FileSystemLoader(_template_dir))
 
 
-async def _get_authenticated_client_for_userinfo(request: Request) -> httpx.AsyncClient:
-    """Get an authenticated HTTP client for user info page operations.
+async def _get_authenticated_client_for_userinfo(request: Request) -> NextcloudClient:
+    """Get an authenticated Nextcloud client for user info page operations.
+
+    This is a shared helper for authenticated routes that need to access
+    Nextcloud APIs. It handles both BasicAuth and OAuth authentication modes.
 
     Args:
         request: Starlette request object
 
     Returns:
-        Authenticated httpx.AsyncClient
+        Authenticated NextcloudClient
+
+    Raises:
+        RuntimeError: If credentials/session not configured
     """
     oauth_ctx = getattr(request.app.state, "oauth_context", None)
 
@@ -45,11 +53,15 @@ async def _get_authenticated_client_for_userinfo(request: Request) -> httpx.Asyn
         if not all([nextcloud_host, username, password]):
             raise RuntimeError("BasicAuth credentials not configured")
 
-        assert nextcloud_host is not None  # Type narrowing for type checker
-        return httpx.AsyncClient(
+        from httpx import BasicAuth
+
+        assert nextcloud_host is not None
+        assert username is not None
+        assert password is not None
+        return NextcloudClient(
             base_url=nextcloud_host,
-            auth=(username, password),
-            timeout=30.0,
+            username=username,
+            auth=BasicAuth(username, password),
         )
 
     # OAuth mode - get token from session
@@ -64,15 +76,14 @@ async def _get_authenticated_client_for_userinfo(request: Request) -> httpx.Asyn
         raise RuntimeError("No access token found in session")
 
     access_token = token_data["access_token"]
+    username = token_data.get("username")
     nextcloud_host = oauth_ctx.get("config", {}).get("nextcloud_host", "")
 
-    if not nextcloud_host:
-        raise RuntimeError("Nextcloud host not configured")
+    if not nextcloud_host or not username:
+        raise RuntimeError("Nextcloud host or username not configured")
 
-    return httpx.AsyncClient(
-        base_url=nextcloud_host,
-        headers={"Authorization": f"Bearer {access_token}"},
-        timeout=30.0,
+    return NextcloudClient.from_token(
+        base_url=nextcloud_host, token=access_token, username=username
     )
 
 
@@ -423,10 +434,10 @@ async def user_info_html(request: Request) -> HTMLResponse:
     try:
         from nextcloud_mcp_server.auth.permissions import is_nextcloud_admin
 
-        # Get authenticated HTTP client
-        http_client = await _get_authenticated_client_for_userinfo(request)
-        is_admin = await is_nextcloud_admin(request, http_client)
-        await http_client.aclose()
+        # Get authenticated Nextcloud client
+        nc_client = await _get_authenticated_client_for_userinfo(request)
+        is_admin = await is_nextcloud_admin(request, nc_client._client)
+        await nc_client.close()
     except Exception as e:
         logger.warning(f"Failed to check admin status: {e}")
         # Default to not admin if check fails
diff --git a/nextcloud_mcp_server/auth/viz_routes.py b/nextcloud_mcp_server/auth/viz_routes.py
index e1f2e4e..1599073 100644
--- a/nextcloud_mcp_server/auth/viz_routes.py
+++ b/nextcloud_mcp_server/auth/viz_routes.py
@@ -138,7 +138,7 @@ async def vector_visualization_search(request: Request) -> JSONResponse:
             _get_authenticated_client_for_userinfo,
         )
 
-        async with await _get_authenticated_client_for_userinfo(request) as http_client:  # noqa: F841
+        async with await _get_authenticated_client_for_userinfo(request) as nc_client:  # noqa: F841
             # Create search algorithm (no client needed - verification removed)
             if algorithm == "semantic":
                 search_algo = SemanticSearchAlgorithm(score_threshold=score_threshold)
@@ -217,72 +217,75 @@ async def vector_visualization_search(request: Request) -> JSONResponse:
                 }
             )
 
-        # Fetch vectors for matching results from Qdrant
+        # Fetch vectors for specific matching chunks from Qdrant
         vector_fetch_start = time.perf_counter()
         qdrant_client = await get_qdrant_client()
-        doc_ids = [r.id for r in search_results]
 
-        # Retrieve vectors for the matching documents
-        from qdrant_client.models import FieldCondition, Filter, MatchAny
+        # Build filters for each specific chunk
+        from qdrant_client.models import FieldCondition, Filter, MatchValue
 
-        points_response = await qdrant_client.scroll(
-            collection_name=settings.get_collection_name(),
-            scroll_filter=Filter(
-                must=[
+        chunk_vectors_map = {}  # Map (doc_id, chunk_start, chunk_end) -> vector
+
+        # Fetch vectors in batches by filtering on chunk-specific fields
+        for result in search_results:
+            chunk_start = result.chunk_start_offset
+            chunk_end = result.chunk_end_offset
+
+            # Build filter for this specific chunk
+            must_conditions = [
+                FieldCondition(
+                    key="doc_id",
+                    match=MatchValue(value=str(result.id)),
+                ),
+                FieldCondition(
+                    key="user_id",
+                    match=MatchValue(value=username),
+                ),
+            ]
+
+            # Add chunk position filters if available
+            if chunk_start is not None:
+                must_conditions.append(
                     FieldCondition(
-                        key="doc_id",
-                        match=MatchAny(any=[str(doc_id) for doc_id in doc_ids]),
-                    ),
+                        key="chunk_start_offset",
+                        match=MatchValue(value=chunk_start),
+                    )
+                )
+            if chunk_end is not None:
+                must_conditions.append(
                     FieldCondition(
-                        key="user_id",
-                        match={"value": username},
-                    ),
-                ]
-            ),
-            limit=len(doc_ids) * 2,  # Account for multiple chunks per doc
-            with_vectors=["dense"],  # Only fetch dense vectors for visualization
-            with_payload=["doc_id"],  # Need doc_id to map vectors to results
-        )
+                        key="chunk_end_offset",
+                        match=MatchValue(value=chunk_end),
+                    )
+                )
 
-        points = points_response[0]
-
-        if not points:
-            return JSONResponse(
-                {
-                    "success": True,
-                    "results": [],
-                    "coordinates_2d": [],
-                    "message": "No vectors found for results",
-                }
+            # Fetch this specific chunk vector
+            points_response = await qdrant_client.scroll(
+                collection_name=settings.get_collection_name(),
+                scroll_filter=Filter(must=must_conditions),
+                limit=1,  # Only need the first match
+                with_vectors=["dense"],
+                with_payload=False,
             )
 
-        # Extract dense vectors and group by document
-        def extract_dense_vector(point):
-            if point.vector is None:
-                return None
-            # If named vectors (dict), extract "dense"
-            if isinstance(point.vector, dict):
-                return point.vector.get("dense")
-            # If unnamed vector (array), use directly
-            return point.vector
+            points = points_response[0]
+            if points:
+                # Extract dense vector
+                point = points[0]
+                if point.vector is not None:
+                    # If named vectors (dict), extract "dense"
+                    if isinstance(point.vector, dict):
+                        vector = point.vector.get("dense")
+                    else:
+                        vector = point.vector
 
-        # Group chunk vectors by doc_id
-        from collections import defaultdict
-
-        doc_chunks = defaultdict(list)
-        for point in points:
-            if point.payload:
-                # doc_id can be int (for notes) or str (for files - file path)
-                # Keep original type instead of forcing to int
-                doc_id = point.payload.get("doc_id", 0)
-                vector = extract_dense_vector(point)
-                if vector is not None:
-                    doc_chunks[doc_id].append(vector)
+                    chunk_key = (result.id, chunk_start, chunk_end)
+                    chunk_vectors_map[chunk_key] = vector
 
         vector_fetch_duration = time.perf_counter() - vector_fetch_start
 
-        if len(doc_chunks) < 2:
-            # Not enough documents for PCA
+        if len(chunk_vectors_map) < 2:
+            # Not enough chunks for PCA
             return JSONResponse(
                 {
                     "success": True,
@@ -298,15 +301,15 @@ async def vector_visualization_search(request: Request) -> JSONResponse:
                     ],
                     "coordinates_3d": [[0, 0, 0]] * len(search_results),
                     "query_coords": [0, 0, 0],
-                    "message": "Not enough documents for PCA",
+                    "message": "Not enough chunks for PCA",
                 }
             )
 
         # Detect embedding dimension from first available vector
         embedding_dim = None
-        for chunks in doc_chunks.values():
-            if chunks:
-                embedding_dim = len(chunks[0])
+        for vector in chunk_vectors_map.values():
+            if vector is not None:
+                embedding_dim = len(vector)
                 break
 
         if embedding_dim is None:
@@ -320,23 +323,21 @@ async def vector_visualization_search(request: Request) -> JSONResponse:
 
         logger.info(f"Detected embedding dimension: {embedding_dim}")
 
-        # Average chunk vectors per document to create document-level embeddings
-        # Maintain order of search_results for coordinate mapping
-        doc_vectors = []
+        # Build chunk vectors array in search_results order (1:1 mapping)
+        chunk_vectors = []
         for result in search_results:
-            if result.id in doc_chunks:
-                # Average all chunk embeddings for this document
-                chunk_vectors = np.array(doc_chunks[result.id])
-                avg_vector = np.mean(chunk_vectors, axis=0)
-                doc_vectors.append(avg_vector)
-                logger.debug(f"Doc {result.id}: averaged {len(chunk_vectors)} chunks")
+            chunk_key = (result.id, result.chunk_start_offset, result.chunk_end_offset)
+            if chunk_key in chunk_vectors_map:
+                chunk_vectors.append(chunk_vectors_map[chunk_key])
             else:
-                # Document not found in vectors (shouldn't happen)
-                logger.warning(f"Doc {result.id} not found in fetched vectors")
-                # Use zero vector as fallback with detected dimension
-                doc_vectors.append(np.zeros(embedding_dim))
+                # Chunk not found in vectors (shouldn't happen)
+                logger.warning(
+                    f"Chunk {chunk_key} not found in fetched vectors, using zero vector"
+                )
+                # Use zero vector as fallback
+                chunk_vectors.append(np.zeros(embedding_dim))
 
-        doc_vectors = np.array(doc_vectors)
+        chunk_vectors = np.array(chunk_vectors)
 
         # Generate query embedding for visualization
         query_embed_start = time.perf_counter()
@@ -348,9 +349,9 @@ async def vector_visualization_search(request: Request) -> JSONResponse:
 
         logger.info(f"Generated query embedding (dimension={len(query_embedding)})")
 
-        # Combine query vector with document vectors for PCA
+        # Combine query vector with chunk vectors for PCA
         # Query will be the last point in the array
-        all_vectors = np.vstack([doc_vectors, np.array([query_embedding])])
+        all_vectors = np.vstack([chunk_vectors, np.array([query_embedding])])
 
         # Normalize vectors to unit length (L2 normalization)
         # This is critical because Qdrant uses COSINE distance, which only measures
@@ -396,17 +397,12 @@ async def vector_visualization_search(request: Request) -> JSONResponse:
             # Replace NaN with 0 to allow JSON serialization
             coords_3d = np.nan_to_num(coords_3d, nan=0.0)
 
-        # Split query coords from document coords
+        # Split query coords from chunk coords
         # Round to 2 decimal places for cleaner display
         query_coords_3d = [
             round(float(x), 2) for x in coords_3d[-1]
         ]  # Last point is query
-        doc_coords_3d = coords_3d[:-1]  # All but last are documents
-
-        total_chunks = sum(len(chunks) for chunks in doc_chunks.values())
-        avg_chunks_per_doc = (
-            total_chunks / len(doc_vectors) if doc_vectors.size > 0 else 0
-        )
+        chunk_coords_3d = coords_3d[:-1]  # All but last are chunks
 
         logger.info(
             f"PCA explained variance: PC1={pca.explained_variance_ratio_[0]:.3f}, "
@@ -414,13 +410,14 @@ async def vector_visualization_search(request: Request) -> JSONResponse:
             f"PC3={pca.explained_variance_ratio_[2]:.3f}"
         )
         logger.info(
-            f"Embedding stats: documents={len(doc_vectors)}, "
-            f"total_chunks={total_chunks}, avg_chunks_per_doc={avg_chunks_per_doc:.1f}, "
-            f"query_dim={len(query_embedding)}, doc_vector_dim={doc_vectors.shape[1] if doc_vectors.size > 0 else 0}"
+            f"Embedding stats: chunks={len(chunk_vectors)}, "
+            f"query_dim={len(query_embedding)}, chunk_vector_dim={chunk_vectors.shape[1] if chunk_vectors.size > 0 else 0}"
         )
 
         # Coordinates already match search_results order (1:1 mapping)
-        result_coords = [[round(float(x), 2) for x in coord] for coord in doc_coords_3d]
+        result_coords = [
+            [round(float(x), 2) for x in coord] for coord in chunk_coords_3d
+        ]
 
         # Build response
         response_results = [
@@ -449,7 +446,7 @@ async def vector_visualization_search(request: Request) -> JSONResponse:
             f"vector_fetch={vector_fetch_duration * 1000:.1f}ms ({vector_fetch_duration / total_duration * 100:.1f}%), "
             f"query_embed={query_embed_duration * 1000:.1f}ms ({query_embed_duration / total_duration * 100:.1f}%), "
             f"pca={pca_duration * 1000:.1f}ms ({pca_duration / total_duration * 100:.1f}%), "
-            f"results={len(search_results)}, doc_vectors={len(doc_vectors)}"
+            f"results={len(search_results)}, chunk_vectors={len(chunk_vectors)}"
         )
 
         return JSONResponse(
@@ -470,7 +467,7 @@ async def vector_visualization_search(request: Request) -> JSONResponse:
                     "query_embed_ms": round(query_embed_duration * 1000, 2),
                     "pca_ms": round(pca_duration * 1000, 2),
                     "num_results": len(search_results),
-                    "num_doc_vectors": len(doc_vectors),
+                    "num_chunk_vectors": len(chunk_vectors),
                 },
             }
         )
@@ -519,75 +516,59 @@ async def chunk_context_endpoint(request: Request) -> JSONResponse:
                 status_code=400,
             )
 
+        # Type assertions - we validated these above
+        assert doc_type is not None
+        assert doc_id is not None
+        assert start_str is not None
+        assert end_str is not None
+
         start = int(start_str)
         end = int(end_str)
 
-        # Currently only support notes
-        if doc_type != "note":
-            return JSONResponse(
-                {"success": False, "error": f"Unsupported doc_type: {doc_type}"},
-                status_code=400,
-            )
-
-        # Get authenticated HTTP client and fetch note
+        # Get authenticated Nextcloud client
         from nextcloud_mcp_server.auth.userinfo_routes import (
             _get_authenticated_client_for_userinfo,
         )
-        from nextcloud_mcp_server.client.notes import NotesClient
+        from nextcloud_mcp_server.search.context import get_chunk_with_context
 
-        # Get username from request auth
-        username = (
-            request.user.display_name
-            if hasattr(request.user, "display_name")
-            else "unknown"
-        )
+        # Use context expansion module to fetch chunk with surrounding context
+        async with await _get_authenticated_client_for_userinfo(request) as nc_client:
+            chunk_context = await get_chunk_with_context(
+                nc_client=nc_client,
+                user_id=request.user.display_name,  # User ID from auth
+                doc_id=doc_id,
+                doc_type=doc_type,
+                chunk_start=start,
+                chunk_end=end,
+                context_chars=context_chars,
+            )
 
-        # Create notes client with authenticated HTTP client
-        http_client = await _get_authenticated_client_for_userinfo(request)
-        notes_client = NotesClient(http_client, username)
-
-        # Fetch full note content
-        note = await notes_client.get_note(int(doc_id))
-        full_content = f"{note['title']}\n\n{note['content']}"
-
-        # Validate offsets
-        if start < 0 or end > len(full_content) or start >= end:
+        # Check if context expansion succeeded
+        if chunk_context is None:
             return JSONResponse(
                 {
                     "success": False,
-                    "error": f"Invalid offsets: start={start}, end={end}, content_length={len(full_content)}",
+                    "error": f"Failed to fetch chunk context for {doc_type} {doc_id}",
                 },
-                status_code=400,
+                status_code=404,
             )
 
-        # Extract chunk
-        chunk_text = full_content[start:end]
-
-        # Extract context before and after
-        before_start = max(0, start - context_chars)
-        before_context = full_content[before_start:start]
-
-        after_end = min(len(full_content), end + context_chars)
-        after_context = full_content[end:after_end]
-
-        # Determine if there's more content
-        has_more_before = before_start > 0
-        has_more_after = after_end < len(full_content)
-
         logger.info(
             f"Fetched chunk context for {doc_type}_{doc_id}: "
-            f"chunk_len={len(chunk_text)}, before_len={len(before_context)}, "
-            f"after_len={len(after_context)}"
+            f"chunk_len={len(chunk_context.chunk_text)}, "
+            f"before_len={len(chunk_context.before_context)}, "
+            f"after_len={len(chunk_context.after_context)}"
         )
 
+        # Return response compatible with frontend expectations
         return JSONResponse(
             {
                 "success": True,
-                "chunk_text": chunk_text,
-                "before_context": before_context,
-                "after_context": after_context,
-                "has_more_before": has_more_before,
-                "has_more_after": has_more_after,
+                "chunk_text": chunk_context.chunk_text,
+                "before_context": chunk_context.before_context,
+                "after_context": chunk_context.after_context,
+                "has_more_before": chunk_context.has_before_truncation,
+                "has_more_after": chunk_context.has_after_truncation,
             }
         )
 
diff --git a/nextcloud_mcp_server/client/__init__.py b/nextcloud_mcp_server/client/__init__.py
index d6e9f24..a3277c6 100644
--- a/nextcloud_mcp_server/client/__init__.py
+++ b/nextcloud_mcp_server/client/__init__.py
@@ -190,6 +190,15 @@ class NextcloudClient:
         """Helper to get the base WebDAV path for the authenticated user."""
         return f"/remote.php/dav/files/{self.username}"
 
+    async def __aenter__(self):
+        """Async context manager entry."""
+        return self
+
+    async def __aexit__(self, exc_type, exc_val, exc_tb):
+        """Async context manager exit - closes all clients."""
+        await self.close()
+        return False  # Don't suppress exceptions
+
     async def close(self):
         """Close the HTTP client and CalDAV client."""
         await self._client.aclose()
diff --git a/nextcloud_mcp_server/models/semantic.py b/nextcloud_mcp_server/models/semantic.py
index 2586195..e6cea54 100644
--- a/nextcloud_mcp_server/models/semantic.py
+++ b/nextcloud_mcp_server/models/semantic.py
@@ -35,6 +35,29 @@ class SemanticSearchResult(BaseModel):
     chunk_end_offset: Optional[int] = Field(
         default=None, description="Character position where chunk ends in document"
     )
+    page_number: Optional[int] = Field(
+        default=None, description="Page number for PDF documents"
+    )
+    # Context expansion fields (optional, populated when include_context=True)
+    has_context_expansion: bool = Field(
+        default=False, description="Whether context expansion was performed"
+    )
+    marked_text: Optional[str] = Field(
+        default=None,
+        description="Full text with position markers around matched chunk",
+    )
+    before_context: Optional[str] = Field(
+        default=None, description="Text before the matched chunk"
+    )
+    after_context: Optional[str] = Field(
+        default=None, description="Text after the matched chunk"
+    )
+    has_before_truncation: Optional[bool] = Field(
+        default=None, description="Whether before_context was truncated"
+    )
+    has_after_truncation: Optional[bool] = Field(
+        default=None, description="Whether after_context was truncated"
+    )
 
 
 class SemanticSearchResponse(BaseResponse):
diff --git a/nextcloud_mcp_server/search/algorithms.py b/nextcloud_mcp_server/search/algorithms.py
index c859960..416d0d7 100644
--- a/nextcloud_mcp_server/search/algorithms.py
+++ b/nextcloud_mcp_server/search/algorithms.py
@@ -133,6 +133,9 @@ class SearchResult:
         metadata: Additional algorithm-specific metadata
         chunk_start_offset: Character position where chunk starts (None if not available)
         chunk_end_offset: Character position where chunk ends (None if not available)
+        page_number: Page number for PDF documents (None for other doc types)
+        chunk_index: Zero-based index of this chunk in the document
+        total_chunks: Total number of chunks in the document
     """
 
     id: int
@@ -143,6 +146,9 @@ class SearchResult:
     metadata: dict[str, Any] | None = None
     chunk_start_offset: int | None = None
     chunk_end_offset: int | None = None
+    page_number: int | None = None
+    chunk_index: int = 0
+    total_chunks: int = 1
 
     def __post_init__(self):
         """Validate score is non-negative.
diff --git a/nextcloud_mcp_server/search/bm25_hybrid.py b/nextcloud_mcp_server/search/bm25_hybrid.py
index 5acb861..1c4336b 100644
--- a/nextcloud_mcp_server/search/bm25_hybrid.py
+++ b/nextcloud_mcp_server/search/bm25_hybrid.py
@@ -72,6 +72,9 @@ class BM25HybridSearchAlgorithm(SearchAlgorithm):
         Returns unverified results from Qdrant. Access verification should be
         performed separately at the final output stage using verify_search_results().
 
+        Deduplicates by (doc_id, doc_type, chunk_start_offset, chunk_end_offset)
+        to show multiple chunks from the same document while avoiding duplicate chunks.
+
         Args:
             query: Natural language or keyword search query
             user_id: User ID for filtering
@@ -176,21 +179,24 @@ class BM25HybridSearchAlgorithm(SearchAlgorithm):
                 f"Top 3 {self.fusion_name.upper()} fusion scores: {top_scores}"
             )
 
-        # Deduplicate by (doc_id, doc_type) - multiple chunks per document
-        seen_docs = set()
+        # Deduplicate by (doc_id, doc_type, chunk_start, chunk_end)
+        # This allows multiple chunks from same doc, but removes duplicate chunks
+        seen_chunks = set()
         results = []
 
         for result in search_response.points:
             # doc_id can be int (notes) or str (files - file paths)
             doc_id = result.payload["doc_id"]
             doc_type = result.payload.get("doc_type", "note")
-            doc_key = (doc_id, doc_type)
+            chunk_start = result.payload.get("chunk_start_offset")
+            chunk_end = result.payload.get("chunk_end_offset")
+            chunk_key = (doc_id, doc_type, chunk_start, chunk_end)
 
-            # Skip if we've already seen this document
-            if doc_key in seen_docs:
+            # Skip if we've already seen this exact chunk
+            if chunk_key in seen_chunks:
                 continue
 
-            seen_docs.add(doc_key)
+            seen_chunks.add(chunk_key)
 
             # Return unverified results (verification happens at output stage)
             results.append(
@@ -207,6 +213,9 @@ class BM25HybridSearchAlgorithm(SearchAlgorithm):
                     },
                     chunk_start_offset=result.payload.get("chunk_start_offset"),
                     chunk_end_offset=result.payload.get("chunk_end_offset"),
+                    page_number=result.payload.get("page_number"),
+                    chunk_index=result.payload.get("chunk_index", 0),
+                    total_chunks=result.payload.get("total_chunks", 1),
                 )
             )
 
diff --git a/nextcloud_mcp_server/search/context.py b/nextcloud_mcp_server/search/context.py
new file mode 100644
index 0000000..43be81b
--- /dev/null
+++ b/nextcloud_mcp_server/search/context.py
@@ -0,0 +1,265 @@
+"""Context expansion for search results.
+
+Provides utilities to expand matched chunks with surrounding context and
+position markers for better visualization and understanding of search results.
+"""
+
+import logging
+from dataclasses import dataclass
+
+from nextcloud_mcp_server.client import NextcloudClient
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class ChunkContext:
+    """Expanded chunk with surrounding context and position markers.
+
+    Attributes:
+        chunk_text: The matched chunk text
+        before_context: Text before the chunk (up to context_chars)
+        after_context: Text after the chunk (up to context_chars)
+        chunk_start_offset: Character position where chunk starts in document
+        chunk_end_offset: Character position where chunk ends in document
+        page_number: Page number for PDFs (None for other doc types)
+        chunk_index: Zero-based chunk index (N in "chunk N of M")
+        total_chunks: Total number of chunks in document
+        marked_text: Full text with position markers around the chunk
+        has_before_truncation: True if before_context was truncated
+        has_after_truncation: True if after_context was truncated
+    """
+
+    chunk_text: str
+    before_context: str
+    after_context: str
+    chunk_start_offset: int
+    chunk_end_offset: int
+    page_number: int | None
+    chunk_index: int
+    total_chunks: int
+    marked_text: str
+    has_before_truncation: bool
+    has_after_truncation: bool
+
+
+async def get_chunk_with_context(
+    nc_client: NextcloudClient,
+    user_id: str,
+    doc_id: str | int,
+    doc_type: str,
+    chunk_start: int,
+    chunk_end: int,
+    page_number: int | None = None,
+    chunk_index: int = 0,
+    total_chunks: int = 1,
+    context_chars: int = 300,
+) -> ChunkContext | None:
+    """Fetch chunk with surrounding context from original document.
+
+    Retrieves the full document text and expands the matched chunk to include
+    surrounding context for better understanding. Inserts position markers
+    around the chunk for visualization.
+
+    Args:
+        nc_client: Authenticated Nextcloud client
+        user_id: User ID who owns the document
+        doc_id: Document ID (note ID or file path)
+        doc_type: Type of document ("note", "file", etc.)
+        chunk_start: Character offset where chunk starts
+        chunk_end: Character offset where chunk ends
+        page_number: Optional page number for PDFs
+        chunk_index: Zero-based chunk index in document
+        total_chunks: Total number of chunks in document
+        context_chars: Number of characters to include before/after chunk
+
+    Returns:
+        ChunkContext with expanded context and markers, or None if document
+        cannot be retrieved
+    """
+    # Fetch full document text
+    full_text = await _fetch_document_text(nc_client, doc_id, doc_type)
+    if full_text is None:
+        logger.warning(
+            f"Could not fetch document text for {doc_type} {doc_id}, "
+            "skipping context expansion"
+        )
+        return None
+
+    # Validate offsets
+    if chunk_start < 0 or chunk_end > len(full_text) or chunk_start >= chunk_end:
+        logger.warning(
+            f"Invalid chunk offsets for {doc_type} {doc_id}: "
+            f"start={chunk_start}, end={chunk_end}, doc_len={len(full_text)}"
+        )
+        return None
+
+    # Extract chunk text
+    chunk_text = full_text[chunk_start:chunk_end]
+
+    # Calculate context boundaries
+    context_start = max(0, chunk_start - context_chars)
+    context_end = min(len(full_text), chunk_end + context_chars)
+
+    # Extract context
+    before_context = full_text[context_start:chunk_start]
+    after_context = full_text[chunk_end:context_end]
+
+    # Check for truncation
+    has_before_truncation = context_start > 0
+    has_after_truncation = context_end < len(full_text)
+
+    # Create marked text with position markers
+    marked_text = _insert_position_markers(
+        before_context=before_context,
+        chunk_text=chunk_text,
+        after_context=after_context,
+        page_number=page_number,
+        chunk_index=chunk_index,
+        total_chunks=total_chunks,
+        has_before_truncation=has_before_truncation,
+        has_after_truncation=has_after_truncation,
+    )
+
+    return ChunkContext(
+        chunk_text=chunk_text,
+        before_context=before_context,
+        after_context=after_context,
+        chunk_start_offset=chunk_start,
+        chunk_end_offset=chunk_end,
+        page_number=page_number,
+        chunk_index=chunk_index,
+        total_chunks=total_chunks,
+        marked_text=marked_text,
+        has_before_truncation=has_before_truncation,
+        has_after_truncation=has_after_truncation,
+    )
+
+
+async def _fetch_document_text(
+    nc_client: NextcloudClient, doc_id: str | int, doc_type: str
+) -> str | None:
+    """Fetch full text content of a document.
+
+    Args:
+        nc_client: Authenticated Nextcloud client
+        doc_id: Document ID (note ID or file path)
+        doc_type: Type of document ("note", "file", etc.)
+
+    Returns:
+        Full document text, or None if document cannot be retrieved
+    """
+    try:
+        if doc_type == "note":
+            # Fetch note by ID
+            note = await nc_client.notes.get_note(note_id=int(doc_id))
+            return note.get("content", "")
+        elif doc_type == "file":
+            # Fetch file content via WebDAV
+            try:
+                file_path = str(doc_id)
+                file_content, content_type = await nc_client.webdav.read_file(file_path)
+
+                # Check if it's a PDF (by content type or file extension)
+                is_pdf = (
+                    content_type and "pdf" in content_type.lower()
+                ) or file_path.lower().endswith(".pdf")
+
+                if is_pdf:
+                    # Extract text from PDF using PyMuPDF
+                    import fitz  # PyMuPDF
+
+                    logger.debug(f"Extracting text from PDF: {file_path}")
+                    pdf_doc = fitz.open(stream=file_content, filetype="pdf")
+                    text_parts = []
+                    for page in pdf_doc:
+                        text_parts.append(page.get_text())
+                    pdf_doc.close()
+
+                    full_text = "\n".join(text_parts)
+                    logger.debug(
+                        f"Extracted {len(full_text)} characters from "
+                        f"{len(text_parts)} pages in {file_path}"
+                    )
+                    return full_text
+                else:
+                    # Assume it's a text file, decode to string
+                    logger.debug(f"Decoding text file: {file_path}")
+                    return file_content.decode("utf-8", errors="replace")
+            except Exception as e:
+                logger.error(
+                    f"Error fetching file content for {doc_id}: {e}", exc_info=True
+                )
+                return None
+        else:
+            logger.warning(f"Unsupported doc_type for context expansion: {doc_type}")
+            return None
+    except Exception as e:
+        logger.error(f"Error fetching document {doc_type} {doc_id}: {e}", exc_info=True)
+        return None
+
+
+def _insert_position_markers(
+    before_context: str,
+    chunk_text: str,
+    after_context: str,
+    page_number: int | None,
+    chunk_index: int,
+    total_chunks: int,
+    has_before_truncation: bool,
+    has_after_truncation: bool,
+) -> str:
+    """Insert position markers around matched chunk.
+
+    Creates markdown-formatted text with visual markers indicating chunk
+    boundaries and metadata.
+
+    Args:
+        before_context: Text before chunk
+        chunk_text: The matched chunk
+        after_context: Text after chunk
+        page_number: Optional page number
+        chunk_index: Zero-based chunk index
+        total_chunks: Total chunks in document
+        has_before_truncation: Whether before_context is truncated
+        has_after_truncation: Whether after_context is truncated
+
+    Returns:
+        Formatted text with position markers
+    """
+    # Build position metadata
+    position_parts = []
+    if page_number is not None:
+        position_parts.append(f"Page {page_number}")
+    position_parts.append(f"Chunk {chunk_index + 1} of {total_chunks}")
+    position_metadata = ", ".join(position_parts)
+
+    # Build marked text
+    parts = []
+
+    # Add truncation indicator for before context
+    if has_before_truncation:
+        parts.append("**[...]**\n\n")
+
+    # Add before context if present
+    if before_context:
+        parts.append(before_context)
+
+    # Add chunk start marker
+    parts.append(f"\n\n🔍 **MATCHED CHUNK START** ({position_metadata})\n\n")
+
+    # Add chunk text
+    parts.append(chunk_text)
+
+    # Add chunk end marker
+    parts.append("\n\n🔍 **MATCHED CHUNK END**\n\n")
+
+    # Add after context if present
+    if after_context:
+        parts.append(after_context)
+
+    # Add truncation indicator for after context
+    if has_after_truncation:
+        parts.append("\n\n**[...]**")
+
+    return "".join(parts)
diff --git a/nextcloud_mcp_server/search/semantic.py b/nextcloud_mcp_server/search/semantic.py
index 133a0cd..e1c52cf 100644
--- a/nextcloud_mcp_server/search/semantic.py
+++ b/nextcloud_mcp_server/search/semantic.py
@@ -50,6 +50,9 @@ class SemanticSearchAlgorithm(SearchAlgorithm):
         Returns unverified results from Qdrant. Access verification should be
         performed separately at the final output stage using verify_search_results().
 
+        Deduplicates by (doc_id, doc_type, chunk_start_offset, chunk_end_offset)
+        to show multiple chunks from the same document while avoiding duplicate chunks.
+
         Args:
             query: Natural language search query
             user_id: User ID for filtering
@@ -123,21 +126,24 @@ class SemanticSearchAlgorithm(SearchAlgorithm):
             top_scores = [p.score for p in search_response.points[:3]]
             logger.debug(f"Top 3 similarity scores: {top_scores}")
 
-        # Deduplicate by (doc_id, doc_type) - multiple chunks per document
-        seen_docs = set()
+        # Deduplicate by (doc_id, doc_type, chunk_start, chunk_end)
+        # This allows multiple chunks from same doc, but removes duplicate chunks
+        seen_chunks = set()
         results = []
 
         for result in search_response.points:
             # doc_id can be int (notes) or str (files - file paths)
             doc_id = result.payload["doc_id"]
             doc_type = result.payload.get("doc_type", "note")
-            doc_key = (doc_id, doc_type)
+            chunk_start = result.payload.get("chunk_start_offset")
+            chunk_end = result.payload.get("chunk_end_offset")
+            chunk_key = (doc_id, doc_type, chunk_start, chunk_end)
 
-            # Skip if we've already seen this document
-            if doc_key in seen_docs:
+            # Skip if we've already seen this exact chunk
+            if chunk_key in seen_chunks:
                 continue
 
-            seen_docs.add(doc_key)
+            seen_chunks.add(chunk_key)
 
             # Return unverified results (verification happens at output stage)
             results.append(
@@ -153,6 +159,9 @@ class SemanticSearchAlgorithm(SearchAlgorithm):
                     },
                     chunk_start_offset=result.payload.get("chunk_start_offset"),
                     chunk_end_offset=result.payload.get("chunk_end_offset"),
+                    page_number=result.payload.get("page_number"),
+                    chunk_index=result.payload.get("chunk_index", 0),
+                    total_chunks=result.payload.get("total_chunks", 1),
                 )
             )