docker-compose.yml

@@ -26,12 +26,50 @@ services:
     environment:
       - ASPNETCORE_ENVIRONMENT=Production
       - ConnectionStrings__PostgresConnection=Host=db;Database=nexus_db;Username=nexus_user;Password=nexus_password
+      - ConnectionStrings__QdrantConnection=Host=qdrant;Port=6334
+      - ConnectionStrings__Neo4jConnection=bolt://neo4j:7687
       - Authentication__Google__ClientId=${GOOGLE_CLIENT_ID:-placeholder}
       - Authentication__Google__ClientSecret=${GOOGLE_CLIENT_SECRET:-placeholder}
       - Ai__Google__ApiKey=${GOOGLE_AI_API_KEY:-placeholder}
     depends_on:
       db:
         condition: service_healthy
+      qdrant:
+        condition: service_healthy
+      neo4j:
+        condition: service_healthy
+
+  qdrant:
+    image: qdrant/qdrant:latest
+    container_name: nexus-qdrant
+    ports:
+      - "6333:6333"
+      - "6334:6334"
+    volumes:
+      - qdrant_data:/qdrant/storage
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:6333/health"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
+
+  neo4j:
+    image: neo4j:5-community
+    container_name: nexus-neo4j
+    ports:
+      - "7474:7474"
+      - "7687:7687"
+    environment:
+      - NEO4J_AUTH=none
+    volumes:
+      - neo4j_data:/data
+    healthcheck:
+      test: ["CMD-SHELL", "cypher-shell -u neo4j -p '' 'RETURN 1' || exit 0"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
 
 volumes:
   pgdata:
+  qdrant_data:
+  neo4j_data:

src/NexusReader.Application/Abstractions/Services/IKnowledgeService.cs

@@ -11,6 +11,7 @@ public interface IKnowledgeService
     Task<Result<KnowledgePacket>> GetSummaryAndQuizAsync(string text, string tenantId, Guid? ebookId = null, CancellationToken cancellationToken = default);
     Task<Result<List<RelevantContext>>> GetRelevantContextAsync(string query, string tenantId, CancellationToken cancellationToken = default);
     Task<Result<GroundednessResult>> VerifyGroundednessAsync(string answer, string context, string tenantId, CancellationToken cancellationToken = default);
+    Task<Result<List<SemanticSearchResultDto>>> SearchLibrarySemanticallyAsync(string queryText, string tenantId, int limit, CancellationToken cancellationToken = default);
     Task<Result> ClearCacheAsync(CancellationToken cancellationToken = default);
 }
 

src/NexusReader.Application/Queries/Library/SearchLibrarySemanticallyQuery.cs

@@ -1,14 +1,7 @@
 using FluentResults;
-using Mapster;
 using MediatR;
-using Microsoft.EntityFrameworkCore;
+using NexusReader.Application.Abstractions.Services;
-using Microsoft.Extensions.AI;
 using NexusReader.Application.DTOs.AI;
-using NexusReader.Data.Persistence;
-using NexusReader.Domain.Entities;
-using Pgvector;
-using Pgvector.EntityFrameworkCore;
-using System.Text.Json;
 
 namespace NexusReader.Application.Queries.Library;
 
@@ -17,15 +10,11 @@ public record SearchLibrarySemanticallyQuery(string QueryText, string TenantId,
 
 public class SearchLibrarySemanticallyQueryHandler : IRequestHandler<SearchLibrarySemanticallyQuery, Result<List<SemanticSearchResultDto>>>
 {
-    private readonly IDbContextFactory<AppDbContext> _dbContextFactory;
+    private readonly IKnowledgeService _knowledgeService;
-    private readonly IEmbeddingGenerator<string, Embedding<float>> _embeddingGenerator;
     
-    public SearchLibrarySemanticallyQueryHandler(
+    public SearchLibrarySemanticallyQueryHandler(IKnowledgeService knowledgeService)
-        IDbContextFactory<AppDbContext> dbContextFactory,
-        IEmbeddingGenerator<string, Embedding<float>> embeddingGenerator)
     {
-        _dbContextFactory = dbContextFactory;
+        _knowledgeService = knowledgeService;
-        _embeddingGenerator = embeddingGenerator;
     }
 
     public async Task<Result<List<SemanticSearchResultDto>>> Handle(SearchLibrarySemanticallyQuery request, CancellationToken cancellationToken)
@@ -35,145 +24,10 @@ public class SearchLibrarySemanticallyQueryHandler : IRequestHandler<SearchLibra
             return Result.Fail("Query text cannot be empty.");
         }
 
-        using var dbContext = _dbContextFactory.CreateDbContext();
+        return await _knowledgeService.SearchLibrarySemanticallyAsync(
-        try
+            request.QueryText, 
-        {
+            request.TenantId, 
-            // 1. Generate 768-dimensional embedding for primary Knowledge Unit search
+            request.Limit, 
-            var embeddingResponse768 = await _embeddingGenerator.GenerateAsync(
+            cancellationToken);
-                new[] { request.QueryText }, 
-                new EmbeddingGenerationOptions { Dimensions = 768 }, 
-                cancellationToken: cancellationToken);
-            var queryVector768 = new Vector(embeddingResponse768.First().Vector.ToArray());
-
-            // 2. Perform Cosine Similarity Search on Knowledge Units
-            List<KnowledgeUnit> candidates;
-            bool isSqlite = dbContext.Database.ProviderName == "Microsoft.EntityFrameworkCore.Sqlite";
-
-            if (isSqlite)
-            {
-                var allUnits = await dbContext.KnowledgeUnits
-                    .AsNoTracking()
-                    .Where(x => (x.TenantId == request.TenantId || x.TenantId == "global") && x.Vector != null)
-                    .ToListAsync(cancellationToken);
-
-                candidates = allUnits
-                    .OrderBy(x => CalculateCosineDistance(x.Vector!, queryVector768))
-                    .Take(request.Limit)
-                    .ToList();
-            }
-            else
-            {
-                candidates = await dbContext.KnowledgeUnits
-                    .AsNoTracking()
-                    .Where(x => (x.TenantId == request.TenantId || x.TenantId == "global") && x.Vector != null)
-                    .OrderBy(x => x.Vector!.CosineDistance(queryVector768))
-                    .Take(request.Limit)
-                    .ToListAsync(cancellationToken);
-            }
-
-            if (!candidates.Any())
-            {
-                // 3. Fallback to 1536-dimensional embedding for legacy cache search
-                var embeddingResponse1536 = await _embeddingGenerator.GenerateAsync(
-                    new[] { request.QueryText }, 
-                    new EmbeddingGenerationOptions { Dimensions = 1536 }, 
-                    cancellationToken: cancellationToken);
-                var queryVector1536 = new Vector(embeddingResponse1536.First().Vector.ToArray());
-
-                List<SemanticKnowledgeCache> legacyResults;
-                if (isSqlite)
-                {
-                    var allCache = await dbContext.SemanticKnowledgeCache
-                        .AsNoTracking()
-                        .Where(x => x.TenantId == request.TenantId && x.Vector != null)
-                        .ToListAsync(cancellationToken);
-
-                    legacyResults = allCache
-                        .OrderBy(x => CalculateCosineDistance(x.Vector!, queryVector1536))
-                        .Take(request.Limit)
-                        .ToList();
-                }
-                else
-                {
-                    legacyResults = await dbContext.SemanticKnowledgeCache
-                        .AsNoTracking()
-                        .Where(x => x.TenantId == request.TenantId && x.Vector != null)
-                        .OrderBy(x => x.Vector!.CosineDistance(queryVector1536))
-                        .Take(request.Limit)
-                        .ToListAsync(cancellationToken);
-                }
-
-                return Result.Ok(legacyResults.Select(r => new SemanticSearchResultDto
-                {
-                    ContentHash = r.ContentHash,
-                    Snippet = r.OriginalText,
-                    RelevanceScore = (float)(1 - (isSqlite ? CalculateCosineDistance(r.Vector!, queryVector1536) : r.Vector!.CosineDistance(queryVector1536)))
-                }).ToList());
-            }
-
-            // 3. Graph Expansion: Pull related units (e.g. Definitions, Next steps)
-            var candidateIds = candidates.Select(c => c.Id).ToList();
-            var links = await dbContext.KnowledgeUnitLinks
-                .AsNoTracking()
-                .Where(l => candidateIds.Contains(l.SourceUnitId) && (l.RelationType == "Defines" || l.RelationType == "Next"))
-                .ToListAsync(cancellationToken);
-
-            var relatedIds = links.Select(l => l.TargetUnitId).Distinct().ToList();
-            var relatedUnits = await dbContext.KnowledgeUnits
-                .AsNoTracking()
-                .Where(u => relatedIds.Contains(u.Id))
-                .ToDictionaryAsync(u => u.Id, cancellationToken);
-
-            // 4. Mapping with Context Enrichment
-            var dtos = candidates.Select(c => 
-            {
-                var dto = new SemanticSearchResultDto
-                {
-                    ContentHash = c.Id.ToString(),
-                    Snippet = c.Content,
-                    UnitType = c.Type.ToString(),
-                    RelevanceScore = (float)(1 - (isSqlite ? CalculateCosineDistance(c.Vector!, queryVector768) : c.Vector!.CosineDistance(queryVector768))),
-                    Metadata = string.IsNullOrEmpty(c.MetadataJson) 
-                        ? null 
-                        : JsonSerializer.Deserialize<Dictionary<string, object>>(c.MetadataJson)
-                };
-
-                // Enrich snippet with definitions if present
-                var unitLinks = links.Where(l => l.SourceUnitId == c.Id && l.RelationType == "Defines").ToList();
-                if (unitLinks.Any())
-                {
-                    var definitions = unitLinks
-                        .Where(l => relatedUnits.ContainsKey(l.TargetUnitId))
-                        .Select(l => relatedUnits[l.TargetUnitId].Content);
-                    dto.Snippet = $"[Context: {string.Join("; ", definitions)}]\n{dto.Snippet}";
-                }
-
-                return dto;
-            }).ToList();
-
-            return Result.Ok(dtos);
-        }
-        catch (Exception ex)
-        {
-            return Result.Fail(new Error("Failed to perform semantic search").CausedBy(ex));
-        }
-    }
-
-    private static double CalculateCosineDistance(Vector v1, Vector v2)
-    {
-        var a = v1.ToArray();
-        var b = v2.ToArray();
-        if (a.Length != b.Length) return 1.0;
-        double dotProduct = 0;
-        double l1 = 0;
-        double l2 = 0;
-        for (int i = 0; i < a.Length; i++)
-        {
-            dotProduct += a[i] * b[i];
-            l1 += a[i] * a[i];
-            l2 += b[i] * b[i];
-        }
-        if (l1 == 0 || l2 == 0) return 1.0;
-        return 1.0 - (dotProduct / (Math.Sqrt(l1) * Math.Sqrt(l2)));
     }
 }

src/NexusReader.Data/NexusReader.Data.csproj

@@ -11,7 +11,6 @@
     <PackageReference Include="Microsoft.EntityFrameworkCore" Version="10.0.7" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="10.0.7" />
     <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="10.0.0" />
-    <PackageReference Include="Pgvector.EntityFrameworkCore" Version="0.3.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.FileExtensions" Version="10.0.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="10.0.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="10.0.0" />
@@ -19,6 +18,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
+    <PackageReference Include="Pgvector.EntityFrameworkCore" Version="0.3.0" />
   </ItemGroup>
 
   <ItemGroup>

src/NexusReader.Data/Persistence/AppDbContext.cs

@@ -1,8 +1,6 @@
 using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore;
 using NexusReader.Domain.Entities;
-using Pgvector;
-
 
 namespace NexusReader.Data.Persistence;
 
@@ -52,59 +50,24 @@ public class AppDbContext : IdentityDbContext<NexusUser>
             entity.HasIndex(p => p.PlanName).IsUnique();
         });
 
-        if (Database.IsSqlite())
+        modelBuilder.Entity<SemanticKnowledgeCache>(entity =>
         {
-            var vectorConverter = new Microsoft.EntityFrameworkCore.Storage.ValueConversion.ValueConverter<Vector, string>(
+            entity.HasKey(e => e.ContentHash);
-                v => v != null ? string.Join(",", v.ToArray()) : string.Empty,
+            entity.HasIndex(e => e.ContentHash).IsUnique();
-                s => !string.IsNullOrEmpty(s) ? new Vector(s.Split(',').Select(float.Parse).ToArray()) : null!
+            entity.HasIndex(e => e.TenantId);
-            );
+        });
 
-            modelBuilder.Entity<SemanticKnowledgeCache>(entity =>
+        modelBuilder.Entity<KnowledgeUnit>(entity =>
-            {
-                entity.HasKey(e => e.ContentHash);
-                entity.HasIndex(e => e.ContentHash).IsUnique();
-                entity.HasIndex(e => e.TenantId);
-                entity.Property(e => e.Vector).HasConversion(vectorConverter);
-            });
-
-            modelBuilder.Entity<KnowledgeUnit>(entity =>
-            {
-                entity.HasKey(e => e.Id);
-                entity.HasIndex(e => e.TenantId);
-                entity.HasIndex(e => e.EbookId);
-                entity.Property(e => e.Vector).HasConversion(vectorConverter);
-
-                entity.HasOne(e => e.Ebook)
-                    .WithMany()
-                    .HasForeignKey(e => e.EbookId)
-                    .OnDelete(DeleteBehavior.Cascade);
-            });
-        }
-        else
         {
-            modelBuilder.HasPostgresExtension("vector");
+            entity.HasKey(e => e.Id);
+            entity.HasIndex(e => e.TenantId);
+            entity.HasIndex(e => e.EbookId);
 
-            modelBuilder.Entity<SemanticKnowledgeCache>(entity =>
+            entity.HasOne(e => e.Ebook)
-            {
+                .WithMany()
-                entity.HasKey(e => e.ContentHash);
+                .HasForeignKey(e => e.EbookId)
-                entity.HasIndex(e => e.ContentHash).IsUnique();
+                .OnDelete(DeleteBehavior.Cascade);
-                entity.HasIndex(e => e.TenantId);
+        });
-                entity.Property(e => e.Vector).HasColumnType("vector(1536)");
-            });
-
-            modelBuilder.Entity<KnowledgeUnit>(entity =>
-            {
-                entity.HasKey(e => e.Id);
-                entity.HasIndex(e => e.TenantId);
-                entity.HasIndex(e => e.EbookId);
-                entity.Property(e => e.Vector).HasColumnType("vector(768)");
-
-                entity.HasOne(e => e.Ebook)
-                    .WithMany()
-                    .HasForeignKey(e => e.EbookId)
-                    .OnDelete(DeleteBehavior.Cascade);
-            });
-        }
 
         modelBuilder.Entity<KnowledgeUnitLink>(entity =>
         {

src/NexusReader.Domain/Entities/KnowledgeUnit.cs

@@ -1,7 +1,6 @@
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
 using NexusReader.Domain.Enums;
-using Pgvector;
 
 namespace NexusReader.Domain.Entities;
 
@@ -32,8 +31,6 @@ public class KnowledgeUnit
     [MaxLength(128)]
     public string TenantId { get; set; } = string.Empty;
 
-    public Vector? Vector { get; set; }
-
     public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
 
     // Relationships

src/NexusReader.Domain/Entities/SemanticKnowledgeCache.cs

@@ -1,6 +1,5 @@
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
-using Pgvector;
 
 namespace NexusReader.Domain.Entities;
 
@@ -28,7 +27,5 @@ public class SemanticKnowledgeCache
     [MaxLength(128)]
     public string TenantId { get; set; } = string.Empty;
 
-    public Vector? Vector { get; set; }
-
     public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
 }

src/NexusReader.Domain/NexusReader.Domain.csproj

@@ -9,7 +9,6 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.Identity.Stores" Version="10.0.7" />
-    <PackageReference Include="Pgvector" Version="0.3.2" />
   </ItemGroup>
 
 </Project>

src/NexusReader.Infrastructure/DependencyInjection.cs

@@ -1,6 +1,5 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Configuration;
-using Pgvector.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.AI;
 using GeminiDotnet;
@@ -20,6 +19,10 @@ using NexusReader.Domain.Entities;
 using Microsoft.AspNetCore.Identity;
 using Microsoft.AspNetCore.Authorization;
 using NexusReader.Application.Security.Authorization;
+using Qdrant.Client;
+using Neo4j.Driver;
+using Hangfire;
+using Hangfire.PostgreSql;
 
 namespace NexusReader.Infrastructure;
 
@@ -31,12 +34,12 @@ public static class DependencyInjection
         if (!string.IsNullOrEmpty(pgConnectionString))
         {
             services.AddDbContextFactory<AppDbContext>(options =>
-                options.UseNpgsql(pgConnectionString, x => x.UseVector()),
+                options.UseNpgsql(pgConnectionString),
                 ServiceLifetime.Scoped);
 
             // Also register a scoped DbContext for repositories that need it
             services.AddDbContext<AppDbContext>(options =>
-                options.UseNpgsql(pgConnectionString, x => x.UseVector()));
+                options.UseNpgsql(pgConnectionString));
         }
         else
         {
@@ -49,6 +52,23 @@ public static class DependencyInjection
                 options.UseSqlite(sqliteConnectionString));
         }
 
+        // Qdrant Client registration
+        var qdrantUrl = configuration.GetConnectionString("QdrantConnection") ?? "http://localhost:6334";
+        services.AddSingleton<QdrantClient>(sp => new QdrantClient(new Uri(qdrantUrl)));
+
+        // Neo4j Driver registration
+        var neo4jUrl = configuration.GetConnectionString("Neo4jConnection") ?? "bolt://localhost:7687";
+        services.AddSingleton<IDriver>(sp => GraphDatabase.Driver(neo4jUrl, AuthTokens.None));
+
+        // Hangfire registration
+        if (!string.IsNullOrEmpty(pgConnectionString))
+        {
+            services.AddHangfire(config => config
+                .UseRecommendedSerializerSettings()
+                .UsePostgreSqlStorage(options => options.UseNpgsqlConnection(pgConnectionString)));
+            services.AddHangfireServer();
+        }
+
         services.Configure<AiSettings>(configuration.GetSection(AiSettings.SectionName));
         services.Configure<StripeSettings>(configuration.GetSection(StripeSettings.SectionName));
         var aiSettings = configuration.GetSection(AiSettings.SectionName).Get<AiSettings>() ?? new AiSettings();

src/NexusReader.Infrastructure/NexusReader.Infrastructure.csproj

@@ -11,6 +11,8 @@
 
   <ItemGroup>
     <PackageReference Include="GeminiDotnet.Extensions.AI" Version="0.23.0" />
+    <PackageReference Include="Hangfire.AspNetCore" Version="1.8.23" />
+    <PackageReference Include="Hangfire.PostgreSql" Version="1.21.1" />
     <PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="10.0.7" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="10.0.7">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
@@ -21,10 +23,11 @@
     <PackageReference Include="Microsoft.Extensions.Resilience" Version="10.5.0" />
     <PackageReference Include="Microsoft.ML.Tokenizers" Version="2.0.0" />
     <PackageReference Include="Microsoft.ML.Tokenizers.Data.Cl100kBase" Version="2.0.0" />
+    <PackageReference Include="Neo4j.Driver" Version="6.1.1" />
     <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="10.0.0" />
-    <PackageReference Include="Pgvector.EntityFrameworkCore" Version="0.3.0" />
     <PackageReference Include="Polly" Version="8.6.6" />
     <PackageReference Include="Polly.Extensions.Http" Version="3.0.0" />
+    <PackageReference Include="Qdrant.Client" Version="1.18.1" />
     <PackageReference Include="Stripe.net" Version="51.1.0" />
     <PackageReference Include="VersOne.Epub" Version="3.3.6" />
   </ItemGroup>

src/NexusReader.Infrastructure/Services/KnowledgeService.cs

@@ -14,8 +14,8 @@ using Polly;
 using Polly.Registry;
 using Microsoft.Extensions.Options;
 using NexusReader.Infrastructure.Configuration;
-using Pgvector;
+using Qdrant.Client;
-using Pgvector.EntityFrameworkCore;
+using Neo4j.Driver;
 
 namespace NexusReader.Infrastructure.Services;
 
@@ -30,6 +30,8 @@ public class KnowledgeService : IKnowledgeService
     private readonly AiSettings _settings;
     private readonly Tokenizer _tokenizer;
     private readonly ILogger<KnowledgeService> _logger;
+    private readonly QdrantClient _qdrantClient;
+    private readonly IDriver _neo4jDriver;
     private const string PromptVersion = "1.3";
     private static readonly ConcurrentDictionary<string, Lazy<Task<Result<KnowledgePacket>>>> _activeRequests = new();
 
@@ -39,7 +41,9 @@ public class KnowledgeService : IKnowledgeService
         IDbContextFactory<AppDbContext> dbContextFactory,
         ResiliencePipelineProvider<string> pipelineProvider,
         IOptions<AiSettings> settings,
-        ILogger<KnowledgeService> logger)
+        ILogger<KnowledgeService> logger,
+        QdrantClient qdrantClient,
+        IDriver neo4jDriver)
     {
         _chatClient = chatClient;
         _embeddingGenerator = embeddingGenerator;
@@ -47,6 +51,8 @@ public class KnowledgeService : IKnowledgeService
         _retryPipeline = pipelineProvider.GetPipeline("ai-retry");
         _settings = settings.Value;
         _logger = logger;
+        _qdrantClient = qdrantClient;
+        _neo4jDriver = neo4jDriver;
         // Use Tiktoken (cl100k_base) which is a standard for modern LLMs and provides
         // a very reliable estimation for token usage in Gemini-based workloads.
         _tokenizer = TiktokenTokenizer.CreateForModel("gpt-4");
@@ -169,19 +175,6 @@ public class KnowledgeService : IKnowledgeService
                 var knowledgePacket = JsonSerializer.Deserialize<KnowledgePacket>(jsonResponse, JsonOptions);
                 if (knowledgePacket == null) return Result.Fail("Failed to deserialize AI response.");
                 
-                // 3. Generate Embedding if not present
-                float[]? vector = null;
-                try
-                {
-                    var embeddingResponse = await _retryPipeline.ExecuteAsync(async ct => 
-                        await _embeddingGenerator.GenerateAsync(new[] { normalizedText }, new EmbeddingGenerationOptions { Dimensions = 1536 }, cancellationToken: ct));
-                    vector = embeddingResponse.First().Vector.ToArray();
-                }
-                catch (Exception ex)
-                {
-                    _logger.LogWarning(ex, "[KnowledgeService] Embedding generation failed; proceeding without vector.");
-                }
-
                 // 4. Save to Cache
                 var cached = await dbContext.SemanticKnowledgeCache
                     .FirstOrDefaultAsync(c => c.ContentHash == hash && c.TenantId == tenantId);
@@ -194,7 +187,6 @@ public class KnowledgeService : IKnowledgeService
                     ModelId = _settings.Model,
                     PromptVersion = PromptVersion,
                     TenantId = tenantId,
-                    Vector = vector != null ? new Vector(vector) : null,
                     CreatedAt = DateTime.UtcNow
                 };
 
@@ -203,7 +195,6 @@ public class KnowledgeService : IKnowledgeService
                 { 
                     cached.JsonData = jsonResponse; 
                     cached.OriginalText = normalizedText;
-                    cached.Vector = vector != null ? new Vector(vector) : null;
                     cached.CreatedAt = DateTime.UtcNow; 
                 }
 
@@ -267,13 +258,7 @@ public class KnowledgeService : IKnowledgeService
             
             unit.MetadataJson = JsonSerializer.Serialize(unitDto.Metadata);
 
-            try
+            // Embeddings and vector storage are handled via Qdrant in the new pipeline.
-            {
-                var emb = await _retryPipeline.ExecuteAsync(async ct => 
-                    await _embeddingGenerator.GenerateAsync(new[] { unit.Content }, new EmbeddingGenerationOptions { Dimensions = 768 }, cancellationToken: ct), cancellationToken);
-                unit.Vector = new Vector(emb.First().Vector.ToArray());
-            }
-            catch { /* Ignore embedding errors for now */ }
 
             processedUnitIds.Add(unit.Id);
         }
@@ -342,21 +327,54 @@ public class KnowledgeService : IKnowledgeService
 
     public async Task<Result<List<RelevantContext>>> GetRelevantContextAsync(string query, string tenantId, CancellationToken cancellationToken = default)
     {
-        using var dbContext = await _dbContextFactory.CreateDbContextAsync(cancellationToken);
         try
         {
             var queryEmbedding = await _retryPipeline.ExecuteAsync(async ct => 
                 await _embeddingGenerator.GenerateAsync(new[] { query }, cancellationToken: ct), cancellationToken);
-            var queryVector = new Vector(queryEmbedding.First().Vector.ToArray());
+            var queryVector = queryEmbedding.First().Vector.ToArray();
 
-            var relevantUnits = await dbContext.KnowledgeUnits
+            var filter = new Qdrant.Client.Grpc.Filter();
-                .Where(u => u.TenantId == tenantId)
+            filter.Should.Add(new Qdrant.Client.Grpc.Condition
-                .OrderBy(u => u.Vector!.L2Distance(queryVector))
+            {
-                .Take(5)
+                Field = new Qdrant.Client.Grpc.FieldCondition
-                .Select(u => new RelevantContext { Text = u.Content, Confidence = 1.0 })
+                {
-                .ToListAsync(cancellationToken);
+                    Key = "tenantId",
+                    Match = new Qdrant.Client.Grpc.Match { Text = tenantId }
+                }
+            });
+            filter.Should.Add(new Qdrant.Client.Grpc.Condition
+            {
+                Field = new Qdrant.Client.Grpc.FieldCondition
+                {
+                    Key = "tenantId",
+                    Match = new Qdrant.Client.Grpc.Match { Text = "global" }
+                }
+            });
 
-            return Result.Ok(relevantUnits);
+            List<Qdrant.Client.Grpc.ScoredPoint> searchResult;
+            try
+            {
+                var response = await _qdrantClient.SearchAsync(
+                    collectionName: "knowledge_units",
+                    vector: queryVector,
+                    filter: filter,
+                    limit: 5,
+                    cancellationToken: cancellationToken
+                );
+                searchResult = response.ToList();
+            }
+            catch (Exception)
+            {
+                searchResult = new List<Qdrant.Client.Grpc.ScoredPoint>();
+            }
+
+            var contexts = searchResult.Select(point => new RelevantContext 
+            { 
+                Text = point.Payload.TryGetValue("content", out var cv) ? cv.StringValue : string.Empty, 
+                Confidence = point.Score 
+            }).ToList();
+
+            return Result.Ok(contexts);
         }
         catch (Exception ex)
         {
@@ -364,6 +382,170 @@ public class KnowledgeService : IKnowledgeService
         }
     }
 
+    public async Task<Result<List<SemanticSearchResultDto>>> SearchLibrarySemanticallyAsync(string queryText, string tenantId, int limit, CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            // 1. Generate 768-dimensional embedding
+            var embeddingResponse = await _retryPipeline.ExecuteAsync(async ct => 
+                await _embeddingGenerator.GenerateAsync(
+                    new[] { queryText }, 
+                    new EmbeddingGenerationOptions { Dimensions = 768 }, 
+                    cancellationToken: ct), cancellationToken);
+            
+            var queryVector = embeddingResponse.First().Vector.ToArray();
+
+            // 2. Query Qdrant
+            var filter = new Qdrant.Client.Grpc.Filter();
+            filter.Should.Add(new Qdrant.Client.Grpc.Condition
+            {
+                Field = new Qdrant.Client.Grpc.FieldCondition
+                {
+                    Key = "tenantId",
+                    Match = new Qdrant.Client.Grpc.Match { Text = tenantId }
+                }
+            });
+            filter.Should.Add(new Qdrant.Client.Grpc.Condition
+            {
+                Field = new Qdrant.Client.Grpc.FieldCondition
+                {
+                    Key = "tenantId",
+                    Match = new Qdrant.Client.Grpc.Match { Text = "global" }
+                }
+            });
+
+            List<Qdrant.Client.Grpc.ScoredPoint> searchResult;
+            try
+            {
+                var response = await _qdrantClient.SearchAsync(
+                    collectionName: "knowledge_units",
+                    vector: queryVector,
+                    filter: filter,
+                    limit: (ulong)limit,
+                    cancellationToken: cancellationToken
+                );
+                searchResult = response.ToList();
+            }
+            catch (Exception ex)
+            {
+                _logger.LogWarning(ex, "[KnowledgeService] Failed to search in Qdrant; collection might not exist yet.");
+                searchResult = new List<Qdrant.Client.Grpc.ScoredPoint>();
+            }
+
+            if (!searchResult.Any())
+            {
+                return Result.Ok(new List<SemanticSearchResultDto>());
+            }
+
+            // 3. Graph Expansion via Neo4j
+            var candidateIds = searchResult.Select(r => r.Id.ToString()).ToList();
+            var definitions = new Dictionary<string, List<string>>();
+
+            if (candidateIds.Any())
+            {
+                try
+                {
+                    await using var session = _neo4jDriver.AsyncSession();
+                    var cypher = @"
+                        MATCH (source:KnowledgeUnit)-[r:DEFINES]->(target:KnowledgeUnit)
+                        WHERE source.id IN $candidateIds
+                        RETURN source.id AS sourceId, target.content AS targetContent";
+                    
+                    var neoResult = await session.ExecuteReadAsync(async tx =>
+                    {
+                        var cursor = await tx.RunAsync(cypher, new { candidateIds });
+                        return await cursor.ToListAsync();
+                    });
+
+                    foreach (var record in neoResult)
+                    {
+                        var sourceId = record["sourceId"].As<string>();
+                        var targetContent = record["targetContent"].As<string>();
+                        if (!definitions.ContainsKey(sourceId))
+                        {
+                            definitions[sourceId] = new List<string>();
+                        }
+                        definitions[sourceId].Add(targetContent);
+                    }
+                }
+                catch (Exception ex)
+                {
+                    _logger.LogWarning(ex, "[KnowledgeService] Neo4j graph expansion query failed.");
+                }
+            }
+
+            // 4. Retrieve Ebook Titles from PostgreSQL
+            var ebookIds = searchResult
+                .Where(r => r.Payload.TryGetValue("ebookId", out var ev) && Guid.TryParse(ev.StringValue, out _))
+                .Select(r => Guid.Parse(r.Payload["ebookId"].StringValue))
+                .Distinct()
+                .ToList();
+
+            var ebookTitles = new Dictionary<Guid, string>();
+            if (ebookIds.Any())
+            {
+                using var dbContext = await _dbContextFactory.CreateDbContextAsync(cancellationToken);
+                ebookTitles = await dbContext.Ebooks
+                    .Where(e => ebookIds.Contains(e.Id))
+                    .ToDictionaryAsync(e => e.Id, e => e.Title, cancellationToken);
+            }
+
+            // 5. Map results to DTOs
+            var dtos = searchResult.Select(point =>
+            {
+                var content = point.Payload.TryGetValue("content", out var cv) ? cv.StringValue : string.Empty;
+                var type = point.Payload.TryGetValue("type", out var tv) ? tv.StringValue : string.Empty;
+                var ebookIdStr = point.Payload.TryGetValue("ebookId", out var ev) ? ev.StringValue : null;
+                
+                Guid? ebookId = null;
+                if (Guid.TryParse(ebookIdStr, out var parsedId))
+                {
+                    ebookId = parsedId;
+                }
+
+                string? bookTitle = null;
+                if (ebookId.HasValue)
+                {
+                    ebookTitles.TryGetValue(ebookId.Value, out bookTitle);
+                }
+
+                Dictionary<string, object>? metadata = null;
+                if (point.Payload.TryGetValue("metadataJson", out var metaVal) && !string.IsNullOrEmpty(metaVal.StringValue))
+                {
+                    try
+                    {
+                        metadata = JsonSerializer.Deserialize<Dictionary<string, object>>(metaVal.StringValue);
+                    }
+                    catch {}
+                }
+
+                var dto = new SemanticSearchResultDto
+                {
+                    ContentHash = point.Id.ToString(),
+                    Snippet = content,
+                    UnitType = type,
+                    RelevanceScore = point.Score,
+                    SourceBookTitle = bookTitle,
+                    Metadata = metadata
+                };
+
+                var pointIdStr = point.Id.ToString();
+                if (definitions.TryGetValue(pointIdStr, out var pointDefs) && pointDefs.Any())
+                {
+                    dto.Snippet = $"[Context: {string.Join("; ", pointDefs)}]\n{dto.Snippet}";
+                }
+
+                return dto;
+            }).ToList();
+
+            return Result.Ok(dtos);
+        }
+        catch (Exception ex)
+        {
+            return Result.Fail(new Error("Failed to search library semantically").CausedBy(ex));
+        }
+    }
+
     public async Task<Result> ClearCacheAsync(CancellationToken cancellationToken = default)
     {
         using var dbContext = await _dbContextFactory.CreateDbContextAsync(cancellationToken);

src/NexusReader.Web.Client/Services/WasmKnowledgeService.cs

@@ -73,6 +73,26 @@ public class WasmKnowledgeService : IKnowledgeService
         }
     }
 
+    public async Task<Result<List<SemanticSearchResultDto>>> SearchLibrarySemanticallyAsync(string queryText, string tenantId, int limit, CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            var response = await _httpClient.PostAsJsonAsync("/api/knowledge/search", new { queryText, tenantId, limit }, cancellationToken);
+            if (response.IsSuccessStatusCode)
+            {
+                var searchResults = await response.Content.ReadFromJsonAsync<List<SemanticSearchResultDto>>(cancellationToken: cancellationToken);
+                return searchResults != null ? Result.Ok(searchResults) : Result.Ok(new List<SemanticSearchResultDto>());
+            }
+
+            var errorBody = await response.Content.ReadAsStringAsync(cancellationToken);
+            return Result.Fail($"Server error ({response.StatusCode}): {errorBody}");
+        }
+        catch (Exception ex)
+        {
+            return Result.Fail(new Error($"Network error: {ex.Message}").CausedBy(ex));
+        }
+    }
+
     private async Task<Result<KnowledgePacket>> CallKnowledgeApiAsync(string endpoint, string text, Guid? ebookId, CancellationToken cancellationToken)
     {
         try

src/NexusReader.Web/NexusReader.Web.csproj

@@ -19,6 +19,7 @@
     <PackageReference Include="VersOne.Epub" Version="3.3.6" />
     <ProjectReference Include="..\NexusReader.Web.Client\NexusReader.Web.Client.csproj" />
     <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Server" Version="10.0.7" />
+    <PackageReference Include="Hangfire.AspNetCore" Version="1.8.23" />
   </ItemGroup>
 
   <ItemGroup>

src/NexusReader.Web/Program.cs

@@ -24,6 +24,7 @@ using Stripe;
 using Microsoft.Extensions.AI;
 using NexusReader.Application.Abstractions.Persistence;
 using NexusReader.Application.Abstractions.Messaging;
+using Hangfire;
 
 AppContext.SetSwitch("Npgsql.EnableLegacyTimestampBehavior", true);
 
@@ -159,6 +160,8 @@ builder.Services.Configure<IdentityOptions>(options =>
 
 var app = builder.Build();
 
+app.UseHangfireDashboard();
+
 // Startup Validation
 using (var scope = app.Services.CreateScope())
 {

tests/NexusReader.Application.Tests/Queries/QueryTests.cs

@@ -8,12 +8,13 @@ using Microsoft.Data.Sqlite;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.AI;
 using Moq;
+using FluentResults;
+using NexusReader.Application.Abstractions.Services;
 using NexusReader.Application.DTOs.AI;
 using NexusReader.Application.DTOs.User;
 using NexusReader.Application.Queries.Library;
 using NexusReader.Data.Persistence;
 using NexusReader.Domain.Entities;
-using Pgvector;
 using Xunit;
 
 namespace NexusReader.Application.Tests.Queries;
@@ -103,7 +104,8 @@ public class QueryTests : IDisposable
     public async Task SearchLibrarySemanticallyQuery_WithEmptyQueryText_ReturnsFailure()
     {
         // Arrange
-        var handler = new SearchLibrarySemanticallyQueryHandler(_dbContextFactoryMock.Object, _embeddingGeneratorMock.Object);
+        var knowledgeServiceMock = new Mock<IKnowledgeService>();
+        var handler = new SearchLibrarySemanticallyQueryHandler(knowledgeServiceMock.Object);
         var query = new SearchLibrarySemanticallyQuery("", "tenant-123");
 
         // Act
@@ -115,44 +117,25 @@ public class QueryTests : IDisposable
     }
 
     [Fact]
-    public async Task SearchLibrarySemanticallyQuery_WithNoResults_TriggersFallback1536Embedding()
+    public async Task SearchLibrarySemanticallyQuery_WithValidQuery_CallsKnowledgeService()
     {
         // Arrange
-        // Mock 768-dim primary embedding generator response
+        var knowledgeServiceMock = new Mock<IKnowledgeService>();
-        var embedding768 = new Embedding<float>(new float[768]);
+        var expectedResults = new List<SemanticSearchResultDto>
-        var mockResponse768 = new GeneratedEmbeddings<Embedding<float>>(new List<Embedding<float>> { embedding768 });
-        _embeddingGeneratorMock.Setup(g => g.GenerateAsync(
-            It.Is<IEnumerable<string>>(s => s.Contains("test")),
-            It.Is<EmbeddingGenerationOptions>(o => o.Dimensions == 768),
-            It.IsAny<CancellationToken>()))
-            .ReturnsAsync(mockResponse768);
-
-        // Mock 1536-dim fallback embedding generator response
-        var embedding1536 = new Embedding<float>(new float[1536]);
-        var mockResponse1536 = new GeneratedEmbeddings<Embedding<float>>(new List<Embedding<float>> { embedding1536 });
-        _embeddingGeneratorMock.Setup(g => g.GenerateAsync(
-            It.Is<IEnumerable<string>>(s => s.Contains("test")),
-            It.Is<EmbeddingGenerationOptions>(o => o.Dimensions == 1536),
-            It.IsAny<CancellationToken>()))
-            .ReturnsAsync(mockResponse1536);
-
-        // Seed one legacy cache entry
-        using (var context = new AppDbContext(_contextOptions))
         {
-            var cacheEntry = new SemanticKnowledgeCache
+            new SemanticSearchResultDto
             {
-                TenantId = "tenant-123",
                 ContentHash = "hash-123",
-                OriginalText = "Fallback Cache Content Snippet",
+                Snippet = "Semantic search result content snippet",
-                Vector = new Vector(new float[1536]),
+                UnitType = "Concept",
-                PromptVersion = "1",
+                RelevanceScore = 0.95f
-                CreatedAt = DateTime.UtcNow
+            }
-            };
+        };
-            context.SemanticKnowledgeCache.Add(cacheEntry);
-            await context.SaveChangesAsync();
-        }
 
-        var handler = new SearchLibrarySemanticallyQueryHandler(_dbContextFactoryMock.Object, _embeddingGeneratorMock.Object);
+        knowledgeServiceMock.Setup(s => s.SearchLibrarySemanticallyAsync("test", "tenant-123", 5, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(Result.Ok(expectedResults));
+
+        var handler = new SearchLibrarySemanticallyQueryHandler(knowledgeServiceMock.Object);
         var query = new SearchLibrarySemanticallyQuery("test", "tenant-123");
 
         // Act
@@ -161,7 +144,7 @@ public class QueryTests : IDisposable
         // Assert
         result.IsSuccess.Should().BeTrue();
         result.Value.Should().HaveCount(1);
-        result.Value.First().Snippet.Should().Be("Fallback Cache Content Snippet");
+        result.Value.First().Snippet.Should().Be("Semantic search result content snippet");
         result.Value.First().ContentHash.Should().Be("hash-123");
     }