feat: implement multi-tenancy support across knowledge services and normalize TenantId to string type.

src/NexusReader.Infrastructure/DependencyInjection.cs

@@ -74,11 +74,13 @@ public static class DependencyInjection
 
         services.AddScoped<IAuthorizationHandler, ProUserHandler>();
 
-        services.AddMediatR(config => 
-        {
-            config.RegisterServicesFromAssembly(typeof(DependencyInjection).Assembly);
-        });
+        services.AddScoped<IInfrastructureMarker, InfrastructureMarker>();
 
         return services;
     }
+
+    public static System.Reflection.Assembly Assembly => typeof(DependencyInjection).Assembly;
 }
+
+public interface IInfrastructureMarker { }
+internal class InfrastructureMarker : IInfrastructureMarker { }

src/NexusReader.Infrastructure/Persistence/DbInitializer.cs

@@ -44,7 +44,7 @@ public static class DbInitializer
                     EmailConfirmed = true,
                     CurrentPlan = "Enterprise",
                     AITokenLimit = 1000000,
-                    TenantId = Guid.NewGuid()
+                    TenantId = Guid.NewGuid().ToString()
                 };
 
                 var createPowerUser = await userManager.CreateAsync(adminUser, "Admin123!");

src/NexusReader.Infrastructure/Services/KnowledgeService.cs

@@ -43,27 +43,27 @@ public class KnowledgeService : IKnowledgeService
         _tokenizer = TiktokenTokenizer.CreateForModel("gpt-4");
     }
 
-    public async Task<Result<KnowledgePacket>> GetKnowledgeAsync(string text, CancellationToken cancellationToken = default)
+    public async Task<Result<KnowledgePacket>> GetKnowledgeAsync(string text, string tenantId, CancellationToken cancellationToken = default)
     {
-        return await GetKnowledgeInternalAsync(text, PromptRegistry.KnowledgeExtractionSystemPrompt, "full", cancellationToken);
+        return await GetKnowledgeInternalAsync(text, tenantId, PromptRegistry.KnowledgeExtractionSystemPrompt, "full", cancellationToken);
     }
 
-    public async Task<Result<KnowledgePacket>> GetGraphDataAsync(string text, CancellationToken cancellationToken = default)
+    public async Task<Result<KnowledgePacket>> GetGraphDataAsync(string text, string tenantId, CancellationToken cancellationToken = default)
     {
-        return await GetKnowledgeInternalAsync(text, PromptRegistry.GraphExtractionPrompt, "graph", cancellationToken);
+        return await GetKnowledgeInternalAsync(text, tenantId, PromptRegistry.GraphExtractionPrompt, "graph", cancellationToken);
     }
 
-    public async Task<Result<KnowledgePacket>> GetSummaryAndQuizAsync(string text, CancellationToken cancellationToken = default)
+    public async Task<Result<KnowledgePacket>> GetSummaryAndQuizAsync(string text, string tenantId, CancellationToken cancellationToken = default)
     {
-        return await GetKnowledgeInternalAsync(text, PromptRegistry.SummaryAndQuizPrompt, "summary_quiz", cancellationToken);
+        return await GetKnowledgeInternalAsync(text, tenantId, PromptRegistry.SummaryAndQuizPrompt, "summary_quiz", cancellationToken);
     }
 
-    public async Task<Result<KnowledgePacket>> GetKnowledgeMapAsync(string text, CancellationToken cancellationToken = default)
+    public async Task<Result<KnowledgePacket>> GetKnowledgeMapAsync(string text, string tenantId, CancellationToken cancellationToken = default)
     {
-        return await GetKnowledgeInternalAsync(text, PromptRegistry.KM_ExtractionPrompt, "km_map", cancellationToken);
+        return await GetKnowledgeInternalAsync(text, tenantId, PromptRegistry.KM_ExtractionPrompt, "km_map", cancellationToken);
     }
 
-    private async Task<Result<KnowledgePacket>> GetKnowledgeInternalAsync(string text, string systemPrompt, string cacheSuffix, CancellationToken cancellationToken)
+    private async Task<Result<KnowledgePacket>> GetKnowledgeInternalAsync(string text, string tenantId, string systemPrompt, string cacheSuffix, CancellationToken cancellationToken)
     {
         if (string.IsNullOrWhiteSpace(text))
         {
@@ -84,7 +84,7 @@ public class KnowledgeService : IKnowledgeService
 
         // 1. Check Cache
         var cached = await _dbContext.SemanticKnowledgeCache
-            .FirstOrDefaultAsync(c => c.ContentHash == hash && c.PromptVersion == PromptVersion, cancellationToken);
+            .FirstOrDefaultAsync(c => c.ContentHash == hash && c.TenantId == tenantId && c.PromptVersion == PromptVersion, cancellationToken);
 
         if (cached != null)
         {
@@ -146,7 +146,7 @@ public class KnowledgeService : IKnowledgeService
                     OriginalText = normalizedText,
                     ModelId = _settings.Model,
                     PromptVersion = PromptVersion,
-                    TenantId = "global", // Default for shared cache, should be overridden by caller context if possible
+                    TenantId = tenantId,
                     Vector = vector,
                     CreatedAt = DateTime.UtcNow
                 };
@@ -163,7 +163,7 @@ public class KnowledgeService : IKnowledgeService
                 // 5. Process KM-RAG Units and Links if present
                 if (knowledgePacket.Units.Any())
                 {
-                    await ProcessKnowledgeUnitsAsync(knowledgePacket, "global", cancellationToken);
+                    await ProcessKnowledgeUnitsAsync(knowledgePacket, tenantId, cancellationToken);
                 }
 
                 await _dbContext.SaveChangesAsync(cancellationToken);
@@ -191,7 +191,7 @@ public class KnowledgeService : IKnowledgeService
             var unit = existing ?? new KnowledgeUnit { Id = unitId, TenantId = tenantId };
             unit.Type = Enum.TryParse<NexusReader.Domain.Enums.KnowledgeUnitType>(unitDto.Type, true, out var type) ? type : NexusReader.Domain.Enums.KnowledgeUnitType.Snippet;
             unit.Content = unitDto.Content;
-            unit.SourceId = "extracted"; // Should be passed from context
+            unit.SourceId = "extracted";
             unit.MetadataJson = JsonSerializer.Serialize(unitDto.Metadata);
 
             // Generate unit-specific embedding for granular retrieval
@@ -217,6 +217,44 @@ public class KnowledgeService : IKnowledgeService
         }
     }
 
+    public async Task<Result<GroundednessResult>> VerifyGroundednessAsync(string answer, string context, string tenantId, CancellationToken cancellationToken = default)
+    {
+        var systemPrompt = @"
+        You are a Fact-Checking AI. Evaluate if the 'Answer' is supported by the 'Context'.
+        Rate the groundedness from 0.0 to 1.0.
+        Return ONLY a JSON object: { ""score"": 0.9, ""rationale"": ""string"", ""isGrounded"": true }
+        ";
+
+        var userPrompt = $"Context: {context}\n\nAnswer: {answer}";
+
+        try
+        {
+            var options = new ChatOptions
+            {
+                Temperature = 0.0f, // Low temperature for factual checks
+                MaxOutputTokens = 500
+            };
+
+            var response = await _retryPipeline.ExecuteAsync(async ct => 
+                await _chatClient.GetResponseAsync(new List<ChatMessage>
+                {
+                    new ChatMessage(ChatRole.System, systemPrompt),
+                    new ChatMessage(ChatRole.User, userPrompt)
+                }, options, cancellationToken: ct), cancellationToken);
+
+            var rawJson = response.Text?.Trim() ?? "{}";
+            rawJson = rawJson.Replace("```json", "").Replace("```", "").Trim();
+            
+            var result = JsonSerializer.Deserialize<GroundednessResult>(rawJson, new JsonSerializerOptions { PropertyNameCaseInsensitive = true });
+            
+            return result != null ? Result.Ok(result) : Result.Fail("Failed to parse groundedness result");
+        }
+        catch (Exception ex)
+        {
+            return Result.Fail(new Error("Failed to verify groundedness").CausedBy(ex));
+        }
+    }
+
     public async Task<Result<List<RelevantContext>>> GetRelevantContextAsync(string query, string tenantId, CancellationToken cancellationToken = default)
     {
         if (string.IsNullOrWhiteSpace(query)) return Result.Fail("Query is empty.");