documentation cleanse, sprints work and planning. remaining non EF DAL migration to EF

src/AdvisoryAI/StellaOps.AdvisoryAI.WebService/Endpoints/ChatEndpoints.cs

@@ -21,6 +21,8 @@ using StellaOps.AdvisoryAI.WebService.Security;
 using StellaOps.Auth.ServerIntegration.Tenancy;
 using System.Collections.Immutable;
 using System.Runtime.CompilerServices;
+using System.Security.Cryptography;
+using System.Text;
 using System.Text.Json;
 using static StellaOps.Localization.T;
 
@@ -166,6 +168,17 @@ public static class ChatEndpoints
 
         if (!result.Success)
         {
+            if (!result.GuardrailBlocked && !result.QuotaBlocked && !result.ToolAccessDenied)
+            {
+                logger.LogWarning(
+                    "Chat gateway runtime fallback activated for tenant {TenantId}, user {UserId}. Reason: {Reason}",
+                    tenantId,
+                    userId,
+                    result.Error ?? "processing_failed");
+
+                return Results.Ok(CreateDeterministicFallbackQueryResponse(request, result));
+            }
+
             var statusCode = result.GuardrailBlocked
                 ? StatusCodes.Status400BadRequest
                 : result.QuotaBlocked
@@ -858,6 +871,60 @@ public static class ChatEndpoints
             } : null
         };
     }
+
+    private static AdvisoryChatQueryResponse CreateDeterministicFallbackQueryResponse(
+        AdvisoryChatQueryRequest request,
+        AdvisoryChatServiceResult failedResult)
+    {
+        var diagnostics = failedResult.Diagnostics is null
+            ? null
+            : new DiagnosticsResponse
+            {
+                IntentRoutingMs = failedResult.Diagnostics.IntentRoutingMs,
+                EvidenceAssemblyMs = failedResult.Diagnostics.EvidenceAssemblyMs,
+                InferenceMs = failedResult.Diagnostics.InferenceMs,
+                TotalMs = failedResult.Diagnostics.TotalMs,
+                PromptTokens = failedResult.Diagnostics.PromptTokens,
+                CompletionTokens = failedResult.Diagnostics.CompletionTokens,
+            };
+
+        var reason = string.IsNullOrWhiteSpace(failedResult.Error)
+            ? "chat runtime unavailable"
+            : failedResult.Error.Trim();
+        var normalizedQuery = request.Query?.Trim() ?? string.Empty;
+        var fallbackId = BuildFallbackResponseId(normalizedQuery, reason);
+
+        return new AdvisoryChatQueryResponse
+        {
+            ResponseId = fallbackId,
+            BundleId = null,
+            Intent = (failedResult.Intent ?? AdvisoryChatIntent.General).ToString(),
+            GeneratedAt = DateTimeOffset.UtcNow,
+            Summary =
+                $"Chat runtime is temporarily unavailable. For \"{normalizedQuery}\", start with unified search evidence, verify VEX status, and confirm active policy gates before acting.",
+            Confidence = new ConfidenceResponse { Level = ConfidenceLevel.Low.ToString(), Score = 0.2d },
+            EvidenceLinks = [],
+            Mitigations = [],
+            ProposedActions = [],
+            FollowUp = new FollowUpResponse
+            {
+                SuggestedQueries = [normalizedQuery],
+                NextSteps =
+                [
+                    "Retry this chat query after runtime recovery.",
+                    "Use global search to review findings, VEX, and policy context now."
+                ]
+            },
+            Diagnostics = diagnostics,
+        };
+    }
+
+    private static string BuildFallbackResponseId(string query, string reason)
+    {
+        var bytes = SHA256.HashData(Encoding.UTF8.GetBytes($"{query}|{reason}"));
+        var token = Convert.ToHexString(bytes.AsSpan(0, 8)).ToLowerInvariant();
+        return $"fallback-{token}";
+    }
 }
 
 #region Request/Response DTOs