Surface Membase error details and skip retries on Membase - query execution errors

src/Plugins/BotSharp.Plugin.Membase/Controllers/MembaseController.cs

@@ -1,4 +1,5 @@
 using Microsoft.AspNetCore.Http;
+using ApiException = Refit.ApiException;
 
 namespace BotSharp.Plugin.Membase.Controllers;
 
@@ -91,9 +92,7 @@ public async Task<IActionResult> ExecuteGraphQuery(string graphId, [FromBody] Cy
         }
         catch (Exception ex)
         {
-            return StatusCode(
-                StatusCodes.Status500InternalServerError,
-                new { message = "An error occurred while executing the query.", error = ex.Message });
+            return ErrorResult(ex, "An error occurred while executing the query.");
         }
     }
 
@@ -594,4 +593,48 @@ public async Task<IActionResult> ValidatePgtDefinition(string graphId, string de
                 new { message = "An error occurred while validating the PGT definition.", error = ex.Message });
         }
     }
+
+    /// <summary>
+    /// Build a 500 response. "message" always carries the generic per-endpoint description;
+    /// "error" carries the concrete cause — for a Refit ApiException that is the "detail"
+    /// field of the upstream Membase problem-details body (falling back to the exception
+    /// message when the upstream body has no usable detail).
+    /// </summary>
+    private ObjectResult ErrorResult(Exception ex, string message)
+    {
+        var error = ex.Message;
+
+        if (ex is ApiException apiEx)
+        {
+            var detail = GetUpstreamDetail(apiEx.Content);
+            if (!string.IsNullOrWhiteSpace(detail))
+            {
+                error = detail;
+            }
+        }
+
+        return StatusCode(StatusCodes.Status500InternalServerError, new { message, error });
+    }
+
+    private static string? GetUpstreamDetail(string? content)
+    {
+        if (string.IsNullOrWhiteSpace(content))
+        {
+            return null;
+        }
+
+        try
+        {
+            using var doc = JsonDocument.Parse(content);
+            return doc.RootElement.ValueKind == JsonValueKind.Object
+                && doc.RootElement.TryGetProperty("detail", out var detail)
+                && detail.ValueKind == JsonValueKind.String
+                ? detail.GetString()
+                : null;
+        }
+        catch (JsonException)
+        {
+            return null;
+        }
+    }
 }

src/Plugins/BotSharp.Plugin.Membase/GraphDb/MembaseGraphDb.cs

@@ -13,6 +13,9 @@ public partial class MembaseGraphDb : IGraphDb
     private readonly IMembaseApi _membaseApi;
 
     private const int RETRY_COUNT = 3;
+    // Membase reports Cypher compile/runtime failures as HTTP 500 problem details with this title.
+    // Those failures are deterministic, so retrying them only delays the error.
+    private const string QUERY_EXECUTION_ERROR_TITLE = "Query Execution Error";
 
     public MembaseGraphDb(
         IServiceProvider services,
@@ -155,7 +158,7 @@ private AsyncPolicy BuildRetryPolicy()
             .Handle<HttpRequestException>()
             .Or<TaskCanceledException>()
             .Or<TimeoutRejectedException>()
-            .Or<ApiException>(ex => ex.StatusCode == HttpStatusCode.ServiceUnavailable || ex.StatusCode == HttpStatusCode.InternalServerError)
+            .Or<ApiException>(IsTransientApiException)
             .WaitAndRetryAsync(
                 retryCount: RETRY_COUNT,
                 sleepDurationProvider: retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)),
@@ -168,5 +171,41 @@ private AsyncPolicy BuildRetryPolicy()
 
         return Policy.WrapAsync(retryPolicy, timeoutPolicy);
     }
+
+    private static bool IsTransientApiException(ApiException ex)
+    {
+        switch (ex.StatusCode)
+        {
+            case HttpStatusCode.BadGateway:
+            case HttpStatusCode.ServiceUnavailable:
+            case HttpStatusCode.GatewayTimeout:
+                return true;
+            case HttpStatusCode.InternalServerError:
+                return !IsQueryExecutionError(ex.Content);
+            default:
+                return false;
+        }
+    }
+
+    private static bool IsQueryExecutionError(string? content)
+    {
+        if (string.IsNullOrWhiteSpace(content))
+        {
+            return false;
+        }
+
+        try
+        {
+            using var doc = JsonDocument.Parse(content);
+            return doc.RootElement.ValueKind == JsonValueKind.Object
+                && doc.RootElement.TryGetProperty("title", out var title)
+                && title.ValueKind == JsonValueKind.String
+                && string.Equals(title.GetString(), QUERY_EXECUTION_ERROR_TITLE, StringComparison.OrdinalIgnoreCase);
+        }
+        catch (JsonException)
+        {
+            return false;
+        }
+    }
     #endregion
 }