Retry analytics on concurrent-modification conflicts instead of erroring

The reconciliation worker resets position checkpoints via bulk UPDATE while
the analytics worker saves recalculated positions for the same trader —
MySQL then rejects the stale save ("Record has changed since last read").
The engine run is now retried once with a fresh context (re-reading the
concurrent change); if it still collides, it logs a warning and lets the
next cycle pick the trader up again (LastAnalyzedAt stays unset).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/Predictalytics.Worker/Services/TraderAnalyticsWorker.cs

@@ -86,9 +86,33 @@ public class TraderAnalyticsWorker : BackgroundService
             _logger.LogInformation("Found {Count} active or unanalyzed traders to update", traderIds.Count);
         }
 
+        async Task MarkJobFailedAsync(int traderId, Exception ex)
+        {
+            if (activeJob != null && activeJob.TraderId == traderId)
+            {
+                try
+                {
+                    using var jobScope = _services.CreateScope();
+                    var updateJobRepo = jobScope.ServiceProvider.GetRequiredService<IJobRepository>();
+                    activeJob.Status = Predictalytics.Domain.Enums.JobStatus.Failed;
+                    activeJob.CompletedAt = DateTime.UtcNow;
+                    activeJob.ErrorMessage = ex.Message;
+                    await updateJobRepo.UpdateAsync(activeJob, CancellationToken.None);
+                }
+                catch { /* Ignore secondary errors */ }
+            }
+        }
+
         foreach (var id in traderIds)
         {
             if (ct.IsCancellationRequested) break;
+
+            // Concurrent writers (reconciliation checkpoint resets, pollers) can touch the
+            // same TraderPositions/Traders rows mid-save ("Record has changed since last
+            // read"). A retry with a fresh context re-reads their changes and succeeds.
+            const int maxAttempts = 2;
+            for (int attempt = 1; attempt <= maxAttempts; attempt++)
+            {
             try
             {
                 using var traderScope = _services.CreateScope();
@@ -149,27 +173,38 @@ public class TraderAnalyticsWorker : BackgroundService
                     activeJob.CompletedAt = DateTime.UtcNow;
                     await updateJobRepo.UpdateAsync(activeJob, ct);
                 }
+
+                break; // trader done
             }
             catch (OperationCanceledException) when (ct.IsCancellationRequested)
             {
                 _logger.LogInformation("Cancellation requested during analysis, stopping batch.");
                 break;
             }
+            catch (DbUpdateException ex) when (attempt < maxAttempts)
+            {
+                _logger.LogWarning("Concurrent modification while analyzing trader {TraderId} — retrying with a fresh context. ({Message})",
+                    id, ex.InnerException?.Message ?? ex.Message);
+                await Task.Delay(250, CancellationToken.None);
+            }
+            catch (DbUpdateException ex)
+            {
+                // Still colliding after the retry. LastAnalyzedAt stays unset, so this
+                // trader is picked up again next cycle — a warning is enough.
+                _logger.LogWarning("Trader {TraderId} skipped after repeated concurrent modifications — will retry next cycle. ({Message})",
+                    id, ex.InnerException?.Message ?? ex.Message);
+                await MarkJobFailedAsync(id, ex);
+                break;
+            }
             catch (Exception ex)
             {
                 _logger.LogError(ex, "Error recalculating positions/PnL for trader {TraderId}", id);
-                if (activeJob != null && activeJob.TraderId == id)
+                await MarkJobFailedAsync(id, ex);
-                {
+                break;
-                    try {
-                        using var jobScope = _services.CreateScope();
-                        var updateJobRepo = jobScope.ServiceProvider.GetRequiredService<IJobRepository>();
-                        activeJob.Status = Predictalytics.Domain.Enums.JobStatus.Failed;
-                        activeJob.CompletedAt = DateTime.UtcNow;
-                        activeJob.ErrorMessage = ex.Message;
-                        await updateJobRepo.UpdateAsync(activeJob, CancellationToken.None);
-                    } catch { /* Ignore secondary errors */ }
-                }
             }
+            }
+
+            if (ct.IsCancellationRequested) break;
         }
 
         if (traderIds.Count > 0)