feat: Stream-Error-Info für Debugging bei unexpected_end / max_tokens

- chains Tabelle: neue Spalte stream_error_info (TEXT)
- ChainRecord: neues Property StreamErrorInfo
- AnthropicService/ProcessStream: sammelt Debug-Infos bei problematischen
  stop_reasons (unexpected_end, max_tokens) und API error-Events
- FinalizeChain: speichert stream_error_info in DB
- SSE done-Event: enthält streamErrorInfo für Client-seitiges Debugging

Models/ChainRecord.cs

@@ -18,5 +18,6 @@ public class ChainRecord
     public string ToolChoice { get; set; }
     public string ToolNames { get; set; }
     public string ArchiveId { get; set; }
+    public string StreamErrorInfo { get; set; }
     public string CreatedAt { get; set; }
 }

Services/AnthropicService.cs

@@ -119,7 +119,7 @@ public class AnthropicService
                     return;
                 }
 
-                var (stopReason, assistantContent, executedTools) = await ProcessStream(response, httpResp, usage, workspace, agentId, cancellationToken);
+                var (stopReason, assistantContent, executedTools, streamErrorInfo) = await ProcessStream(response, httpResp, usage, workspace, agentId, cancellationToken);
                 lastStopReason = stopReason;
 
                 messages.Add(new { role = "assistant", content = assistantContent });
@@ -169,7 +169,7 @@ public class AnthropicService
                 if (stopReason != "tool_use")
                 {
                     var finalStopReason = string.IsNullOrEmpty(stopReason) ? "unexpected_end" : stopReason;
-                    await FinalizeChain(chain, usage, iterations, finalStopReason, sw);
+                    await FinalizeChain(chain, usage, iterations, finalStopReason, sw, streamErrorInfo);
                     await TryWriteSse(response, "done", new
                     {
                         model = modelId,
@@ -180,7 +180,8 @@ public class AnthropicService
                         iterations,
                         chainId,
                         durationMs = sw.ElapsedMilliseconds,
-                        stopReason = finalStopReason
+                        stopReason = finalStopReason,
+                        streamErrorInfo
                     }, cancellationToken);
                     return;
                 }
@@ -234,7 +235,7 @@ public class AnthropicService
         }
     }
 
-    private async Task FinalizeChain(ChainRecord chain, TokenUsage usage, int iterations, string stopReason, System.Diagnostics.Stopwatch sw)
+    private async Task FinalizeChain(ChainRecord chain, TokenUsage usage, int iterations, string stopReason, System.Diagnostics.Stopwatch sw, string streamErrorInfo = null)
     {
         chain.InputTokens = usage.InputTokens;
         chain.OutputTokens = usage.OutputTokens;
@@ -242,11 +243,12 @@ public class AnthropicService
         chain.CacheReadTokens = usage.CacheReadTokens;
         chain.Iterations = iterations;
         chain.StopReason = stopReason;
+        chain.StreamErrorInfo = streamErrorInfo;
         chain.DurationMs = sw.ElapsedMilliseconds;
         await _db.UpdateChain(chain);
     }
 
-    private async Task<(string StopReason, List<object> Content, List<ToolResult> Tools)> ProcessStream(
+    private async Task<(string StopReason, List<object> Content, List<ToolResult> Tools, string StreamErrorInfo)> ProcessStream(
         HttpResponse response,
         HttpResponseMessage httpResp,
         TokenUsage usage,
@@ -267,6 +269,7 @@ public class AnthropicService
         var blockTypes = new Dictionary<int, string>();
         var webSearchResultBlocks = new Dictionary<int, object>();
         var executedTools = new List<ToolResult>();
+        var streamErrors = new List<object>();
 
         string line;
         while ((line = await reader.ReadLineAsync(cancellationToken)) != null)
@@ -433,21 +436,66 @@ public class AnthropicService
 
                 case "message_delta":
                 {
-                    if (evt.TryGetProperty("delta", out var d) &&
-                        d.TryGetProperty("stop_reason", out var sr))
-                        stopReason = sr.GetString() ?? "";
+                    if (evt.TryGetProperty("delta", out var d))
+                    {
+                        if (d.TryGetProperty("stop_reason", out var sr))
+                        {
+                            stopReason = sr.GetString() ?? "";
+
+                            // Bei problematischen stop_reasons Debug-Infos sammeln
+                            if (stopReason is "unexpected_end" or "max_tokens")
+                            {
+                                var debugInfo = new Dictionary<string, object>
+                                {
+                                    ["event"] = "message_delta",
+                                    ["stop_reason"] = stopReason,
+                                    ["output_tokens"] = usage.OutputTokens,
+                                    ["text_length"] = currentTextBlock.Length,
+                                    ["timestamp"] = DateTime.UtcNow.ToString("o")
+                                };
+                                if (d.TryGetProperty("stop_sequence", out var ss) && ss.ValueKind != JsonValueKind.Null)
+                                    debugInfo["stop_sequence"] = ss.GetString();
+                                streamErrors.Add(debugInfo);
+                            }
+                        }
+                    }
                     if (evt.TryGetProperty("usage", out var u2) &&
                         u2.TryGetProperty("output_tokens", out var ot))
                         usage.OutputTokens += ot.GetInt64();
                     break;
                 }
+
+                case "error":
+                {
+                    // API Error-Event (z.B. overloaded_error)
+                    var errorInfo = new Dictionary<string, object>
+                    {
+                        ["event"] = "error",
+                        ["timestamp"] = DateTime.UtcNow.ToString("o"),
+                        ["raw"] = data
+                    };
+                    if (evt.TryGetProperty("error", out var err))
+                    {
+                        if (err.TryGetProperty("type", out var errType))
+                            errorInfo["error_type"] = errType.GetString();
+                        if (err.TryGetProperty("message", out var errMsg))
+                            errorInfo["error_message"] = errMsg.GetString();
+                    }
+                    streamErrors.Add(errorInfo);
+                    break;
+                }
             }
         }
 
         if (currentTextBlock.Length > 0)
             assistantContent.Add(new { type = "text", text = currentTextBlock.ToString() });
 
-        return (stopReason, assistantContent, executedTools);
+        // Stream-Fehler als JSON serialisieren (null wenn keine Fehler)
+        string streamErrorInfo = streamErrors.Count > 0
+            ? JsonSerializer.Serialize(streamErrors)
+            : null;
+
+        return (stopReason, assistantContent, executedTools, streamErrorInfo);
     }
 
     private HttpClient CreateClient()

Services/DatabaseService.cs

@@ -140,6 +140,7 @@ public class DatabaseService
             conn.Execute("UPDATE agents SET auto_commit = 'enforce' WHERE auto_commit = '1' OR auto_commit = 1");
         }
         catch { /* already migrated */ }
+        TryAddColumn(conn, "chains", "stream_error_info", "TEXT");
         TryAddColumn(conn, "agents", "use_soul", "INTEGER NOT NULL DEFAULT 1");
         TryAddColumn(conn, "agents", "use_identity", "INTEGER NOT NULL DEFAULT 1");
         TryAddColumn(conn, "agents", "use_user_info", "INTEGER NOT NULL DEFAULT 1");
@@ -459,6 +460,7 @@ public class DatabaseService
                 cache_read_tokens = @CacheReadTokens,
                 iterations = @Iterations,
                 stop_reason = @StopReason,
+                stream_error_info = @StreamErrorInfo,
                 duration_ms = @DurationMs
             WHERE chain_id = @ChainId
         ", chain);