gott/Services/AnthropicService.Streaming.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using Gott.Models;
using Microsoft.AspNetCore.Http;

namespace Gott.Services;

public partial class AnthropicService
{
    public async Task StreamChat(
        HttpResponse response,
        string modelId,
        List<object> systemPrompt,
        List<object> messages,
        string chainId,
        string workspace,
        string apiToken,
        string sessionId = null,
        string agentId = null,
        string userId = null,
        bool useMemory = true,
        string webSearchVersion = null,
        int maxIterations = 100,
        string toolChoice = "any",
        SubAgentContext review = null,
        SubAgentContext finalizer = null,
        bool allowUserChoice = true,
        bool planMode = false,
        bool useAutoContext = true,
        bool useGitHubSearch = false,
        bool useSerperSearch = false,
        string effort = null,
        CancellationToken workCt = default,
        CancellationToken hardCt = default,
        CancellationToken sseCt = default,
        RemoteConnectionManager remoteMgr = null)
    {
        var sw = System.Diagnostics.Stopwatch.StartNew();
        var usage = new TokenUsage();
        int iterations = 0;
        int reviewRound = 0;
        string lastStopReason = "";
        int promptTrimRetries = 0;

        var chain = new ChainRecord
        {
            ChainId = chainId,
            SessionId = sessionId,
            Model = modelId
        };

        try
        {
            // ── Automatische Kontext-Injektion via Embedding-Suche ──
            if (useAutoContext)
            {
                try
                {
                    var autoCtx = await BuildAutoContextAsync(_vectorSearch, messages, chainId, agentId);
                    if (autoCtx != null)
                    {
                        systemPrompt.Add(new { type = "text", text = autoCtx });
                        await SseHelper.TryWriteSse(response, "auto_context", new { context = autoCtx }, sseCt);
                        await _db.SaveMessage(new MessageRecord
                        {
                            ChainId = chainId,
                            Role = "system",
                            Type = "auto_context",
                            Content = autoCtx
                        });
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine($"[AutoContext] Error: {ex.Message}");
                }
            }

            while (iterations < maxIterations)
            {
                // Hard-Stop: Sofortiger Abbruch aus while-Loop (Doppel-Klick Stop)
                hardCt.ThrowIfCancellationRequested();
                workCt.ThrowIfCancellationRequested();
                iterations++;

                var payload = new Dictionary<string, object>
                {
                    ["model"] = modelId,
                    ["max_tokens"] = 16384,
                    ["messages"] = messages,
                    ["stream"] = true
                };

                // Reasoning-Effort (Opus 4.5+, Sonnet 4.6+). "" / "high" / null = Default weglassen.
                // Werte: low / medium / high / xhigh (Opus 4.7+) / max (Opus 4.6+, Sonnet 4.6).
                if (!string.IsNullOrEmpty(effort) && effort != "high")
                    payload["output_config"] = new { effort };

                if (systemPrompt != null && systemPrompt.Count > 0)
                {
                    // Cache-Breakpoint auf den letzten System-Prompt-Block (1h TTL).
                    // Idempotent über Iterationen.
                    ApplyCacheControlToLast(systemPrompt);
                    payload["system"] = systemPrompt;
                }

                var remoteConn = remoteMgr?.GetBySessionId(sessionId);
                var hasRemote = remoteConn != null;
                AddToolsToPayload(payload, new ToolPayloadOptions
                {
                    Workspace = workspace,
                    AgentId = agentId,
                    UseMemory = useMemory,
                    WebSearchVersion = webSearchVersion,
                    ToolChoice = toolChoice,
                    Iteration = iterations,
                    AllowUserChoice = allowUserChoice,
                    PlanMode = planMode,
                    IncludeRemote = hasRemote,
                    RemoteOs = remoteConn?.OsVersion,
                    IncludeGitHubSearch = useGitHubSearch && _toolService.HasGitHubToken,
                    IncludeSerperSearch = useSerperSearch && _toolService.HasSerperKey
                });

                var client = CreateClient(apiToken);
                var json = JsonSerializer.Serialize(payload, new JsonSerializerOptions { WriteIndented = true });
                LogPayload(json, sessionId, chainId, iterations);
                var httpContent = new StringContent(json, Encoding.UTF8, "application/json");

                using var httpResp = await client.SendAsync(
                    new HttpRequestMessage(HttpMethod.Post, "https://api.anthropic.com/v1/messages") { Content = httpContent },
                    HttpCompletionOption.ResponseHeadersRead,
                    workCt
                );

                TryUpdateKeyMeta(httpResp, apiToken);

                if (!httpResp.IsSuccessStatusCode)
                {
                    var errBody = await httpResp.Content.ReadAsStringAsync(workCt);
                    var errMsg = $"API {(int)httpResp.StatusCode}: {errBody}";

                    // Auto-Retry bei "prompt too long" / "exceed context limit": History kürzen und erneut versuchen
                    if ((int)httpResp.StatusCode == 400 &&
                        (errBody.Contains("prompt is too long") || errBody.Contains("exceed context limit")) &&
                        messages.Count > 4 && promptTrimRetries < 5)
                    {
                        promptTrimRetries++;
                        int trimCount = Math.Max(2, messages.Count / 5); // 20% der Messages entfernen
                        trimCount = TrimMessagesCleanly(messages, trimCount);
                        if (trimCount > 0)
                        {
                            await SseHelper.TryWriteSse(response, "info", new { message = $"History zu lang – {trimCount} ältere Messages entfernt, Retry ({promptTrimRetries}/5)..." }, sseCt);
                            iterations--; // Iteration nicht zählen, war ja kein echter Versuch
                            continue; // → nächste while-Iteration mit kürzerer History
                        }
                    }

                    await _db.SaveMessage(new MessageRecord
                    {
                        ChainId = chainId, Iteration = iterations,
                        Role = "system", Type = "error",
                        Content = errMsg, IsError = true
                    });
                    await SseHelper.TryWriteSse(response, "error", new { error = errMsg }, sseCt);
                    await FinalizeChain(chain, usage, iterations, "error", sw);
                    await SseHelper.TryWriteSse(response, "done", new { chainId = chain.ChainId }, sseCt);
                    return;
                }

                var (stopReason, assistantContent, executedTools, streamErrorInfo) = await ProcessStream(response, httpResp, usage, workspace, agentId, workCt, sseCt, remoteMgr, sessionId, userId, apiToken);
                lastStopReason = stopReason;
                promptTrimRetries = 0; // Erfolgreicher API-Call → Retry-Counter resetten

                messages.Add(new { role = "assistant", content = assistantContent });

                // Assistant-Blöcke persistieren
                foreach (var block in assistantContent)
                {
                    var blockJson = JsonSerializer.Serialize(block);
                    var el = JsonSerializer.Deserialize<JsonElement>(blockJson);
                    var blockType = el.GetProperty("type").GetString() ?? "";

                    if (blockType == "text")
                    {
                        var textContent = el.GetProperty("text").GetString();
                        var msgId = await _db.SaveMessage(new MessageRecord
                        {
                            ChainId = chainId, Iteration = iterations,
                            Role = "assistant", Type = "text",
                            Content = textContent
                        });
                        _embeddingBg?.Enqueue(msgId, chainId, sessionId, agentId, "assistant", textContent ?? "");
                    }
                    else if (blockType == "tool_use")
                    {
                        await _db.SaveMessage(new MessageRecord
                        {
                            ChainId = chainId, Iteration = iterations,
                            Role = "assistant", Type = "tool_use",
                            ToolName = el.GetProperty("name").GetString(),
                            ToolCallId = el.GetProperty("id").GetString(),
                            Content = el.GetProperty("input").ToString()
                        });
                    }
                    else if (blockType == "server_tool_use")
                    {
                        await _db.SaveMessage(new MessageRecord
                        {
                            ChainId = chainId, Iteration = iterations,
                            Role = "assistant", Type = "server_tool_use",
                            Content = el.GetRawText()
                        });
                    }
                    else if (blockType == "web_search_tool_result")
                    {
                        // Raw-JSON speichern für History-Rebuild (API braucht den vollständigen Block)
                        await _db.SaveMessage(new MessageRecord
                        {
                            ChainId = chainId, Iteration = iterations,
                            Role = "assistant", Type = "web_search_result",
                            Content = el.GetRawText()
                        });
                    }
                    else if (blockType.EndsWith("_tool_result"))
                    {
                        // Generische Server-Tool-Results (bash_code_execution_tool_result, code_execution_tool_result etc.)
                        await _db.SaveMessage(new MessageRecord
                        {
                            ChainId = chainId, Iteration = iterations,
                            Role = "assistant", Type = "server_tool_result",
                            Content = el.GetRawText()
                        });
                    }
                }

                // Tool Results persistieren
                foreach (var tr in executedTools)
                {
                    await _db.SaveMessage(new MessageRecord
                    {
                        ChainId = chainId, Iteration = iterations,
                        Role = "user", Type = "tool_result",
                        ToolCallId = tr.Id,
                        Content = tr.Result,
                        IsError = tr.IsError
                    });
                }

                if (stopReason != "tool_use")
                {
                    // ── Review-Agent Phase ──
                    if (review != null && stopReason == "end_turn" && reviewRound < review.MaxReviewIterations)
                    {
                        var reviewResult = await RunReview(response, review, messages, chainId, workspace, sessionId, apiToken, usage, iterations, reviewRound, workCt, sseCt);
                        iterations += reviewResult.ReviewIterationCount;
                        reviewRound++;

                        if (reviewResult.HasFeedback)
                        {
                            // Feedback als User-Message an Worker zurückgeben → nächste Iteration
                            messages.Add(new Dictionary<string, object>
                            {
                                ["role"] = "user",
                                ["content"] = new List<object> { new { type = "text", text = reviewResult.Feedback } }
                            });
                            await _db.SaveMessage(new MessageRecord
                            {
                                ChainId = chainId, Iteration = iterations,
                                Role = "user", Type = "text",
                                Content = reviewResult.Feedback
                            });
                            continue; // → nächste Worker-Iteration
                        }
                    }

                    // ── Finalizer-Agent Phase ──
                    if (finalizer != null && stopReason == "end_turn")
                    {
                        var finalizerIterations = await RunFinalizer(response, finalizer, messages, chainId, workspace, sessionId, apiToken, usage, iterations, workCt, sseCt);
                        iterations += finalizerIterations;
                    }

                    var finalStopReason = string.IsNullOrEmpty(stopReason) ? "unexpected_end" : stopReason;
                    await FinalizeChain(chain, usage, iterations, finalStopReason, sw, streamErrorInfo);
                    await SseHelper.TryWriteSse(response, "done", new
                    {
                        model = modelId,
                        inputTokens = usage.InputTokens,
                        outputTokens = usage.OutputTokens,
                        cacheCreationTokens = usage.CacheCreationTokens,
                        cacheReadTokens = usage.CacheReadTokens,
                        iterations,
                        chainId,
                        durationMs = sw.ElapsedMilliseconds,
                        stopReason = finalStopReason,
                        streamErrorInfo,
                        planMode,
                        effort
                    }, sseCt);
                    return;
                }

                var toolResults = new List<object>();
                foreach (var tr in executedTools)
                {
                    toolResults.Add(new
                    {
                        type = "tool_result",
                        tool_use_id = tr.Id,
                        content = TruncateToolResult(tr.Result),
                        is_error = tr.IsError
                    });
                }

                messages.Add(new { role = "user", content = toolResults });

                // Hard-Stop Check nach Tool-Ausführung: Sofort raus statt nächste Iteration
                hardCt.ThrowIfCancellationRequested();
            }

            await FinalizeChain(chain, usage, iterations, "max_iterations", sw);
            await SseHelper.TryWriteSse(response, "error", new { error = "Max iterations erreicht" }, sseCt);
            await SseHelper.TryWriteSse(response, "done", new { chainId = chain.ChainId }, sseCt);
        }
        catch (OperationCanceledException) when (workCt.IsCancellationRequested || hardCt.IsCancellationRequested)
        {
            // Stop-Button gedrückt (workCt oder hardCt wurde gecancelled)
            await FinalizeChain(chain, usage, iterations, "stopped", sw);
            // sseCt ist hier bereits cancelled (gelinkt mit workCt), daher CancellationToken.None
            // Der SSE-Stream zum Client ist noch offen – nur der Stop-Button hat ausgelöst
            await SseHelper.TryWriteSse(response, "done", new
            {
                model = modelId,
                inputTokens = usage.InputTokens,
                outputTokens = usage.OutputTokens,
                cacheCreationTokens = usage.CacheCreationTokens,
                cacheReadTokens = usage.CacheReadTokens,
                iterations,
                chainId,
                durationMs = sw.ElapsedMilliseconds,
                stopReason = "stopped",
                planMode,
                effort
            }, CancellationToken.None);
        }
        catch (Exception) when (workCt.IsCancellationRequested || hardCt.IsCancellationRequested)
        {
            // Stream-Dispose durch CancellationToken-Registration löst
            // ObjectDisposedException/IOException aus statt OperationCanceledException.
            // Wenn workCt/hardCt gecancelled ist, ist das ein regulärer Stop.
            await FinalizeChain(chain, usage, iterations, "stopped", sw);
            // sseCt ist hier bereits cancelled (gelinkt mit workCt), daher CancellationToken.None
            await SseHelper.TryWriteSse(response, "done", new
            {
                model = modelId,
                inputTokens = usage.InputTokens,
                outputTokens = usage.OutputTokens,
                cacheCreationTokens = usage.CacheCreationTokens,
                cacheReadTokens = usage.CacheReadTokens,
                iterations,
                chainId,
                durationMs = sw.ElapsedMilliseconds,
                stopReason = "stopped",
                planMode,
                effort
            }, CancellationToken.None);
        }
        catch (OperationCanceledException)
        {
            // Client-Disconnect (cancellationToken gecancelled, aber NICHT workCt/hardCt)
            // Agent-Arbeit ist leider schon abgebrochen – Chain als "client_disconnected" finalisieren
            // (sollte durch TryWriteSse eigentlich nicht mehr passieren)
            await FinalizeChain(chain, usage, iterations, "client_disconnected", sw);
        }
        catch (Exception ex)
        {
            // Unerwarteter Fehler – in DB speichern und versuchen an Client zu senden
            var errMsg = $"Stream-Fehler: {ex.Message}";
            await _db.SaveMessage(new MessageRecord
            {
                ChainId = chainId, Iteration = iterations,
                Role = "system", Type = "error",
                Content = errMsg, IsError = true
            });
            await FinalizeChain(chain, usage, iterations, "error", sw);
            await SseHelper.TryWriteSse(response, "error", new { error = errMsg }, sseCt);
            await SseHelper.TryWriteSse(response, "done", new { chainId = chain.ChainId }, sseCt);
        }
    }

    private async Task<(string StopReason, List<object> Content, List<ToolResult> Tools, string StreamErrorInfo)> ProcessStream(
        HttpResponse response,
        HttpResponseMessage httpResp,
        TokenUsage usage,
        string workspace,
        string agentId = null,
        CancellationToken workCt = default,
        CancellationToken sseCt = default,
        RemoteConnectionManager remoteMgr = null,
        string sessionId = null,
        string userId = null,
        string apiToken = null)
    {
        var stream = await httpResp.Content.ReadAsStreamAsync(workCt);
        // Bei Cancellation den Stream disposen, damit ReadLineAsync sofort abbricht.
        // StreamReader.ReadLineAsync propagiert den CancellationToken nicht zuverlässig
        // an den underlying NetworkStream – der Read blockiert sonst bis Anthropic
        // das nächste Chunk sendet (kann bei extended thinking Minuten dauern).
        using var ctReg = workCt.Register(() => { try { stream.Dispose(); } catch { } });
        using var reader = new StreamReader(stream);

        var stopReason = "";
        var assistantContent = new List<object>();
        var currentToolId = "";
        var currentToolName = "";
        var currentToolInputJson = new StringBuilder();
        var currentTextBlock = new StringBuilder();

        var blockTypes = new Dictionary<int, string>();
        var webSearchResultBlocks = new Dictionary<int, object>();
        var webSearchSources = new Dictionary<int, List<object>>();
        var serverToolResultBlocks = new Dictionary<int, object>(); // bash_code_execution_tool_result, code_execution_tool_result etc.
        var executedTools = new List<ToolResult>();
        var streamErrors = new List<object>();

        string line;
        while ((line = await reader.ReadLineAsync(workCt)) != null)
        {
            if (!line.StartsWith("data: ")) continue;
            var data = line["data: ".Length..];
            if (string.IsNullOrWhiteSpace(data)) continue;

            JsonElement evt;
            try { evt = JsonSerializer.Deserialize<JsonElement>(data); }
            catch { continue; }

            var evtType = evt.TryGetProperty("type", out var t) ? t.GetString() ?? "" : "";

            switch (evtType)
            {
                case "message_start":
                {
                    if (evt.TryGetProperty("message", out var msg) &&
                        msg.TryGetProperty("usage", out var u))
                        TrackUsage(usage, u);
                    break;
                }

                case "content_block_start":
                {
                    var idx = evt.GetProperty("index").GetInt32();
                    var cb = evt.GetProperty("content_block");
                    var cbType = cb.GetProperty("type").GetString() ?? "";
                    blockTypes[idx] = cbType;

                    if (cbType == "text")
                    {
                        currentTextBlock.Clear();
                        await SseHelper.TryWriteSse(response, "text_start", new { index = idx }, sseCt);
                    }
                    else if (cbType == "tool_use")
                    {
                        if (currentTextBlock.Length > 0)
                        {
                            assistantContent.Add(new { type = "text", text = currentTextBlock.ToString() });
                            currentTextBlock.Clear();
                        }
                        currentToolId = cb.GetProperty("id").GetString() ?? "";
                        currentToolName = cb.GetProperty("name").GetString() ?? "";
                        currentToolInputJson.Clear();
                        await SseHelper.TryWriteSse(response, "tool_start", new { name = currentToolName, id = currentToolId }, sseCt);
                    }
                    else if (cbType == "server_tool_use")
                    {
                        if (currentTextBlock.Length > 0)
                        {
                            assistantContent.Add(new { type = "text", text = currentTextBlock.ToString() });
                            currentTextBlock.Clear();
                        }
                        currentToolId = cb.GetProperty("id").GetString() ?? "";
                        currentToolName = cb.GetProperty("name").GetString() ?? "";
                        currentToolInputJson.Clear();
                        await SseHelper.TryWriteSse(response, "web_search_start", new { name = currentToolName, id = currentToolId }, sseCt);
                    }
                    else if (cbType == "web_search_tool_result")
                    {
                        var rawBlock = JsonSerializer.Deserialize<JsonElement>(cb.GetRawText());
                        webSearchResultBlocks[idx] = rawBlock;
                        webSearchSources[idx] = ExtractWebSearchSources(cb);
                    }
                    else if (cbType.EndsWith("_tool_result"))
                    {
                        // Generische Server-Tool-Results (bash_code_execution_tool_result, code_execution_tool_result etc.)
                        serverToolResultBlocks[idx] = JsonSerializer.Deserialize<JsonElement>(cb.GetRawText());
                    }
                    break;
                }

                case "content_block_delta":
                {
                    var delta = evt.GetProperty("delta");
                    var deltaType = delta.GetProperty("type").GetString() ?? "";

                    if (deltaType == "text_delta")
                    {
                        var text = delta.GetProperty("text").GetString() ?? "";
                        currentTextBlock.Append(text);
                        await SseHelper.TryWriteSse(response, "text_delta", new { text }, sseCt);
                    }
                    else if (deltaType == "input_json_delta")
                    {
                        var partial = delta.GetProperty("partial_json").GetString() ?? "";
                        currentToolInputJson.Append(partial);
                    }
                    break;
                }

                case "content_block_stop":
                {
                    var idx = evt.GetProperty("index").GetInt32();
                    if (blockTypes.TryGetValue(idx, out var bt))
                    {
                        if (bt == "text")
                        {
                            var text = currentTextBlock.ToString();
                            if (text.Length > 0)
                            {
                                assistantContent.Add(new { type = "text", text });
                                await SseHelper.TryWriteSse(response, "text_end", new { }, sseCt);
                            }
                            currentTextBlock.Clear();
                        }
                        else if (bt == "tool_use")
                        {
                            JsonElement inputEl;
                            try { inputEl = JsonSerializer.Deserialize<JsonElement>(currentToolInputJson.ToString()); }
                            catch { inputEl = JsonSerializer.Deserialize<JsonElement>("{}"); }

                            assistantContent.Add(new
                            {
                                type = "tool_use",
                                id = currentToolId,
                                name = currentToolName,
                                input = inputEl
                            });

                            // ask_user_choice: NICHT ausführen, sondern als SSE-Event an Client senden
                            if (currentToolName == ToolService.AskUserChoiceToolName)
                            {
                                var question = inputEl.TryGetProperty("question", out var q) ? q.GetString() ?? "" : "";
                                var choices = new List<string>();
                                if (inputEl.TryGetProperty("choices", out var c))
                                {
                                    if (c.ValueKind == JsonValueKind.Array)
                                    {
                                        foreach (var ch in c.EnumerateArray())
                                            choices.Add(ch.GetString() ?? "");
                                    }
                                    else if (c.ValueKind == JsonValueKind.String)
                                    {
                                        // Fallback: Claude hat einen einzelnen String statt Array gesendet
                                        choices.Add(c.GetString() ?? "");
                                    }
                                }

                                await SseHelper.TryWriteSse(response, "user_choice", new
                                {
                                    toolCallId = currentToolId,
                                    question,
                                    choices
                                }, sseCt);

                                // Stream restlich konsumieren ohne weitere Verarbeitung
                                // (Claude sendet nach dem tool_use noch message_delta mit stop_reason)
                                stopReason = "awaiting_user_choice";
                                continue;
                            }

                            // Cancellation prüfen bevor Tool ausgeführt wird
                            workCt.ThrowIfCancellationRequested();

                            string toolResult;
                            bool isError = false;
                            try { toolResult = await _toolService.ExecuteTool(currentToolName, inputEl, new ToolExecutionContext
                            {
                                Workspace = workspace, MemoryService = _memoryService, AgentId = agentId,
                                CancellationToken = workCt, RemoteMgr = remoteMgr, SessionId = sessionId,
                                VectorSearch = _vectorSearch, EmbeddingBg = _embeddingBg, Db = _db,
                                ChatService = _chatService, AnthropicService = this, OpenAiService = _openAiService,
                                UserId = userId, TelegramService = _telegramService, ApiToken = apiToken
                            }); }
                            catch (OperationCanceledException) { throw; }
                            catch (Exception ex) { toolResult = $"Fehler: {ex.Message}"; isError = true; }

                            workCt.ThrowIfCancellationRequested();
                            executedTools.Add(new ToolResult(currentToolId, toolResult, isError));

                            await SseHelper.TryWriteSse(response, "tool_end", new
                            {
                                name = currentToolName,
                                input = currentToolInputJson.ToString(),
                                result = toolResult,
                                isError
                            }, sseCt);
                        }
                        else if (bt == "server_tool_use")
                        {
                            // Server-side tool (Web Search) – Anthropic führt es aus, wir speichern nur die Anfrage
                            JsonElement inputEl;
                            try { inputEl = JsonSerializer.Deserialize<JsonElement>(currentToolInputJson.ToString()); }
                            catch { inputEl = JsonSerializer.Deserialize<JsonElement>("{}"); }

                            assistantContent.Add(new
                            {
                                type = "server_tool_use",
                                id = currentToolId,
                                name = currentToolName,
                                input = inputEl
                            });
                        }
                        else if (bt == "web_search_tool_result")
                        {
                            // Web-Search-Ergebnis von Anthropic – als Raw-JSON in assistantContent aufnehmen
                            assistantContent.Add(webSearchResultBlocks[idx]);
                            var sources = webSearchSources.TryGetValue(idx, out var s) ? s : new List<object>();
                            await SseHelper.TryWriteSse(response, "web_search_end", new { id = currentToolId, sources }, sseCt);
                        }
                        else if (bt.EndsWith("_tool_result") && serverToolResultBlocks.TryGetValue(idx, out var srvResultBlock))
                        {
                            // Generische Server-Tool-Results (bash_code_execution_tool_result, code_execution_tool_result etc.)
                            assistantContent.Add(srvResultBlock);
                        }
                    }
                    break;
                }

                case "message_delta":
                {
                    if (evt.TryGetProperty("delta", out var d))
                    {
                        if (d.TryGetProperty("stop_reason", out var sr))
                        {
                            // Nicht überschreiben wenn bereits auf awaiting_user_choice gesetzt
                            if (stopReason != "awaiting_user_choice")
                                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() });

        // Stream-Fehler als JSON serialisieren (null wenn keine Fehler)
        string streamErrorInfo = streamErrors.Count > 0
            ? JsonSerializer.Serialize(streamErrors)
            : null;

        return (stopReason, assistantContent, executedTools, streamErrorInfo);
    }

    /// <summary>
    /// Extrahiert Web-Search-Sources aus einem web_search_tool_result-Block.
    /// </summary>
    private static List<object> ExtractWebSearchSources(JsonElement block)
    {
        var sources = new List<object>();
        if (block.TryGetProperty("content", out var searchContent) && searchContent.ValueKind == JsonValueKind.Array)
        {
            foreach (var item in searchContent.EnumerateArray())
            {
                var itemType = item.TryGetProperty("type", out var it) ? it.GetString() : "";
                if (itemType == "web_search_result")
                {
                    var url = item.TryGetProperty("url", out var u) ? u.GetString() ?? "" : "";
                    var title = item.TryGetProperty("title", out var tt) ? tt.GetString() ?? "" : "";
                    if (!string.IsNullOrEmpty(url))
                        sources.Add(new { url, title });
                }
            }
        }
        return sources;
    }

    /// <summary>
    /// Parst einen server_tool_use-Block und gibt (id, name, input) zurück.
    /// </summary>
    private static (string id, string name, JsonElement input) ParseServerToolUse(JsonElement block)
    {
        var toolId = block.GetProperty("id").GetString() ?? "";
        var toolName = block.GetProperty("name").GetString() ?? "";
        JsonElement inputEl;
        try { inputEl = block.GetProperty("input"); }
        catch { inputEl = JsonSerializer.Deserialize<JsonElement>("{}"); }
        return (toolId, toolName, inputEl);
    }

    /// <summary>
    /// Aktualisiert den TokenUsage-Tracker aus einem usage-JSON-Element.
    /// </summary>
    private static void TrackUsage(TokenUsage usage, JsonElement u)
    {
        if (u.TryGetProperty("input_tokens", out var it)) usage.InputTokens += it.GetInt64();
        if (u.TryGetProperty("output_tokens", out var ot)) usage.OutputTokens += ot.GetInt64();
        if (u.TryGetProperty("cache_creation_input_tokens", out var cc)) usage.CacheCreationTokens += cc.GetInt64();
        if (u.TryGetProperty("cache_read_input_tokens", out var cr)) usage.CacheReadTokens += cr.GetInt64();
    }
}