Stream panel member responses live with a parallel SSE write-lock

Panel members now stream token-by-token and show tool uses in real time
(like the session agent) instead of delivering text only at completion.
The key constraint is byte-level safety: N members flushing SSE frames
concurrently on the shared HttpResponse would interleave and corrupt the
stream, so a SemaphoreSlim gate serializes the writes (not the model work).

- SseHelper.TryWriteSse takes an optional write-lock (default null, backward
  compatible)
- NonStreamingLoopCallbacks carries SseGate + MemberIndex; _text/_tool/_error
  events are tagged with the member index (review/finalizer stay at -1, no gate)
- CLI members forward TextDelta/ToolStart/ToolResult live instead of
  discarding everything but the final text
- Anthropic-API members stream per tool-round via the loop callbacks; OpenAI
  members fall back to collected text at panel_member_done
- Frontend demuxes by member index into per-bubble interleaved text/tool
  rendering

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Services/AnthropicService.Panel.cs

@@ -52,7 +52,12 @@ public partial class AnthropicService
     {
         if (panel == null || panel.Count == 0) return 0;
 
-        await SseHelper.TryWriteSse(response, "panel_start", new { members = panel.Count, mode = "fusion" }, sseCt);
+        // Write-Lock: alle Member streamen LIVE parallel auf DIESELBE HttpResponse →
+        // ohne Serialisierung würden sich ihre SSE-Frames auf Byte-Ebene vermischen.
+        // Serialisiert nur die µs-Byte-Flushes, nicht die parallele Modell-Arbeit.
+        using var sseGate = new SemaphoreSlim(1, 1);
+
+        await SseHelper.TryWriteSse(response, "panel_start", new { members = panel.Count, mode = "fusion" }, sseCt, sseGate);
 
         // Concurrency begrenzen: bei CLI-Membern sind das parallele claude-Children.
         using var sem = new SemaphoreSlim(Math.Min(3, panel.Count));
@@ -64,7 +69,7 @@ public partial class AnthropicService
             tasks.Add(Task.Run(async () =>
             {
                 await sem.WaitAsync(workCt);
-                try { return await RunPanelMember(response, member, workerMessages, index, chainId, sessionId, apiToken, workCt, sseCt); }
+                try { return await RunPanelMember(response, member, workerMessages, index, chainId, sessionId, apiToken, sseGate, workCt, sseCt); }
                 finally { sem.Release(); }
             }, workCt));
         }
@@ -78,7 +83,7 @@ public partial class AnthropicService
 
         if (ordered.Count == 0)
         {
-            await SseHelper.TryWriteSse(response, "panel_done", new { synthesizing = false, members = 0 }, sseCt);
+            await SseHelper.TryWriteSse(response, "panel_done", new { synthesizing = false, members = 0 }, sseCt, sseGate);
             return 0;
         }
 
@@ -103,7 +108,7 @@ public partial class AnthropicService
 
         MergePanelIntoLastUserText(workerMessages, sb.ToString());
 
-        await SseHelper.TryWriteSse(response, "panel_done", new { synthesizing = true, members = ordered.Count }, sseCt);
+        await SseHelper.TryWriteSse(response, "panel_done", new { synthesizing = true, members = ordered.Count }, sseCt, sseGate);
         return ordered.Count;
     }
 
@@ -120,11 +125,12 @@ public partial class AnthropicService
         string chainId,
         string sessionId,
         string apiToken,
+        SemaphoreSlim sseGate,
         CancellationToken workCt,
         CancellationToken sseCt)
     {
         var name = member.Agent?.Name ?? $"Panel-Agent {index + 1}";
-        await SseHelper.TryWriteSse(response, "panel_member_start", new { index, name, model = member.ModelId }, sseCt);
+        await SseHelper.TryWriteSse(response, "panel_member_start", new { index, name, model = member.ModelId }, sseCt, sseGate);
 
         var memberMessages = new List<object>(workerMessages); // eigene Kopie pro Member
         string text;
@@ -139,11 +145,13 @@ public partial class AnthropicService
             else if (string.IsNullOrEmpty(apiToken) && _cliService != null && _cliService.IsAvailable)
             {
                 // Kein API-Key → CLI-Member, read-only (Plan-Modus: nur Read/Glob/Grep).
-                text = await RunPanelMemberViaCli(member, memberMessages, workCt);
+                // Streamt LIVE (Token + Tool-Uses) über panel_member_*-Events.
+                text = await RunPanelMemberViaCli(response, member, memberMessages, index, sseGate, workCt, sseCt);
             }
             else
             {
                 // Anthropic-API-Member: read-only (PlanMode) + NICHT persistieren (Caller persistiert einmal).
+                // Live-Streaming über den Loop: pro Tool-Runde panel_member_text / panel_member_tool.
                 var memberUsage = new TokenUsage();
                 var (t, _) = await RunNonStreamingToolLoop(
                     member.ModelId, member.SystemPrompt,
@@ -155,7 +163,12 @@ public partial class AnthropicService
                     },
                     memberMessages, chainId, sessionId, apiToken, memberUsage,
                     0, 12, workCt,
-                    new NonStreamingLoopCallbacks { Persist = false },
+                    new NonStreamingLoopCallbacks
+                    {
+                        Persist = false,
+                        SseResponse = response, SseCt = sseCt, SseGate = sseGate,
+                        SsePrefix = "panel_member", MemberIndex = index, AgentName = name
+                    },
                     member.Effort);
                 text = t;
             }
@@ -178,17 +191,27 @@ public partial class AnthropicService
         }
 
         await SseHelper.TryWriteSse(response, "panel_member_done",
-            new { index, name, model = member.ModelId, text }, sseCt);
+            new { index, name, model = member.ModelId, text }, sseCt, sseGate);
 
         return new PanelMemberResult { Index = index, Name = name, Model = member.ModelId, Text = text };
     }
 
     /// <summary>
-    /// Führt einen Panel-Member über die Claude CLI aus (read-only via Plan-Modus).
-    /// Sammelt nur den Text, persistiert nichts und sendet keine Text-Deltas
-    /// (parallele Member → Deltas würden interleaven; der volle Text kommt via panel_member_done).
+    /// Führt einen Panel-Member über die Claude CLI aus (read-only via Plan-Modus) und
+    /// streamt seine Arbeit LIVE: Text-Deltas (panel_member_text), Tool-Start
+    /// (panel_member_tool_use) und Tool-Result (panel_member_tool_end) – jeweils mit
+    /// Member-Index, damit das Frontend sie der richtigen Bubble zuordnet. Die SSE-Writes
+    /// laufen durch den geteilten <paramref name="sseGate"/> (parallele Member → sonst
+    /// vermischen sich die Frames). Persistiert nichts – der Caller speichert eine Proposal-Message.
     /// </summary>
-    private async Task<string> RunPanelMemberViaCli(SubAgentContext member, List<object> memberMessages, CancellationToken workCt)
+    private async Task<string> RunPanelMemberViaCli(
+        HttpResponse response,
+        SubAgentContext member,
+        List<object> memberMessages,
+        int index,
+        SemaphoreSlim sseGate,
+        CancellationToken workCt,
+        CancellationToken sseCt)
     {
         if (_cliService == null || !_cliService.IsAvailable) return "";
 
@@ -199,13 +222,29 @@ public partial class AnthropicService
             prompt = $"<conversation_history>\n{historyContext}\n</conversation_history>\n\n<current_request>\n{prompt}\n</current_request>";
 
         var fullText = new StringBuilder();
+        string currentToolName = null; // ToolResult trägt keinen Namen → vom ToolStart merken
         await _cliService.ChatStreamingAsync(
             prompt,
-            evt =>
+            async evt =>
             {
-                if (evt.Type == CliEventType.TextDelta)
-                    fullText.Append(evt.Text);
-                return Task.CompletedTask;
+                switch (evt.Type)
+                {
+                    case CliEventType.TextDelta:
+                        fullText.Append(evt.Text);
+                        await SseHelper.TryWriteSse(response, "panel_member_text",
+                            new { index, text = evt.Text }, sseCt, sseGate);
+                        break;
+                    case CliEventType.ToolStart:
+                        currentToolName = evt.ToolName;
+                        await SseHelper.TryWriteSse(response, "panel_member_tool_use",
+                            new { index, name = evt.ToolName }, sseCt, sseGate);
+                        break;
+                    case CliEventType.ToolResult:
+                        await SseHelper.TryWriteSse(response, "panel_member_tool_end",
+                            new { index, name = currentToolName, result = evt.ToolResultContent, isError = evt.ToolResultIsError }, sseCt, sseGate);
+                        currentToolName = null;
+                        break;
+                }
             },
             modelId: member.ModelId,
             systemPrompt: systemText,