feat(ai): configurable tool-call limit (0=unlimited) + Stop button

Replace the fixed 30-round cap with a Settings value (AiMaxToolRounds,
Settings → AI Assistant). 0 = unlimited, for long automation runs left
going for hours. The chat's Send button turns into Stop while the agent
is running so any run — bounded or unlimited — can be aborted (via the
CancellationToken; the loop also checks it each round).

Docs: ARCHITECTURE gains the configurable-limit note and a generic
"pair with a self-hosted gateway = hardware assistant" usage section
(no private endpoints).

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

src/ETTerms/Ai/AgentHost.cs

@@ -14,9 +14,9 @@ public sealed class AgentHost
     private readonly OpenAiChatClient _client;
     private readonly AiTools _tools;
     private readonly JsonArray _messages = new();
-    // 單次 SendAsync 的工具呼叫輪數上限（防失控迴圈的保險）。硬體任務常需多輪
-    // （逐一操作多個 port、多次讀寫、power-cycle 等待…）,故放寬到 30。
-    private const int MaxToolRounds = 30;
+    // 單次 SendAsync 的工具呼叫輪數上限（防失控迴圈的保險）。由 Settings 設定,
+    // 0 = 無上限（自動化長跑用；執行中可按 Stop 中止,取消透過 CancellationToken）。
+    private readonly int _maxRounds;
 
     public event Action<string>? AssistantText;   // 最終文字回應
     public event Action<string>? ToolActivity;     // 「呼叫 serial_write …」之類過程
@@ -28,10 +28,11 @@ public sealed class AgentHost
         "破壞性動作（關插座 / power-cycle）會由使用者在 GUI 確認,你只需正常呼叫工具。" +
         "serial 操作前必須先 serial_attach 到 GUI 已開啟的 session。";
 
-    public AgentHost(OpenAiChatClient client, AiTools tools, string? systemPrompt)
+    public AgentHost(OpenAiChatClient client, AiTools tools, string? systemPrompt, int maxRounds)
     {
         _client = client;
         _tools = tools;
+        _maxRounds = maxRounds;
         _messages.Add(new JsonObject
         {
             ["role"] = "system",
@@ -45,8 +46,10 @@ public sealed class AgentHost
         _messages.Add(new JsonObject { ["role"] = "user", ["content"] = userText });
         var tools = _tools.GetSchemas();
 
-        for (int round = 0; round < MaxToolRounds; round++)
+        // _maxRounds <= 0 → 無上限（自動化長跑；靠 Stop / CancellationToken 中止）
+        for (int round = 0; _maxRounds <= 0 || round < _maxRounds; round++)
         {
+            ct.ThrowIfCancellationRequested();
             Status?.Invoke("thinking");
             var msg = await _client.CompleteAsync(_messages, tools, ct);
             _messages.Add((JsonObject)msg.DeepClone());
@@ -85,7 +88,7 @@ public sealed class AgentHost
             }
         }
 
-        AssistantText?.Invoke("（已達工具呼叫上限,停止。請縮小問題或分步再試。）");
+        AssistantText?.Invoke($"（已達工具呼叫上限 {_maxRounds} 次,停止。可到 Settings → AI Assistant 調高或設 0 = 無上限,或分步再試。）");
         Status?.Invoke("done");
     }
 }

src/ETTerms/App/AboutView.cs

@@ -188,6 +188,7 @@ public sealed class AboutView : UserControl
             "The AI Chat pane now renders proper chat bubbles (your messages on the right, the AI's on the left) with full Markdown — code blocks, tables, lists and inline `code` all display nicely.",
             "When you send a prompt, an animated \"…\" thinking bubble appears while the AI works and disappears the moment the reply arrives — so you always know it's running.",
             "Under the hood this uses WebView2 (built into Windows 11); the model dropdown, [AI] serial tagging, and PDU confirmations all work exactly as before.",
+            "New setting: Max tool calls per message (Settings → AI Assistant). Set it to 0 for unlimited — handy for long automation runs you leave going — and press Stop in the chat to abort any run in progress.",
         ]),
         new("0.6.0", new DateOnly(2026, 7, 5), "Built-in AI Assistant — drive serial & PDU in plain language",
         [

src/ETTerms/App/AiChatView.cs

@@ -57,7 +57,7 @@ public sealed class AiChatView : UserControl
         };
         _input.KeyDown += (_, e) =>
         {
-            if (e.KeyCode == Keys.Enter && !e.Shift) { e.Handled = e.SuppressKeyPress = true; OnSend(); }
+            if (e.KeyCode == Keys.Enter && !e.Shift && !_running) { e.Handled = e.SuppressKeyPress = true; OnSend(); }
         };
 
         var rightCol = new Panel { Dock = DockStyle.Right, Width = 178, BackColor = Theme.RailBack, Padding = new Padding(8, 0, 0, 0) };
@@ -163,7 +163,7 @@ public sealed class AiChatView : UserControl
         var key = CredentialVault.Get("ETTerms/AiApiKey") ?? "";
         _client = new OpenAiChatClient(s.AiBaseUrl, key, s.AiModel);
         _tools = new AiTools { ConfirmAsync = ConfirmOnUiAsync };
-        _agent = new AgentHost(_client, _tools, s.AiSystemPrompt);
+        _agent = new AgentHost(_client, _tools, s.AiSystemPrompt, s.AiMaxToolRounds);
         _agent.AssistantText += t => Ui(() => { HideThinking(); AddAI(t); });
         _agent.ToolActivity += t => Ui(() => AddTool(t));
         _agent.Status += st => Ui(() => { if (st == "thinking") ShowThinking(); });
@@ -216,20 +216,31 @@ public sealed class AiChatView : UserControl
         return tcs.Task;
     }
 
+    private bool _running;
+
     private async void OnSend()
     {
         if (_agent == null) return;
+        if (_running) { _cts?.Cancel(); return; }   // 執行中再按 = 中止（長跑用）
+
         var text = _input.Text.Trim();
         if (text.Length == 0) return;
         _input.Clear();
         AddUser(text);
         ShowThinking();
-        _send.Enabled = false;
+        SetRunning(true);
         _cts = new CancellationTokenSource();
         try { await _agent.SendAsync(text, _cts.Token); }
-        catch (OperationCanceledException) { AddNote("（已取消）"); }
+        catch (OperationCanceledException) { AddNote("（已停止）"); }
         catch (Exception ex) { AddError(ex.Message); }
-        finally { HideThinking(); _send.Enabled = true; }
+        finally { HideThinking(); SetRunning(false); }
+    }
+
+    private void SetRunning(bool running)
+    {
+        _running = running;
+        _send.Text = running ? "■ Stop" : "Send  ⏎";
+        _send.FlatAppearance.BorderColor = running ? Color.FromArgb(210, 120, 120) : Theme.Accent;
     }
 
     // ── WebView2 interop（呼叫 ChatHtml 裡的 JS 函式）──

src/ETTerms/App/SettingsView.cs

@@ -339,8 +339,22 @@ public sealed class SettingsView : UserControl
             PlaceholderText = "(optional) override the assistant persona / system prompt"
         };
 
+        var maxRounds = new NumericUpDown
+        {
+            Width = 100, Minimum = 0, Maximum = 100000, Increment = 10, Value = s.AiMaxToolRounds,
+            BackColor = Theme.TabBack, ForeColor = Theme.Text, BorderStyle = BorderStyle.FixedSingle
+        };
+
         flow.Controls.Add(MakeRow("Base URL (with /v1)", baseUrl));
         flow.Controls.Add(MakeRow("API Key", apiKey));
+        flow.Controls.Add(MakeRow("Max tool calls / message", maxRounds));
+        flow.Controls.Add(new Label
+        {
+            Text = "How many tool calls the assistant may chain per message before it stops (a runaway-loop guard).\n" +
+                   "0 = unlimited — for long automation runs. Every round costs tokens; press Stop in the chat to abort.",
+            AutoSize = false, Width = 620, Height = 34,
+            ForeColor = Theme.TextDim, Font = Theme.UiFont, Margin = new Padding(0, 0, 0, 6)
+        });
         flow.Controls.Add(MakeSpacer(4));
         flow.Controls.Add(new Label
         {
@@ -363,6 +377,7 @@ public sealed class SettingsView : UserControl
         {
             s.AiBaseUrl = baseUrl.Text.Trim();
             s.AiSystemPrompt = sysPrompt.Text.Trim();
+            s.AiMaxToolRounds = (int)maxRounds.Value;
             s.Save();
             var key = apiKey.Text;
             if (string.IsNullOrEmpty(key)) CredentialVault.Delete("ETTerms/AiApiKey");

src/ETTerms/Infrastructure/AppSettings.cs

@@ -39,6 +39,9 @@ public sealed class AppSettings
     public string AiModel { get; set; } = "";
     /// <summary>系統提示詞（人設）；空則用內建預設。</summary>
     public string AiSystemPrompt { get; set; } = "";
+    /// <summary>AI agent 單次訊息的工具呼叫輪數上限（防失控迴圈的保險）。
+    /// **0 = 無上限**（自動化長跑用；注意每輪都燒 token/費用,執行中可按 Stop 中止）。</summary>
+    public int AiMaxToolRounds { get; set; } = 30;
 
     // ── Keyword highlight（終端機關鍵字標色 + 分頁警示；Settings → Highlight 分頁設定）──
     public bool KeywordHighlightEnabled { get; set; } = true;