feat: v0.4.0 performance & stability overhaul

Terminal:
- cache font variants + single reusable brush in render hot path;
  resolve cell colors once per cell; dispose GDI resources
- scrollback: List+RemoveRange -> O(1) ring buffer
- follow new output only when already at bottom (no more yank-to-bottom
  while reading history)
- alt-screen mouse wheel -> arrow keys (vim/htop scroll)
- answer DSR (ESC[5n/6n) and DA (ESC[c) queries so TUIs no longer hang
- remove dead code in OnKeyPress

Encoding correctness (garbled CJK across chunk boundaries):
- stateful UTF-8 Decoder in TTLInterpreter.OnData, SerialBridgeServer
  rx forwarding, and SessionLogger.Write

Sessions:
- ShellChannel: free proc-thread attribute list, close hProcess,
  notify '[ETTerms] shell process exited' in the tab
- SshChannel: surface ErrorOccurred / ShellStream.Closed in the tab;
  Write no longer throws into the UI thread on a dead connection

PDU:
- new shared ETTerms.PduCore project replaces the two drifted copies of
  PduController (GUI + PduMcp); logging via injected delegates
- batched SNMP GET (GetAllPortsStatus): 12-port poll is 3 UDP
  round-trips instead of 36 (StatusView polling + pdu_status tool)

Scripting:
- cap TTL receive buffer at 1MB; skip re-scan in wait when buffer
  length unchanged
- merge ScriptRunner.RunAsync/RunGroupAsync; new TtlScript helper
  dedups script picking + group-command checks (3 copies -> 1)

Misc:
- ConnectionStore: parse LastUsedUtc with InvariantCulture/RoundtripKind
- version 0.4.0; About changelog; CLAUDE.md notes (intentional group
  barrier behavior, SSH.NET reflection resize caveat)

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

src/ETTerms.PduCore/ETTerms.PduCore.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <RootNamespace>ETTerms.PduCore</RootNamespace>
+    <AssemblyName>ETTerms.PduCore</AssemblyName>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="SnmpSharpNet" Version="0.9.7">
+      <NoWarn>NU1701</NoWarn>
+    </PackageReference>
+  </ItemGroup>
+
+</Project>

src/ETTerms.PduCore/PduController.cs

@@ -0,0 +1,124 @@
+using System.Net;
+using SnmpSharpNet;
+
+namespace ETTerms.PduCore;
+
+/// <summary>
+/// PDU controller for iPoMan II/III models via SNMP。
+/// GUI 與 ETTerms.PduMcp 共用的唯一實作（v0.4.0 起取代兩份複製的版本）。
+/// 診斷輸出走建構子注入的 log 委派：GUI 給 AppLogger、MCP server 給 stderr
+/// （stdio MCP 的 stdout 專供 JSON-RPC，不可污染）。
+/// SNMP 走 UDP、非獨佔，多個行程可同時對同一台 PDU 操作。
+/// </summary>
+public sealed class PduController : IDisposable
+{
+    private readonly string _ip;
+    private readonly Action<string>? _logInfo;
+    private readonly Action<string>? _logWarn;
+
+    private const string Community = "private";
+    private const int SnmpPort = 161;
+    private const int Timeout = 3000;
+
+    public string Ip => _ip;
+
+    public PduController(string ip, Action<string>? logInfo = null, Action<string>? logWarn = null)
+    {
+        _ip = ip;
+        _logInfo = logInfo;
+        _logWarn = logWarn;
+    }
+
+    /// <summary>讀 PDU 型號/名稱 OID；非空且含 "PDU" 代表連得上。</summary>
+    public string? GetModelName() => SnmpGet(".1.3.6.1.4.1.2468.1.4.2.1.1.4");
+
+    public bool CheckConnection()
+    {
+        var name = GetModelName();
+        _logInfo?.Invoke($"[PDU] CheckConnection {_ip}: name='{name ?? "<null>"}'");
+        return !string.IsNullOrEmpty(name) && name.Contains("PDU");
+    }
+
+    public bool SetPortOn(int port) => SnmpSet(PortControlOid(port), new Integer32(3));
+    public bool SetPortOff(int port) => SnmpSet(PortControlOid(port), new Integer32(4));
+
+    /// <summary>true = on, false = off, null = unknown/unreachable.</summary>
+    public bool? GetPortState(int port) => ParseState(SnmpGet(PortStateOid(port)));
+
+    public int? GetPortCurrent(int port) => int.TryParse(SnmpGet(PortCurrentOid(port)), out int v) ? v : null;
+    public double? GetPortPowerWatts(int port) => int.TryParse(SnmpGet(PortPowerOid(port)), out int v) ? v / 10.0 : null;
+
+    /// <summary>
+    /// 一次讀回所有插座的狀態 / 電流(mA) / 功率(W)。
+    /// 以 3 個批次 SNMP GET（每個 PDU 含 <paramref name="portCount"/> 個 varbind）取代
+    /// 逐 port 逐 OID 的 3×N 個請求 —— 12 port 從 36 個 UDP 來回縮成 3 個，
+    /// 逾時時的最壞情況也從 36×Timeout 縮到 3×Timeout。
+    /// </summary>
+    public (bool? State, int? CurrentMilliAmps, double? PowerWatts)[] GetAllPortsStatus(int portCount)
+    {
+        var ports = Enumerable.Range(1, portCount).ToArray();
+        var states = SnmpGetMany(ports.Select(PortStateOid).ToArray());
+        var currents = SnmpGetMany(ports.Select(PortCurrentOid).ToArray());
+        var powers = SnmpGetMany(ports.Select(PortPowerOid).ToArray());
+
+        var result = new (bool?, int?, double?)[portCount];
+        for (int i = 0; i < portCount; i++)
+        {
+            result[i] = (
+                ParseState(states[i]),
+                int.TryParse(currents[i], out int c) ? c : null,
+                int.TryParse(powers[i], out int p) ? p / 10.0 : null);
+        }
+        return result;
+    }
+
+    private static bool? ParseState(string? r) => r == "3" ? true : (r == "2" || r == "4") ? false : null;
+
+    private static string PortControlOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.4.1.2.{port}";
+    private static string PortStateOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.2.{port}";
+    private static string PortCurrentOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.3.{port}";
+    private static string PortPowerOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.5.{port}";
+
+    private bool SnmpSet(string oid, AsnType value)
+    {
+        try
+        {
+            var param = new AgentParameters(new OctetString(Community)) { Version = SnmpVersion.Ver1 };
+            using var target = new UdpTarget((IPAddress)new IpAddress(_ip), SnmpPort, Timeout, 1);
+            var pdu = new SnmpSharpNet.Pdu(PduType.Set);
+            pdu.VbList.Add(new Oid(oid), value);
+            var result = (SnmpV1Packet)target.Request(pdu, param);
+            return result?.Pdu.ErrorStatus == 0;
+        }
+        catch (Exception ex) { _logWarn?.Invoke($"[PDU] SNMP SET {oid} exception: {ex.Message}"); return false; }
+    }
+
+    private string? SnmpGet(string oid)
+    {
+        var r = SnmpGetMany(new[] { oid });
+        return r[0];
+    }
+
+    /// <summary>一個 SNMP GET 帶多個 OID（varbind），回傳同序的值；失敗整批回 null。</summary>
+    private string?[] SnmpGetMany(string[] oids)
+    {
+        var result = new string?[oids.Length];
+        try
+        {
+            var param = new AgentParameters(new OctetString(Community)) { Version = SnmpVersion.Ver1 };
+            using var target = new UdpTarget((IPAddress)new IpAddress(_ip), SnmpPort, Timeout, 1);
+            var pdu = new SnmpSharpNet.Pdu(PduType.Get);
+            foreach (var oid in oids) pdu.VbList.Add(new Oid(oid));
+            var resp = (SnmpV1Packet)target.Request(pdu, param);
+            if (resp == null) { _logWarn?.Invoke($"[PDU] SNMP GET ({oids.Length} oids): no response (timeout)"); return result; }
+            if (resp.Pdu.ErrorStatus != 0) { _logWarn?.Invoke($"[PDU] SNMP GET ({oids.Length} oids): ErrorStatus={resp.Pdu.ErrorStatus}"); return result; }
+            // SNMP GET 回應的 varbind 順序與請求一致，直接依 index 對回去。
+            int n = Math.Min(oids.Length, resp.Pdu.VbList.Count);
+            for (int i = 0; i < n; i++) result[i] = resp.Pdu.VbList[i].Value.ToString();
+        }
+        catch (Exception ex) { _logWarn?.Invoke($"[PDU] SNMP GET ({oids.Length} oids) exception: {ex.Message}"); }
+        return result;
+    }
+
+    public void Dispose() { }
+}

src/ETTerms.PduMcp/ETTerms.PduMcp.csproj

@@ -12,9 +12,10 @@
   <ItemGroup>
     <PackageReference Include="ModelContextProtocol" Version="1.2.0" />
     <PackageReference Include="Microsoft.Extensions.Hosting" Version="8.0.1" />
-    <PackageReference Include="SnmpSharpNet" Version="0.9.7">
-      <NoWarn>NU1701</NoWarn>
-    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\ETTerms.PduCore\ETTerms.PduCore.csproj" />
   </ItemGroup>
 
 </Project>

src/ETTerms.PduMcp/PduController.cs

@@ -1,92 +0,0 @@
-using System.Net;
-using SnmpSharpNet;
-
-namespace ETTerms.PduMcp;
-
-/// <summary>
-/// PDU controller for iPoMan II/III models via SNMP (slim copy of the GUI's
-/// ETTerms.Scripting.Pdu.PduController, ported into the standalone MCP server).
-///
-/// Differences from the GUI version:
-///   • No dependency on ETTerms.Infrastructure.AppLogger — diagnostics go to stderr
-///     (stdout is reserved for the MCP JSON-RPC stream).
-///   • Adds <see cref="GetModelName"/> so tools can surface the device identity.
-///
-/// SNMP is connectionless (UDP) and non-exclusive, so this talks to the PDU directly
-/// without bridging through the GUI.
-/// </summary>
-public sealed class PduController : IDisposable
-{
-    private readonly string _ip;
-    private const string Community = "private";
-    private const int SnmpPort = 161;
-    private const int Timeout = 3000;
-
-    public string Ip => _ip;
-
-    public PduController(string ip) => _ip = ip;
-
-    /// <summary>Reads the PDU model/name OID; non-empty containing "PDU" means reachable.</summary>
-    public string? GetModelName() => SnmpGet(".1.3.6.1.4.1.2468.1.4.2.1.1.4");
-
-    public bool CheckConnection()
-    {
-        var name = GetModelName();
-        Log($"CheckConnection {_ip}: name='{name ?? "<null>"}'");
-        return !string.IsNullOrEmpty(name) && name.Contains("PDU");
-    }
-
-    public bool SetPortOn(int port) => SnmpSet(PortControlOid(port), new Integer32(3));
-    public bool SetPortOff(int port) => SnmpSet(PortControlOid(port), new Integer32(4));
-
-    /// <summary>true = on, false = off, null = unknown/unreachable.</summary>
-    public bool? GetPortState(int port)
-    {
-        var r = SnmpGet(PortStateOid(port));
-        return r == "3" ? true : (r == "2" || r == "4") ? false : null;
-    }
-
-    public int? GetPortCurrent(int port) => int.TryParse(SnmpGet(PortCurrentOid(port)), out int v) ? v : null;
-    public double? GetPortPowerWatts(int port) => int.TryParse(SnmpGet(PortPowerOid(port)), out int v) ? v / 10.0 : null;
-
-    private static string PortControlOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.4.1.2.{port}";
-    private static string PortStateOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.2.{port}";
-    private static string PortCurrentOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.3.{port}";
-    private static string PortPowerOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.5.{port}";
-
-    private bool SnmpSet(string oid, AsnType value)
-    {
-        try
-        {
-            var param = new AgentParameters(new OctetString(Community)) { Version = SnmpVersion.Ver1 };
-            using var target = new UdpTarget((IPAddress)new IpAddress(_ip), SnmpPort, Timeout, 1);
-            var pdu = new SnmpSharpNet.Pdu(PduType.Set);
-            pdu.VbList.Add(new Oid(oid), value);
-            var result = (SnmpV1Packet)target.Request(pdu, param);
-            return result?.Pdu.ErrorStatus == 0;
-        }
-        catch (Exception ex) { Log($"SNMP SET {oid} exception: {ex.Message}"); return false; }
-    }
-
-    private string? SnmpGet(string oid)
-    {
-        try
-        {
-            var param = new AgentParameters(new OctetString(Community)) { Version = SnmpVersion.Ver1 };
-            using var target = new UdpTarget((IPAddress)new IpAddress(_ip), SnmpPort, Timeout, 1);
-            var pdu = new SnmpSharpNet.Pdu(PduType.Get);
-            pdu.VbList.Add(new Oid(oid));
-            var result = (SnmpV1Packet)target.Request(pdu, param);
-            if (result == null) { Log($"SNMP GET {oid}: no response (timeout)"); return null; }
-            if (result.Pdu.ErrorStatus != 0) { Log($"SNMP GET {oid}: ErrorStatus={result.Pdu.ErrorStatus}"); return null; }
-            foreach (var v in result.Pdu.VbList) return v.Value.ToString();
-        }
-        catch (Exception ex) { Log($"SNMP GET {oid} exception: {ex.Message}"); }
-        return null;
-    }
-
-    // stdio MCP server：stdout 專供 JSON-RPC，診斷一律走 stderr。
-    private static void Log(string msg) => Console.Error.WriteLine($"[PDU] {msg}");
-
-    public void Dispose() { }
-}

src/ETTerms.PduMcp/PduRegistry.cs

@@ -1,4 +1,5 @@
 using System.Collections.Concurrent;
+using ETTerms.PduCore;
 
 namespace ETTerms.PduMcp;
 
@@ -16,7 +17,10 @@ public sealed class PduRegistry
     private readonly ConcurrentDictionary<string, PduController> _pdus = new(StringComparer.OrdinalIgnoreCase);
 
     public PduController GetOrAdd(string ip) =>
-        _pdus.GetOrAdd(ip.Trim(), static k => new PduController(k));
+        _pdus.GetOrAdd(ip.Trim(), static k => new PduController(k, Log, Log));
+
+    // stdio MCP server：stdout 專供 JSON-RPC，診斷一律走 stderr。
+    private static void Log(string msg) => Console.Error.WriteLine(msg);
 
     public bool TryGet(string ip, out PduController pdu) =>
         _pdus.TryGetValue(ip.Trim(), out pdu!);

src/ETTerms.PduMcp/PduTools.cs

@@ -1,6 +1,7 @@
 using System.ComponentModel;
 using System.Text;
 using System.Text.Json;
+using ETTerms.PduCore;
 using ModelContextProtocol.Server;
 
 namespace ETTerms.PduMcp;
@@ -65,9 +66,20 @@ public static class PduTools
     {
         if (!PduRegistry.Instance.TryGet(ip, out var pdu))
             return Err($"PDU {ip} not connected. Call pdu_connect first.");
+        // 批次 SNMP GET：12 port 只需 3 個 UDP 來回，而非逐 port 逐 OID 36 個。
+        var all = pdu.GetAllPortsStatus(PduRegistry.PortCount);
         var ports = new List<object>();
-        for (int p = 1; p <= PduRegistry.PortCount; p++)
-            ports.Add(PortSnapshot(pdu, p));
+        for (int p = 0; p < all.Length; p++)
+        {
+            var (state, current, power) = all[p];
+            ports.Add(new
+            {
+                port = p + 1,
+                state = state == true ? "on" : state == false ? "off" : "unknown",
+                currentMilliAmps = current,
+                powerWatts = power
+            });
+        }
         return Ok(new { ip, ports });
     }
 

src/ETTerms/App/AboutView.cs

@@ -183,6 +183,17 @@ public sealed class AboutView : UserControl
 
     private static readonly ChangelogEntry[] Changelog =
     [
+        new("0.4.0", new DateOnly(2026, 7, 2), "Performance & stability overhaul",
+        [
+            "The terminal is much smoother during heavy output (long boot logs, big file dumps) — drawing and scroll history were reworked to stay fast no matter how much text has scrolled by.",
+            "Fixed Chinese and other non-English text occasionally turning into garbled characters — in script 'wait' matching, in what the AI reads from the serial port, and in saved session logs.",
+            "While you are scrolled back reading history, new output no longer yanks the view down to the bottom.",
+            "The mouse wheel now scrolls inside full-screen tools like vim and htop instead of doing nothing.",
+            "Full-screen tools that ask the terminal where the cursor is now get an answer, fixing apps that could hang or draw at the wrong position.",
+            "You now see a clear message in the tab when an SSH connection drops or the local shell exits, instead of the session silently going dead.",
+            "PDU status refresh is much faster and lighter on the network (one bundled query instead of 36 separate ones).",
+            "Fixed small memory and handle leaks when opening many local shell tabs over a long session.",
+        ]),
         new("0.3.3", new DateOnly(2026, 6, 16), "Bugfix — terminal input no longer dies after activity",
         [
             "Fixed: after the terminal had printed output (Serial or PowerShell), switching away and back — minimizing, or clicking another window — left the terminal unable to accept any typing or Enter, forcing you to reopen the session.",

src/ETTerms/App/StatusView.cs

@@ -1,6 +1,7 @@
 using System.Drawing;
 using System.Windows.Forms;
-using ETTerms.Scripting.Pdu;
+using ETTerms.Infrastructure;
+using ETTerms.PduCore;
 
 namespace ETTerms.App;
 
@@ -149,12 +150,9 @@ public sealed class StatusView : UserControl
 
             try
             {
-                var rows = new (bool? state, int? current, double? power)[12];
-                for (int i = 0; i < 12; i++)
-                {
-                    int port = i + 1;
-                    rows[i] = (current.GetPortState(port), current.GetPortCurrent(port), current.GetPortPowerWatts(port));
-                }
+                // 批次 SNMP GET：12 port 只需 3 個 UDP 來回（原本逐 port 逐 OID 36 個，
+                // 逾時時最壞一輪要 36×3 秒）。
+                var rows = current.GetAllPortsStatus(12);
 
                 if (!IsDisposed && IsHandleCreated)
                 {
@@ -192,7 +190,7 @@ public sealed class StatusView : UserControl
             }
 
             var ip = ipBox.Text.Trim();
-            var p = new PduController(ip);
+            var p = new PduController(ip, AppLogger.Info, AppLogger.LogWarning);
             if (p.CheckConnection())
             {
                 pdu = p;
@@ -255,7 +253,7 @@ public sealed class StatusView : UserControl
         return page;
     }
 
-    private static void ApplyPduRows(DataGridView grid, (bool? state, int? current, double? power)[] rows)
+    private static void ApplyPduRows(DataGridView grid, (bool? State, int? CurrentMilliAmps, double? PowerWatts)[] rows)
     {
         for (int i = 0; i < rows.Length && i < grid.Rows.Count; i++)
         {

src/ETTerms/App/Workspace/WorkspaceView.cs

@@ -452,22 +452,9 @@ public sealed class WorkspaceView : UserControl
             return;
         }
 
-        string content, name;
-        using (var dlg = new OpenFileDialog { Filter = "TTL scripts (*.ttl)|*.ttl|All files (*.*)|*.*" })
-        {
-            if (dlg.ShowDialog(this) != DialogResult.OK) return;
-            content = File.ReadAllText(dlg.FileName);
-            name = Path.GetFileName(dlg.FileName);
-        }
-
+        if (!TtlScript.TryPick(this, out var content, out var name)) return;
         // Run All 拒絕含 waitall / sendlnall 的腳本
-        if (ScriptContainsGroupCommands(content))
-        {
-            MessageBox.Show(this,
-                "Script contains 'waitall' or 'sendlnall' which require Group execution.\nPlease use Run Group buttons instead.",
-                "Run All", MessageBoxButtons.OK, MessageBoxIcon.Warning);
-            return;
-        }
+        if (TtlScript.WarnIfGroupCommands(this, content, "Run All")) return;
 
         await Task.WhenAll(serials.Select(sp => sp.RunScriptAsync(content, name)));
     }
@@ -486,29 +473,12 @@ public sealed class WorkspaceView : UserControl
             return;
         }
 
-        string content, name;
-        using (var dlg = new OpenFileDialog { Filter = "TTL scripts (*.ttl)|*.ttl|All files (*.*)|*.*" })
-        {
-            if (dlg.ShowDialog(this) != DialogResult.OK) return;
-            content = File.ReadAllText(dlg.FileName);
-            name = Path.GetFileName(dlg.FileName);
-        }
+        if (!TtlScript.TryPick(this, out var content, out var name)) return;
 
         var sync = new GroupSyncContext(members.Count);
         await Task.WhenAll(members.Select((sp, i) => sp.RunGroupScriptAsync(content, name, sync, ((char)('A' + i)).ToString())));
     }
 
-    private static bool ScriptContainsGroupCommands(string content)
-    {
-        foreach (var line in content.Split('\n'))
-        {
-            var t = line.Trim().ToLower();
-            if (t.StartsWith("waitall") || t.StartsWith("sendlnall") || t.StartsWith("sendlngroup"))
-                return true;
-        }
-        return false;
-    }
-
     protected override void Dispose(bool disposing)
     {
         if (disposing)

src/ETTerms/Connections/ConnectionStore.cs

@@ -1,3 +1,4 @@
+using System.Globalization;
 using System.Text.Json;
 using Microsoft.Data.Sqlite;
 using ETTerms.Infrastructure;
@@ -59,7 +60,8 @@ public sealed class ConnectionStore
                 Type = (ConnectionType)r.GetInt32(2),
                 SortOrder = r.GetInt32(3),
                 GroupName = r.IsDBNull(4) ? null : r.GetString(4),
-                LastUsedUtc = DateTime.Parse(r.GetString(5)),
+                // 與寫入端的 "o" (round-trip) 格式對稱，不受系統地區設定影響
+                LastUsedUtc = DateTime.Parse(r.GetString(5), CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind),
                 Ssh = blob?.Ssh,
                 Serial = blob?.Serial
             });

src/ETTerms/ETTerms.csproj

@@ -10,7 +10,7 @@
     <AssemblyName>ETTerms</AssemblyName>
 
     <!-- 版本資訊 -->
-    <Version>0.3.3</Version>
+    <Version>0.4.0</Version>
     <Product>ETTerms</Product>
     <Company>ETTerms Project</Company>
 
@@ -28,13 +28,15 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.Data.Sqlite" Version="8.0.10" />
-    <PackageReference Include="SnmpSharpNet" Version="0.9.7">
-      <NoWarn>NU1701</NoWarn>
-    </PackageReference>
     <PackageReference Include="SSH.NET" Version="2024.2.0" />
     <PackageReference Include="System.IO.Ports" Version="8.0.0" />
   </ItemGroup>
 
+  <ItemGroup>
+    <!-- PDU SNMP 控制共用庫（GUI 與 ETTerms.PduMcp 共用，v0.4.0 取代兩份複製的 PduController） -->
+    <ProjectReference Include="..\ETTerms.PduCore\ETTerms.PduCore.csproj" />
+  </ItemGroup>
+
   <!--
     發佈 GUI 時，自動把 MCP servers（Serial + PDU）一併發佈到 <publish>\<server>\ 子資料夾。
     這樣單一 `dotnet publish src\ETTerms` 就會產生完整自洽的 bundle，

src/ETTerms/Infrastructure/SessionLogger.cs

@@ -23,6 +23,7 @@ public sealed class SessionLogger : IDisposable
     private readonly object _lock = new();
     private readonly StreamWriter _writer;
     private readonly StringBuilder _pending = new();
+    private readonly Decoder _decoder = Encoding.UTF8.GetDecoder();   // stateful：多位元組字元跨 chunk 不會解成亂碼
     private bool _disposed;
 
     /// <summary>實際寫入的完整檔案路徑。</summary>
@@ -52,13 +53,15 @@ public sealed class SessionLogger : IDisposable
     public void Write(byte[] data)
     {
         if (_disposed || data.Length == 0) return;
-        string text = Encoding.UTF8.GetString(data);
-        string clean = AnsiRegex.Replace(text, "").Replace("\r", "");
-        if (clean.Length == 0) return;
 
         lock (_lock)
         {
             if (_disposed) return;
+            var chars = new char[data.Length];
+            int n = _decoder.GetChars(data, 0, data.Length, chars, 0);
+            if (n == 0) return;
+            string clean = AnsiRegex.Replace(new string(chars, 0, n), "").Replace("\r", "");
+            if (clean.Length == 0) return;
             string stamp = $"[{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff}] ";
             int start = 0;
             for (int i = 0; i < clean.Length; i++)

src/ETTerms/Scripting/Pdu/PduController.cs

@@ -1,76 +0,0 @@
-using System.Net;
-using ETTerms.Infrastructure;
-using SnmpSharpNet;
-
-namespace ETTerms.Scripting.Pdu;
-
-/// <summary>
-/// PDU Controller for iPoMan II/III models via SNMP.
-/// Ported from MyTeraTerm's PDUControlLib.
-/// </summary>
-public sealed class PduController : IDisposable
-{
-    private readonly string _ip;
-    private const string Community = "private";
-    private const int SnmpPort = 161;
-    private const int Timeout = 3000;
-
-    public PduController(string ip) => _ip = ip;
-
-    public bool CheckConnection()
-    {
-        var name = SnmpGet(".1.3.6.1.4.1.2468.1.4.2.1.1.4");
-        AppLogger.Info($"[PDU] CheckConnection {_ip}: name='{name ?? "<null>"}'");
-        return !string.IsNullOrEmpty(name) && name.Contains("PDU");
-    }
-
-    public bool SetPortOn(int port) => SnmpSet(PortControlOid(port), new Integer32(3));
-    public bool SetPortOff(int port) => SnmpSet(PortControlOid(port), new Integer32(4));
-
-    public bool? GetPortState(int port)
-    {
-        var r = SnmpGet(PortStateOid(port));
-        return r == "3" ? true : (r == "2" || r == "4") ? false : null;
-    }
-
-    public int? GetPortCurrent(int port) => int.TryParse(SnmpGet(PortCurrentOid(port)), out int v) ? v : null;
-    public double? GetPortPowerWatts(int port) => int.TryParse(SnmpGet(PortPowerOid(port)), out int v) ? v / 10.0 : null;
-
-    private static string PortControlOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.4.1.2.{port}";
-    private static string PortStateOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.2.{port}";
-    private static string PortCurrentOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.3.{port}";
-    private static string PortPowerOid(int port) => $".1.3.6.1.4.1.2468.1.4.2.1.3.2.3.1.5.{port}";
-
-    private bool SnmpSet(string oid, AsnType value)
-    {
-        try
-        {
-            var param = new AgentParameters(new OctetString(Community)) { Version = SnmpVersion.Ver1 };
-            using var target = new UdpTarget((IPAddress)new IpAddress(_ip), SnmpPort, Timeout, 1);
-            var pdu = new SnmpSharpNet.Pdu(PduType.Set);
-            pdu.VbList.Add(new Oid(oid), value);
-            var result = (SnmpV1Packet)target.Request(pdu, param);
-            return result?.Pdu.ErrorStatus == 0;
-        }
-        catch { return false; }
-    }
-
-    private string? SnmpGet(string oid)
-    {
-        try
-        {
-            var param = new AgentParameters(new OctetString(Community)) { Version = SnmpVersion.Ver1 };
-            using var target = new UdpTarget((IPAddress)new IpAddress(_ip), SnmpPort, Timeout, 1);
-            var pdu = new SnmpSharpNet.Pdu(PduType.Get);
-            pdu.VbList.Add(new Oid(oid));
-            var result = (SnmpV1Packet)target.Request(pdu, param);
-            if (result == null) { AppLogger.LogWarning($"[PDU] SNMP GET {oid}: no response (timeout)"); return null; }
-            if (result.Pdu.ErrorStatus != 0) { AppLogger.LogWarning($"[PDU] SNMP GET {oid}: ErrorStatus={result.Pdu.ErrorStatus}"); return null; }
-            foreach (var v in result.Pdu.VbList) return v.Value.ToString();
-        }
-        catch (Exception ex) { AppLogger.LogError($"[PDU] SNMP GET {oid} exception", ex); }
-        return null;
-    }
-
-    public void Dispose() { }
-}

src/ETTerms/Scripting/ScriptRunner.cs

@@ -22,39 +22,14 @@ public sealed class ScriptRunner
 
     public bool IsRunning { get; private set; }
 
-    public async Task RunAsync(string content, string fileName, ISessionChannel channel)
-    {
-        if (IsRunning) return;
-        IsRunning = true;
+    public Task RunAsync(string content, string fileName, ISessionChannel channel)
+        => RunCoreAsync(content, fileName, channel, null, "");
 
-        var interp = new TTLInterpreter(channel);
-        interp.StatusChanged += (f, l, c) => StatusChanged?.Invoke(f, l, c);
-        interp.Output += m => Output?.Invoke(m);
-        _interp = interp;
+    public Task RunGroupAsync(string content, string fileName, ISessionChannel channel, GroupSyncContext sync, string memberLabel = "")
+        => RunCoreAsync(content, fileName, channel, sync, memberLabel);
 
-        try
-        {
-            await Task.Run(() => interp.ExecuteScriptContent(content, fileName));
-            Finished?.Invoke(true, "Completed");
-        }
-        catch (OperationCanceledException)
-        {
-            Finished?.Invoke(false, "Cancelled");
-        }
-        catch (Exception ex)
-        {
-            Output?.Invoke($"[error] {ex.Message}");
-            Finished?.Invoke(false, ex.Message);
-        }
-        finally
-        {
-            interp.Dispose();
-            _interp = null;
-            IsRunning = false;
-        }
-    }
-
-    public async Task RunGroupAsync(string content, string fileName, ISessionChannel channel, GroupSyncContext sync, string memberLabel = "")
+    private async Task RunCoreAsync(string content, string fileName, ISessionChannel channel,
+        GroupSyncContext? sync, string memberLabel)
     {
         if (IsRunning) return;
         IsRunning = true;

src/ETTerms/Scripting/TTLInterpreter.cs

@@ -1,7 +1,8 @@
 using System.Globalization;
 using System.Text;
 using System.Text.RegularExpressions;
-using ETTerms.Scripting.Pdu;
+using ETTerms.Infrastructure;
+using ETTerms.PduCore;
 using ETTerms.Sessions;
 
 namespace ETTerms.Scripting;
@@ -17,11 +18,13 @@ public sealed class TTLInterpreter : IDisposable
 {
     private readonly ISessionChannel _channel;
     private readonly Encoding _enc = new UTF8Encoding(false);
+    private readonly Decoder _rxDecoder = Encoding.UTF8.GetDecoder();   // stateful：多位元組字元跨 chunk 不會解成亂碼
     private readonly Dictionary<string, object> _vars = new();
     private readonly StringBuilder _recv = new();
     private readonly CancellationTokenSource _cts = new();
 
     private const int SettleMs = 300;   // wait 命中關鍵字後，需連續安靜這麼久（無新資料）才接受，避免比對到輸出中途的回顯
+    private const int MaxRecvChars = 1_000_000;   // _recv 上限：長時間無 wait 消費時避免無限成長
 
     private GroupSyncContext? _groupSync;
     private string _groupMemberLabel = "";
@@ -51,7 +54,13 @@ public sealed class TTLInterpreter : IDisposable
 
     private void OnData(byte[] data)
     {
-        lock (_recv) _recv.Append(_enc.GetString(data));
+        lock (_recv)
+        {
+            var chars = new char[data.Length];
+            int n = _rxDecoder.GetChars(data, 0, data.Length, chars, 0);
+            _recv.Append(chars, 0, n);
+            if (_recv.Length > MaxRecvChars) _recv.Remove(0, _recv.Length - MaxRecvChars);
+        }
     }
 
     #region Script Execution
@@ -350,11 +359,19 @@ public sealed class TTLInterpreter : IDisposable
         _logWriter?.WriteLine($"[Wait] {text}");
 
         int elapsed = 0;
+        int lastLen = -1;   // buffer 長度沒變就不重掃（避免每 100ms 全量 ToString+IndexOf）
         while (true)
         {
             ThrowIfCancelled();
-            bool found;
-            lock (_recv) found = _recv.ToString().IndexOf(text, StringComparison.Ordinal) >= 0;
+            bool found = false;
+            lock (_recv)
+            {
+                if (_recv.Length != lastLen)
+                {
+                    lastLen = _recv.Length;
+                    found = _recv.ToString().IndexOf(text, StringComparison.Ordinal) >= 0;
+                }
+            }
             if (found && SettleAndConsume(text)) return;
 
             // 只有在明確設定 timeout(>0) 且超時才中止腳本；否則一直等到關鍵字出現或被取消。
@@ -503,7 +520,7 @@ public sealed class TTLInterpreter : IDisposable
         if (parts.Length != 2) { Output?.Invoke("[pduconnect] syntax: pduconnect <device> <ip>"); _result = 0; return; }
         int device = ParseIntDirect(parts[0]);
         string ip = parts[1].Trim('\'', '"');
-        var pdu = new PduController(ip);
+        var pdu = new PduController(ip, AppLogger.Info, AppLogger.LogWarning);
         if (pdu.CheckConnection())
         {
             _pdus[device] = pdu;

src/ETTerms/Scripting/TtlScript.cs

@@ -0,0 +1,44 @@
+using System.Windows.Forms;
+
+namespace ETTerms.Scripting;
+
+/// <summary>
+/// TTL 腳本檔的共用小工具：選檔載入與 group 指令檢查。
+/// SessionPage（▶ Script）與 WorkspaceView（Run All / Run Group）共用，避免三份重複流程。
+/// </summary>
+public static class TtlScript
+{
+    /// <summary>跳出選檔對話框並讀入腳本內容。使用者取消回傳 false。</summary>
+    public static bool TryPick(IWin32Window owner, out string content, out string fileName)
+    {
+        content = "";
+        fileName = "";
+        using var dlg = new OpenFileDialog { Filter = "TTL scripts (*.ttl)|*.ttl|All files (*.*)|*.*" };
+        if (dlg.ShowDialog(owner) != DialogResult.OK) return false;
+        content = File.ReadAllText(dlg.FileName);
+        fileName = Path.GetFileName(dlg.FileName);
+        return true;
+    }
+
+    /// <summary>腳本是否含只能在 Run Group 模式使用的同步指令（waitall / sendlnall / sendlngroup）。</summary>
+    public static bool ContainsGroupCommands(string content)
+    {
+        foreach (var line in content.Split('\n'))
+        {
+            var t = line.Trim().ToLower();
+            if (t.StartsWith("waitall") || t.StartsWith("sendlnall") || t.StartsWith("sendlngroup"))
+                return true;
+        }
+        return false;
+    }
+
+    /// <summary>含 group 指令時警告並回傳 true（呼叫端應中止，改用 Run Group）。</summary>
+    public static bool WarnIfGroupCommands(IWin32Window owner, string content, string caption)
+    {
+        if (!ContainsGroupCommands(content)) return false;
+        MessageBox.Show(owner,
+            "Script contains 'waitall' or 'sendlnall' which require Group execution.\nPlease use Run Group buttons instead.",
+            caption, MessageBoxButtons.OK, MessageBoxIcon.Warning);
+        return true;
+    }
+}

src/ETTerms/Sessions/SerialBridgeServer.cs

@@ -69,13 +69,28 @@ public sealed class SerialBridgeServer : IDisposable
                             Send(new { sessions = SerialBridge.All.Select(e => new { name = e.Name, baud = e.BaudRate }) });
                             break;
                         case "attach":
+                        {
                             Detach();
                             attached = SerialBridge.Find(req.session ?? "");
                             if (attached == null) { Send(new { ok = false, error = $"no open serial session '{req.session}' in GUI" }); break; }
-                            rx = data => Send(new { op = "rx", data = Encoding.UTF8.GetString(data) });
+                            // stateful Decoder：UTF-8 多位元組字元跨 chunk 邊界時不會解成亂碼
+                            var dec = Encoding.UTF8.GetDecoder();
+                            var decLock = new object();
+                            rx = data =>
+                            {
+                                string s;
+                                lock (decLock)
+                                {
+                                    var chars = new char[data.Length];
+                                    int n = dec.GetChars(data, 0, data.Length, chars, 0);
+                                    s = new string(chars, 0, n);
+                                }
+                                if (s.Length > 0) Send(new { op = "rx", data = s });
+                            };
                             attached.Rx += rx;
                             Send(new { ok = true, name = attached.Name });
                             break;
+                        }
                         case "write":
                             if (attached == null) { Send(new { ok = false, error = "not attached" }); break; }
                             attached.Write(req.data ?? "", req.newline);

src/ETTerms/Sessions/SessionPage.cs

@@ -100,20 +100,8 @@ public sealed class SessionPage : UserControl
 
     private async void OnRunScript(object? sender, EventArgs e)
     {
-        string content, name;
-        using (var dlg = new OpenFileDialog { Filter = "TTL scripts (*.ttl)|*.ttl|All files (*.*)|*.*" })
-        {
-            if (dlg.ShowDialog(this) != DialogResult.OK) return;
-            content = File.ReadAllText(dlg.FileName);
-            name = Path.GetFileName(dlg.FileName);
-        }
-        if (ContainsGroupCommands(content))
-        {
-            MessageBox.Show(this,
-                "Script contains 'waitall' or 'sendlnall' which require Group execution.\nPlease use Run Group buttons instead.",
-                "Script", MessageBoxButtons.OK, MessageBoxIcon.Warning);
-            return;
-        }
+        if (!TtlScript.TryPick(this, out var content, out var name)) return;
+        if (TtlScript.WarnIfGroupCommands(this, content, "Script")) return;
         SetRunning(true);
         await _runner.RunAsync(content, name, _channel);
     }
@@ -168,17 +156,6 @@ public sealed class SessionPage : UserControl
         _log.FlatAppearance.BorderColor = on ? Theme.SerialColor : Theme.Border;
     }
 
-    private static bool ContainsGroupCommands(string content)
-    {
-        foreach (var line in content.Split('\n'))
-        {
-            var t = line.Trim().ToLower();
-            if (t.StartsWith("waitall") || t.StartsWith("sendlnall") || t.StartsWith("sendlngroup"))
-                return true;
-        }
-        return false;
-    }
-
     private void SetRunning(bool running)
     {
         _run.Enabled = !running;

src/ETTerms/Sessions/ShellChannel.cs

@@ -73,13 +73,25 @@ public sealed class ShellChannel : ISessionChannel
             ? configured
             : Environment.GetFolderPath(Environment.SpecialFolder.UserProfile);
 
-        bool ok = CreateProcess(null, $"{exe} {args}".TrimEnd(), IntPtr.Zero, IntPtr.Zero, false,
-            0x00080000 /* EXTENDED_STARTUPINFO_PRESENT */, IntPtr.Zero, workDir, ref si, out var pi);
+        bool ok;
+        PROCESS_INFORMATION pi;
+        try
+        {
+            ok = CreateProcess(null, $"{exe} {args}".TrimEnd(), IntPtr.Zero, IntPtr.Zero, false,
+                0x00080000 /* EXTENDED_STARTUPINFO_PRESENT */, IntPtr.Zero, workDir, ref si, out pi);
+        }
+        finally
+        {
+            // attribute list 在 CreateProcess 返回後即可釋放（文件保證），不釋放會每開一個 shell 漏一次
+            DeleteProcThreadAttributeList(si.lpAttributeList);
+            Marshal.FreeHGlobal(si.lpAttributeList);
+        }
 
         if (!ok) throw new Exception($"CreateProcess failed: {Marshal.GetLastWin32Error()}");
 
         CloseHandle(pi.hThread);
         _proc = Process.GetProcessById(pi.dwProcessId);
+        CloseHandle(pi.hProcess);   // 之後都經由 _proc 操作，raw handle 不留（避免 handle 洩漏）
 
         // Start reader thread
         _reader = new Thread(ReadLoop) { IsBackground = true, Name = "ConPTY-Reader" };
@@ -101,7 +113,12 @@ public sealed class ShellChannel : ISessionChannel
                 DataReceived?.Invoke(data);
             }
         }
-        catch when (_closed) { }
+        catch { /* 使用者關閉或 ConPTY 收掉都會走到這，不可讓例外殺掉行程 */ }
+
+        // shell 自己 exit（非使用者關分頁）時給個明確提示，分頁才不會看起來像死掉
+        if (!_closed)
+            DataReceived?.Invoke(Encoding.UTF8.GetBytes(
+                "\r\n\x1b[90m[ETTerms] shell process exited\x1b[0m\r\n"));
     }
 
     public void Write(byte[] data)
@@ -176,6 +193,9 @@ public sealed class ShellChannel : ISessionChannel
     [DllImport("kernel32.dll", SetLastError = true)]
     private static extern bool UpdateProcThreadAttribute(IntPtr lpAttributeList, uint dwFlags, IntPtr Attribute, IntPtr lpValue, IntPtr cbSize, IntPtr lpPreviousValue, IntPtr lpReturnSize);
 
+    [DllImport("kernel32.dll")]
+    private static extern void DeleteProcThreadAttributeList(IntPtr lpAttributeList);
+
     [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
     private static extern bool CreateProcess(string? lpApplicationName, string lpCommandLine, IntPtr lpProcessAttributes, IntPtr lpThreadAttributes, bool bInheritHandles, uint dwCreationFlags, IntPtr lpEnvironment, string lpCurrentDirectory, ref STARTUPINFOEX lpStartupInfo, out PROCESS_INFORMATION lpProcessInformation);
 

src/ETTerms/Sessions/SshChannel.cs

@@ -40,9 +40,22 @@ public sealed class SshChannel : ISessionChannel
             var ci = BuildConnectionInfo();
             _client = new SshClient(ci);
             _client.HostKeyReceived += OnHostKey;
+            // 斷線 / 錯誤要讓使用者看得到，否則只會覺得「打字沒反應」
+            _client.ErrorOccurred += (_, e) =>
+            {
+                if (_closed) return;
+                Emit($"\r\n\x1b[90m[SSH error] {e.Exception.Message}\x1b[0m\r\n");
+                AppLogger.LogWarning($"SSH error {_ssh.Host}: {e.Exception.Message}");
+            };
             _client.Connect();
             _shell = _client.CreateShellStream("xterm-256color", (uint)_cols, (uint)_rows, 0, 0, 4096);
             _shell.DataReceived += (_, e) => DataReceived?.Invoke(e.Data);
+            _shell.Closed += (_, _) =>
+            {
+                if (_closed) return;
+                Emit("\r\n\x1b[90m[SSH] connection closed by remote host\x1b[0m\r\n");
+                AppLogger.Info($"SSH shell closed: {_ssh.Host}");
+            };
             AppLogger.Info($"SSH connected: {_ssh.Username}@{_ssh.Host}:{_ssh.Port}");
         }
         catch (Exception ex)
@@ -102,8 +115,15 @@ public sealed class SshChannel : ISessionChannel
     public void Write(byte[] data)
     {
         if (_shell == null) return;
-        _shell.Write(data, 0, data.Length);
-        _shell.Flush();
+        try
+        {
+            _shell.Write(data, 0, data.Length);
+            _shell.Flush();
+        }
+        catch (Exception ex)   // 連線已斷時從 UI thread 寫入不可讓例外炸掉視窗
+        {
+            if (!_closed) Emit($"\r\n\x1b[90m[SSH] write failed: {ex.Message}\x1b[0m\r\n");
+        }
     }
 
     public void Resize(int cols, int rows)

src/ETTerms/Terminal/AnsiParser.cs

@@ -23,6 +23,10 @@ public sealed class AnsiParser
     /// 讓 PSReadLine / Kiro CLI 等把多行貼上視為單一輸入而非逐行立即送出。</summary>
     public bool BracketedPaste { get; private set; }
 
+    /// <summary>對查詢序列（DSR ESC[5n/6n、DA ESC[c）的回覆，須回送給遠端。
+    /// vim 等 TUI 會查游標位置，收不到回覆可能卡住或排版錯亂。</summary>
+    public event Action<byte[]>? Response;
+
     public AnsiParser(ScreenBuffer buffer) => _b = buffer;
 
     public void Feed(byte[] data)
@@ -130,9 +134,20 @@ public sealed class AnsiParser
             case 'h': SetMode(p, true); break;
             case 'l': SetMode(p, false); break;
             case 'm': Sgr(p); break;
+            case 'n': if (!_priv) DeviceStatusReport(p); break;
+            case 'c': if (!_priv) Respond("\x1b[?1;2c"); break;   // DA：VT100 with AVO
         }
     }
 
+    private void DeviceStatusReport(int[] p)
+    {
+        int code = p.Length > 0 ? p[0] : 0;
+        if (code == 5) Respond("\x1b[0n");                                          // 裝置 OK
+        else if (code == 6) Respond($"\x1b[{_b.CursorRow + 1};{_b.CursorCol + 1}R"); // 游標位置（1-based）
+    }
+
+    private void Respond(string seq) => Response?.Invoke(Encoding.ASCII.GetBytes(seq));
+
     private void SetMode(int[] p, bool set)
     {
         if (!_priv) return;

src/ETTerms/Terminal/ScreenBuffer.cs

@@ -33,8 +33,11 @@ public sealed class ScreenBuffer
     public bool AutoWrap = true;
 
     private Cell[][] _screen;
-    private readonly List<Cell[]> _scrollback = new();
-    private readonly int _maxScroll;
+    // scrollback 用環形緩衝：滿了以後 push/丟舊行都是 O(1)。
+    // （原本 List + RemoveRange(0,…) 在 buffer 滿時每推一行就整串搬移，大量輸出會愈跑愈卡。）
+    private readonly Cell[]?[] _sb;
+    private int _sbHead;                 // 最舊一行的位置
+    private int _sbCount;
     private int _top, _bottom;           // 滾動區（含）
     private bool _wrapPending;
 
@@ -49,15 +52,15 @@ public sealed class ScreenBuffer
     {
         Cols = Math.Max(1, cols); Rows = Math.Max(1, rows);
         DefaultFg = fg; DefaultBg = bg; PenFg = fg; PenBg = bg;
-        _maxScroll = maxScrollback;
+        _sb = new Cell[Math.Max(0, maxScrollback)][];
         _screen = NewGrid(Rows, Cols);
         _top = 0; _bottom = Rows - 1;
     }
 
     // ── 給 TerminalView 讀取 ─────────────────────────────────
-    public int ScrollbackCount => _scrollback.Count;
-    public int TotalRows => _scrollback.Count + Rows;
-    public Cell[] LineAt(int abs) => abs < _scrollback.Count ? _scrollback[abs] : _screen[abs - _scrollback.Count];
+    public int ScrollbackCount => _sbCount;
+    public int TotalRows => _sbCount + Rows;
+    public Cell[] LineAt(int abs) => abs < _sbCount ? _sb[(_sbHead + abs) % _sb.Length]! : _screen[abs - _sbCount];
 
     // ── 內部建構工具 ─────────────────────────────────────────
     private Cell BlankPen() => new() { Ch = ' ', Fg = PenFg, Bg = PenBg, Attr = CellAttr.None };
@@ -73,8 +76,9 @@ public sealed class ScreenBuffer
 
     private void PushScroll(Cell[] line)
     {
-        _scrollback.Add(line);
-        if (_scrollback.Count > _maxScroll) _scrollback.RemoveRange(0, _scrollback.Count - _maxScroll);
+        if (_sb.Length == 0) return;
+        if (_sbCount < _sb.Length) _sb[(_sbHead + _sbCount++) % _sb.Length] = line;
+        else { _sb[_sbHead] = line; _sbHead = (_sbHead + 1) % _sb.Length; }   // 滿了：覆蓋最舊一行
     }
 
     // ── 輸出字元 ─────────────────────────────────────────────
@@ -229,7 +233,7 @@ public sealed class ScreenBuffer
 
     public void EraseInDisplay(int mode)
     {
-        if (mode == 3) { _scrollback.Clear(); return; }
+        if (mode == 3) { Array.Clear(_sb); _sbHead = 0; _sbCount = 0; return; }
         if (mode == 2) { for (int r = 0; r < Rows; r++) _screen[r] = BlankLine(); return; }
         if (mode == 0)
         {

src/ETTerms/Terminal/TerminalInput.cs

@@ -45,4 +45,17 @@ public static class TerminalInput
         };
         return seq is null ? null : Encoding.ASCII.GetBytes(seq);
     }
+
+    /// <summary>滾輪 → 上/下方向鍵序列（alt screen 用，每格 3 行）。notches 正值往上。</summary>
+    public static byte[]? WheelArrows(int notches, bool appCursor)
+    {
+        if (notches == 0) return null;
+        string one = notches > 0
+            ? (appCursor ? "\x1bOA" : "\x1b[A")
+            : (appCursor ? "\x1bOB" : "\x1b[B");
+        int count = Math.Abs(notches) * 3;
+        var sb = new StringBuilder(one.Length * count);
+        for (int i = 0; i < count; i++) sb.Append(one);
+        return Encoding.ASCII.GetBytes(sb.ToString());
+    }
 }

src/ETTerms/Terminal/TerminalView.cs

@@ -17,6 +17,11 @@ public sealed class TerminalView : UserControl
     private readonly ScreenBuffer _buf;
     private readonly AnsiParser _parser;
     private readonly Font _font;
+    // 繪製熱路徑的快取：Font 建立是貴的 GDI 操作，預先做好 4 種變體；
+    // SolidBrush 的 Color 可改，用單一 brush 重複填色，避免每段 run 都 new/dispose。
+    private readonly Font _fontBold, _fontUnderline, _fontBoldUnderline;
+    private readonly SolidBrush _fill = new(Color.Black);
+    private readonly StringBuilder _runSb = new();
     private readonly DarkScrollBar _vscroll;     // 右側深色垂直捲軸（可拖曳捲動 scrollback）
     private bool _suppressScroll;                // 程式設定捲軸值時抑制回呼
     private int _cellW, _cellH;
@@ -35,6 +40,9 @@ public sealed class TerminalView : UserControl
         BackColor = Color.FromArgb(18, 18, 22);
         ImeMode = ImeMode.NoControl;   // 容器控制項預設關 IME，這裡明確開啟讓使用者可切中文
         _font = new Font(profile.FontFamily, profile.FontSize);
+        _fontBold = new Font(_font, FontStyle.Bold);
+        _fontUnderline = new Font(_font, FontStyle.Underline);
+        _fontBoldUnderline = new Font(_font, FontStyle.Bold | FontStyle.Underline);
         using (var g = CreateGraphics())
         {
             var sz = TextRenderer.MeasureText(g, "W", _font, Size.Empty, TextFormatFlags.NoPadding);
@@ -44,6 +52,7 @@ public sealed class TerminalView : UserControl
         _buf = new ScreenBuffer(profile.Cols, profile.Rows,
             Color.FromArgb(220, 220, 220), BackColor, profile.ScrollbackLines);
         _parser = new AnsiParser(_buf);
+        _parser.Response += bytes => SendData?.Invoke(bytes);   // DSR/DA 查詢回覆（如 ESC[6n 游標位置）
 
         // 右側深色垂直捲軸：拖曳即捲動 scrollback。內容寬度會扣掉捲軸寬，故文字不會被蓋住。
         _vscroll = new DarkScrollBar { Dock = DockStyle.Right, SmallChange = 1, Minimum = 0, Maximum = 0 };
@@ -54,8 +63,12 @@ public sealed class TerminalView : UserControl
     /// <summary>餵入遠端資料（須在 UI thread 呼叫）。</summary>
     public void Feed(byte[] data)
     {
+        int before = _buf.ScrollbackCount;
         _parser.Feed(data);
-        _scrollOffset = 0;          // 新輸出貼底
+        // 已貼底才跟隨新輸出；使用者往回看歷史時，補償 scrollback 增量讓畫面停在原處，
+        // 不會每來一筆輸出就被拉回底部。
+        if (_scrollOffset > 0)
+            _scrollOffset = Math.Min(_scrollOffset + (_buf.ScrollbackCount - before), _buf.ScrollbackCount);
         UpdateScrollBar();
         Invalidate();
     }
@@ -116,36 +129,48 @@ public sealed class TerminalView : UserControl
             if ((cell.Attr & CellAttr.Wide) != 0)
             {
                 var wr = new Rectangle(c * _cellW, y, _cellW * 2, _cellH);
-                using (var bb = new SolidBrush(bg)) g.FillRectangle(bb, wr);
+                FillRect(g, wr, bg);
                 DrawRun(g, cell.Ch == '\0' ? " " : cell.Ch.ToString(), cell.Attr, wr, fg);
                 c++;
                 continue;
             }
 
-            // 合併同屬性連續的窄字
+            // 合併同色同字型的連續窄字（每個 cell 的顏色只解析一次）
+            const CellAttr FontAttrs = CellAttr.Bold | CellAttr.Underline;
             int start = c;
-            var sb = new StringBuilder();
+            _runSb.Clear();
+            _runSb.Append(cell.Ch == '\0' ? ' ' : cell.Ch);
+            c++;
             while (c < line.Length)
             {
                 var cur = line[c];
                 if ((cur.Attr & (CellAttr.Wide | CellAttr.WideTrail)) != 0) break;
                 ResolveColors(cur, out var f2, out var b2, abs, c);
-                if (f2 != fg || b2 != bg || (cur.Attr & CellAttr.Bold) != (cell.Attr & CellAttr.Bold)) break;
-                sb.Append(cur.Ch == '\0' ? ' ' : cur.Ch);
+                if (f2 != fg || b2 != bg || (cur.Attr & FontAttrs) != (cell.Attr & FontAttrs)) break;
+                _runSb.Append(cur.Ch == '\0' ? ' ' : cur.Ch);
                 c++;
             }
             var rect = new Rectangle(start * _cellW, y, (c - start) * _cellW, _cellH);
-            using (var bb = new SolidBrush(bg)) g.FillRectangle(bb, rect);
-            DrawRun(g, sb.ToString(), cell.Attr, rect, fg);
+            FillRect(g, rect, bg);
+            DrawRun(g, _runSb.ToString(), cell.Attr, rect, fg);
         }
     }
 
+    private void FillRect(Graphics g, Rectangle rect, Color bg)
+    {
+        _fill.Color = bg;
+        g.FillRectangle(_fill, rect);
+    }
+
+    private Font FontFor(CellAttr attr)
+    {
+        bool bold = (attr & CellAttr.Bold) != 0, ul = (attr & CellAttr.Underline) != 0;
+        return bold ? (ul ? _fontBoldUnderline : _fontBold) : (ul ? _fontUnderline : _font);
+    }
+
     private void DrawRun(Graphics g, string text, CellAttr attr, Rectangle rect, Color fg)
     {
-        var style = (attr & CellAttr.Bold) != 0 ? FontStyle.Bold : FontStyle.Regular;
-        if ((attr & CellAttr.Underline) != 0) style |= FontStyle.Underline;
-        using var fnt = style == FontStyle.Regular ? _font : new Font(_font, style);
-        TextRenderer.DrawText(g, text, fnt, rect, fg,
+        TextRenderer.DrawText(g, text, FontFor(attr), rect, fg,
             TextFormatFlags.NoPadding | TextFormatFlags.NoPrefix | TextFormatFlags.Left);
     }
 
@@ -182,10 +207,7 @@ public sealed class TerminalView : UserControl
 
     protected override void OnKeyPress(KeyPressEventArgs e)
     {
-        if (!char.IsControl(e.KeyChar) || e.KeyChar is '\r' or '\t' or '\b' or '\x1b')
-        {
-            // \r,\t,\b,\x1b 已由 OnKeyDown 送出，這裡只送一般可列印字元與 Ctrl 組合碼
-        }
+        // \r,\t,\b,\x1b 已由 OnKeyDown 送出，這裡只送一般可列印字元與 Ctrl 組合碼
         if (e.KeyChar >= ' ' && e.KeyChar != '\x7f')
             SendData?.Invoke(Encoding.UTF8.GetBytes(e.KeyChar.ToString()));
         else if (char.IsControl(e.KeyChar) && e.KeyChar is not ('\r' or '\t' or '\b' or '\x1b'))
@@ -196,8 +218,16 @@ public sealed class TerminalView : UserControl
     // ── 滑鼠：scrollback / 選取 / 貼上 ───────────────────────
     protected override void OnMouseWheel(MouseEventArgs e)
     {
-        int delta = e.Delta / 120 * 3;
-        _scrollOffset = Math.Clamp(_scrollOffset + delta, 0, _buf.ScrollbackCount);
+        int notches = e.Delta / 120;
+        // alt screen（vim / htop 等全螢幕 TUI）沒有 scrollback：慣例是把滾輪轉成
+        // 上下方向鍵送給對方，讓應用程式自己捲動。
+        if (_buf.AltActive)
+        {
+            var seq = TerminalInput.WheelArrows(notches, _parser.AppCursorKeys);
+            if (seq != null) SendData?.Invoke(seq);
+            return;
+        }
+        _scrollOffset = Math.Clamp(_scrollOffset + notches * 3, 0, _buf.ScrollbackCount);
         UpdateScrollBar();
         Invalidate();
     }
@@ -397,6 +427,19 @@ public sealed class TerminalView : UserControl
         finally { ImmReleaseContext(Handle, hImc); }
     }
 
+    protected override void Dispose(bool disposing)
+    {
+        if (disposing)
+        {
+            _fill.Dispose();
+            _fontBold.Dispose();
+            _fontUnderline.Dispose();
+            _fontBoldUnderline.Dispose();
+            _font.Dispose();
+        }
+        base.Dispose(disposing);
+    }
+
     [StructLayout(LayoutKind.Sequential)] private struct POINT { public int x, y; }
     [StructLayout(LayoutKind.Sequential)] private struct RECT { public int left, top, right, bottom; }
     [StructLayout(LayoutKind.Sequential)] private struct COMPOSITIONFORM { public int dwStyle; public POINT ptCurrentPos; public RECT rcArea; }