From 2a3d220db447aea27d45e0a828beed102ce2fc7b Mon Sep 17 00:00:00 2001
From: Yun Chan <yunchan@twentyoz.kr>
Date: Mon, 1 Jun 2026 14:46:28 +0900
Subject: [PATCH] =?UTF-8?q?feat(ui):=20AI=20=EC=84=A4=EC=A0=95=EC=B0=BD=20?=
 =?UTF-8?q?+=20Codex=20CLI=20OAuth=20=EB=B0=B1=EC=97=94=EB=93=9C=20+=20?=
 =?UTF-8?q?=E2=9A=99=20=EC=A7=84=EC=9E=85=EC=A0=90?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

사용자 원래 요구였던 Codex non-interactive OAuth를 실제 동작까지 검증해 통합. ChatGPT 구독으로 API 키 없이 AI 변환.

- CodexChatClient: codex exec --skip-git-repo-check --ephemeral -o <file> - (stdin 프롬프트). 실제 한글→영어 번역 검증 완료
- ExternalProcessRunner: stdin 지원 + UTF-8 인코딩(한글 깨짐 해결)
- ExternalToolDetector.IsCodexAvailable() + public 승격
- LlmProvider: codex 백엔드 + auto 폴백(키 없으면 Codex)
- SettingsWindow: OpenAI/Anthropic 키(2단계 Verify) + Codex(OAuth) + 외부도구 상태/다운로드 CTA + 모델 선택
- App.Settings를 LlmProvider와 공유(키 저장 즉시 반영)
- MainWindow 네비바 ⚙ 설정 진입점
- 디자인: Cursor/Zed/Raycast 설정 UX + Radix 상태 토큰 영감
---
 src/Everything2Everything.App/App.xaml.cs     |  10 +-
 .../Views/FormatShiftTheme.xaml               |  37 ++++
 .../Views/MainWindow.xaml                     |   3 +
 .../Views/MainWindow.xaml.cs                  |   8 +
 .../Views/SettingsWindow.xaml                 | 162 ++++++++++++++++++
 .../Views/SettingsWindow.xaml.cs              | 157 +++++++++++++++++
 .../Converters/ChatClients.cs                 |  49 ++++++
 .../Converters/ExternalProcessRunner.cs       |  18 +-
 .../Converters/ExternalToolDetector.cs        |  30 +++-
 .../Converters/LlmProvider.cs                 |   7 +-
 .../Everything2EverythingBootstrap.cs         |   4 +-
 .../LlmProviderTests.cs                       |   3 +-
 12 files changed, 480 insertions(+), 8 deletions(-)
 create mode 100644 src/Everything2Everything.App/Views/SettingsWindow.xaml
 create mode 100644 src/Everything2Everything.App/Views/SettingsWindow.xaml.cs

diff --git a/src/Everything2Everything.App/App.xaml.cs b/src/Everything2Everything.App/App.xaml.cs
index 6c03b33..3c7b93a 100644
--- a/src/Everything2Everything.App/App.xaml.cs
+++ b/src/Everything2Everything.App/App.xaml.cs
@@ -7,7 +7,15 @@ namespace Everything2Everything.App;
 
 public partial class App : Application
 {
-    public ConversionEngine Engine { get; } = Everything2EverythingBootstrap.CreateDefault();
+    /// <summary>App·LlmProvider가 공유하는 설정 저장소 (키 저장 즉시 변환에 반영).</summary>
+    public ISettingsStore Settings { get; } = new DpapiSettingsStore();
+
+    public ConversionEngine Engine { get; }
+
+    public App()
+    {
+        Engine = Everything2EverythingBootstrap.CreateDefault(Settings);
+    }
 
     protected override async void OnStartup(StartupEventArgs e)
     {
diff --git a/src/Everything2Everything.App/Views/FormatShiftTheme.xaml b/src/Everything2Everything.App/Views/FormatShiftTheme.xaml
index 784011c..6aa50c0 100644
--- a/src/Everything2Everything.App/Views/FormatShiftTheme.xaml
+++ b/src/Everything2Everything.App/Views/FormatShiftTheme.xaml
@@ -338,4 +338,41 @@
             </Setter.Value>
         </Setter>
     </Style>
+
+    <!-- PasswordBox (API 키 입력) -->
+    <Style x:Key="FsPasswordInputStyle" TargetType="PasswordBox">
+        <Setter Property="Background" Value="{StaticResource FsBgInput}"/>
+        <Setter Property="Foreground" Value="{StaticResource FsTextPrimary}"/>
+        <Setter Property="BorderBrush" Value="{StaticResource FsBorderSubtle}"/>
+        <Setter Property="BorderThickness" Value="1"/>
+        <Setter Property="Padding" Value="10,8"/>
+        <Setter Property="FontFamily" Value="{StaticResource FsFontMono}"/>
+        <Setter Property="FontSize" Value="12"/>
+        <Setter Property="CaretBrush" Value="{StaticResource FsTextPrimary}"/>
+        <Setter Property="Template">
+            <Setter.Value>
+                <ControlTemplate TargetType="PasswordBox">
+                    <Border Background="{TemplateBinding Background}"
+                            BorderBrush="{TemplateBinding BorderBrush}"
+                            BorderThickness="{TemplateBinding BorderThickness}"
+                            CornerRadius="6"
+                            Padding="{TemplateBinding Padding}">
+                        <ScrollViewer x:Name="PART_ContentHost"/>
+                    </Border>
+                    <ControlTemplate.Triggers>
+                        <Trigger Property="IsFocused" Value="True">
+                            <Setter Property="BorderBrush" Value="{StaticResource FsAccentBlue}"/>
+                        </Trigger>
+                    </ControlTemplate.Triggers>
+                </ControlTemplate>
+            </Setter.Value>
+        </Setter>
+    </Style>
+
+    <!-- 손실 등급 dot (8px 원) -->
+    <Style x:Key="FsLossDotStyle" TargetType="Ellipse">
+        <Setter Property="Width" Value="8"/>
+        <Setter Property="Height" Value="8"/>
+        <Setter Property="VerticalAlignment" Value="Center"/>
+    </Style>
 </ResourceDictionary>
diff --git a/src/Everything2Everything.App/Views/MainWindow.xaml b/src/Everything2Everything.App/Views/MainWindow.xaml
index 31b5a84..3af73c6 100644
--- a/src/Everything2Everything.App/Views/MainWindow.xaml
+++ b/src/Everything2Everything.App/Views/MainWindow.xaml
@@ -334,6 +334,9 @@
 
                         <!-- Actions -->
                         <StackPanel Grid.Column="1" Orientation="Horizontal">
+                            <Button Content="⚙ 설정" Margin="0,0,8,0"
+                                    Style="{StaticResource FsSecondaryButtonStyle}"
+                                    Click="OnSettingsClick"/>
                             <Button Content="Register Menu" Margin="0,0,8,0"
                                     Style="{StaticResource FsSecondaryButtonStyle}"
                                     Click="OnRegisterClick"/>
diff --git a/src/Everything2Everything.App/Views/MainWindow.xaml.cs b/src/Everything2Everything.App/Views/MainWindow.xaml.cs
index b3db981..31d1123 100644
--- a/src/Everything2Everything.App/Views/MainWindow.xaml.cs
+++ b/src/Everything2Everything.App/Views/MainWindow.xaml.cs
@@ -87,6 +87,14 @@ public partial class MainWindow : Wpf.Ui.Controls.FluentWindow
         CapabilityStatusText.Visibility = Visibility.Visible;
     }
 
+    private void OnSettingsClick(object sender, RoutedEventArgs e)
+    {
+        var win = new SettingsWindow(((App)Application.Current).Settings) { Owner = this };
+        win.ShowDialog();
+        _ = RefreshCapabilityStatusAsync();
+        RefreshAvailableOutputFormats();
+    }
+
     private void PickAndAddFiles()
     {
         var dlg = new Microsoft.Win32.OpenFileDialog
diff --git a/src/Everything2Everything.App/Views/SettingsWindow.xaml b/src/Everything2Everything.App/Views/SettingsWindow.xaml
new file mode 100644
index 0000000..ba9d8d7
--- /dev/null
+++ b/src/Everything2Everything.App/Views/SettingsWindow.xaml
@@ -0,0 +1,162 @@
+<ui:FluentWindow x:Class="Everything2Everything.App.Views.SettingsWindow"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:ui="http://schemas.lepo.co/wpfui/2022/xaml"
+    Title="설정" Width="560" Height="720"
+    WindowStartupLocation="CenterOwner"
+    ExtendsContentIntoTitleBar="True"
+    WindowBackdropType="Mica"
+    Background="{StaticResource FsBgBase}">
+
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto"/>
+            <RowDefinition Height="*"/>
+            <RowDefinition Height="Auto"/>
+        </Grid.RowDefinitions>
+
+        <ui:TitleBar Grid.Row="0" Title="설정" ShowMaximize="False" ShowMinimize="False"/>
+
+        <ScrollViewer Grid.Row="1" VerticalScrollBarVisibility="Auto" Padding="24,8,24,16">
+            <StackPanel>
+
+                <!-- ===== AI 카드 ===== -->
+                <Border Background="{StaticResource FsBgSurface}"
+                        BorderBrush="{StaticResource FsBorderHairline}" BorderThickness="1"
+                        CornerRadius="10" Padding="20" Margin="0,0,0,16">
+                    <StackPanel>
+                        <TextBlock Text="AI 텍스트 변환" Style="{StaticResource FsBodyStyle}" FontWeight="SemiBold" FontSize="15"/>
+                        <TextBlock Text="요약 · 번역 · 교정에 사용됩니다 (종량 과금 · 네트워크 필요). 키가 없으면 AI 변환만 비활성됩니다."
+                                   Style="{StaticResource FsCaptionStyle}" TextWrapping="Wrap" Margin="0,4,0,16"/>
+
+                        <TextBlock Text="기본 백엔드" Style="{StaticResource FsLabelStyle}" Margin="0,0,0,6"/>
+                        <ComboBox x:Name="BackendCombo" Margin="0,0,0,16">
+                            <ComboBoxItem Content="자동 (API 키 우선, 없으면 Codex)"/>
+                            <ComboBoxItem Content="OpenAI (API 키)"/>
+                            <ComboBoxItem Content="Anthropic (API 키)"/>
+                            <ComboBoxItem Content="Codex CLI (ChatGPT 구독 OAuth)"/>
+                        </ComboBox>
+
+                        <!-- OpenAI -->
+                        <TextBlock Text="OpenAI API Key" Style="{StaticResource FsLabelStyle}" Margin="0,0,0,6"/>
+                        <Grid Margin="0,0,0,4">
+                            <Grid.ColumnDefinitions>
+                                <ColumnDefinition Width="*"/>
+                                <ColumnDefinition Width="Auto"/>
+                            </Grid.ColumnDefinitions>
+                            <PasswordBox x:Name="OpenAiKeyBox" Grid.Column="0"
+                                         Style="{StaticResource FsPasswordInputStyle}"
+                                         PasswordChanged="OnOpenAiKeyChanged"/>
+                            <Button x:Name="OpenAiVerifyBtn" Grid.Column="1" Content="확인"
+                                    Style="{StaticResource FsSecondaryButtonStyle}" Margin="8,0,0,0"
+                                    IsEnabled="False" Click="OnVerifyOpenAi"/>
+                        </Grid>
+                        <StackPanel Orientation="Horizontal" Margin="0,0,0,16">
+                            <Ellipse x:Name="OpenAiDot" Style="{StaticResource FsLossDotStyle}"
+                                     Fill="{StaticResource FsTextTertiary}" Margin="0,0,7,0"/>
+                            <TextBlock x:Name="OpenAiStatus" Text="키 미설정" Style="{StaticResource FsCaptionStyle}"/>
+                        </StackPanel>
+
+                        <!-- Anthropic -->
+                        <TextBlock Text="Anthropic API Key" Style="{StaticResource FsLabelStyle}" Margin="0,0,0,6"/>
+                        <Grid Margin="0,0,0,4">
+                            <Grid.ColumnDefinitions>
+                                <ColumnDefinition Width="*"/>
+                                <ColumnDefinition Width="Auto"/>
+                            </Grid.ColumnDefinitions>
+                            <PasswordBox x:Name="AnthropicKeyBox" Grid.Column="0"
+                                         Style="{StaticResource FsPasswordInputStyle}"
+                                         PasswordChanged="OnAnthropicKeyChanged"/>
+                            <Button x:Name="AnthropicVerifyBtn" Grid.Column="1" Content="확인"
+                                    Style="{StaticResource FsSecondaryButtonStyle}" Margin="8,0,0,0"
+                                    IsEnabled="False" Click="OnVerifyAnthropic"/>
+                        </Grid>
+                        <StackPanel Orientation="Horizontal" Margin="0,0,0,16">
+                            <Ellipse x:Name="AnthropicDot" Style="{StaticResource FsLossDotStyle}"
+                                     Fill="{StaticResource FsTextTertiary}" Margin="0,0,7,0"/>
+                            <TextBlock x:Name="AnthropicStatus" Text="키 미설정" Style="{StaticResource FsCaptionStyle}"/>
+                        </StackPanel>
+
+                        <!-- Codex CLI (OAuth) -->
+                        <TextBlock Text="Codex CLI (OAuth · API 키 불필요)" Style="{StaticResource FsLabelStyle}" Margin="0,0,0,6"/>
+                        <StackPanel Orientation="Horizontal" Margin="0,0,0,16">
+                            <Ellipse x:Name="CodexDot" Style="{StaticResource FsLossDotStyle}"
+                                     Fill="{StaticResource FsTextTertiary}" Margin="0,0,7,0"/>
+                            <TextBlock x:Name="CodexStatus" Text="확인 중…" Style="{StaticResource FsCaptionStyle}" VerticalAlignment="Center"/>
+                            <Button x:Name="CodexVerifyBtn" Content="테스트" Style="{StaticResource FsSecondaryButtonStyle}"
+                                    Margin="12,0,0,0" Padding="10,4" IsEnabled="False" Click="OnVerifyCodex"/>
+                        </StackPanel>
+
+                        <!-- 모델 -->
+                        <TextBlock Text="모델 (선택)" Style="{StaticResource FsLabelStyle}" Margin="0,0,0,6"/>
+                        <TextBox x:Name="ModelBox" Style="{StaticResource FsPathInputStyle}"/>
+                        <TextBlock Text="비워두면 기본 모델 (OpenAI: gpt-4o-mini, Anthropic: claude-3-5-sonnet-latest)"
+                                   Style="{StaticResource FsCaptionStyle}" Margin="0,6,0,0"/>
+                    </StackPanel>
+                </Border>
+
+                <!-- ===== 외부 도구 카드 ===== -->
+                <Border Background="{StaticResource FsBgSurface}"
+                        BorderBrush="{StaticResource FsBorderHairline}" BorderThickness="1"
+                        CornerRadius="10" Padding="20">
+                    <StackPanel>
+                        <TextBlock Text="외부 도구" Style="{StaticResource FsBodyStyle}" FontWeight="SemiBold" FontSize="15"/>
+                        <TextBlock Text="설치하면 영상/오디오·한글/Word 변환이 자동 활성화됩니다."
+                                   Style="{StaticResource FsCaptionStyle}" TextWrapping="Wrap" Margin="0,4,0,16"/>
+
+                        <!-- FFmpeg -->
+                        <Grid Margin="0,0,0,14">
+                            <Grid.ColumnDefinitions>
+                                <ColumnDefinition Width="*"/>
+                                <ColumnDefinition Width="Auto"/>
+                            </Grid.ColumnDefinitions>
+                            <StackPanel Grid.Column="0">
+                                <StackPanel Orientation="Horizontal">
+                                    <Ellipse x:Name="FfmpegDot" Style="{StaticResource FsLossDotStyle}"
+                                             Fill="{StaticResource FsStatusWarn}" Margin="0,0,7,0"/>
+                                    <TextBlock Text="FFmpeg" Style="{StaticResource FsBodyStyle}" FontWeight="Medium"/>
+                                    <TextBlock x:Name="FfmpegStatus" Text="미설치" Style="{StaticResource FsCaptionStyle}" Margin="8,0,0,0" VerticalAlignment="Center"/>
+                                </StackPanel>
+                                <TextBlock Text="영상/오디오 변환 (mp4·webm·mp3·flac…)" Style="{StaticResource FsCaptionStyle}" Margin="15,3,0,0"/>
+                            </StackPanel>
+                            <StackPanel Grid.Column="1" Orientation="Horizontal" VerticalAlignment="Center">
+                                <Button Content="다운로드" Style="{StaticResource FsSecondaryButtonStyle}" Click="OnDownloadFfmpeg"/>
+                                <Button Content="폴더 열기" Style="{StaticResource FsSecondaryButtonStyle}" Margin="6,0,0,0" Click="OnOpenFfmpegFolder"/>
+                            </StackPanel>
+                        </Grid>
+
+                        <!-- LibreOffice -->
+                        <Grid>
+                            <Grid.ColumnDefinitions>
+                                <ColumnDefinition Width="*"/>
+                                <ColumnDefinition Width="Auto"/>
+                            </Grid.ColumnDefinitions>
+                            <StackPanel Grid.Column="0">
+                                <StackPanel Orientation="Horizontal">
+                                    <Ellipse x:Name="LibreDot" Style="{StaticResource FsLossDotStyle}"
+                                             Fill="{StaticResource FsStatusWarn}" Margin="0,0,7,0"/>
+                                    <TextBlock Text="LibreOffice" Style="{StaticResource FsBodyStyle}" FontWeight="Medium"/>
+                                    <TextBlock x:Name="LibreStatus" Text="미설치" Style="{StaticResource FsCaptionStyle}" Margin="8,0,0,0" VerticalAlignment="Center"/>
+                                </StackPanel>
+                                <TextBlock Text="한글/Word/문서 변환 (HWP·DOCX→PDF/이미지). 한글은 H2Orestart 확장 필요." Style="{StaticResource FsCaptionStyle}" Margin="15,3,0,0" TextWrapping="Wrap"/>
+                            </StackPanel>
+                            <StackPanel Grid.Column="1" Orientation="Horizontal" VerticalAlignment="Center">
+                                <Button Content="다운로드" Style="{StaticResource FsSecondaryButtonStyle}" Click="OnDownloadLibre"/>
+                            </StackPanel>
+                        </Grid>
+                    </StackPanel>
+                </Border>
+
+            </StackPanel>
+        </ScrollViewer>
+
+        <!-- ===== 푸터 ===== -->
+        <Border Grid.Row="2" Background="{StaticResource FsBgPanel}"
+                BorderBrush="{StaticResource FsBorderSubtle}" BorderThickness="0,1,0,0" Padding="24,14">
+            <StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
+                <Button Content="닫기" Style="{StaticResource FsSecondaryButtonStyle}" Padding="18,8" Click="OnClose"/>
+                <Button Content="저장" Style="{StaticResource FsPrimaryButtonStyle}" Padding="22,8" Margin="8,0,0,0" Click="OnSave"/>
+            </StackPanel>
+        </Border>
+    </Grid>
+</ui:FluentWindow>
diff --git a/src/Everything2Everything.App/Views/SettingsWindow.xaml.cs b/src/Everything2Everything.App/Views/SettingsWindow.xaml.cs
new file mode 100644
index 0000000..7a5b4fb
--- /dev/null
+++ b/src/Everything2Everything.App/Views/SettingsWindow.xaml.cs
@@ -0,0 +1,157 @@
+using System.Diagnostics;
+using System.Threading;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Media;
+using System.Windows.Shapes;
+using Everything2Everything.Core;
+using Everything2Everything.Core.Converters;
+
+namespace Everything2Everything.App.Views;
+
+public partial class SettingsWindow : Wpf.Ui.Controls.FluentWindow
+{
+    private readonly ISettingsStore _settings;
+
+    public SettingsWindow(ISettingsStore settings)
+    {
+        _settings = settings;
+        InitializeComponent();
+        LoadSettings();
+        RefreshToolStatus();
+    }
+
+    private void LoadSettings()
+    {
+        var backend = (_settings.Get("ai.backend") ?? "auto").ToLowerInvariant();
+        BackendCombo.SelectedIndex = backend switch
+        {
+            "openai" => 1,
+            "anthropic" => 2,
+            "codex" => 3,
+            _ => 0,
+        };
+        ModelBox.Text = _settings.Get("ai.model") ?? string.Empty;
+
+        SetKeyStatus(OpenAiDot, OpenAiStatus, _settings.Contains("openai.apikey"), HasEnv("OPENAI_API_KEY"));
+        SetKeyStatus(AnthropicDot, AnthropicStatus, _settings.Contains("anthropic.apikey"), HasEnv("ANTHROPIC_API_KEY"));
+    }
+
+    private static bool HasEnv(string name) => !string.IsNullOrEmpty(Environment.GetEnvironmentVariable(name));
+
+    private void SetKeyStatus(Ellipse dot, TextBlock text, bool stored, bool env)
+    {
+        if (stored) { dot.Fill = Res("FsStatusSuccess"); text.Text = "저장됨 (변경하려면 새 키 입력)"; }
+        else if (env) { dot.Fill = Res("FsStatusInfo"); text.Text = "환경변수에서 감지됨"; }
+        else { dot.Fill = Res("FsTextTertiary"); text.Text = "키 미설정"; }
+    }
+
+    private static Brush Res(string key) => (Brush)Application.Current.Resources[key];
+
+    // --- 2단계 Verify: 형식 검사로 버튼 활성화 → 클릭 시에만 실제 핑 ---
+
+    private void OnOpenAiKeyChanged(object sender, RoutedEventArgs e)
+        => OpenAiVerifyBtn.IsEnabled = OpenAiKeyBox.Password.StartsWith("sk-", StringComparison.Ordinal);
+
+    private void OnAnthropicKeyChanged(object sender, RoutedEventArgs e)
+        => AnthropicVerifyBtn.IsEnabled = AnthropicKeyBox.Password.StartsWith("sk-ant-", StringComparison.Ordinal);
+
+    private async void OnVerifyOpenAi(object sender, RoutedEventArgs e)
+        => await VerifyAsync(OpenAiDot, OpenAiStatus, OpenAiVerifyBtn,
+            new OpenAiChatClient(OpenAiKeyBox.Password), ModelOr("gpt-4o-mini"));
+
+    private async void OnVerifyAnthropic(object sender, RoutedEventArgs e)
+        => await VerifyAsync(AnthropicDot, AnthropicStatus, AnthropicVerifyBtn,
+            new AnthropicChatClient(AnthropicKeyBox.Password), ModelOr("claude-3-5-sonnet-latest"));
+
+    private async void OnVerifyCodex(object sender, RoutedEventArgs e)
+        => await VerifyAsync(CodexDot, CodexStatus, CodexVerifyBtn, new CodexChatClient(), ModelOr(string.Empty));
+
+    private string ModelOr(string fallback)
+        => string.IsNullOrWhiteSpace(ModelBox.Text) ? fallback : ModelBox.Text.Trim();
+
+    private async Task VerifyAsync(Ellipse dot, TextBlock text, Button btn, IChatClient client, string model)
+    {
+        btn.IsEnabled = false;
+        dot.Fill = Res("FsStatusInfo");
+        text.Text = "확인 중…";
+        try
+        {
+            using var cts = new CancellationTokenSource(TimeSpan.FromMinutes(2));
+            var reply = await client.CompleteAsync("Reply with exactly: OK", "ping", model, 8, cts.Token);
+            dot.Fill = Res("FsStatusSuccess");
+            text.Text = string.IsNullOrWhiteSpace(reply) ? $"확인됨 ({client.Name})" : $"확인됨 — {client.Name}";
+        }
+        catch (Exception ex)
+        {
+            dot.Fill = Res("FsStatusDanger");
+            text.Text = "실패: " + Trunc(ex.Message);
+        }
+        finally
+        {
+            btn.IsEnabled = true;
+        }
+    }
+
+    private static string Trunc(string s) => s.Length > 64 ? s[..64] + "…" : s;
+
+    private void RefreshToolStatus()
+    {
+        var ffmpeg = ExternalToolDetector.TryFindFfmpeg(out _);
+        FfmpegDot.Fill = Res(ffmpeg ? "FsStatusSuccess" : "FsStatusWarn");
+        FfmpegStatus.Text = ffmpeg ? "준비됨" : "미설치";
+
+        var libre = ExternalToolDetector.TryFindLibreOfficeSoffice(out _);
+        LibreDot.Fill = Res(libre ? "FsStatusSuccess" : "FsStatusWarn");
+        LibreStatus.Text = libre ? "준비됨" : "미설치";
+
+        var codex = ExternalToolDetector.IsCodexAvailable();
+        CodexDot.Fill = Res(codex ? "FsStatusSuccess" : "FsTextTertiary");
+        CodexStatus.Text = codex ? "설치됨 — 키 없이 사용 가능" : "미설치 (npm i -g @openai/codex)";
+        CodexVerifyBtn.IsEnabled = codex;
+    }
+
+    private void OnSave(object sender, RoutedEventArgs e)
+    {
+        var backend = BackendCombo.SelectedIndex switch
+        {
+            1 => "openai",
+            2 => "anthropic",
+            3 => "codex",
+            _ => "auto",
+        };
+        _settings.Set("ai.backend", backend);
+
+        var model = ModelBox.Text?.Trim();
+        if (string.IsNullOrEmpty(model)) _settings.Remove("ai.model");
+        else _settings.Set("ai.model", model);
+
+        if (OpenAiKeyBox.Password.Length > 0) _settings.Set("openai.apikey", OpenAiKeyBox.Password);
+        if (AnthropicKeyBox.Password.Length > 0) _settings.Set("anthropic.apikey", AnthropicKeyBox.Password);
+
+        Close();
+    }
+
+    private void OnClose(object sender, RoutedEventArgs e) => Close();
+
+    private void OnDownloadFfmpeg(object sender, RoutedEventArgs e)
+        => OpenUrl("https://github.com/BtbN/FFmpeg-Builds/releases");
+
+    private void OnDownloadLibre(object sender, RoutedEventArgs e)
+        => OpenUrl("https://www.libreoffice.org/download/");
+
+    private void OnOpenFfmpegFolder(object sender, RoutedEventArgs e)
+    {
+        var dir = System.IO.Path.Combine(
+            Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
+            "Everything2Everything", "ffmpeg");
+        Directory.CreateDirectory(dir);
+        OpenUrl(dir);
+    }
+
+    private static void OpenUrl(string target)
+    {
+        try { Process.Start(new ProcessStartInfo(target) { UseShellExecute = true }); }
+        catch { /* 브라우저/탐색기 실행 실패 무시 */ }
+    }
+}
diff --git a/src/Everything2Everything.Core/Converters/ChatClients.cs b/src/Everything2Everything.Core/Converters/ChatClients.cs
index df4fee1..b751beb 100644
--- a/src/Everything2Everything.Core/Converters/ChatClients.cs
+++ b/src/Everything2Everything.Core/Converters/ChatClients.cs
@@ -88,3 +88,52 @@ public sealed class AnthropicChatClient : IChatClient
 
     private static string Truncate(string s) => s.Length > 400 ? s[..400] : s;
 }
+
+/// <summary>
+/// OpenAI Codex CLI를 non-interactive로 호출하는 백엔드. ChatGPT 구독 OAuth(auth.json)를 그대로
+/// 재사용하므로 API 키 없이 동작한다. `codex exec --skip-git-repo-check --ephemeral -o &lt;file&gt; -`
+/// 형태로 프롬프트를 stdin으로 전달하고, 최종 메시지를 파일에서 읽는다.
+/// </summary>
+public sealed class CodexChatClient : IChatClient
+{
+    public string Name => "Codex CLI (OAuth)";
+
+    public async Task<string> CompleteAsync(string systemPrompt, string userPrompt, string model, int maxTokens, CancellationToken ct)
+    {
+        var prompt = string.IsNullOrWhiteSpace(systemPrompt) ? userPrompt : systemPrompt + "\n\n---\n\n" + userPrompt;
+        var outFile = Path.Combine(Path.GetTempPath(), "e2e_codex_" + Guid.NewGuid().ToString("N") + ".txt");
+
+        var args = new List<string> { "/c", "codex", "exec", "--skip-git-repo-check", "--ephemeral", "-o", outFile };
+        if (!string.IsNullOrWhiteSpace(model)) { args.Add("-m"); args.Add(model); }
+        args.Add("-"); // 프롬프트를 stdin으로 (인자 이스케이프 회피)
+
+        try
+        {
+            var r = await ExternalProcessRunner.RunAsync(
+                "cmd.exe", args, TimeSpan.FromMinutes(5), workingDirectory: null,
+                cancellationToken: ct, stdinText: prompt).ConfigureAwait(false);
+
+            if (r.TimedOut)
+                throw new InvalidOperationException("Codex CLI 응답이 시간 초과되었습니다 (5분).");
+
+            if (File.Exists(outFile))
+            {
+                var msg = await File.ReadAllTextAsync(outFile, ct).ConfigureAwait(false);
+                if (!string.IsNullOrWhiteSpace(msg)) return msg.Trim();
+            }
+
+            if (!r.Success)
+            {
+                var detail = !string.IsNullOrWhiteSpace(r.StdErr) ? r.StdErr : r.StdOut;
+                throw new InvalidOperationException($"Codex CLI 오류 (exit {r.ExitCode}): {Truncate(detail)}");
+            }
+            return r.StdOut.Trim();
+        }
+        finally
+        {
+            try { if (File.Exists(outFile)) File.Delete(outFile); } catch { }
+        }
+    }
+
+    private static string Truncate(string s) => s.Length > 400 ? s[..400] : s;
+}
diff --git a/src/Everything2Everything.Core/Converters/ExternalProcessRunner.cs b/src/Everything2Everything.Core/Converters/ExternalProcessRunner.cs
index 361dd22..6d5c24a 100644
--- a/src/Everything2Everything.Core/Converters/ExternalProcessRunner.cs
+++ b/src/Everything2Everything.Core/Converters/ExternalProcessRunner.cs
@@ -19,7 +19,8 @@ public static class ExternalProcessRunner
         IEnumerable<string> arguments,
         TimeSpan? timeout = null,
         string? workingDirectory = null,
-        CancellationToken cancellationToken = default)
+        CancellationToken cancellationToken = default,
+        string? stdinText = null)
     {
         var psi = new ProcessStartInfo
         {
@@ -28,7 +29,11 @@ public static class ExternalProcessRunner
             CreateNoWindow = true,
             RedirectStandardOutput = true,
             RedirectStandardError = true,
+            RedirectStandardInput = stdinText is not null,
+            StandardOutputEncoding = Encoding.UTF8,
+            StandardErrorEncoding = Encoding.UTF8,
         };
+        if (stdinText is not null) psi.StandardInputEncoding = new UTF8Encoding(false);
         foreach (var a in arguments) psi.ArgumentList.Add(a);
         if (!string.IsNullOrEmpty(workingDirectory)) psi.WorkingDirectory = workingDirectory;
 
@@ -44,6 +49,17 @@ public static class ExternalProcessRunner
         proc.BeginOutputReadLine();
         proc.BeginErrorReadLine();
 
+        // 프롬프트 등 긴 입력을 인자 이스케이프 없이 stdin으로 안전하게 전달
+        if (stdinText is not null)
+        {
+            try
+            {
+                await proc.StandardInput.WriteAsync(stdinText.AsMemory(), cancellationToken).ConfigureAwait(false);
+                proc.StandardInput.Close();
+            }
+            catch { /* 프로세스가 stdin을 안 읽고 종료한 경우 무시 */ }
+        }
+
         using var linked = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
         if (timeout is { } t) linked.CancelAfter(t);
 
diff --git a/src/Everything2Everything.Core/Converters/ExternalToolDetector.cs b/src/Everything2Everything.Core/Converters/ExternalToolDetector.cs
index 189c2e7..cfe24bd 100644
--- a/src/Everything2Everything.Core/Converters/ExternalToolDetector.cs
+++ b/src/Everything2Everything.Core/Converters/ExternalToolDetector.cs
@@ -2,7 +2,7 @@ using Microsoft.Win32;
 
 namespace Everything2Everything.Core.Converters;
 
-internal static class ExternalToolDetector
+public static class ExternalToolDetector
 {
     public static bool TryFindLibreOfficeSoffice(out string sofficePath)
     {
@@ -82,6 +82,34 @@ internal static class ExternalToolDetector
         return false;
     }
 
+    /// <summary>
+    /// codex CLI(OpenAI Codex, ChatGPT 구독 OAuth 재사용) 설치 여부. npm 글로벌 + PATH에서
+    /// codex.cmd/codex.exe/codex.ps1을 탐지한다.
+    /// </summary>
+    public static bool IsCodexAvailable()
+    {
+        var names = new[] { "codex.cmd", "codex.exe", "codex.ps1" };
+        var dirs = new List<string>();
+
+        var appdata = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
+        if (!string.IsNullOrEmpty(appdata)) dirs.Add(Path.Combine(appdata, "npm"));
+
+        var pathEnv = Environment.GetEnvironmentVariable("PATH") ?? "";
+        foreach (var d in pathEnv.Split(Path.PathSeparator))
+            if (!string.IsNullOrWhiteSpace(d)) dirs.Add(d.Trim());
+
+        foreach (var dir in dirs.Distinct())
+        {
+            try
+            {
+                foreach (var n in names)
+                    if (File.Exists(Path.Combine(dir, n))) return true;
+            }
+            catch { /* 잘못된 경로 무시 */ }
+        }
+        return false;
+    }
+
     public static bool IsH2OrestartInstalled()
     {
         try
diff --git a/src/Everything2Everything.Core/Converters/LlmProvider.cs b/src/Everything2Everything.Core/Converters/LlmProvider.cs
index e8eba99..e95b351 100644
--- a/src/Everything2Everything.Core/Converters/LlmProvider.cs
+++ b/src/Everything2Everything.Core/Converters/LlmProvider.cs
@@ -22,7 +22,7 @@ public sealed class LlmProvider : IConverterProvider
             new ConversionPair(".md", ".md", LossClass.Recode),
         },
         Status: ProviderStatus.RequiresExternal,
-        Summary: "OpenAI 또는 Anthropic API로 텍스트를 요약·번역·교정합니다 (✨AI · 종량 과금 · 네트워크 필요). API 키가 없으면 비활성됩니다.",
+        Summary: "OpenAI/Anthropic API 또는 Codex CLI(ChatGPT 구독 OAuth, 키 불필요)로 텍스트를 요약·번역·교정합니다 (✨AI · 네트워크 필요). 키도 Codex도 없으면 비활성됩니다.",
         ExternalDependencies: new[]
         {
             new ExternalDependency(
@@ -96,10 +96,13 @@ public sealed class LlmProvider : IConverterProvider
             return openaiKey is null ? (null, "") : (new OpenAiChatClient(openaiKey), ai.Model ?? "gpt-4o-mini");
         if (backend == "anthropic")
             return anthropicKey is null ? (null, "") : (new AnthropicChatClient(anthropicKey), ai.Model ?? "claude-3-5-sonnet-latest");
+        if (backend == "codex")
+            return ExternalToolDetector.IsCodexAvailable() ? (new CodexChatClient(), ai.Model ?? "") : (null, "");
 
-        // auto: OpenAI 우선, 없으면 Anthropic
+        // auto: API 키 우선, 없으면 Codex CLI(ChatGPT 구독 OAuth)
         if (openaiKey is not null) return (new OpenAiChatClient(openaiKey), ai.Model ?? "gpt-4o-mini");
         if (anthropicKey is not null) return (new AnthropicChatClient(anthropicKey), ai.Model ?? "claude-3-5-sonnet-latest");
+        if (ExternalToolDetector.IsCodexAvailable()) return (new CodexChatClient(), ai.Model ?? "");
         return (null, "");
     }
 
diff --git a/src/Everything2Everything.Core/Everything2EverythingBootstrap.cs b/src/Everything2Everything.Core/Everything2EverythingBootstrap.cs
index 993ef3c..b13cff2 100644
--- a/src/Everything2Everything.Core/Everything2EverythingBootstrap.cs
+++ b/src/Everything2Everything.Core/Everything2EverythingBootstrap.cs
@@ -4,9 +4,9 @@ namespace Everything2Everything.Core;
 
 public static class Everything2EverythingBootstrap
 {
-    public static ConversionEngine CreateDefault()
+    public static ConversionEngine CreateDefault(ISettingsStore? settings = null)
     {
-        var settings = new DpapiSettingsStore();
+        settings ??= new DpapiSettingsStore();
         var magick = new Converters.MagickProvider();
         var pdf = new Converters.PdfProvider();
         var providers = new IConverterProvider[]
diff --git a/src/Everything2Everything.Tests/LlmProviderTests.cs b/src/Everything2Everything.Tests/LlmProviderTests.cs
index eecff8e..5673273 100644
--- a/src/Everything2Everything.Tests/LlmProviderTests.cs
+++ b/src/Everything2Everything.Tests/LlmProviderTests.cs
@@ -25,7 +25,8 @@ public class LlmProviderTests
     [Fact]
     public async Task NoKey_IsNotReady()
     {
-        if (EnvHasKey()) return; // 환경변수 키가 있으면 이 단언은 건너뜀
+        // 환경변수 키 또는 codex CLI(OAuth)가 있으면 AI가 활성화되므로 이 단언은 건너뜀
+        if (EnvHasKey() || ExternalToolDetector.IsCodexAvailable()) return;
         var p = new LlmProvider(new FakeStore());
         var a = await p.CheckAvailabilityAsync();
         Assert.False(a.IsReady);