diff --git a/Services/ClaudeCliService.cs b/Services/ClaudeCliService.cs
index c553c19..99e80f2 100644
--- a/Services/ClaudeCliService.cs
+++ b/Services/ClaudeCliService.cs
@@ -39,7 +39,6 @@ public class ClaudeCliService
     {
         var psi = new ProcessStartInfo
         {
-            FileName = _cliPath,
             RedirectStandardInput = redirectInput,
             RedirectStandardOutput = true,
             RedirectStandardError = true,
@@ -49,12 +48,91 @@ public class ClaudeCliService
             StandardErrorEncoding = Encoding.UTF8
         };
 
-        foreach (var arg in args)
-            psi.ArgumentList.Add(arg);
+        if (OperatingSystem.IsWindows())
+        {
+            // Auf Windows: über cmd.exe wrappen und Codepage 65001 (UTF-8) erzwingen.
+            // Sonst kann der Child-Prozess (claude.exe) Output mit CP1252/CP850 schreiben,
+            // was beim UTF-8-Decode zu Replacement-Chars (�) für Umlaute / Em-Dash führt.
+            var sb = new StringBuilder();
+            sb.Append("/S /C \"chcp 65001 >nul && ");
+            sb.Append(QuoteArgForCmd(_cliPath));
+            foreach (var a in args)
+            {
+                sb.Append(' ');
+                sb.Append(QuoteArgForCmd(a));
+            }
+            sb.Append('"');
+
+            psi.FileName = Environment.GetEnvironmentVariable("ComSpec") ?? "cmd.exe";
+            psi.Arguments = sb.ToString();
+        }
+        else
+        {
+            psi.FileName = _cliPath;
+            foreach (var arg in args)
+                psi.ArgumentList.Add(arg);
+        }
+
+        // UTF-8-Locale für den Child setzen (Node.js / diverse Tools respektieren das).
+        // Schadet auf Windows nicht, hilft auf manchen Linux-Setups (z.B. systemd-Diensten ohne LANG).
+        psi.Environment["LANG"] = "en_US.UTF-8";
+        psi.Environment["LC_ALL"] = "en_US.UTF-8";
+        psi.Environment["PYTHONIOENCODING"] = "utf-8";
 
         return psi;
     }
 
+    /// <summary>
+    /// Quotet ein Argument im Stil von Microsoft CRT (CommandLineToArgvW),
+    /// passend für die Verwendung innerhalb von cmd.exe /C "...".
+    /// </summary>
+    private static string QuoteArgForCmd(string arg)
+    {
+        if (string.IsNullOrEmpty(arg))
+            return "\"\"";
+
+        bool needsQuoting = false;
+        foreach (var c in arg)
+        {
+            if (c == ' ' || c == '\t' || c == '"' || c == '\n' || c == '\v')
+            {
+                needsQuoting = true;
+                break;
+            }
+        }
+
+        if (!needsQuoting)
+            return arg;
+
+        var sb = new StringBuilder();
+        sb.Append('"');
+        int backslashes = 0;
+        foreach (var c in arg)
+        {
+            if (c == '\\')
+            {
+                backslashes++;
+            }
+            else if (c == '"')
+            {
+                // 2n+1 Backslashes vor einem Anführungszeichen
+                sb.Append('\\', backslashes * 2 + 1);
+                sb.Append('"');
+                backslashes = 0;
+            }
+            else
+            {
+                sb.Append('\\', backslashes);
+                sb.Append(c);
+                backslashes = 0;
+            }
+        }
+        // 2n Backslashes am Ende (vor dem schließenden ")
+        sb.Append('\\', backslashes * 2);
+        sb.Append('"');
+        return sb.ToString();
+    }
+
     private static string FindCliPath()
     {
         // 1. Expliziter Pfad über Umgebungsvariable (höchste Priorität)