diff --git a/Endpoints/ChatEndpoint.cs b/Endpoints/ChatEndpoint.cs
index 35543d3..04e2edb 100644
--- a/Endpoints/ChatEndpoint.cs
+++ b/Endpoints/ChatEndpoint.cs
@@ -52,7 +52,19 @@ public static class ChatEndpoint
         var userId = req.HttpContext.GetUserId();
         var maxIterations = config.GetValue<int>("MaxIterations", 100);
 
-        var ctx = await chatService.PrepareContext(sessionId, userId, maxIterations);
+        // Bei Choice-Response: planMode vom vorherigen Chain übernehmen
+        var effectivePlanMode = body.PlanMode;
+        if (isChoiceResponse && !effectivePlanMode)
+        {
+            var prevChainId = await chatService.FindChainWithToolCall(sessionId, body.ChoiceToolCallId);
+            if (prevChainId != null)
+            {
+                var prevChain = await db.GetChain(prevChainId);
+                if (prevChain != null) effectivePlanMode = prevChain.PlanMode;
+            }
+        }
+
+        var ctx = await chatService.PrepareContext(sessionId, userId, maxIterations, planMode: effectivePlanMode);
         if (ctx == null)
         {
             res.StatusCode = 400;
@@ -132,7 +144,7 @@ public static class ChatEndpoint
 
         try
         {
-            await anthropic.StreamChat(res, ctx.ModelId, ctx.SystemPrompt, messages, ctx.ChainId, ctx.Workspace, sessionId, agentId: ctx.AgentId, useMemory: ctx.UseMemory, webSearchVersion: ctx.WebSearchVersion, maxIterations: ctx.MaxIterations, toolChoice: effectiveToolChoice, review: ctx.Review, finalizer: ctx.Finalizer, allowUserChoice: ctx.Agent?.AllowUserChoice ?? true, cancellationToken: linkedCts.Token);
+            await anthropic.StreamChat(res, ctx.ModelId, ctx.SystemPrompt, messages, ctx.ChainId, ctx.Workspace, sessionId, agentId: ctx.AgentId, useMemory: ctx.UseMemory, webSearchVersion: ctx.WebSearchVersion, maxIterations: ctx.MaxIterations, toolChoice: effectiveToolChoice, review: ctx.Review, finalizer: ctx.Finalizer, allowUserChoice: ctx.Agent?.AllowUserChoice ?? true, planMode: ctx.PlanMode, cancellationToken: linkedCts.Token);
         }
         finally
         {
diff --git a/Models/ChainRecord.cs b/Models/ChainRecord.cs
index 9785a3c..b8a15e5 100644
--- a/Models/ChainRecord.cs
+++ b/Models/ChainRecord.cs
@@ -19,5 +19,6 @@ public class ChainRecord
     public string ToolNames { get; set; }
     public string ArchiveId { get; set; }
     public string StreamErrorInfo { get; set; }
+    public bool PlanMode { get; set; }
     public string CreatedAt { get; set; }
 }
diff --git a/Models/ChatContext.cs b/Models/ChatContext.cs
index 2372a33..a87c406 100644
--- a/Models/ChatContext.cs
+++ b/Models/ChatContext.cs
@@ -17,6 +17,7 @@ public class ChatContext
     public int MaxIterations { get; set; }
     public AgentRecord Agent { get; set; }
     public SessionRecord Session { get; set; }
+    public bool PlanMode { get; set; }
 
     // Review-Agent
     public ReviewContext Review { get; set; }
diff --git a/Models/ChatModels.cs b/Models/ChatModels.cs
index a13526b..36e06e9 100644
--- a/Models/ChatModels.cs
+++ b/Models/ChatModels.cs
@@ -144,4 +144,10 @@ public class ChatRequest
     /// </summary>
     [JsonPropertyName("choiceResult")]
     public string ChoiceResult { get; set; }
+
+    /// <summary>
+    /// Wenn true: Plan-Modus aktiv. Nur Read-only Tools, keine Datei-Änderungen.
+    /// </summary>
+    [JsonPropertyName("planMode")]
+    public bool PlanMode { get; set; }
 }
diff --git a/Services/AnthropicService.cs b/Services/AnthropicService.cs
index 22dffe4..c84afb0 100644
--- a/Services/AnthropicService.cs
+++ b/Services/AnthropicService.cs
@@ -50,6 +50,7 @@ public class AnthropicService
         ReviewContext review = null,
         FinalizerContext finalizer = null,
         bool allowUserChoice = true,
+        bool planMode = false,
         CancellationToken cancellationToken = default)
     {
         var sw = System.Diagnostics.Stopwatch.StartNew();
@@ -58,6 +59,20 @@ public class AnthropicService
         int reviewRound = 0;
         string lastStopReason = "";
 
+        // Plan-Modus: System-Prompt-Ergänzung
+        if (planMode && systemPrompt != null)
+        {
+            systemPrompt.Add(new { type = "text", text = @"## Plan-Modus aktiv
+Der User hat den Plan-Modus aktiviert. Du DARFST KEINE Änderungen vornehmen:
+- KEINE Dateien erstellen, bearbeiten oder löschen
+- KEINE Shell-Befehle ausführen die Änderungen vornehmen (Commits, Installationen etc.)
+- NUR lesen, analysieren, suchen und planen
+- Nutze read_file, list_files, glob, grep und web_search um den Codebase zu verstehen
+- Nutze ask_user_choice um Rückfragen zu stellen und Anforderungen zu klären
+- Erstelle einen strukturierten Plan mit Aufgaben, Abhängigkeiten und Reihenfolge
+- Der User wird den Plan-Modus deaktivieren wenn du mit der Umsetzung beginnen sollst" });
+        }
+
         var chain = new ChainRecord
         {
             ChainId = chainId,
@@ -93,13 +108,19 @@ public class AnthropicService
                 {
                     var tools = new List<object>();
                     if (hasTools)
-                        tools.AddRange(_toolService.GetToolDefinitions(includeFileTools: hasWorkspace, includeMemory: includeMemory, includeUserChoice: allowUserChoice));
+                    {
+                        var allTools = _toolService.GetToolDefinitions(includeFileTools: hasWorkspace, includeMemory: includeMemory, includeUserChoice: allowUserChoice);
+                        if (planMode)
+                            allTools = _toolService.FilterReadOnlyTools(allTools);
+                        tools.AddRange(allTools);
+                    }
                     if (hasWebSearch)
                         tools.Add(new { type = webSearchVersion, name = "web_search", max_uses = 5 });
                     payload["tools"] = tools;
                     // "any" erzwingt Tool-Nutzung, aber nur in der ersten Iteration,
                     // damit Claude nicht endlos Tools aufruft wenn die Aufgabe erledigt ist.
-                    var effectiveChoice = (toolChoice == "any" && iterations == 1) ? "any" : "auto";
+                    // Im Plan-Modus nie "any" erzwingen – Claude soll frei antworten können.
+                    var effectiveChoice = (!planMode && toolChoice == "any" && iterations == 1) ? "any" : "auto";
                     payload["tool_choice"] = new { type = effectiveChoice };
                 }
 
@@ -252,7 +273,8 @@ public class AnthropicService
                         chainId,
                         durationMs = sw.ElapsedMilliseconds,
                         stopReason = finalStopReason,
-                        streamErrorInfo
+                        streamErrorInfo,
+                        planMode
                     }, cancellationToken);
                     return;
                 }
diff --git a/Services/ChatService.cs b/Services/ChatService.cs
index 6cf44a1..39d64de 100644
--- a/Services/ChatService.cs
+++ b/Services/ChatService.cs
@@ -42,7 +42,7 @@ public class ChatService
     /// <summary>
     /// Baut den vollständigen ChatContext auf: Agent, Model, SystemPrompt, Chain, Workspace etc.
     /// </summary>
-    public async Task<ChatContext> PrepareContext(string sessionId, string userId, int maxIterations = 100)
+    public async Task<ChatContext> PrepareContext(string sessionId, string userId, int maxIterations = 100, bool planMode = false)
     {
         var session = await _db.GetSession(sessionId);
         if (session == null || (userId != null && session.UserId != userId) || string.IsNullOrEmpty(session.AgentId))
@@ -94,7 +94,8 @@ public class ChatService
             Model = modelId,
             SystemPrompt = systemPromptText,
             ToolChoice = (hasWorkspace || includeMemory) ? toolChoice : null,
-            ToolNames = toolNames
+            ToolNames = toolNames,
+            PlanMode = planMode
         });
 
         await _db.UpdateSessionTimestamp(sessionId);
@@ -193,7 +194,8 @@ public class ChatService
             Agent = agent,
             Session = session,
             Review = reviewContext,
-            Finalizer = finalizerContext
+            Finalizer = finalizerContext,
+            PlanMode = planMode
         };
     }
 
diff --git a/Services/DatabaseService.cs b/Services/DatabaseService.cs
index 890f628..cff2cec 100644
--- a/Services/DatabaseService.cs
+++ b/Services/DatabaseService.cs
@@ -179,6 +179,7 @@ public class DatabaseService
         TryAddColumn(conn, "agents", "avatar_offset_y", "REAL NOT NULL DEFAULT 0");
         TryAddColumn(conn, "sessions", "finalizer_agent_id", "TEXT");
         TryAddColumn(conn, "agents", "allow_user_choice", "INTEGER NOT NULL DEFAULT 1");
+        TryAddColumn(conn, "chains", "plan_mode", "INTEGER NOT NULL DEFAULT 0");
 
         conn.Execute(@"
             CREATE TABLE IF NOT EXISTS agent_skills (
@@ -579,8 +580,8 @@ public class DatabaseService
         using var conn = CreateConnection();
         chain.CreatedAt = DateTime.UtcNow.ToString("o");
         await conn.ExecuteAsync(@"
-            INSERT INTO chains (chain_id, session_id, archive_id, agent_id, model, system_prompt, tool_choice, tool_names, input_tokens, output_tokens, iterations, stop_reason, duration_ms, created_at)
-            VALUES (@ChainId, @SessionId, @ArchiveId, @AgentId, @Model, @SystemPrompt, @ToolChoice, @ToolNames, @InputTokens, @OutputTokens, @Iterations, @StopReason, @DurationMs, @CreatedAt)
+            INSERT INTO chains (chain_id, session_id, archive_id, agent_id, model, system_prompt, tool_choice, tool_names, input_tokens, output_tokens, iterations, stop_reason, duration_ms, plan_mode, created_at)
+            VALUES (@ChainId, @SessionId, @ArchiveId, @AgentId, @Model, @SystemPrompt, @ToolChoice, @ToolNames, @InputTokens, @OutputTokens, @Iterations, @StopReason, @DurationMs, @PlanMode, @CreatedAt)
         ", chain);
     }
 
diff --git a/Services/ToolService.cs b/Services/ToolService.cs
index e138d53..6b17029 100644
--- a/Services/ToolService.cs
+++ b/Services/ToolService.cs
@@ -17,6 +17,34 @@ public class ToolService
 {
     public const string AskUserChoiceToolName = "ask_user_choice";
 
+    /// <summary>
+    /// Read-only Tools die im Plan-Modus verfügbar bleiben.
+    /// Write-Tools (write_file, edit_file, delete_file, execute) werden entfernt.
+    /// </summary>
+    private static readonly HashSet<string> ReadOnlyToolNames = new HashSet<string>
+    {
+        "read_file", "list_files", "glob", "grep", "todo_write",
+        "memory_read", "memory_write", "memory_list",
+        AskUserChoiceToolName
+    };
+
+    public object[] FilterReadOnlyTools(object[] tools)
+    {
+        var filtered = new List<object>();
+        foreach (var tool in tools)
+        {
+            var json = JsonSerializer.Serialize(tool);
+            var el = JsonSerializer.Deserialize<JsonElement>(json);
+            if (el.TryGetProperty("name", out var nameProp))
+            {
+                var name = nameProp.GetString() ?? "";
+                if (ReadOnlyToolNames.Contains(name))
+                    filtered.Add(tool);
+            }
+        }
+        return filtered.ToArray();
+    }
+
     public object[] GetToolDefinitions(bool includeFileTools = false, bool includeMemory = false, bool includeUserChoice = true)
     {
         var allTools = new List<object>();
diff --git a/wwwroot/css/chat.css b/wwwroot/css/chat.css
index 5269afa..41dfa2b 100644
--- a/wwwroot/css/chat.css
+++ b/wwwroot/css/chat.css
@@ -378,6 +378,13 @@
   color: var(--dangerous);
 }
 
+/* Plan Mode Toggle */
+#planModeBtn.plan-mode-active {
+  color: var(--primary);
+  background: color-mix(in srgb, var(--primary) 15%, transparent);
+  border-radius: var(--border-radius);
+}
+
 /* Emoji Picker */
 
 .emoji-picker {
diff --git a/wwwroot/index.html b/wwwroot/index.html
index 8753801..ef5e69d 100644
--- a/wwwroot/index.html
+++ b/wwwroot/index.html
@@ -322,6 +322,7 @@
         <input type="file" id="fileInput" accept="image/jpeg,image/png,image/gif,image/webp,application/pdf" multiple hidden>
         <button id="fileBtn" class="icon-btn" title="Datei anhängen"><i class="fa fa-paperclip"></i></button>
         <button id="explorerBtn" class="icon-btn" title="Workspace durchsuchen"><i class="fa fa-folder"></i></button>
+        <button id="planModeBtn" class="icon-btn" title="Plan-Modus umschalten"><i class="fa fa-map"></i></button>
         <textarea id="input" placeholder="Nachricht..." rows="1"></textarea>
         <button id="emojiBtn" class="icon-btn" title="Emoji einfügen"><i class="fa fa-smile-o"></i></button>
         <button id="send" class="icon-btn"><i class="fa fa-paper-plane"></i></button>
diff --git a/wwwroot/js/api.js b/wwwroot/js/api.js
index 437b242..6c82ed0 100644
--- a/wwwroot/js/api.js
+++ b/wwwroot/js/api.js
@@ -41,11 +41,13 @@ async function apiMe() {
 
 // ── API Calls ──
 
-async function apiChat(content, sessionId, signal) {
+async function apiChat(content, sessionId, signal, planMode) {
+  var payload = { content, sessionId };
+  if (planMode) payload.planMode = true;
   return fetch('/api/chat', {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
-    body: JSON.stringify({ content, sessionId }),
+    body: JSON.stringify(payload),
     signal
   });
 }
diff --git a/wwwroot/js/chat.js b/wwwroot/js/chat.js
index e6a9764..1f5a01b 100644
--- a/wwwroot/js/chat.js
+++ b/wwwroot/js/chat.js
@@ -2,6 +2,7 @@
 
 function buildMetaBadges(d) {
   const badges = [];
+  if (d.planMode) badges.push('📋 Plan-Modus');
   badges.push(prettyModelName(d.model));
   badges.push('Tokens: ' + (d.inputTokens || 0) + ' / ' + (d.outputTokens || 0));
   if (d.cacheCreationTokens > 0 || d.cacheReadTokens > 0) {
@@ -137,6 +138,23 @@ function handleStreamEvent(eventType, data) {
   }
 }
 
+// ── Plan Mode ──
+
+let _planModeActive = false;
+
+function togglePlanMode() {
+  _planModeActive = !_planModeActive;
+  var btn = $('#planModeBtn');
+  if (btn) {
+    btn.classList.toggle('plan-mode-active', _planModeActive);
+    btn.title = _planModeActive ? 'Plan-Modus deaktivieren' : 'Plan-Modus aktivieren';
+  }
+  var input = $('#input');
+  if (input) {
+    input.placeholder = _planModeActive ? 'Plannen...' : 'Nachricht...';
+  }
+}
+
 // ── Chat State ──
 
 let isStreaming = false;
@@ -254,7 +272,7 @@ async function sendMessage() {
   _chatAbandoned = false;
 
   try {
-    const resp = await apiChat(content, getCurrentSessionId(), _abortController.signal);
+    const resp = await apiChat(content, getCurrentSessionId(), _abortController.signal, _planModeActive);
     const reader = resp.body.getReader();
     const decoder = new TextDecoder();
     let buffer = '';
diff --git a/wwwroot/js/pages/chat-page.js b/wwwroot/js/pages/chat-page.js
index 5f73be7..65b26a0 100644
--- a/wwwroot/js/pages/chat-page.js
+++ b/wwwroot/js/pages/chat-page.js
@@ -304,6 +304,15 @@ registerPage('chat', {
       });
     }
 
+    // Plan Mode Toggle
+    const planModeBtn = document.getElementById('planModeBtn');
+    if (planModeBtn) {
+      // Plan-Modus bei Session-Wechsel zurücksetzen
+      _planModeActive = false;
+      planModeBtn.classList.remove('plan-mode-active');
+      planModeBtn.addEventListener('click', togglePlanMode);
+    }
+
     // File Upload
     const fileBtn = document.getElementById('fileBtn');
     const fileInput = document.getElementById('fileInput');