diff --git a/server/api/claude.js b/server/api/claude.js
index 1cd5b93..cdc6d95 100644
--- a/server/api/claude.js
+++ b/server/api/claude.js
@@ -1,8 +1,26 @@
 import { Router } from "express";
+import { getSession, addMessage, getConversationForAPI } from "../services/sessionStore.js";
 
 const router = Router();
 const ANTHROPIC_API_URL = "https://api.anthropic.com";
 
+/**
+ * Build entity context string for the system prompt
+ */
+function buildEntityContext(entities) {
+  if (!entities || entities.length === 0) {
+    return "\n\nThe diagram is currently empty.";
+  }
+
+  const entityList = entities.map(e => {
+    const shape = e.template?.replace('#', '').replace('-template', '') || 'unknown';
+    const pos = e.position || { x: 0, y: 0, z: 0 };
+    return `- ${e.text || '(no label)'} (${shape}, ${e.color || 'unknown'}) at (${pos.x?.toFixed(1)}, ${pos.y?.toFixed(1)}, ${pos.z?.toFixed(1)})`;
+  }).join('\n');
+
+  return `\n\n## Current Diagram State\nThe diagram currently contains ${entities.length} entities:\n${entityList}`;
+}
+
 // Express 5 uses named parameters for wildcards
 router.post("/*path", async (req, res) => {
   const apiKey = process.env.ANTHROPIC_API_KEY;
@@ -16,6 +34,36 @@ router.post("/*path", async (req, res) => {
   const pathParam = req.params.path;
   const path = "/" + (Array.isArray(pathParam) ? pathParam.join("/") : pathParam || "");
 
+  // Check for session-based request
+  const { sessionId, ...requestBody } = req.body;
+  let modifiedBody = requestBody;
+
+  if (sessionId) {
+    const session = getSession(sessionId);
+    if (session) {
+      console.log(`[Claude API] Session ${sessionId}: ${session.entities.length} entities, ${session.conversationHistory.length} messages in history`);
+
+      // Inject entity context into system prompt
+      if (modifiedBody.system) {
+        const entityContext = buildEntityContext(session.entities);
+        console.log(`[Claude API] Entity context:`, entityContext);
+        modifiedBody.system += entityContext;
+      }
+
+      // Get conversation history and merge with current messages
+      const historyMessages = getConversationForAPI(sessionId);
+      if (historyMessages.length > 0 && modifiedBody.messages) {
+        // Filter out any duplicate messages (in case client sent history too)
+        const currentContent = modifiedBody.messages[modifiedBody.messages.length - 1]?.content;
+        const filteredHistory = historyMessages.filter(msg => msg.content !== currentContent);
+        modifiedBody.messages = [...filteredHistory, ...modifiedBody.messages];
+        console.log(`[Claude API] Merged ${filteredHistory.length} history messages with ${modifiedBody.messages.length - filteredHistory.length} new messages`);
+      }
+    } else {
+      console.log(`[Claude API] Session ${sessionId} not found`);
+    }
+  }
+
   try {
     const response = await fetch(`${ANTHROPIC_API_URL}${path}`, {
       method: "POST",
@@ -24,10 +72,39 @@ router.post("/*path", async (req, res) => {
         "x-api-key": apiKey,
         "anthropic-version": "2023-06-01",
       },
-      body: JSON.stringify(req.body),
+      body: JSON.stringify(modifiedBody),
     });
 
     const data = await response.json();
+
+    // If session exists and response is successful, store messages
+    if (sessionId && response.ok && data.content) {
+      const session = getSession(sessionId);
+      if (session) {
+        // Store the user message if it was new (only if it's a string, not tool results)
+        const userMessage = requestBody.messages?.[requestBody.messages.length - 1];
+        if (userMessage && userMessage.role === 'user' && typeof userMessage.content === 'string') {
+          addMessage(sessionId, {
+            role: 'user',
+            content: userMessage.content
+          });
+        }
+
+        // Store the assistant response (text only, not tool use blocks)
+        const assistantContent = data.content
+          .filter(c => c.type === 'text')
+          .map(c => c.text)
+          .join('\n');
+
+        if (assistantContent) {
+          addMessage(sessionId, {
+            role: 'assistant',
+            content: assistantContent
+          });
+        }
+      }
+    }
+
     res.status(response.status).json(data);
   } catch (error) {
     console.error("Claude API error:", error.message);
diff --git a/server/api/index.js b/server/api/index.js
index 70321ff..56faff4 100644
--- a/server/api/index.js
+++ b/server/api/index.js
@@ -1,8 +1,12 @@
 import { Router } from "express";
 import claudeRouter from "./claude.js";
+import sessionRouter from "./session.js";
 
 const router = Router();
 
+// Session management
+router.use("/session", sessionRouter);
+
 // Claude API proxy
 router.use("/claude", claudeRouter);
 
diff --git a/server/api/session.js b/server/api/session.js
new file mode 100644
index 0000000..20e738a
--- /dev/null
+++ b/server/api/session.js
@@ -0,0 +1,144 @@
+import { Router } from "express";
+import {
+  createSession,
+  getSession,
+  findSessionByDiagram,
+  syncEntities,
+  addMessage,
+  clearHistory,
+  deleteSession,
+  getStats
+} from "../services/sessionStore.js";
+
+const router = Router();
+
+/**
+ * GET /api/session/debug/stats
+ * Get session statistics (for debugging)
+ * Query params:
+ *   - details=true: Include full entity and conversation data
+ * NOTE: Must be before /:id routes to avoid matching "debug" as an id
+ */
+router.get("/debug/stats", (req, res) => {
+  const includeDetails = req.query.details === 'true';
+  const stats = getStats(includeDetails);
+  console.log('[Session Debug] Stats requested:', JSON.stringify(stats, null, 2));
+  res.json(stats);
+});
+
+/**
+ * POST /api/session/create
+ * Create a new session or return existing one for a diagram
+ */
+router.post("/create", (req, res) => {
+  const { diagramId } = req.body;
+
+  if (!diagramId) {
+    return res.status(400).json({ error: "diagramId is required" });
+  }
+
+  // Check for existing session
+  let session = findSessionByDiagram(diagramId);
+  if (session) {
+    console.log(`[Session] Resuming existing session ${session.id} for diagram ${diagramId} (${session.conversationHistory.length} messages, ${session.entities.length} entities)`);
+    return res.json({
+      session,
+      isNew: false
+    });
+  }
+
+  // Create new session
+  session = createSession(diagramId);
+  console.log(`[Session] Created new session ${session.id} for diagram ${diagramId}`);
+  res.json({
+    session,
+    isNew: true
+  });
+});
+
+/**
+ * GET /api/session/:id
+ * Get session details including history
+ */
+router.get("/:id", (req, res) => {
+  const session = getSession(req.params.id);
+
+  if (!session) {
+    return res.status(404).json({ error: "Session not found" });
+  }
+
+  res.json({ session });
+});
+
+/**
+ * PUT /api/session/:id/sync
+ * Sync entities from client to server
+ */
+router.put("/:id/sync", (req, res) => {
+  const { entities } = req.body;
+
+  if (!entities || !Array.isArray(entities)) {
+    return res.status(400).json({ error: "entities array is required" });
+  }
+
+  const session = syncEntities(req.params.id, entities);
+
+  if (!session) {
+    return res.status(404).json({ error: "Session not found" });
+  }
+
+  console.log(`[Session ${req.params.id}] Synced ${entities.length} entities:`,
+    entities.map(e => `${e.text || '(no label)'} (${e.template})`).join(', ') || 'none');
+
+  res.json({ success: true, entityCount: entities.length });
+});
+
+/**
+ * POST /api/session/:id/message
+ * Add a message to history (used after successful Claude response)
+ */
+router.post("/:id/message", (req, res) => {
+  const { role, content, toolResults } = req.body;
+
+  if (!role || !content) {
+    return res.status(400).json({ error: "role and content are required" });
+  }
+
+  const session = addMessage(req.params.id, { role, content, toolResults });
+
+  if (!session) {
+    return res.status(404).json({ error: "Session not found" });
+  }
+
+  res.json({ success: true, messageCount: session.conversationHistory.length });
+});
+
+/**
+ * DELETE /api/session/:id/history
+ * Clear conversation history
+ */
+router.delete("/:id/history", (req, res) => {
+  const session = clearHistory(req.params.id);
+
+  if (!session) {
+    return res.status(404).json({ error: "Session not found" });
+  }
+
+  res.json({ success: true });
+});
+
+/**
+ * DELETE /api/session/:id
+ * Delete a session entirely
+ */
+router.delete("/:id", (req, res) => {
+  const deleted = deleteSession(req.params.id);
+
+  if (!deleted) {
+    return res.status(404).json({ error: "Session not found" });
+  }
+
+  res.json({ success: true });
+});
+
+export default router;
diff --git a/server/services/sessionStore.js b/server/services/sessionStore.js
new file mode 100644
index 0000000..c997efb
--- /dev/null
+++ b/server/services/sessionStore.js
@@ -0,0 +1,158 @@
+/**
+ * In-memory session store for diagram chat sessions.
+ * Stores conversation history and entity snapshots.
+ */
+
+import { v4 as uuidv4 } from 'uuid';
+
+// Session structure:
+// {
+//   id: string,
+//   diagramId: string,
+//   conversationHistory: Array<{role, content, toolResults?, timestamp}>,
+//   entities: Array<{id, template, text, color, position}>,
+//   createdAt: Date,
+//   lastAccess: Date
+// }
+
+const sessions = new Map();
+
+// Session timeout (1 hour of inactivity)
+const SESSION_TIMEOUT_MS = 60 * 60 * 1000;
+
+/**
+ * Create a new session for a diagram
+ */
+export function createSession(diagramId) {
+  const id = uuidv4();
+  const session = {
+    id,
+    diagramId,
+    conversationHistory: [],
+    entities: [],
+    createdAt: new Date(),
+    lastAccess: new Date()
+  };
+  sessions.set(id, session);
+  return session;
+}
+
+/**
+ * Get a session by ID
+ */
+export function getSession(sessionId) {
+  const session = sessions.get(sessionId);
+  if (session) {
+    session.lastAccess = new Date();
+  }
+  return session || null;
+}
+
+/**
+ * Find existing session for a diagram
+ */
+export function findSessionByDiagram(diagramId) {
+  for (const [, session] of sessions) {
+    if (session.diagramId === diagramId) {
+      session.lastAccess = new Date();
+      return session;
+    }
+  }
+  return null;
+}
+
+/**
+ * Update entities snapshot for a session
+ */
+export function syncEntities(sessionId, entities) {
+  const session = sessions.get(sessionId);
+  if (!session) return null;
+
+  session.entities = entities;
+  session.lastAccess = new Date();
+  return session;
+}
+
+/**
+ * Add a message to conversation history
+ */
+export function addMessage(sessionId, message) {
+  const session = sessions.get(sessionId);
+  if (!session) return null;
+
+  session.conversationHistory.push({
+    ...message,
+    timestamp: new Date()
+  });
+  session.lastAccess = new Date();
+  return session;
+}
+
+/**
+ * Get conversation history for API calls (formatted for Claude)
+ */
+export function getConversationForAPI(sessionId) {
+  const session = sessions.get(sessionId);
+  if (!session) return [];
+
+  // Convert to Claude message format
+  return session.conversationHistory.map(msg => ({
+    role: msg.role,
+    content: msg.content
+  }));
+}
+
+/**
+ * Clear conversation history but keep session
+ */
+export function clearHistory(sessionId) {
+  const session = sessions.get(sessionId);
+  if (!session) return null;
+
+  session.conversationHistory = [];
+  session.lastAccess = new Date();
+  return session;
+}
+
+/**
+ * Delete a session
+ */
+export function deleteSession(sessionId) {
+  return sessions.delete(sessionId);
+}
+
+/**
+ * Clean up expired sessions
+ */
+export function cleanupExpiredSessions() {
+  const now = Date.now();
+  for (const [id, session] of sessions) {
+    if (now - session.lastAccess.getTime() > SESSION_TIMEOUT_MS) {
+      sessions.delete(id);
+    }
+  }
+}
+
+// Run cleanup every 15 minutes
+setInterval(cleanupExpiredSessions, 15 * 60 * 1000);
+
+/**
+ * Get session stats (for debugging)
+ */
+export function getStats(includeDetails = false) {
+  return {
+    activeSessions: sessions.size,
+    sessions: Array.from(sessions.values()).map(s => ({
+      id: s.id,
+      diagramId: s.diagramId,
+      messageCount: s.conversationHistory.length,
+      entityCount: s.entities.length,
+      lastAccess: s.lastAccess,
+      // Include full details if requested
+      ...(includeDetails && {
+        entities: s.entities,
+        conversationHistory: s.conversationHistory
+      })
+    }))
+  };
+}
diff --git a/src/diagram/diagramManager.ts b/src/diagram/diagramManager.ts
index a2e10ea..a2f5f75 100644
--- a/src/diagram/diagramManager.ts
+++ b/src/diagram/diagramManager.ts
@@ -13,6 +13,7 @@ import {UserModelType} from "../users/userTypes";
 import {vectoxys} from "./functions/vectorConversion";
 import {controllerObservable} from "../controllers/controllers";
 import {ControllerEvent} from "../controllers/types/controllerEvent";
+import {HEX_TO_COLOR_NAME, TEMPLATE_TO_SHAPE} from "../react/types/chatTypes";
 
 
 export class DiagramManager {
@@ -107,6 +108,13 @@ export class DiagramManager {
         document.addEventListener('chatCreateEntity', (event: CustomEvent) => {
             const {entity} = event.detail;
             this._logger.debug('chatCreateEntity', entity);
+
+            // Generate a default label if none is provided
+            if (!entity.text) {
+                entity.text = this.generateDefaultLabel(entity);
+                this._logger.debug('Generated default label:', entity.text);
+            }
+
             const object = new DiagramObject(this._scene, this.onDiagramEventObservable, {
                 diagramEntity: entity,
                 actionManager: this._diagramEntityActionManager
@@ -161,6 +169,7 @@ export class DiagramManager {
                 id: obj.diagramEntity.id,
                 template: obj.diagramEntity.template,
                 text: obj.diagramEntity.text || '',
+                color: obj.diagramEntity.color,
                 position: obj.diagramEntity.position
             }));
             const responseEvent = new CustomEvent('chatListEntitiesResponse', {
@@ -219,6 +228,42 @@ export class DiagramManager {
         return null;
     }
 
+    /**
+     * Generates a default label for an entity based on its color and shape.
+     * Format: "{color} {shape} {number}" e.g., "blue box 1", "red sphere 2"
+     * The number is determined by counting existing entities with the same prefix.
+     */
+    private generateDefaultLabel(entity: DiagramEntity): string {
+        // Get color name from hex
+        const colorHex = entity.color?.toLowerCase() || '#0000ff';
+        const colorName = HEX_TO_COLOR_NAME[colorHex] || 'blue';
+
+        // Get shape name from template
+        const shapeName = TEMPLATE_TO_SHAPE[entity.template] || 'box';
+
+        // Create the prefix (e.g., "blue box")
+        const prefix = `${colorName} ${shapeName}`;
+
+        // Count existing entities with labels starting with this prefix
+        let maxNumber = 0;
+        for (const [, obj] of this._diagramObjects) {
+            const label = obj.diagramEntity.text?.toLowerCase() || '';
+            if (label.startsWith(prefix)) {
+                // Extract the number from the end of the label
+                const match = label.match(new RegExp(`^${prefix}\\s*(\\d+)$`));
+                if (match) {
+                    const num = parseInt(match[1], 10);
+                    if (num > maxNumber) {
+                        maxNumber = num;
+                    }
+                }
+            }
+        }
+
+        // Return the next number in sequence
+        return `${prefix} ${maxNumber + 1}`;
+    }
+
     private onDiagramEvent(event: DiagramEvent) {
         let diagramObject = this._diagramObjects.get(event?.entity?.id);
         switch (event.type) {
diff --git a/src/react/components/ChatPanel.tsx b/src/react/components/ChatPanel.tsx
index ed8d401..a10fd30 100644
--- a/src/react/components/ChatPanel.tsx
+++ b/src/react/components/ChatPanel.tsx
@@ -2,9 +2,19 @@ import React, {useEffect, useRef, useState} from "react";
 import {ActionIcon, Alert, Box, CloseButton, Group, Paper, ScrollArea, Text, Textarea} from "@mantine/core";
 import {IconAlertCircle, IconRobot, IconSend} from "@tabler/icons-react";
 import ChatMessage from "./ChatMessage";
-import {ChatMessage as ChatMessageType, ToolResult} from "../types/chatTypes";
-import {createAssistantMessage, createLoadingMessage, createUserMessage, sendMessage} from "../services/diagramAI";
+import {ChatMessage as ChatMessageType, SessionMessage, ToolResult} from "../types/chatTypes";
+import {
+    createAssistantMessage,
+    createLoadingMessage,
+    createOrResumeSession,
+    createUserMessage,
+    sendMessage,
+    syncEntitiesToSession
+} from "../services/diagramAI";
+import {getEntitiesForSync} from "../services/entityBridge";
+import {getPath} from "../../util/functions/getPath";
 import log from "loglevel";
+import {v4 as uuidv4} from 'uuid';
 
 const logger = log.getLogger('ChatPanel');
 
@@ -13,16 +23,79 @@ interface ChatPanelProps {
     onClose?: () => void;
 }
 
+const WELCOME_MESSAGE = "Hello! I can help you create and modify 3D diagrams. Try saying things like:\n\n• \"Add a blue box labeled 'Server'\"\n• \"Create a red sphere called 'Database'\"\n• \"Connect Server to Database\"\n• \"What's in my diagram?\"\n\nHow can I help you today?";
+
+/**
+ * Convert session messages to ChatMessage format
+ */
+function sessionMessageToChatMessage(msg: SessionMessage): ChatMessageType | null {
+    // Skip messages with non-string content (e.g., tool result objects)
+    if (typeof msg.content !== 'string') {
+        return null;
+    }
+    return {
+        id: uuidv4(),
+        role: msg.role,
+        content: msg.content,
+        timestamp: new Date(msg.timestamp),
+        toolResults: msg.toolResults
+    };
+}
+
 export default function ChatPanel({width = 400, onClose}: ChatPanelProps) {
-    const [messages, setMessages] = useState<ChatMessageType[]>([
-        createAssistantMessage("Hello! I can help you create and modify 3D diagrams. Try saying things like:\n\n• \"Add a blue box labeled 'Server'\"\n• \"Create a red sphere called 'Database'\"\n• \"Connect Server to Database\"\n• \"What's in my diagram?\"\n\nHow can I help you today?")
-    ]);
+    const [messages, setMessages] = useState<ChatMessageType[]>([]);
     const [inputValue, setInputValue] = useState('');
     const [isLoading, setIsLoading] = useState(false);
+    const [isInitializing, setIsInitializing] = useState(true);
     const [error, setError] = useState<string | null>(null);
     const scrollAreaRef = useRef<HTMLDivElement>(null);
     const textareaRef = useRef<HTMLTextAreaElement>(null);
 
+    // Initialize or resume session on mount
+    useEffect(() => {
+        const initSession = async () => {
+            const diagramId = getPath() || 'default';
+            logger.info('Initializing session for diagram:', diagramId);
+
+            try {
+                // Create or resume session
+                const {session, isNew} = await createOrResumeSession(diagramId);
+                logger.info(`Session ${isNew ? 'created' : 'resumed'}:`, session.id);
+
+                // Sync current entities to server
+                const entities = await getEntitiesForSync();
+                if (entities.length > 0) {
+                    await syncEntitiesToSession(entities);
+                    logger.info('Synced', entities.length, 'entities to session');
+                }
+
+                // Restore conversation history or show welcome message
+                if (!isNew && session.conversationHistory && session.conversationHistory.length > 0) {
+                    const restoredMessages = session.conversationHistory
+                        .map(sessionMessageToChatMessage)
+                        .filter((msg): msg is ChatMessageType => msg !== null);
+                    if (restoredMessages.length > 0) {
+                        setMessages(restoredMessages);
+                        logger.info('Restored', restoredMessages.length, 'messages from session');
+                    } else {
+                        setMessages([createAssistantMessage(WELCOME_MESSAGE)]);
+                    }
+                } else {
+                    setMessages([createAssistantMessage(WELCOME_MESSAGE)]);
+                }
+            } catch (err) {
+                logger.error('Failed to initialize session:', err);
+                // Fall back to welcome message
+                setMessages([createAssistantMessage(WELCOME_MESSAGE)]);
+            } finally {
+                setIsInitializing(false);
+            }
+        };
+
+        initSession();
+    }, []);
+
+    // Auto-scroll when messages change
     useEffect(() => {
         if (scrollAreaRef.current) {
             scrollAreaRef.current.scrollTo({
@@ -46,6 +119,13 @@ export default function ChatPanel({width = 400, onClose}: ChatPanelProps) {
         setMessages(prev => [...prev, loadingMessage]);
 
         try {
+            // Sync current entities before sending message so Claude has latest state
+            const entities = await getEntitiesForSync();
+            if (entities.length > 0) {
+                await syncEntitiesToSession(entities);
+                logger.debug('Synced', entities.length, 'entities before message');
+            }
+
             const allToolResults: ToolResult[] = [];
 
             const {response, toolResults} = await sendMessage(
@@ -141,22 +221,22 @@ export default function ChatPanel({width = 400, onClose}: ChatPanelProps) {
                 <Group gap="xs" align="flex-end">
                     <Textarea
                         ref={textareaRef}
-                        placeholder="Describe what you want to create..."
+                        placeholder={isInitializing ? "Connecting..." : "Describe what you want to create..."}
                         value={inputValue}
                         onChange={(e) => setInputValue(e.currentTarget.value)}
                         onKeyDown={handleKeyDown}
                         autosize
                         minRows={1}
                         maxRows={4}
-                        disabled={isLoading}
+                        disabled={isLoading || isInitializing}
                         style={{flex: 1}}
                     />
                     <ActionIcon
                         size="lg"
                         variant="filled"
                         onClick={handleSend}
-                        disabled={!inputValue.trim() || isLoading}
-                        loading={isLoading}
+                        disabled={!inputValue.trim() || isLoading || isInitializing}
+                        loading={isLoading || isInitializing}
                     >
                         <IconSend size={18}/>
                     </ActionIcon>
diff --git a/src/react/services/diagramAI.ts b/src/react/services/diagramAI.ts
index 984496e..e2fe47a 100644
--- a/src/react/services/diagramAI.ts
+++ b/src/react/services/diagramAI.ts
@@ -1,7 +1,86 @@
-import {ChatMessage, DiagramToolCall, ToolResult} from "../types/chatTypes";
+import {ChatMessage, CreateSessionResponse, DiagramSession, DiagramToolCall, SessionEntity, SyncEntitiesResponse, ToolResult} from "../types/chatTypes";
 import {connectEntities, createEntity, listEntities, modifyEntity, removeEntity} from "./entityBridge";
 import {v4 as uuidv4} from 'uuid';
 
+// Session management
+let currentSessionId: string | null = null;
+
+/**
+ * Create a new session or resume existing one for a diagram
+ */
+export async function createOrResumeSession(diagramId: string): Promise<{ session: DiagramSession; isNew: boolean }> {
+    const response = await fetch('/api/session/create', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ diagramId })
+    });
+
+    if (!response.ok) {
+        throw new Error(`Failed to create session: ${response.status}`);
+    }
+
+    const data: CreateSessionResponse = await response.json();
+    currentSessionId = data.session.id;
+    return data;
+}
+
+/**
+ * Get current session ID
+ */
+export function getCurrentSessionId(): string | null {
+    return currentSessionId;
+}
+
+/**
+ * Sync entities to the current session
+ */
+export async function syncEntitiesToSession(entities: SessionEntity[]): Promise<void> {
+    if (!currentSessionId) {
+        console.warn('No active session to sync entities to');
+        return;
+    }
+
+    const response = await fetch(`/api/session/${currentSessionId}/sync`, {
+        method: 'PUT',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ entities })
+    });
+
+    if (!response.ok) {
+        console.error('Failed to sync entities:', response.status);
+    }
+}
+
+/**
+ * Get session with conversation history
+ */
+export async function getSessionHistory(): Promise<DiagramSession | null> {
+    if (!currentSessionId) {
+        return null;
+    }
+
+    const response = await fetch(`/api/session/${currentSessionId}`);
+    if (!response.ok) {
+        return null;
+    }
+
+    const data = await response.json();
+    return data.session;
+}
+
+/**
+ * Clear session history
+ */
+export async function clearSessionHistory(): Promise<void> {
+    if (!currentSessionId) {
+        return;
+    }
+
+    await fetch(`/api/session/${currentSessionId}/history`, {
+        method: 'DELETE'
+    });
+}
+
 const SYSTEM_PROMPT = `You are a 3D diagram assistant helping users create and modify diagrams in a virtual reality environment.
 
 Available entity shapes: box, sphere, cylinder, cone, plane, person
@@ -174,14 +253,20 @@ export async function sendMessage(
     conversationHistory: ChatMessage[],
     onToolResult?: (result: ToolResult) => void
 ): Promise<{ response: string; toolResults: ToolResult[] }> {
-    const messages: ClaudeMessage[] = conversationHistory
-        .filter(m => !m.isLoading)
-        .map(m => ({
-            role: m.role,
-            content: m.content
-        }));
+    // When using sessions, we don't need to send full history - server manages it
+    // Just send the new message
+    const messages: ClaudeMessage[] = currentSessionId
+        ? [{ role: 'user', content: userMessage }]
+        : conversationHistory
+            .filter(m => !m.isLoading)
+            .map(m => ({
+                role: m.role,
+                content: m.content
+            }));
 
-    messages.push({role: 'user', content: userMessage});
+    if (!currentSessionId) {
+        messages.push({role: 'user', content: userMessage});
+    }
 
     const allToolResults: ToolResult[] = [];
     let finalResponse = '';
@@ -198,7 +283,9 @@ export async function sendMessage(
                 max_tokens: 1024,
                 system: SYSTEM_PROMPT,
                 tools: TOOLS,
-                messages
+                messages,
+                // Include sessionId if we have an active session
+                ...(currentSessionId && { sessionId: currentSessionId })
             })
         });
 
diff --git a/src/react/services/entityBridge.ts b/src/react/services/entityBridge.ts
index 1c3eb7c..d11d482 100644
--- a/src/react/services/entityBridge.ts
+++ b/src/react/services/entityBridge.ts
@@ -167,3 +167,31 @@ export function listEntities(): Promise<ToolResult> {
         }, 5000);
     });
 }
+
+/**
+ * Get all entities for session syncing (returns raw entity data)
+ */
+export function getEntitiesForSync(): Promise<Array<{
+    id: string;
+    template: string;
+    text?: string;
+    color?: string;
+    position?: { x: number; y: number; z: number };
+}>> {
+    return new Promise((resolve) => {
+        const responseHandler = (e: CustomEvent) => {
+            document.removeEventListener('chatListEntitiesResponse', responseHandler as EventListener);
+            resolve(e.detail.entities || []);
+        };
+
+        document.addEventListener('chatListEntitiesResponse', responseHandler as EventListener);
+
+        const event = new CustomEvent('chatListEntities', {bubbles: true});
+        document.dispatchEvent(event);
+
+        setTimeout(() => {
+            document.removeEventListener('chatListEntitiesResponse', responseHandler as EventListener);
+            resolve([]);
+        }, 5000);
+    });
+}
diff --git a/src/react/types/chatTypes.ts b/src/react/types/chatTypes.ts
index 42565b8..f10b1d1 100644
--- a/src/react/types/chatTypes.ts
+++ b/src/react/types/chatTypes.ts
@@ -73,3 +73,55 @@ export const COLOR_NAME_TO_HEX: Record<string, string> = {
     gray: '#778899',
     grey: '#778899',
 };
+
+// Reverse mapping from hex to color name
+export const HEX_TO_COLOR_NAME: Record<string, string> = Object.entries(COLOR_NAME_TO_HEX)
+    .reduce((acc, [name, hex]) => {
+        acc[hex.toLowerCase()] = name;
+        return acc;
+    }, {} as Record<string, string>);
+
+// Template to shape name mapping
+export const TEMPLATE_TO_SHAPE: Record<string, string> = {
+    '#box-template': 'box',
+    '#sphere-template': 'sphere',
+    '#cylinder-template': 'cylinder',
+    '#cone-template': 'cone',
+    '#plane-template': 'plane',
+    '#person-template': 'person',
+};
+
+// Session types
+export interface SessionEntity {
+    id: string;
+    template: string;
+    text?: string;
+    color?: string;
+    position?: { x: number; y: number; z: number };
+}
+
+export interface SessionMessage {
+    role: ChatRole;
+    content: string;
+    toolResults?: ToolResult[];
+    timestamp: Date;
+}
+
+export interface DiagramSession {
+    id: string;
+    diagramId: string;
+    conversationHistory: SessionMessage[];
+    entities: SessionEntity[];
+    createdAt: Date;
+    lastAccess: Date;
+}
+
+export interface CreateSessionResponse {
+    session: DiagramSession;
+    isNew: boolean;
+}
+
+export interface SyncEntitiesResponse {
+    success: boolean;
+    entityCount: number;
+}