diff --git a/src/dolibarr_mcp/dolibarr_client.py b/src/dolibarr_mcp/dolibarr_client.py
new file mode 100644
index 0000000..94496e9
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+++ b/src/dolibarr_mcp/dolibarr_client.py
@@ -0,0 +1,386 @@
+"""Professional Dolibarr API client with comprehensive CRUD operations."""
+
+import json
+import logging
+from typing import Any, Dict, List, Optional, Union
+from urllib.parse import urljoin, quote
+
+import aiohttp
+from aiohttp import ClientSession, ClientTimeout
+
+from .config import Config
+
+
+class DolibarrAPIError(Exception):
+    """Custom exception for Dolibarr API errors."""
+    
+    def __init__(self, message: str, status_code: Optional[int] = None, response_data: Optional[Dict] = None):
+        self.message = message
+        self.status_code = status_code
+        self.response_data = response_data
+        super().__init__(self.message)
+
+
+class DolibarrClient:
+    """Professional Dolibarr API client with comprehensive functionality."""
+    
+    def __init__(self, config: Config):
+        """Initialize the Dolibarr client."""
+        self.config = config
+        self.base_url = config.dolibarr_url.rstrip('/')
+        self.api_key = config.api_key
+        self.session: Optional[ClientSession] = None
+        self.logger = logging.getLogger(__name__)
+        
+        # Configure timeout
+        self.timeout = ClientTimeout(total=30, connect=10)
+    
+    async def __aenter__(self):
+        """Async context manager entry."""
+        await self.start_session()
+        return self
+    
+    async def __aexit__(self, exc_type, exc_val, exc_tb):
+        """Async context manager exit."""
+        await self.close_session()
+    
+    async def start_session(self):
+        """Start the HTTP session."""
+        if not self.session:
+            self.session = aiohttp.ClientSession(
+                timeout=self.timeout,
+                headers={
+                    "DOLAPIKEY": self.api_key,
+                    "Content-Type": "application/json",
+                    "Accept": "application/json"
+                }
+            )
+    
+    async def close_session(self):
+        """Close the HTTP session."""
+        if self.session:
+            await self.session.close()
+            self.session = None
+    
+    def _build_url(self, endpoint: str) -> str:
+        """Build full API URL."""
+        endpoint = endpoint.lstrip('/')
+        return f"{self.base_url}/{endpoint}"
+    
+    async def _make_request(
+        self, 
+        method: str, 
+        endpoint: str, 
+        params: Optional[Dict] = None,
+        data: Optional[Dict] = None
+    ) -> Dict[str, Any]:
+        """Make HTTP request to Dolibarr API."""
+        if not self.session:
+            await self.start_session()
+        
+        url = self._build_url(endpoint)
+        
+        try:
+            self.logger.debug(f"Making {method} request to {url}")
+            
+            kwargs = {
+                "params": params or {},
+            }
+            
+            if data and method.upper() in ["POST", "PUT"]:
+                kwargs["json"] = data
+            
+            async with self.session.request(method, url, **kwargs) as response:
+                response_text = await response.text()
+                
+                # Log response for debugging
+                self.logger.debug(f"Response status: {response.status}")
+                self.logger.debug(f"Response text: {response_text[:500]}...")
+                
+                # Try to parse JSON response
+                try:
+                    response_data = json.loads(response_text) if response_text else {}
+                except json.JSONDecodeError:
+                    response_data = {"raw_response": response_text}
+                
+                # Handle error responses
+                if response.status >= 400:
+                    error_msg = f"HTTP {response.status}: {response.reason}"
+                    if isinstance(response_data, dict) and "error" in response_data:
+                        error_msg = response_data["error"]
+                    elif isinstance(response_data, dict) and "message" in response_data:
+                        error_msg = response_data["message"]
+                    
+                    raise DolibarrAPIError(
+                        message=error_msg,
+                        status_code=response.status,
+                        response_data=response_data
+                    )
+                
+                return response_data
+                
+        except aiohttp.ClientError as e:
+            raise DolibarrAPIError(f"HTTP client error: {str(e)}")
+        except Exception as e:
+            if isinstance(e, DolibarrAPIError):
+                raise
+            raise DolibarrAPIError(f"Unexpected error: {str(e)}")
+    
+    # ============================================================================
+    # SYSTEM ENDPOINTS
+    # ============================================================================
+    
+    async def get_status(self) -> Dict[str, Any]:
+        """Get API status and version information."""
+        return await self._make_request("GET", "/status")
+    
+    # ============================================================================
+    # USER MANAGEMENT
+    # ============================================================================
+    
+    async def get_users(self, limit: int = 100, page: int = 1) -> List[Dict[str, Any]]:
+        """Get list of users."""
+        params = {"limit": limit}
+        if page > 1:
+            params["page"] = page
+        
+        result = await self._make_request("GET", "/users", params=params)
+        return result if isinstance(result, list) else []
+    
+    async def get_user_by_id(self, user_id: int) -> Dict[str, Any]:
+        """Get specific user by ID."""
+        return await self._make_request("GET", f"/users/{user_id}")
+    
+    async def create_user(self, **kwargs) -> Dict[str, Any]:
+        """Create a new user."""
+        return await self._make_request("POST", "/users", data=kwargs)
+    
+    async def update_user(self, user_id: int, **kwargs) -> Dict[str, Any]:
+        """Update an existing user."""
+        return await self._make_request("PUT", f"/users/{user_id}", data=kwargs)
+    
+    async def delete_user(self, user_id: int) -> Dict[str, Any]:
+        """Delete a user."""
+        return await self._make_request("DELETE", f"/users/{user_id}")
+    
+    # ============================================================================
+    # CUSTOMER/THIRD PARTY MANAGEMENT
+    # ============================================================================
+    
+    async def get_customers(self, limit: int = 100, page: int = 1) -> List[Dict[str, Any]]:
+        """Get list of customers/third parties."""
+        params = {"limit": limit}
+        if page > 1:
+            params["page"] = page
+        
+        result = await self._make_request("GET", "/thirdparties", params=params)
+        return result if isinstance(result, list) else []
+    
+    async def get_customer_by_id(self, customer_id: int) -> Dict[str, Any]:
+        """Get specific customer by ID."""
+        return await self._make_request("GET", f"/thirdparties/{customer_id}")
+    
+    async def create_customer(
+        self,
+        name: str,
+        email: Optional[str] = None,
+        phone: Optional[str] = None,
+        address: Optional[str] = None,
+        town: Optional[str] = None,
+        zip: Optional[str] = None,
+        country_id: int = 1,
+        type: int = 1,  # 1=Customer, 2=Supplier, 3=Both
+        status: int = 1,
+        **kwargs
+    ) -> Dict[str, Any]:
+        """Create a new customer/third party."""
+        data = {
+            "name": name,
+            "status": status,
+            "client": type if type in [1, 3] else 0,
+            "fournisseur": 1 if type in [2, 3] else 0,
+            "country_id": country_id,
+            **kwargs
+        }
+        
+        if email:
+            data["email"] = email
+        if phone:
+            data["phone"] = phone
+        if address:
+            data["address"] = address
+        if town:
+            data["town"] = town
+        if zip:
+            data["zip"] = zip
+        
+        return await self._make_request("POST", "/thirdparties", data=data)
+    
+    async def update_customer(self, customer_id: int, **kwargs) -> Dict[str, Any]:
+        """Update an existing customer."""
+        return await self._make_request("PUT", f"/thirdparties/{customer_id}", data=kwargs)
+    
+    async def delete_customer(self, customer_id: int) -> Dict[str, Any]:
+        """Delete a customer."""
+        return await self._make_request("DELETE", f"/thirdparties/{customer_id}")
+    
+    # ============================================================================
+    # PRODUCT MANAGEMENT
+    # ============================================================================
+    
+    async def get_products(self, limit: int = 100) -> List[Dict[str, Any]]:
+        """Get list of products."""
+        params = {"limit": limit}
+        result = await self._make_request("GET", "/products", params=params)
+        return result if isinstance(result, list) else []
+    
+    async def get_product_by_id(self, product_id: int) -> Dict[str, Any]:
+        """Get specific product by ID."""
+        return await self._make_request("GET", f"/products/{product_id}")
+    
+    async def create_product(
+        self,
+        label: str,
+        price: float,
+        description: Optional[str] = None,
+        stock: Optional[int] = None,
+        **kwargs
+    ) -> Dict[str, Any]:
+        """Create a new product."""
+        data = {
+            "label": label,
+            "price": price,
+            **kwargs
+        }
+        
+        if description:
+            data["description"] = description
+        if stock is not None:
+            data["stock"] = stock
+        
+        return await self._make_request("POST", "/products", data=data)
+    
+    async def update_product(self, product_id: int, **kwargs) -> Dict[str, Any]:
+        """Update an existing product."""
+        return await self._make_request("PUT", f"/products/{product_id}", data=kwargs)
+    
+    async def delete_product(self, product_id: int) -> Dict[str, Any]:
+        """Delete a product."""
+        return await self._make_request("DELETE", f"/products/{product_id}")
+    
+    # ============================================================================
+    # INVOICE MANAGEMENT
+    # ============================================================================
+    
+    async def get_invoices(self, limit: int = 100, status: Optional[str] = None) -> List[Dict[str, Any]]:
+        """Get list of invoices."""
+        params = {"limit": limit}
+        if status:
+            params["status"] = status
+        
+        result = await self._make_request("GET", "/invoices", params=params)
+        return result if isinstance(result, list) else []
+    
+    async def get_invoice_by_id(self, invoice_id: int) -> Dict[str, Any]:
+        """Get specific invoice by ID."""
+        return await self._make_request("GET", f"/invoices/{invoice_id}")
+    
+    async def create_invoice(
+        self,
+        customer_id: int,
+        lines: List[Dict[str, Any]],
+        date: Optional[str] = None,
+        due_date: Optional[str] = None,
+        **kwargs
+    ) -> Dict[str, Any]:
+        """Create a new invoice."""
+        data = {
+            "socid": customer_id,
+            "lines": lines,
+            **kwargs
+        }
+        
+        if date:
+            data["date"] = date
+        if due_date:
+            data["due_date"] = due_date
+        
+        return await self._make_request("POST", "/invoices", data=data)
+    
+    async def update_invoice(self, invoice_id: int, **kwargs) -> Dict[str, Any]:
+        """Update an existing invoice."""
+        return await self._make_request("PUT", f"/invoices/{invoice_id}", data=kwargs)
+    
+    async def delete_invoice(self, invoice_id: int) -> Dict[str, Any]:
+        """Delete an invoice."""
+        return await self._make_request("DELETE", f"/invoices/{invoice_id}")
+    
+    # ============================================================================
+    # ORDER MANAGEMENT
+    # ============================================================================
+    
+    async def get_orders(self, limit: int = 100, status: Optional[str] = None) -> List[Dict[str, Any]]:
+        """Get list of orders."""
+        params = {"limit": limit}
+        if status:
+            params["status"] = status
+        
+        result = await self._make_request("GET", "/orders", params=params)
+        return result if isinstance(result, list) else []
+    
+    async def get_order_by_id(self, order_id: int) -> Dict[str, Any]:
+        """Get specific order by ID."""
+        return await self._make_request("GET", f"/orders/{order_id}")
+    
+    async def create_order(self, customer_id: int, **kwargs) -> Dict[str, Any]:
+        """Create a new order."""
+        data = {"socid": customer_id, **kwargs}
+        return await self._make_request("POST", "/orders", data=data)
+    
+    async def update_order(self, order_id: int, **kwargs) -> Dict[str, Any]:
+        """Update an existing order."""
+        return await self._make_request("PUT", f"/orders/{order_id}", data=kwargs)
+    
+    async def delete_order(self, order_id: int) -> Dict[str, Any]:
+        """Delete an order."""
+        return await self._make_request("DELETE", f"/orders/{order_id}")
+    
+    # ============================================================================
+    # CONTACT MANAGEMENT
+    # ============================================================================
+    
+    async def get_contacts(self, limit: int = 100) -> List[Dict[str, Any]]:
+        """Get list of contacts."""
+        params = {"limit": limit}
+        result = await self._make_request("GET", "/contacts", params=params)
+        return result if isinstance(result, list) else []
+    
+    async def get_contact_by_id(self, contact_id: int) -> Dict[str, Any]:
+        """Get specific contact by ID."""
+        return await self._make_request("GET", f"/contacts/{contact_id}")
+    
+    async def create_contact(self, **kwargs) -> Dict[str, Any]:
+        """Create a new contact."""
+        return await self._make_request("POST", "/contacts", data=kwargs)
+    
+    async def update_contact(self, contact_id: int, **kwargs) -> Dict[str, Any]:
+        """Update an existing contact."""
+        return await self._make_request("PUT", f"/contacts/{contact_id}", data=kwargs)
+    
+    async def delete_contact(self, contact_id: int) -> Dict[str, Any]:
+        """Delete a contact."""
+        return await self._make_request("DELETE", f"/contacts/{contact_id}")
+    
+    # ============================================================================
+    # RAW API CALL
+    # ============================================================================
+    
+    async def dolibarr_raw_api(
+        self,
+        method: str,
+        endpoint: str,
+        params: Optional[Dict] = None,
+        data: Optional[Dict] = None
+    ) -> Dict[str, Any]:
+        """Make raw API call to any Dolibarr endpoint."""
+        return await self._make_request(method, endpoint, params=params, data=data)