feat: auto add MCP projects servers with auth API key mode

src/backend/base/langflow/__main__.py

@@ -341,6 +341,9 @@ def run(
         if is_port_in_use(port, host):
             port = get_free_port(port)
 
+        # Store the actual port being used in settings
+        get_settings_service().settings.current_port = port
+
         protocol = "https" if ssl_cert_file_path and ssl_key_file_path else "http"
 
     # Step 4: Loading Components (placeholder for components loading)

src/backend/base/langflow/api/v1/mcp_projects.py

@@ -48,6 +48,9 @@
 from langflow.services.database.models.api_key.model import ApiKeyCreate
 from langflow.services.database.models.user.model import User
 
+# Constants
+ALL_INTERFACES_HOST = "0.0.0.0"  # noqa: S104
+
 router = APIRouter(prefix="/mcp/project", tags=["mcp_projects"])
 
 
@@ -448,7 +451,7 @@ def is_local_ip(ip_str: str) -> bool:
         return True
 
     # Check if it's exactly "0.0.0.0" (which binds to all interfaces)
-    if ip_str == "0.0.0.0":  # noqa: S104
+    if ip_str == ALL_INTERFACES_HOST:
         return True
 
     try:
@@ -888,8 +891,17 @@ async def get_project_sse_url(project_id: UUID) -> str:
     """Generate the SSE URL for a project, including WSL handling."""
     # Get settings service to build the SSE URL
     settings_service = get_settings_service()
-    host = getattr(settings_service.settings, "host", "localhost")
-    port = getattr(settings_service.settings, "port", 3000)
+    server_host = getattr(settings_service.settings, "host", "localhost")
+    # Use the actual running port (current_port) if available, otherwise fall back to configured port
+    server_port = getattr(settings_service.settings, "current_port", None) or getattr(
+        settings_service.settings, "port", 7860
+    )
+
+    # For MCP clients, always use localhost instead of 0.0.0.0
+    # 0.0.0.0 is a bind address, not a connect address
+    host = "localhost" if server_host == ALL_INTERFACES_HOST else server_host
+    port = server_port
+
     base_url = f"http://{host}:{port}".rstrip("/")
     project_sse_url = f"{base_url}/api/v1/mcp/project/{project_id}/sse"
 

src/backend/base/langflow/api/v1/projects.py

@@ -12,16 +12,24 @@
 from fastapi.responses import StreamingResponse
 from fastapi_pagination import Params
 from fastapi_pagination.ext.sqlmodel import apaginate
+from lfx.base.mcp.constants import MAX_MCP_SERVER_NAME_LENGTH
+from lfx.base.mcp.util import sanitize_mcp_name
+from lfx.log.logger import logger
 from sqlalchemy import or_, update
 from sqlalchemy.orm import selectinload
 from sqlmodel import select
 
 from langflow.api.utils import CurrentActiveUser, DbSession, cascade_delete_flow, custom_params, remove_api_keys
 from langflow.api.v1.flows import create_flows
+from langflow.api.v1.mcp_projects import get_project_sse_url
 from langflow.api.v1.schemas import FlowListCreate
+from langflow.api.v2.mcp import update_server
 from langflow.helpers.flow import generate_unique_flow_name
 from langflow.helpers.folders import generate_unique_folder_name
 from langflow.initial_setup.constants import STARTER_FOLDER_NAME
+from langflow.services.auth.mcp_encryption import encrypt_auth_settings
+from langflow.services.database.models.api_key.crud import create_api_key
+from langflow.services.database.models.api_key.model import ApiKeyCreate
 from langflow.services.database.models.flow.model import Flow, FlowCreate, FlowRead
 from langflow.services.database.models.folder.constants import DEFAULT_FOLDER_NAME
 from langflow.services.database.models.folder.model import (
@@ -32,6 +40,7 @@
     FolderUpdate,
 )
 from langflow.services.database.models.folder.pagination_model import FolderWithPaginatedFlows
+from langflow.services.deps import get_settings_service, get_storage_service
 
 router = APIRouter(prefix="/projects", tags=["Projects"])
 
@@ -74,6 +83,46 @@ async def create_project(
         await session.commit()
         await session.refresh(new_project)
 
+        # Auto-register MCP server for this project with API key auth
+        if get_settings_service().settings.add_projects_to_mcp_servers:
+            try:
+                # Create API key
+                api_key_name = f"MCP Project {new_project.name} - default"
+                unmasked_api_key = await create_api_key(session, ApiKeyCreate(name=api_key_name), current_user.id)
+
+                # Set folder auth to API key mode (encrypted at rest)
+                new_project.auth_settings = encrypt_auth_settings({"auth_type": "apikey"})
+                session.add(new_project)
+                await session.commit()
+                await session.refresh(new_project)
+
+                # Build SSE URL
+                sse_url = await get_project_sse_url(new_project.id)
+
+                # Prepare server config
+                command = "uvx"
+                args = [
+                    "mcp-proxy",
+                    "--headers",
+                    "x-api-key",
+                    unmasked_api_key.api_key,
+                    sse_url,
+                ]
+                server_config = {"command": command, "args": args}
+
+                # Determine server name and register in user's _mcp_servers.json
+                server_name = f"lf-{sanitize_mcp_name(new_project.name)[: (MAX_MCP_SERVER_NAME_LENGTH - 4)]}"
+                await update_server(
+                    server_name,
+                    server_config,
+                    current_user,
+                    session,
+                    get_storage_service(),
+                    get_settings_service(),
+                )
+            except Exception as e:  # noqa: BLE001
+                await logger.aexception(f"Failed to auto-register MCP server for project {new_project.id}: {e}")
+
         if project.components_list:
             update_statement_components = (
                 update(Flow).where(Flow.id.in_(project.components_list)).values(folder_id=new_project.id)  # type: ignore[attr-defined]

src/lfx/src/lfx/services/settings/base.py

@@ -214,6 +214,8 @@ class Settings(BaseSettings):
     """The host on which Langflow will run."""
     port: int = 7860
     """The port on which Langflow will run."""
+    current_port: int | None = None
+    """The actual port on which Langflow is running (after checking for port conflicts)."""
     workers: int = 1
     """The number of workers to run."""
     log_level: str = "critical"
@@ -263,6 +265,11 @@ class Settings(BaseSettings):
     mcp_server_enable_progress_notifications: bool = False
     """If set to False, Langflow will not send progress notifications in the MCP server."""
 
+    # Add projects to MCP servers automatically on creation
+    add_projects_to_mcp_servers: bool = True
+    """If set to True, newly created projects will be added to the user's MCP servers config automatically.
+    Controlled by LANGFLOW_ADD_PROJECTS_TO_MCP_SERVERS env variable."""
+
     # Public Flow Settings
     public_flow_cleanup_interval: int = Field(default=3600, gt=600)
     """The interval in seconds at which public temporary flows will be cleaned up.