feat: add SSE and HTTP transport support for MCP servers

- Add type, url, and headers fields to MCP server config
- Update MCP client to handle stdio, sse, and http transports
- Add todos field to ThreadState
- Add Deerflow branding requirement to frontend-design skill
- Update extensions_config.example.json with SSE/HTTP examples

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/src/agents/thread_state.py

@@ -18,3 +18,4 @@ class ThreadState(AgentState):
     thread_data: NotRequired[ThreadDataState | None]
     title: NotRequired[str | None]
     artifacts: NotRequired[list[str] | None]
+    todos: NotRequired[list | None]

backend/src/config/extensions_config.py

@@ -12,9 +12,12 @@ class McpServerConfig(BaseModel):
     """Configuration for a single MCP server."""
 
     enabled: bool = Field(default=True, description="Whether this MCP server is enabled")
-    command: str = Field(..., description="Command to execute to start the MCP server")
-    args: list[str] = Field(default_factory=list, description="Arguments to pass to the command")
+    type: str = Field(default="stdio", description="Transport type: 'stdio', 'sse', or 'http'")
+    command: str | None = Field(default=None, description="Command to execute to start the MCP server (for stdio type)")
+    args: list[str] = Field(default_factory=list, description="Arguments to pass to the command (for stdio type)")
     env: dict[str, str] = Field(default_factory=dict, description="Environment variables for the MCP server")
+    url: str | None = Field(default=None, description="URL of the MCP server (for sse or http type)")
+    headers: dict[str, str] = Field(default_factory=dict, description="HTTP headers to send (for sse or http type)")
     description: str = Field(default="", description="Human-readable description of what this MCP server provides")
     model_config = ConfigDict(extra="allow")
 

backend/src/gateway/routers/mcp.py

@@ -16,9 +16,12 @@ class McpServerConfigResponse(BaseModel):
     """Response model for MCP server configuration."""
 
     enabled: bool = Field(default=True, description="Whether this MCP server is enabled")
-    command: str = Field(..., description="Command to execute to start the MCP server")
-    args: list[str] = Field(default_factory=list, description="Arguments to pass to the command")
+    type: str = Field(default="stdio", description="Transport type: 'stdio', 'sse', or 'http'")
+    command: str | None = Field(default=None, description="Command to execute to start the MCP server (for stdio type)")
+    args: list[str] = Field(default_factory=list, description="Arguments to pass to the command (for stdio type)")
     env: dict[str, str] = Field(default_factory=dict, description="Environment variables for the MCP server")
+    url: str | None = Field(default=None, description="URL of the MCP server (for sse or http type)")
+    headers: dict[str, str] = Field(default_factory=dict, description="HTTP headers to send (for sse or http type)")
     description: str = Field(default="", description="Human-readable description of what this MCP server provides")
 
 

backend/src/mcp/client.py

@@ -18,15 +18,26 @@ def build_server_params(server_name: str, config: McpServerConfig) -> dict[str,
     Returns:
         Dictionary of server parameters for langchain-mcp-adapters.
     """
-    params: dict[str, Any] = {
-        "command": config.command,
-        "args": config.args,
-        "transport": "stdio",  # Default to stdio transport
-    }
+    transport_type = config.type or "stdio"
+    params: dict[str, Any] = {"transport": transport_type}
 
-    # Add environment variables if present
-    if config.env:
-        params["env"] = config.env
+    if transport_type == "stdio":
+        if not config.command:
+            raise ValueError(f"MCP server '{server_name}' with stdio transport requires 'command' field")
+        params["command"] = config.command
+        params["args"] = config.args
+        # Add environment variables if present
+        if config.env:
+            params["env"] = config.env
+    elif transport_type in ("sse", "http"):
+        if not config.url:
+            raise ValueError(f"MCP server '{server_name}' with {transport_type} transport requires 'url' field")
+        params["url"] = config.url
+        # Add headers if present
+        if config.headers:
+            params["headers"] = config.headers
+    else:
+        raise ValueError(f"MCP server '{server_name}' has unsupported transport type: {transport_type}")
 
     return params
 

backend/src/tools/tools.py

@@ -38,7 +38,7 @@ def get_available_tools(groups: list[str] | None = None, include_mcp: bool = Tru
 
             mcp_tools = get_cached_mcp_tools()
             if mcp_tools:
-                logger.debug(f"Using {len(mcp_tools)} cached MCP tool(s)")
+                logger.info(f"Using {len(mcp_tools)} cached MCP tool(s)")
         except ImportError:
             logger.warning("MCP module not available. Install 'langchain-mcp-adapters' package to enable MCP tools.")
         except Exception as e: