---
title: MCP Transport Modes Guide
description: "Choose the right transport mode for GitLab MCP Server. Compare stdio for CLI tools and desktop apps, SSE for legacy web clients, and StreamableHTTP for modern HTTP-based MCP communication."
head:
- - meta
- name: keywords
content: gitlab mcp transport, stdio, SSE, StreamableHTTP, http mode, mcp server transport, server-sent events
---
# MCP Transport Modes Guide
The server automatically selects the appropriate transport mode based on configuration.
## Automatic Mode Selection
| Configuration | Transport Mode | Endpoints | Use Case |
|--------------|----------------|-----------|----------|
| `PORT` env var present | HTTP (Dual) | `/sse` and `/mcp` | Web clients, HTTP-based MCP |
| No `PORT` env var | stdio | N/A | CLI tools, direct MCP |
| `stdio` argument | stdio (forced) | N/A | Override PORT when set |
## HTTP Mode (Dual Transport)
When `PORT` is set, the server starts an Express HTTP server providing both endpoints simultaneously:
- **`/mcp`** — StreamableHTTP (recommended for modern clients)
- **`/sse`** — Server-Sent Events (backwards compatibility)
Features:
- Session management and reconnection
- Perfect for web-based MCP clients
- Supports TLS termination (direct or via reverse proxy)
## stdio Mode
Direct stdin/stdout communication:
- No HTTP server required
- Optimal for command-line tools
- Lower resource usage
- Used by most desktop MCP clients (Claude Desktop, VS Code, Cursor)
## Forcing stdio Mode
If `PORT` is set but you need stdio mode:
```bash
npx @structured-world/gitlab-mcp stdio
```
The `stdio` argument overrides the PORT environment variable.
