Description

OpenCode MCP client fails to connect to GitLab MCP server (v18.9+) with 401 Unauthorized error.

Environment

• OpenCode version: 1.3.9
• GitLab version: 18.9.2-ee
• GitLab MCP endpoint: /api/v4/mcp

Steps to Reproduce

1. Configure photon MCP server with GitLab self-managed instance (18.9+)
2. Run opencode mcp list or opencode mcp debug photon

Expected Result

MCP connection succeeds with successful handshake

Actual Result

HTTP response: 401 Unauthorized
Server returned 401 Unauthorized
Connection error: Streamable HTTP error: Error POSTing to endpoint: {\"message\":\"Invalid params\",\"data\":{\"params\":\"Unsupported protocol version '2024-11-05'. Supported: 2025-06-18, 2025-03-26, 2025-11-25\"}}

Root Cause

OpenCode MCP client sends protocolVersion: "2024-11-05" in the initialize request, but GitLab 18.9+ only supports:

• 2025-06-18
• 2025-03-26
• 2025-11-25

The client needs to be updated to use a supported protocol version.

Workaround

None - the protocol version is hardcoded in the client.

Verification

Manual test with curl using correct protocol version succeeds:

```bash
curl -sk -X POST "https://gitlab.example.com/api/v4/mcp"
-H "Authorization: Bearer $TOKEN"
-H "Content-Type: application/json"
-d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}'

Returns: {"jsonrpc":"2.0","result":{"protocolVersion":"2025-06-18","capabilities":{"tools":{"listChanged":false}},"serverInfo":{"name":"Official GitLab MCP Server","version":"18.9.2-ee"},"id":1}}

```