config Feishu MCP server for open code mmet an Error message：SSE error: Non-200 status code (404)

[iwaner]

Description

I tried to config Feishu MCP server for open code. I meet an Error message：SSE error: Non-200 status code (404)
I have confirm that Feishu MCP support protocolVersion: 2025-03-26（Streamable HTTP）
My OpenCode version：v1.2.27

My opencode.json is like below:
{
"$schema": "https://opencode.ai/config.json",
"mcp": {
"feishu-mcp": {
"type": "remote",
"enabled": true,
"url": "https://mcp.larkenterprise.com/mcp/mytoken",
"headers": {
"x-bbzai-mcp-token": "mytoken"
}
}
}
}

Plugins

No response

OpenCode version

No response

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

No response

Terminal

No response

[github-actions]

This issue might be a duplicate of an existing issue. Please check:

• Unauthenticated streamable HTTP MCP servers are reported as SSE errors instead of missing auth #16247: Same "SSE error: Non-200 status code" symptom when connecting to a remote MCP server that uses streamable HTTP instead of SSE

[dl-alexandre]

Same issue with Tidewave MCP server (local development)

I'm experiencing the exact same problem with lidewave https://github.com/tidewave-ai/tidewave_phoenix- an MCP server for Phoenix/LiveView development.
Environment:

• OpenCode version: latest (installed via npm)
• MCP Server: tidewave 0.5.6 (local SSE server)
• Protocol:
  2025-03-26
  -URL: http://localhost:4003/tidewave/mcp

Error:

SSE error: Unable to connect. Is the computer able to access the url?

HTTP response: 400 Bad Request

Response body: "Unsupported protocol version. Server supports 2025-03-26
or later"

Workaround:
Downgraded to tidewave 0.1.10 (uses older protocol 2024-11-05) which works fine.

Root cause:

The server requires protocol version 2025-03-26 but OpenCode's MCP client appears to be sending an older version. According to the MCP spec, servers can require specific protocol versions.

+1 to getting 2025-03-26 support added to OpenCode!