Windows MCP local server fails with Bun but works with NPX (Error -32000) #6994

Description

When configuring a local MCP server using bun x or bun run on Windows, OpenCode fails with MCP error -32000: Connection closed.

"mcp": {
"exa_search": {
"type": "local",
"enabled": true,
"command": [
"bun",
"x",
"-y",
"exa-mcp-server"
],
"env": {
"EXA_API_KEY": "####"
}
}
}

This is what is output in debug logs:
ERROR 2026-01-05T19:30:57 +75ms service=mcp key=exa_search command=["bun","x","-y","exa-mcp-server"] cwd=C:\Users####\OpenCode error=MCP error -32000: Connection closed local mcp startup failed

Note: bun will install when run outside of OpenCode .

Installing Node.js and using ["npx", "-y", "exa-mcp-server"] resolves the issue because Node does not pollute the stdout pipe with startup logs.

Plugins

No response

OpenCode version

1.1.3

Steps to reproduce

1. Install exa-mcp-server via Bun.
2. Configure opencode.jsonc using ["bun", "x", "exa-mcp-server"]
3. Run opencode run --print-logs --log-level=DEBUG "hi"
4. Observe the -32000 error in debug logs.

Screenshot and/or share link

Operating System

Windows 11

Terminal

Windows Terminal