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

[bagleytravis68]

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.

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Operating System

Windows 11

Terminal

Windows Terminal