EventEmitter overflow (drain) when used with OpenCode 1.14.28 — resources/list polling causes listener leak #621

Issue Description

EventEmitter overflow (drain event) when excel-sbroenne MCP server is enabled in OpenCode. After a short period of use, OpenCode crashes with a Node.js overflow error. When the server is disabled, OpenCode works perfectly with no issues.

AI Assistant

• Other: OpenCode v1.14.28 (https://opencode.ai)

MCP Tool & Action

• Tool: N/A — the crash occurs at the connection/initialization level, not during a specific tool call
• Action: The overflow appears to be triggered during getPrompt polling
• File Path: N/A
• Additional Parameters: N/A

Expected Behavior

The MCP server should stay connected and respond to requests from OpenCode without causing the Node.js event loop to overflow.

Actual Behavior

After enabling excel-sbroenne in OpenCode and using it for a short time, OpenCode crashes with:
type: "drain"
count: 11
at overflowWarning (node:events:185:19)
at addListener (node:events:158:22)
at once (node:events:200:36)
...at getPrompt
...at send

Error Response

{
  "error": "Node.js EventEmitter MaxListenersExceededWarning: drain event, count 11, at overflowWarning node:events:185:19"
}

MCP Server Configuration

Configuration file location: C:\Users\JEFRY\.config\opencode\opencode.json

"excel-sbroenne": {
  "type": "local",
  "enabled": true,
  "command": [
    "C:/Users/JEFRY/.dotnet/tools/mcp-excel.exe"
  ],
  "environment": {
    "DOTNET_EnableDiagnostics": "0",
    "APPLICATIONINSIGHTS_CONNECTION_STRING": ""
  },
  "timeout": 60000
}

Environment

• Windows Version: Windows 11
• Excel Version: Excel 365
• ExcelMcp Version: v1.8.50
• .NET Version: 8.0 and 10.0 (both installed)
• Installation Method:
  • Global .NET tool (dotnet tool install --global Sbroenne.ExcelMcp.McpServer)

MCP Server Logs

INFO service=mcp key=excel-sbroenne toolCount=25 create() successfully created client
warn: ModelContextProtocol.Server.McpServer[2049951654]
Server (excel-mcp 1.8.50.0), Client (opencode 1.14.28) received request for method 'resources/list', but no handler is available.
warn: ModelContextProtocol.Server.McpServer[975074943]
Server (excel-mcp 1.8.50.0), Client (opencode 1.14.28) method 'resources/list' request handler failed in 29.7949ms.
ModelContextProtocol.McpProtocolException: Method 'resources/list' is not available.
ERROR service=mcp clientName=excel-sbroenne error=MCP error -32601: Method 'resources/list' is not available. failed to get resources

Steps to Reproduce

1. Install mcp-excel via dotnet tool install --global Sbroenne.ExcelMcp.McpServer
2. Configure OpenCode with the MCP server as shown above
3. Start OpenCode — server connects successfully showing 25 tools
4. Use OpenCode normally for a few minutes
5. OpenCode crashes with EventEmitter overflow on drain event

Additional Context

• The server connects successfully at startup (25 tools detected)
• The crash happens during active use, not at startup
• Disabling excel-sbroenne completely fixes the issue — OpenCode runs stably
• The resources/list method is not implemented in the server, OpenCode receives -32601 error repeatedly which may be contributing to the listener accumulation
• Also tried with the standalone ZIP executable (ExcelMcp-MCP-Server-1.8.50-windows.zip) — same overflow occurs
• OpenCode uses Bun (not Node.js directly) as its runtime

Question

Is there a known workaround for this compatibility issue with OpenCode? Could the repeated resources/list polling by OpenCode be causing the listener leak?