MCP prompts/list -32601 causes infinite npx process spawning and UI freeze #26012

Description

When opening a new session or switching to a new workspace folder, OpenCode sends prompts/list requests to all configured local MCP servers. Servers that don't support this protocol method (playwright MCP, zai-mcp-server) return error -32601 (Method not found).

OpenCode retries these requests indefinitely, each time forking a new npx child process under opencode-cli.exe. Across 10+ session restarts in a single day, this accumulates into:

• 13× duplicate npx @playwright/mcp@latest processes (each wrapped by a separate cmd.exe)
• 13× duplicate npx -y @z_ai/mcp-server processes
• 5+ PowerShell/CMD wrapper processes
• 37 total child processes, 514 handles, 58 threads
• Sidecar memory: 855MB+

This causes:

1. Built-in terminal becomes unresponsive (cannot type)
2. Switching to a new folder session hangs indefinitely
3. Archiving sessions freezes the UI
4. Existing sessions that already initialized their MCP connections work normally

Log files at %APPDATA%\ai.opencode.desktop\logs\ contain hundreds of:

Plugins

@tarquinen/opencode-dcp@latest oh-my-openagent@latest

OpenCode version

Desktop: v1.14.39 CLI: v1.14.33

Steps to reproduce

1. Configure 2+ local MCP servers in opencode.json that use npx (e.g., playwright: npx @playwright/mcp@latest, zai-mcp-server: npx -y @z_ai/mcp-server)
2. Launch OpenCode desktop app
3. Open a new workspace folder session (NOT an existing session that already initialized)
4. Wait 2-3 minutes, then open Task Manager → observe duplicate npx processes accumulating under opencode-cli.exe
5. Try using the built-in terminal or switching to another session → observe freeze/unresponsiveness
6. Check %APPDATA%\ai.opencode.desktop\logs\ for "MCP error -32601" spam

Screenshot and/or share link

N/A — log evidence available at %APPDATA%\ai.opencode.desktop\logs
Crash dump: %LOCALAPPDATA%\CrashDumps\OpenCode.exe.42804.dmp

Operating System

Windows 11 Pro 10.0.26200

Terminal

OpenCode built-in terminal (PowerShell 5.1 backend)