MCP server processes not cleaned up on exit (orphan processes) + eagerly starts all servers #30123

Bug Description

When OpenCode exits, MCP server child processes are not killed, leaving orphan processes running indefinitely. Additionally, OpenCode eagerly starts ALL configured stdio-type MCP servers at launch regardless of whether they will be used.

Impact

• 30 orphan node.exe processes accumulated (from just 2 sessions), each consuming 45-75MB RAM
• Total wasted memory: ~1.5GB
• CPU fan noise due to unnecessary load

Root Cause

1. Process tree: OpenCode -> cmd /c npx -y -> node(npx-cli.js) -> node(MCP server)
2. When OpenCode exits, it does not cascade SIGTERM/kill to child processes
3. The cmd /c wrapper exits early (by design of /c), making npx and MCP server orphans
4. Windows does not auto-clean orphan processes — they run forever waiting on closed stdin

All MCP servers are started eagerly

Even if a session never uses avily, exa, memory, sequential-thinking, or context7, all of them are launched at startup. This wastes CPU and memory on every session.

Expected Behavior

1. On exit: OpenCode should kill all spawned child processes (the entire process tree)
2. On startup: MCP servers should be lazily started only when first needed (or at least have a config option for this)
3. Alternatively: MCP servers should detect stdin EOF and exit themselves

Environment

• Windows (Win32)
• OpenCode (latest)
• MCP servers launched via: \cmd /c npx -y @modelcontextprotocol/server-sequential-thinking\ (and similar)

Workaround

Users can manually kill orphan processes:
\\powershell
taskkill /f /im node.exe
\\

Or disable unused MCP servers in opencode.json to prevent them from starting.