hermes - 💡(How to fix) Fix [mcp_lazy] MEDIUM: pre_tool_call gives no guidance for unpromoted server-stub calls

Severity: MEDIUM (correctness/error-handling)

pre_tool_call gives no guidance when the model calls a stub for an unpromoted server.

Evidence

plugins/mcp_lazy/hook_impl.py:227-250 — when the model calls a still-visible mcp_server_<name> stub for a server that is NOT yet promoted, the handler returns None (line 250) and falls through to normal dispatch of a synthetic non-tool. There is no load_mcp_server auto-promotion or helpful block directive. Behavior then depends on the dispatcher tolerating an unknown tool.

Related: meta_tool_server.py registers load_mcp_server only when discovery_mode in {server, both} (__init__.py:57), set once at load. A mid-process tool→both flip leaves stubs referencing a tool the model cannot call (document restart requirement or always-register + gate via check()).

Fix

On an unpromoted server-stub call, return a block directing the model to load_mcp_server, mirroring the promoted branch. Document that discovery_mode changes require a restart, or always register load_mcp_server and gate availability dynamically.

Filed from opus-4.8 plugin audit (mcp_lazy).