When the gateway processes /reload-mcp, it reconnects MCP servers and
updates the global _servers registry, but cached AIAgent instances in
_agent_cache keep the tools list they were built with. The user had to
also run /new (discarding conversation history) before the agent could
see the new tools — even though /reload-mcp had succeeded.
This patch refreshes each cached agent's .tools and .valid_tool_names
in _execute_mcp_reload after discovery returns, so existing sessions
pick up new MCP tools on their next turn. The slash-confirm gate in
_handle_reload_mcp_command already obtains user consent for the
implied prompt-cache invalidation before this code runs.
Mirrors the equivalent behaviour the CLI already does in cli.py
_reload_mcp. Per-agent enabled_toolsets and disabled_toolsets are
preserved so an agent that was scoped to a subset of toolsets does
not silently gain disabled tools after the reload.
Original diagnosis + initial implementation in #23812 from @fujinice.
The auto-reload watcher half of that PR is intentionally dropped —
users want /reload-mcp to remain explicit.
Co-authored-by: fujinice <45688690+fujinice@users.noreply.github.com>
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