session-scoped-mcp-invisible-to-pre-existing-subagents
Session-scoped MCP servers (claude mcp add -s project) registered mid-session are not visible to subagents that were dispatched before the registration. Permanent (user-scope) MCP servers registered at mcpServers top-level in .claude.json are always visible to all subagents. For tasks requiring a session MCP, register it before dispatching any subagents.