Headless runs now report which MCP servers config validation silently dropped, via `mcp_server_errors`
Claude Code Changelog·medium signal
v2.1.219 added `mcp_server_errors` to the headless `stream-json` init event, listing `--mcp-config` entries skipped by config validation; terminal runs print a startup warning. Previously a malformed entry meant the agent ran to completion with fewer tools than you thought it had and no signal anywhere in the output — a failure mode that looks like model regression, not misconfiguration. The same release added HTTP status and error text to `claude mcp list` and `/mcp` on connection failure, plus a warning for MCP config values carrying hidden leading or trailing whitespace.