The JSON Config schema for type 'text' enforces additionalProperties:false and 'multiline' is not a documented property. Its presence caused the admin UI to fail schema validation and refuse to render the panel. Multi-line behaviour is already provided by 'minRows: 6' alone — the schema explicitly states: "Set this attribute to 2 or more if you want to have a textarea with more than one row." Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>