Who placed the item. Drives the ownership chrome (chips / violet vs slate-amber).
OptionalHOptional max height in px; content beyond it is clipped. Omitted = content-driven.
Stable item id (e.g. sticky-3) — referenced by connectors, deltas and agent tools.
The markdown source. Rendered SAFELY (sanitized — never raw HTML passthrough).
OptionalTagOptional free-form role tag ('slot', 'heading', 'step-done'). It carries no behavior:
the board lands it on the item's wrapper as a wb-tag-<slug> class (see
WhiteboardTagClass) so a host restyling the board from outside can tell two ROLES of
one kind apart — a shape used as a section head vs an empty "fill this in" slot — which the
DOM could not distinguish before (CSS cannot select on label text). Persisted with the item;
the agent's scene view carries it as tag.
Panel width in px (required — markdown always renders in an explicit column).
Render order (higher renders on top). Assigned by the engine.
A rendered MARKDOWN panel — a rich, formatted card (headings, lists, code, links) for illustrative content that outgrows a sticky note. Width is explicit (the panel's column width); height is content-driven, optionally capped by
H(overflow clips).