nodecode-canvas

Board: a diagram the agent draws with tool calls and you open as one page. A Nodecode rewrite of skk2010/hermes-board-plugin by skk2010.

A board is one JSON document under the folder you point it at. The model draws on it with the original's six tools and its op vocabulary — nodes, edges, free lines, groups, notes, captions, a title, a grid, and the layered layout placement — and board_render writes the same drawing as a standalone SVG or as one HTML page that opens in any browser. Nothing has to be installed for the picture: no browser, no Python, no service.

Get it

Tell the agent "add the canvas cell", or run:

nodecode add nc://nodecode-canvas

Set it up

One setting, in /settings (or the page's Settings tab):

"canvas": { "dir": "~/boards", "max_nodes": 400 }

dir is where boards live: boards/<id>.json under it, and render/ for the pictures. max_nodes (default 400) caps how big one board may grow. Until dir is set the cell still runs; a tool that needs it says so.

Use it

Ask for a diagram — "draw the checkout flow" — and the model calls board_apply with a list of ops:

board_new  {id: "checkout", title: "Checkout"}
board_apply {id: "checkout", ops: [
  {op: "add_node", id: "cart", text: "Cart"},
  {op: "add_node", id: "pay",  text: "Payment", x: 360, y: 60},
  {op: "add_edge", from: "cart", to: "pay", label: "submits"},
  {op: "add_note", text: "idempotency key here", x: 60, y: 320},
  {op: "layout", rows: [["cart"], ["pay"]], direction: "down"}
]}
board_render {id: "checkout", format: "html"}

The tools, the same six the Hermes plugin registered:

board_list — the boards in the folder, with a one-line shape of each.
board_get — one board whole: the JSON document and its summary. Read it before editing, so the ids are the ones on the board.
board_new, board_delete — one file each; board_new refuses an id that exists.
board_apply — an ordered op list applied in one call, then saved. An op that refuses (an unknown op, an edge naming a node that is not there, a tone outside the palette, a full board) fails the call and saves nothing, naming the op by its index.
board_render — format: "svg" for the drawing alone, "html" for the same drawing on a page; answers the file's path.

The operator's side is /canvas: list, show ID, new ID [TITLE], delete ID, render ID [svg|html].

Ops: add_node, update_node, move_node, delete_node, add_edge, update_edge, delete_edge, add_line, update_line, delete_line, add_group, update_group, delete_group, add_caption, add_note, update_note, delete_note, set_title, set_grid, layout. A node carries text, an optional sub, a tone (default, accent, ok, warn, danger, muted), a family (box, pill, diamond, note, caption, cloud, cylinder, document, hexagon, area) and its own size and position; a node with no x/y lands in the next free slot.

What the rewrite leaves out

The Hermes plugin also docked an editor pane beside the conversation and woke the session when you edited the board there (board_watch), rendered PNG through a headless Chrome on PATH, and carried bus (shared-trunk connections), graph (ranks derived from the edges) and the table node. A cell has no editor pane, and a page that opens in your browser needs no browser to be run by the cell — so the picture is SVG and HTML, layout places what graph would have, and bus and tables are not rewritten. The NOTICE says the same in one paragraph.

Test it

.github/test-cell.sh tools/nodecode-canvas

nc://canvas