OneCAD/docs/control-protocol.md

Control protocol

solvecraft --control PORT (or SOLVECRAFT_CONTROL_PORT=PORT) listens on 127.0.0.1:PORT for JSON lines. Each request is one line {"id": …, "method": "…", "params": {…}}; each reply is one line {"id": …, "ok": true, "result": …} or {"id": …, "ok": false, "error": "…"}. Requests are handled on the UI thread between frames; pointer and keyboard input is injected as real egui events, one pointer event per frame.

Engine

Method	Params	Result
engine.execute	command: command id, params: JSON object	the command's result
engine.script	commands: [{command, params}, …]	results, stops at the first error
engine.commands	—	every command: id, label, tab, panel, icon, shortcut, params doc, enabled
document.inspect	measure?: bool	parameters, timeline (errors, timings), bodies, sketches, selection

Commands never open dialogs when run this way. solvecraft-cli commands prints the same registry.

UI

Method	Params	Notes
ui.inspect	—	UI state, viewport rect, camera, active tool/dialog, hover, renderer, timings, live preview (active, busy, error, ms, bodies it stands in for)
ui.set	any UiState field (tab, perspective, showGrid, hiddenBodies, dark, …)	dark: false switches to the light theme
ui.view	view: front, back, top, bottom, left, right, iso, home, fit; animate (bool, default false: snap)
ui.start	command	like a toolbar click: starts the sketch tool or dialog for the command
ui.click	x, y (screen points), button?: left/right/middle, shift?, ctrl?, double?	real pointer input
ui.move	x, y
ui.drag	x0, y0, x1, y1, button?, shift?, ctrl?, steps?, hold?, hold_end?	press, move, release; a left drag on the model is a box selection (left to right: window, right to left: crossing); hold keeps the button down that many frames first (a right press-and-hold opens the marking menu, releasing over a direction picks it), hold_end that many frames at the end (a sketch drag shows its snap)
ui.menu	x?, y?, target?, close?	with a point: open a context menu there as a right-click would (the viewport's marking menu, or a browser menu with target: {"type": "body", "name"} | {"type": "sketch", "id"} | {"type": "component", "id"}); without: the open menu (radial and items: id, label, shortcut, enabled)
ui.menuPick	item: id or label	runs an item of the open menu, as clicking it does
ui.rename	text?, commit? (default true)	finishes the rename box a Rename item opened
ui.selection		the selection, the open dialog's inputs, the hovered item, and the active sketch's drawn dimensions (dimensions: id and text centre, dimension_selected, dimension_editing)
ui.worldToScreen	points: [[x, y, z]…] world points	their screen points
ui.triad		screen points of the 3D sketch move triad's handles (x, y, z, plane)
ui.sketchToScreen	points: [[x, y]…] in active-sketch coordinates	their screen points (null when behind the camera)
ui.dialogInput	index	what clicking an input's Select chip does: picks go to that input
ui.at	world: [x,y,z] | sketch: [x,y] | plane: "XY" | axis: "Z" | dimension: "d1" (its value text) | handle: "arrow" (a manipulator handle, see scenario::publish_handle)	the screen point (a scenario step's target; see crates/ui-egui/src/scenario.rs)
ui.handles	prefix?	the handles drawn last frame, [{name, x, y}]: toolbar buttons and drop-down items toolbar:<command id>, panel labels panel:<tab>:<panel>, browser rows row:<label> and fold arrows fold:<label>, manipulator handles
ui.editFeature	feature (id or name)	what double-clicking a timeline item does: rolls back to it and opens its dialog filled in (sketches open in sketch mode)
ui.scroll	x, y, delta?	wheel zoom at the cursor
ui.key	key (egui key name, Enter, Escape…), cmd?, shift?
ui.text	text	typed text
ui.screenshot	path?	PNG of the window (needs a presented frame)
ui.render	path, width?, height?	CPU render of the model with the current camera (no window needed)
ui.confirm	accept?: bool	answers the Delete confirmation (shown when a delete takes other features with it or makes some fail); without accept, what it lists
ui.documents	action?: new, switch, close, quit; index?; force? (close without asking); answer?: save, dont_save, cancel (answers "save changes?")	the open designs (tabs): names, unsaved flags, the active one, a pending "save changes?" prompt, whether a quit is asking
ui.home	open?: bool; sample?: index	the start page: show or hide it, open a built-in sample (once built); returns open and the recent designs
ui.shortcut	command, key?, replace?	a command's key, or rebinds it ("" clears; a key another command uses is refused unless replace)
ui.help	item?: about, shortcuts (read only), report (copies diagnostics)	the version, commit, build date and diagnostic text
ui.prefs	any of default_units, nav (fusion, solidworks, inventor, alias, tinkercad), zoom_reverse, zoom_to_cursor, orbit_cursor, look_at_anim, look_at_speed, msaa, length_decimals, angle_decimals, theme (dark, light, system), ui_scale, up_axis (z, y), offer_stand_up; open (a page: General, Navigation, Keyboard Shortcuts, Design, Graphics, Sketch, Selection) opens the Preferences dialog there; button: ok, cancel, apply, defaults; stand_up: true stands up a just-opened Y-up file	sets preferences (kept between runs), returns them all plus dialog (the open page or null), dark and stand_up_offer
ui.capture	action?: capture, revert, cancel	answers the Capture Position question (asked when a command starts or the design is saved while components were moved without capturing); without action, what waits
ui.window	action: minimize, maximize, restore, toggle, close	what the title bar's caption buttons do (on Windows and Linux the application bar is the title bar); close asks about unsaved designs first
ui.agent_cursor	show (bool), speed: a number from 1 to 5 (times the normal speed) or "instant" (no animation: the command runs at once and the pointer jumps to where it acted), follow_camera (bool); all optional	the settings. While the cursor is shown, engine.execute first glides to the command's toolbar button and to each pick, then runs and replies; later requests wait their turn. "animate": false on a call skips it
ui.resize	width, height
app.quit	force? (quit without asking about unsaved designs)	quitting (the window closes), asking (a "save changes?" prompt is open)

MCP

solvecraft-cli mcp --connect 127.0.0.1:PORT bridges an MCP client (an AI agent) to this channel; see mcp.md.

Example

{"id":1,"method":"engine.execute","params":{"command":"sketch.create","params":{"plane":"XY"}}}
{"id":2,"method":"engine.execute","params":{"command":"sketch.rectangle.two_point","params":{"p0":[0,0],"p1":[40,30]}}}
{"id":3,"method":"engine.execute","params":{"command":"solid.extrude","params":{"distance":20}}}
{"id":4,"method":"engine.execute","params":{"command":"solid.fillet","params":{"edges":[[0,0,10]],"radius":3}}}
{"id":5,"method":"ui.screenshot","params":{"path":"/tmp/part.png"}}