--serve remains available for isolated headless scripts. live.py connects to the real desktop application through a private per-process descriptor under the user's OCS configuration directory. The GUI owns every mutation: transport threads only validate and enqueue requests.

The live protocol requires protocol version 1, stable session/document IDs, an expected edit revision for mutations, and a unique request ID. Commands report waiting_input while interactive work remains. Asynchronous file and renderer work remains running until its real callback finishes. A bounded operation cache makes retries with the same payload idempotent; after a restart or an expired operation, clients must read state instead of replaying a mutation.

Operations include document state and activation, paged entity queries, layer/header/property inspection, command discovery, start/run/step/cancel, WCS/UCS/relative points, entity and structure picks, selection, property edits, semantic UI actions, undo/redo, protected save, event polling, and current-window PNG capture. The status bar includes a control switch whose green, yellow, and red states mean ready, busy, and off.

The Web build exposes ocs_control_submit(json) and ocs_control_take(ticket). They enter the same bounded GUI queue and return the same semantic responses; browser code polls the ticket until a response is present.

OpenCADStudio --mcp is the common local entry point for every MCP client. It is built into the application, uses stdio, launches the editor when needed, and has no Python or package-manager dependency. Tool definitions and safety instructions are served by MCP itself, so the drawing behavior is identical in every client.

Run ./docs/automation/install.sh once for a source build. It installs the release binary in ~/.local/share/ocs-control and automatically connects installed Codex and Claude Code CLIs. Both registrations point to the same binary. Re-run an individual connection later with:

~/.local/share/ocs-control/connect.sh codex
~/.local/share/ocs-control/connect.sh claude-code

Any other local MCP client uses the same command and argument. connect.sh config prints the portable configuration object to paste into clients that do not provide a registration CLI:

{"mcpServers":{"opencadstudio":{"command":"/path/to/OpenCADStudio","args":["--mcp"]}}}

Client-specific skills and extension manifests may improve discovery, but contain no drawing or protocol implementation. Adding another AI client therefore requires only registering this command; the OpenCADStudio executable and tools do not change.

The legacy client is unchanged:

from ocs import Ocs
with Ocs(binary="OpenCADStudio") as app:
    app.new()
    app.run("LINE 0,0 100,0")

For direct live diagnostics:

python3 docs/automation/live.py --launch
python3 docs/automation/live.py '{"op":"state"}'