LSP Server (lsp)

The lsp command starts the OPC UA Modeler Language Server, which powers real-time diagnostics, completions, hover docs, and quick fixes in your editor.

VS Code users get this automatically through the VS Code Extension. For other editors see the LSP Server setup guide.

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stdio mode

Used by editors that spawn the language server as a child process (VS Code, Neovim, Zed, Emacs):

opcua-modeler lsp --stdio

The server reads LSP messages from stdin and writes responses to stdout. You do not normally run this command directly — your editor configuration does it for you.

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Socket mode

New in v2.0.0

For multi-client setups (browser-based editors, CI tooling, or shared developer environments), start the server in WebSocket / TCP socket mode:

# Start on default port
opcua-modeler lsp --socket 7000

# Keep it running in the background (Windows)
Start-Process opcua-modeler -ArgumentList "lsp","--socket","7000" -WindowStyle Hidden

Multiple editors can connect to the same running server instance. The server maintains isolated per-connection state while sharing the expensive OPC UA address space cache across all connections — so only the first connection pays the startup cost.

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Options

Flag	Description
--stdio	Run in stdio mode (for editors that spawn the server)
--socket <port>	Run in TCP socket mode on the given port