1.1.5 • Public • Published

kOS Language Server

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A language server for Kerboscript within the KOS mod for Kerbal Space Program. A language server can provide features typical to an IDE language for the supported target language, in this case Kerboscript.

The project currently supports the following clients

For additional client support such as sublime text, emacs, notepad++ or others please post an issue with the requested editor.


Currently the vscode client 1.1.5 implements the follow features

  • syntax highlighting
  • brace detection
  • code snippets
  • diagnostics on parsing errors
  • go to definition for symbols and run statements
  • symbol auto complete
  • suffix auto complete
  • manual completion triggering
  • rename symbol
  • unreachable code detection
  • function signature help
  • file symbol lookup
  • workspace symbol lookup
  • identify symbols that don't exist
  • identify unused symbols
  • identify symbols that shadow (hide) an existing variable
  • identify symbols that may not exist at runtime
  • on hover type definitions (experimental)
  • full workspace loading and change propagation
  • documentation searching


The language server includes several comment directives that can be included extra functionality

  • \\ #include <file path>: Include a script file in the current files scope even if no run is present
  • \\ #region: Foldable region start
  • \\ #endRegion: Foldable region end


All commands can be launched with ctrl+shift+p

  • launch kerbal space program kOS: Start Kerbal Space Program
  • launch telnet client using kOS: Connect Telnet Client
  • Route server logging to LSP inspector kOS: Route Logging to LSP inspector
  • Route server logging to Vscode kOS: Route Logging to Vscode
  • Search kOS Documentation kOS: Search Documentation

Workspace Configuration

The workspace can be configured with a file called ksconfig.json. The following is an example

  "archive": "..",
  "bodies": ["earth", "moon", "sun"],
  "linting": {
    "control-flow-break": "off"

This will set the archive folder to correspond to the folder above, the valid bodes to be earth, moon and sun and to turn off linting related to invalid break statements. More info can be found here.

Global Configuration

These settings are currently included with the tool

  • kos-vscode.kerbalSpaceProgramPath Path to kerbal space program
  • kos-vscode.completionCase Indicate the preferred completion case for built in symbols
  • kos-vscode.telnetHost Host name of the telnet server
  • kos-vscode.telnetPort Host port of the telnet server
  • kos-vscode.lspPort Port to send lsp message to for the LSP Inspector
  • kos-vscode.trace.server
    • verbosity Detail level of the logs
    • format Log format
    • level Message level


This project is heavily inspired by the crafting interpreters series. Definitely check it out if your interested in creating your own language, or language tooling.

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npm i kos-vscode

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  • jonnyboyc