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TethysL Extension Activation

When activated by VS Code, the TethysL extension:

  • Will check if the tethysl program is already available on your PATH. If so, it will use it to start the TethysL LSP server. The extension should now be fully functional.
  • Otherwise:

    • The extension will check for java in your PATH and, if not found, it will offer you options to download a Java Runtime Environment or to select the home location of your already installed Java environment.

      Automatic Java installation

      If the automatic Java installation attempted by the extension fails for some reason on your machine, please let us know, and, in the meantime, please make sure you have java available on your PATH. You can install Java using common package managers or directly from

    • With java now satisfied, the extension will then automatically download and use the TethysL CLI program from The specific CLI version to be downloaded will directly depend on the extension version itself. The extension will then start the TethysL language server and be ready to use.

TethysL CLI

The more self-contained extension as describe above —that is, in terms of taking care of downloading its own dependencies— has been implemented mainly as a convenience for general users.

However, you may want to have a directly installed TethysL CLI on your system for the following reasons:

  • The VS Code extension will use it right away (as already mentioned);
  • You can use the CLI directly not only for compiling .tl scripts, but also for other various tasks, including use in shell scripts and makefiles (as part of preparations for vehicle deployments), etc.