languagetool-org/languagetool · error · IllegalArgumentException

Unknown level '<level>' - currently, only 'PICKY' is support

Error message

Unknown level '<level>' - currently, only 'PICKY' is supported

What it means

When parsing `--level`, parseOptions() tries JLanguageTool.Level.valueOf(level). If the value is not a defined Level enum constant, it rethrows IllegalArgumentException with this message, since the CLI currently only implements the PICKY level.

Source

Thrown at languagetool-commandline/src/main/java/org/languagetool/commandline/CommandLineParser.java:61

        options.setPrintLanguages(true);
      } else if (args[i].equals("-h") || args[i].equals("-help") || args[i].equals("--help") || args[i].equals("--?")) {
        options.setPrintUsage(true);
      } else if (args[i].equals("-adl") || args[i].equals("--autoDetect")) {    // set autoDetect flag
        options.setAutoDetect(true);
      } else if (args[i].equals("-v") || args[i].equals("--verbose")) {
        options.setVerbose(true);
      } else if (args[i].equals("--line-by-line")) {
        options.setLineByLine(true);
      } else if (args[i].equals("--enable-temp-off")) {
        options.setEnableTempOff(true);
      } else if (args[i].equals("--clean-overlapping")) {
        options.setCleanOverlapping(true);
      } else if (args[i].equals("--level")) {
        String level = args[++i];
        try {
          options.setLevel(JLanguageTool.Level.valueOf(level));
        } catch (IllegalArgumentException e) {
          throw new IllegalArgumentException("Unknown level '" + level + "' - currently, only 'PICKY' is supported");
        }
      } else if (args[i].equals("-t") || args[i].equals("--taggeronly")) {
        options.setTaggerOnly(true);
        if (options.isListUnknown()) {
          throw new IllegalArgumentException("You cannot list unknown words when tagging only");
        }
        if (options.isApplySuggestions()) {
          throw new IllegalArgumentException("You cannot apply suggestions when tagging only");
        }
      } else if (args[i].equals("-r") || args[i].equals("--recursive")) {
        options.setRecursive(true);
      } else if (args[i].equals("-b2") || args[i].equals("--bitext")) {
        options.setBitext(true);
      } else if (args[i].equals("-eo") || args[i].equals("--enabledonly")) {
        if (options.getDisabledRules().size() > 0) {
          throw new IllegalArgumentException("You cannot specify both disabled rules and enabledonly");
        }
        options.setUseEnabledOnly();

View on GitHub (pinned to 2e990059ce)

Solutions

1. Use exactly `--level PICKY` (uppercase).
2. Omit --level entirely to use the default level.
3. Check the JLanguageTool.Level enum constants for the accepted values.
4. Wrap your own call to parseOptions/Main in a try-catch for IllegalArgumentException if you build commands dynamically.

Example fix

// before
languagetool --level picky file.txt
// after
languagetool --level PICKY file.txt

String level = System.getenv("LT_LEVEL");
if (level != null && !level.equals("PICKY")) {
  throw new IllegalArgumentException("--level must be exactly 'PICKY'");
}

try {
  new CommandLineParser().parseOptions(args);
} catch (IllegalArgumentException e) {
  if (e.getMessage().startsWith("Unknown level")) {
    System.err.println("Use --level PICKY (uppercase); it is the only supported level.");
  }
}

When it happens

Trigger: `languagetool --level picky file.txt` (wrong case), `--level PICKYALL`, or any misspelled/unimplemented level name passed after --level.

Common situations: Copy-pasting level names from other tools or docs; assuming case-insensitivity; assuming more levels exist in the CLI than the enum (only PICKY is wired up).

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Unknown mode:
• WrongParameterNumberException
• You cannot list unknown words when tagging only
• You cannot apply suggestions when tagging only
• You cannot specify both disabled rules and enabledonly

AI-assisted analysis of languagetool-org/languagetool@2e990059ce (2026-09-06). Data as JSON: /api/errors/9bea4ea5e32e2413. Report an issue: GitHub.