stanfordnlp/CoreNLP · error · IllegalArgumentException

Unknown option:

Error message

Unknown option: 

What it means

Options.setOption resolves a command-line flag first via the lexparser option flags and then via the TreebankLanguagePack params; if neither consumes the flag, it throws IllegalArgumentException('Unknown option: ...'). It guarantees that every training/test flag passed to the parser is actually recognized.

Solutions

1. Fix the flag spelling/name in your argument list.
2. Run the parser with no arguments or consult the lexparser options documentation for valid flags for your version.
3. If it is a version mismatch, check the release notes and update or remove obsolete flags.
4. Pass a supported -tlpp / treebank language pack if the flag is language-pack specific.

Example fix

// before
options.setOptions(new String[]{"-maxLen", "40"});
// after
options.setOptions(new String[]{"-maxLength", "40"});

Set<String> validFlags = Set.of("-maxLength","-outputFormat","-tlpp","-writeGrammarFiles");
for (int i = 0; i < args.length; i++) if (args[i].startsWith("-")) assert validFlags.contains(args[i]) : "Unknown flag: " + args[i];

try {
  options.setOptions(flags);
} catch (IllegalArgumentException e) {
  System.err.println("Bad parser flag: " + e.getMessage());
}

When it happens

Trigger: Passing a flag string (e.g., via Options.setOptions, main(), or -props-style command lines) that neither setOptionFlag nor tlpParams.setOptionFlag recognizes, so the returned index equals the input index i.

Common situations: Typos in flags (e.g., '-maxLen' instead of '-maxLength'), flags removed or renamed across Stanford Parser versions, or flags that belong to a different parser package.

Understand the failure class

Background: "Unknown argument", "Invalid value", and "must be one of": invalid CLI argument errors explained — this error's family across 35 libraries.

Related errors

• Invalid value for -distanceBin:
• Invalid feature name '
• args: treebankPath trainNums testNums
• Bad character encoding
• Bad process cp1252

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/536e212d44675358. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/parser/lexparser/Options.java:179

   * <li> <code>-printTT</code> print the training trees in raw, annotated, and annotated+binarized form.  Useful for debugging and other miscellany.
   * <li> <code>-printAnnotated filename</code> use only in conjunction with -printTT.  Redirects printing of annotated training trees to <code>filename</code>.
   * <li> <code>-forceTags</code> when the parser is tested against a set of gold standard trees, use the tagged yield, instead of just the yield, as input.
   * </ul>
   *
   * @param flags An array of options arguments, command-line style.  E.g. {"-maxLength", "50"}.
   * @param i The index in flags to start at when processing an option
   * @return The index in flags of the position after the last element used in
   *      processing this option.
   * @throws IllegalArgumentException If the current array position cannot be
   *      processed as a valid option
   */
  public int setOption(String[] flags, int i) {
    int j = setOptionFlag(flags, i);
    if (j == i) {
      j = tlpParams.setOptionFlag(flags, i);
    }
    if (j == i) {
      throw new IllegalArgumentException("Unknown option: " + flags[i]);
    }
    return j;
  }

  /**
   * Set an option in this object, based on a String array in the style of
   * commandline flags.  The option is only processed with respect to
   * options directly known by the Options object.
   * Some options (there are many others; see the source code):
   * <ul>
   * <li> <code>-maxLength n</code> set the maximum length sentence to parse (inclusively)
   * <li> <code>-printTT</code> print the training trees in raw, annotated, and annotated+binarized form.  Useful for debugging and other miscellany.
   * <li> <code>-printAnnotated filename</code> use only in conjunction with -printTT.  Redirects printing of annotated training trees to <code>filename</code>.
   * <li> <code>-forceTags</code> when the parser is tested against a set of gold standard trees, use the tagged yield, instead of just the yield, as input.
   * </ul>
   *
   * @param args An array of options arguments, command-line style.  E.g. {"-maxLength", "50"}.
   * @param i The index in args to start at when processing an option

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