elastic/elasticsearch · error · IllegalArgumentException

Unknown token type: '{}', must be one of {}

Error message

Unknown token type: '{}', must be one of {}

What it means

Error "Unknown token type: '{}', must be one of {}" thrown in elastic/elasticsearch.

Source

Thrown at modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/NGramTokenizerFactory.java:75

                    continue;
                }
            }
        }
        MATCHERS = unmodifiableMap(matchers);
    }

    static CharMatcher parseTokenChars(Settings settings) {
        List<String> characterClasses = settings.getAsList("token_chars");
        if (characterClasses == null || characterClasses.isEmpty()) {
            return null;
        }
        CharMatcher.Builder builder = new CharMatcher.Builder();
        for (String characterClass : characterClasses) {
            characterClass = characterClass.toLowerCase(Locale.ROOT).trim();
            CharMatcher matcher = MATCHERS.get(characterClass);
            if (matcher == null) {
                if (characterClass.equals("custom") == false) {
                    throw new IllegalArgumentException(
                        "Unknown token type: '"
                            + characterClass
                            + "', must be one of "
                            + Stream.of(MATCHERS.keySet(), Collections.singleton("custom"))
                                .flatMap(x -> x.stream())
                                .collect(Collectors.toSet())
                    );
                }
                String customCharacters = settings.get("custom_token_chars");
                if (customCharacters == null) {
                    throw new IllegalArgumentException("Token type: 'custom' requires setting `custom_token_chars`");
                }
                final Set<Integer> customCharSet = customCharacters.chars().boxed().collect(Collectors.toSet());
                matcher = customCharSet::contains;
            }
            builder.or(matcher);
        }
        return builder.build();

View on GitHub (pinned to db6a809a66)

When it happens

Trigger: Thrown at modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/NGramTokenizerFactory.java:75 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of elastic/elasticsearch@db6a809a66 (2026-08-12). Data as JSON: /api/errors/3d2ea8d56836483f. Report an issue: GitHub.