kestra-io/kestra · error · PebbleException

Invalid regex '{0}': {1}

Error message

Invalid regex '{0}': {1}

What it means

Thrown by the 'regexMatch' Pebble filter when `Pattern.compile(regex)` fails with a `PatternSyntaxException`. The message includes the bad pattern and the JDK's description of the syntax error.

Source

Thrown at core/src/main/java/io/kestra/core/runners/pebble/filters/RegexMatchFilter.java:64

    public Object apply(Object input, Map<String, Object> args, PebbleTemplate self, EvaluationContext context, int lineNumber) throws PebbleException {
        if (input == null) {
            return false;
        }

        if (args.get(ARGUMENT_REGEX) == null) {
            throw new PebbleException(
                null,
                MessageFormat.format("The argument ''{0}'' is required.", ARGUMENT_REGEX),
                lineNumber,
                self.getName()
            );
        }

        String regex = args.get(ARGUMENT_REGEX).toString();
        try {
            return RegexUtils.matcher(Pattern.compile(regex), input.toString()).find();
        } catch (PatternSyntaxException e) {
            throw new PebbleException(e, MessageFormat.format("Invalid regex ''{0}'': {1}", regex, e.getDescription()), lineNumber, self.getName());
        } catch (RegexUtils.RegexTimeoutException e) {
            throw new PebbleException(e, e.getMessage(), lineNumber, self.getName());
        }
    }
}

View on GitHub (pinned to 823fada927)

Solutions

1. Double-escape in Pebble: `\\d`, `\\w`, `\\s`.
2. Validate the pattern in a Java regex playground.
3. Move complex patterns into a flow variable or input to reduce escaping churn.

Example fix

# before
{{ s | regexMatch(regex="\d{3}") }}
# after
{{ s | regexMatch(regex="\\d{3}") }}

# Double-escape backslashes in Pebble literals:
{{ s | regexMatch(regex="\\d{3}") }}
# Validate in a script task first:
# Pattern.compile(userPattern);

When it happens

Trigger: Malformed regex (unbalanced groups, illegal quantifiers, bad escapes); most commonly a backslash escaping problem caused by Pebble's own string parsing consuming one level of backslashes.

Common situations: Writing `\d` in a Pebble literal (becomes `d`); copy-pasting a regex from another language; using POSIX classes or constructs the JDK does not support.

Related errors

• Invalid regex '{0}': {1}
• Invalid regex ''{0}'': {1}
• The argument 'regex' is required.
• The 'escapeChar' filter expects an argument 'type'.
• The 'escapeChar' filter expects the value of 'type' to be ei

AI-assisted analysis of kestra-io/kestra@823fada927 (2026-08-14). Data as JSON: /api/errors/90705e5dae86ca56. Report an issue: GitHub.