kestra-io/kestra · error · PebbleException

Invalid regex ''{0}'': {1}

Error message

Invalid regex ''{0}'': {1}

What it means

Thrown by the 'regexReplace' Pebble filter when `Pattern.compile(regex)` raises a `PatternSyntaxException`. The message embeds the bad pattern and the JDK's description so you can locate the syntax fault.

Source

Thrown at core/src/main/java/io/kestra/core/runners/pebble/filters/RegexReplaceFilter.java:73

                self.getName()
            );
        }

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

        String regex = args.get(ARGUMENT_REGEX).toString();
        String replacement = args.get(ARGUMENT_REPLACEMENT).toString();
        try {
            return RegexUtils.matcher(Pattern.compile(regex), input.toString()).replaceAll(replacement);
        } 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 metacharacters in Pebble: `\\.`, `\\d`, `\\s`.
2. Test the pattern in a Java regex tester first.
3. For complex patterns, store them in a variable/input to escape once.

Example fix

# before
{{ url | regexReplace(regex="\.com", replacement=".org") }}
# after
{{ url | regexReplace(regex="\\.com", replacement=".org") }}

# Double-escape in Pebble literals:
{{ s | regexReplace(regex="\\.", replacement="_") }}
# Validate the pattern in a script task:
# Pattern.compile(userPattern);

When it happens

Trigger: Unbalanced parentheses, illegal quantifiers, malformed character classes, or backslash escaping issues induced by Pebble's string parsing.

Common situations: Writing `\.` in a Pebble literal (becomes `.`); copying a regex from JS/Python without re-escaping; using unsupported constructs.

Related errors

• Invalid regex '{0}': {1}
• Invalid regex '{0}': {1}
• The argument ''{0}'' is required.
• RegexTimeoutException: e.getMessage()
• The 'escapeChar' filter expects an argument 'type'.

AI-assisted analysis of kestra-io/kestra@823fada927 (2026-08-14). Data as JSON: /api/errors/b748b95028dd281d. Report an issue: GitHub.