Pebble template syntax and filters in Flow Designer

Verified 2026-09-15 · 10 claims · sources tier 2

Also known as Pebble, Pebble Templates, epoch filter.

Flow Designer input fields use the open-source Pebble Templates expression syntax, and the source article names no version of it 4. The documentation names 10 operator symbols, 2 filters, and 1 function of the expression language, delegating the rest to an external wiki 1.

Syntax and usage rules

Cisco instructs that single quotes be used instead of double quotes inside an expression and gives no reason for this rule 8. An expression written without its double curly braces throws a flow error, though the documentation states this for the Condition activity only 5. A text-to-speech message of more than 1 line requires a Pebble escape filter for the system to play it 6.

For date and time values, Cisco instructs that the now function not be used to obtain the current time in milliseconds because it uses a simple date format, directing the author to the epoch filter instead 7. In certain activity configurations, 2 unrelated expression syntaxes coexist: the Pebble double-brace form for flow variables and a JSON path form for parsing a response body 9. In the field, Cisco advises against complex expressions when configuring multiple variables in 1 Set Variable activity, but defines neither complex nor the consequence 2.

Validation and error behavior

Flow validation checks expressions for structural errors only and cannot evaluate a function or check that a variable resolves to the expected value 10. An invalid expression surfaces either as design-time error code FC1009 or as a system error during execution of the Set Variable activity, and the documentation never relates the 2 failure surfaces 3.

See also

See also Webex Contact Center Flow Designer architecture. See also The Webex Contact Center Flow Designer activity set. See also The Flow Designer failure code vocabularies.

Applicability

Across the claims in this article, the evidence covers Cisco Webex Contact Center, verified as of 2026-09-15. The deployment model is not covered by any claim in this article.

What remains uncertain

Which logic operators the expression language supports is not covered by any claim in this article. What makes an expression invalid at design time is not covered by any claim in this article. Whether the missing-brace error applies outside the Condition activity is not covered by any claim in this article. Which Pebble release the platform runs is not covered by any claim in this article.

WarmTransfer. (2026, September 15). Pebble template syntax and filters in Flow Designer. WarmTransfer. https://warmtransfer.net/knowledge/pebble-template-expressions

@misc{warmtransfer-pebble-template-expressions,
  title  = {Pebble template syntax and filters in Flow Designer},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/pebble-template-expressions},
  note   = {Verified 2026-09-15}
}