21 August 2026
Extensibility
API Extensions now include additional API HTTP response headers that improve observability and help you monitor and troubleshoot your Extensions.
The following API HTTP response headers are now available, in addition to the existing
X-Correlation-ID header:ct-upstream-status-code: present when the HTTP status is 400 or higher, indicating that API Extension errors occurred (for example, caused by an Extension failure). The header is not present if there were no API Extension errors.Server-Timing: contains the duration in milliseconds of the API Extension call. The header has one entry per API Extension call with its duration, plus a total entry for the overall external call time. It follows the W3C Server-Timing format.
For additional observability information about API Extensions, see API Extensions observability.