A relay MUST include all Extension Headers associated with a Track when sending any PUBLISH, SUBSCRIBE_OK, REQUEST_OK when in response to a TRACK_STATUS, or FETCH_OK, unless allowed by the extension's specification (see Section 2.5).
§8.6.
Relay Track Handling
This is one section of the MoQT specification, rendered per-section for quick reference and citation. The authoritative text is draft-ietf-moq-transport-16 at the IETF.