OptionalbodyOptionalheadersOptionalkeepaliveOptionalmetaSeed the request context meta bag (carried to response/error interceptors).
OptionalmethodOptionalparamsOptionalsignalBind the request to a caller's own lifetime. Combined with the client's timeout rather than replacing it — whichever fires first aborts.
Let the request outlive the page (
fetch(..., { keepalive: true })), for a last report onpagehide. Small bodies only (browsers cap keepalive bodies at 64 KB).