Forge cannot use multipart/form data

I now use Forge custom UI to call the interface of the last file of Slack. I encounter the following problems. How can I solve them? It is urgent to solve it now!!! Greenting and Thanks!

The code is as follows:


The error is reported as follows:


There’s a good chance you’ve run into Forge’s multipart/form-data problem: [FRGE-114] - Ecosystem Jira.

It might be worth trying to use application/x-www-form-urlencoded (which I think the Slack API supports) because this does work with fetch from forge/api.

When will the multipart/form data mode in Forge be available? At present, application/x-www-form-urlencoded is feasible.

The most recent update we have from Atlassian is on that ticket, which indicates it won’t be soon.