are you getting an error that looks like this?
[{'type': 'Body', 'errors': {'issues': [{'code': 'invalid_type', 'expected': 'number', 'received': 'string', 'path': ['content_length'], 'message': 'Expected number, received string'}], 'name': 'ZodError'}}]
you are sending a numeric string as content_length in the attachment start request. we don't accept that anymore (we weren't supposed to accept it ever but that was a longstanding bug that got inadvertently fixed when we did other shit). make sure you're sending the body as a json object instead of form encoded or whatever.
(python requests defaults to form encoded for some reason, changing from data=whatever to json=whatever is sufficient to unbreak it unless you have other shit going on)
