Telegram sendAudio for a Sume track: URL 20 MB, upload 50 MB

To send a finished Sume music track to a Telegram chat, call sendAudio with the artifact URL as the audio value. Telegram's Bot API says that a file fetched from an HTTP URL can be at most 20 MB, and that an upload by multipart form can be at most 50 MB. A Music Router track is usually audio/mpeg on media.sume.com, so check the byte size and choose the route.

The three ways to pass the file

The audio parameter accepts a file_id, an HTTP URL or a multipart upload.

Send by URL, keep the file_id

Start the job in the default async mode, read the audio artifact when the envelope is terminal, and send the URL. The Music Router costs a fixed $0.125 per generation and has no duration field, so most tracks are small; check anyway with a HEAD request.

import json, os, urllib.request

def send_audio(chat_id: int, url: str, title: str) -> str:
    head = urllib.request.Request(url, method="HEAD")
    size = int(urllib.request.urlopen(head, timeout=10).headers["Content-Length"])
    if size > 20 * 1024 * 1024:
        raise ValueError("over the 20 MB URL limit: upload the bytes instead")
    body = {"chat_id": chat_id, "audio": url, "title": title}
    req = urllib.request.Request(
        "https://api.telegram.org/bot%s/sendAudio" % os.environ["TELEGRAM_BOT_TOKEN"],
        data=json.dumps(body).encode(),
        headers={"Content-Type": "application/json"})
    reply = json.load(urllib.request.urlopen(req, timeout=30))
    return reply["result"]["audio"]["file_id"]

Why keep the file_id

Telegram recommends a file_id for a file that already sits on its servers. Store the id returned by the first send and reuse it for later chats; then Telegram does not download the file from Sume again. Keep the Sume job id with it so the track can be traced.

Limits

The Telegram page that I read says nothing about how long a track may be, so do not promise a duration. The URL must be reachable by Telegram's servers without your Sume API key, which is why the public artifact link is used and not a status URL. If the send fails, read the error text from the reply before you retry, and do not start a second generation just because Telegram failed; the first job is already paid and its artifact is still there.