aiohttp 3.14.4 fixes truncated retried file bodies: Sume submits

If you submit a Sume job with aiohttp, build the JSON body in memory and pass the bytes, and upgrade to aiohttp 3.14.4. That release fixed a bug where an internally retried request sent a truncated body when the request data was a file object. A Sume submit body is a few hundred bytes, so there is no reason to hand aiohttp an open file at all.

What 3.14.4 fixed

The aiohttp changelog (read 2026-10-10) dates 3.14.4 to 2026-10-04; the GitHub release page shows the same notes. The items that touch a client calling Sume are below.

Why a cut-off body is worse than an error

A JSON body that stops halfway is not valid JSON. The errors page lists 400 invalid_request for a body that is not valid, so the good outcome is a clean rejection. The risky case is a retry that you cannot see: your code made one call, the library made two, and you now have to reason about whether the first one created a job.

That is what Idempotency-Key is for. The jobs page says to send the same key on a retried submit so the retry returns the original job instead of billing a second one. Pair that with a body that cannot be half-read.

import asyncio
import json
import os

import aiohttp

URL = os.environ.get("SUME_URL", "https://api.sume.com/v1/videos")


async def main() -> None:
    payload = {"model": "seedance-2.5", "prompt": "비 오는 서울 골목", "duration": 5}
    body = json.dumps(payload, ensure_ascii=False).encode("utf-8")  # bytes in memory
    headers = {
        "Authorization": f"Bearer {os.environ['SUME_API_KEY']}",
        "Content-Type": "application/json",
        "Idempotency-Key": os.environ["RUN_KEY"],  # same key on every retry
    }
    async with aiohttp.ClientSession() as session:
        async with session.post(URL, data=body, headers=headers) as resp:
            job = await resp.json()
            print(resp.status, job.get("id"), job.get("polling_url"))


asyncio.run(main())

Notes on the sample

The request shape follows the video docs: model, prompt, and an integer duration, with the response carrying id and polling_url. I ran the script on aiohttp 3.14.4 against a local stub and it printed the status, job id, and polling URL.

• Encode once with ensure_ascii=False and .encode("utf-8"). The Content-Type header says application/json, and the bytes are the same on a retry.
• Read the key from the environment or from your job table. Do not generate a new UUID inside the retry loop, because a new key is a new paid job.
• Poll polling_url afterward. Do not submit again because a local timeout fired.
• If you really must upload a large file elsewhere, UploadTracker is the new way to watch progress. Sume's generation endpoints take public HTTPS URLs for media, so a Sume submit does not need it.

Pin aiohttp>=3.14.4 in the service that talks to Sume. The fix is in the library, but the habit of sending bytes you built yourself works on every version.