Upload failed (https://playground.bfl.ai)

[Alexcm19877891]

Hi, I am trying to use the playground and first day was working fine (https://playground.bfl.ai/) . However, since yesterday I can't upload anymore (im using kontext pro model ) as everytime when I try upload any image it says "upload failed". I tried restarting my computer, changed browser, clear cache.
Any ideas please?

[Alexcm19877891]

Hello, unfortunately no From: courtenaystars-cmd ***@***.***> Sent: 17 January 2026 04:24 To: black-forest-labs/flux ***@***.***> Cc: Alameda De Hercules Limited ***@***.***>; Author ***@***.***> Subject: Re: [black-forest-labs/flux] Upload failed (https://playground.bfl.ai) (Issue #503) [https://avatars.githubusercontent.com/u/255472399?s=20&v=4]courtenaystars-cmd left a comment (black-forest-labs/flux#503)<#503 (comment)> Did you ever get an answer to this? — Reply to this email directly, view it on GitHub<#503 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/BO4EWH7ZMAJUPOAQAVHDBDT4HG2ONAVCNFSM6AAAAACNY3BTO2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTONRSGYZTEMZRGQ>. You are receiving this because you authored the thread.Message ID: ***@***.******@***.***>>

[rehan243]

oh interesting, we hit something kinda similar with image uploads breaking after a model upgrade (kontext pro in our case too). Turns out, the playground was choking on file size limits and didn’t throw a proper error, just “upload failed” like you saw. We ended up patching our backend to expose max upload size in the UI, but for a quick test, try lowering your image size to under 2MB — that worked for us when Flux was running on AWS S3 with default configs.

Here's a sanity check pattern we used to catch this:

if image.size > 2 * 1024 * 1024:
    raise Exception("Image too big for upload")

Honestly, browser cache won’t matter if it’s backend-side. If downsizing doesn’t work, I’d poke at the API response using devtools and see if there’s a 413 or 500 coming back. The docs don’t mention it, but they sneakily changed limits after the last update.