The part that eats our time isn't the OAuth dance, it's the media. We push the same daily batch to Telegram, Threads, Instagram, LinkedIn, X and TikTok for an iGaming job board, and every platform fails differently: TikTok choked on an ICC colour-profile atom our encoder was writing and rejects anything past ~10 MB, Instagram carousels have to be 4:5 or the text gets cropped off the card, Telegram takes whatever you hand it. "Media is uploaded once and reused across platforms" only saves us if something in the middle re-encodes per target, otherwise we keep the six render paths we already have and just move the failures behind your API. When a file trips a platform's media validation, does PostZen normalise it to that platform's spec, or does the webhook hand back the upstream error for us to fix and retry?