Most of this pipeline automates cleanly: pulling your clips, cropping to vertical, burning captions, and scheduling the upload. What does not automate is choosing which clip is worth posting and where the hook starts inside it, so the realistic setup is automatic after a person picks. If you want zero human steps, you are trading quality for volume, and it is worth knowing which quality you are giving up.
Which parts actually automate
Getting the files is solved, since your own clip list is available through Twitch's API and clip pages resolve to downloadable video. Cropping is solved in the mechanical sense: a tool can center the frame or track a face and render 9:16. Captioning is solved well enough that the remaining work is fixing names and game terms. Scheduled posting is solved by the destination platform's own upload API. None of those four steps needs to understand the clip, which is exactly why they automate.
Three routes, and what each costs
A clip-to-Shorts subscription tool is the fastest path: connect accounts, pick a template, and it reframes, captions, and posts on a schedule. You pay monthly and you inherit its crop logic, and free tiers generally add a watermark or a cap. A scripted pipeline (one API call for your clip list, an open source encoder for the crop and pad, an open source speech model for captions, an upload call at the end) takes a day or two to build and stays cheap as volume grows, but you own every breakage and every quota error. Doing it by hand stays the best option for the clip you actually care about, and it is the only route where the vertical crop follows the meaning of the shot. Going straight from a full VOD instead of from clips adds one more unsolved step, which is finding the moment at all.
Where automation breaks on stream footage
The crop is the usual failure. Face tracking on gameplay throws away the minimap and the killfeed, which is often the thing that made the clip land. Loud is not the same as good, so a tool that picks by audio peaks hands you the same kind of reaction every week. Captions on game audio drop proper nouns constantly, and that reads as careless on a channel where the audience knows every name. A fixed layout with gameplay on top and your camera below survives most of this, at the cost of a smaller picture.
Picking the clip, and finding the hook inside it
This step stays yours, and it is the one where a search layer helps more than an editing tool. You describe the moment you remember and get back openable time ranges instead of a timeline to scrub. Search mode changes the answer: on short videos a fast pass tends to come back with whole clips that are probably relevant, and pinpointing the few seconds where something appears takes the slower precise pass, which you wait on. Vivu does that part on footage you have uploaded to a project yourself, so a Twitch link is not an input and neither is a whole channel. It hands back the original clip to export, which means reframing and captions still happen wherever you already do that work.
When this is not worth automating
If you post two or three Shorts a week, a saved export preset plus manual upload beats maintaining a pipeline. If your clips are already 30 seconds with the hook at the front, the only automation you need is the preset. And if what people follow you for is the commentary rather than the visuals, handing the selection to a tool costs you the thing that makes the channel work.
How to decide
Count how many clips you would post in a month if posting were free. Under a dozen or so, automate the export and keep the choosing manual, because the choosing is where the value is and the export is where the tedium is. Above that, a pipeline pays for itself, and the real question becomes which quality you give up first. For most channels the crop goes before the captions, because viewers forgive an awkward frame and read bad captions as effort you did not make.
FAQ
Can I automate this without paying for a tool?
Yes, if you are willing to write a small script. Your clip list and your uploads are both reachable through the two platforms' APIs, and the cropping, padding, and caption burn-in can all be done with open source command line tools. The work is a day or two up front plus maintenance whenever an API changes or a token expires. What you cannot get free is a good automatic crop, because that is the part where the paid tools are actually doing something hard.
Why does the automatic crop cut off the part that matters?
Because it is following a face or the loudest region, not the meaning of the frame. In gameplay the informative pixels are often in a corner, so a centered or face-tracked 9:16 crop drops them. The fix is a layout rather than a smarter crop: put the game in the upper portion at its original aspect ratio and your camera below, and accept a smaller picture. For face-cam-only moments, the automatic crop is usually fine.
Do I need permission to post a clip a viewer made of my stream?
The broadcast is yours, and re-posting clips of your own stream is the normal case. Two things are worth checking anyway. If the clip contains someone else's material, such as a video you were reacting to or licensed music, that part is a separate rights question and it travels with the clip to the new platform. And Twitch's own terms govern how clips can be exported and used, so read those rather than relying on what is customary.
Does a Shorts tool need my video file, or just my channel link?
It depends on what the tool does. A publisher only needs a rendered file. Anything that crops, captions, or looks inside the video needs the actual media, which means either downloading from a link it is allowed to fetch or having you upload it. Tools that advertise "just paste a link" are still fetching and storing a copy, so if the footage is sensitive, that is the question to ask before the pricing one.