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Configurations in which an inserter places items on belts directed towards the inserter or away from it cannot be exactly mirrored due to inserters lacking true flipping behavior. This then requires manually fixing problems after flipping or having to deliberately predict these problems and restrict own building choices.
Expected result:
- ideally, any configuration which can be flipped should function exactly as the original right out of the gate,
- if it's not possible to implement true flipping for inserters, then flipping the problematic configurations should either be blocked or produce a warning.

That is not a bug, items land on the right side of the belt in direction of flow.

I'm quite aware of how it works. And the way it works causes some setups to break when flipped. This is fundamentally not expected behavior - ergo, a bug.

MKMoose wrote: Thu May 28, 2026 8:43 amI'm quite aware of how it works.

You are looking for the "Rotate" function (press the R key), which has existed in the game for much longer than Flipping, and preserves lefty-righty-ness (Edit: chirality is the word I was looking for, thank you computeraddict ) of Inserter-Belt-lane setups like this.

Good Luck!

MKMoose wrote: Thu May 28, 2026 8:43 am I'm quite aware of how it works. And the way it works causes some setups to break when flipped. This is fundamentally not expected behavior - ergo, a bug.

Don't change the chirality of setups that rely on chirality. There's no way to do what you want without breaking other things or adding complexity to inserters.

eugenekay wrote: Thu May 28, 2026 7:33 pm You are looking for the "Rotate" function (press the R key), which has existed in the game for much longer than Flipping, and preserves lefty-righty-ness (Edit: chirality is the word I was looking for, thank you computeraddict ) of Inserter-Belt-lane setups like this.

If I was looking for the rotate function, then I would have used it, but interestingly, you might notice that the rotate function actually does not produce the same result as flipping.

The problem was that I specifically needed to flip a blueprint, and the current flipping behavior for inserters works the same way as a 180° rotation. After a bunch of debugging to find what actually went wrong, I ended up having to either make two near-identical setups with the belts fixed in the second configuration, or redoing the base setup in a less space-efficient way to no longer break when flipped.

Having experienced flipping being blocked when a building cannot be flipped (e.g. a train stop) and having read FFF#394 which includes a mention of how flipping is now a first-class operation that works anywhere it feels natural, I did not expect something as basic as an inserter to break when flipped with no warning.

computeraddict wrote: Thu May 28, 2026 8:58 pm Don't change the chirality of setups that rely on chirality. There's no way to do what you want without breaking other things or adding complexity to inserters.

Oh no! There's no way to do what I want without doing what I want!

Of course it would increase the complexity of inserters. There's no way to allow them to choose whether they drop items on the left or right without allowing them to do just that (and to be clear, not close-far choice - just left-right). It would likely be a purely optional checkbox, just like filters, stack size override and spoiled priority. And it wouldn't even break anything.

Not enabling inserters to configure their drop side is probably an intended game challenge. It's a trade-off between simplicity and functionality. A certain level of simplicity is required to accommodate beginners and a larger player base in general.

Example: many circuit users from the community would like to have the feature to select red/green wire for every output everywhere, similar to as it is already possible for combinator input. Would be a big and useful feature. However, in case the devs don't implement this because they deem it not simple enough any more, I would fully accept this as valid reason.

This kind of feature creep is dangerous. It might put new players off, because it might overwhelm them.

Make a feature request if you want to discuss this further.