Labs should use the pack they pick up before passing them.

[Tide]

Since Labs chained with inserters are becoming quite popular n 0.15 I thought I should bring up some behaviour that feels a little inefficient. As it is now, an inserter will grab a pack from a lab even if that lab can use the pack immediately. This causes a lag before the science actually gets started. It also stops interesting designs like circular chains, as the labs get stuck in a cycle of grab grab grab grab.

[DaveMcW]

interesting designs like circular chains

Circular chains are possible, just use filter inserters to make make sure none of the packs does a complete loop.

[Rseding91]

Since Labs chained with inserters are becoming quite popular n 0.15 I thought I should bring up some behaviour that feels a little inefficient. As it is now, an inserter will grab a pack from a lab even if that lab can use the pack immediately. This causes a lag before the science actually gets started. It also stops interesting designs like circular chains, as the labs get stuck in a cycle of grab grab grab grab.

That's partially by design: it means it's not the end-all most efficient way to fill labs with packs.

Either you setup more belts to feed everything or you deal with the inefficiencies of them flowing through the labs.