It had a burst of constructions bots creeping right after map load, then nothing for the last ten or so minutes. I have ~1000 idle construction bots (well, I have 1000, and they're all idle).

Same here. I installed this onto a save and they worked quite a bit, i didnt notice how long. Once I saw they started doing it I went and did other things came back some time later and they were still doing it in other areas, then at one point I noticed they had stopped. All of my roboports are connected logistic networks and i have PLENTY of concrete haha.

I think I fixed the problem. Testing my changes for 0.9.5 which has some optimizations also seems to have fixed this issue. The update to 0.9.5 should reset all roboports back to trying to fill their area, but if they don't (and this works in 0.9.4 too) you can also remove the roboport and place it down again. Or disable the mod, load a game, save, quit, re-enable the mod, and load again.

Ah, time to update and check... as soon as you uploaded and it shows up, that is :D

I did notice (since the original comment) that newly-placed ports started creeping. Like mad. With UPS dipping to about 30 (I do get almost 60UPS in most areas otherwise, and that's with a 2GB Factorio process :P). Like, filling all the area right away.

But I'm sure I've placed some ports in the same map, after the stoppage, and those ports didn't "immedicreep".

And... just now noticed it filling one farther. That is, it placed ghosts over the whole construction area of a newly placed port, and then one tile more outside the construction area. Looks like an off-by-one error somewhere ;-) But need to test .5 first to check.

Been fiddling with the tuning so the release isn't out yet. In testing I found sometimes trees would get marked but be out of reach. Which is annoying but I'm not sure how to properly filter trees. All in all it seems to work well so I'll go ahead and publish the new version.

Before your latest release, I had tried to fix tis by doing as you said above but that didn't work for me. Also since your release it also did not spark bots to start laying concrete.

Every time the mod updates, every roboport will try to start creeping with radius 0 and it only checks 4 roboports per second. So depending on how many roboports you have, it might be a while before they expand and find areas that need don't have concrete yet.

Thanks, I'll give it another shot and be more observant. Thanks for your help and hard work Mylon!