Hi Duncan, if I try a simple model like yours above, it works in most cases (I ran it four times with different inputs, only once it defaulted back to the inputs cell size). But when I try to set up my more complicated model, even if it seems to remember the cell size, once I run it, the processing runs with the resolution of the input mosaic, which is 1m cell size.
I tried using MosaicToNew Raster, but that tool doesn't process all the rasters in the mosaic, some are left out in the output (another bug I found other people complaining about), so it's useless. Now I'm trying CopyRaster…...