--scale

--scale accepts a single positive floating-point multiplier and applies it uniformly across all three axes of every object in every loaded model. A value of 1.0 is the identity (no change); 1.5 makes each dimension 150% of its original size; 0.5 halves it. The default when the flag is omitted is 1.0. Any value that is zero or negative causes the CLI to log an invalid-params error and exit immediately with a non-zero status code -- the slice is never started.

The transform is applied directly to the mesh volumes of each object, not to placement instances. This means the change in size is baked into the geometry before arrangement, bed-fit checks, and slicing run. Because --scale is classified as a transform, it is collected in command-line order alongside --rotate, --rotate-x, --rotate-y, and other active transform flags such as --arrange and --orient, and the entire transform list is replayed in that order before slicing begins. The sequence you pass on the command line is therefore meaningful: --rotate 45 --scale 1.5 and --scale 1.5 --rotate 45 produce identical results for uniform scale (since uniform scaling commutes with rotation), but if you are composing multiple transforms it is worth being deliberate about order.