--assemble

--assemble is a boolean transform flag, defaulting to false. When set, after all input model files have been loaded, the slicer iterates over every loaded model and every object within each model, collecting all volumes. Those volumes are added into a single new object named "Assembly", which is given one instance. The result replaces the entire model list: from that point forward the slicer sees one model containing one object.

For each collected volume, the extruder assignment is taken from the **parent object's** extruder configuration and written onto the new volume — the volume's own prior extruder config is overwritten. This means separate files that were loaded as separate objects, each assigned to a different filament slot, contribute their volumes with the correct per-object filament, so per-object filament differentiation across the original file set is preserved. However, per-volume extruder distinctions within a single original object (such as those produced by color painting, where individual volumes carry different extruder values) are not preserved: all volumes from one original object receive that object's single extruder value, collapsing any within-object per-volume color distinctions.

The flag belongs to the transform pipeline, which runs after loading. It composes with other pre-slice transforms (orientation, unit conversion, etc.), and the merge itself is unconditional: every piece of geometry the CLI loaded becomes a volume inside that single object. Per-object print-parameter overrides from the original objects are lost after the merge because the separate objects no longer exist.

--assemble cannot be combined with --clone-objects. The CLI validates this and exits with an invalid-params error if both are present. It is also distinct from --load-assemble-list, which is an alternative model-loading strategy driven by a JSON spec; that flag cannot be combined with input model files (the CLI exits with an invalid-params error if it is).