A print sliced against a Virtual Printer carries use_ams=false — a VP
advertises no AMS, so the slicer sends it and VP intake stamps it on the
queue item. But an "Any [model]" item is colour-matched to a real printer
at dispatch, resolving a real AMS slot in ams_mapping. The command builder
only ever forced use_ams off (all-external) and never back on, so the stale
false shipped with a real-tray mapping and the printer aborted at layer 0 on
the empty external spool.
For single-nozzle printers the mapping is now authoritative: a real tray
(0-253) forces use_ams=true, explicit external (254/255) forces it false,
and an unresolved -1 does neither (preserving the #2589 contract).
Dual-nozzle is untouched — use_ams is nozzle routing there. The correction
sits at the single command-builder choke point, covering the VP, queue, and
manual paths.
maziggy
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