Tears of the Kingdom
The Smithing Construct was, by its own words, created by Mineru in the era of Hyrule's founding as an experiment to "unlock the hidden potential of Zonai charges" with "the unique ability to temper zonaite for weapons and equipment". Having hidden when the Seized Construct took over the Spirit Temple, it emerges along with a Mining Construct when Mineru and Link destroy the Seized Construct and retrieve Mineru's Secret Stone.
While it says it would "not ordinarily work for anyone other than Mineru", it calls Link a "special case" and agrees to work for him at the cost of the zonaite required to make the weapons:
|Mighty Zonaite Sword||1||45|
|Mighty Zonaite Longsword||1||60|
|Mighty Zonaite Spear||1||30|
|Mighty Zonaite Shield||1||45|
(Note that, by the time Link has completed the Spirit Temple, it is likely that the World Level will have upgraded the Zonaite Swords, Zonaite Longsword, Zonaite Spear and Zonaite Shield lying freely in Zonaite Forge Island to their Mighty equivalents, which respawn with every Blood Moon along with a Mighty Construct Bow.)