temporalUpscale

The settings behind the reconstruction, and the switch that starts it.

local Upscale = require("@builtin::systems.temporalUpscale.temporalUpscale")

Upscale.enable({ renderScale = 0.5 })   -- render at half, present at full
Upscale.enable({ sharpness = 0.5 })     -- retune; omitted fields keep their value
Upscale.get()                            -- what is in force, incl. the live scale
Upscale.active()                         -- whether the pass is running
Upscale.disable()                        -- release the pass

field	effect
historyWeight	How much of the accumulation to keep each frame. Higher resolves more and settles smoother; it also takes longer to let go of what a surface used to look like.
neighbourhoodClamp	How far outside the current frame's own colour spread an accumulated sample may sit before it is pulled back in.
sharpness	How much of the edge lost to averaging — and to the interpolation that brought the frame up to size — is added back.
motionRejection	How much fast motion shortens the memory, which is what keeps a moving object from trailing behind itself.
renderScale	The fraction of the display's resolution the scene rasterizes at. Omit to leave it wherever it is.

enable moves the render scale only when you pass renderScale, so a dynamic-resolution controller (@builtin::systems.renderScale.renderScale) keeps steering it while the reconstruction runs.