the canvas is transparent and this page is behind it. the scene renders at a fraction of the display resolution with a zero-alpha background, and the temporal path reconstructs coverage the same way it reconstructs color — from the sub-pixel jitter, integrated over frames. the thin cyan wires are the test: at 2x they are narrower than a render texel, so every alpha value along their edges is reconstructed rather than interpolated. switch the path to spatial and the same wires go soft, because FSR1 has no history to integrate. switch the backdrop to light to check the coverage against a bright page instead of a dark one. the canvas is transparent and this page is behind it. the scene renders at a fraction of the display resolution with a zero-alpha background, and the temporal path reconstructs coverage the same way it reconstructs color.
Alpha on the temporal path. Coverage is resolved by the accumulate pass with the same jitter-aware taps and blend weight as color, then stored in the locks buffer's spare alpha. Compare temporal vs spatial on the thin wires — and note the debug views are unaffected, since they write opaque output.