WebGPU's spec currently indicates:

During presentation, the chrominance of color values outside of the [0, 1] range is not to be clamped to that range; extended values may be used to display colors outside of the gamut defined by the canvas' color space’s primaries, when permitted by the configured format and the user’s display capabilities. This is in contrast with luminance, which is to be clamped to the maximum standard dynamic range luminance.

This is a very good default behavior, but some applications may want to use extended-range brightness.

The following proposal provides a mechanism for opting in to extended-range brightness.
https://github.com/ccameron-chromium/webgpu-hdr/blob/main/EXPLAINER.md