Constant MISMATCH_DIR_ENV 

pub const MISMATCH_DIR_ENV: &str = "UNLIT3D_SNAPSHOT_MISMATCH_DIR";

Available on crate feature snapshot and non-WebAssembly only.

The environment variable that collects mismatched frames on the host.

A mismatch is often the platform showing through rather than a regression: the stored frames come from one GPU stack, and another driver’s rounding can put a frame below the bar with nothing wrong. Writing the frame that did not match is what lets CI upload it as an artifact, so the difference can be looked at instead of guessed at from a score.

Unset, frames go under DEFAULT_MISMATCH_DIR. Set to a path, they go there instead — which is how a task that makes several passes gives each one its own directory.