Concerns: pushword/core
A worker batch was sized as the stale count divided by the worker count, with no ceiling, and travels as a single element of argv — which Linux caps at 128 KiB per argument however generous ARG_MAX is. Past a few thousand stale medias the command died on posix_spawn(): Argument list too long before the first image. Batches are capped at 200 now, and a worker is killed after five minutes without output rather than five minutes in total, which a large batch used to hit by construction.
Affects sites running pw:image:cache with --parallel above 1 on a large media library — including bin/setup --full, which failed the same way. Nothing to do: re-run the command. The sequential path (--parallel=1, and the auto default on fewer than 8 cores) never built an argv and was never affected.