Constant KTSTR_KERNEL_LIST_ENV 

pub const KTSTR_KERNEL_LIST_ENV: &str = "KTSTR_KERNEL_LIST";

Name of the environment variable that carries the multi-kernel fan-out list across the cargo ktstr → cargo nextest → test- binary boundary. Format: label1=path1;label2=path2;… (semicolon entry separator, = separates label from absolute kernel-dir path). Empty / unset means “single-kernel mode” — the test binary honours KTSTR_KERNEL_ENV directly.

Set by cargo ktstr test --kernel A --kernel B (or any --kernel value that expands to ≥ 2 entries — repeated --kernel flags, or a single --kernel START..END range that expands to multiple stable releases via crate::kernel_path::KernelId::Range) before the exec into cargo nextest. Read by the test binary’s --list / --exact handlers in crate::test_support::dispatch to fan the gauntlet across kernels: each (test × scenario × topology × kernel) tuple becomes a distinct nextest test case so nextest’s parallelism, retries, and -E filtering work natively. Per-variant subprocesses re-export KTSTR_KERNEL to the kernel directory selected by the test name’s kernel_… suffix.

KTSTR_KERNEL_ENV is always set in tandem (to the first entry’s path) so downstream code that reads KTSTR_KERNEL directly — budget-listing’s vmlinux probe in dispatch.rs for example — still observes a valid kernel even when running under multi- kernel mode.

Single source of truth so the name is not spelled by hand at each reader; if the name ever changes, the change lands in one place instead of fanning out to every call site.