A registry-only mount at /usr/local/cargo/registry left the package-cache lock under CARGO_HOME=/usr/local/cargo in each
container's own layer, so sibling containers (cargo-mutants stages, concurrent ygg-verify jobs) shared no lock and removed
each other's half-unpacked crate directories. Reproduced on Yggdrasil from an empty registry: 15 of 18 containers failed
with a registry mount, 15 of 18 with RUSTC_WRAPPER= too, 0 of 18 with the volume as CARGO_HOME.
ygg-verify.sh and cargo-mutants.sh mount eureka-cargo-home at /cargo-home and set CARGO_HOME and PATH for the rust image.
Removed: the retry without RUSTC_WRAPPER, its note and diag plumbing, and its two tests and the FAKE_CM_DEADWRAP switch.
Kept: container errors tail 25 lines.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Eureka
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