The atomic mv approach (kyssta-exe's commit) narrows but does not close the
#38249 race: the temp name used $$ (parent shell PID), which is identical
across &-launched concurrent subshells. Two concurrent writers pick the same
temp file, clobber each other mid-write, and mv then publishes a torn snapshot
— a reader sourcing it absorbs declare-x/export fragments into PATH.
- Use $BASHPID (actual per-subshell PID) so concurrent writers never collide.
- Chain mv on export success (&&) and rm the temp on failure so a partial dump
never replaces a good snapshot; apply the same to the init_session bootstrap.
- shlex-quote the static temp-path portion (Windows/spaces), $BASHPID outside.
- LocalEnvironment.cleanup sweeps orphaned snap.tmp.* temps.
- Regression tests: string-shape + a behavioral concurrent writers/readers test
that proves the snapshot never tears (would still tear with $$).
9f17f16c66