### concurrent trigger
# Two isolated source trees (A and B) were supplied to independent helper builds sharing dist/helpers.
# The deterministic Zig fixture delayed A/Oliver and B/Boris to force overlap; the lipo fixture copied
# the generated helper markers into the shared output.
rm -rf /tmp/banal-race /tmp/banal-race-work
mkdir -p /tmp/banal-race/{A,B}/{oliver,boris} /tmp/banal-race-work/bin
touch /tmp/banal-race/{A,B}/{oliver,boris}/build.zig
cat > /tmp/banal-race-work/bin/zig <<'SH'
#!/bin/bash
set -u
prefix=
prev=
for arg in "$@"; do
  if [ "$prev" = "--prefix" ]; then prefix="$arg"; fi
  prev="$arg"
done
name="$(basename "$PWD")"
root="$(basename "$(dirname "$PWD")")"
if [ "$root" = A ] && [ "$name" = oliver ]; then sleep 0.3; fi
if [ "$root" = B ] && [ "$name" = boris ]; then sleep 0.3; fi
mkdir -p "$prefix/bin"
printf 'source=%s helper=%s target=%s\n' "$root" "$name" "${TARGET:-host}" > "$prefix/bin/$name"
chmod +x "$prefix/bin/$name"
SH
chmod +x /tmp/banal-race-work/bin/zig
cat > /tmp/banal-race-work/bin/lipo <<'SH'
#!/bin/bash
output="${@: -1}"
: > "$output"
for f in "${@:1:$#-1}"; do cat "$f" >> "$output"; done
chmod +x "$output"
SH
chmod +x /tmp/banal-race-work/bin/lipo
rm -rf dist/helpers
mkdir -p dist/helpers
(PATH="/tmp/banal-race-work/bin:$PATH" OLIVER_DIR=/tmp/banal-race/A/oliver BORIS_DIR=/tmp/banal-race/A/boris ZIG=/tmp/banal-race-work/bin/zig make helpers > /tmp/race-A.log 2>&1) & a=$!
(PATH="/tmp/banal-race-work/bin:$PATH" OLIVER_DIR=/tmp/banal-race/B/oliver BORIS_DIR=/tmp/banal-race/B/boris ZIG=/tmp/banal-race-work/bin/zig make helpers > /tmp/race-B.log 2>&1) & b=$!
wait "$a"; sa=$?
wait "$b"; sb=$?

### final output readback
A_exit=0 B_exit=0
dist/helpers/oliver: source=A helper=oliver target=host source=A helper=oliver target=host
dist/helpers/boris: source=B helper=boris target=host source=A helper=boris target=host source=B helper=boris target=host source=A helper=boris target=host
tmp_files=none

### source publication path
# Scripts/helpers.sh:73-84 uses a private compiler directory but publishes each lipo result to the
# shared $HELPERS/$name.tmp and then moves it to shared $HELPERS/$name.
tmp="$(mktemp -d)"
if (cd "$src" && "$ZIG" build --prefix "$arm" -Doptimize=ReleaseSafe -Dtarget=aarch64-macos) &&
  (cd "$src" && "$ZIG" build --prefix "$x86" -Doptimize=ReleaseSafe -Dtarget=x86_64-macos); then
  if [ -f "$arm/bin/$name" ] && [ -f "$x86/bin/$name" ] && lipo -create "$arm/bin/$name" "$x86/bin/$name" -output "$HELPERS/$name.tmp"; then
    mv "$HELPERS/$name.tmp" "$HELPERS/$name"
  fi
fi

# Scripts/helpers.sh:90-103 can also copy or remove the same shared final path during host fallback.
cp "$tmp/bin/$name" "$HELPERS/$name"
...
rm -f "$HELPERS/$name"

# Scripts/helpers.sh:107-117 processes oliver and boris independently, without an invocation-level lock
# or pair-level publication. Makefile:33-35 exposes this script directly as `make helpers`.
for tool in oliver boris; do
  ...
  build_helper "$tool" "$src"
done

### final result
# final result: BF-RACE-1 failed. Both concurrent commands returned success, but the shared Boris output
# contains provenance from both source trees while Oliver and Boris were published independently.