The :bg test family wrote to fixed /tmp paths (test-electron.log, its .exit/.pid siblings, test-spec, test-grep-pattern). Two worktrees — or a worktree and the primary checkout — running the gate at the same time silently overwrote each other's output, so a run could report another checkout's result. scripts/tagged-path.sh derives a suffix from the calling checkout's own worktree root (basename of `git rev-parse --show-toplevel`) and prints the tagged path for a given basename, so the path is deterministic from repo location alone — no environment variable has to be set or exported for it to resolve, unlike ${TMPDIR:-/tmp} alone. apps/desktop/package.json's :bg scripts and test:log now resolve their paths through it; scripts/bg-run.sh stays path-agnostic. Docs citing the old literal /tmp/test-electron.log path are updated to point at yarn test:log / scripts/tagged-path.sh instead. Claude-Session: https://claude.ai/code/session_017eGkdjW7RoMwGCssQpLgfS