Preinstall probed absent or non-executable PATH Node candidates, creating Node spawn attempts during Bun-only installs. The smoke also omitted the documented Bun launcher marker and masked the resulting failure with an install-time Node fallback.
Check execute permission before probing persistent Node candidates, preserve Node engine enforcement and Bun lifecycle-shim exclusion, and make the smoke install through the documented Bun 1.4+ launcher without a Node fallback. Remove the resolved expected blocker.
Proof: 132 focused preinstall, spawn-ledger, and install-smoke workflow tests pass after a patch-identical rebase. The reviewed Linux Bun-only smoke passes all ten steps with zero preinstall Node attempts and no fallback; both classifier negative controls reject invalid blocker inventories.
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