A coordinator agent spawned a subagent with a prompt stating "you are running in a cloud environment" to run a long data job (3 GB HTTP read of parquet row groups, 30-90 min) as a parallel hedge next to its own local run. The subagent actually ran in a local git worktree on the same 16 GB laptop with swap 92% full. Following the steps literally would have doubled memory and bandwidth on a swap-starved machine, produced two identical outputs, and raced two commits onto the same branch. A second trap: macOS `ps -o etime` prints [[dd-]hh:]mm:ss, so "02:35" is 2.5 minutes, not 2.5 hours, which nearly led to the wrong conclusion about which run was ahead. Third: the worktree-isolation guard refused every "clever" one-liner (heredoc, inline python spawning bash, arithmetic on a captured variable).