The bash tool finished only when every holder of its output let go, so `python3 -m http.server … &` left a background subshell holding the pipe and the turn waited forever (a jumping-game session sat for minutes). It now returns when the shell exits, gives the output a moment to drain, and leaves background processes running. Tests cover both hang shapes. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>