sandboxing is indeed an advantage (can be an important one!), but

1. bash can also express concurrency easily, with sync and async (using standard & syntax) support for each command, and standard cancellation (kill, though crude). 2. "way fewer instructions": It requires no instruction for agents to use bash either, except for merely listing the custom commands (view_image, apply_patch, etc.). Also, bash has standard progressive disclosure mechanism (--help) that models will automatically use with no instruction.