The canonical three-package capability seam (see [capability seams](../../docs/rfc/implemented/architecture/2026-06-13-capability-seams.md)): an abstract executor interface, a concrete local implementation, and the model-facing tool that consumes it. All **product** packages.
The interface lives at `bash/bash/`. A sandboxed executor would replace `bash-local` without touching the interface or the tool — the split is what makes that possible. Background runs are generic tasks, not bash-private state: `tool-bash` registers a started `BashProcess` handle with the [`ctx.tasks` registry](../tasks/README.md), whose `task_*` tools collect and stop it.