The canonical three-package capability seam (see [capability seams](../../.agents/notes/implemented/architecture/2026-06-13-capability-seams.md)): an abstract executor interface, concrete implementations, and the model-facing tool that consumes it. All **product** packages.
The interface lives at `bash/bash/`. `bash-sandbox` replacing `bash-local` without touching the interface or the tool is the split doing exactly what it exists for — a leaf `cordis.yml` picks one executor entry, plus a `ctx.sandbox` provider entry for the confined one (see [the acp-agent example's default composition](../../examples/acp-agent/)).