Separate sibling track
Production readiness is not design-system completeness.
Engineering Foundation starts after the design-system six when that track is complete. It has its own six-stage progression and its own evidence. The playbook explicitly says not to add these cells to From Prototype’s What’s next tracker.
From Prototype finishes
Import → Catalog → Names → Cleanup → Rules → Wire
Engineering Foundation runs
Reproduce → Contract → Prove → Harden → Contain → Open
Six engineering stages
Why a second six
The source playbook treats these as a severity/readiness sequence rather than feature order. They shore up reproducibility, write contracts, proof, access/failure behavior, dead infrastructure, and the entry contract for new work. None of those jobs is the same as naming tokens or cleaning up design-system leftovers.
Keep the vocabulary distinct.
- Contain is not Cleanup. One concerns dead stubs/toolchain; the other concerns design-system leftovers.
- Open is not Handoff. It opens the product to new work through the established Contract.
- Engineering Foundation is not Gap Protocol. System gaps still use the design-system gap workflow.
- No Stage 7. Completion is a state of the six-stage track, not a new tracker node.