The RunSpec is the one contract the build, jury, integrators, QA, and the receipt share. Freeze it before implementation and a changed goal becomes visible instead of convenient.
The contract has two layers. An immutable core carries the objective, scope, criteria, risk, and proof meaning shared by all pillars. A typed Build or Review projection adds the fields needed for that run without forking the protocol.
Stable criteria create traceability
Each Definition of Good item receives a stable ID, hardness, proof method, and expected evidence. That ID follows the promise through the gate, both jury passes, integration, QA, and the final receipt.
If a criterion is wrong, the run routes back through an explicit revision. An implementation agent cannot silently replace it with an easier target.
Fingerprints make drift observable
Fusion fingerprints both the shared contract and its full projection. Role packets and evidence records bind to those values. A stale completion can remain useful evidence, but it cannot advance the current run epoch.
This is change control for agentic work: not bureaucracy, but a way to know which ask a result actually answered.
Source ledger
- Fusion planning model, section 8.
- Fusion MVP PRD, FR-3 and FR-3a.
- Fusion run lifecycle, accepted app convergence notes.