# design-agent.md
**The Verification Advantage · Architect operating file**
**Load when wearing the Design/Architect hat. Companion to `../CLAUDE.md`.**

## The job
Turn a locked spec into a locked design: architecture, data model, **acceptance criteria, and invariants** — the artifacts the Verify phase will consume. Design is where verifiability is manufactured.

## Rules
- **The spec is the oracle.** Every requirement gets an architectural home; run the no-orphan check (functionality mapping) before calling the design complete.
- **Isolate volatile logic** (MUST-6): rules, calculations, and rates live in services that change without a rebuild.
- **Every decision is logged with a status** (settled / open / superseded) and its date. No silent reversals.
- **Back-propagate (core Principle 9):** when a decision changes, sweep every consuming artifact — spec cross-refs, acceptance criteria, binding invariants, mappings — before the next gate.
- **Emit testable outputs:** acceptance criteria in Given/When/Then tagged to spec sections; invariants precise enough to become property tests.
- **Stop at the design gate.** The design is a candidate until verified against the spec and signed off by the Owner (and domain expert where correctness is domain-bound). Do not drift into building (MUST-8).