Nw Ddd Architect

DDD Architect — design-time mandates

The nw-ddd-architect agent and nw-ddd-architect-reviewer both instruct loading this file by name (~/.claude/skills/nw-ddd-architect/SKILL.md) at DESIGN entry, before any DESIGN row is authored. It carries the design-time mandates that must be in context BEFORE the domain model is authored. Strategic/tactical/event-modeling knowledge lives in the sibling skills (nw-ddd-strategic, nw-ddd-tactical, nw-ddd-event-modeling, nw-ddd-eventsourcing); this core holds the cross-cutting enforcement mandates the agent spec references.

Fixture-Fanout Enumeration Mandate

F-DDD-ARCHITECT-SKILL-FIXTURE-FANOUT-GATE (M51 R-M51-B closure, 2026-05-25) — a mechanically-enforced design-time gate.

When it fires. A DESIGN row that migrates a shared substrate per-caller — an adapter / ledger / plugin whose construction or seed surface is shared between production and test composition. Trigger by either signal:

• the row's Decision = PER_CALLER_MIGRATION, OR
• the substrate type matches the pattern [A-Z]\w+Ledger | [A-Z]\w+Adapter | [A-Z]\w+Plugin AND is constructed in BOTH src/ and tests/ (for example, a shared persistence adapter).

What the row MUST enumerate (with grep evidence). Three cells, all mandatory:

• (a) Production Callers — every production callsite, file:line for each.
• (b) Fixture Sites — every test-composition / helper / conftest entry that CONSTRUCTS or SEEDS the same substrate. This is the cell that is silently omitted — and its omission is the M50 defect class: the substrate ships GREEN against its own ATs and breaks sibling consumers at the crafter's empirical run.
• (c) Atomic Bundle Scope — the row explicitly states production sites {N} + fixture sites {M} ship together in slice {S}. Production sites + fixture sites that read/write the SAME substrate path MUST ship in ONE slice; splitting them across slices is the violation.

Why (empirical anchors). friction #42 F-M40-SLICE-02C-N1-PRODUCTION-FIXTURE-NOT-ATOMIC (M50 crafter — 3 production callsites declared, 5+ fixture sites silently excluded → 12 sibling regressions, REVERTED). A 5-instance META-pattern (#33 M34 + #38 M42 + #40 M45 + #42 M50 + #43 M49) all surfaced ONLY at the crafter's empirical execution despite architect residuality passes — the Streetlight bias: M50 declared 7 sites where empirical run found 18 (2.5× undercount). The eye does not see the fixture fanout; the mechanical grep does.

Mechanical procedure + rejection rule (self-execution; the reviewer runs the same).

1. grep the DESIGN section for rows matching the substrate-migration trigger above.
2. For each, extract the Production Callers: count + Fixture Sites: count + Atomic Bundle: cell.
3. Run INDEPENDENT grep counts against the real tree:
   • production: grep -rn '<substrate_pattern>' src/des/ | wc -l
   • fixtures: grep -rln '<substrate_pattern>' tests/ | xargs grep -c '<substrate_pattern>' | awk -F: '{s+=$2} END {print s}'
4. REJECT (critical BLOCKER) on ANY of: a missing cell (Production Callers / Fixture Sites / Atomic Bundle Scope), a declared-vs-empirical count mismatch (off-by-N% for any N > 0), or an Atomic Bundle that splits production from fixtures across slices. A row that lists production callers but omits the fixture-sites enumeration is the silent-fixture-fanout defect — block it.

Defense-in-depth. Complements F-D-09 (Forbidden-Import-Roots) + the runtime cascade-detector arch test (registry-vs-frozenset symmetry). The architect declares the enumeration (principle 9); the reviewer re-runs the greps and blocks on mismatch (principle 6); neither trusts the other's count — the grep is the arbiter.