Domain Modeling

Actively build and sharpen the project's domain model as you design. This is the active discipline: challenging terms, inventing edge-case scenarios, and writing the glossary and decisions down the moment they crystallise. (Merely reading GLOSSARY.md for vocabulary is not this skill: that's a one-line habit any skill can do. This skill is for when you're changing the model, not just consuming it.)

File structure

Most repos have a single context:

/
├── GLOSSARY.md
├── docs/
│   └── adr/
│       ├── 0001-event-sourced-orders.md
│       └── 0002-postgres-for-write-model.md
└── src/

If GLOSSARY-MAP.md or CONTEXT-MAP.md exists at the root, read its pointers to find the existing contexts:

/
├── GLOSSARY-MAP.md
├── docs/
│   └── adr/                          ← system-wide decisions
├── src/
│   ├── ordering/
│   │   ├── GLOSSARY.md
│   │   └── docs/adr/                 ← context-specific decisions
│   └── billing/
│       ├── GLOSSARY.md
│       └── docs/adr/

Use existing GLOSSARY.md or CONTEXT.md files and their map pointers; do not migrate or duplicate them. When authorized to write and no glossary exists, create GLOSSARY.md for the first resolved term. Create docs/adr/ only for the first accepted ADR. Otherwise render the exact proposed change in chat.

During the session

Challenge against the glossary

When a term conflicts with the existing GLOSSARY.md or CONTEXT.md language, surface the conflict. "Your glossary defines 'cancellation' as X, but you seem to mean Y. Which is it?"

Sharpen fuzzy language

When the user uses vague or overloaded terms, propose a precise canonical term. "You're saying 'account': do you mean the Customer or the User? Those are different things."

Discuss concrete scenarios

When domain relationships are being discussed, stress-test them with specific scenarios. Invent scenarios that probe edge cases and force the user to be precise about the boundaries between concepts.

Cross-reference with code

When the user states how something works, check whether the code agrees. If you find a contradiction, surface it: "Your code cancels entire Orders, but you just said partial cancellation is possible. Which is right?"

Update the existing glossary inline

When a term is resolved and writing is authorized, update the existing glossary, or GLOSSARY.md for a new one. Otherwise render the exact proposed update in chat. Don't batch these up: capture them as they happen. Use the format in GLOSSARY-FORMAT.md.

Keep the existing GLOSSARY.md or CONTEXT.md focused on domain terms, without implementation details or decisions. Use ADRs for durable decisions.

Offer ADRs sparingly

Only offer to create an ADR when all three are true:

1. Hard to reverse: the cost of changing your mind later is meaningful
2. Surprising without context: a future reader will wonder "why did they do it this way?"
3. The result of a real trade-off: there were genuine alternatives and you picked one for specific reasons

If any of the three is missing, skip the ADR. Use the format in ADR-FORMAT.md.