Domain Modeling

Domain Modeling

Actively build and sharpen the project's domain model while designing. Challenge terms, invent edge-case scenarios, and write the glossary and decisions down the moment they crystallise.

Reading CONTEXT.md for vocabulary is not this skill — that is a one-line habit any skill can do. This skill is for changing the model, not just consuming it.

Contract

Inputs:

• A term, relationship, or decision under discussion
• Existing CONTEXT.md / CONTEXT-MAP.md and docs/adr/ when present
• docs/agents/domain.md when setup-agent-routing has already configured layout

Outputs:

• Updated glossary entries in CONTEXT.md
• Optional ADR when the three-gate filter passes

Creates/Modifies:

• CONTEXT.md (or a per-context CONTEXT.md listed in CONTEXT-MAP.md)
• docs/adr/NNNN-slug.md when an ADR is warranted
• Directories created lazily — only when there is something to write

External Side Effects:

• Local file writes only. No tracker writes.

Confirmation Required:

• Before creating the first CONTEXT.md in a repo that had none
• Before writing an ADR

Delegates To:

• None. grilling and interview invoke this skill when a term crystallises.

File structure

Most repos have a single context:

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

If a CONTEXT-MAP.md exists at the root, the repo has multiple contexts. The map points to where each one lives. Prefer the layout already recorded in docs/agents/domain.md when that file exists.

Create files lazily — only when there is something to write. If no CONTEXT.md exists, create one when the first term is resolved. If no docs/adr/ exists, create it when the first ADR is needed.

During the session

Challenge against the glossary

When the user uses a term that conflicts with the existing language in CONTEXT.md, call it out immediately. "The glossary defines 'cancellation' as X, but this sounds like Y — which is it?"

Sharpen fuzzy language

When the user uses vague or overloaded terms, propose a precise canonical term. "'Account' — Customer or 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 precise boundaries between concepts.

Cross-reference with code

When the user states how something works, check whether the code agrees. If they contradict, surface it: "The code cancels entire Orders, but you just said partial cancellation is possible — which is right?"

Update CONTEXT.md inline

When a term is resolved, update CONTEXT.md right there. Do not batch these up — capture them as they happen. Use the format in references/CONTEXT-FORMAT.md.

CONTEXT.md is a glossary and nothing else. Keep implementation details, scratch notes, and specs out of it.

Offer ADRs sparingly

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

1. Hard to reverse — the cost of changing later is meaningful
2. Surprising without context — a future reader will wonder why it was done this way
3. The result of a real trade-off — genuine alternatives, picked for specific reasons

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