Vendored, pinned to a commit (HIMMEL-5498). Source: mattpocock/skills,
commit 49dd158d1076134a641b33efb035946536778336, path
skills/engineering/domain-modeling/ (SKILL.md, GLOSSARY-FORMAT.md),
fetched 2026-10-16. License: MIT, (c) 2026 Matt Pocock (LICENSE beside this file).
Deviations from upstream: (1) output retargeted from a root GLOSSARY.md to
himmel's docs/glossary.md, in its own table format (one definition per term,
an alias points at the canonical term); (2) the multi-context GLOSSARY-MAP.md
structure and the ADR guidance are dropped (ADR-FORMAT.md is not vendored,
himmel keeps decision records in the state repo); (3) frontmatter description
trimmed to match; (4) this header. Re-sync by diffing against the pinned path.

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 down the moment terms crystallise. (Merely reading docs/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

himmel has a single context: docs/glossary.md. It is the one definition site for the fleet and harness vocabulary; everything else links to it instead of restating a definition. Create no other glossary file.

During the session

Challenge against the glossary

When the user uses a term that conflicts with the existing language in docs/glossary.md, call it out immediately. "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 docs/glossary.md inline

When a term is resolved, update docs/glossary.md right there. Don't batch these up: capture them as they happen. Use the format in GLOSSARY-FORMAT.md. Search the glossary for the term and its aliases first: one definition per term, never a second row.

docs/glossary.md should be totally devoid of implementation details. Do not treat it as a spec, a scratch pad, or a repository for implementation decisions. It is a glossary and nothing else.