Equilio Explain

Use Explain as an independently invokable Supporting Skill for human comprehension, whether the code came from a human, AI, or the Core Skills. Ask: What should a maintainer understand differently because this changed?

Establish the model change

When an associated work artifact is available, read its latest state and apply the work-artifact contract, reusing current guidance already in context. Keep the owning issue current when explanation reveals missing durable understanding.

Read the supplied branch, PR, work artifact, implementation, and relevant repository context. Establish a comparison baseline from available history; inspect actual code, callers, and tests rather than inferring behavior from the diff alone. With partial evidence, name what could not be checked. For unfamiliar code without a before-state, teach the current model and its comparison limits instead of inventing an old model.

Use an existing System Model as optional shared context, relating changed responsibilities to affected interactions and governing principles. Identify stale entries for reconciliation without assuming a model exists or creating one for the explanation.

Apply the Development Principles proportionately. Distinguish verified behavior, inferred intent, and documented reasoning; do not manufacture rationale or validation.

Look selectively for concepts and relationships that change future reasoning: responsibilities moving across boundaries, new invariants, changed data or user flows, removed assumptions, durable decisions, meaningful coupling, or extension points. Explain what must now be understood and why it matters. These are inspection lenses, not required output sections. Omit mechanical refactors, file or function inventories, routine test additions, and obvious code narration unless they alter the system model.

Teach the updated model

Lead with the conceptual shift, then explain relationships, cause and effect, and responsibility boundaries. Include supported reasoning, constraints a maintainer must preserve, and a few precise references when useful. Use technical terms only with enough context to make them understandable. Match depth to the change and omit empty sections; say briefly when no material mental-model change exists.