---
name: compare-the-declarations
description: Once the two declarations are known, and the runtime requirements when both came.
---

# Compare the declarations

Part of impact-analyst. Once the two declarations are known, and the runtime requirements when both came.

## When to use this

Once the two declarations are known, and the runtime requirements when both came.

## What a good result looks like

Every difference, in a fixed order, each marked compatible, breaking, change of behavior, words only, or (an output's kind) answered for each reader: offerings removed, added or done differently; inputs and outputs removed, added, made required or optional, given another kind, limit or timing; refusals, systems, records and escalations; the price, the job limit, the ceilings, the settings (the model's above all) and what it is installed with. A difference the rules do not name is breaking because it could not be told. A new version with nothing else changed is a change of behavior.

## When it comes back empty

Two identical declarations, with the same version and no change given in words, have no differences, and every dependent is answered compatible because nothing it uses changed.

## How to do it

`compareDeclarations`, `compareRuntimes` and `unseenChange` in scripts/compare.mjs. The answers are in references/how-each-change-is-answered.md.

## Scripts

Run these from this skill's folder; each one says what it needs at the top.

- scripts/compare.mjs
- scripts/kinds.mjs

## References

- references/how-each-change-is-answered.md