spec/*.feature is the product behaviour source of truth. The files are executable specifications in structure, but AK does not run them through Cucumber. Ordinary Vitest and Playwright tests prove each scenario at the cheapest useful layer.

Each scenario has exactly one stable id and one proof layer:

@tasks/claim @api
Scenario: The assigned Agent claims a Task

The proving test includes the same id in its name:

it("[spec: tasks/claim] claims the assigned Task", async () => {})

Proof layers:

Tag	Home	Purpose
`@domain`	`server/domain/*/.test.ts`	Pure state and authority rules
`@usecase`	`server/usecases/*/.test.ts`	Application orchestration with port fakes
`@api`	`server/http/*/.test.ts` or `tests/integration/http/*/.test.ts`	Assembled HTTP contract and real D1 boundaries
`@web`	`src/*/.test.tsx`	Component behaviour with a mocked API boundary
`@e2e`	`tests/*/.spec.ts`	A small number of real browser journeys

Scenario ids never change. If product behaviour is replaced, remove the old scenario and add a new id. pnpm lint:spec checks ids, tags, duplicates, and test breadcrumbs. Keep this directory pure: only this README and .feature files belong here.