history

Minimal App definitions

id: LK-20260716-minimal-app-definition
date: 2026-07-16
sequence: 76
type: feat
compatibility: compatible
component: `labkit.ui` | `7.0.0 -> 7.1.0`
scope: App authoring
scope: Runtime V2 definition defaults

Context

Runtime V2 already normalized missing project and session buckets, but every definition still had to provide project create/validate callbacks, at least one action, and a presenter. A static App therefore needed lifecycle files and placeholder functions that owned no behavior.

Decision and rationale

Make lifecycle components proportional to product behavior. Every App still declares a stable ID, title, and semantic layout. The framework supplies empty canonical state and no-op dynamic behavior until the App opts into durable data, transient cache, actions, or presentation.

Changes

• Made Project, Actions, and Present optional in labkit.ui.runtime.define; CreateSession was already optional.
• Added a framework-owned version-1 empty project specification and empty presenter model.
• Allowed an empty action registry when no layout event or startup phase references an action.
• Added a GUI contract test that launches a definition containing only Id, Title, and Layout and verifies both canonical state roots.
• Rewrote App-development entry guidance around capability tiers instead of a fixed list of placeholder files.

User and data impact

Existing Apps behave unchanged. A new static App does not need createProject.m, createSession.m, validateProject.m, definitionActions.m, or a presenter. Those components are introduced only when the App gains corresponding behavior.

Compatibility and migration

The change is additive within UI 7. Existing complete definitions remain valid. Saved project and source schemas do not change.

Validation

The minimal-definition GUI test exercises real launch, canonical project and session creation, layout construction, empty presentation, and readiness. Definition validation and public documentation guardrails cover both minimal and full definitions.

Evidence

• App Framework introduces the minimal definition.
• Runtime and Lifecycle lists required and optional definition components.
• App Development maps files to capabilities instead of treating them as universal boilerplate.

Known limitations and follow-up

Apps that own a project schema still use explicit project specification. The next lifecycle cleanup consolidates each App's project factory, validator, and ordered migration steps behind one projectSpec.m entry point rather than scattered version-step files.