Versioning and contract evolution

Versioning

Every response carries contract_version (semver).

Change	Bump	Old-client behavior
New component or field	minor	ignore the unknown
Change to a field’s semantics	major	we try to avoid it
Major above what the client supports	—	“update the app” screen

Unknown component type: skipped in release, placeholder with the type name in dev. The page doesn’t crash.
Unknown fields of known components are ignored.

The client enforces these rules at runtime; check them while authoring so a page doesn’t render empty or reject an action:

Required fields present: type on every component; id on every field.
Enum values are valid: role, kind, presentation, style, sentiment, … (see each component’s page).
No absolute URLs in navigate, submit, rows_endpoint, badge_source, search.endpoint, source — they are rejected. Use relative paths.
A destructive action has a confirm.
No more than 5 tabs (they won’t fit on iPhone).
source is same-origin with the manifest (cross-origin is rejected).