POST /api/v1/hosting/apps/{app_id}/deploys

Deploy a pre-built image. environment accepts a slug or public ID, all (the default), or existing. existing selects this service's placements in active environments with positive replica counts and enabled regions; it preserves their replica counts unless desired_instances overrides them and never creates a placement or restarts a drained placement. No eligible placements returns 422. Existing Git writer placements roll out sequentially in the background. rollout_predecessor queues a deployment until the named operation has completed successfully; failure or cancellation stops its followers.