Core concepts
Delivery states
Provider acceptance, device presentation, and user engagement are different observations.The evidence chain
| State | What it proves | What it does not prove |
|---|---|---|
| Queued | A durable job exists | A provider request occurred |
| Provider accepted | APNs or FCM accepted the request | The device displayed it |
| Presented | The SDK observed presentation where supported | The user read it |
| Opened | The user opened through the notification | The destination action succeeded |
Failures
Dead-token responses deactivate only the proven invalid token. Configuration failures remain permanent without damaging tokens. Timeouts, rate limits, and provider unavailability remain retryable.