We forward logs from one environment (19 services) with Locomotive, which uses the environmentLogs GraphQL subscription. Sentry consistently received fewer lines than Railway has. We instrumented the subscriber to account for every line it receives, ran it for 70 minutes, and compared the result with railway logs --since … --until … --json for the same services and window.

Subscription used

subscription streamEnvironmentLogs($environmentId: String!, $filter: String, $beforeLimit: Int!, $beforeDate: String) {
  environmentLogs(environmentId: $environmentId, filter: $filter, beforeDate: $beforeDate, beforeLimit: $beforeLimit) { … }
}

filter = the service-id filter for the 19 services, beforeLimit: 5000, and beforeDate = the last timestamp seen. That's the resume point after a reconnect.

Result (2026-11-11, 16:39–17:49 UTC)

• The logs query returned 5,687 lines. The subscription delivered 5,617. 70 lines (1.2%) were never delivered.
• Every line the subscription delivered was accounted for: summed batch sizes = lines forwarded + duplicates. The subscriber dropped nothing.
• Reconnects weren't the cause. The server closed the stream with 4500 deadline_exceeded about every 10 minutes, plus a few EOFs, and each resubscribe resumed exactly at beforeDate.
• The missing lines arrive in the middle of a healthy stream. Batches covering their timestamps arrived, but those lines weren't in them. They're partial gaps inside bursts. For example, 12 of 38 lines from one service within one second are missing, and all 10 lines from another service at one moment are missing.
• We saw the same rate over a longer earlier window: ~1.6% over 15 hours on one service.

Expected: the subscription delivers the same lines the logs query returns for the same filter and window.

Questions:

1. Is the subscription expected to be lossy, e.g. sampled or best-effort under bursts?
2. If so, is there a reliable way to tail logs, such as a per-deployment subscription or a paginated query with a cursor?

We can provide the environment ID, the exact missing timestamps and the probe output privately.