What
Claude Code now tracks how many usage/telemetry events are still waiting to be sent when a session shuts down. A new internal check reports the number of unsent client events, the number of unsent internal events, how long the oldest queued event has been waiting, and whether sending is currently backing off. This information is attached to telemetry as unsent_client_events_at_close, unsent_internal_events_at_close, and hold_preflush_inflight_age_ms at the moments a connection closes or no listener is holding events.
Why
This gives visibility into whether Claude Code is losing or delaying telemetry data at shutdown, which helps diagnose gaps in usage reporting rather than leaving them silent.