Realtime sessions close after 3 minutes with no audio or ping/pong, signaled by an in-band error and code 1008. Send pings while your agent thinks, and keep custom dictionaries under 20,000 items.

Context: Official docs (Speechmatics realtime limits): a realtime session ends after 48 hours, after 1 hour with no audio, or after just 3 minutes with no audio and no ping or pong. Closure arrives as an in-band error plus close code 1008, so handle it as a normal event. If your agent pauses to think, send pings to hold the session. Separately, more than 20,000 custom dictionary items triggers a protocol error with code 1003.