3 OTel span attributes I tag on every voice-pipeline span

Voice pipelines have 4 stages that need separate latency stories: ASR (speech to text), LLM (the response prompt), TTS (text to speech), and client (jitter on the receiving end). When we wired OTel across all 4, the spans without consistent attributes were useless for queries. 3 attributes ended up on every span and earn their keep. audio.stage. Enum: asr, llm, tts, client. The single most-queried attribute. The Grafana query for p95 latency by stage is one filter. Without this, you are scrolling raw traces. audio.session_id: The full conversation.