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Overview

Stream text deltas in (for example, LLM tokens), get audio chunks back live.
The WSS endpoint is rolling out. If the upgrade returns 500, the route is not yet enabled for your account. The HTTP fallback is Stream Speech.

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Authentication

In order of precedence:
  • ?token=<JWT> query parameter (recommended for browsers). Mint via Mint Stream Input Token.
  • Authorization: Bearer <api_key> header (server-side).
  • Sec-WebSocket-Protocol: bland.api_key.<key> subprotocol.
  • ?api_key=<key> query (deprecated, logged).

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Protocol

All messages are JSON.

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Client → Server messages

init   { type, voice_id, output_format?, consistency?,
         expressiveness?, auto_flush?, auto_flush_char_threshold? }
speak  { type, text, flush? }
flush  { type }
close  { type }

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Server → Client messages

ready  { type, session_id, output_format }
audio  { type, data (base64), is_final }
done   { type, session_id, characters_billed, cost_usd, latency_ms }
error  { type, code, message }

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Limits

Buffer cap:    4000 chars (per accumulation before flush)
Speak rate:    500 msgs / 10s window
Idle timeout:  60s (no client messages → close)
Billing:       once at "done", partial disconnect not charged
Docs for agents: llms.txt