> ## Documentation Index > Fetch the complete documentation index at: https://voice.ai/llms.txt > Use this file to discover all available pages before exploring further. # Single-Context WebSocket > Single generation per connection. Text is buffered until flush, audio streams back, then server closes connection (code 1000). For multiple generations, use `/multi-stream`. **Authentication:** `Authorization: Bearer YOUR_API_KEY` ## AsyncAPI ````yaml docs/asyncapi.json /api/v1/tts/stream id: /api/v1/tts/stream title: Single-Context WebSocket description: >- Single generation per connection. Text is buffered until flush, audio streams back, then server closes connection (code 1000). For multiple generations, use `/multi-stream`. **Authentication:** `Authorization: Bearer YOUR_API_KEY` servers: - id: production protocol: wss host: dev.voice.ai bindings: [] variables: [] address: /api/v1/tts/stream parameters: [] bindings: [] operations: - &ref_1 id: sendInitSingle title: Send Initialization Message description: >- Send the first message to initialize the session with voice, model, and language settings. Include text and flush=true for immediate generation. type: receive messages: - &ref_4 id: initMessage contentType: application/json payload: - name: Initialization Message description: First message to set up the session (sets voice, model, language) type: object properties: - name: voice_id type: string description: Voice ID to use. Omit to use the default built-in voice. required: false - name: text type: string description: Text to synthesize (buffered until flush) required: true - name: language type: string description: >- Language code (ISO 639-1 format). Supported: en, ca, sv, es, fr, de, it, pt, pl, ru, nl. enumValues: - en - ca - sv - es - fr - de - it - pt - pl - ru - nl required: false - name: model type: string description: >- TTS model to use. If not provided, automatically selected based on language. English uses voiceai-tts-v1-latest; other languages use voiceai-tts-multilingual-v1-latest. Lite models are English-only and must be selected explicitly. enumValues: - voiceai-tts-v1-latest - voiceai-tts-v1-2026-02-10 - voiceai-tts-lite-v1-latest - voiceai-tts-lite-v1-2026-04-15 - voiceai-tts-multilingual-v1-latest - voiceai-tts-multilingual-v1-2026-02-10 required: false - name: audio_format type: string description: >- Audio output format. Basic formats (mp3, wav, pcm) use 32kHz sample rate. Format-specific options allow control over sample rate and bitrate. All PCM formats (pcm, pcm_*) use 16-bit signed little-endian mono. enumValues: - mp3 - wav - pcm - alaw_8000 - mp3_22050_32 - mp3_24000_48 - mp3_44100_32 - mp3_44100_64 - mp3_44100_96 - mp3_44100_128 - mp3_44100_192 - opus_48000_32 - opus_48000_64 - opus_48000_96 - opus_48000_128 - opus_48000_192 - pcm_8000 - pcm_16000 - pcm_22050 - pcm_24000 - pcm_32000 - pcm_44100 - pcm_48000 - ulaw_8000 - wav_16000 - wav_22050 - wav_24000 required: false - name: temperature type: number description: Sampling temperature (0.0-2.0) required: false - name: top_p type: number description: Nucleus sampling (0.0-1.0) required: false - name: dictionary_id type: string description: Optional managed pronunciation dictionary identifier. required: false - name: dictionary_version type: integer description: >- Optional managed dictionary version. Defaults to latest when omitted. required: false - name: delivery_mode type: string description: >- Delivery cadence mode: 'raw' (default) or 'paced'. Paced delivery is applied only to PCM-based outputs ('pcm', 'pcm_*', 'ulaw_8000', 'alaw_8000'); other formats fall back to raw cadence. enumValues: - raw - paced required: false - name: flush type: boolean description: Trigger audio generation from buffer required: false headers: [] jsonPayloadSchema: type: object properties: voice_id: type: string description: Voice ID to use. Omit to use the default built-in voice. x-parser-schema-id: text: type: string description: Text to synthesize (buffered until flush) x-parser-schema-id: language: type: string description: >- Language code (ISO 639-1 format). Supported: en, ca, sv, es, fr, de, it, pt, pl, ru, nl. default: en enum: - en - ca - sv - es - fr - de - it - pt - pl - ru - nl x-parser-schema-id: model: type: string description: >- TTS model to use. If not provided, automatically selected based on language. English uses voiceai-tts-v1-latest; other languages use voiceai-tts-multilingual-v1-latest. Lite models are English-only and must be selected explicitly. enum: - voiceai-tts-v1-latest - voiceai-tts-v1-2026-02-10 - voiceai-tts-lite-v1-latest - voiceai-tts-lite-v1-2026-04-15 - voiceai-tts-multilingual-v1-latest - voiceai-tts-multilingual-v1-2026-02-10 x-parser-schema-id: audio_format: type: string description: >- Audio output format. Basic formats (mp3, wav, pcm) use 32kHz sample rate. Format-specific options allow control over sample rate and bitrate. All PCM formats (pcm, pcm_*) use 16-bit signed little-endian mono. enum: - mp3 - wav - pcm - alaw_8000 - mp3_22050_32 - mp3_24000_48 - mp3_44100_32 - mp3_44100_64 - mp3_44100_96 - mp3_44100_128 - mp3_44100_192 - opus_48000_32 - opus_48000_64 - opus_48000_96 - opus_48000_128 - opus_48000_192 - pcm_8000 - pcm_16000 - pcm_22050 - pcm_24000 - pcm_32000 - pcm_44100 - pcm_48000 - ulaw_8000 - wav_16000 - wav_22050 - wav_24000 default: mp3 x-enum-descriptions: mp3: MP3 format (32kHz) wav: WAV format (32kHz) pcm: PCM format (32kHz) alaw_8000: A-law telephony format (8kHz) mp3_22050_32: MP3 at 22.05kHz, 32kbps mp3_24000_48: MP3 at 24kHz, 48kbps mp3_44100_32: MP3 at 44.1kHz, 32kbps mp3_44100_64: MP3 at 44.1kHz, 64kbps mp3_44100_96: MP3 at 44.1kHz, 96kbps mp3_44100_128: MP3 at 44.1kHz, 128kbps mp3_44100_192: MP3 at 44.1kHz, 192kbps opus_48000_32: Opus at 48kHz, 32kbps opus_48000_64: Opus at 48kHz, 64kbps opus_48000_96: Opus at 48kHz, 96kbps opus_48000_128: Opus at 48kHz, 128kbps opus_48000_192: Opus at 48kHz, 192kbps pcm_8000: PCM at 8kHz pcm_16000: PCM at 16kHz pcm_22050: PCM at 22.05kHz pcm_24000: PCM at 24kHz pcm_32000: PCM at 32kHz pcm_44100: PCM at 44.1kHz pcm_48000: PCM at 48kHz ulaw_8000: μ-law telephony format (8kHz) wav_16000: WAV at 16kHz wav_22050: WAV at 22.05kHz wav_24000: WAV at 24kHz x-parser-schema-id: temperature: type: number description: Sampling temperature (0.0-2.0) default: 1 minimum: 0 maximum: 2 x-parser-schema-id: top_p: type: number description: Nucleus sampling (0.0-1.0) default: 0.8 minimum: 0 maximum: 1 x-parser-schema-id: dictionary_id: type: string description: Optional managed pronunciation dictionary identifier. x-parser-schema-id: dictionary_version: type: integer description: >- Optional managed dictionary version. Defaults to latest when omitted. minimum: 1 x-parser-schema-id: delivery_mode: type: string description: >- Delivery cadence mode: 'raw' (default) or 'paced'. Paced delivery is applied only to PCM-based outputs ('pcm', 'pcm_*', 'ulaw_8000', 'alaw_8000'); other formats fall back to raw cadence. enum: - raw - paced default: raw x-parser-schema-id: flush: type: boolean description: Trigger audio generation from buffer default: false x-parser-schema-id: required: - text x-parser-schema-id: title: Initialization Message description: First message to set up the session (sets voice, model, language) example: |- { "voice_id": "", "text": "", "language": "", "model": "", "audio_format": "", "temperature": 123, "top_p": 123, "dictionary_id": "", "dictionary_version": 123, "delivery_mode": "", "flush": true } bindings: [] extensions: - id: x-parser-unique-object-id value: initMessage bindings: [] extensions: &ref_0 - id: x-parser-unique-object-id value: /api/v1/tts/stream - &ref_2 id: sendTextSingle title: Buffer Additional Text description: >- Buffer additional text before flush. Once flush=true is sent, audio generates and connection closes. No further messages possible after flush. type: receive messages: - &ref_5 id: textMessage contentType: application/json payload: - name: Text Buffering Message description: >- Buffer additional text before flush (text-only, no params). After flush, connection closes. type: object properties: - name: text type: string description: Additional text to buffer (appended to existing buffer) required: true - name: flush type: boolean description: >- Trigger audio generation. Once flushed, audio streams and connection closes. required: false headers: [] jsonPayloadSchema: type: object properties: text: type: string description: Additional text to buffer (appended to existing buffer) x-parser-schema-id: flush: type: boolean description: >- Trigger audio generation. Once flushed, audio streams and connection closes. default: false x-parser-schema-id: required: - text x-parser-schema-id: title: Text Buffering Message description: >- Buffer additional text before flush (text-only, no params). After flush, connection closes. example: |- { "text": "", "flush": true } bindings: [] extensions: - id: x-parser-unique-object-id value: textMessage bindings: [] extensions: *ref_0 - &ref_3 id: receiveAudioSingle title: Receive Audio Chunks description: >- Receive base64-encoded audio chunks. After is_last, server closes connection. Errors close connection with close code (no JSON error message). type: send messages: - &ref_6 id: audioChunk contentType: application/json payload: - name: Audio Chunk Response description: Base64-encoded audio chunk (streamed immediately) type: object properties: - name: audio type: string description: Base64-encoded audio chunk (32kHz sample rate) required: true headers: [] jsonPayloadSchema: type: object properties: audio: type: string description: Base64-encoded audio chunk (32kHz sample rate) format: byte x-parser-schema-id: required: - audio x-parser-schema-id: title: Audio Chunk Response description: Base64-encoded audio chunk (streamed immediately) example: |- { "audio": "" } bindings: [] extensions: - id: x-parser-unique-object-id value: audioChunk - &ref_7 id: completionMessage contentType: application/json payload: - name: Completion Signal description: >- Sent after all audio chunks. Server then closes connection (code 1000). type: object properties: - name: is_last type: boolean description: >- Indicates all audio chunks have been sent. Connection will close immediately after. required: true headers: [] jsonPayloadSchema: type: object properties: is_last: type: boolean description: >- Indicates all audio chunks have been sent. Connection will close immediately after. const: true x-parser-schema-id: required: - is_last x-parser-schema-id: title: Completion Signal description: >- Sent after all audio chunks. Server then closes connection (code 1000). example: |- { "is_last": true } bindings: [] extensions: - id: x-parser-unique-object-id value: completionMessage - &ref_8 id: errorMessage contentType: application/json payload: - name: Error Close Event description: Close event emitted on protocol/validation errors type: object properties: - name: error type: string description: Close reason text from server required: true headers: [] jsonPayloadSchema: type: object properties: error: type: string description: Close reason text from server x-parser-schema-id: required: - error x-parser-schema-id: title: Error Close Event description: Close event emitted on protocol/validation errors example: |- { "error": "" } bindings: [] extensions: - id: x-parser-unique-object-id value: errorMessage bindings: [] extensions: *ref_0 sendOperations: - *ref_1 - *ref_2 receiveOperations: - *ref_3 sendMessages: - *ref_4 - *ref_5 receiveMessages: - *ref_6 - *ref_7 - *ref_8 extensions: - id: x-parser-unique-object-id value: /api/v1/tts/stream securitySchemes: - id: bearerAuth name: bearerAuth type: http description: >- API key (vk_*). Include in Authorization header: 'Bearer YOUR_API_KEY'. Required for all WebSocket connections. See the [Authentication guide](/docs/guides/authentication) for details. scheme: bearer extensions: [] ````