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resources/realtime/translation-client-events.md 2026-09-10 18:01 UTC to 2026-09-11 20:00 UTC

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Realtime translation client events

For the complete documentation index, see llms.txt. Markdown versions of documentation pages are available by appending .md to the page URL.

These are events that the OpenAI Realtime Translation WebSocket server will accept from the client.

session.update

Send this event to update the translation session configuration. Translation sessions support updates to audio.output.language, audio.input.transcription, and audio.input.noise_reduction.

Schema

Schema name: RealtimeTranslationClientEventSessionUpdate

  • session: RealtimeTranslationSessionUpdateRequest

    Translation session fields to update. The session type and model are set at creation and cannot be changed with session.update.

    • audio: optional object { input, output }

      Configuration for translation input and output audio.

      • input: optional object { noise_reduction, transcription }

        • noise_reduction: optional object { type } or null

          Optional input noise reduction. Set to null to disable it.

          • type: NoiseReductionType

            Type of noise reduction. near_field is for close-talking microphones such as headphones, far_field is for far-field microphones such as laptop or conference room microphones.

            • "near_field"

            • "far_field"

        • transcription: optional object { model } or null

          Optional source-language transcription. When configured, the server emits session.input_transcript.delta events. Translation itself still runs from the input audio stream.

          • model: string

            The transcription model to use for source transcript deltas.

      • output: optional object { language }

        • language: optional string

          Target language for translated output audio and transcript deltas.

  • type: "session.update"

    The event type, must be session.update.

    • "session.update"

  • event_id: optional string

    Optional client-generated ID used to identify this event.

Example

{
  "type": "session.update",
  "session": {
    "audio": {
      "input": {
        "transcription": {
          "model": "gpt-realtime-whisper"
        },
        "noise_reduction": null
      },
      "output": {
        "language": "es"
      }
    }
  }
}

session.input_audio_buffer.append

Send this event to append audio bytes to the translation session input audio buffer.

WebSocket translation sessions accept base64-encoded 24 kHz PCM16 mono little-endian raw audio bytes. Unsupported websocket audio formats return a validation error because lower-quality audio materially degrades translation quality.

Translation consumes 200 ms engine frames. For best realtime behavior, append audio in 200 ms chunks. If a chunk is shorter, the server buffers it until it has enough audio for one frame. If a chunk is longer, the server splits it into 200 ms frames and enqueues them back-to-back.

Keep appending silence while the session is active. If a client stops sending audio and later resumes, model time treats the resumed audio as contiguous with the previous audio rather than as a real-world pause.

Schema

Schema name: RealtimeTranslationClientEventInputAudioBufferAppend

  • audio: string

    Base64-encoded 24 kHz PCM16 mono audio bytes.

  • type: "session.input_audio_buffer.append"

    The event type, must be session.input_audio_buffer.append.

    • "session.input_audio_buffer.append"

  • event_id: optional string

    Optional client-generated ID used to identify this event.

Example

{
  "event_id": "event_456",
  "type": "session.input_audio_buffer.append",
  "audio": "Base64EncodedAudioData"
}

session.close

Gracefully close the realtime translation session. The server flushes pending input audio and emits any remaining translated output before closing the session.

Schema

Schema name: RealtimeTranslationClientEventSessionClose

  • type: "session.close"

    The event type, must be session.close.

    • "session.close"

  • event_id: optional string

    Optional client-generated ID used to identify this event.

Example

{
  "event_id": "event_789",
  "type": "session.close"
}