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

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Realtime translation server 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 emitted from the OpenAI Realtime Translation WebSocket server to the client.

error

Returned when an error occurs, which could be a client problem or a server problem. Most errors are recoverable and the session will stay open, we recommend to implementors to monitor and log error messages by default.

Schema

Schema name: RealtimeServerEventError

  • error: RealtimeError

    Details of the error.

    • message: string

      A human-readable error message.

    • type: string

      The type of error (e.g., "invalid_request_error", "server_error").

    • code: optional string or null

      Error code, if any.

    • event_id: optional string or null

      The event_id of the client event that caused the error, if applicable.

    • param: optional string or null

      Parameter related to the error, if any.

  • event_id: string

    The unique ID of the server event.

  • type: "error"

    The event type, must be error.

    • "error"

Example

{
    "event_id": "event_890",
    "type": "error",
    "error": {
        "type": "invalid_request_error",
        "code": "invalid_event",
        "message": "The 'type' field is missing.",
        "param": null,
        "event_id": "event_567"
    }
}

session.created

Returned when a translation session is created. Emitted automatically when a new connection is established as the first server event. This event contains the default translation session configuration.

Schema

Schema name: RealtimeTranslationServerEventSessionCreated

  • event_id: string

    The unique ID of the server event.

  • session: RealtimeTranslationSession

    The translation session configuration.

    • id: string

      Unique identifier for the session that looks like sess_1234567890abcdef.

    • audio: 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.

          • 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 used for source transcript deltas.

      • output: optional object { language }

        • language: optional string

          Target language for translated output audio and transcript deltas.

    • expires_at: number

      Expiration timestamp for the session, in seconds since epoch.

    • model: string

      The Realtime translation model used for this session. This field is set at session creation and cannot be changed with session.update.

    • type: "translation"

      The session type. Always translation for Realtime translation sessions.

      • "translation"

  • type: "session.created"

    The event type, must be session.created.

    • "session.created"

Example

{
  "type": "session.created",
  "event_id": "event_123",
  "session": {
    "id": "sess_123",
    "type": "translation",
    "model": "gpt-realtime-translate",
    "expires_at": 1714857600,
    "audio": {
      "input": {
        "transcription": {
          "model": "gpt-realtime-whisper",
          "language": "en"
        },
        "noise_reduction": {
          "type": "near_field"
        }
      },
      "output": {
        "language": "fr"
      }
    }
  }
}

session.updated

Returned when a translation session is updated with a session.update event, unless there is an error.

Schema

Schema name: RealtimeTranslationServerEventSessionUpdated

  • event_id: string

    The unique ID of the server event.

  • session: RealtimeTranslationSession

    The translation session configuration.

    • id: string

      Unique identifier for the session that looks like sess_1234567890abcdef.

    • audio: 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.

          • 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 used for source transcript deltas.

      • output: optional object { language }

        • language: optional string

          Target language for translated output audio and transcript deltas.

    • expires_at: number

      Expiration timestamp for the session, in seconds since epoch.

    • model: string

      The Realtime translation model used for this session. This field is set at session creation and cannot be changed with session.update.

    • type: "translation"

      The session type. Always translation for Realtime translation sessions.

      • "translation"

  • type: "session.updated"

    The event type, must be session.updated.

    • "session.updated"

Example

{
  "type": "session.updated",
  "event_id": "event_124",
  "session": {
    "id": "sess_123",
    "type": "translation",
    "model": "gpt-realtime-translate",
    "expires_at": 1714857600,
    "audio": {
      "input": {
        "transcription": {
          "model": "gpt-realtime-whisper",
          "language": "en"
        },
        "noise_reduction": {
          "type": "near_field"
        }
      },
      "output": {
        "language": "es"
      }
    }
  }
}

session.closed

Returned when a realtime translation session is closed.

Schema

Schema name: RealtimeTranslationServerEventSessionClosed

  • event_id: string

    The unique ID of the server event.

  • type: "session.closed"

    The event type, must be session.closed.

    • "session.closed"

Example

{
  "event_id": "event_987",
  "type": "session.closed"
}

session.input_transcript.delta

Returned when optional source-language transcript text is available. This event is emitted only when audio.input.transcription is configured.

Transcript deltas are append-only text fragments. Clients should not insert unconditional spaces between deltas.

Schema

Schema name: RealtimeTranslationServerEventSessionInputTranscriptDelta

  • delta: string

    Append-only source-language transcript text.

  • event_id: string

    The unique ID of the server event.

  • type: "session.input_transcript.delta"

    The event type, must be session.input_transcript.delta.

    • "session.input_transcript.delta"

  • elapsed_ms: optional number or null

    Timing metadata for stream alignment, derived from the translation frame when available. It advances in 200 ms increments, but multiple transcript deltas may share the same elapsed_ms. Treat it as alignment metadata, not a unique transcript-delta identifier.

Example

{
  "event_id": "event_125",
  "type": "session.input_transcript.delta",
  "delta": " hear",
  "elapsed_ms": 1200
}

session.output_transcript.delta

Returned when translated transcript text is available.

Transcript deltas are append-only text fragments. Clients should not insert unconditional spaces between deltas.

Schema

Schema name: RealtimeTranslationServerEventSessionOutputTranscriptDelta

  • delta: string

    Append-only transcript text for the translated output audio.

  • event_id: string

    The unique ID of the server event.

  • type: "session.output_transcript.delta"

    The event type, must be session.output_transcript.delta.

    • "session.output_transcript.delta"

  • elapsed_ms: optional number or null

    Timing metadata for stream alignment, derived from the translation frame when available. It advances in 200 ms increments, but multiple transcript deltas may share the same elapsed_ms. Treat it as alignment metadata, not a unique transcript-delta identifier.

Example

{
  "event_id": "event_124",
  "type": "session.output_transcript.delta",
  "delta": " escuch",
  "elapsed_ms": 1200
}

session.output_audio.delta

Returned when translated output audio is available. The delta contains a PCM16 audio chunk whose length can vary. Clients should decode and queue the complete delta instead of assuming a fixed byte or sample count.

Schema

Schema name: RealtimeTranslationServerEventSessionOutputAudioDelta

  • delta: string

    Base64-encoded translated audio data.

  • event_id: string

    The unique ID of the server event.

  • type: "session.output_audio.delta"

    The event type, must be session.output_audio.delta.

    • "session.output_audio.delta"

  • channels: optional number

    Number of audio channels.

  • elapsed_ms: optional number or null

    Timing metadata for stream alignment, derived from the translation frame when available. Treat elapsed_ms as alignment metadata, not a unique event identifier.

  • format: optional "pcm16"

    Audio encoding for delta.

    • "pcm16"

  • sample_rate: optional number

    Sample rate of the audio delta.

Example

{
  "event_id": "event_123",
  "type": "session.output_audio.delta",
  "delta": "Base64EncodedAudioDelta",
  "sample_rate": 24000,
  "channels": 1,
  "format": "pcm16",
  "elapsed_ms": 1200
}