OpenAI

OpenAIRealtimeModel connects an agent to OpenAI’s native speech-to-speech models. Start with the realtime quickstart or the text-to-audio example.

Setup

To use OpenAI realtime models, install pydantic-ai-slim with the openai-realtime optional group, which bundles the openai package together with the realtime WebSocket transport:

Terminal

pip install "pydantic-ai-slim[openai-realtime]"

Terminal

uv add "pydantic-ai-slim[openai-realtime]"

Set OPENAI_API_KEY as described in the OpenAI model documentation. Authentication and base URL come from provider, mirroring OpenAIChatModel. The default provider='openai' reads the environment; pass an OpenAIProvider for a custom key or base URL. The realtime WebSocket opens separately, so a custom provider httpx client is not used for it. Sessions run over a server-side WebSocket by default; for browser voice, the browser can exchange media directly over WebRTC while your backend runs the agent (see Connecting a frontend).

Model names

Use the provider’s realtime model ID with OpenAIRealtimeModel, for example gpt-realtime, gpt-realtime-2.1, or gpt-realtime-2.1-mini. Model availability and aliases can change; use the official OpenAI model documentation as the canonical model list.

Settings

OpenAIRealtimeModelSettings — the realtime counterpart of model run settings — extends the shared settings with voice, noise reduction, output speed, exact turn detection, and truncation:

from pydantic_ai.realtime.openai import (
    OpenAIRealtimeModel,
    OpenAIRealtimeModelSettings,
)

settings = OpenAIRealtimeModelSettings(
    max_tokens=2_000,
    openai_voice='alloy',
    turn_detection={'sensitivity': 'high', 'silence_duration_ms': 400},
    openai_input_noise_reduction='near_field',
    openai_output_speed=1.1,
    openai_turn_detection={'type': 'semantic_vad', 'eagerness': 'high'},
    openai_truncation={'type': 'retention_ratio', 'retention_ratio': 0.8},
)
model = OpenAIRealtimeModel('gpt-realtime', settings=settings)

openai_turn_detection accepts ServerVAD or SemanticVAD and overrides shared turn_detection. openai_truncation also accepts 'auto' or 'disabled'; retention ratio preserves a stable, cacheable prefix as the session grows. openai_voice selects the provider voice. OpenAI realtime does not expose temperature through Pydantic AI.

Input transcription defaults to 'auto'; set a supported transcription model ID to pin it or None to disable it. See Input transcription.

Reasoning

The shared thinking setting (see Thinking) applies to models whose profile reports supports_thinking, including the gpt-realtime-2 family. True uses the provider default and an effort string selects a level. False omits reasoning, because OpenAI realtime does not accept a disabled effort. The GA gpt-realtime ignores the setting.

Reasoning traces are not surfaced as ThinkingParts; the API exposes effort as input only.

Browser WebRTC

For browser voice agents, OpenAI recommends WebRTC: the audio flows browser ↔ OpenAI directly, while your backend attaches a control-plane sideband to run the agent. AgentRealtime exposes two signaling helpers, both resolving and binding the agent’s session configuration (instructions, tools, voice, VAD) server-side:

answer_webrtc_offer — the secure path: relay the browser’s SDP offer to POST /v1/realtime/calls, returning the SDP answer and a WebRTCSession to attach a sideband to with agent.realtime(model).session(provider_session=…). The browser never sees a token.
create_client_secret — mint a short-lived RealtimeClientSecret (ephemeral token) for a browser that negotiates the WebRTC call itself, when you don’t relay the SDP through your backend.

See Connecting a frontend for the topology, the secure offer-relay flow, and the sideband trust model, and the realtime WebRTC example for a runnable FastAPI and browser app.

Feature support and limitations

Feature	Support	Notes
Audio format	Full feature support	Mono PCM16, 24 kHz input and output
Text output	Full feature support	Select with `output_modality='text'`
Image input	Full feature support	Images provide context for the next turn
Manual turns	Full feature support	`turn_detection=False` plus commit/create verbs
Interruption/truncation	Full feature support	`interrupt(played_ms=...)` records the heard cutoff
Input transcription	Full feature support	Dedicated model; `'auto'` by default
Native tools	Unsupported	Configure local fallbacks for web capabilities
Usage	Full feature support	Token, audio, and cache breakdowns
Reconnection	Full feature support	Pydantic AI replays completed local history; in-flight media is lost

See Audio, images, and transcripts, Turns and interruptions, Tools, and Connection lifecycle for the provider-agnostic workflows.

Gateway

To route through the Pydantic AI Gateway, use a gateway/-prefixed model string:

from pydantic_ai import Agent

agent = Agent(instructions='You are a helpful voice assistant.')
realtime = agent.realtime('gateway/openai:gpt-realtime')

Credentials come from gateway_provider. OpenAI-compatible endpoints that expose the realtime protocol can also be supplied through an OpenAIProvider. See Gateway trace propagation.

Provider-specific quirks

The provider connection has no resumable server handle. Automatic reconnect restores completed history by replaying local messages into a new session.