Model comparison
Compare GPT-Realtime-2.1 and Grok Voice Think Fast 2.0 using the same provider-sourced voice & realtime rubric. No mystery score and no invented benchmark ranking.
Facts checked September 4, 2026
Quick take
OpenAI's realtime speech-to-speech reasoning model for tool-using voice agents that also need text and image context.
There is no published universal latency number, and audio-token costs are hard to compare directly with minute- or character-priced competitors.
SpaceXAI's current realtime speech-to-speech model for sub-second conversational agents with tool access.
The model-specific price is higher than the generic 'starting at' Voice API headline. Use the Think Fast 2.0 row when budgeting.
Compare the published facts
Values use each provider's own published units and limits. A blank means the provider did not publish a directly comparable value in the sources reviewed.
| Voice & realtime | GPT-Realtime-2.1 | Grok Voice Think Fast 2.0 |
|---|---|---|
| Price basisToken-, character-, or minute-based price for the listed access route. | Audio $32 in · $64 out / 1M tokens | $0.08 / audio minute |
| Interaction modeSpeech-to-speech, audio-to-audio, or streamed text-to-speech behavior. | Speech-to-speech with text/image context | Realtime speech-to-speech with tools |
| Published latencyProvider-published measurement with its stated exclusions; not a Cody test. | Not published | Sub-second provider claim |
| LanguagesProvider-documented language coverage or a clear unpublished marker. | Multilingual; exact list not published here | Exact supported list not published here |
| Tools & controlNative function calling, reasoning, or speech-control features. | Function calling and configurable reasoning | Realtime tool use |
| Context or input limitDocumented token or character limit where it is meaningful. | 128K input · 32K max output | Not published |
How to choose
Start with the job you need to complete, then validate cost, access, and policy details on your exact provider route.
OpenAI says API content is not used for training by default. Default abuse-monitoring logs may be retained up to 30 days, with additional controls available to qualifying organizations.
Provider and API links
SpaceXAI says it does not train on API inputs or outputs without explicit permission. Default encrypted retention is 30 days; team-level zero data retention is available with feature tradeoffs.
Provider and API links
Frequently asked questions
GPT-Realtime-2.1: OpenAI's realtime speech-to-speech reasoning model for tool-using voice agents that also need text and image context. Grok Voice Think Fast 2.0: SpaceXAI's current realtime speech-to-speech model for sub-second conversational agents with tool access.
Consider GPT-Realtime-2.1 when your priority is Tool-using customer or employee voice agents. Consider Grok Voice Think Fast 2.0 when your priority is Realtime voice agents with tools. Test both with your own data and provider route before committing.
No. This comparison aligns provider-published facts for the Voice & realtime category. It does not claim a universal winner or combine incompatible third-party benchmark scores.
