SpaceXAI, the combined xAI-SpaceX entity, released Grok Voice Think Fast 2.0 on July 29, 2026, a successor to the Grok Voice Think Fast 1.0 model it shipped earlier this year, with sizable gains on independent speech-to-speech benchmarks and a sharp cut in latency.

Benchmark gains

According to results published by Artificial Analysis, Grok Voice Think Fast 2.0's "High" reasoning variant scored 82.9% on the firm's Speech to Speech Index, debuting at #2 overall — behind only Qwen Audio 3.0 Realtime Plus (84.1%) and ahead of OpenAI's GPT-Realtime-2.1 High (79.1%) and Google's Gemini 3.1 Flash (69.5%). That's a 7.3 percentage-point jump from Think Fast 1.0's 75.7% score. On Artificial Analysis's Tau Voice benchmark, which measures agentic voice performance, the new model took the top spot at 56.5%, ahead of Qwen Audio 3.0 Realtime Plus (54.6%) and its own predecessor (52.1%).

Faster and among the first to reply

Beyond raw accuracy, SpaceXAI emphasized latency: average time-to-first-audio fell from 1.25 seconds in version 1.0 to 0.70 seconds in version 2.0, making it, per Artificial Analysis, the only model in the Speech to Speech Index's top five averaging under one second to first response. The company also said reasoning-token usage dropped by roughly 60% version-over-version, which should lower the effective cost of running the model at scale even before accounting for its published price of $0.08 per minute of audio.

Why it matters

Voice has become one of the more competitive fronts in the model race this year, as OpenAI, Google and Alibaba's Qwen team all ship realtime speech models aimed at voice agents and assistants rather than text chat. SpaceXAI is positioning Think Fast 2.0 specifically for agentic use inside its Agent Builder tooling, not just as a conversational demo, which tracks with the company's broader push — following July's Grok 4.5 release — to compete on task-completion and latency in agent workflows rather than general chatbot benchmarks alone. SpaceXAI said it will automatically migrate existing Grok users from Think Fast 1.0 to the new model on August 5, 2026.