Grok Voice Think Fast 2.0 ranks first on Speech-to-Speech Index

Elon Musk’s xAI just took the top spot in voice AI. Grok Voice Think Fast 2.0 has claimed first place on the Artificial Analysis Speech-to-Speech Index, a benchmark that evaluates how well AI models handle real-time voice conversations from end to end. The model, launched on July 29, 2026, scored 79.0% on the index. More striking are the component metrics: 97% for speech reasoning and 94.7% in task success rates. What the numbers actually mean Grok Voice Think Fast 2.0 posts a time-to-first-audio of 0.70 seconds. The standout number might be the agentic performance score of 56.5%. Agentic performance measures how well a voice model can handle multi-step tasks during a conversation, things like booking a reservation while answering follow-up questions about availability. The model also uses roughly 60% fewer reasoning tokens than its predecessor. On the pricing front, xAI is charging $0.08 per minute of audio. For context, that puts a 10-minute customer service call at $0.80 in AI costs. From 1.0 to 2.0 in under three months Think Fast 1.0 launched approximately in April 2026. Its successor arrived less than three months later. The 2.0 version supports over 25 languages and has impr...